Some aspects of endometrial cup formation and PMSG production.

The research investigates the formation of endometrial cups and the production of PMSG (Pregnant mare’s serum gonadotropin) in horse twins. It offers support for the idea that these cups are created by the fetus and are eventually destroyed through immune mechanisms.

Study Overview

• The study was conducted on two female horses that were part of a set of chimeric twins, meaning each pair of twins was fertilized with the other’s semen.
• These two mares were closely observed during their gestational period in order to monitor PMSG production. In this case, one mare conceived four offspring, while the other gave birth to two.

Main Findings

• Observations revealed high levels of PMSG in both mares, with this hormone being detectable even towards the end (220 days and 265 days respectively) of their gestational periods.
• The fetal membranes of one mare were found to contain remnants of cup secretion that held PMSG activity even at full term.

Conclusion and Significance

• The observations and findings from this study provide support for the theory proposed by Allen and Moor in 1972. This theory suggests that endometrial cups, a structure that forms in the uterus of pregnant horses, are created by the fetus itself.
• The presence of PMSG in the peripheral blood until the later stages of gestation and the remnants of cups in the fetal membrane at term provide evidence supporting this theory.
• Furthermore, the study also suggests that these endometrial cups are later destroyed through immunological processes, possibly as a bodily attempt to return to pre-pregnant conditions in preparation for future pregnancies.