Expression of heregulin and ErbB/Her receptors in adult chinchilla cochlear and vestibular sensory epithelium

Immunolabeling of heregulin, a growth factor that enhances cell proliferation in damaged utricles, and one of its binding receptors, ErbB-2, has been briefly described in the P3 rat cochlea and utricle [Zheng et al. (1999) J. Neurocytol. 28, 901-912]. However, little is known about the distribution of heregulin and its three binding receptors in adult animals. Here we describe the immunolabeling patterns for heregulin, ErbB-2, ErbB-3 and ErB-4 in the cochlea, spiral ganglion, utricle and saccule of the adult chinchilla using confocal microscopy. Heregulin immunolabeling was intense along the apical pole of Deiters cells and Hensen cells and along the membrane of supporting cells of the utricle and saccule; light immunolabeling was present in the outer layer of the spiral prominence and cytoplasm of spiral ganglion neurons. In the cochlea, intense to moderate ErbB-2 immunolabeling was evident in the cytoplasm of pillar cells, outer hair cells (OHCs), border cells, stria vascularis and spiral ligament; moderate ErbB-2 immunolabeling was present in the cytoplasm of the hair cell and supporting cell layers of the utricle and saccule. In the cochlea, light ErbB-3 immunolabeling was present in the inner hair cells, OHCs, marginal and intermediate cell layers of the stria vascularis and spiral ganglion neurons; moderate ErbB-3 immunolabeling was present in the cytoplasm of hair cells and supporting cells of the utricle and saccule. In the cochlea, utricle and saccule, ErbB-4 immunolabeling was intense in the nuclei and light to moderate in the cytoplasm and membrane of sensory cells and supporting cells. These results suggest that heregulin acting through ErbB receptors and various receptor complexes may play an important role in cell proliferation and survival in the cochlea and vestibular system.