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Feifan Wang, Yan Zhang, Xuejian Zhou, Xianwu Chen, Jiayong Xiang, Mengjing Fan, Yanlan Yu, Yueshu Cai, Hongshen Wu, Shihan Huang, et al.
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.704683

Abstract:
Circular RNA (circRNA) is a newly discovered endogenous non-coding RNA (ncRNA), which is characterized with a closed circular structure. A growing body of evidence has verified the vital roles of circRNAs in human cancer. In this research, we selected circPPP1CB as a study object by circRNA sequencing and quantitative real-time PCR (qRT-PCR) validation in human bladder cancer (BC). CircPPP1CB is downregulated in BC and is negatively correlated with clinical stages and histological grades. Functionally, circPPP1CB modulated cell growth, metastasis, and epithelial-to-mesenchymal transition (EMT) process in vitro and in vivo. Mechanically, we performed various experiments to verify the circPPP1CB/miR-1307-3p/SMG1 regulatory axis. Taken together, our results demonstrated that circPPP1CB participates in tumor growth, metastasis, and EMT process by interacting with the miR-1307-3p/SMG1 axis, and that circPPP1CB might be a novel therapeutic target and diagnostic biomarker in human BC.
Mattia Emanuela Ligotti, Fanny Pojero, Giulia Accardi, Anna Aiello, , Giovanni Duro, Giuseppina Candore
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.725606

Abstract:
The outcomes of Coronavirus disease-2019 (COVID-19) vary depending on the age, health status and sex of an individual, ranging from asymptomatic to lethal. From an immunologic viewpoint, the final severe lung damage observed in COVID-19 should be caused by cytokine storm, driven mainly by interleukin-6 and other pro-inflammatory cytokines. However, which immunopathogenic status precedes this “cytokine storm” and why the male older population is more severely affected, are currently unanswered questions. The aging of the immune system, i.e., immunosenescence, closely associated with a low-grade inflammatory status called “inflammageing,” should play a key role. The remodeling of both innate and adaptive immune response observed with aging can partly explain the age gradient in severity and mortality of COVID-19. This review discusses how aging impacts the immune response to the virus, focusing on possible strategies to rejuvenate the immune system with stem cell-based therapies. Indeed, due to immunomodulatory and anti-inflammatory properties, multipotent mesenchymal stem cells (MSCs) are a worth-considering option against COVID-19 adverse outcomes.
Enrica Urciuoli, Valentina D’Oria, Stefania Petrini,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.712377

Abstract:
Besides its structural properties in the nucleoskeleton, Lamin A/C is a mechanosensor protein involved in perceiving the elasticity of the extracellular matrix. In this study we provide evidence about Lamin A/C-mediated regulation of osteosarcoma cell adhesion and spreading on substrates with tissue-specific elasticities. Our working hypothesis is based on the observation that low-aggressive and bone-resident SaOS-2 osteosarcoma cells express high level of Lamin A/C in comparison to highly metastatic, preferentially to the lung, osteosarcoma 143B cells, thereby suggesting a role for Lamin A/C in tumor cell tropism. Specifically, LMNA gene over-expression in 143B cells induced a reduction in tumor cell aggressiveness in comparison to parental cells, with decreased proliferation rate and reduced migration capability. Furthermore, LMNA reintegration into 143B cells changed the adhesion properties of tumor cells, from a preferential tropism toward the 1.5 kPa PDMS substrate (resembling normal lung parenchyma) to the 28 kPa (resembling pre-mineralized bone osteoid matrix). Our study suggests that Lamin A/C expression could be involved in the organ tropism of tumor cells, thereby providing a rationale for further studies focused on the definition of cancer mechanism of metastatization.
Mike F. Renne,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.726261

Abstract:
Cells prepare for fluctuations in nutrient availability by storing energy in the form of neutral lipids in organelles called Lipid Droplets (LDs). Upon starvation, fatty acids (FAs) released from LDs are trafficked to different cellular compartments to be utilized for membrane biogenesis or as a source of energy. Despite the biochemical pathways being known in detail, the spatio-temporal regulation of FA synthesis, storage, release, and breakdown is not completely understood. Recent studies suggest that FA trafficking and metabolism are facilitated by inter-organelle contact sites that form between LDs and other cellular compartments such as the Endoplasmic Reticulum (ER), mitochondria, peroxisomes, and lysosomes. LD-LD contact sites are also sites where FAs are transferred in a directional manner to support LD growth and expansion. As the storage site of neutral lipids, LDs play a central role in FA homeostasis. In this mini review, we highlight the role of LD contact sites with other organelles in FA trafficking, channeling, and metabolism and discuss the implications for these pathways on cellular lipid and energy homeostasis.
Zhi-Jie Xia, Xin-Xin I. Zeng, Mitali Tambe, Bobby G. Ng, P. Duc S. Dong,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.720688

Abstract:
Saul–Wilson syndrome (SWS) is a rare, skeletal dysplasia with progeroid appearance and primordial dwarfism. It is caused by a heterozygous, dominant variant (p.G516R) in COG4, a subunit of the conserved oligomeric Golgi (COG) complex involved in intracellular vesicular transport. Our previous work has shown the intracellular disturbances caused by this mutation; however, the pathological mechanism of SWS needs further investigation. We sought to understand the molecular mechanism of specific aspects of the SWS phenotype by analyzing SWS-derived fibroblasts and zebrafish embryos expressing this dominant variant. SWS fibroblasts accumulate glypicans, a group of heparan sulfate proteoglycans (HSPGs) critical for growth and bone development through multiple signaling pathways. Consistently, we find that glypicans are increased in zebrafish embryos expressing the COG4 p.G516R variant. These animals show phenotypes consistent with convergent extension (CE) defects during gastrulation, shortened body length, and malformed jaw cartilage chondrocyte intercalation at larval stages. Since non-canonical Wnt signaling was shown in zebrafish to be related to the regulation of these processes by glypican 4, we assessed wnt levels and found a selective increase of wnt4 transcripts in the presence of COG4 p.G516R . Moreover, overexpression of wnt4 mRNA phenocopies these developmental defects. LGK974, an inhibitor of Wnt signaling, corrects the shortened body length at low concentrations but amplifies it at slightly higher concentrations. WNT4 and the non-canonical Wnt signaling component phospho-JNK are also elevated in cultured SWS-derived fibroblasts. Similar results from SWS cell lines and zebrafish point to altered non-canonical Wnt signaling as one possible mechanism underlying SWS pathology.
, Beate Winner, Franziska Richter, Gabriela Caraveo
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.752378

Abstract:
Editorial on the Research Topic Intracellular Mechanisms of α-Synuclein Processing The aggregation of the protein α-synuclein (aSyn) is the pathological hallmark of the group of neurodegenerative disorders, collectively known as synucleinopathies. These include Parkinson's disease (PD), PD-Dementia, Dementia with Lewy Bodies (DLB), and Multiple Systems Atrophy (MSA). While all of these neurodegenerative disorders present with distinctive clinical features, they all converge in one pathological characteristic: intracellular aSyn aggregation into Lewy Bodies (Mezey et al., 1998; Spillantini et al., 1998; Goedert et al., 2017; Riederer et al., 2019). Lewy Body pathology can occur at the soma and neurites of neurons, but it can also occur within glial cells as in MSA [called glial cytoplasmic inclusions (GCI)]. To complicate matters, there is increasing evidence for extracellular aSyn conformers, that might be responsible for the spreading of pathological protein aggregates and hence disease pathology (Kordower et al., 2008; Li et al., 2008), as first demonstrated in patients following fetal midbrain transplants. This findings have led to the hypothesis that sporadic PD might progress in six states that follow a caudo-rostral pattern (Braak et al., 2003), with peripheral non-motor symptoms occurring before the diagnosis of the full blown disease. Despite the central role of aSyn in all of these disorders, little is known about the initial mechanisms that lead to its aggregation, disruption of cellular functions and extracellular spread, as suggested via the gut-brain axis (Kim et al., 2019; Derkinderen et al., 2020). Articles within this Research Topic seek to shed light into these mechanisms. aSyn is typically degraded by both the lysosome and the proteasome (Cuervo et al., 2004; Shin et al., 2005). It is of no surprise that mutations in genes associated with lysosomal pathways are major genetic risk factors for the development of PD (Klein and Mazzulli, 2018). These include the lysosomal enyzmes β-glucocerebrosidase (GBA1), galactocerebrosidase (GALC), and the lysosomal cathepsins (CTSD and CTSB), as well as lysosomal membrane proteins like SCARB2, TMEM175, LAMP3, and components of the lysosomal acidification machinery (ATP13A2 and ATP6V0A1) (Sidransky et al., 2009; Chang et al., 2017; Robak et al., 2017). As shown in longitudinal studies, GBA1-associated PD patients undergo faster disease progression and shorter survival, underlying the need for novel and genotype-specific therapeutic strategies (Brockmann). GBA1 degrades the lysosomal sphingolipid glucosylceramide into glucose and ceramide. Mutations in GBA1 linked to PD, yield deficits in ceramide metabolism and result in inefficient aSyn degradation within the lysosome. Accumulation of the GBA1 substrate, glucosylceramide can lead to the conversion of physiologic to pathologic aSyn (Zunke et al., 2018), indicating lipids as one of the key factors in aSyn conformation (Kiechle et al.) (Figure 1, no. 1, 5). Figure 1. Overview of intra- and extracellular routes of aSyn aggregation and pathology pathways as highlighted within this Research Topic: (1) Intracellular aSyn aggregation can be triggered by overexpression, post translational modifications (PTMs), or mutations within aSyn (e.g., A53T, A30P). (2–5) Pathological aSyn conformers comprising oligomers and fibrils block the autophagic/lysosomal pathway by interfering with BAG5 and the autophagic adaptor protein p62 (2), the lysosomal enzymes β-glucocerebrosidase (GBA1; 3) and cathepsin D (CTSD; 4), all critical for aSyn degradation. Dysfunction of GBA1 causes glycosphingolipids (glucosylceramide, GluCer) to increase (5). These lipids further drive aSyn aggregation. Pathological aSyn conformers also affect mitochondrial function, the lysosomal-mitochondrial crosstalk (6), vesicle recycling, and endocytosis (7), as well as formation and function of the actin cytoskeleton (8). Moreover, aSyn accumulation induces microRNAs involved in cell cycle activation (9). (10) Effects of aSyn-mediated pathologies were analyzed and summarized within different models (human, murine, C. elegans), exhibiting important roles of aSyn within the hippocampus. Additionally, aSyn is capable of escaping neurons causing cell-to-cell propagation and hence spreading of disease, which causes pathological effects on peripheral immune cells (11) and the gastro intestinal tract (GIT). The gut-brain-axis contributes to the spread of pathological aSyn conformers and disease pathology (12, 13). This illustration contains images from Servier Medical Art (smart.servier.com). Further emphasizing the importance of lysosomal degradation processes in synucleinopathies (Figure 1, no. 2-5), as well as the bidirectional loop between degradative function of lysosomes and aSyn proteoforms (Wildburger et al.), lysosomal cathepsin D variants associated with neurodegenerative disorders were analyzed (Bunk et al.) (Figure 1, no. 4). Given that lysosomal cathepsins have been shown to directly process aSyn (Mcglinchey and Lee, 2015), the study of Bunk et al. also suggests enhanced aSyn proteolysis as a potential therapeutic strategy. Since the lysosome is the key organelle involved in autophagy, defects in autophagic function have been implicated in numerous neurodegenerative diseases including synucleinopathies. Highlighting the link between lysosomal autophagic pathways and aSyn accumulation, Friesen et al. describe that the co-chaperone BAG5 can promote aSyn oligomer formation, as well as regulate the levels and subcellular distribution of p62, an important autophagic adaptor protein (Friesen et al.) (Figure 1, no. 2). The structural properties and posttranslational modifications (PTMs) of aSyn play an important role in toxicity and its seeding capacity (Figure 1, no. 1, 12). To this end, Ray et al. revises the importance of aSyn structure and mutations on the biophysics of its aggregation, cell...
Yun Bai, Tao Yu, Jiezhong Deng, Yusheng Yang, Jiulin Tan, Qijie Dai, Zehua Zhang, , Jianzhong Xu
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.730095

