Dimethyl sulfoxide and glycerol as cryoprotectant agents of stallion semen: effects on blastocyst rates following intracytoplasmic sperm injection of IVM equine oocytes.

This research explores the effect of the sperm cryoprotectant agent (CPA) used when freezing horse semen on the success rate of in vitro fertilization. The study compared the use of dimethyl sulfoxide (DMSO) and glycerol as cryoprotectants and found that DMSO resulted in higher embryo cleavage rates, an important step in the fertilization process, though did not significantly affect overall blastocyst development.

Overview of the Research Study

• The study aimed to understand how the cryopreservation of stallion semen using different CPAs affects invitro blastocyst development. This is done following intracytoplasmic sperm injection (ICSI), a fertility treatment procedure.
• The researchers used single ejaculates from five stallions, which were processed in a freezing extender containing either 1M dimethyl sulfoxide (DMSO) or 3.5% glycerol, the two CPA under investigation.
• Immature equine oocytes, the cells that develop into an egg, were obtained from mares during diestrus through transvaginal aspiration.
• After the oocytes matured in vitro, the mature oocytes were fertilized using ICSI with the thawed stallion spermatozoa. This process was carried out for both the DMSO and glycerol groups.

Key Findings

• The researchers found higher embryo cleavage rates (a key stage in embryo development) in the group that used DMSO as the cryoprotectant agent (73.3%) compared to the group that used glycerol (46.7%).
• The study did not find a significant difference in the blastocyst development rate per fertilized oocyte (a mature egg cell) between the two groups. Nor was there a significant difference in the blastocyst production rate per cleaved embryo.
• Interestingly, although not statistically significant due to the small number of stallions used, there was noted increased blastocyst production and individual stallion variability among CPA treatments.

Implication of the Study

• In conclusion, based on the higher cleavage rates observed, DMSO may be a more effective CPA for equine sperm used for ICSI than glycerol.
• However, the observed differences were not statistically significant and the sample size was small, suggesting more research is needed.
• The research implies the need for further critical examination of cryoprotectants used in equine sperm subpopulations for ICSI in a larger number of stallions.