Influence of seminal plasma on leucocyte migration and amount of COX-2 protein in the jenny endometrium after insemination with frozen-thawed semen

After mating, seminal plasma has an immuno-modulatory effect on the endometrium in some mammals. In jennies, achieving conception via artificial insemination (AI) with frozen-thawed semen is generally much more difficult than in mares. The endometrial inflammatory response is hypothesized to be a contributing factor to the lesser fertility. Following a cross-over experimental design, the uterine inflammatory response of six jennies was evaluated at 6 h after AI with frozen-thawed semen (deposited in the uterine body) in the presence or absence of autologous seminal plasma (+SP or −SP). The endometrial cytology and histology of the animals were examined by uterine lavage, uterine swabbing and biopsy. The amount of cyclooxygenase-2 (COX-2) protein in endometrial cells was also evaluated. As a control (C), the same examinations were made before any AI procedure (i.e., when the jennies were in oestrus). Large numbers of polymorphonuclear neutrophils (PMN) were observed in the −SP and +SP cytology and biopsy samples; more than in the C samples. The −SP samples also had intense COX-2 labelling; less labelling was detected in the +SP and C samples (no significant difference between these latter two types). Thus, while the presence of SP does not change the post-AI number of PMNs with regard to that detected in its absence, it does reduce COX-2 protein. Further research into the complex mix of molecules in SP and its effects during AI might help increase the pregnancy rates achieved in jennies.