Antioxidants retard the ageing of mouse oocytes

The aim of the present study was to verify the effects of heavy metal coupling agents (sodium citrate and EDTA) and antioxidants (acetyl carnitine and lipoic acid) on the number of oocytes, as well as the ageing of mitochondria, chromosomes and spindles in mice. C57BL/6 female mice were randomly classified into four groups (n=12 per group): i) Heavy metal coupling agent; ii) antioxidant; iii) mixed group; and iv) the normal control group. For the treatments, heavy metal coupling agents and antioxidants were added to the drinking water provided to the mice. Following 3, 6, 9 and 12 months of treatment, the number of oocytes and mitochondrial membrane potential were determined, and chromosome and spindle structures were observed. With increasing age, the experimental mice in the four groups showed significantly decreased numbers of oocytes, reduced mitochondrial activity, and increased rates of spindle and chromosome abnormalities, which indicated age-induced ageing of mouse oocytes; thus, a mouse ageing oocyte model had been successfully established. For mice of the same age, more oocytes, higher mitochondrial activity, and lower spindle and chromosome malformation rates were detected in the antioxidant and mixed groups when compared with the normal control groups. Furthermore, no significant difference in the number of oocytes, mitochondrial activity or chromosome malformation rates was observed between the heavy metal coupling agent group and normal control group, which was possibly due to less metal being absorbed during the breeding process. Therefore, the results demonstrated that the antioxidants acetyl carnitine and lipoic acid may serve a role in delaying oocyte ageing.