Evaluation of inflammatory infiltrates in the endometrium of the jenny (Equus asinus)

Abstract

Introduction: Endometrial immune cell infiltration and its biological significance has not yet been investigated in the jenny. In other species, resident immune cells contribute to homoeostasis and female fertility. However, chronic inflammation leads to endometrosis, a major cause of subfertility and infertility in mares, represented by irreversible and progressive fibrosis, glandular and vascular changes. So far, endometrial biopsies of jennies are evaluated using Kenney and Doig’s classification for mares. Materials and Methods: Twenty endometrial biopsies of jennies aged between 4 and 20 years were classified according to Kenney and Doig into four categories (I, IIA, IIB and III) using haematoxylin and eosin (HE) stained sections. The Masson-trichrome (MT) stain served for the assessment of connective tissue and immunohistochemistry to detect macrophages (MACA874GA, Bio-Rad) and T cells (polyclonal rabbit anti-CD3, Dako). Five microscopic fields (40x magnification) were assessed for eosinophil (HE), macrophage and T cell (immunohistochemistry) infiltrates, and for collagen (MT), using the ImageJ® software. Statistical analysis was performed with SPSS software (Pearson correlation). Results: A significant statistical association was found between the collagen area and Kenney and Doig’s classification (p=0.017). No correlations were found between each type of inflammatory cells and Kenney and Doig’s classification, or between the different types of inflammatory cells. Conclusions: In contrast to mares, jennies exhibited inflammatory infiltrates in all endometrial categories; hence, Kenney and Doig’s classification for endometrial biopsies needs adjustment for the jenny. Future studies are required to unravel the influence of endometrial inflammatory cell infiltrates and collagen on the fertility of jennies.