Endometrial expression of antimicrobial peptides as markers of subclinical endometritis in mares

Abstract

AbstractBackgroundEndometritis is a major cause of subfertility in mares. Multiparous old mares are more susceptible to developing endometritis given that ageing is associated with an altered immune response and with inadequate physiological uterine clearance after breeding, which can lead to degenerative changes in the endometrium. Molecules such as antimicrobial peptides (AMPs) have been proposed as endometritis markers in the equine species.Study designCross‐sectional.ObjectivesTo investigate the endometrial expression of defensin‐beta 4B (DEFB4B), lysozyme (LYZ) and secretory leukocyte peptidase inhibitor (SLPI) genes in mares either affected or not by subclinical endometritis, due to the role of these AMPs in the immune response to bacteria and inflammatory reactions.MethodsEndometrial biopsy for histopathological and gene expression examinations was performed on 26 mares. The inclusion criteria for the normal mare group (NM, N = 7) were 2–4 years of age, maiden status, no clinical signs of endometritis and a uterine biopsy score of I, while for mares affected by subclinical endometritis (EM, N = 19) the inclusion criteria were 10–22 years of age, barren status for 1–3 years, no clinical signs of endometritis and a uterine biopsy score between IIA and III.ResultsA significantly higher expression of LYZ (NM: 0.76 [1.84–0.37] vs. EM: 2.78 [5.53–1.44], p = 0.0255) and DEFB4B (NM: 0.06 [0.11–0.01] vs. EM: 0.15 [0.99–0.08], p = 0.0457) genes was found in endometritis mares versus normal mares. Statistically significant moderate positive correlations were found between the level of expression of LYZ gene and both the age (r = 0.4071, p = 0.039) and the biopsy grade (r = 0.4831, p = 0.0124) of the mares.Main limitationsThe study investigated a limited number of genes and mares, and the presence/location of the proteins coded by these genes was not confirmed within the endometrium by IHC.ConclusionsIf the results of this study are confirmed, LYZ and DEFB4B genes can be used as markers to identify mares that are affected by subclinical endometritis.