Proliferative potential of endometrial stromal cells, and endometrial and placental expression of cyclin in the bovine.

The objective of the present investigation was to study proliferative activity of fibroblast-like endometrial stromal cells in bovine endometrial caruncular (CAR) and intercaruncular (ICAR) areas that have distinct functions during implantation. Endometrial stromal cells were derived from CAR and ICAR of nonpregnant cows, and their proliferative potential was analyzed in an in vitro cell culture system. In addition, expression of four types of cell cycle regulatory molecules was analyzed by RT-PCR in samples of CAR, ICAR, cotyledon (COT) and fetal membrane of both artificially inseminated (AI) and somatic nuclear transferred (NT) cows on days 30 and 60 of gestation. The proliferation growth curve showed that the cells derived from CAR had higher proliferative activity than that of ICAR-derived cells. No morphological differences were found between the cells derived from CAR and ICAR at population-doubling levels (PDL) of the two. Most of the cells derived from ICAR of nonpregnant cows exhibited expanded shape with no further proliferation at PDL 6 with a lack of cyclin E expression. Of the regulatory molecules, cyclin D1, CDK2 and CDK4 were expressed in both CAR and ICAR cells derived from both nonpregnant, and AI cows on days 30 and 60 of gestation. The expression of cyclin E in both AI and NT cows was confined to COT and fetal membrane on day 30 of gestation. Cyclin E expression on day 60 of gestation in AI cows was observed in all but ICAR areas. In marked contrast, however, cyclin E expression on day 60 of gestation in NT cows was confined to COT, suggesting that poor placentation in these cows is possibly associated with a lack of cyclin E expression. These results suggest that CAR-derived stromal cells have higher proliferative potential, which may be related to cyclin E expression during implantation.