The role of DNA strand breaks in human spermatozoa used for IVF and ICSI

Background: The objective of this study was to determine the incidence of spermatozoa with DNA strand breaks in four clinically different groups of infertile couples, and to correlate DNA damage with other semen analysis parameters, as well as fertilization rates and IVF outcome. Methods. One group consisted of 75 men where the female partners had a tubal obstruction, Group A. Fifty sperm samples were collected from men in unexplained infertile couples, Group B. Fifty men with oligozoospermia and IVF made up Group C. Finally, 61 men with oligozoospermia and where ICSI was performed made up Group D. Sperm samples were assessed according to the WHO manual and for the presence of DNA strand breaks in spermatozoa. The study was blinded for the technician involved in the assessment of DNA strand breaks. IVF was carried out according to a long down regulation protocol using GnRH, FSH and hCG. Embryos were transferred on day 2 after fertilization with a maximum of three embryos. Results. This study demonstrated a negative correlation between the proportion of spermatozoa having DNA strand breaks and the proportion of oocytes fertilized after IVF (p<0.01). Furthermore, the number of spermatozoa with DNA strand breaks was important for the pregnancy rate in the group of unexplained infertile couples. After ICSI no association was found between spermatozoa with DNA strand breaks and fertilization rates (p>0.05). Conclusion. DNA strand breaks in human spermatozoa impairs fertilization in both unexplained infertile couples and those with oligozoospermia and IVF. However, after ICSI, this impact of DNA strand breaks were not seen. This creates a specific indication and treatment for this new diagnosed group of otherwise unexplained infertile men.