Overcoming Cryopreservation Challenges in Mammalian Sperm: Strategies for Mitigating Cryoinjuries

Cryopreservation is a critical tool in the livestock industry, particularly for disseminating genetic materials and establishing sperm banks to preserve species. Developing a successful semen storage procedure is essential to minimize the negative effects caused by the cryopreservation process. Mammalian sperm are highly susceptible to cryoinjury and primarily inflicted during the freezing and thawing processes when extracellular water freezes and intracellular water is lost, negatively impacting sperm quality parameters and fertility. Cryoinjuries generally cause irreversible damage to sperm structure and function. Currently, various cryopreservation measures, such as selection of cryoprotectants and optimization of freezing and thawing processes, are employed to reduce sperm cryoinjuries and to elucidate the mechanisms underlying cryodamage. However, the exact nature of sperm cryoinjury remains largely unclear. This review discusses the current understanding of sperm cryodamage induced by the cryopreservation process, factors influencing sperm susceptibility to cryoinjury, the impacts of cryopreservation on proteins, metabolites, lipids, and RNAs. As one of the important measures to mitigate sperm cryoinjuries, the application of antioxidants is becoming increasingly important. So, the effects of antioxidants on post-thaw sperm quality are reviewed here.