The possible role of the SIRT1 enzyme in oxidative stress and spindle assembly in bovine oocytes—a large animal model for reproductive ageing

Chromosomal defects and oxidative stress become much more prevalent with advancing maternal age and are considered the major factors responsible for the increased incidence of miscarriage and birth defects in women over 35 year of age. However, mechanisms that modulate the meiotic apparatus remain to be discovered. The SIRT1 enzyme deacetylates a spectrum of transcriptional regulators and can be activated by resveratrol. Therefore, the goal of our large animal model was to examine, how the SIRT1 enzyme influences oxidative stress and spindle assembly in bovine oocytes from donors of different age. COCs of pre-pubertal (5–6 months old), adult cows (2nd lactation) and aged cows (10th lactation) were collected by Ovum Pick-up twice a week. Medium for IVM and IVF was supplemented with 2 μM Resveratrol® (Sigma-Aldrich, Buchs, Switzerland). Standard lab protocol was used as control. SIRT1 activity was measured using a fluorometric SIRT1 activator kit (BioVision, Milpitas, USA). The spindle assembly of oocytes was analysed by fluorescence immunostaining under a confocal microscope (LSM510, Zeiss, Germany). Reactive oxygen species (ROS) levels were assessed in oocytes using Dihydroethidium (Thermo Fisher, Bonn, Germany). In total 238 COCs of all three donor groups were analysed. A 4-fold increase of SIRT1 enzyme activity (4 independent replicates) could be detected in oocytes of resveratrol treated groups compared to the ones out of the control groups. A high frequency of spindle defects and chromosome disorganization were observed in the oocytes of the untreated aged donor group (35.5 ± 8.7%) and a lower frequency in the resveratrol treated aged donor group (9.6 ± 3.8%, respectively 4 independent replicates). The ROS levels (12 independent replicates) were significantly lower (121 ± 34 FIU) in the resveratrol treated samples than in those of the control group (865 ± 45 FIU, p ≤ 0.05). In conclusion, these results indicate that resveratrol is able to influence SIRT1 enzyme activity, the redox status and spindle formation in bovine oocytes of different maternal age. In this regard, SIRT1 could be a marker for reproductive ageing and useful for further understanding of human infertility caused by ageing.