Aquaporins in reproductive system: New markers for male (in)fertility in cattle?

Abstract

Improving reproductive methods and searching for new solutions is one of the challenges of modern animal breeding. Among the new potential indicators that may allow precise determination of male reproductive potential and elimination of low-fertility males are aquaporins located in the reproductive system (AQPs) [1, 2]. In mammals, of the 13 known AQPs (AQP0-AQP12), as many as 11 were found in the male reproductive organs. AQPs located in sperm are of particular interest in the context of assessing semen quality parameters. According to some authors, their expression may play an important role in the “journey” of sperm in the female reproductive tract and effective fertilisation. Despite the wide range of possibilities related to the measurement of AQPs, little is still known in this respect in farm animals, including cattle. Hence, research was undertaken, the main goals of which were to identify and analyse changes in the expression of all potentially occurring AQPs in the reproductive tract with the growth and development of animals, as well as to identify AQPs in sperm and search for the relationship between their expression and selected semen quality parameters. As a result of the conducted research, the bull will be the first male in which a comprehensive assessment of the occurrence of all known AQPs in the male reproductive system was made. To date, as many as 12 aquaporins, apart from AQP2, have been found in cattle. The age-related changes in the expression and/or distribution patterns of particular AQPs indicate the involvement of these proteins in the normal development and course of male reproductive processes in cattle. The presence of individual AQPs was observed throughout the entire male reproductive system, starting from gonocytes in the youngest animals, through Leydig and Sertoli cells, germ cells in seminiferous tubules, basal and principal cells of epididymis, and ending with vas deferens. Assessment of selected sperm parameters of cryopreserved semen and changes in the expression of individual AQPs indicates that they may be related to its quality.