Immunohistochemical analysis of proliferating cells in a sterile labyrinthitis animal model.

Inflammatory reactions within the cochlea lead to the formation of fibrotic tissue and bone. To determine which cells are involved in the proliferation of the inflammatory response within the cochlea, sterile labyrinthitis was created by inoculating keyhole limpet hemocyanin (KLH) into the scala tympani of systemically sensitized animals. Cellular proliferation was assessed immunohistochemically using the monoclonal antibody Ki-67. Proliferating cells were identified among inflammatory cells and fibroblasts within the matrix, as well as in endosteal cells lining the scala tympani. Inflammatory and potential osteoprogenitor cells were labeled as late as 6 weeks after inoculation, suggesting the absence of a strong immunosuppressive mechanism. Endosteal cells may proliferate and secrete the extracellular matrix used by the inflammatory cells to move within the cochlear scalae. They may also participate in the ossification of the inflammatory matrix.