Abstract:
The periosteum is critical for bone healing. Studies have shown that the periosteum contains periosteal stem cells (PSCs) with multidirectional differentiation potential and self-renewal ability. PSCs are activated in early fracture healing and are committed to the chondrocyte lineage, which is the basis of callus formation. However, the mechanism by which PSCs are activated and committed to chondrocytes in bone regeneration remains unclear. Here, we show that tartrate acid phosphatase (TRAP)-positive monocytes secrete CTGF to activate PSCs during bone regeneration. The loss function of TRAP-positive monocytes identifies their specific role during bone healing. Then, the secreted CTGF promotes endochondral ossification and activates PSCs in mouse bone fracture models. The secreted CTGF enhances PSC renewal by upregulating the expression of multiple pluripotent genes. CTGF upregulates c-Jun expression through αVβ5 integrin. Then, c-Jun transcription activates the transcription of the pluripotent genes Sox2, Oct4, and Nanog. Simultaneously, CTGF also activates the transcription and phosphorylation of Smad3 through αVβ5 integrin, which is the central gene in chondrogenesis. Our study indicates that TRAP-positive monocyte-derived CTGF promotes bone healing by activating PSCs and directing lineage commitment and that targeting PSCs may be an effective strategy for preventing bone non-union.
Oscar A. Peña, Alexandra Lubin, Jasmine Rowell, Yvette Hoade, Noreen Khokhar, Hanna Lemmik, Christopher Mahony, Phoebe Dace, Chianna Umamahesan,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.708113

Abstract:
Germline loss or mutation of one copy of the transcription factor GATA2 in humans leads to a range of clinical phenotypes affecting hematopoietic, lymphatic and vascular systems. GATA2 heterozygous mice show only a limited repertoire of the features observed in humans. Zebrafish have two copies of the Gata2 gene as a result of an additional round of ancestral whole genome duplication. These genes, Gata2a and Gata2b, show distinct but overlapping expression patterns, and between them, highlight a significantly broader range of the phenotypes observed in GATA2 deficient syndromes, than each one alone. In this manuscript, we use mutants for Gata2a and Gata2b to interrogate the effects on hematopoiesis of these two ohnologs, alone and in combination, during development in order to further define the role of GATA2 in developmental hematopoiesis. We define unique roles for each ohnolog at different stages of developmental myelopoiesis and for the emergence of hematopoietic stem and progenitor cells. These effects are not additive in the haploinsufficient state suggesting a redundancy between these two genes in hematopoietic stem and progenitor cells. Rescue studies additionally support that Gata2b can compensate for the effects of Gata2a loss. Finally we show that adults with loss of combined heterozygosity show defects in the myeloid compartment consistent with GATA2 loss in humans. These results build on existing knowledge from other models of GATA2 deficiency and refine our understanding of the early developmental effects of GATA2. In addition, these studies shed light on the complexity and potential structure-function relationships as well as sub-functionalization of Gata2 genes in the zebrafish model.
Erwann Pain, Sonia Shinhmar,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.722066

Abstract:
Ketogenic diets have been utilized for many years to improve health, and as a dietary approach for the treatment of a range of diseases, where the mechanism of these low carbohydrate and high fat diets is widely considered to be through the production of metabolic products of fat breakdown, called ketones. One of these diets, the medium chain triglyceride ketogenic diet, involves high fat dietary intake in the form of medium chain fatty acids (MCFAs), decanoic and octanoic acid, and is commonly used in endurance and high intensity exercises but has also demonstrated beneficial effects in the treatment of numerous pathologies including drug resistant epilepsy, cancer, and diabetes. Recent advances, using Dictyostelium discoideum as a model, have controversially proposed several direct molecular mechanisms for decanoic acid in this diet, independent of ketone generation. Studies in this model have identified that decanoic acid reduces phosphoinositide turnover, diacylglycerol kinase (DGK) activity, and also inhibits the mechanistic target of rapamycin complex 1 (mTORC1). These discoveries could potentially impact the treatment of a range of disorders including epilepsy, cancer and bipolar disorder. In this review, we summarize the newly proposed mechanisms for decanoic acid, identified using D. discoideum, and highlight potential roles in health and disease treatment.
Jing Qu, Yue Cheng, Wenchao Wu, , Xiaojing Liu
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.730621

Abstract:
The glycocalyx is a complex polysaccharide-protein layer lining the lumen of vascular endothelial cells. Changes in the structure and function of the glycocalyx promote an inflammatory response in blood vessels and play an important role in the pathogenesis of many vascular diseases (e.g., diabetes, atherosclerosis, and sepsis). Vascular endothelial dysfunction is a hallmark of inflammation-related diseases. Endothelial dysfunction can lead to tissue swelling, chronic inflammation, and thrombosis. Therefore, elimination of endothelial inflammation could be a potential target for the treatment of vascular diseases. This review summarizes the key role of the glycocalyx in the inflammatory process and the possible mechanism by which it alleviates this process by interrupting the cycle of endothelial dysfunction and inflammation. Especially, we highlight the roles of different components of the glycocalyx in modulating the inflammatory process, including components that regulate leukocyte rolling, L-selectin binding, inflammasome activation and the signaling interactions between the glycocalyx components and the vascular cells. We discuss how the glycocalyx interferes with the development of inflammation and the importance of preventing glycocalyx impairment. Finally, drawing on current understanding of the role of the glycocalyx in inflammation, we consider a potential strategy for the treatment of vascular diseases.
Zhibin Li, Sumin Wang, Chunli Gong, Yiyang Hu, Jiao Liu, Wei Wang, Yang Chen, Qiushi Liao, Bing He, Yu Huang, et al.
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.725933

Abstract:
Male infertility is a widespread health problem affecting approximately 6%–8% of the male population, and hypoxia may be a causative factor. In mammals, two types of hypoxia are known, including environmental and pathological hypoxia. Studies looking at the effects of hypoxia on male infertility have linked both types of hypoxia to poor sperm quality and pregnancy outcomes. Hypoxia damages testicular seminiferous tubule directly, leading to the disorder of seminiferous epithelium and shedding of spermatogenic cells. Hypoxia can also disrupt the balance between oxidative phosphorylation and glycolysis of spermatogenic cells, resulting in impaired self-renewal and differentiation of spermatogonia, and failure of meiosis. In addition, hypoxia disrupts the secretion of reproductive hormones, causing spermatogenic arrest and erectile dysfunction. The possible mechanisms involved in hypoxia on male reproductive toxicity mainly include excessive ROS mediated oxidative stress, HIF-1α mediated germ cell apoptosis and proliferation inhibition, systematic inflammation and epigenetic changes. In this review, we discuss the correlations between hypoxia and male infertility based on epidemiological, clinical and animal studies and enumerate the hypoxic factors causing male infertility in detail. Demonstration of the causal association between hypoxia and male infertility will provide more options for the treatment of male infertility
Wonyoung Jeong, Eek-Hoon Jho
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.714330

Abstract:
Wnt signaling plays crucial roles in development and tissue homeostasis, and its dysregulation leads to various diseases, notably cancer. Wnt/β-catenin signaling is initiated when the glycoprotein Wnt binds to and forms a ternary complex with the Frizzled and low-density lipoprotein receptor-related protein 5/6 (LRP5/6). Despite being identified as a Wnt co-receptor over 20 years ago, the molecular mechanisms governing how LRP6 senses Wnt and transduces downstream signaling cascades are still being deciphered. Due to its role as one of the main Wnt signaling components, the dysregulation or mutation of LRP6 is implicated in several diseases such as cancer, neurodegeneration, metabolic syndrome and skeletal disease. Herein, we will review how LRP6 is activated by Wnt stimulation and explore the various regulatory mechanisms involved. The participation of LRP6 in other signaling pathways will also be discussed. Finally, the relationship between LRP6 dysregulation and disease will be examined in detail.
Stefan Washausen,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.712522

Abstract:
Placodes are ectodermal thickenings of the embryonic vertebrate head. Their descendants contribute to sensory organ development, but also give rise to sensory neurons of the cranial nerves. In mammals, the signaling pathways which regulate the morphogenesis and neurogenesis of epibranchial placodes, localized dorsocaudally to the pharyngeal clefts, are poorly understood. Therefore, we performed mouse whole embryo culture experiments to assess the impact of pan-fibroblast growth factor receptor (FGFR) inhibitors, anti-FGFR3 neutralizing antibodies or the pan-bone morphogenetic protein receptor (BMPR) inhibitor LDN193189 on epibranchial development. We demonstrate that each of the three paired epibranchial placodes is regulated by a unique combination of FGF and/or bone morphogenetic protein (BMP) signaling. Thus, neurogenesis depends on fibroblast growth factor (FGF) signals, albeit to different degrees, in all epibranchial placodes (EP), whereas only EP1 and EP3 significantly rely on neurogenic BMP signals. Furthermore, individual epibranchial placodes vary in the extent to which FGF and/or BMP signals (1) have access to certain receptor subtypes, (2) affect the production of Neurogenin (Ngn)2+ and/or Ngn1+ neuroblasts, and (3) regulate either neurogenesis alone or together with structural maintenance. In EP2 and EP3, all FGF-dependent production of Ngn2+ neuroblasts is mediated via FGFR3 whereas, in EP1, it depends on FGFR1 and FGFR3. Differently, production of FGF-dependent Ngn1+ neuroblasts almost completely depends on FGFR3 in EP1 and EP2, but not in EP3. Finally, FGF signals turned out to be responsible for the maintenance of both placodal thickening and neurogenesis in all epibranchial placodes, whereas administration of the pan-BMPR inhibitor, apart from its negative neurogenic effects in EP1 and EP3, causes only decreases in the thickness of EP3. Experimentally applied inhibitors most probably not only blocked receptors in the epibranchial placodes, but also endodermal receptors in the pharyngeal pouches, which act as epibranchial signaling centers. While high doses of pan-FGFR inhibitors impaired the development of all pharyngeal pouches, high doses of the pan-BMPR inhibitor negatively affected only the pharyngeal pouches 3 and 4. In combination with partly concordant, partly divergent findings in other vertebrate classes our observations open up new approaches for research into the complex regulation of neurogenic placode development.
Yuhang Shi, Sergio Castro-Gonzalez, Yuexuan Chen,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.711481

