Characterization of normal human brain cultures. Evidence for the outgrowth of leptomeningeal cells.

To establish the histogenetic identity of the predominant cell type in monolayer cultures of normal human adult brain, eight brain specimens were placed into culture and characterized according to cell kinetics, karyotype, antigenic expression, and ultrastructural features. The protein profiles of both the cell layer and the medium were analyzed in selected cultures using sodium dodecyl sulfate polyacrylamide gel electrophoresis and diethylaminoethyl cellulose chromatography. All cultures displayed a limited life span in vitro; marked contact inhibition at confluence; a normal karyotype; an intracytoplasmic and extracellular glycoprotein profile consisting of fibronectin, procollagen type III, laminin, and collagen type IV; specialized intercellular junctions; and interstitial collagen chain synthesis. All of these features were identified in our previous study of human leptomeningeal cultures. The results of immunocytochemical staining for glial fibrillary acidic protein were negative in all cultures of normal human brain, except in early passages in two cultures, which lost the glial cell marker during subsequent passages; immunostains for vimentin were positive in all cells in all cultures. These results support the hypothesis that, in this study, cultures derived from normal human brain are not of glial origin. Our findings also suggest that glial cells are less well-suited to monolayer growth under our culture conditions than are other cell types in enzyme-dissociated brain tissue placed in culture, especially leptomeningeal cells. The identification of leptomeningeal cells as the predominant cell type in normal human brain cultures may prove useful in attempts to foster the growth of human glial cells by culturing brain samples under conditions that prohibit the growth of leptomeningeal cells. Under such conditions, astrocytes, oligodendroglia, and ependymal cells could be isolated with greater ease and cultured separately. These purified cultures of different glial cell types would then provide a more relevant in vitro model for studying human neurological diseases.