Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/4/2005
Publication Date: 7/25/2005
Citation: Barrera-Compean, M.H., Purdy, P.H., Dzakuma, J.M., Newton, G.R., Nuti, L.C. 2005. Cholesterol-loaded cyclodextrin improves post-thaw goat sperm motility. Journal of Animal Science. 2005. 83 (Supl 1):153.
Interpretive Summary: During cooling and freezing, a sperm is subjected to decreasing temperatures that reorganize the plasma membrane lipids and proteins. This reorganization results in a rigid plasma membrane that is less apt to survive freezing. One method for improving post-thaw quality is to treat the sperm (bull, ram, stallion) with cholesterol-loaded cyclodextrin because the lipid treatment makes the plasma membrane more flexible at lower temperatures and the sperm respond to the physical stresses better. A cyclodextrin is a circular sugar that can incorporate a lipid into the center of the circle. This puts the cholesterol in a form where it can be readily incorporated into the plasma membrane of a sperm. If the sperm are treated with cholesterol in this manner, the membrane is more fluid at lower temperatures and the sperm survives freezing better. Semen samples from 25 bucks were treated with 0, 1.5, 2.0, 2.5, or 3.0mg of CLC and then cryopreserved. Post-thaw motility analysis resulted in significantly more motile buck sperm with the 1.5, 2.0, 2.5 and 3.0mg CLC treatment (46, 50, 52 and 50%, respectively) compared to the 0mg treatment (42%; P < 0.05). No differences in plasma membrane or acrosomal membrane integrity were detected. The research presented here will potentially improve the fertility of cryopreserved buck sperm in a methodology that can be readily utilized by the goat industry and will provide a better understanding of what happens to a sperm when it is cryopreserved, particularly the effects of cryopreservation on the membranes of the sperm and on the processes associated with sperm physiology.
Technical Abstract: Membrane destabilization can occur when the sperm plasma membrane undergoes a phase transition from the liquid crystalline phase to the gel phase due to a decrease in temperature. Various lipids have been added to sperm prior to cooling to avoid this phase transition. It is documented that increasing the cholesterol membrane concentration of liposomes removes the phase transition during cryopreservation. Furthermore, treating bull, ram, and stallion sperm with cholesterol-loaded-cyclodextrin (CLC) prior to cryopreservation results in higher proportions of motile and membrane intact sperm after thawing. Application of the CLC treatment has not been documented using goat sperm. Therefore, the goal of this study was to determine if treating buck sperm with CLC in a Tris-citric acid-fructose diluent (15% egg-yolk, 7% glycerol) would improve the post-thaw sperm quality. Semen samples were collected from 25 bucks. Aliquots (240 x 106 sperm) from each ejaculate were treated with 0 (control), 1.5, 2.0, 2.5, and 3.0 mg CLC in separate test tubes and then cryopreserved. After thawing, sperm motility, plasma membrane integrity, and acrosome integrity were assessed using a computer assisted sperm analysis system and flow cytometry. Treatment differences between control and CLC-treated sperm for motility and membrane integrities were determined by ANOVA. CLC treatment resulted in significantly higher proportions of motile sperm at 1.5, 2.0, 2.5, or 3.0 mg CLC dosages (46, 50, 52 and 50%, respectively) compared to control sperm (42%; P < 0.0003). No significant differences were detected in the plasma membrane or acrosomal membrane integrity analyses. These results demonstrate that treating buck sperm with cholesterol prior to cryopreservation results in higher post-thaw motility without affecting plasma membrane and acrosomal membrane integrity.