Abstract:
Breast cancer-associated gene 2 (BCA2) is an E3 ubiquitin and SUMO ligase with antiviral properties against HIV. Specifically, BCA2 (i) enhances the restriction imposed by BST2/Tetherin, impeding viral release; (ii) promotes the ubiquitination and degradation of the HIV protein Gag, limiting virion production; (iii) down-regulates NF-κB, which is necessary for HIV RNA synthesis; and (iv) activates the innate transcription factor IRF1. Due to its antiviral properties, ectopic expression of BCA2 in infected cells represents a promising therapeutic approach against HIV infection. However, BCA2 up-regulation is often observed in breast tumors. To date, the studies about BCA2 and cancer development are controversial, stating both pro- and anti-oncogenic roles. Here, we investigated the impact of BCA2 on cellular metabolic activity, cell proliferation, cell migration, and cell cycle progression. In addition, we also examined the ability of BCA2 to regulate NF-κB and IRF1 in transformed and non-tumor breast epithelial environments. Despite the fact that BCA2 promotes the transition from G1 to S phase of the cell cycle, it did not increase cell proliferation, migration nor metabolic activity. As expected, BCA2 maintains its enzymatic function at inhibiting NF-κB in different breast cancer cell lines. However, the effect of BCA2 on IRF1 differs depending on the cellular context. Specifically, BCA2 activates IRF1 in ER+ breast cell lines while it inhibits this transcription factor in ER– breast cancer cells. We hypothesize that the distinct actions of BCA2 over IRF1 may explain, at least in part, the different proposed roles for BCA2 in these cancers.
Baoxing Tian, Mengjie Hou, Kun Zhou, Xia Qiu, Yibao Du, Yifan Gu, Xiaoxing Yin,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.717462

Abstract:
Breast cancer (BC) is the most common cancer affecting women and the leading cause of cancer-related deaths worldwide. Compelling evidence indicates that microRNAs (miRNAs) are inextricably involved in the development of cancer. Here, we constructed a novel model, based on miRNA-seq and clinical data downloaded from The Cancer Genome Atlas (TCGA). Data from a total of 962 patients were included in this study, and the relationships among their clinicopathological features, survival, and miRNA-seq expression levels were analyzed. Hsa-miR-186 and hsa-miR-361 were identified as internal reference miRNAs and used to normalize miRNA expression data. A five-miRNA signature, constructed using univariate and multivariate Cox regression, was significantly associated with disease-specific survival (DSS) of patients with BC. Kaplan–Meier (KM) and receiver operating characteristic (ROC) analyses were conducted to confirm the clinical significance of the five-miRNA signature. Finally, a nomogram was constructed based on the five-miRNA signature to evaluate its clinical value. Cox regression analysis revealed that a five-miRNA signature was significantly associated with DSS of patients with BC. KM analysis demonstrated that the signature could efficiently distinguish high- and low-risk patients. Moreover, ROC analysis showed that the five-miRNA signature exhibited high sensitivity and specificity in predicting the prognosis of patients with BC. Patients in the high-risk subgroup who received adjuvant chemotherapy had a significantly lower incidence of mortality than those who did not. A nomogram constructed based on the five-miRNA signature was effective in predicting 5-year DSS. This study presents a novel five-miRNA signature as a reliable prognostic tool to predict DSS and provide theoretical reference significance for individualized clinical decisions for patients with BC.
Siham Zentout, Rebecca Smith, Marine Jacquier,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.730998

Abstract:
DNA repair requires a coordinated effort from an array of factors that play different roles in the DNA damage response from recognizing and signaling the presence of a break, creating a repair competent environment, and physically repairing the lesion. Due to the rapid nature of many of these events, live-cell microscopy has become an invaluable method to study this process. In this review we outline commonly used tools to induce DNA damage under the microscope and discuss spatio-temporal analysis tools that can bring added information regarding protein dynamics at sites of damage. In particular, we show how to go beyond the classical analysis of protein recruitment curves to be able to assess the dynamic association of the repair factors with the DNA lesions as well as the target-search strategies used to efficiently find these lesions. Finally, we discuss how the use of mathematical models, combined with experimental evidence, can be used to better interpret the complex dynamics of repair proteins at DNA lesions.
Eimear O’Reilly, Hojjat Alizadeh Zeinabad, Caoimhe Nolan, Jamileh Sefy, Thomas Williams, Marina Tarunina, Diana Hernandez, Yen Choo,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.662868

Abstract:
The main challenge in the treatment of acute myeloid leukemia (AML) is relapse, as it has no good treatment options and 90% of relapsed patients die as a result. It is now well accepted that relapse is due to a persisting subset of AML cells known as leukemia-initiating cells or leukemic stem cells (LSCs). Hematopoietic stem cells (HSCs) reside in the bone marrow microenvironment (BMM), a specialized niche that coordinates HSC self-renewal, proliferation, and differentiation. HSCs are divided into two types: long-term HSCs (LT-HSCs) and short-term HSCs, where LT-HSCs are typically quiescent and act as a reserve of HSCs. Like LT-HSCs, a quiescent population of LSCs also exist. Like LT-HSCs, quiescent LSCs have low metabolic activity and receive pro-survival signals from the BMM, making them resistant to drugs, and upon discontinuation of therapy, they can become activated and re-establish the disease. Several studies have shown that the activation of quiescent LSCs may sensitize them to cytotoxic drugs. However, it is very difficult to experimentally model the quiescence-inducing BMM. Here we report that culturing AML cells with bone marrow stromal cells, transforming growth factor beta-1 and hypoxia in a three-dimensional system can replicate the quiescence-driving BMM. A quiescent-like state of the AML cells was confirmed by reduced cell proliferation, increased percentage of cells in the G0 cell cycle phase and a decrease in absolute cell numbers, expression of markers of quiescence, and reduced metabolic activity. Furthermore, the culture could be established as co-axial microbeads, enabling high-throughput screening, which has been used to identify combination drug treatments that could break BMM-mediated LSC quiescence, enabling the eradication of quiescent LSCs.
Marco Nuno De Canha, Velaphi Clement Thipe, Kattesh V. Katti, Vusani Mandiwana, Michel Lonji Kalombo, Suprakas Sinha Ray, Rirhandzu Rikhotso, Arno Janse van Vuuren,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.675064

Abstract:
The human skin is home to millions of bacteria, fungi, and viruses which form part of a unique microbiome. Commensal microbes, including Cutibacterium acnes can occasionally become opportunistic resulting in the onset of dermatological diseases such as acne. Acne is defined as a chronic inflammatory disorder based on its ability to persist for long periods throughout an individual’s life. The synthesis of gold nanoparticles (AuNPs) was performed using the bottom-up approach by reduction of a gold salt (HAuCl4.3H2O) by the methanol extract (HO-MeOH) and aqueous decoction prepared from the dried aerial parts of Helichrysum odoratissimum (HO-Powder). The HO-MeOH and HO-Powder AuNPs were prepared as unstabilised (−GA) or stabilized (+GA) by the omission or addition of Gum Arabic (GA) as the capping agent. The characterization of the AuNPs was performed using Transmission Electron Microscopy (TEM), dynamic light scattering (DLS), Ultraviolet-Visual spectroscopy (UV-Vis), Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD) and Zeta-potential. The MBIC50 values for HO-MeOH − GA and HO-MeOH + GA were 1.79 ± 0.78% v/v and 0.22 ± 0.16% v/v, respectively. The HO-Powder AuNPs showed potent inhibition of C. acnes cell adhesion to the 96-well plates. The HO-MeOH − GA and HO-Powder + GA exhibited IC50 of 22.01 ± 6.13% v/v and 11.78 ± 1.78% v/v, respectively. The activity of the AuNPs validated the anti-adhesion activity of the methanol extract in the crude form. The study emphasizes the selectivity of H. odoratissimum AuNPs for the prevention of C. acnes cell adhesion and not antimicrobial activity, which may prevent the emergence of resistant strains of C. acnes through reduced bactericidal or bacteriostatic activity, while targeting mechanisms of pathogenesis.
Peilin Cong, Tingmei Wu, Xinwei Huang, Huazheng Liang, Xiaofei Gao, Li Tian, Wanrong Li, Aiwen Chen, Hanxi Wan, Mengfan He, et al.
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.709022

Abstract:
M6A RNA methylation regulators can regulate the growth, progression, and invasion of glioma cells by regulating their target genes, which provides a reliable support for the m6A regulator–target axes as the novel therapeutic targets and clinical prognostic signature in glioma. This study aimed to explore the role and prognostic value of m6A RNA methylation regulators and their targets. Expression profiles and clinicopathological data were obtained from the Chinese Glioma Genome Atlas (CGGA), The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), and Clinical Proteome Tumor Analysis Consortium (CPTAC) datasets. Differential expression and correlation analyses were performed between normal and glioma tissues at mRNA and protein levels. Univariate Cox regression, survival, and Lasso Cox regression analyses were conducted to identify and establish the prognostic gene signature. Kaplan–Meier curve, multivariate Cox regression analysis, and ROC were utilized to evaluate the prognostic capacity of the prognostic gene signature. The correlation analysis, systematic bioinformatics analysis, and cell experiment were performed to further understand the potential underlying molecular mechanisms and drug sensitivity. Our results suggested that IGF2BP2, KIAA1429, METTL16, and METTL3, as well as 208 targets are involved in the occurrence of glioma, GBM, and LGG. YTHDF1 and 78 targets involved the occurrence of glioma and GBM, not LGG, among which 181 genes were associated with overall survival. From other findings and our cell experiment results, we demonstrated that METTL3 can activate Notch pathway and facilitate glioma occurrence through regulating its direct targets NOTCH3, DLL3, and HES1, and Notch pathway genes may serve as the potential treatment targets for glioma. Our study established and validated a seven-gene signature comprising METTL3, COL18A1, NASP, PHLPP2, TIMP1, U2AF2, and VEGFA, with a good capability for predicting glioma survival, which may guide therapeutic customization and clinical decision-making. These genes were identified to influence 81 anticancer drug responses, which further contributes to the early phase clinical trials of drug development.
Quan Jiang, Lingli Chen, Hao Chen, , ,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.739509

