Using immunocytochemical methods, we localized several
glycoproteins of the extracellular matrix to leptomeningeal cells and
meningiomas in vitro. Three cell lines derived from normal human leptomeninges and seven from
meningiomas were studied by indirect immunofluorescence to evaluate the cellular production of
fibronectin,
laminin,
collagen type IV, and
procollagen type III. All leptomeningeal cell lines stained intensely and uniformly for all matrix
proteins; all
meningioma cell cultures stained uniformly, but the intensity of staining varied considerably. After removal of the cells in culture adherent to glass with 25 mM
ammonium hydroxide, indirect immunofluorescence demonstrated an exuberant residual extracellular residue enriched with
fibronectin,
laminin,
collagen type IV, and
procollagen type III. Electron microscopic examination of all leptomeningeal and
meningioma cultures revealed desmosomes and dense tonofilament formation; in addition, granular, filamentous basement membrane-like material was abundant in the extracellular spaces of all cultures.
Sodium dodecyl sulfate (SDS)-
polyacrylamide gel electrophoresis of the cell layer of two leptomeningeal and four
meningioma cultures showed production of interstitial
collagen types I and III; diethylaminoethyl (
DEAE)-cellulose chromatography of the medium demonstrated preferential production of
procollagen type I. Our findings show conclusively that normal arachnoid cells in vitro synthesize several of the
collagen subtypes and may be responsible for the "fibrous response" of the leptomeninges to
trauma,
infection, or infiltration by
tumor. The similarities between leptomeningeal cells and
meningiomas demonstrated by electron microscopy and by indirect immunofluorescence support the notion that
meningiomas are derived from arachnoid cells. The localization of various mesenchymal
glycoproteins within the intra- and extracellular spaces and the ubiquity of specialized intercellular junctions suggest that leptomeningeal cells in culture have the potential to behave like both stromal and epithelial cells.