| dc.description | Integrins are involved in reproductive processes such as uterine receptivity and embryo attachment. At the fetal-maternal interface integrins are involved cell attachment and communication. In cattle, the uterine distribution of integrin alphavbeta3 is different between cycling and pregnant animals. The hypothesis of this research was that integrin alphavbeta3 may be involved in the events surrounding embryo implantation. Because its expression is regulated during the estrous cycle and pregnancy it may be controlled by estrogen receptor (ER) or progesterone receptor (PR) signaling, or by local substances produced by the uterus or embryo. The objectives were to: (1) characterize the expression of ER and PR in the uterus during the estrous cycle and pregnancy, (2) identify factors that regulate integrin alphavbeta 3 expression, and relate this information to the local uterine environment at luteolysis and embryo attachment and (3) compare expression patterns of integrin alphavbeta3 and its ligand osteopontin in the uteri of sheep and cattle. Results and discussion. The pattern of ER distribution was consistent with the hypothesis that cycle termination is initiated by estrogen binding its receptor; estrogen is a known stimulant for synthesis of the luteolysin, PGF2alpha. Uterine infusion of the pregnancy recognition protein, interferon-tau, or an anti-estrogen blocked ER expression. Therefore in pregnancy interferon-tau may prevent luteolysis by blocking ER action. Interferon-tau did not affect integrin alpha vbeta3. Treatment of cultured uterine cells with estrogen inhibited expression of integrin alphavbeta3 while prostaglandins stimulated expression. Based on these results it appears that estrogen downregulates integrin alphavbeta3 on day 16 of the cycle, which may promote differentiation of the epithelium into the prostaglandin secreting phenotype. If interferon-tau increases the luteoprotective substance prostaglandin E2, this may sustain integrin alpha vbeta3 expression during pregnancy. Integrin alpha vbeta3 and osteopontin were not co-expressed at the fetal maternal-interface. Therefore in ruminants integrin alphavbeta 3 and osteopontin are not essential for attachment, but may function in the signaling pathways initiated at luteolysis and maternal recognition of pregnancy. | en_US |
