Equine endometrial development during late fetal and postnatal periods.

The research addresses the development process of the horse’s uterine tissue, focusing on the endometrial histogenesis, which begins before birth and continues after birth. This study, carried out on 38 horse fetuses and newborns from gestation day 300 to postnatal day 180, shows that equine endometrial histogenesis is characterized by an early appearance of uterine glands and a substantial increase in epithelial proliferation during the first 24 postnatal weeks.

Research Methodology and Sample

• The authors collected uterine tissues from 38 foals with developmental ages between gestation day 300 and postnatal day 180.
• After acquiring the samples, they conducted an assessment of endometrial histogenesis, which is the process of tissue formation.

Evaluation of Cell Proliferation

• The research team examined patterns of cell proliferation within the endometrium (uterine lining).
• They used multispectral imaging to evaluate tissue sections that had been stained immunofluorescently for Ki-67, a cellular marker for proliferation.
• The researchers then calculated the Labeling index (LI), the percentage of cells expressing Ki-67, for each compartment of the endometrial cell, including luminal epithelium, glandular epithelium, and stroma (connective tissue).

Findings

• Analysis revealed that endometrial glands were notably present in all examined pre- and postnatal uterine tissues.
• It was found that Ki-67 LI significantly increased from the prenatal to postnatal periods, indicating a rise in cell proliferation during this period.
• The LI was higher in the epithelium compared to the stroma, revealing more cell division activity in this area.
• In the postnatal period, the endometrial Ki-67 LI significantly increased from week 1 to week 24, showing a major surge in cell division after birth.

Conclusion

• The results of this study contradict the previously understood patterns of uterine development in ungulates (hoofed mammals) where neonatal uterine development was reported to begin postnatally.
• The findings confirm that endometrial histogenesis in horses starts prenatally, with evidence of uterine glands as early as GD 300.
• Moreover, the research highlights a significant increase in epithelial proliferation, which is associated with the maturation of the equine endometrium, by postnatal week 24.