Endometrial gland surface density and hyperaemia of the endometrium during early pregnancy in the mare.

The article focuses on studying changes in the morphology and surface density of endometrial glands during the initial 30 days of gestation in mares. The research showed that there were no significant differences noticed on day 12 after ovulation, but on day 16, glands beneath the conceptus were notably less dense. Between days 20 and 30, the endometrium directly in contact with the conceptus started appearing redder and significantly more hyperaemic, indicating that further investigations are needed to understand the components secreted by the endometrial glands during early pregnancies.

Objective of the Study

• The primary goal of this research was to examine the modifications in the morphology and surface density of the endometrial glands located near and far from the conceptus during the initial 30 days of gestation.

Methodology

• Endometrial biopsies were obtained from both nonpregnant and pregnant mares 12 days after ovulation and pregnant mares on Days 16, 20, 25, and 30 of gestation.
• Computer-assisted morphometric analysis was used to evaluate the biopsied samples, specifically focusing on the surface area per unit volume (Sv) of the endometrial glands in the stratum spongiosum.
• One biopsy was taken each at the base of the nonpregnant uterine horn and from beneath the conceptus at the base of the gravid horn.

Results

• On Day 12 post-ovulation, there were no discernable differences in morphology or density of the glands between the pregnant and nonpregnant mares.
• On Day 16, the glands beneath the conceptus were significantly less dense than the glands at the base of the nonpregnant horn.
• Between Days 20 to 30 of gestation, the endometrium in direct contact with the conceptus was visibly more reddened and hyperaemic than other parts of the uterus.
• By this stage, the Sv of glands beneath the conceptus had increased again, making them appear similar to those in the nonpregnant horn. This was mainly due to a reduction in stromal oedema in the former.

Conclusions

• During early pregnancy, embryo-maternal interactions critical for suppressing the cyclical luteolytic cascade and supporting the nidation of the conceptus were observed. They were characterized by endometrial hyperaemia, histotroph production, and a decrease in endometrial gland Sv at the beginning of the stationary phase.
• The study concluded that both the components secreted by the endometrial glands and the factors liberated by the conceptus during early pregnancy warrant further investigation.