Sperm Cryo-Tolerance

Cryotolerance of sperm is a strictly individual indicator that allows more accurate prediction of sperm quality after thawing.

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Криолечение

Cryo-tolerance of spermatozoa — a key factor for successful freezing

Cryotolerance of spermatozoa is their ability to survive, retain their structure and function after the process of freezing and thawing. This is especially important in the practice of assisted reproduction, since not all sperm tolerate cryopreservation equally well.

What Happens When Freezing?

The cryopreservation process includes:

  1. Addition of cryoprotective agent
  2. Gradual cooling to -196°C (liquid nitrogen);
  3. Defrost when needed for use.

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During this cycle, physical and biochemical changes occur that can affect:

  • Membrane integrity;
  • DNA stability;
  • The acrosomal reaction;
  • The motility and morphology of spermatozoa.

What is cryotolerance?

Cryotolerance reflects the endurance of sperm to cryopreservation. In some men, especially with a lower quality of ejaculate, the number of viable sperm after thawing may decrease significantly.

Factors that influence include:

  • Sperm quality before freezing;
  • Level of DNA fragmentation;
  • Presence of antioxidants and protective substances;
  • Type and duration of freezing.

How is cryotolerance assessed?

  1. First sample — standard analysis of fresh semen;
  2. Freezing a control part
  3. Thawing and re-analysis after 24—72 hours
  4. Comparison of parameters before and after:
  • Concentration;
  • Motility (progressive, weak and immobile spermatozoa);
  • Morphology;
  • DNA fragmentation (if needed).

What does the cryo-tolerance test show?

At:

- > 50% preserved mobility after thawing — good cryo-tolerance;
- ≤ 50% mobility after thawing — additional sample preparation or an alternative technique such as ICSI is recommended.

What do we offer in our clinic?

At Invitro Clinic “Sofia” we carry out an evaluation of sperm cryo-tolerance as part of the planned freezing.

Advantages:

  • Qualitative cryopreservation;
  • Possibility of trial freezing and thawing;
  • Personalized recommendation for future procedures;
  • Incorporation of antioxidant supplements as needed.

Conclusion

Cryotolerance of spermatozoa is an individual indicator that must be taken into account when planning freezing. Its evaluation allows for more accurate prediction of post-thawing quality and helps to make the right decisions in assisted reproduction.

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