Cellular responses and microRNA profiling in bovine spermatozoa under heat shock

Area of Science:

• Reproductive Biology
• Sperm Physiology
• Molecular Biology

Background:

• Sperm function is sensitive to temperature fluctuations.
• Elevated temperatures in vivo and in vitro reduce bovine sperm motility and fertility.
• The precise cellular and molecular effects of heat shock on sperm are not fully understood.

Purpose of the Study:

• To investigate the impact of heat shock on mature bovine sperm.
• To analyze functional, cellular, and molecular changes in sperm exposed to elevated temperatures.
• To determine the effect of heat shock on sperm microRNA profiles and subsequent embryo development.

Main Methods:

• Holstein bull sperm were cryopreserved and thawed.
• Sperm were incubated at 35°C, 38.5°C, and 41°C for 4 hours.
• Sperm motility, mitochondrial activity, reactive oxygen species, caspase activity, fertilizing ability, and microRNA profiles were assessed.

Main Results:

• Heat shock at 41°C reduced sperm motility; 38.5°C and 41°C reduced mitochondrial activity.
• Increased reactive oxygen species and caspase activity were observed in heat-shocked sperm.
• Fertilizing ability, cleavage rates, and blastocyst rates were diminished; specific microRNAs were altered, with miR-181d enriched at higher temperatures.

Conclusions:

• Elevated temperatures disrupt bovine sperm physiology, impacting cellular functions and microRNA expression.
• Heat-induced sperm damage leads to reduced fertilizing capacity and impaired preimplantation embryo development.
• Temperature control is crucial for maintaining sperm quality and optimizing assisted reproductive technologies.