To investigate the expression levels of claudin-11 mRNA and the localization of claudin-11 protein in testes of infertile men.

This study included 5 men with obstructive azoospermia and 50 men with nonobstructive azoospermia who had undergone testicular sperm extraction. Testicular tissues were obtained from these men and expression levels of claudin-11 mRNA in testicular samples were determined by real-time reverse transcription-polymerase chain reaction. The localization of claudin-11 protein was analyzed by immunofluorescent staining.

Expression levels of testicular claudin-11 mRNA in nonobstructive azoospermia men were significantly greater than in obstructive azoospermia men, whereas there was no significant difference in testicular claudin-11 mRNA expression between men with and without successful sperm retrieval by testicular sperm extraction. Based on the findings of immunofluorescent staining, expression patterns of claudin-11 protein could be divided into normal (localization to basal component of seminiferous tubules) and abnormal patterns (diffuse expression in Sertoli cells/extremely low or no expression). The proportion of nonobstructive azoospermia men with an abnormal expression pattern of claudin-11, particularly that of Sertoli cell–only syndrome men, was significantly greater than that of obstructive azoospermia men. Furthermore, claudin-11 expression showing an abnormal pattern in men without successful sperm retrieval was significantly frequent compared with those whose sperm were successfully retrieved.

These findings suggest that disorganization of claudin-11 expression in Sertoli cells might be one of the factors involved in the impairment of spermatogenesis.