Studies on the cytodynamics of experimental endometrial regeneration in the rabbit. I. Historadioautography and ultrastructure.

The kinetic and fine structural characteristics and site of origin of the resurfacing uterine lining, as well as the influence of ovarian hormonal stimuli on the reparative processes of experimentally injured endometrium in the rabbit, were studied by means of in vivo historadioautography and electron microscopy. The first-generation, resurfacing spindle-shaped cells lacked mitosis and expanded by ameboid migration. This was followed by a rapid increase in nuclear deoxyribonucleic acid synthesis, which presumably provided for accelerated mitosis-mediated surface epithelial proliferation and maturation. By Day 3 after injury, endometrial regeneration was completed with a return of labeling index to base-line levels. The newly formed surface lining was derived exclusively from the persistent surface epithelium bordering the denuded regions. The isotope uptake and morphologic alterations of the regenerating endometrium in castrated rabbits which were similar to those of intact rabbits suggest that endometrial repair is not mediated by the hormones of the reproductive system.