Gerbilline cholesteatoma development Part III. Increased proliferation index of basal keratinocytes of the tympanic membrane and external ear canal.

Objective: To quantify the rate of basal cell division for keratinizing epithelium (KE) of the tympanic membrane (TM) and external ear canal (EAC) in spontaneous and induced gerbilline cholesteatomas.

Study Design And Setting: Cholesteatomas (3 spontaneous and 5 by induction) were labeled with tritiated thymidine for autoradiography and a KE proliferation index (PI) was determined. The PI was defined as the average number of labeled cells/mm overall and per anatomic region.

Results: For all regions combined, the PI was 27.3 in ears with cholesteatoma and 4.1 in normal ears (P < 0.0001). Additionally, there were significant regional differences in the PI in both normal ears and ears with cholesteatoma.

Conclusion: The KE of cholesteatomas in gerbils proliferates at approximately 7 times the rate measured in control ears.

Significance: Hyperproliferation of keratinocytes is a causative factor in the development and progression of spontaneous and experimental cholesteatomas in gerbils.