[Epidermal stem cells in the tympanic membrane].

OBJECTIVE: To investigate the distributions of epithelial stem cells in the tympanic membrane and the growth characteristics of cultured epithelial cells from different region of tympanic membrane, and to establish culture techniques of stem cells in tympanic membrane.
METHODS: Four young rats and four adult SD rats were used to observe normal tympanic membrane. The other 28 rats were performed 2 mm size perforations in pars tensa. These animals were sacrificed at different periods after perforation. The tympanic membranes were cut in cryostat sections for immunohistochemistry of cytokeratin 19 and integrin beta1. Thirty tympanic membranes of rats were treated with Mitomycin C to damage the mucosal surface, then divided into two parts: the annulus region and center region of pars tensa, cultured in medium with high amount of epidermal growth factor and low amount of calcium.
RESULTS: The immunostaining cells of cytokeratin 19 and integrin beta1 were displayed in both the handle of malleus and annular regions, but there were no staining positive cells in the intermediate region of pars tensa. The positive cells distribution had no significant difference between adult and infancy rats. In the pars flaccid, the positive cells scattered in the basal layer. The positive cells increased after perforation in the annulus and handle of malleus region, but no immunostaining cells were found at the edge of perforation. The redouble time of the culture cells from the annulus region was shorter than the center of pars tensa. The cells adherent within 1 hour formed larger and more colonies, and contained more positive cells.
CONCLUSION: The epithelial stem cells in tympanic membrane were located in both the handle of malleus and annular regions, but no stem cells could be found in the intermediate region of pars tensa. The stem cells of tympanic membrane can be simply purified according to the adherent time.