Impact of the corpus luteum on survival of the developing embryo and early pregnancy in mares.

The research article discusses the crucial role of the corpus luteum, a temporary endocrine structure in female mammals, in the early stages of pregnancy in horses. It particularly focuses on its impact on the survival of the developing embryo and the establishment of pregnancy.

Study of Ovaries and Corpora Lutea

• The research article begins by noting past studies that highlight the necessity of ovaries and corpora lutea (a type of body tissue) for the survival of the embryo and the establishment of pregnancy.

Importance of Luteal Progesterone in Pregnancy

• For horses, luteal progesterone, a hormone produced by the corpus luteum, is critical only during the first trimester of pregnancy. This support is observed to be quite complex compared to other domestic animals.

Role of eCG on Luteal Function

• The function of the ovarian luteal is further enhanced by the luteinizing hormone (LH) effect of the equine chorionic gonadotropin (eCG), beginning roughly around the 35th day of pregnancy. This leads to an increased secretion of eCG, thus leading to the formation of additional corpora lutea, increasing the concentration of blood progesterone.

Progesterone-Driven Embryo-Maternal Interactions

• The researchers also explore the physiological mechanisms of progesterone-driven embryo-maternal interactions. Investigation into the transcriptomes and secretomes of uterine tubes, the endometrium and early embryo have provided more information about the cellular and molecular events that enable the embryo’s survival and endometrium remodelling before the formation of a functioning placenta.

Effects of Progesterone-Deprived Environment

• Aluteal pregnancy models have demonstrated that early embryo development can occur even in a progesterone-deprived environment. However, the lack of progesterone leads to dysregulation of vital pregnancy-related genes. Embryo development is compromised unless progestin supplementation is provided once the embryo reaches the uterus.

Luteal Support is Essential for Embryo Survival

• While our understanding of embryo-maternal interactions continues to grow, it remains clear that luteal support is essential for the survival of the embryo, primarily after it reaches the uterus. Luteal support influences gene expression, facilitating appropriate physiological interactions between the embryo and the mother and allowing the formation of a fully competent placenta thus, increasing the chances of giving birth to a live foal at full term.