Impact of hydrogen peroxide-driven Fenton reaction on mouse oocyte quality

Here we show that hydroxyl radical ^(•OH) generated through the Fenton reaction alters metaphase-II mouse oocyte microtubules (MT) and chromosomal alignment (CH). Metaphase-II mouse oocytes, obtained commercially, were grouped as follows: control, hydrogen peroxide (H₂O ₂), Fe(II), and combined (Fe(II) +H₂O₂) treatments. After 7-10 min of incubation at 37 °C, MT and CH were evaluated on fixed and stained oocytes and scored by two blinded observers. Pearson χ² test and Fisher exact test were used to compare outcomes between controls and treated groups and also among the treated groups. Our results showed that poor scores for MT and CH increased significantly in oocytes treated with a combination of H₂O₂ and Fe(II) (p<0.001); oocytes treated with H₂O₂ alone or Fe(II) alone showed no or few changes compared to control. Comparison of oocyte groups that received increasing concentrations of H₂O₂ and a fixed amount of Fe(II) showed that 70-80% demonstrated poor scores in both MT and CH when pretreated with 5 μM H₂O₂, and this increased up to 90-100% when treated with 10-20 μM H₂O ₂. Hydroxyl radical generated by H₂O₂-driven Fenton reaction deteriorates the metaphase-II mouse oocyte spindle and CH alignment, which is thought to be a potential cause of poor oocyte quality. Thus, free iron and/or ROS scavengers could attenuate the ^•OH- mediated spindle and chromosomal damage, thereby serving as a possible approach for further examination as a therapeutic option in inflammatory states.