Abstract:
The immune microenvironment plays a critical role in tumor biology. As a critical feature of cancers, stemness is acknowledged as a contributor to the development of drug resistance in gastric cancers (GCs). Long non-coding RNAs (lncRNAs) have been revealed to participate in this process. In this study, we aimed to develop a stemness-related lncRNA signature (SRLncSig) with guiding significance for immunotherapy. Three cohorts (TCGA, Zhongshan, and IMvigor210) were enrolled for analysis. A list of stemness-related lncRNAs (SRlncRNAs) was collected by co-expression strategy under the threshold of coefficient value >0.35 and p-value < 0.05. Cox and Lasso regression analysis was further applied to find out the SRlncRNAs with prognosis-predictive value to establish the SRLncSig in the TCGA cohort. IPS and TIDE algorithms were further applied to predict the efficacy of SRLncSig in TCGA and Zhongshan cohorts. IMvigor210 was composed of patients with clinical outcomes of immunotherapy. The results indicated that SRLncSig not only was confirmed as an independent risk factor for GCs but also identified as a robust indicator for immunotherapy. The patient with a lower SRLncSig score was more likely to benefit from immunotherapy, and the results were highly consistent in three cohorts. In conclusion, our study not only could clarify the correlations between stemness and immunotherapy in GC patients but also provided a model to guide the applications of immunotherapy in clinical practice.
Xinyu Gu, Haibo Zhou, Qingfei Chu, Qiuxian Zheng, Jing Wang, Haihong Zhu
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.727935

Abstract:
Background: 5-Methylcytosine (m5C) plays essential roles in hepatocellular carcinoma (HCC), but the association between m5C regulation and immune cell infiltration in HCC has not yet been clarified. Methods: In this study, we analysed 371 patients with HCC from The Cancer Genome Atlas (TCGA) database, and the expression of 13 m5C regulators was investigated. Additionally, gene set variation analysis (GSVA), unsupervised clustering analysis, single-sample gene set enrichment analysis (ssGSEA), correlation analysis, and immunohistochemical (IHC) staining were performed. Results: Among the 371 patients, 41 had mutations in m5C regulators, the frequency of which was 11.26%. Compared with normal hepatic tissues, the expression of m5C regulators with copy number variations (CNVs) expansion was significantly higher than that in HCC tissues. Then, we identified three m5C modification patterns that had obvious tumour microenvironment (TME) cell infiltration characteristics. The prognostic analysis of the three major m5C modification subtypes showed that Cluster-2 had a clear survival advantage over the others. In addition, we found that DNMT1 was highly expressed in tumour tissues compared with normal tissues in a tissue microarray (TMA) and that it was positively correlated with many TME-infiltrating immune cells. High expression of the m5C regulator DNMT1 was related to a poor prognosis in patients with HCC. Furthermore, we developed three distinct Immu-clusters. Importantly, mRNAs related to the transcription of growth factor β (TGF-β)/EMT pathway were significantly up-regulated in Immu-cluster 2, indicating that this cluster is considered to be the immune rejection phenotype. Immu-cluster 3 showed elevated expression of mRNAs related to immune checkpoint genes. Conclusion: Our work revealed the association between m5C modification and immune regulators in the TME. These findings also suggest that DNMT1 has great potential as a prognostic biomarker and therapeutic target for HCC.
Lingyan Zhang, Jian Zhang, Yuanqing Jin, Gang Yao, Hai Zhao, Penghai Qiao, Shuguang Wu
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.728172

Abstract:
Iron is an essential trace mineral element in almost all living cells and organisms. However, cellular iron metabolism pathways are disturbed in most cancer cell types. Cancer cells have a high demand of iron. To maintain rapid growth and proliferation, cancer cells absorb large amounts of iron by altering expression of iron metabolism related proteins. However, iron can catalyze the production of reactive oxygen species (ROS) through Fenton reaction. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is an important player in the resistance to oxidative damage by inducing the transcription of antioxidant genes. Aberrant activation of Nrf2 is observed in most cancer cell types. It has been revealed that the over-activation of Nrf2 promotes cell proliferation, suppresses cell apoptosis, enhances the self-renewal capability of cancer stem cells, and even increases the chemoresistance and radioresistance of cancer cells. Recently, several genes involving cellular iron homeostasis are identified under the control of Nrf2. Since cancer cells require amounts of iron and Nrf2 plays pivotal roles in oxidative defense and iron metabolism, it is highly probable that Nrf2 is a potential modulator orchestrating iron homeostasis and redox balance in cancer cells. In this hypothesis, we summarize the recent findings of the role of iron and Nrf2 in cancer cells and demonstrate how Nrf2 balances the oxidative stress induced by iron through regulating antioxidant enzymes and iron metabolism. This hypothesis provides new insights into the role of Nrf2 in cancer progression. Since ferroptosis is dependent on lipid peroxide and iron accumulation, Nrf2 inhibition may dramatically increase sensitivity to ferroptosis. The combination of Nrf2 inhibitors with ferroptosis inducers may exert greater efficacy on cancer therapy.
Martina Tufano, Elena Cesaro, Rosanna Martinelli, Roberto Pacelli, ,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.718947

Abstract:
Melanoma is one of the most immunogenic tumors and has the highest potential to elicit specific adaptive antitumor immune responses. Immune cells induce apoptosis of cancer cells either by soluble factors or by triggering cell-death pathways. Melanoma cells exploit multiple mechanisms to escape immune system tumoricidal control. FKBP51 is a relevant pro-oncogenic factor of melanoma cells supporting NF-κB-mediated resistance and cancer stemness/invasion epigenetic programs. Herein, we show that FKBP51-silencing increases TNF-related apoptosis-inducing ligand (TRAIL)-R2 (DR5) expression and sensitizes melanoma cells to TRAIL-induced apoptosis. Consistent with the general increase in histone deacetylases, as by the proteomic profile, the immune precipitation assay showed decreased acetyl-Yin Yang 1 (YY1) after FKBP51 depletion, suggesting an impaired repressor activity of this transcription factor. ChIP assay supported this hypothesis. Compared with non-silenced cells, a reduced acetyl-YY1 was found on the DR5 promoter, resulting in increased DR5 transcript levels. Using Crispr/Cas9 knockout (KO) melanoma cells, we confirmed the negative regulation of DR5 by FKBP51. We also show that KO cells displayed reduced levels of acetyl-EP300 responsible for YY1 acetylation, along with reduced acetyl-YY1. Reconstituting FKBP51 levels contrasted the effects of KO on DR5, acetyl-YY1, and acetyl-EP300 levels. In conclusion, our finding shows that FKBP51 reduces DR5 expression at the transcriptional level by promoting YY1 repressor activity. Our study supports the conclusion that targeting FKBP51 increases the expression level of DR5 and sensitivity to TRAIL-induced cell death, which can improve the tumoricidal action of immune cells.
Yu Jiang, Chen Zhang, Lujue Long, Lihua Ge, Jing Guo, Zhipeng Fan, GuoXia Yu
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.721205

Abstract:
Objective: Articular cartilage injury is common and difficult to treat clinically because of the characteristics of the cartilage. Bone marrow-derived mesenchymal stem cell (BMSC)-mediated cartilage regeneration is a promising therapy for treating articular cartilage injury. BMSC differentiation is controlled by numerous molecules and signaling pathways in the microenvironment at both the transcriptional and post-transcriptional levels. However, the possible function of super enhancer long non-coding RNAs (SE-lncRNAs) in the chondrogenic differentiation of BMSCs is still unclear. Our intention was to explore the expression profile of SE-lncRNAs and potential target genes regulated by SE-lncRNAs during chondrogenic differentiation in BMSCs. Materials and Methods: In this study, we conducted a human Super-Enhancer LncRNA Microarray to investigate the differential expression profile of SE-lncRNAs and mRNAs during chondrogenic differentiation of BMSCs. Subsequent bioinformatic analysis was performed to clarify the important signaling pathways, SE-lncRNAs, and mRNAs associated with SE-lncRNAs regulating the chondrogenic differentiation of BMSCs. Results: A total of 77 SE-lncRNAs were identified, of which 47 were upregulated and 30 were downregulated during chondrogenic differentiation. A total of 308 mRNAs were identified, of which 245 were upregulated and 63 were downregulated. Some pathways, such as focal adhesion, extracellular matrix (ECM)–receptor interaction, transforming growth factor-β (TGF-β) signaling pathway, and PI3K–Akt signaling pathway, were identified as the key pathways that may be implicated in the chondrogenic differentiation of BMSCs. Moreover, five potentially core regulatory mRNAs (PMEPA1, ENC1, TES, CDK6, and ADIRF) and 37 SE-lncRNAs in chondrogenic differentiation were identified by bioinformatic analysis. Conclusion: We assessed the differential expression levels of SE-lncRNAs and mRNAs, along with the chondrogenic differentiation of BMSCs. By analyzing the interactions and co-expression, we identified the core SE-lncRNAs and mRNAs acting as regulators of the chondrogenic differentiation potential of BMSCs. Our study also provided novel insights into the mechanism of BMSC chondrogenic and cartilage regeneration.
WanBo Tang, Jian He, Tao Huang, Zhijie Bai, Chaojie Wang, Haizhen Wang, Ruichuang Yang, Yanli Ni, Jun Hou, Junliang Wang, et al.
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.728057

Abstract:
In the aorta-gonad-mesonephros (AGM) region of mouse embryos, pre-hematopoietic stem cells (pre-HSCs) are generated from rare and specialized hemogenic endothelial cells (HECs) via endothelial-to-hematopoietic transition, followed by maturation into bona fide hematopoietic stem cells (HSCs). As HECs also generate a lot of hematopoietic progenitors not fated to HSCs, powerful tools that are pre-HSC/HSC-specific become urgently critical. Here, using the gene knockin strategy, we firstly developed an Hlf-tdTomato reporter mouse model and detected Hlf-tdTomato expression exclusively in the hematopoietic cells including part of the immunophenotypic CD45– and CD45+ pre-HSCs in the embryonic day (E) 10.5 AGM region. By in vitro co-culture together with long-term transplantation assay stringent for HSC precursor identification, we further revealed that unlike the CD45– counterpart in which both Hlf-tdTomato-positive and negative sub-populations harbored HSC competence, the CD45+ E10.5 pre-HSCs existed exclusively in Hlf-tdTomato-positive cells. The result indicates that the cells should gain the expression of Hlf prior to or together with CD45 to give rise to functional HSCs. Furthermore, we constructed a novel Hlf-CreER mouse model and performed time-restricted genetic lineage tracing by a single dose induction at E9.5. We observed the labeling in E11.5 AGM precursors and their contribution to the immunophenotypic HSCs in fetal liver (FL). Importantly, these Hlf-labeled early cells contributed to and retained the size of the HSC pool in the bone marrow (BM), which continuously differentiated to maintain a balanced and long-term multi-lineage hematopoiesis in the adult. Therefore, we provided another valuable mouse model to specifically trace the fate of emerging HSCs during development.
Ye Xie, , Lu Nie, Wanting Zhang, Zijun Ke,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.734046

