A Preliminary Study On The Protective Effect Of Vitamin E (Trolox) On Oxidative Stress In Human Spermatozoa

Background:Male infertility becomes a social problem and its incidence continue to rise without a pause in recent years.Even though the Artificial Reproductive Techno logy(ART)had made remarkable progress in treatment of male infertility, but the poor sperm motility after cryopreservation is still a major obstacle.Recently, Reactive Oxygen Species(ROS) which emerged in the cryopreservation and thawing procedure induced oxidative stress was considered as the major reason for post-thawing sperm motility loss. Vitamin E which play a key role in the antioxidant system can protect the polyunsaturated fatty acid from peroxidation induced by ROS. Glycerol-based cryoprotectant is most widely used and major cryoprotectant solution, and this study aims to clear that whether Vitamin E can ease the oxidative injury to sperm and improve the post-thawing motility by adding proper concentration of Vitamin E into cryoprotectant.Objective:To survey the concentration of reactive Oxygen Species and lipid peroxidation product malondialdehyde of post-thawing human sperm,and analysis the sperm motility, progressive motility and kinematics parameters before and after thawingto evaluate the effect and mechanism of Vitamin E (Trolox) addition to freezing extender on the motility of post-thawing human sperm.Methods:Semen samples from16fertile men were mixed with modified cryoprotectant and every semen sample was equally divided into4groups according to the concentration of Trolox after analysis for fresh sperm motility, progressive motility and kinematics parameters.The group containing no VE served as control group, and G1,G2, G3contain VE of concentration of50uM,100uM,200uM respectively.Before and after thawing, semen samples were subjected to analysis for sperm kinematics by computer-assisted semen analysis(CASA),for reactive oxygen species(ROS) by flow cytometry(FCM),and for malondialdehyde(MDA),which indicates the sperm membrane lipidperoxidation, by using thiobarbituric acid(TBA) assay.According to the experiment results,to make a conclusion that whether there is statistical differences between experiment groups and control group.Results:Compared with fresh sperm, the motility, progressive motility and kinematics parameters of all groups were decreased after cryopreservation (P<0.001), but compared with the control group (47.85±5.09%), the progressive motility decrease was less (P<0.05) in Trolox100uM group (53.33±5.63%).Differences were also observed among groups in sperm kinematic indicators (curvilinear velocity, average path velocity), with higher values for the Trolox100group (P<0.05). Corresponsively, ROS and MDA were lower for the Trolox100and200uM groups (P<0.05)Conclusion:VE (Trolox) addition to freezing extender at moderate concentration may decrease the surplus ROS emerged in the freeze-thawing procedure, ease the membrane oxidative stress injury and improve human sperm progressive motility and kinematic parameters after cryopreservation.