Expression of Caspase Family in the Endometrium during the Estrous Cycle and Pregnancy in Pigs

다국어 초록 (Multilingual Abstract)

Caspases are a family of protease enzymes that play an essential role in apoptosis. Caspases can be subdivided to two groups. One is initiator caspases which include caspase 8 (CASP8), caspase 9 (CASP9) and caspase 10 (CASP10), and the other is executioner caspases which include caspase 3 (CASP3), caspase 6 (CASP6) and caspase 7 (CASP7). Once activated by death signaling proteins, initiator caspases cleave and activate downstream executioner caspases, which in turn execute apoptosis by cleaving targeted critical cellular proteins. In many studies, the caspase family is involved in cell proliferation and apoptosis and the expression of caspases is regulated by steroid hormones in the endometrium during the estrous cycle and pregnancy in mammals. However, the expression and function of caspases have not been determined in the porcine endometrium. Thus, to initiate the study on the role of caspases in the endometrium, we characterized the expression of caspases in the endometrium during the estrous cycle and pregnancy in pigs. We obtained endometrial tissue samples from glits on day (D) 12 and D15 of the estrous cycle and from D12, D15, D30, D60, D90 and D114 of pregnancy. Real-time RT-PCR analysis showed that the expression of CASP3, CASP6, CASP7, CASP8, CASP9 and CASP10 mRNAs was detected in the endometrium during the estrous cycle and pregnancy. Especially, levels of CASP3 mRNA were higher on D12 of pregnancy than the estrous cycle. To investigate the effects of steroid hormones, estrogen and progesterone, on expression of caspase, endometrial tissue explants from immature pigs were treated with steroid hormones. Increasing doses of progesterone, CASP7 mRNA increased but, decreased CASP8 and CASP10 mRNAs. In addition, increasing doses of IL1B upregulated the expression of CASP3 mRNA in the endometrium. Furthermore, immunohistochemistry analysis showed that CASP3 protein was localized to the luminal and glandular epithelial cells in the endometrium during the estrous cycle and pregnancy. These results indicate that caspases are expressed in the endometrium during the estrous cycle and pregnancy in a stage-depedent manner, and the expression of some caspase in the endometrium is regulated by steroid hormone or cytokine. Further analysis of localization and functions of caspase families at endometrium are needed.