Serial culture and characterization of the chinchilla middle ear epithelium.

We have successfully cultured a fibroblast-free chinchilla middle ear epithelium up to the 10th passage by using conditioned medium or using irradiated 3T3 cells as feeder cells. The cultured epithelial cells assumed a polygonal shape with a cobblestone appearance, indicating tight junction formation. A small number of the cells began to show abnormal morphology, such as indistinct cell boundaries, fibroid appearance, or giant cell formation, as the passage increased, particularly after the 5th passage. These morphologically transformed cells showed positive labeling with an anticytokeratin antibody, which indicated the epithelial origin of these cells. Neither ciliated nor secretory cells were observed in the serially cultured cells. The rate of cell growth slowed after the 7th passage, and after the 11th passage the cells no longer proliferated. Even with the above limitations, these cultured cells can be used for a number of in vitro experiments.