Background: Asthenozoospermia, characterized by decreased mobility or complete immobility of sperms, is significantly prevalent. Cryopreservation, an indispensable part of assisted reproductive technology, impairs sperm function. Most side effects of cryopreservation are due to increased reactive oxygen species levels during freezing and thawing. Therefore, adding antioxidants to the cryopreservation medium maybe can compensate for the freezing adverse effects. Sildenafil citrate (SC) has a wide range of applications, such as erectile dysfunction, and many studies have reported that sildenafil has antioxidant properties and many positive effects on sperm parameters. Objective: In this study, the effects of SC as an antioxidant on sperm chromatin and acrosomal integrity during cryopreservation in asthenozoospermic patients were investigated for the first time. Materials and Methods: 30 semen samples were collected from asthenozoospermic men referred to the infertility treatment center of Qom University Jihad from July to December 2021. Each sample was divided into 3 groups: control (fresh), freeze (treated with cryo-protectant alone), and freeze+ SC (treated with cryo-protectant+ 0.67 µM SC solution). In the freezing groups, samples were cryopreserved with human sperm freezing medium and rapid freezing method. The DNA fragmentation, protamine deficiency, and acrosome integrity were assessed in each sample SDFA (Sperm DNA Fragmentation Assay) Kit, Chromomycin A3 staining, and FITC-PSA (fluorescein isothiocyanate-conjugated pisumsativum agglutinin) staining respectively. Results: The DNA fragmentation and protamine deficiency increased significantly in the freeze group compared to the control (p < 0.001), while the acrosomal integrity significantly decreased (p < 0.001). In the freeze+ SC group, compared to the freeze group, the mentioned parameters were significantly reversed (p < 0.001), except for the acrosomal integrity (decreased even more (p = 0.009)). Conclusion: In conclusion, although adding SC to the freezing medium decreased the adverse effects of freezing on the sperm of asthenozoospermic men and improved sperm chromatin quality, it also caused premature acrosome reaction. Therefore, it is suggested that the consumption of SC and another antioxidant benefit from the favorable effects of SC and maintain the integrity of the sperm acrosome.
