Antifreeze proteins are robust cryoprotectants for sperm cryopreservation in fishes: A systematic review and meta-analysis

The effectiveness of antifreeze proteins as cryoprotectants for cryopreservation of genital materials has been always controversial in the literature. In the present study, we evaluated the effect of antifreeze proteins in cryopreservation of sperm in four fish species (66.6% Acipenseridae, 11.1% Cyprinidae, and 22.2% Sparidae). PubMed, Scopus, Web of Science, and Google Scholar search engines were searched for studies that tested the effects of antifreeze proteins in cryopreservation and vitrification of sperm without any time and language exclusions. We used motility percentage as the common outcome in the eight most relevant studies that were chosen from 142 search records. The viability percentage reported by four of these studies was also included. The publication bias and sensitivity analysis showed there was no publication bias and sensitivity to any study. Our findings here show that antifreeze proteins type I and III are significantly effective in the preservation of motility (SMD = 1.466, 95% CI, 1.073–1.860) and viability (SMD = 1.492, 95% CI, 0.557–2.427) of spermatozoa from different fish species after cryopreservation. Our different subgrouping strategies also revealed that the heterogeneity within and between studies does not lie in antifreeze protein type, species, cryopreservation technique, and the use of other cryoprotectants in combination with antifreeze proteins. Here we propose that future studies target the combined effect of heterogeneity sources. This is the first report of a meta-analysis that considered the effects of antifreeze proteins as cryoprotectants in fish sperm cryopreservation.