Progesterone and conceptus-derived factors important for conceptus survival and growth

Progesterone (P4) from the corpus luteum (CL) is critical for the establishment and maintenance of pregnancy and plays a major role in regulating endometrial secretions essential for stimulating and mediating changes in conceptus growth and differentiation throughout early pregnancy in ruminants. Numerous studies have demonstrated an association between elevated P4 and acceleration in conceptus elongation. A combination of in vivo and in vitro experiments found that the effects of P4 on conceptus elongation are indirect and mediated through P4- induced effects in the endometrium. Despite effects on elongation, data on the impact of post-insemination supplementation of P4 on pregnancy rates are conflicting and typically only result in a modest improvement, if any, in fertility. Differences in conceptus length on the same day of gestation would suggest that factors intrinsic to the blastocysts transferred regulate development, at least in part, and would be consistent with the hypothesis that the quality of the oocyte regulates developmental competence. This paper will review recent knowledge on the effect of P4 on conceptus development in cattle and summarize strategies that have been undertaken to manipulate post fertilization P4 concentrations to increase fertility.

Progesterone and conceptus-derived factors important for conceptus survival and growth

Progesterone (P4) from the corpus luteum (CL) is critical for the establishment and maintenance of pregnancy and plays a major role in regulating endometrial secretions essential for stimulating and mediating changes in conceptus growth and differentiation throughout early pregnancy in ruminants. Numerous studies have demonstrated an association between elevated P4 and acceleration in conceptus elongation. A combination of in vivo and in vitro experiments found that the effects of P4 on conceptus elongation are indirect and mediated through P4- induced effects in the endometrium. Despite effects on elongation, data on the impact of post-insemination supplementation of P4 on pregnancy rates are conflicting and typically only result in a modest improvement, if any, in fertility. Differences in conceptus length on the same day of gestation would suggest that factors intrinsic to the blastocysts transferred regulate development, at least in part, and would be consistent with the hypothesis that the quality of the oocyte regulates developmental competence. This paper will review recent knowledge on the effect of P4 on conceptus development in cattle and summarize strategies that have been undertaken to manipulate post fertilization P4 concentrations to increase fertility.(AU)

Biological roles of progesterone, prostaglandins, and interferon tau in endometrial function and conceptus elongation in ruminants

A large majority of pregnancy loss in cattle occus during the firt three weeks afeer conception particularly during the pperi-implantation period. This review integrantes established and new information on the biological role of ovarian progesterone (P4), prostaglandina (PGs) and interferon tau (IFNT) in endometrial function and conceptus elongation during the peri-implantation period of pregnancy in ruminants. Progesterone is secreted by the ovarian corpus luteum (CL) and is the u nequivocal hormone of pregnancy. Prostaglandins are produced from both the endometrium as well as conceptus trophectoderm during early pregnancy. Interferon tau is produced solely by the conceptus trophectoderm and is the maternal recognition of pregnancy signal that inhibits production of luteolytic pulses of PG F2α by the endometrium to maintain the CL and thus production of P4. Conceptus endometrial interactions in ruminants are complex and involve carefully orchestrated temporal and spatial alterations in endometrial gene expression during pregnancy. Available results support the idea that the individual, interactive, and coordinated actions of P4, PGs, and IFNT regulate uterine receptivity to conceptus implantation by controlling expression of genes in t he endometrium and that their actions are essential for conceptus elongation. One outcome of gene expression changes in the endometrial epithelia is alterations in lumenal secretions that govern conceptus elongation via effects on the trophectoderm. An increased knowledge of conceptus endometrial interactions during early pregnancy in ruminants is necessary to understand and elucidate the causes of infertility and recurrent pregnancy loss and to provide a basis for new strategies to improve fertility, pregnancy outcomes and thus reproductive efficiency.

Biological roles of progesterone, prostaglandins, and interferon tau in endometrial function and conceptus elongation in ruminants

A large majority of pregnancy loss in cattle occus during the firt three weeks afeer conception particularly during the pperi-implantation period. This review integrantes established and new information on the biological role of ovarian progesterone (P4), prostaglandina (PGs) and interferon tau (IFNT) in endometrial function and conceptus elongation during the peri-implantation period of pregnancy in ruminants. Progesterone is secreted by the ovarian corpus luteum (CL) and is the u nequivocal hormone of pregnancy. Prostaglandins are produced from both the endometrium as well as conceptus trophectoderm during early pregnancy. Interferon tau is produced solely by the conceptus trophectoderm and is the maternal recognition of pregnancy signal that inhibits production of luteolytic pulses of PG F2α by the endometrium to maintain the CL and thus production of P4. Conceptus endometrial interactions in ruminants are complex and involve carefully orchestrated temporal and spatial alterations in endometrial gene expression during pregnancy. Available results support the idea that the individual, interactive, and coordinated actions of P4, PGs, and IFNT regulate uterine receptivity to conceptus implantation by controlling expression of genes in t he endometrium and that their actions are essential for conceptus elongation. One outcome of gene expression changes in the endometrial epithelia is alterations in lumenal secretions that govern conceptus elongation via effects on the trophectoderm. An increased knowledge of conceptus endometrial interactions during early pregnancy in ruminants is necessary to understand and elucidate the causes of infertility and recurrent pregnancy loss and to provide a basis for new strategies to improve fertility, pregnancy outcomes and thus reproductive efficiency.(AU)