Sperm preparation: DNA damage by comet assay in normo- and teratozoospermics

The present study was carried out on semen samples of human fertile and infertile subjects, teratozoospermics (TZs) and idiopathics (IDs), with neat semen and sperm prepared by swim up or Percoll density gradient centrifugation procedures. Sperm morphology analysis revealed that only head and midpiece defects in TZs and IDs were significantly (P < 0.001) higher compared to fertile subjects. Infertile subjects indicated significantly higher (P < 0.001) sperm DNA damage compared to fertile subjects. Fertile subjects with sperm prepared from neat and Percoll density gradient centrifugation exhibited a comet tail DNA percentage of 20% and 15%, respectively. The TZs and IDs infertile subjects had higher levels of comet tail DNA of 33% and 25% and 25% and 19%, respectively. A significant (F = 24.01; P = 0.0059) decrease in mean comet head DNA percentage or sperm DNA integrity was observed in neat samples from fertile and infertile subjects by Repeated Measures ANOVA. In Percoll prepared samples from fertile, TZs, and IDs, there was a significant increase in sperm DNA integrity. Similarily, there was a decrease in abnormal sperm morphology in swim up and Percoll prepared sperm compared to neat samples. The Percoll density gradient centrifugation procedure yields sperm with an increase in sperm DNA integrity relative to swim up. Sperm DNA damage of TZs with both sperm preparation methods was significantly (P < 0.01) higher when compared to fertile and IDs. But the level of DNA damage was higher in IDs compared to fertile subjects. Compared to the other methods tested, the Percoll method yielded sperm with improved DNA integrity. In conjunction with semen analysis, the assessment of nuclear integrity improves the characterization of the semen sample and may be used as a tool for allocating the patients to specific assisted reproductive treatments.