Astrocyte cultures from human embryonic brain: Characterization and modulation of surface molecules by inflammatory cytokines

Abstract

Astrocyte‐enriched cultures were established upon passaging of primary cultures from the myelencephalon and mesencephalon of 7–9‐week‐old human embryos. Immunocytochemical analysis showed that third‐fourth passage cultures were composed of a highly enriched population of proliferating, epithelioid cells, up to 90% of which expressed glial fibrillary acidic protein (GFAP); no macrophages and very few fibroblasts (>2%) were present. GFAP expression and proliferation declined upon further culturing in serum‐containing medium but could be transiently reinduced by growing the cells in a serum‐free chemically defined medium. Large numbers of GFAP⁺ astrocytes were obtained from each embryo and could be stored frozen and recultured. Using flow cytometric analysis, human astrocyte cultures were examined for basal and cytokine [interferon‐γ (IFN‐γ), interleukin‐1β (IL‐1β), and tumor necrosis factor‐α (TNF‐α)]‐induced expression of molecules that may be involved in astrocyte‐T‐lymphocyte interactions. Cultured human astrocytes spontaneously expressed major histocompatibility complex (MHC) class I antigens and variable levels of MHC class II; MHC class I levels were increased upon IFN‐γ and TNF‐α treatment, whereas MHC class II antigens were induced on most of the astrocytes by IFN‐γ. Among the molecules involved in antigen‐independent interactions between T lymphocytes and target cells, lymphocyte function‐associated molecule‐3 (LFA‐3) was spontaneously expressed by most cultured human astrocytes, whereas intercellular adhesion molecule‐1 (ICAM‐1) was present at variable levels in non‐stimulated astrocytes and was greatly induced by IFN‐γ, TNF‐α, and IL‐1β. In this study we also show that the above cytokines upregulate astroglial expression of adhesion molecules of the integrin family (VLA‐1, VLA‐2, and VLA‐6) that may be involved in astrocyte‐extracellular matrix interaction and play a role in the astrocyte reactive changes occurring at sites of brain injury and inflammation. The human astrocyte cultures developed here represent a useful in vitro model to further investigate mechanisms involved in bidirectional communication between central glia and cells of the immune system.