Abstract:
Repetitive transcranial magnetic stimulation (rTMS), a non-invasive brain stimulation technique, has been considered as a potentially effective treatment for the cognitive impairment in patients with mild cognitive impairment (MCI) and Alzheimer’s Disease (AD). However, the effectiveness of this therapy is still under debate due to the variety of rTMS parameters and individual differences including distinctive stages of AD in the previous studies. The current meta-analysis is aiming to assess the cognitive enhancement of rTMS treatment on patients of MCI and early AD. Three datasets (PubMed, Web of Science and CKNI) were searched with relative terms and finally twelve studies with 438 participants (231 in the rTMS group and 207 in the control group) in thirteen randomized, double-blind and controlled trials were included. Random effects analysis revealed that rTMS stimulation significantly introduced cognitive benefits in patients of MCI and early AD compared with the control group (mean effect size, 1.17; 95% CI, 0.76 - 1.57). Most settings of rTMS parameters (frequency, session number, stimulation site number) significantly enhanced global cognitive function, and the results revealed that protocols with 10 Hz repetition frequency and DLPFC as the stimulation site for 20 sessions can already be able to produce cognitive improvement. The cognitive enhancement of rTMS could last for one month after the end of treatment and patients with MCI were likely to benefit more from the rTMS stimulation. Our meta-analysis added important evidence to the cognitive enhancement of rTMS in patients with MCI and early AD and discussed potential underlying mechanisms about the effect induced by rTMS.
Xuda Liu, Haiying Wang, Bingchen Liu, Zhipeng Qi, Jiashuo Li, Bin Xu, Wei Liu, Zhaofa Xu,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.681238

Abstract:
Eukaryotic messenger mRNAs contain many RNA methyl chemical modifications, in which N6-methyladenosine (m6A) plays a very important role. The modification process of RNA methylation is a dynamic reversible regulatory process that is mainly catalyzed by “Writer” m6A methyltransferase, removed by “Eraser” m6A demethylase, and recognized by the m6A binding protein, thereby, linking m6A modification with other mRNA pathways. At various stages of the life cycle, m6A modification plays an extremely important role in regulating mRNA splicing, processing, translation, as well as degradation, and is associated with gametogenesis and fertility for both sexes. Normal gametogenesis is a basic guarantee of fertility. Infertility leads to trauma, affects harmony in the family and seriously affects the quality of life. We review the roles and mechanisms of RNA m6A methylation modification in infertility and provide a potential target for infertility treatment, which can be used for drug development.
Mathilde Bergamelli, Hélène Martin, Mélinda Bénard, Jérôme Ausseil, Jean-Michel Mansuy, Ilse Hurbain, Maïlys Mouysset, Marion Groussolles, Géraldine Cartron, Yann Tanguy le Gac, et al.
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.689122

Abstract:
Extracellular vesicles (EVs) have increasingly been recognized as key players in a wide variety of physiological and pathological contexts, including during pregnancy. Notably, EVs appear both as possible biomarkers and as mediators involved in the communication of the placenta with the maternal and fetal sides. A better understanding of the physiological and pathological roles of EVs strongly depends on the development of adequate and reliable study models, specifically at the beginning of pregnancy where many adverse pregnancy outcomes have their origin. In this study, we describe the isolation of small EVs from a histoculture model of first trimester placental explants in normal conditions as well as upon infection by human cytomegalovirus. Using bead-based multiplex cytometry and electron microscopy combined with biochemical approaches, we characterized these small EVs and defined their associated markers and ultrastructure. We observed that infection led to changes in the expression level of several surface markers, without affecting the secretion and integrity of small EVs. Our findings lay the foundation for studying the functional role of EVs during early pregnancy, along with the identification of new predictive biomarkers for the severity and outcome of this congenital infection, which are still sorely lacking.
Fide Sevgi, Eva M. Brauchle, Daniel A. Carvajal Berrio, Katja Schenke-Layland, Nicolas Casadei, Madhuri S. Salker, Olaf Riess,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.664365

Abstract:
A hallmark of Parkinson’s disease (PD) is the formation of Lewy bodies in the brain. Lewy bodies are rich in the aggregated form of misfolded α-Synuclein (α-Syn). The brain from PD patients can only be analyzed after postmortem, therefore, limiting the diagnosis of PD to the manifestation of motor symptoms. In PD patients and animal models, phosphorylated α-Syn was detected in the peripheral tissues including the gut, thus, raising the hypothesis that early-stage PD could be diagnosed based on colon tissue biopsies. Non-invasive marker-free technologies represent ideal methods to potentially detect aggregated α-Syn in vivo. Raman microspectroscopy has been established for the detection of molecular changes such as alterations of protein structures. Using Raman imaging and microspectroscopy, we analyzed the olfactory bulb in the brain and the muscularis mucosae of colon tissue sections of a human BAC-SNCA transgenic (TG) rat model. Raman images from TG and WT rats were investigated using principal component analysis (PCA) and true component analysis (TCA). Spectral components indicated protein aggregates (spheroidal oligomers) in the TG rat brain and in the colon tissues even at a young age but not in WT. In summary, we have demonstrated that Raman imaging is capable of detecting α-Syn aggregates in colon tissues of a PD rat model and making it a promising tool for future use in PD pathology.
, Ting Wen, Peng Wu, Rui Jia, Ronghua Zhang, Jingxia Dang
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.718803

Abstract:
Recent advances in the neurobiology and neurogenerative diseases have attracted growing interest in exosomes and their ability to carry and propagate active biomolecules as a means to reprogram recipient cells. Alterations in exosomal protein content and nucleic acid profiles found in human biological fluids have been correlated with various diseases including amyotrophic lateral sclerosis (ALS). In ALS pathogenesis, these lipid-bound nanoscale vesicles have emerged as valuable candidates for diagnostic biomarkers. Moreover, their capacity to spread misfolded proteins and functional non-coding RNAs to interconnected neuronal cells make them putative mediators for the progressive motor degeneration found remarkably apparent in ALS. This review outlines current knowledge concerning the biogenesis, heterogeneity, and function of exosomes in the brain as well as a comprehensive probe of currently available literature on ALS-related exosomal proteins and microRNAs. Lastly, with the rapid development of employing nanoparticles for drug delivery, we explore the therapeutic potentials of exosomes as well as underlying limitations in current isolation and detection methodologies.
, Mina Abedi, Maryam Arabi, Sepideh Alavi-Moghadam, Mostafa Rezaei-Tavirani, Mahdieh Hadavandkhani, Akram Tayanloo-Beik, Ramin Kordi, Peyvand Parhizkar Roudsari, Bagher Larijani
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.704903

Abstract:
Cardiovascular disease is now the leading cause of adult death in the world. According to new estimates from the World Health Organization, myocardial infarction (MI) is responsible for four out of every five deaths due to cardiovascular disease. Conventional treatments of MI are taking aspirin and nitroglycerin as intermediate treatments and injecting antithrombotic agents within the first 3 h after MI. Coronary artery bypass grafting and percutaneous coronary intervention are the most common long term treatments. Since none of these interventions will fully regenerate the infarcted myocardium, there is value in pursuing more innovative therapeutic approaches. Regenerative medicine is an innovative interdisciplinary method for rebuilding, replacing, or repairing the missed part of different organs in the body, as similar as possible to the primary structure. In recent years, regenerative medicine has been widely utilized as a treatment for ischemic heart disease (one of the most fatal factors around the world) to repair the lost part of the heart by using stem cells. Here, the development of mesenchymal stem cells causes a breakthrough in the treatment of different cardiovascular diseases. They are easily obtainable from different sources, and expanded and enriched easily, with no need for immunosuppressing agents before transplantation, and fewer possibilities of genetic abnormality accompany them through multiple passages. The production of new cardiomyocytes can result from the transplantation of different types of stem cells. Accordingly, due to its remarkable benefits, stem cell therapy has received attention in recent years as it provides a drug-free and surgical treatment for patients and encourages a more safe and feasible cardiac repair. Although different clinical trials have reported on the promising benefits of stem cell therapy, there is still uncertainty about its mechanism of action. It is important to conduct different preclinical and clinical studies to explore the exact mechanism of action of the cells. After reviewing the pathophysiology of MI, this study addresses the role of tissue regeneration using various materials, including different types of stem cells. It proves some appropriate data about the importance of ethical problems, which leads to future perspectives on this scientific method.
Marcela Soledad Bertolio, Anabela La Colla, Alejandra Carrea, Ana Romo, Gabriela Canziani, Stella Maris Echarte, Sabrina Campisano, German Patricio Barletta, Alexander Miguel Monzon, Tania Melina Rodríguez, et al.
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.690397

Abstract:
We describe, for the first time, a new splice variant of the human TGF-β type II receptor (TβRII). The new transcript lacks 149 nucleotides, resulting in a frameshift and the emergence of an early stop codon, rendering a truncated mature protein of 57 amino acids. The predicted protein, lacking the transmembrane domain and with a distinctive 13-amino-acid stretch at its C-terminus, was named TβRII-Soluble Endogenous (TβRII-SE). Binding predictions indicate that the novel 13-amino-acid stretch interacts with all three TGF-β cognate ligands and generates a more extensive protein–protein interface than TβRII. TβRII-SE and human IgG1 Fc domain were fused in frame in a lentiviral vector (Lv) for further characterization. With this vector, we transduced 293T cells and purified TβRII-SE/Fc by A/G protein chromatography from conditioned medium. Immunoblotting revealed homogeneous bands of approximately 37 kDa (reduced) and 75 kDa (non-reduced), indicating that TβRII-SE/Fc is secreted as a disulfide-linked homodimer. Moreover, high-affinity binding of TβRII-SE to the three TGF-β isoforms was confirmed by surface plasmon resonance (SPR) analysis. Also, intrahepatic delivery of Lv.TβRII-SE/Fc in a carbon tetrachloride-induced liver fibrosis model revealed amelioration of liver injury and fibrosis. Our results indicate that TβRII-SE is a novel member of the TGF-β signaling pathway with distinctive characteristics. This novel protein offers an alternative for the prevention and treatment of pathologies caused by the overproduction of TGF-β ligands.
Anna Sloutskin, Hila Shir-Shapira, Richard N. Freiman,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.666508

