Incidence and morphology of endometrial angiopathies in mares in relationship to age and parity.

This research paper discusses how, in mares, the morphology of uterine blood vessels changes with age and reproductive status, ultimately leading to pregnancy-induced pathologies and infertility.

Research Methodology

• The researchers analyzed the structure of endometrial blood vessels in the uterus of mares using light and electron microscopy, involving 117 and 13 samples respectively. In addition, the study used elastase digestion to examine 86 samples.
• The mares included in this study represented a range of ages and reproductive statuses for more comprehensive results.

Key Findings

• Vascular changes related to inflammation were observed in approximately 20.5% of the specimens.
• Arterial and venous blood vessels, both small and large, showed mild to severe degenerative lesions. Healthy blood vessels were only found in maiden (unbred) mares.
• Older, maiden mares often presented angiosclerotic changes, marked by mild to moderate sclerosis surrounding the blood vessels and within the inner lining of the blood vessels (intima).
• The occurrence and intensity of these vascular changes increased with age and the number of past pregnancies.
• The vascular changes found in mares that had multiple pregnancies resembled “pregnancy-sclerosis”, seen in other species. This condition presents with damage to the internal elastic lamina, atrophy of the middle layer of the blood vessels, sclerosis and fibrosis, and calcification within the blodd vessel walls.

Implications and Conclusions

• Minutely observing the arteries in mares post-parturition revealed notable changes, like damage to the internal elastic lamina, activation of smooth muscle cells, and emerging elastic fibres in the intima and inner media. These observations suggested a potential pregnancy-induced origin for these pathologies.
• The authors theorized that the changes in blood flow and hormones during and after pregnancy might cause active remodelling in the blood vessels.
• Cyclical processes of blood vessel expansion during pregnancy and subsequent shrinking post-partum could lead to progressive degeneration, particularly in mares that have given birth multiple times.
• Additional factors contributing to these degenerative changes include the natural aging process, chronic inflammation, and short intervals between foal births.
• Severe angiosis was often associated with phlebectasia and lymphangiectasia. These conditions may indicate a decreased capacity of the blood vessels to adjust to the varying demands of uterine blood flow, leading to decreased perfusion and lymph drainage in the uterus.
• These changes in the blood vessels of older, multiparous mares could also directly contribute to infertility.