Tissue-specific levels and cellular distribution of epidermal growth factor receptors within control and neomycin-damaged neonatal rat organ of corti

Epidermal growth factor receptor (EGFR) levels were assayed by an enzyme-li nked immunosorbent assay (ELISA) in microdissected organ of Corti (OC) from neonatal rats directly after isolation and after 3 days in culture with an d without neomycin treatment. In addition, the cellular distribution of the EGFR in the OC was determined by immunohistochemistry, The in vitro level of EGFR determined by ELISA assays doubled after neomycin damage to OC, sug gesting that EGFR is subject to up-regulation following this treatment. Imm unohistochemistry of both in vivo and in vitro controls indicates that EGFR is predominantly localized in the stereociliary bundles of the hair cells; supporting cells and the apical junctions between the remaining Kolliker o rgan cells were also immunolabeled, In neomycin-treated cultures, sensory c ells were degenerated, so no labeling could be seen. However, supporting an d Kolliker organ cells continued to show labeling. In addition, nerve fiber s in the region of the future osseous spiral lamina and projecting out towa rd the damaged sensory epithelium were immunostained, The up-regulation of the EGFR and its redistribution within the OC following neomycin damage sup port the earlier observation that growth factors that act through EGFR, suc h as EGF and transforming growth factor-a can induce neonatal mammalian aud itory hair cell replacement under culture conditions, after aminoglycoside treatment. (C) 1999 John Wiley & Sons, Inc.