Abstract:
The development of multicellular organisms and the uniqueness of each cell are achieved by distinct transcriptional programs. Multiple processes that regulate gene expression converge at the core promoter region, an 80 bp region that directs accurate transcription initiation by RNA polymerase II (Pol II). In recent years, it has become apparent that the core promoter region is not a passive DNA component, but rather an active regulatory module of transcriptional programs. Distinct core promoter compositions were demonstrated to result in different transcriptional outputs. In this mini-review, we focus on the role of the core promoter, particularly its downstream region, as the regulatory hub for developmental genes. The downstream core promoter element (DPE) was implicated in the control of evolutionarily conserved developmental gene regulatory networks (GRNs) governing body plan in both the anterior-posterior and dorsal-ventral axes. Notably, the composition of the basal transcription machinery is not universal, but rather promoter-dependent, highlighting the importance of specialized transcription complexes and their core promoter target sequences as key hubs that drive embryonic development, differentiation and morphogenesis across metazoan species. The extent of transcriptional activation by a specific enhancer is dependent on its compatibility with the relevant core promoter. The core promoter content also regulates transcription burst size. Overall, while for many years it was thought that the specificity of gene expression is primarily determined by enhancers, it is now clear that the core promoter region comprises an important regulatory module in the intricate networks of developmental gene expression.
, Ze-Hao Zheng, Jian-Xi Wang, Zhen Zhao, Tian-Yi Peng
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.726323

Abstract:
Background: Tumor-derived exosomes (EXOs), commonly differentially expressed in circular RNAs, have been shown to be crucial determinants of tumor progression and may regulate the development and metastasis of hepatic carcinoma (HCC). Methods: Possibly differentially expressed circRNAs in patients with HCC were screened out from the Gene Expression Omnibus (GEO). EXOs were isolated from the culture medium of HCC cells and plasma of patients with HCC, followed by characterization by transmission electron microscope, NanHCCight, and western blotting. Additionally, RNA immunoprecipitation and luciferase reporter gene assays were carried out to explore the molecular mechanism of hsa_circRNA_103809 (circ-0072088) in HCC cells. Results: The screening results showed that circ-0072088 was highly expressed in patients with HCC, and its increase indicated unfavorable prognosis of patients according to quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Additionally, circ-0072088 was mainly secreted by HCC cells via EXOs in plasma of such patients, and its high level in plasma EXOs was closely associated with tumor node metastasis (TNM) staging and tumor size. Moreover, HCC-secreted EXOs mediated the degradation of miR-375 via circ-0072088 and upregulated MMP-16, thus suppressing the metastasis of HCC. Conclusion: Upregulated in patients with HCC, circ-0072088 may be an index for diagnosis and prognosis of HCC. In addition, HCC-derived EXOs coated with circ-0072088 might be a treatment for HCC, with the ability to inhibit the metastasis of HCC cells.
Yuting Lu, Jiangtao Jin, Qi Du, Min Hu, Yuhan Wei, Miao Wang, Hongzhong Li,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.730240

Abstract:
The combination of immune-checkpoint blockade (ICB) and lenvatinib has demonstrated robust clinical effects that are superior to those of monotherapies, but the synergistic anti-tumor mechanisms remain unclear. Exploring the synergistic molecular mechanisms and early identifying potential application have key importance for clinical therapeutics. We firstly systematically reviewed published data of ICB in combination with lenvatinib for the treatment of cancer by meta-analysis. A subsequent bioinformatics analysis explored the mechanism of combined ICB and lenvatinib therapy in 33 cancer types. Transcriptomic analysis was conducted by RNA-seq, and genomic analysis was performed on gene mutations and copy-number alteration data. Tumor-related pathways and tumor immune micro-environment (TIME) were also investigated. The meta-analysis showed a 38.0% objective response rate (ORR) and 79% disease control rate (DCR) for ICB combined with lenvatinib. Multi-omics analysis revealed that ICB and lenvatinib target genes were highly expressed and showed driving alterations in six specific malignancies. Pathway-enrichment analysis found target genes were implicated in tumor development, angiogenesis, and immunoregulatory associated pathways. This study verified the potential synergistic mechanisms of ICB combined with lenvatinib at transcriptomics, genomics, protein, and cellular levels and recognized nine tumor types had ≥ 2 positive treatment-related molecular characteristics, which might benefit particularly from this combined strategy. The findings would help to provide clinical insights and theoretical basis for optimizing of targeted therapy-immunotherapy combinations, and for guiding individualized precision-medicine approaches for cancer treatment.
Frederic Abou Azar,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.709823

Abstract:
The canonical Wnt signaling pathway is ubiquitous throughout the body and influences a diverse array of physiological processes. Following the initial discovery of the Wnt signaling pathway during wing development in Drosophila melanogaster, it is now widely appreciated that active Wnt signaling in mammals is necessary for the development and growth of various tissues involved in whole-body metabolism, such as brain, liver, pancreas, muscle, and adipose. Moreover, elegant gain- and loss-of-function studies have dissected the tissue-specific roles of various downstream effector molecules in the regulation of energy homeostasis. This review attempts to highlight and summarize the contributions of the Wnt signaling pathway and its downstream effectors on whole-body metabolism and their influence on the development of metabolic diseases, such as diabetes and obesity. A better understanding of the Wnt signaling pathway in these tissues may aid in guiding the development of future therapeutics to treat metabolic diseases.
Xiao Sheng, Yuedan Zhu, Juanyu Zhou, La Yan, Gang Du, Zhiming Liu, Haiyang Chen
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.735483

Abstract:
The dysfunction or exhaustion of adult stem cells during aging is closely linked to tissue aging and age-related diseases. Circumventing this aging-related exhaustion of adult stem cells could significantly alleviate the functional decline of organs. Therefore, identifying small molecular compounds that could prevent the age-related decline of stem cell function is a primary goal in anti-aging research. Caffeic acid (CA), a phenolic compound synthesized in plants, offers substantial health benefits for multiple age-related diseases and aging. However, the effects of CA on adult stem cells remain largely unknown. Using the Drosophila midgut as a model, this study showed that oral administration with CA significantly delayed age-associated Drosophila gut dysplasia caused by the dysregulation of intestinal stem cells (ISCs) upon aging. Moreover, administering CA retarded the decline of intestinal functions in aged Drosophila and prevented hyperproliferation of age-associated ISC by suppressing oxidative stress-associated JNK signaling. On the other hand, CA supplementation significantly ameliorated the gut hyperplasia defect and reduced environmentally induced mortality, revealing the positive effects of CA on tolerance to stress responses. Taken together, our findings report a crucial role of CA in delaying age-related changes in ISCs of Drosophila.
Takuto Tokuhiro, Akane Ishikawa, Haruka Sato, Shunya Takita, Ayuri Yoshikawa, Ryoko Anzai, Shinichi Sato, Ryohei Aoyagi, Makoto Arita, Takumi Shibuya, et al.
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.718586

Abstract:
Neutrophil extracellular traps (NETs) are web-like structures consisting of decondensed chromatin DNA and contents of granules, such as myeloperoxidase (MPO) and neutrophil elastase (NE). NETs are usually released from neutrophils undergoing NETosis, a neutrophil-specific cell death mode characterized by the collapse and disappearance of cell membranes and nuclear envelopes. It is well known that production of reactive oxygen species (ROS) triggers NETosis and NET formation. However, details of intracellular signaling downstream of ROS production during NETosis and NET formation remains uncertain. Here, we demonstrated that the peroxidation of phospholipids plays a critical role in NETosis and NET formation induced by phorbol 12-myristate13-acetate (PMA) or immune complex in vitro and by lipopolysaccharide (LPS) in vivo. This phospholipid peroxidation is mediated by the enzymatic activity of MPO. On the other hand, NE, which was previously reported to be released from granules to cytosol by MPO during NET formation, is not required for either the peroxidation of phospholipids or the execution of NETosis, but contributes to chromatin decondensation and nuclear swelling independently of MPO-mediated oxidized phospholipids. Analysis of isolated nuclei clearly demonstrated that oxidized phospholipids and NE differently yet synergistically execute chromatin decondensation and nuclear swelling, and the subsequent release of nuclear contents. These findings indicate the dual roles of MPO in NETosis and NET formation, and provide new insight into the molecular mechanism of these phenomena.
, Alexander A. Mongin, Giovanna Valenti, Yasunobu Okada
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.757033

