Cryopreservation of Mauritian Cynomolgus Macaque (Macaca fascicularis) Sperm in Chemically Defined Medium.

The objective of this study was to optimize cryopreservation of sperm from Mauritian cynomolgus macaques (MCM) in defined conditions. Sperm viability and motility were compared between sperm cryopreserved in chemically-defined freezing media with variable osmolarity and the presence of either ethylene glycol or glycerol. The highest percentage viability (after freeze-thaw) was seen in sperm samples that were cryopreserved in medium with an osmolarity of 310 mOsm, while higher osmolarities markedly decreased sperm viability. Ethylene glycol and glycerol at concentrations of 4.6% and 5%, respectively, preserved sperm viability to an equivalent degree. Although higher motility rates and higher straight-line velocities were observed in sperm samples frozen in glycerol compared with ethylene glycol, these differences were not statistically significant. Thawed sperm frozen in defined conditions with glycerol were capable of fertilizing MCM oocytes in vitro, with development to the blastocyst stage. The protocol described here provides an effective method for cryopreservation of sperm to facilitate subsequent in vitro fertilization and genome editing of embryos in MCM species.