Controlled cooling versus rapid freezing of teratozoospermic semen samples: Impact on sperm chromatin integrity

AIM: The present study evaluates the impact of controlled slow cooling and rapid freezing techniques on the sperm chromatin integrity in teratozoospermic and normozoospermic samples. SETTING: The study was done in a university infertility clinic, which is a tertiary healthcare center serving the general population. DESIGN: It was a prospective study designed in vitro. MATERIALS AND METHODS: Semen samples from normozoospermic (N=16) and teratozoospermic (N=13) infertile men were cryopreserved using controlled cooling and rapid freezing techniques. The sperm chromatin integrity was analyzed in fresh and frozen-thawed samples. STATISTICAL ANALYSIS USED: Data were reported as mean and standard error (mean ± SEM) of mean. The difference between two techniques was determined by a paired t-test. RESULTS: The freeze-thaw induced chromatin denaturation was significantly (P<0.01) elevated in the post-thaw samples of normozoospermic and teratozoospermic groups. Compared to rapid freezing, there was no difference in the number of red sperms (with DNA damage) by the controlled slow cooling method in both normozoospermic and teratozoospermic groups. Freeze-thaw induced sperm chromatin denaturation in teratozoospermic samples did not vary between controlled slow cooling and rapid freezing techniques. CONCLUSIONS: Since the controlled slow cooling technique involves the use of expensive instrument and is a time consuming protocol, rapid freezing can be a good alternative technique for teratozoospermic and normozoospermic samples when sperm DNA damage is a concern.