Caspase-3-mediated apoptosis and cell proliferation in the equine endometrium during the oestrous cycle.

Cell proliferation and apoptosis are hormone-dependent physiological processes involved in endometrial growth and regression. The aims of the present study were: (1) to evaluate endometrial cell proliferation using proliferating cell nuclear antigen (PCNA) expression; (2) to evaluate the induction of endometrial cell death by the expression of active caspase-3 and the apoptotic phenotype visualised by DNA fragmentation; and (3) to relate these observations to endometrial tissue dynamics in the equine endometrium throughout the oestrous cycle. Endometria were assigned to follicular and luteal phases based on ovarian structures and plasma progesterone. Cell proliferation and active caspase-3-mediated apoptosis were expressed in both phases of the oestrous cycle. In the luteal phase, PCNA expression was higher than in the follicular phase. Highest PCNA activity was noted in the luminal and glandular structures. Active caspase-3 staining was increased in luminal epithelium and deep glandular cells during the luteal phase. However, in the follicular phase, stromal cells showed greater active caspase-3 expression. Only a few apoptotic endometrial cells were detected by terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) and these cells were mostly present in luminal and glandular structures. A simultaneous increase in DNA, cell proliferation and protein synthesis was observed in the endometrium during the mid-luteal phase. This suggests that cell hyperplasia occurs at the time the histotroph is needed for eventual embryo nourishment.

Microvascular development and growth of uterine tissue during the estrous cycle in mares.

OBJECTIVE: To document uterine growth and microvascular development in the endometrium of uteri with differing degrees of fibrosis as well as uterine growth throughout the estrous cycle of mares. ANIMALS: 30 mares. PROCEDURE: Uterine tissue was obtained during the breeding season from a slaughter facility. Stage of estrous cycle of the mares was assessed on the basis of ovarian structures and plasma progesterone concentrations. Endometrium was characterized by use of light microscopy, and blood vessel walls were marked by histochemical techniques. Microvascular development was evaluated by a computerized image analysis system. Growth of uterine tissue was based on cellular content of DNA and RNA, RNA:DNA, and protein:DNA. RESULTS: Significant differences in vascular density were not observed in the endometrium of uteri obtained from mares euthanatized during the follicular or luteal phase of the estrous cycle, regardless of whether endometrial classification of degree of fibrosis was considered. There was a 3-fold increase in amount of DNA and RNA of endometrial cells in the follicular phase when compared to myometrium. Hypertrophy of endometrial tissue during the luteal phase was reflected by a significant increase in cell protein content and protein:DNA. CONCLUSIONS AND CLINICAL RELEVANCE: Endometrial growth of vascular tissues during the estrous cycle may be coordinated with development of nonvascular tissue. Estrogen and progesterone may play a role in regulation of uterine growth and angiogenesis.