Platelet-Rich Plasma Proteome of Mares Susceptible to Persistent-Breeding-Induced Endometritis Differs from Resistant Mares

Persistent-breeding-induced endometritis (PBIE) is the leading cause of subfertility and poor reproductive efficiency in mares. Platelet-rich plasma (PRP) treatment has been shown to mitigate PBIE, reduce uterine infections, and improve fertility in mares. However, the proteome of PRP in mares, particularly those susceptible to PBIE, remains unknown. This study aimed to fill this knowledge gap by comparing the most abundant proteins present in PRP prepared from mares with histories of being susceptible or resistant to PBIE. The study involved twelve light-breed mares: seven susceptible and five resistant to PBIE. A complete blood count and physical examination were performed on each mare before blood drawing to ensure good health. The PRP was prepared following collection in a blood transfusion bag and double centrifugation. Platelet counts in the PRP were compared across the groups. The PRP was cryopreserved in liquid nitrogen until proteomics could be completed. Physical parameters and complete blood cell counts were within normal ranges. The platelet counts for resistant (561 ± 152 × 103) and susceptible mares (768 ± 395 × 103) differed (p < 0.05). One hundred and five proteins were detected in all mares, and four proteins were more abundant in resistant mares (p < 0.05). The proteins were apolipoprotein C-II, serpin family G member 1, protection of telomeres protein 1, and non-specific serine/threonine protein kinase. All these proteins are linked to the immune response. These results suggest that PRP prepared from mares resistant to PBIE may be more beneficial in mitigating PBIE in mares, offering a promising avenue for improving equine reproductive health. However, this remains to be determined with in vivo studies.