Effects of Sperm Chromatin Integrity on Fertilization Rate and Embryo Quality Following Intracytoplasmic Sperm Injection

Sperm chromatin integrity has been being recognized as an important factor in male fertility. During normal fertilization, high quality sperm with intact chromatin are selected through natural selection in journey from vagina to fallopian tube. However, using Assisted Reproductive Techniques, particularly ICSI, the natural selection is bypassed. Therefore sperm with DNA breakage have the opportunity to fertilize the egg which may lead to decreased embryo quality and implantation rate. The aim of this study was to evaluate the effects of sperm chromatin integrity on ICSI outcomes. A total of 200 semen samples were collected from couples undergoing ICSI and were analyzed according to WHO criteria. Each sample was evaluated for sperm chromatin integrity using four cytochemical assays and semen processing by swim up method. The ICSI was carried out according to a long-term pituitary down-regulation protocol. The correlation between sperm parameters, sperm chromatin integrity and ICSI outcomes (fertilization rate and embryo quality) was examined. The mean number of oocyte, fertilization rate and cleavage embryos per cycles was 7.5±5.0, 74.06%±25 and 5.4±3.6, respectively. There was not significant correlation between the results of chromatin assays (AO, AB, TB, and CMA3) and fertilization outcomes following ICSI. The fertilization rate was significantly higher for a group with less than 10% chromatin abnormality (p<0.05). Sperm chromatin integrity is essential for successful fertilization, embryo development and normal pregnancy. A protamine deficiency appeared to affect fertilization rate and embryo quality. However, the presence of confounding factors such as selection of spermatozoa according to normal morphology may influence the effect of sperm chromatin status on ICSI outcomes.