Abstract:
Editorial on the Research Topic Ion and Water Transport in Cell Death The flow of water across cellular membranes determines the dynamics of cellular hydration and volume, both of which govern a plentitude of fundamental functions, including cell death (CD) (Lang et al., 1993, 1998, 2007; Haussinger, 1996; Hoffmann et al., 2009; Okada et al., 2021; Okada et al.). The aforementioned reviews suggest that changes in the directionality of water transport involve a variety of mechanisms; they can be osmotically obligated in their nature and coupled to the movement of ions and organic osmolytes, driven by hydrostatic pressure, or determined by “ingestion” and “excretion” during endo/exocytotic processes. The significance of water transport and cell volume in CD has been recognized for a long time. Injurious cell swelling, which was initially described as oncosis (from Greek Óγκoς, i.e. tumor/swelling), represents a hallmark of the unregulated form of CD—necrosis (von Recklinghausen, 1910; Majno and Joris, 1995; Weerasinghe and Buja, 2012). Similar increases in cell volume are prominent in several other related modes of CD, such as secondary necrosis (aponecrosis), pyroptosis, and ferroptosis (Formigli et al., 2000; Zong and Thompson, 2006; Silva, 2010; D'Arcy, 2019; Okada et al., 2019; Nirmala and Lopus, 2020; Riegman et al., 2020). While necrosis was initially considered to be a result of uncontrolled water accumulation, recent studies suggest that this form of CD starts with tightly controlled normotonic cell swelling, termed necrotic volume increase (NVI) (Barros et al., 2001; Okada et al., 2001, 2021; Orlov and Hamet, 2004; Lang and Hoffmann, 2013a,b; Orlov et al., 2013a,b; Bortner and Cidlowski, 2014; Model, 2014; Bortner and Cidlowski). In contrast, the highly regulated mode of CD, apoptosis, is generally associated with cell volume decrease (Majno and Joris, 1995; Lang et al., 1998; Maeno et al., 2000; Hoffmann et al., 2009). Apoptosis is initiated by the early and precisely regulated normotonic cell shrinkage, termed apoptotic volume decrease (AVD), which is driven by activation of distinct ion channels and transporters (Maeno et al., 2000; Okada et al., 2001). Additionally, the emerging research indicates that the precise regulation of ion and water transport across organellar membranes is also indispensable for normal cell function, and its disturbances may cause CD and disease (Maltese and Overmeyer, 2014; Li et al., 2020; Saric and Freeman, 2020; Chadwick et al., 2021; Bouteau et al.; Ritter et al.; Urbani et al.). Apart from the two major types of CD, apoptosis and necrosis, numerous additional (sub)forms of CD have been identified. These include aponecrosis, oncosis, necroptosis, parthanatos, anoikis, entotic CD, NETotic CD, immunogenic CD, lysosome-dependent CD, ferroptosis, oxeiptosis, sarmoptosis, autosis, autolysis, paraptosis, pyroptosis, alkaliptosis, phagoptosis, eryptosis, chondroptosis, autophagic CD, mitoptosis, methuosis, and the mitotic catastrophe-driven CD (Galluzzi et al., 2018). Although all these forms of CD involve very diverse and distinct mechanisms (Green and Llambi, 2015; Galluzzi et al., 2018; Nirmala and Lopus, 2020), their successful execution relies on tightly regulated transport of ions, organic solutes and water across the plasma membrane and/or organelle membranes (Lang et al., 1998; Okada and Maeno, 2001; Chen et al., 2008; Hoffmann et al., 2009; Orlov et al., 2013c; Maltese and Overmeyer, 2014; Mongin, 2016; Okada et al., 2019, 2021; Okada et al.). Understanding these mechanisms is crucial for our comprehension of the basic principles of normal and abnormal biological processes. The objective of this Research Topic was to collect state-of-the-art Reviews and cutting-edge original research articles exploring ions and water transport in cell death. This timely subject has attracted significant enthusiasm of the scientific community. The initial Call for Contributions resulted in 23 accepted manuscripts covering various aspects of the pivotal roles of ion and water transport in cell death. The collection encompasses four Original Research papers (Centeio et al.; Kittl et al.; Wei et al.; Yurinskaya et al.), two Brief Research Reports (Rana and Model; Matsuura et al.), 11 Reviews (Bachmann et al.; Bortner and Cidlowski; Bose et al.; Chen et al.; Dias et al.; Foller and Lang; Kim et al.; Lefranc; Ritter et al.; Okada et al.; Shimizu et al.), four Mini Reviews (Kolbrink et al.; Urbani et al.; Amiri et al.; Shiozaki et al.), one Hypotheses article (Shen et al.), and one Opinion article (Bouteau et al.) These publications are contributed by 98 authors. While in the production, the Research Topic was met with high interest within the scientific community; it accumulates the steadily increasing number of views and downloads from all parts of the world (https://www.frontiersin.org/research-topics/13260/ion-and-water-transport-in-cell-death#impact). The articles in this Research Topic cover a large variety of types of CD, including apoptosis (Bachmann et al.; Bortner and Cidlowski; Okada et al.; Rana and Model; Shimizu et al.; Urbani et al.; Yurinskaya et al.; Shiozaki et al.; Lefranc), necrosis (Bouteau et al.; Kittl et al.; Okada et al.; Lefranc), aponecrosis (Wei et al.), necroptosis and pyroptosis (Kolbrink et al.; Okada et al.), ferroptosis (Chen et al.; Okada et al.; Shen et al.; Lefranc), paraptosis (Kim et al.), eryptosis (Dias et al.; Foller and Lang), methuosis (Ritter et al.) as well as plant vacuolar CD (Bouteau et al.). From the standpoint of the mechanisms of CD-inducing processes, the Topic contributors discuss the functional significance of numerous specific anion channels, cation channels, and ion transporters (Bachmann et al.; Bortner and Cidlowski; Bouteau et al.; Kim et al.; Kittl et al.; Kolbrink et al.; Okada et al.; Rana and Model; Shen et al.; Shimizu et al.; Urbani et al.; Wei...
Simin Liang, Xiaojia Zhou, Duo Cai, Fernando Rodrigues-Lima, Jianxiang Chi, Li Wang
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.685954

Abstract:
Chidamide (CDM), a novel histone deacetylase inhibitor, is currently used for patients with peripheral T-cell lymphoma. Aspirin (ASA), an anti-inflammatory drug, has been shown to exert anticancer activity. Herein, we investigated the effect of CDM combined with ASA on myelodysplastic syndromes-derived acute myeloid leukemia (AML-MDS) cells and explored the underlying mechanism. The putative targets of CDM and ASA were predicted by network pharmacology approach. GO functional and KEGG pathway enrichment analyses were performed by DAVID. Furthermore, experimental validation was conducted by Cell Counting Kit-8 assay, Flow cytometry and Western blotting. Network pharmacology analysis revealed 36 AML-MDS-related overlapping genes that were targets of CDM and ASA, while 10 hub genes were identified by the plug-in cytoHubba in Cytoscape. Pathway enrichment analysis indicated CDM and ASA significantly affected PI3K/AKT signaling pathway. Functional experiments demonstrated that the combination of CDM and ASA had a remarkable synergistic anti-proliferative effect by blocking the cell cycle in G0/G1 phase and inducing apoptosis. Mechanistically, the combination treatment significantly down-regulated the phosphorylation levels of PI3K and AKT. In addition, insulin-like growth factor 1 (IGF-1), an activator of PI3K/AKT pathway, reversed the effects of the combination treatment. Our findings suggested that CDM combined with ASA exerted a synergetic inhibitory effect on cell growth by inactivating PI3K/AKT pathway, which might pave the way for effective treatments of AML-MDS.
Zhijing Ren, Qinqin Yang, Jiajia Guo, Haifeng Huang, Bo Li, Zhen Yang, Xiaobin Tian
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.714601

Abstract:
Objective: An increasing number of studies have demonstrated that circular RNAs (circRNAs) are involved in tumor progression. However, the role of hsa_circ_0000073 in osteosarcoma (OS) is still not fully elucidated. Methods: Quantitative reverse transcription-polymerase chain reaction or Western blot was used to detect the gene expression. GeneChip analysis, bioinformatics, luciferase reporter, and RNA immunoprecipitation assays were adopted to predict and verify the relationships between genes. Counting Kit-8 Assay, clone formation assay, wound-healing assay, transwell assays, cell cycle assays, and in vivo tumorigenesis were used to evaluate cell function. Results: hsa_circ_0000073 was highly expressed in OS cell lines and could promote OS progression, including proliferation, migration, invasion, and cell cycle in vitro as well as tumorigenesis in vivo. Mechanically, hsa_circ_0000073 could readily downregulate the expression of CCNE2 and MDM2 through miR-1252-5p. Rescue experiments validated miR-1252-5p mimics, or CCNE2/MDM2 short hairpin RNA could reverse the hsa_circ_0000073 overexpressing-induced impairment of malignant tumor behavior. Conclusion: hsa_circ_0000073 functions as a tumor promoter in OS to increase malignant tumor behavior through sponging miR-1252-5p and regulating CCNE2 and MDM2 expression, which could be a novel target for OS therapy.
Maria Vulf, Daria Shunkina, Aleksandra Komar, Maria Bograya, Pavel Zatolokin, Elena Kirienkova, Natalia Gazatova, Ivan Kozlov, Larisa Litvinova
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.736677

Abstract:
Non-alcoholic fatty liver disease (NAFLD) is emerging as one of the most common chronic liver diseases worldwide, affecting 25% of the world population. In recent years, there has been increasing evidence for the involvement of microRNAs in the epigenetic regulation of genes taking part in the development of steatosis and steatohepatitis—two main stages of NAFLD pathogenesis. In the present study, miRNA profiles were studied in groups of patients with steatosis and steatohepatitis to compare the characteristics of RNA-dependent epigenetic regulation of the stages of NAFLD development. According to the results of miRNA screening, 23 miRNAs were differentially expressed serum in a group of patients with steatohepatitis and 2 in a group of patients with steatosis. MiR-195-5p and miR-16-5p are common differentially expressed miRNAs for both steatosis and steatohepatitis. We analyzed the obtained results: the search for target genes for the differentially expressed miRNAs in our study and the subsequent gene set enrichment analysis performed on KEGG and REACTOME databases revealed which metabolic pathways undergo changes in RNA-dependent epigenetic regulation in steatosis and steatohepatitis. New findings within the framework of this study are the dysregulation of neurohumoral pathways in the pathogenesis of NAFLD as an object of changes in RNA-dependent epigenetic regulation. The miRNAs differentially expressed in our study were found to target 7% of genes in the classic pathogenesis of NAFLD in the group of patients with steatosis and 50% in the group of patients with steatohepatitis. The effects of these microRNAs on genes for the pathogenesis of NAFLD were analyzed in detail. MiR-374a-5p, miR-1-3p and miR-23a-3p do not target genes directly involved in the pathogenesis of NAFLD. The differentially expressed miRNAs found in this study target genes largely responsible for mitochondrial function. The role of miR-423-5p, miR-143-5p and miR-200c-3 in regulating apoptotic processes in the liver and hepatocarcinogenesis is of interest for future experimental studies. These miR-374a, miR-143, miR-1, miR-23a, and miR-423 have potential for steatohepatitis diagnosis and are poorly studied in the context of NAFLD. Thus, this work opens up prospects for further studies of microRNAs as diagnostic and therapeutic biomarkers for NAFLD.
Albert Manzano-Muñoz, Clara Alcon, Pablo Menéndez, Manuel Ramírez, Felix Seyfried, Klaus-Michael Debatin, Lüder H. Meyer, Josep Samitier,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.695225

Abstract:
Multiple targeted therapies are currently explored for pediatric and young adult B-cell precursor acute lymphoblastic leukemia (BCP-ALL) treatment. However, this new armamentarium of therapies faces an old problem: choosing the right treatment for each patient. The lack of predictive biomarkers is particularly worrying for pediatric patients since it impairs the implementation of new treatments in the clinic. In this study, we used the functional assay dynamic BH3 profiling (DBP) to evaluate two new treatments for BCP-ALL that could improve clinical outcome, especially for relapsed patients. We found that the MEK inhibitor trametinib and the multi-target tyrosine kinase inhibitor sunitinib exquisitely increased apoptotic priming in an NRAS-mutant and in a KMT2A-rearranged cell line presenting a high expression of FLT3, respectively. Following these observations, we sought to study potential adaptations to these treatments. Indeed, we identified with DBP anti-apoptotic changes in the BCL-2 family after treatment, particularly involving MCL-1 – a pro-survival strategy previously observed in adult cancers. To overcome this adaptation, we employed the BH3 mimetic S63845, a specific MCL-1 inhibitor, and evaluated its sequential addition to both kinase inhibitors to overcome resistance. We observed that the metronomic combination of both drugs with S63845 was synergistic and showed an increased efficacy compared to single agents. Similar observations were made in BCP-ALL KMT2A-rearranged PDX cells in response to sunitinib, showing an analogous DBP profile to the SEM cell line. These findings demonstrate that rational sequences of targeted agents with BH3 mimetics, now extensively explored in clinical trials, may improve treatment effectiveness by overcoming anti-apoptotic adaptations in BCP-ALL.
Xiuping Yang, Baoai Han, Zuhong He, Ya Zhang, Kun Lin, Hongguo Su, Davood K. Hosseini, , Minlan Yang,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.715027

