DNA fragmentation of sperm subpopulations with different head morphology. implications for ICSI treatment

Abstract

The use of sperm with damaged genome may have a negative effect on the outcome of assisted reproductive technologies. In ICSI, typically only morphologically normal sperm will be chosen to be injected. Generally, sperm DNA fragmentation (DNAf) is evaluated in the whole sperm population. The objectives of this study were to evaluate the presence of DNAf in spermatozoa with different morphology patterns, and to define if the evaluation of DNAf in the total sperm population may impact ICSI outcome. Descriptive study. 24 semen samples from infertile men with more than 10% of total sperm with fragmented DNA were studied. Highly motile sperm were obtained by swim-up. Sperm DNAf was evaluated by TUNEL assay. Simultaneous examination of sperm morphology and DNAf in the same cell were performed using phase contrast and TUNEL respectively. At least 500 cells were evaluated in two droplets per sample. The percentages of different sperm head forms showing DNAf was recorded according to the following classification: normal (N), amorphous (A), pyriform (P), vacuolated (V), tapered (T), small (S), and round (R). 7595 cells with fragmented DNA were evaluated. The percentage of different sperm head forms with DNA fragmentation can be summarized as follows: 45.3% A, 28.5% V, 12.0% S, 7.5% R, 2.8% T, 2.0% P and 1.9% N. 31% of morphologically normal sperm showed fragmented DNA in a range between 3 to 62%. Our data indicate that the majority of the cells showing DNAf have abnormal forms. The most common head abnormalities were A and V. Nevertheless, a variable proportion of N cells showed DNA damage. In ICSI only normal sperm will be injected, consequently the evaluation of abnormal cells could be unnecessary and would provide mistaken information. Therefore, we propose that the evaluation of DNA integrity in morphologically normal spermatozoa is a better approach to evaluate the impact of sperm DNAf on ICSI outcome than the assessment of the total sperm population.