In this study, the effects of Sildenafil Citrate on the sperm quality during cryopreservation in the asthenozoo- spermic patients were investigated for the first time. Thirty semen samples were collected from asthenozoo- spermic patients and each sample was divided into 3 groups: Control (fresh), Freeze and Freeze + Sildenafil. In each groups the sperm parameters, DNA fragmentation, acrosome integrity, protamine deficiency, mitochondrial membrane potential, plasma membrane integrity, the expression of Bcl-2 and HSP70 genes, as well as the level of Tumor necrosis factor-alpha, Malondialdehyde and antioxidants (Catalase, Glutathione, and Superoxide dis- mutase) in sperm were assessed. Data were analyzed statistically using Repeated Measure Analysis. The level of Malondialdehyde and Tumor necrosis factor-alpha, morphological abnormalities, DNA fragmentation, protamine deficiency and the expression of Bcl-2 and HSP70 genes increased significantly in the Freeze group compared to the Control, while the level of sperm parameters and antioxidants, plasma membrane integrity, mitochondrial membrane potential and acrosomal integrity significantly decreased. In the Freeze + Sildenafil group, compared to the Freeze group, all the mentioned parameters were significantly reversed except for the acrosomal integrity (decreased even more) and the expression of Bcl-2 (increased even more) and HSP70 genes (with no change). Although adding Sildenafil to the freezing medium decreased the adverse effects of freezing on the sperm of asthenozoospermic patients and improved sperm quality, but it also caused premature acrosome reaction. Therefore, we suggest the consumption of Sildenafil along with another antioxidant, to benefit from the favorable effects of Sildenafil as well as to maintain the integrity of the sperm acrosome.
