Reliability of histopathological examination and immunohistochemistry of a single biopsy for evaluation of endometrial health in Icelandic mares

Introduction. Endometritis and endometrosis have been and still are the major reasons for infertility in mares. The diagnosis of endometritis can be based on cytology and microbiology, but endometrial biopsy is still the only way to diagnose endometrosis in the mare. Our study attempted to determine if a single biopsy using his­topathology and immunohistochemistry is sufficient to ascertain reasons for infertility in Icelandic mares. The objectives of this study were to examine the relationship between deviations in endometrial biopsies in terms of prostaglandin-endoperoxide synthase-2 (PTGS-2) and fibronectin expression and polymorphonuclear cells (PMNs) infiltration, as well as scoring degeneration in two endometrial biopsies. Material and methods. Materials were collected from 53 Icelandic breed mares, from whom two endometrial biopsies were collected and they were used for histopathology and for immunohistochemistry for PTGS-2 and fibronectin. Results. In our study, twenty-six of 53 mares (49%) showed differences in the biopsy score between the left and the right uterine horns (p = 0.002). There were statistically significant differences in fibronectin expression (p = 0.001), as well as in PTGS-2 expression in the superficial epithelium (p = 0.017). Conclusions. Significant differences in the biopsy score, and fibronectin and PTGS-2 expression, between two endometrial biopsies obtained from individual mares demonstrated that a single biopsy could be insufficient for diagnosing uterine health status in Icelandic mares.