Post-AI uterine lavage and PRP infusion reduce some uterine inflammation parameters but do not improve fertility in jennies inseminated with frozen semen

BACKGROUND: The use of cryopreserved semen in donkey jennies induces an exacerbated post-insemination uterine inflammatory response, resulting in low fertility rates. AIMS/OBJECTIVES: This study aimed to investigate the effects of different intrauterine therapies - seminal plasma infusion, platelet-rich plasma (PRP) infusion, uterine lavage, and uterine lavage combined with PRP infusion - on uterine inflammation and fertility in jennies inseminated with frozen donkey semen. METHODS: Twelve jennies were evaluated in two experimental phases. First, estrous cycles were assigned to control or treatment groups (UL: uterine lavage; PRP: platelet-rich plasma infusion; SP: seminal plasma infusion), and treatments were performed 4 h after AI. Uterine inflammation was assessed by ultrasonography, endometrial cytology, histopathology, collagen quantification, and COX-2 immunohistochemistry at T0 (before AI) and at 12, 24, and 48 h post-AI (T12, T24, and T48). Second, cycles were assigned to a control group or to uterine lavage followed by PRP infusion, and inflammatory parameters, progesterone levels, and pregnancy rates were evaluated. RESULTS: Neutrophil counts increased at 12 h post-insemination in all groups and decreased thereafter, remaining lower in UL and PRP groups than in the control group, but did not return to baseline within 48 h. Histopathology revealed eosinophilia at 48 h in all groups, with no differences among treatments. The combined treatment increased intrauterine fluid accumulation and uterine vascularization at T12 but did not change pregnancy rates (0% vs. 8.33%). CONCLUSION: Overall, uterine lavage and PRP infusion performed individually modulate the uterine inflammatory cellular response; however, the combined use of these therapies does not improve fertility in jennies inseminated with frozen donkey semen.