Aquaporin-Mediated Water and Hydrogen Peroxide Transport Is Involved in Normal Human Spermatozoa Functioning.

Different aquaporins (AQPs) are expressed in human sperm cells and with a different localization. Their function has been related to cell volume control in response to the osmotic changes encountered passing from the epididymal fluid to the cervical mucus or involved in the end stage of cytoplasm removal during sperm maturation. Recently, AQPs have also shown hydrogen peroxide (H2O2) permeability properties. Here, we investigate the expression, localization and functioning of AQPs in human sperm cells with particular attention to their role as peroxiporins in reactive oxygen species (ROS) scavenging in both normospermic and sub-fertile human subjects. Western blotting and immunocytochemistry were used to confirm and clarify the AQPs expression and localization. Water and H2O2 permeability was tested by stopped flow light scattering method and by the CM-H2DCFDA (5-(and-6)-chloromethyl-2',7'-dichlorodihydro-fluorescein diacetate, acetyl ester) H2O2 fluorescence probe, respectively. AQP3, -7, -8, and -11 proteins were found in human sperm cells and localized in the head (AQP7), in the middle piece (AQP8) and in the tail (AQP3 and -11) in both the plasma membrane and in intracellular structures. Sperm cells showed water and H2O2 permeability which was reversibly inhibited by H2O2, heat stress and the AQP inhibitor HgCl2. Reduced functionality was observed in patients with compromised basal semen parameters. Present findings suggest that AQPs are involved in both volume regulation and ROS elimination. The relationship between sperm number and motility and AQP functioning was also demonstrated.

Human spermatozoa cryopreservation: comparison of three different freezing protocols.

Human spermatozoa cryopreservation has significantly improved over the last few decades, but the actual protocols are neither optimal nor standardized between different laboratories in spite of the importance of preserving male fertility or treating severely infertile males. In the present study we aimed to determine the best in-house method of rapid freezing in terms of sperm motility and vitality by comparing three different rapid methods of human spermatozoa cryopreservation. Our data showed that M1 (triphasic cooling) is the method associated with a significantly lower deterioration of semen quality in comparison with mono or biphasic cooling. Differences observed among the three protocols were supported by statistical analysis. These data reinforce previous evidences about the influence of sperm quality on IVF outcome and suggest the importance of improving sperm cryopreservation techniques especially when semen is seriously compromised at baseline.