Localization of Aquaporin-7 in Human Testis and Ejaculated Sperm: Possible Involvement in Maintenance of Sperm Quality

Purpose: We have previously reported the expression of aquaporin-7 (AQP7) in the rat testis and cloned human AQP7 from the testicular cDNA library. However, to our knowledge the spatial expression pattern and biological roles of AQP7 remain to be elucidated in humans.

Materials And Methods: We investigated AQP7 expression in the human testis and ejaculated sperm from fertile men and from infertile patients.

Results: AQP7 was expressed at the tail of spermatids and spermatozoa in the human testis. AQP7 protein was also detected at the middle piece and the anterior tale portion of ejaculated sperm. However, some infertile patients lacked AQP7 expression in ejaculated sperm, although all fertile men expressed AQP7 protein. The motility rate of AQP7 negative sperm was significantly lower than that of AQP7 positive sperm, while the sperm concentration was not different between AQP7 positive and negative subjects.

Conclusions: AQP7 shows a spatial expression pattern in the human testis. AQP7 may be involved in the maintenance of sperm motility. Furthermore, a lack of AQP7 expression in sperm may be an underlying mechanism of male infertility.