Oligozoospermic infertile sperm with high ROS are more prone to epigenetic alterations

Introduction Oxidative stress has been found to play a critical role in sperm quality and function. In this study, we asked if oligozoospermic samples with high ROS display a higher degree of methylation alterations in comparison to normozoospermic samples. Methods We investigated genome-wide DNA methylation in normozoospermic (presumptive fertile) and oligozoospermic infertile samples with high and low ROS levels. Fifty samples each for oligozoospermia and normozoospermia were analyzed for their ROS levels. Two samples each in the normozoospermic low ROS, normozoospermic high ROS, oligozoospermic low ROS and oligozoospermic high ROS categories were selected for genome-wide DNA methylation profiling. Results and discussion A comparison between oligozoospermic and normozoospermic samples showed a low number of differentially methylated genes (about 100). The normozoospermic high ROS group in comparison to the normozoospermic low ROS group showed a moderate number of differentially methylated genes (538). On the other hand, oligozoospermic high ROS versus oligozoospermic low ROS comparison showed the highest number of genes (1,755) to be differentially methylated, of which a majority displayed hypomethylation. These findings underscore the vulnerability of oligozoospermic sperm to epigenetic disruptions induced by oxidative stress. We conclude that oligozoospermic samples with high ROS carry a high degree of methylation alterations.