Analysis of antioxidant activity in commercial IVF media

What is the biological effectiveness and source of antioxidant activity in commercial IVF media?

Antioxidant activity, defined by the ability of individual culture media to scavenge hydrogen peroxide, free radicals and lipid hydroperoxide, was assessed over 24 h in the presence and absence of spermatozoa. Motility, DNA integrity and mitochondrial reactive oxygen species (ROS) generation were investigated. Protein concentration, identification and activity were studied using the DC protein assay, sodium dodecyl sulphate polyacrylamide gel electrophoresis and thiol quantification, respectively. Molecular filtration was employed to determine the role of albumin in supporting sperm function.

The results revealed highly significant differences between media in their capacity to support sperm motility and DNA integrity. Media that optimally supported sperm function generally possessed high levels of antioxidant activity. Moreover, spermatozoa were shown to consume antioxidant equivalents from these media, particularly with respect to their hydrogen peroxide scavenging activity. The major antioxidant present in these commercial preparations was found to be albumin. When albumin was selectively removed, the abilities of these media to support sperm motility, control mitochondrial ROS generation and suppress DNA damage were lost. However, if the albumin content of these media was subsequently restored, all these supportive properties were recovered. Thiol oxidation and the binding of cytotoxic metabolites were central to albumin's protective action.

These studies emphasize the importance of antioxidant activity in supporting sperm function in vitro. As albumin is the only antioxidant available to these cells in current media formulations, an opportunity exists to optimize how such protection is delivered in the future.