Human Disc Nucleus Properties and Vertebral Endplate Permeability
- 1 April 2011
- journal article
- research article
- Published by Ovid Technologies (Wolters Kluwer Health) in Spine
- Vol. 36 (7), 512-520
- https://doi.org/10.1097/brs.0b013e3181f72b94
Abstract
Study Design. Experimental quantification of relationships between vertebral endplate morphology, permeability, disc cell density, glycosaminoglycan (GAG) content, and degeneration in samples harvested from human cadaveric spines. Objective. To test the hypothesis that variation in endplate permeability and porosity contributes to changes in intervertebral disc cell density and overall degeneration. Summary of Background Data. Cells within the intervertebral disc are dependent on diffusive exchange with capillaries in the adjacent vertebral bone. Previous findings suggest that blocked routes of transport negatively affect disc quality, yet there are no quantitative relationships between human vertebral endplate permeability, porosity, cell density, and disc degeneration. Such relationships would be valuable for clarifying degeneration risk factors and patient features that may impede efforts at disc tissue engineering. Methods. Fifty-one motion segments were harvested from 13 frozen cadaveric human lumbar spines (32–85 years) and classified for degeneration using the magnetic resonance imaging-based Pfirrmann scale. A cylindrical core was harvested from the center of each motion segment that included vertebral bony and cartilage endplates along with adjacent nucleus tissue. The endplate mobility, a type of permeability, was measured directly using a custom-made permeameter before and after the cartilage endplate was removed. Cell density within the nucleus tissue was estimated using the picogreen method, while the nuclear GAG content was quantified using the dimethylmethylene blue technique. Specimens were imaged at 8μm resolution using microCT; bony porosity was calculated. Analysis of variance, linear regression, and multiple comparison tests were used to analyze the data. Results. Nucleus cell density increased as the disc height decreased (R2 = 0.13; P = 0.01) but was not related to subchondral bone porosity (P > 0.5), total mobility (P > 0.4), or age (P > 0.2). When controlling for disc height, however, a significant, negative effect of age on cell density was observed (P = 0.03). In addition to this, GAG content decreased with age nonlinearly (R2 = 0.83, P < 0.0001) and a cell function measurement, GAGs/cell, decreased with degeneration (R2 = 0.24; P < 0.0001). Total mobility (R2 = 0.14; P < 0.01) and porosity (R2 = 0.1, P < 0.01) had a positive correlation with age. Conclusion. Although cell density increased with degeneration, cell function indicated that GAGs/cell decreased. Because permeability and porosity increase with age and degeneration, this implies that cell dysfunction, rather than physical barriers to transport, accelerates disc disease.Keywords
This publication has 66 references indexed in Scilit:
- Cell transplantation in lumbar spine disc degeneration diseaseEuropean Spine Journal, 2008
- Biological repair of the degenerated intervertebral disc by the injection of growth factorsEuropean Spine Journal, 2008
- Tissue engineering and the intervertebral disc: the challengesEuropean Spine Journal, 2008
- A Local Adaptive Threshold Strategy for High Resolution Peripheral Quantitative Computed Tomography of Trabecular BoneAnnals of Biomedical Engineering, 2007
- Degeneration of intervertebral discs due to smoking: experimental assessment in a rat-smoking modelJournal of Orthopaedic Science, 2004
- Classification of Age-Related Changes in Lumbar Intervertebral DiscsSpine, 2002
- Direction‐dependent resistance to flow in the endplate of the intervertebral disc: an ex vivo studyJournal of Orthopaedic Research, 2001
- The Anisotropic Hydraulic Permeability of Human Lumbar Anulus FibrosusSpine, 1999
- Effects of low oxygen concentrations and metabolic inhibitors on proteoglycan and protein synthesis rates in the intervertebral discJournal of Orthopaedic Research, 1999
- In Vitro Diffusion of DYE Through the End-Plates and the Annulus Fibrosus of Human Lumbar Inter-Vertebral DiscsActa Orthopaedica, 1970