Regeneration of uterine epithelium after experimental ablation in the rat

Regeneration of the uterine luminal epithelium was studied after its mechanical removal in progesterone-primed rats, leaving one control horn intact. Pulse labelling with [3H]TdR during regeneration, showed a rapid peak of labelling index in remaining glands. A differentiated and highly labelled luminal epithelium reappeared at 34 hr, thereafter showing a rapidly declining LI. After initial depletion, the glandular cell population size was restored within 64 hr, whereas luminal epithelium cell numbers became stabilized at about half normal level. Grain counts after prelabelling showed more rapid dilution in gland cells of stripped uterine horns, indicating accelerated cycling of previously dividing cells. Thymidine labelling indices also showed that, after removal of the epithelium, almost all gland cells became rapidly committed to divide. On average, less than two cell cycles were necessary to restore stable glandular and epithelial population sizes. Numbers of labelled cells were also drastically increased in myometrium and serosa of treated horns. This suggests a non-specific mechanism for stimulation of mitotic activity after ablation of epithelium.