Investigating the Cryotolerance of Boar Spermatozoa Subjected to Prior Selection

Authors: LEWIS, M - Mississippi State University; DURFEY, C - Mississippi State University; HARTUNG, S - Mississippi State University; STEADMAN, C - Mississippi State University; PARK, S - Mississippi State University; CLEMENTE, H - Clemente Associates; WILLARD, S - Mississippi State University; RYAN, P - Mississippi State University; FEUGANG, J - Mississippi State University

Submitted to: Journal Of Reproduction, Fertility And Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2017
Publication Date: 12/4/2017
Citation: Lewis, M., Durfey, C., Hartung, S., Steadman, C., Park, S., Clemente, H., Willard, S., Ryan, P., Feugang, J. 2017. Investigating the Cryotolerance of Boar Spermatozoa Subjected to Prior Selection. Journal Of Reproduction, Fertility And Development. 30:244.

Interpretive Summary: In a previous study, we showed that specifically designed magnetic nanoparticles were able to target damaged boar spermatozoa in semen doses used for artificial inseminations. This novel magnetic approach permits the selection of robust and healthier spermatozoa maintaining fertility performance. Here we tested the tolerance of nano-selected or nano-purified spermatozoa to cryopreservation. The study is still ongoing for the potential improvement of sperm freezability outcomes in the swine industry.

Technical Abstract: The proportion of non-viable spermatozoa in insemination semen doses pose limitations to breeding. Recent studies have shown the potential of removing moribund spermatozoa from semen doses through their interactions with specifically designed magnetic nanoparticles (MNPs). This specific retrieval leads to substantial enrichment of insemination doses with robust spermatozoa (nanoselected), which would have advantageous effects on the animal husbandry industry. Here we explored the potential of these MNPs for semen dose enrichment for freezability improvement. The MNPs were synthesized to specifically target acrosome reacted and apoptotic spermatozoa. Freshly harvested semen of at least 2 boars were pooled and extended in a commercial diluent at a local stud. Extended semen (40 ml) were mixed with various amounts of MNPs (0, 87.5, and 175 µg) and incubated at 37oC, for 30 minutes. Thereafter, the tube mixtures were placed under an electromagnetic field for the trapping of moribund spermatozoa bound to MNPs, following by the elution of intact or MNPs-free (robust) spermatozoa. Both fresh (control) and robust spermatozoa were sequentially mixed with cryoguard (cooling and freezing) extenders, and frozen using the IceCube 14S-B freezer. Sperm motility characteristics were assessed before and after freezing (Computer-Assisted-Sperm-Analyzer), while the quality was evaluated post-thaw (flow cytometry). Data were analyzed (ANOVA-1) and P<0.05 indicate significant differences. The proportions of fresh motile (75±5%, 77±3%, and 84±2%) and progressive (44±4%, 49±2%, and 64±5%) spermatozoa were respectively increased following incubation with 0, 87.5, and 175µg MNPs, (P<0.05). The proportions of spermatozoa with bent tail and distal droplets were significantly decreased (P<0.05) and the greatest increased motility was seen with semen samples exhibiting poor motility (<70%). However, one-hour post-thawed analyses indicated poor (<10%), but comparable motility across groups. Equal proportions of spermatozoa showed intact plasma and acrosome membranes. In conclusion, the designed MNPs indicated advantageous effect on sperm motility and potential to achieve high-throughput semen enrichment. Despite the lower post-thaw outcomes, nanoselected spermatozoa appear less prone to insults. Further optimization of the freezing procedure is being investigated.