Cryo-scanning electron microscopy demonstrates that ice morphology is not associated with the post-thaw survival of domestic boar (Sus domesticus) spermatozoa: A comparison of directional and conventional freezing methods

Gillis, James D.; Holt, William V.; Penfold, Linda M.; Woad, Kathryn J.; Graham, James K.; Watts, Julie A.; Gardner, David S.; Yon, Lisa

Abstract

Directional freezing (in 2 or 10 ml hollow glass tubes) has been reported to improve post-thaw sperm survival parameters compared to conventional methods (in 0.5 ml straws). However, the biophysical properties that increase post-thaw survival are poorly understood. Therefore, the aim for the current study was to investigate the effect of ice morphology on the post-thaw survival of domestic boar spermatozoa directionally and conventionally cryopreserved in 0.5 ml straws. Ice morphology was quantitatively analyzed using a combination of cryo-scanning electron microscopy and Fiji Shape Descriptors. Multivariate analysis found a significant, non-linear effect (p < 0.05) of interface velocity on ice morphology, with an increase in both ice-lake size, as indicated by area and in aspect ratio, at an interface velocity of 0.2 mm/s. By contrast, post-thaw sperm survival (defined as spermatozoa with both intact plasma membranes and acrosomes) was biphasic, with peaks of survival at interface velocities of 0.2 mm/s (54.2 ± 1.9%), and 1.0 or 1.5 mm/s (56.5 ± 1.5%, 56.7 ± 1.7% respectively), and lowest survival at 0.5 (52.1 ± 1.6%) and 3.0 mm/s (51.4 ± 1.9%). Despite numerical differences in Shape Descriptors, there was no difference (p > 0.05) in the post-thaw survival between conventionally and directionally cryopreserved samples at optimal interface velocities of 1.0 or 1.5 mm/s. These findings suggest that: 1) ice morphology has little impact on post-thaw survival of boar spermatozoa, and 2) directional freezing in 0.5 ml straws (rather than 2 or 10 ml hollow glass tubes) may attenuate benefits of directional freezing.

Citation

Gillis, J. D., Holt, W. V., Penfold, L. M., Woad, K. J., Graham, J. K., Watts, J. A., …Yon, L. (2022). Cryo-scanning electron microscopy demonstrates that ice morphology is not associated with the post-thaw survival of domestic boar (Sus domesticus) spermatozoa: A comparison of directional and conventional freezing methods. Cryobiology, 108, 10-18. https://doi.org/10.1016/j.cryobiol.2022.08.006

• Journal Article Type: Article
• Acceptance Date: Aug 31, 2022
• Online Publication Date: Sep 27, 2022
• Publication Date: 2022-10
• Deposit Date: Nov 15, 2022
• Publicly Available Date: Sep 28, 2023
• Journal: Cryobiology
• Print ISSN: 0011-2240
• Electronic ISSN: 1090-2392
• Publisher: Elsevier BV
• Peer Reviewed: Peer Reviewed
• Volume: 108
• Pages: 10-18
• DOI: https://doi.org/10.1016/j.cryobiol.2022.08.006
• Keywords: General Agricultural and Biological Sciences; General Biochemistry, Genetics and Molecular Biology; General Medicine
• Public URL: https://nottingham-repository.worktribe.com/output/10920094
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S001122402200092X