Male obesity and ageing have been shown to impair male fertility. One common proposed mechanism is an increase in harmful ROS levels that can cause DNA damage in the sperm, resulting in reduced pregnancy rates and increases in miscarriage. ART treatments provide an opportunity to reduce sperm ROS during sperm washing and isolation in vitro. Idebenone is a synthetic analog of co-enzyme Q10 that is more readily dissolved in culture media and crosses the mitochondrial membrane, targeting mitochondrial ROS. The aim of this study was to determine if addition of Idebenone to the sperm preparation culture media could reduce ROS levels in human and mouse sperm.
Human sperm (n=6) from obese males or mouse sperm (n=5) with elevated ROS levels were incubated in GIVF medium (control) or GIVF medium supplemented with 5µM Idebenone for 2h. Mitochondrial ROS was measured by incubation with MitoSOX and assessed using flow cytometry of live sperm which were identified by exclusion of SYTOX Green. Fertilization in the mouse was performed by co-incubation of sperm with cumulus-enclosed oocytes for 4h and successful fertilization assessed by the presence of 2-cells the following morning. Statistical differences between treatments where assessed by generalised linear modelling using SPSS.
Incubation with Idebenone resulted in a significant decrease in sperm mitochondrial ROS levels, with a 16% decrease in the human (control 1392±15, Idebenone 1195±14, P<0.01) and 13% decrease in mouse (control 687±11, Idebenone 596±10). In the mouse, fertilization rates were increased when the sperm was incubated with 5µM Idebenone prior to insemination (P<0.05).
This study suggests that short term incubation with the antioxidant Idebenone in vitro can reduce sperm mitochondrial ROS, in samples that have elevated baseline ROS. In the mouse, this translated to improvements in fertilization rates. Further studies need to establish if this translates to similar improvements in the human.