The cryoprotective effect of vitamins on human spermatozoa quality: a systematic review and meta-analysis

The Cryopreservation of spermatozoa ensures preserving fertility potential after some medical treatments such as chemotherapy and radiotherapy in cancer patients. However, many spermatozoa encounter serious damages, and their motility and viability decrease considerably after thawing. The excessive production of reactive oxygen species is one of the major causes of these damages. The supplementation of cryopreservation media with vitamins, which are well-known antioxidants, can reduce cryopreservation-induced damages. In this systematic review, we aimed to evaluate the cryoprotective effect of various vitamins on the quality of cryopreserved-thawed human spermatozoa. Two researchers searched PubMed, ISI, and Scopus databases up to March 2020. All original articles using vitamins in human spermatozoa cryopreservation media were included. We used a standardized form to extract sample size and to determine sample quality, the type and dose of vitamins, and the cryopreservation methods and their effects. We performed a meta-analysis on studies with available data (Mean + SD in cryoprotectant and cryoprotectant + cryoprotectant groups). We also performed a test of between-study heterogeneity, subgroup analysis, and meta-regression. Out of 258 studies, 16 articles were included for the analysis. Our meta-analysis revealed that using vitamins in cryopreservation media could increase motility by 4.60% (95% CI 6.16, 3.05; P = 0.0001), viability by 5.71% (95% CI 9.71, 1.72; P = 0.0001), and DNA integrity by 10.20% (95% CI 12.98, 7.42; P = 0.0001) in cryopreserved-thawed spermatozoa. We found a significant correlation between using vitamins and improved spermatozoa quality; the sperm motility and viability were improved and DNA fragmentation was reduced after thawing by vitamins. However, we could not emphasize on any type or dose of vitamins but we conclude that the anti-oxidative function of vitamins is the main reason for these benefits.