Abstract:
The abnormality of RNA-binding proteins (RBPs) is closely related to the tumorigenesis and development of esophageal squamous cell carcinoma (ESCC), and has been an area of interest for research recently. In this study, 162 tumors and 11 normal samples are obtained from The Cancer Genome Atlas database, among which 218 differentially expressed RBPs are screened. Finally, a prognostic model including seven RBPs (CLK1, DDX39A, EEF2, ELAC1, NKRF, POP7, and SMN1) is established. Further analysis reveals that the overall survival (OS) rate of the high-risk group is lower than that of the low-risk group. The area under the receiver operating characteristic (ROC) curve (AUC) of the training group and testing group is significant (AUCs of 3 years are 0.815 and 0.694, respectively, AUCs of 5 years are 0.737 and 0.725, respectively). In addition, a comprehensive analysis of seven identified RBPs shows that most RBPs are related to OS in patients with ESCC, among which EEF2 and ELCA1 are differentially expressed at the protein level of ESCC and control tissues. CLK1 and POP7 expressions in esophageal cancer tumor samples are undertaken using the tissue microarray, and show that CLK1 mRNA levels are relatively lower, and POP7 mRNA levels are higher compared with non-cancerous esophageal tissues. Survival analysis reveals that a higher expression of CLK1 predicts a significant worse prognosis, and a lower expression of POP7 predicts a worse prognosis in esophageal cancer. These results suggest that CLK1 may promote tumor progression, and POP7 may hinder the development of esophageal cancer. In addition, gene set enrichment analysis reveals that abnormal biological processes related to ribosomes and abnormalities in classic tumor signaling pathways such as TGF-β are important driving forces for the occurrence and development of ESCC. Our results provide new insights into the pathogenesis of ESCC, and seven RBPs have potential application value in the clinical prognosis prediction of ESCC.
Mariia S. Bogacheva, Riina Harjumäki, Emilia Flander, Ara Taalas, Margarita A. Bystriakova, Marjo Yliperttula, , Alan W. Leung,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.726499

Abstract:
The generation of human stem cell-derived spheroids and organoids represents a major step in solving numerous medical, pharmacological, and biological challenges. Due to the advantages of three-dimensional (3D) cell culture systems and the diverse applications of human pluripotent stem cell (iPSC)-derived definitive endoderm (DE), we studied the influence of spheroid size and 3D cell culture systems on spheroid morphology and the effectiveness of DE differentiation as assessed by quantitative PCR (qPCR), flow cytometry, immunofluorescence, and computational modeling. Among the tested hydrogel-based 3D systems, we found that basement membrane extract (BME) hydrogel could not retain spheroid morphology due to dominant cell–matrix interactions. On the other hand, we found that nanofibrillar cellulose (NFC) hydrogel could maintain spheroid morphology but impeded growth factor diffusion, thereby negatively affecting cell differentiation. In contrast, suspension culture provided sufficient mass transfer and was demonstrated by protein expression assays, morphological analyses, and mathematical modeling to be superior to the hydrogel-based systems. In addition, we found that spheroid size was reversely correlated with the effectiveness of DE formation. However, spheroids of insufficient sizes failed to retain 3D morphology during differentiation in all the studied culture conditions. We hereby demonstrate how the properties of a chosen biomaterial influence the differentiation process and the importance of spheroid size control for successful human iPSC differentiation. Our study provides critical parametric information for the generation of human DE-derived, tissue-specific organoids in future studies.
Sophie Sluysmans, Isabelle Méan, Lionel Jond,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.729444

Abstract:
PLEKHA5, PLEKHA6, and PLEKHA7 (WW-PLEKHAs) are members of the PLEKHA family of proteins that interact with PDZD11 through their tandem WW domains. WW-PLEKHAs contribute to the trafficking and retention of transmembrane proteins, including nectins, Tspan33, and the copper pump ATP7A, at cell-cell junctions and lateral membranes. However, the structural basis for the distinct subcellular localizations of PLEKHA5, PLEKHA6, and PLEKHA7 is not clear. Here we expressed mutant and chimeric proteins of WW-PLEKHAs in cultured cells to clarify the role of their structural domains in their localization. We found that the WW-mediated interaction between PLEKHA5 and PDZD11 is required for their respective association with cytoplasmic microtubules. The PH domain of PLEKHA5 is required for its localization along the lateral plasma membrane and promotes the lateral localization of PLEKHA7 in a chimeric molecule. Although the PH domain of PLEKHA7 is not required for its localization at the adherens junctions (AJ), it promotes a AJ localization of chimeric proteins. The C-terminal region of PLEKHA6 and PLEKHA7 and the coiled-coil region of PLEKHA7 promote their localization at AJ of epithelial cells. These observations indicate that the localizations of WW-PLEKHAs at specific subcellular sites, where they recruit PDZD11, are the result of multiple cooperative protein-lipid and protein-protein interactions and provide a rational basis for the identification of additional proteins involved in trafficking and sorting of WW-PLEKHAs.
, Jeanette A. M. Maier
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.733573

Abstract:
Mechanical cues contribute to the maintenance of a healthy endothelium, which is essential for vascular integrity. Indeed endothelial cells are mechanosensors that integrate the forces in the form of biochemical signals. The cytoskeleton is fundamental in sensing mechanical stimuli and activating specific signaling pathways. Because the cytoskeleton is very rapidly remodeled in endothelial cells exposed to microgravity, we investigated whether the disruption of actin polymerization by cytochalasin D in 1g condition triggers and orchestrates responses similar to those occurring in micro- and macro-vascular endothelial cells upon gravitational unloading. We focused our attention on the effect of simulated microgravity on stress proteins and transient receptor potential melastatin 7 (TRPM7), a cation channel that acts as a mechanosensor and modulates endothelial cell proliferation and stress response. Simulated microgravity downregulates TRPM7 in both cell types. However, 24 h of treatment with cytochalasin D decreases the amounts of TRPM7 only in macrovascular endothelial cells, suggesting that the regulation and the role of TRPM7 in microvascular cells are more complex than expected. The 24 h culture in the presence of cytochalasin D mimics the effect of simulated microgravity in modulating stress response in micro- and macro-vascular endothelial cells. We conclude that cytoskeletal disruption might mediate some effects of microgravity in endothelial cells.
Mridu Malik, Yang Yang, Parinaz Fathi, Gretchen J. Mahler,
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.721338

Abstract:
Identification and approval of new drugs for use in patients requires extensive preclinical studies and clinical trials. Preclinical studies rely on in vitro experiments and animal models of human diseases. The transferability of drug toxicity and efficacy estimates to humans from animal models is being called into question. Subsequent clinical studies often reveal lower than expected efficacy and higher drug toxicity in humans than that seen in animal models. Microphysiological systems (MPS), sometimes called organ or human-on-chip models, present a potential alternative to animal-based models used for drug toxicity screening. This review discusses multi-organ MPS that can be used to model diseases and test the efficacy and safety of drug candidates. The translation of an in vivo environment to an in vitro system requires physiologically relevant organ scaling, vascular dimensions, and appropriate flow rates. Even small changes in those parameters can alter the outcome of experiments conducted with MPS. With many MPS devices being developed, we have outlined some established standards for designing MPS devices and described techniques to validate the devices. A physiologically realistic mimic of the human body can help determine the dose response and toxicity effects of a new drug candidate with higher predictive power.
Yan Li, Wei Li, Andrew R. Hoffman, Jiuwei Cui, Ji-Fan Hu
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.699621

Abstract:
Mitophagy is a specialized autophagic pathway responsible for the selective removal of damaged or dysfunctional mitochondria by targeting them to the autophagosome in order to maintain mitochondria quality. The role of mitophagy in tumorigenesis has been conflicting, with the process both supporting tumor cell survival and promoting cell death. Cancer cells may utilize the mitophagy pathway to augment their metabolic requirements and resistance to cell death, thereby leading to increased cell proliferation and invasiveness. This review highlights major regulatory pathways of mitophagy involved in cancer. In particular, we summarize recent progress regarding how nuclear-encoded long non-coding RNAs (lncRNAs) function as novel epigenetic players in the mitochondria of cancer cells, affecting the malignant behavior of tumors by regulating mitophagy. Finally, we discuss the potential application of regulating mitophagy as a new target for cancer therapy.
Ran Wei, Jichuan Quan, Shuofeng Li, Hengchang Liu, Xu Guan, Zheng Jiang, Xishan Wang
Frontiers in Cell and Developmental Biology, Volume 9; https://doi.org/10.3389/fcell.2021.724860

Abstract:
Background: Cancer stem cells (CSCs), which are characterized by self-renewal and plasticity, are highly correlated with tumor metastasis and drug resistance. To fully understand the role of CSCs in colorectal cancer (CRC), we evaluated the stemness traits and prognostic value of stemness-related genes in CRC. Methods: In this study, the data from 616 CRC patients from The Cancer Genome Atlas (TCGA) were assessed and subtyped based on the mRNA expression-based stemness index (mRNAsi). The correlations of cancer stemness with the immune microenvironment, tumor mutational burden (TMB), and N6-methyladenosine (m6A) RNA methylation regulators were analyzed. Weighted gene co-expression network analysis (WGCNA) was performed to identify the crucial stemness-related genes and modules. Furthermore, a prognostic expression signature was constructed using the Lasso-penalized Cox regression analysis. The signature was validated via multiplex immunofluorescence staining of tissue samples in an independent cohort of 48 CRC patients. Results: This study suggests that high-mRNAsi scores are associated with poor overall survival in stage IV CRC patients. Moreover, the levels of TMB and m6A RNA methylation regulators were positively correlated with mRNAsi scores, and low-mRNAsi scores were characterized by increased immune activity in CRC. The analysis identified 34 key genes as candidate prognosis biomarkers. Finally, a three-gene prognostic signature (PARPBP, KNSTRN, and KIF2C) was explored together with specific clinical features to construct a nomogram, which was successfully validated in an external cohort. Conclusion: There is a unique correlation between CSCs and the prognosis of CRC patients, and the novel biomarkers related to cell stemness could accurately predict the clinical outcomes of these patients.
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