【Animal Modeling】-Optimization of the freezing method of cynomolgus monkey semen without yolk freezing solution

  Objective Due to the existence of uncertain components such as yolk in traditional sperm freezing solutions, there is a risk of biological contamination. Therefore, this study aimed to use Origio and Quinn's two commercial yolk-free cryopreservations to preserve cynomolgus monkey germplasm resources and to determine the optimal cryopreservation conditions for cynomolgus monkey sperm.

  Methods The semen of male monkeys was collected by electrical stimulation of the penis, and the sperm of cynomolgus monkeys were frozen at different heights on the surface of liquid nitrogen after mixing with two kinds of cryopreservation solutions according to different volume ratios. After recovery, the sperm survival rate, recovery rate and acrosome integrity rate were counted to determine the optimal conditions of cryopreservation solution, and Quinn's cryopreservation solution was used to confirm the effect of seminal plasma on sperm freezing under optimal conditions.

  Results The optimal conditions for freezing cynomolgus monkey sperm using Origio and Quinn's sperm cryopreservation solution were as follows: the suspension height was 5 cm from the liquid nitrogen surface, and the volume ratio of the semen cryopreservation solution was 1 ∶ 0. 5. The sperm recovery rate of 's group was 38.02% ± 14.98%, which was significantly higher than that of Origio group, which was 15.11% ± 14.49%. There was no between-group difference in the rate of acrosome integrity. Preservation of seminal plasma improves the freezing effect of yolk-free cryopreservation. The sperm recovery rate and acrosome integrity rate after seminal plasma retention were 37.57% ± 13.22% and 84.64% ± 8.82%, respectively; the sperm recovery rate and acrosome integrity rate without seminal plasma retention were : 21. 46% ± 7. 25%, 75. 50% ± 9. 62%.

  Conclusion The yolk-free cryopreservation solution can successfully preserve cynomolgus monkey sperm, which provides a safe and reliable method for the protection of cynomolgus monkey fertility and the preservation of germplasm resources.