Establishment and characterization of rat progenitor hair cell lines

Cochlear progenitor hair cell lines are useful for studies of cellular specification, gene expression features, and signal transduction involved in the development of hair cells. To obtain embryonic and postnatal cochlear progenitor hair cell lines, we immortalized primary cultures of sensorineural epithelial cells from otocysts on embryonic day 12 (E12) and explants of the organ of Corti tissues on postnatal day 5 (P5). Primary cultures and explants were then transduced by the E6/E7 genes of human papilloma virus type 16. Transduced cells were passed for >50 passages and partial clonal cells were isolated from the above P5 organ of Corti explants by limiting dilution. The expression of neuronal, neural, epithelial, hair cell markers, and important transcription factors were then examined in these cell clones. Clones that express the above markers were considered as being progenitor hair cells. At least two representative cell lines, one from a mixed culture of otocyst epithelial cells and the other from the organ of Corti cells, ultimately expressed hair cell markers and neuronal/neural cell markers. The former only expressed the early hair cell marker oncomodulin and myosin VIIa, whereas the latter expressed oncomodulin, calretinin, myosin VIIa and Brn 3.1. These cell lines may represent progenitor hair cells at the different stages of cochlear development.