Changes in aquaporins mRNA expression and liquid storage at 17°C: A potential biomarker of boar sperm quality?

Artificial insemination (AI) for pigs relies on liquid storage of extended semen at 17°C, which preserves sperm quality and ensures its fertilizing capacity. Routine quality controls include the evaluation of sperm motility, viability and capacitation status. The physiological functions of all these features depend on transmembrane aquaporins (AQPs), proteins playing key roles in osmoadaptation. In this study, we made a relative quantification, using RT-qPCR, of the mRNA of several sperm AQPs in AI-liquid semen doses before and after a 48-hr incubation period, aiming to determine possible quantitative compromising expression changes during the process that could serve as a diagnostic tool. Our results showed a decrease in classical sperm motility variables (total and progressive motility and velocity) and sperm viability after 48-hr storage, whereas capacitation status increased overtime. mRNA expression increased in the orthodox AQP4 and AQP6 after 48-hr incubation, relative to control (0 hr) and 24-hr time-points. Moreover, mRNA expression of aquaglyceroporins AQP3, AQP7 and AQP10 was higher after 48-hr incubation, confirmed by AQP7-protein validation using Western blot. Our results indicate that expression levels of AQPs-mRNA can change in ejaculated pig spermatozoa under conditions of ex-vivo incubation that could modify sperm homeostasis, suggesting it could eventually become a relevant molecular biomarker to assess the efficiency of liquid storage of pig semen.