Quantification of CatSper1 expression in human spermatozoa and relation to functional parameters

STUDY QUESTION Is CatSper1 expression in human spermatozoa related to semen parameter values and sperm functions? SUMMARY ANSWER CatSper1 expression is positively related to progressive and hyperactivated (HA) motility, [Ca2+]i responsiveness to progesterone but not the acrosome reaction (AR). WHAT IS KNOWN ALREADY The role of cationic channel of sperm (CatSper) in sperm functions is clear in animal models but less defined in human sperm cells. Current knowledge is mostly based on low specificity CatSper inhibitors showing agonistic and toxic effects on human spermatozoa and is thus of little help in clarifying the role of the CatSper channel in human sperm functions. STUDY DESIGN, SIZE, DURATION CatSper1 protein expression was evaluated in 115 men undergoing semen analysis for couple infertility. CatSper1 expression was related to routine semen parameters, motility kinematic parameters and basal and progesterone-stimulated [Ca2+]i and the AR. PARTICIPANTS/MATERIALS, SETTING, METHODS CatSper1 expression was evaluated (n = 85 normozoospermic, n = 30 asthenozoospermic patients) by immunofluorescence coupled to flow cytometry leading to quantitative measurement of the percentage of ejaculated sperm cells expressing the protein. Semen analysis was evaluated according to World Health Organization guidelines. Kinematic parameters were evaluated by a computer-aided sperm analysis system. [Ca2+]i was measured by a spectrofluorimetric method in fura-2-loaded spermatozoa. The AR was evaluated in live sperm cells by fluorescent-labeled lectin. MAIN RESULTS AND THE ROLE OF CHANCE CatSper1 protein expression in spermatozoa was reduced in asthenozoospermic men (mean ± SD: 53.0 ± 15.5%, n = 30 versus 67.9 ± 17.1% in normozoospermic, n = 85, P < 0.01) and was significantly correlated with progressive (r = 0.36, P < 0.001), total (r = 0.35, P < 0.001) and HA (r = 0.41, P < 0.005) motility. In addition to a higher percentage of spermatozoa not expressing CatSper1, asthenozoospermic men showed a large number of spermatozoa with immunofluorescent signal localized outside the principal piece compared with those in normozoospermia. A significant positive correlation was found between CatSper1 protein expression and the increase of [Ca2+]i in response to progesterone (r = 0.36, P < 0.05, n = 40) but not with basal [Ca2+]i. No correlation was found with the AR, either basal or in response to progesterone. LIMITATIONS, REASONS FOR CAUTION The study is partly descriptive. Furthermo