Comparison of the effects of two methods of cryopreservation on testicular sperm DNA.

OBJECTIVE To assess the effects of two methods of freezing on testicular sperm DNA from subjects with obstructive azoospermia and to compare these with samples of fresh and freeze-thawed testicular sperm from fertile men. DESIGN The Comet assay was used to determine the percentage of undamaged DNA in fresh testicular sperm, testicular sperm freeze-thawed in suspension and in a biopsy sample (men with obstructive azoospermia), and in fresh and freeze-thawed testicular sperm (fertile men). SETTING The Regional Fertility Center, Royal Maternity Hospital, Belfast, Northern Ireland, United Kingdom. PATIENT(S) Twelve males with obstructive azoospermia (normal testicular volume and hormone profiles) and nine fertile control subjects. INTERVENTION(S) Trucut needle testicular biopsy under local anesthetic. MAIN OUTCOME MEASURE(S) Measurement of the percentage of undamaged DNA in fresh and freeze-thawed testicular sperm using the Comet assay. RESULT(S) No significant difference was found between the percentage of undamaged DNA of fresh testicular sperm and of both types of freeze-thawed testicular sperm. There was also no significant difference between the percentage of undamaged DNA in fresh or freeze-thawed testicular sperm from controls. Control ejaculated sperm DNA was significantly more damaged than testicular sperm DNA from control men. CONCLUSION(S) Cryopreservation of testicular sperm does not increase baseline levels of DNA damage.