Objective: Asthenozoospermia is characterized by reduc- tion of sperm motility and it causes infertility. Human semen cryopreservation is a technique that can keep sperm survive indefinitely, enabling the conservation of male fertility. There- fore, it considered as indispensable part of assisted reproduc- tive centers, andrology laboratories and sperm bank. The sperm cryopreservation process can cause losing the sperm function and some of its fertility potentials due to some detrimental fac- tors especially oxidative stress. The major aim of adding some substances to the sperm freezing medium is to get an optimal number of functional sperms. This study investigated to assess the Sildenafil Citrate effect on sperm parameters of the astheno- zoospermic infertile men During Cryopreservation. Material and Methods:30 semen samples were collected from men with asthenozospermia parameters attended the Androl- ogy unit of the Qom Infertility Treatment Center. Each sample was divided into 2 equal aliquots: control (were treated with cryo-protectant alone), Sildenafil Citrate (were treated with cryo-protectant + 0.67µM Sildenafil Citrate solution). In each sample, sperm mobility according to WHO criteria, sperm vi- ability with eosin-nigrosin assay and sperm morphology with Diff Quik assay were assessed. Results:Our results showed that proportion of sperm motility, viability and morphology significantly increased in the Sildena- fil Citrate group compared to control group (p<0.05). Conclusion: In vitro Sildenafil Citrate supplementation of cry- opreserved ejaculate sperm, from infertile men, resulted in a significant enhancement of post-thaw sperm quality.
