Effect of antioxidant supplementation of cryopreservation medium on post-thaw integrity of human spermatozoa

This study examined whether the addition of an antioxidant to cryopreservation medium could improve the post-thaw integrity of cryopreserved human spermatozoa, particularly from men with abnormal semen parameters. Semen samples were collected by masturbation and assessed following WHO standards. Normal (n = 23) and abnormal (n = 20) samples were divided into three aliquots prior to cryopreservation. The first aliquot remained untreated and was mixed with cryopreservation medium (in-house 1:1). The second and third aliquots were mixed with cryopreservation medium containing either 100 µmol or 200 µmol vitamin E analogue. Samples were frozen at −10° C per minute to −80°C, then plunged into liquid nitrogen. Thawed samples were assessed for motility, vitality and DNA integrity. Split-plot repeated-measures ANOVA was used to assess within-subject (dose) and between-group (normal/abnormal) differences in post-thaw motility index, vitality staining and DNA fragmentation. Vitamin E dose was significantly associated with post-thaw motility (P = 0.041) and the pattern of response across doses was similar for normal and abnormal groups. Post-thaw motility was significantly improved by the addition of 200 µmol vitamin E (P = 0.006), but neither vitality nor sperm DNA fragmentation were altered. These results suggest that the addition of vitamin E to cryopreservation medium improves post-thaw motility.