DNA fragmentation in spermatozoa, implications for failed fertilization in intracytoplasmic sperm injection

grantor: University of TorontoObjectives. To correlate the percentage of sperm with damaged DNA with semen analysis parameters and with fertilization rates in ICSI. To evaluate the effect of exogenously generated reactive oxygen species (ROS) on the integrity of the DNA of human spermatozoa and the effectiveness of pretreatment with antioxidants to reduce DNA damage. Design. Semen samples were collected from men in the ICSI program at a tertiary-care centre. DNA fragmentation was determined using the method of TUNEL. Reactive oxygen species was generated in washed sperm samples in an attempt to cause DNA fragmentation. Antioxidants were added to 17 samples to determine if DNA damage could be prevented. Results. A negative correlation was found between the percentage of DNA fragmentation and motility and morphology of the ejaculated sperm. A significant negative association was also found between the percentage of sperm with DNA fragmentation and fertilization rate. When the unfertilized oocytes were analyzed, we determined that almost 25% contained sperm with fragmented DNA and 25% of the sample group demonstrated fragmented oocyte DNA. Lastly, we established that exogenous ROS can cause an almost fourfold increase in DNA damage which can be prevented by the addition of antioxidants. Conclusions. Since poor quality semen samples are the indication for ICSI, our results suggest that there is a greater likelihood that some sperm selected for injection despite appearing normal, contained fragmented DNA.M.Sc