Impacto del estrés oxidativo en la dinámica de fragmentación del ADN espermático

Introduction

One of the additional tests for the diagnosis of male infertility is the study of sperm DNA fragmentation. One reason that may explain the damage of the DNA molecule is oxidative stress. This is caused by free oxygen radicals, among which is the superoxide anion (O₂^{. −}).

Objective

To measure the oxidative stress excess in semen samples and the impact on sperm DNA fragmentation.

Material and methods

A total of 78 samples from patients and donors were evaluated. Each one was classified into one of four levels (EO1, EO2, EO3 or EO4) according to the level of oxidative stress found using the NBT-test (detection of superoxide anion). Sperm concentration and DNA fragmentation index (at t0, t2, t6, and t24 h during incubation at 37 °C) were calculated for each sample using the sperm chromatin dispersion test (SCD).

Results

There were no significant differences between results of the four groups in the baseline DNA fragmentation index (t0 h). When the dynamic process was studied, an increase in the fragmentation index could be observed (the first two hours remained stable). This increase varied depending on the levels of oxidative stress. The DNA fragmentation index (DFI) remained stable for less time as the levels of oxidative stress increased. There is a particular time where the velocity becomes the same in all the groups.

Discussion

No significant correlation was found between the levels of oxidative stress and the baseline DFI. However, the behaviour of the fragmentation dynamics of the samples varied depending on the levels of oxidative stress.

Conclusions

These results enhance the importance of understanding DNA fragmentation from a dynamic point of view rather than a static process of the baseline DFI. Samples with higher levels of oxidative stress showed a rapid increase in their DFI during the first hours after ejaculation compared with the stability shown in the rest of the samples.