Alterations of Circulating Biomarkers During Late Term Pregnancy Complications in the Horse Part II: Steroid Hormones and Alpha-Fetoprotein.

The study highlights the changes in levels of progestogen, estrogen, and alpha-fetoprotein (AFP) in the blood of thoroughbred mares dealing with various pregnancy complications, including preterm labor, and different types of placentitis. The research also presents the first recorded alterations in steroid hormones and AFP amidst focal mucoid placentitis, a specific pregnancy complication in horses.

Objectives of the Study

• The primary aim of the research was to understand the fluctuations in certain biomarkers – specifically, steroid hormones (progestogens and estrogens) and fetal proteins (alpha-fetoprotein; AFP) – during complications in late term pregnancies in horses.
• The researchers also aimed to evaluate if these biomarkers could help improve diagnosis of abnormal pregnancies in horses.

Methodology

• The study examined a large sample size of 702 thoroughbred mares which were bled weekly, from December 2013 until they deliver or went through abortion.
• After childbirth or abortion, their fetal membranes underwent histopathological examination and were classified based on the type of disease: ascending placentitis, focal mucoid placentitis, idiopathic abortion or no disease.
• Serum samples from the mares were analyzed on a weekly basis for their concentrations of progesterone, estradiol-17β, and AFP.
• This was done retrospectively from the week of parturition/abortion and the preceding four weeks.

Key Findings

• The study found significant increase in progesterone and AFP in the cases of both ascending placentitis and focal mucoid placentitis. There was also a significant drop in estradiol-17β and the ratio of estradiol-17β to progesterone when compared to normal pregnancies.
• Interestingly, the research discovered that idiopathic abortions were marked by a decrease in progesterone concentration accompanied by an increase in AFP, but these changes were observed only in the week before parturition or abortion.
• Fundamentally, this research shows that spontaneous placental infection in horses caused alterations in both endocrine and feto-secretory markers in the mother’s blood circulation, but only minor changes ensued when the abortion was non-infectious idiopathic.

Significant Contribution

• The research is significant because it is the first study that reports changes in steroid hormones and AFP during the progression of focal mucoid placentitis, a disease that involves Nocardioform placentitis.
• This deeper understanding of changes in biomarkers during pregnancy complications could potentially lead to better diagnostic mechanisms for abnormal pregnancies in horses.