Immunolocalization of a novel protein (P19) in the endometrium of fertile and subfertile mares.

This research article examines the distribution of a new protein (P19) within the endometrium of fertile and infertile mares, both in healthy individuals and those with endometrosis. The protein could have transport roles in pregnancy and could potentially be linked to lower fertility rates observed in older mares suffering from endometrosis.

Objective of the Research

• The main objective of this study was to reveal the presence and distribution of a new protein, P19, in the endometrium of mares. This protein is produced by the endometrial glands and is observable in uterine secretions during certain periods of the oestrous cycle and at the beginning of pregnancy.
• Since the functioning of P19 was unknown, the study aimed to determine a potential role for this protein. The researchers made an educated guess that P19 could act as a transporter for a maternal factor to the fetus, given that most similar proteins (lipocalins) fulfill such a role.

Methodology

• The researchers developed a high-titre antiserum against this protein, enabling them to identify its presence via immunohistochemistry in endometrial biopsies. They collected these biopsies from healthy mares and mares with endometrosis – a disease that can cause subfertility or infertility.

Findings and Interpretation

• The results showed that P19 was undetectable in prepubertal fillies and in mares in anoestrus, and it was barely noticeable in mares in oestrus. However, significant amounts of P19 was found during dioestrus and very early pregnancy, and moderate levels after the 20th day of gestation.
• In six mares with endometrosis who were subfertile, an abnormal pattern of protein detection was found at all reproductive stages, particularly in the ‘gland nests’. Those exhibited either the absence of P19 or an accumulation of the protein, suggesting an irregular glandular activity.
• The researchers concluded that abnormal secretion of P19 could be one of the causes of reduced fertility rates in older mares with endometrosis. The study therefore identified a high proportion of abnormal, asynchronous endometrial glands in the group of subfertile mares tested.