Intermediate Cells of Dual Embryonic Origin Follow a Basal to Apical Gradient of Ingression Into the Lateral Wall of the Cochlea.

Intermediate cells of the stria vascularis are neural crest derived melanocytes. They are essential for the establishment of the endocochlear potential in the inner ear, which allows mechanosensory hair cells to transduce sound into nerve impulses. Despite their importance for normal hearing, how these cells develop and migrate to their position in the lateral wall of the cochlea has not been studied. We find that as early as E10.5 some Schwann cell precursors in the VIIIth ganglion begin to express melanocyte specific markers while neural crest derived melanoblasts migrate into the otic vesicle. Intermediate cells of both melanoblast and Schwann cell precursor origin ingress into the lateral wall of the cochlea starting at around E15.5 following a basal to apical gradient during embryonic development, and continue to proliferate postnatally.

Congenital Deafness and Recent Advances Towards Restoring Hearing Loss.

Congenital hearing loss is the most common birth defect, estimated to affect 2-3 in every 1000 births. Currently there is no cure for hearing loss. Treatment options are limited to hearing aids for mild and moderate cases, and cochlear implants for severe and profound hearing loss. Here we provide a literature overview of the environmental and genetic causes of congenital hearing loss, common animal models and methods used for hearing research, as well as recent advances towards developing therapies to treat congenital deafness. © 2021 The Authors.

Transcriptomic analysis and ednrb expression in cochlear intermediate cells reveal developmental differences between inner ear and skin melanocytes.

In the inner ear, the neural crest gives rise to the glia of the VIII ganglion and two types of melanocytic cells: The pigmented cells of the vestibular system and intermediate cells of the stria vascularis. We analyzed the transcriptome of neonatal intermediate cells in an effort to better understand the development of the stria vascularis. We found that the expression of endothelin receptor B, which is essential for melanocyte development, persists in intermediate cells long after birth. In contrast, skin melanocytes rapidly downregulate the expression of EdnrB. Our findings suggest that endothelins might have co-opted new functions in the inner ear during evolution of the auditory organ.