Aquaporins in bovine sperm: Promising target for male reproductive strategy

The search for new indicators for assessing the quality of cryopreserved semen is necessary to reduce the number of ineffective insemination procedures in cattle. Aquaporins (AQPs) are small transmembrane proteins that facilitate the transport of water and other small solutes across the membrane. In this study we identified and localized AQP3, AQP7, AQP8 and AQP11 in frozen-thawed bull spermatozoa and investigated the relationship between their expression and specific semen quality parameters, as well as the concentrations of free amino acids (AA), biogenic amines (BA), and the composition of fatty acids (FA) in spermatozoa and seminal plasma. The collected cryopreserved semen samples were classified into two groups: high (H) and low (L) sperm motility. The analysis showed that the percentage of spermatozoa with intense AQP3 staining in the midpiece, and diffuse AQP7 staining in the post-acrosomal region and midpiece, was significantly higher in the H group. Furthermore, AQP3, AQP7 and AQP8 expression showed positive correlations with multiple semen quality parameters and concentrations of selected AA and FA. The results indicate that the analysis of aquaporin distribution in spermatozoa, particularly AQP3 and AQP7, may serve as a useful parameter for assessing the quality of cryopreserved semen in future studies. Detailed analysis of their location and expression allowed for the determination of the potential role of these proteins in the osmoadaptation process to the hypertonic environment of the uterus and fallopian tubes.