Effect of pre-freezing conditions on semen cryopreservation in rhesus monkeys
2008
Dong, Q. | Rodenburg, S.E. | Huang, C. | VandeVoort, C.A.
Although sperm cryopreservation has been studied in at least 17 non-human primate species, systematic factor optimization for any single species is lacking. Gene banking of non-human primate sperm is still in its infancy. The objective of the present study was to initiate a systematic approach to optimize the process of sperm cryopreservation for rhesus macaques, specifically, factors related to pre-freezing conditions (e.g., straw freezing position, sperm concentration, sperm washing, equilibration methods, and equilibration time periods). Straw position had no effect on post-thaw motility (P =0.193). Sperm concentration was tested in a range from 5x10⁶ mL⁻¹ to 5x10⁸ mL⁻¹; post-thaw motility of sperm samples frozen at 5x10⁷ cellmL⁻¹ (51.0±10.6%; mean±S.D.) and 5x10⁸ cellmL⁻¹ (48.1±7.3%) were higher than samples frozen at 5x10⁶ cellsmL⁻¹ (33.0±12.0%, P =0.003). Comparison of motility immediately after thawing between samples with (51.2±6.2%) and without washing (53.9±6.8%) revealed no differences (P >0.05). However, washing improved sperm forward progression within 1h after thawing, whereas unwashed sperm retained higher post-thaw motility and progression during extended incubation (4h) after thawing (P <0.05). Equilibration methods (with or without pre-cooling) made no difference on post-thaw motility (P >0.05), and the most effective equilibration time was the duration required for samples to acclimate to 4°C prior to freezing. Evaluation and optimization of these pre-freezing conditions will help to minimize sources of injury, maximize survival, and contribute to the development of an optimized cryopreservation protocol for rhesus macaque sperm.
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