Origin and histogenesis of equine endometrial cups.

This research paper investigates the origin and development of endometrial cups in horses. The study found that a specific region of the equine trophoblast, known as the chorionic girdle, is responsible for the high production of gonadotrophin hormone – which is vital in equine pregnancy.

Methodology

• The researchers carried out biochemical and morphological studies to determine the origin and histogenesis of endometrial cups in mares.
• A wide range of fetal and maternal tissues were cultured in vitro to monitor their capability to secrete gonadotrophin – a hormone necessary for maintaining pregnancy in mares, also known as Pregnant Mare’s Serum Gonadotrophin (PMSG).

Findings

• The research found that a specific area of the equine trophoblast – an embryonic component of placenta – produces high levels of PMSG. This area is called the chorionic girdle and is a band of highly specialized cells.
• The chorionic girdle is found at the junction of the allantois and the regressing yolk sac. The allantois is a fetal membrane involved in nutrition and excretion, and the yolk sac is an early source of nutrition for the embryo.
• Furthermore, the shape of the girdle cells after cultivation in vitro and after allogeneic grafting to the uterus or testis was found to be identical to that of endometrial cup cells. Allogeneic grafting here refers to the transplantation of cells from a donor of the same species but with a different genotype.

Development of Endometrial Cups

• The firm union between the cells of the chorionic girdle and the adjacent endometrium (the lining of the uterus) takes place on the 36th day of pregnancy.
• After this union, the girdle cells quickly invade and consume the endometrial epithelium. They then migrate to the endometrial glands and the uterine stroma (the connective tissue of the uterus) where they then differentiate into large, immotile endometrial cup cells.
• The process highlights the journey of cellular development within the equine uterus, displaying the transformation of the chorionic girdle cells into endometrial cup cells.