The effects of cryopreservation by vitrification on motility, viability and spontaneous acrosome reaction of human spermatozoa.

Cryopreservation of human sperm is routinely performed in assisted reproduction wards. During which, osmotic effects of freezing and thawing can impair sperm motility and viability, and decrease fertilizing capacity. In addition, variety of cryoprotectants is available to protect sperm from negative effects of cryopreservation processes. Aim of present study is to compare the effects of vitrification, with and without cryoprotectant, on postthaw sperm quality. Semen samples obtained from 29 healthy men referring to Avesina Infertility Clinic, were collected by masturbation, and analyzed according to WHO criteria. The semen samples were divided into two equal aliquots for: vitrification with (HSPM) and without (only seminal plasma) cryoprotectants. Equal volume of cryoprotectants was added to aliquots of samples and mixture filled in straws, plunged into liquid nitrogen, stored for at least 7 days and thawed. Percentage of motility was measured manually, using light microscope, and viability and acrosome reaction analysis were performed by triple staining. Sperm motility, viability and acrosome reaction of semen samples (n = 29), decreased significantly, after freeze/thawing, in comparison prior to freezing. Postthaw motility was highest in samples frozen without cryoprotectant, in comparison with HSPM (p<0.001). Significant differences were observed in the rate of viability and acrosome reaction before and after vitrification (P<0.001) with no significant differences between samples freezing with and without cryoprotectants. In conclusions, long-term storage in liquid nitrogen, at -196 ˚C, consistently causes reduction in postthaw sperm quality. Evaluation of motility, viability and acrosome reaction of human spermatozoa before and after vitrification, suggest that vitrification without cryoprotectant have less deleterious effects on sperm parameters versus HSPM cryoprotectant.