IMMUNOHISTOCHEMICAL LOCALIZATION OF BASEMENT-MEMBRANE COLLAGENS AND ASSOCIATED PROTEINS IN THE MURINE COCHLEA

Immunohistochemistry using antibodies specific for each of the basemen t membrane collagen chains was used to assess the location and composi tion of basement membranes in the mouse cochlea. The classical chains (COL4A1, 4A2) localized primarily in the osseous spiral lamina and in the capillaries of the spiral ligament. In contrast, the novel collage n chains (4A3, 4A4, and 4A5) localized to the interdental cells of the sulcus, the inner sulcus, the basilar membrane, and the region of typ e II fibrocytes in the spiral ligament. Antibodies against type 4A5 co llagen also heavily stained the stria vascularis. Weak staining in the stria was observed with antibodies against 4A3. Basement membrane-ass ociated proteins were also assessed. The basement membrane in the peri neurium of the osseous spiral lamina immunostained using antibodies ag ainst laminin, heparan sulfate proteoglycan, and entactin. The basilar membrane contained only fibronectin in association with the novel col lagen chains. The capillaries of the spiral ligament and the stria vas cularis stained heavily for heparin sulfate proteoglycan and laminin. Generalized staining for laminin was observed in the spiral ligament. These results indicate that an abundance of basement membrane collagen containing extracellular matrix exists in the murine cochlea and that the composition of these matrices are surprisingly varied and tissue specific.