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.