Post-Artificial Insemination Endometrial Inflammation and Its Control in Donkeys

Donkey frozen semen shows good spermatozoa (spz) survival results; however, fertility results are very bad in jennies. Donkey frozen semen is able to penetrate oocytes in vitro and to fertilize mares. Jennies express a high endometrial inflammatory response 6 hours after artificial insemination (AI) with frozen semen. High amount of polymorphonuclear neutrophils (PMNs) in cytologic smears and biopsies, and intense cyclooxygenase-2 (COX-2) immunohistochemical labeling was detected. In vivo and in vitro experiences showed that seminal plasma (SP), eliminated during semen freezing process, has an important role in modulating this response. Seminal plasma reduces the PMN-spz binding in vitro. Moreover, SP decreases COX-2 expression and eosinophils and neutrophils migration in vivo. In vitro, PMN-spz incubation showed that SP is able to activate PMNs and preserves sperm survival and motility. After 3-4 hours of incubation, the main part of spz attached to PMNs was alive, and several attached spz set free had good motility parameters when assessed by CASA system. Fractioning SP attending proteins molecular weight (MW), we observed that low MW fractions (3-10 kDa) induced a rapid spz death; however, fractions between 30 and 100 kDa showed an interesting maintenance of survival and motility as well as a control of reactive oxygen species (ROS) production. Moreover, donkey SP has melatonin and donkey spz have melatonin receptors. Spermatozoa produce ROS, but PMNs produce much more. Therefore, in understanding the role of SP fractions on sperm survival and the antioxidant effect of SP, melatonin and other antioxidant SP compounds are very important to increase donkey frozen semen AI results.