The reliability of various mitotic index systems assessing mitotic activity in stratified squamous epithelium.

Abstract

At various times within a 24 hour period 26 while albino rats aged from 3 to 15 months received an intraperitoneal injection of colchicine (1 mg/kg body weight) and were sacrificed 31/2 hours later. Serial sections were prepared for the palate, tongue, gingiva and ear and were stained with hematoxylin and eosin. The mitotic activity was assessed for the epithelium of these tissues using three different mitotic index systems (mitoses/1 mm2 surface area; mitoses/1000 cells; mitoses/1 mm basement membrane). For the same tissues in another 10 rats the number of nucleated epithelial cells and the length of the basement membrane were related to a reference unit of the epithelial surface. The coefficients of variation for these observations were calculated. The application of the traditional indices (mitoses per 1000 cells or 1 mm of the basement membrane) introduced an appreciable variability into the measurements and produced misleading results when the mitotic activity of various epithelia were compared. The index system expressing the number of mitoses relative to a reference unit (1 mm2) of the outer surface of the epithelium was found to be the most reliable method for assessing mitotic activity in stratified squamous epithelium.