Evaluation of human sperm function after repeated freezing and thawing

Area of Science:

• Reproductive biology
• Cryobiology
• Andrology

Background:

• Sperm cryopreservation is crucial for assisted reproductive technology (ART), especially for men facing fertility challenges due to medical procedures or low sperm counts.
• Evaluating the impact of repeated freeze-thaw cycles on sperm quality and function is essential for optimizing ART protocols.

Purpose of the Study:

• To assess the viability and fertilizing capacity of human sperm after multiple freeze-thaw cycles.
• To compare the effectiveness of slow versus rapid freezing methods on sperm recovery.
• To determine the protective role of seminal plasma during sperm cryopreservation.

Main Methods:

• Sperm samples (normozoospermic and oligozoospermic) underwent three freeze-thaw cycles using both slow and rapid freezing techniques.
• Sperm parameters including motility, viability, and morphology were evaluated after each thaw.
• Fertilization potential was assessed using hamster oocyte microinjection.

Main Results:

• Sperm survived three freeze-thaw cycles, with significant declines in motility and viability between cycles (P < .01).
• No significant differences were observed between slow and rapid freezing methods, or between washed and unwashed samples.
• Seminal plasma did not enhance sperm protection during cryopreservation.
• Sperm retained fertilizing capacity after three cycles, evidenced by successful oocyte fertilization.

Conclusions:

• Repeated freeze-thaw cycles (up to three) are feasible for sperm cryopreservation without compromising fertilizing ability for intracytoplasmic sperm injection (ICSI) in ART.
• Washed sperm can be effectively cryopreserved and re-utilized, offering significant benefits for men with sperm production difficulties.
• Current cryopreservation protocols are adequate for ART, even with multiple freeze-thaw cycles.