Mitigation of post breeding endometritis in mares treated with platelet rich plasma

Abstract

Persistent breeding-induced endometritis (PBIE) is one of the major causes of infertility in mares, characterized by a lingering inflammatory response in the uterus, which leads to accumulation of uterine fluid and polymorphonuclear cells (PMN), harming the reproductive efficiency of the animal. The aim of this study was to determine if the presence and volume of intrauterine fluid and the percent of endometrial neutrophils decreased after intrauterine application of blood platelet-rich plasma (PRP) in mares with post-mating endometritis. Healthy estrous crossbreed mares (n = 9) aged between 6 to 12 years, with optimal body condition and under the same nutritional management, had two cycles randomly assigned to a crossover trial. Each received either intrauterine infusions of lactate ringer solution (LRS) or autologous PRP 4h after artificial insemination (AI) with fresh semen of low sperm quality from the same stallion. All the animals went through all the treatments. A total of 100 mL of citrated whole blood was collected for PRP production and was centrifuged at 2315g for 15 minutes then 579g for 10 minutes. The presence of intrauterine fluid (IUF) was analyzed by ultrasonographic examination and the percentage of endometrial neutrophils was determined through endometrial cytology, both before insemination (in the presence ofa preovulatory follicle ≥35mm and endometrial edema) and 24h after treatment application. Statistical analysis was performed by a Mixed model (SAS, 2023) for repeated measures with treatment and time as between subject factors. The presence of intrauterine fluid had an effect of time (p ≤ 0.049), where fluid size was smaller before AI than 24h after treatment; however, there was no treatment effect (p ≥ 0.264) over intrauterine fluid. The percentage of endometrial neutrophils had an effect of time (p ≤0.001), less inflammatory cells were found before AI than 24 hours after treatment; there was an effect of treatment (p ≤0.001) as well, where PRP decreased the number of endometrial polymorphonuclear cells compared to the control group infused with LRS. The increase in intrauterine fluid with time suggests that semen itself increases blood perfusion that generates intrauterine fluid accumulation. After induction of physiological endometritis, endometrial polymorphonuclear cell numbers were reduced successfully with PRP treatment. PRP is rich in peptides and signaling proteins that suppress the expression of proinflammatory cytokines such as IL-1 and TNF, inhibits polymorphonuclear neutrophil migration, and thus regulates intrauterine inflammation through decreased endometrial COX-2 expression.