Abstract

We investigated the ability of reactive oxygen species (ROS), such as hydrogen peroxide (H2O2), hydroxyl radical (OH),

and hypochlorous acid (HOCl), to overcome the defensive capacity of cumulus cells and elucidate the mechanism through

which ROS differentially deteriorate oocyte quality. Metaphase II mouse oocytes with (n ¼ 1634) and without cumulus cells

(n ¼ 1633) were treated with increasing concentration of ROS, and the deterioration in oocyte quality was assessed by the

changes in the microtubule morphology and chromosomal alignment. Oocyte and cumulus cell viability and cumulus cell

number were assessed by indirect immunofluorescence, staining of gap junction protein, and trypan blue staining. The

treated oocytes showed decreased quality as a function of increasing concentrations of ROS when compared to controls.

Cumulus cells show protection against H2O2 and OH insult at lower concentrations, but this protection was lost at higher

concentrations (>50 mmol/L). At higher H2O2 concentrations, treatment dramatically influenced the cumulus cell number

and viability with resulting reduction in the antioxidant capacity making the oocyte more susceptible to oxidative damage.

However, cumulus cells offered no significant protection against HOCl at any concentration used. In all circumstances in

which cumulus cells did not offer protection to the oocyte, both cumulus cell number and viability were decreased.

Therefore, the deterioration in oocyte quality may be caused by one or more of the following: a decrease in the antioxidant

machinery by the loss of cumulus cells, the lack of scavengers for specific ROS, and/or the ability of the ROS to overcome

these defenses.

Title

Reproductive Sciences

Publisher

SAGE

Publisher Country

United States of America

Indexing

Thomson Reuters

Impact Factor

2.429

Publication Type

Prtinted only

Volume

23

Year

2016

Pages

1-11