Characterization of marginal and Claudius' cells growing from cochlear explants in vitro.

Tissue specimens of stria vascularis together with spiral ligament were transferred from the guinea pig cochlea to tissue culture dishes. To characterize and identify cells growing out from the explants, indirect immunofluorescence microscopy was used. The expression of the intermediate-sized filaments vimentin and cytokeratin 18 in cells on the surface of tissue specimens and in cells growing out from the explants after different cultivation periods were compared. Basically, three types of cells grew from the explants during several days: marginal cells, Claudius' cells and fibroblast-like cells. In primary cultures of explants, growth of marginal cells was observed in 25% of the dishes. Their proliferative activity, estimated by the use of the BrdUrd-DNA antibody, started in the stria vascularis and continued across the attachment of Reissner's membrane down to the bottom of the cell culture dish. The newly-formed marginal cells expressed cytokeratin 18 in the same way that original marginal cells on the tissue specimen do. If the newly-formed marginal cells were in contact with fibroblast-like cells or were forming groups (domes) on the bottom, they expressed vimentin. In 3% of the dishes growth of Claudius' cells was observed. Proliferative activity of these cells was found at the point where the basilar membrane was attached to the spiral ligament. New Claudius' cells spread at the opposite side of an explant when compared with the location of new marginal cells. Original as well as newly-formed Claudius' cells contained cytokeratin 18. Fibroblast-like cells were commonly present in cultures and contained only vimentin.