Effect of the intrauterine contraceptive device on the regeneration of rabbit endometrium

Haemostasis in menstrual endometrium in the presence of an intrauterine device

The histology and ultrastructure of the haemostatic response in the endometrium have been studied in 12 uteri containing an inert or copper wound intrauterine contraceptive device (IUCD). The uteri were removed during the premenstrual phase or during the first 96 hours of menstruation. The results have been compared to earlier observations in non-IUCD influenced endometrium. In all uteri the tissue shedding proceeded more slowly in the presence of an IUCD and considerably fewer haemostatic plugs were found. The platelets in these plugs were more loosely packed and less degranulated, and the plugs contained less fibrin than in the absence of an IUCD. Haemostatic plugs were still observed at times when no such plugs were seen in uteri without an IUCD. Unoccluded vessel lesions were regularly seen and vessels open to the shedding surface were occasionally encountered. These observations suggest that IUCD-induced menorrhagia is caused by the combination of delayed shedding and a decreased haemostatic reaction in the endometrium.

Studies on the cytodynamics of human endometrial regeneration. III. In vitro short-term incubation historadioautography

The proliferation kinetics of endometrial regeneration were assessed by tracing nucleoprotein precursor, radiothymidine. Increased isotope uptake occurred by cycle day 3 and was confined to the gland cells of denuded stratum basale (basal layer) and persistent uterine lining, bordering peripheral areas of denudation. This increase resulted in the formation of flattened surface epithelial cells, which initially were devoid of significant deoxyribonucleic acid synthesis. Such alterations are consistent with changes in cells involved in ameboid migration. Maturation of migrating cells was accompanied by a significant rise in labeling indices and replication at cycle days 3 and 4. By cycle day 5, endometrial repair was complete. The findings indicate that, following physiologic loss of stratum functionale, endometrial healing involves both migration and replication of surface cells, which originate from the gland stumps of the residual basal layer and the persistent surface epithelium adjacent to the periphery of denuded endometrium.

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.

Studies on the cytodynamics of human endometrial regeneration. II. Transmission electron microscopy and histochemistry

The morphologic observations made in this study indicate that postmenstrual endometrial resurfacing occurs by proliferation of epithelial cells originating from the stumps of residual basal glands and uterine surface lining, bordering the denuded areas, respectively. Endometrial stromal cells or glands of the residual spongiosa are not involved in uterine surface repair. The mechanism whereby the new surface develops, it is proposed, is by endomitotic division. This contention is supported by the accelerated nuclear DNA and intracytoplasmic RNA synthesis, and absence of mitosis in the newly formed surface epithelial cells. The results indicate, furthermore, that uterine surface reconstruction, which is completed by cycle day 5, is independent of ovarian hormonal stimuli, whereas further endometrial growth, connective tissue remodeling, and metabolic enzyme synthesis are influenced by the gradual increase of preovulatory estrogens.

Studies on the cytodynamics of human endometrial regeneration. I. Scanning electron microscopy

Stereoscopic morphologic studies on regenerating cyclic endometrium indicate that endometrial repair lasts 48 hours, beginning between cycle Days 2 to 3 and ending between cycle Days 4 to 5. During this period, endometrial repair is focused on the neoformation of surface epithelium and is initiated only when and where the zona basalis is denuded from the overlying secretory spongiosa. The surface epithelium is derived from a simultaneous proliferation of dual origin: first from the exposed ends of basal glands and second from the persistent and intact surface lining of cornual and isthmic regions, bordering the denuded areas. The lack of estrogen-dependent morphologic alterations (mitosis and ciliogenesis) in the uterine mucosa during the regenerative period suggests that the initial factors and cellular processes operating in endometrial reconstruction are purely a reflection of tissue repair and are independent of cyclic hormonal stimuli.