A comparison of the proliferative capacity and ultrastructure of proliferative cells from the cochleae of newborn rats of different ages

Abstract

Objective Recent reports have shown that multipotent stem cells/progenitor cells that are capable of proliferation and regeneration are present in mammalian cochleae. However, progenitor cells have not been isolated from the adult cochlea. We examined the proliferative potential of cells derived from neonatal rats of various ages. The determination of the differences between the proliferative cells from rats of different ages may provide clues to the mechanisms controlling the destiny of these cells. Methods Proliferative cells were isolated from the cochleae of 1-, 7-, and 14-day-old rats, and the proliferative capacity and ultrastructure of the cells from each age group were assessed using flow cytometry and transmission electron microscopy, respectively. Results During the first two postnatal weeks, the number of proliferative cells gradually fell to zero. This decrease occurred in parallel with the impairment of the proliferative capacity of the cells and the accumulation of proliferative cells in G0/G1. In addition, some of the cells exited the cell cycle by means of gradual maturity and apoptosis. Conclusions Our study suggests that cochlear proliferative cells are remnants of the progenitor cells that originally gave rise to the sensory epithelium. The disappearance of the cochlear proliferative cells in adult mammalian cochleae may result from their differentiation and/or apoptosis.