Resumen de Resveratrol supplementation during in vitro maturation: effect on oocyte in species of veterinary interest
The quality of oocytes plays a pivotal role in determining in vitro embryo production (IVEP) outcomes. Different intrinsic and extrinsic factors can impair the quality of mammalian oocytes, affecting their developmental competence.
The aim of the study was to evaluate the effect of supplementation of resveratrol, a natural antioxidant, during in vitro maturation (IVM) on the quality of oocytes in species of veterinary interest (domestic cat, prepubertal goats and sheep).
Three studies were performed to test the potential beneficial influence of resveratrol to improve the in vitro developmental competence of poor quality oocytes such as under sub-optimal condition or with low developmental competence.
Specifically, the effect of resveratrol addition to the IVM medium was tested on:
-STUDY I: IVEP from domestic cat oocytes retrieved from ovaries stored at 4°C for 24 and 48h.
Oocytes retrieved from stored ovaries for 24 and 48h were IVM with or without 5μM resveratrol. Meiotic competence, intracellular levels of reactive oxygen species (ROS) and glutathione (GSH), blastocyst yield and the blastocyst cell number were evaluated. The results showed that resveratrol treatment had not effect on the meiotic competence of the oocytes. Resveratrol groups had lower (P<0.05) intracellular ROS levels and higher (P<0.05) GSH content compared to untreated oocytes, both at 24 and 48h. Moreover, resveratrol supplementation significantly increased blastocyst yield in 48h group and improves blastocyst cells number in both groups.
-STUDY II: IVEP from prepubertal goat oocytes selected by brilliant cresyl blue (BCB) staining.
Oocytes were classified by BCB staining as BCB+ (fully grown oocytes ) or BCB- (growing oocytes) and IVM with or without 1μM resveratrol. ROS and GSH levels, mitochondrial activity and distribution and ATP content were analyzed in metaphase II oocytes (MII). After in vitro fertilization (IVF), the blastocyst rate and the blastocyst quality were assessed. No differences were found in ROS levels, ATP content and mitochondrial activity among groups. GSH levels were significantly higher in both BCB groups treated with resveratrol than their respective controls. Oocytes treated with resveratrol showed a higher proportion of clustered active mitochondria than control groups. The development to blastocyst stage was significantly higher in BCB+ oocytes matured with resveratrol compared with the other groups. No differences were observed in blastocyst quality among groups.
STUDY III: In vitro fertilization outcome of prepubertal sheep oocytes under cadmium exposure.
Oocytes were expose to 2μM cadmium (Cd) and IVM in the presence of different concentration of resveratrol: 0μM (Cd), 1 μM (Cd-Resv1μM) and 2 μM (Cd-Resv2μM). Oocytes matured in absence of Cd were used as control. Fertilization outcomes, cortical granules (CGs) and mitochondria distribution, mitochondria activity and ROS level were evaluated. Oocytes of control, Cd-Resv1μM and Cd-Resv2μM groups had higher normal fertilization compared to Cd group (P<0.05). The percentage of MII oocytes with CGs distributed in the cortex of the oocytes was higher (P<0.05) in control and Cd-Resv1μM groups than Cd group. The percentage of MII oocytes that exhibited a homogeneous mitochondria distribution throughout the cytoplasm was higher in control, Cd-Resv 1μM and Cd-Resv2μM groups than Cd group (P<0.05). Lower activity (P<0.05) of mitochondria was recorded in control and Cd-Resv 1μM oocytes compared to Cd oocytes. The intracellular ROS levels were lower in control, Cd-Resv1μM and Cd-Resv2μM groups than Cd group.
Taking all these results into account, we conclude that resveratrol supplementation during IVM constitutes a useful strategy to improve oocyte quality and IVEP outcome in species of veterinary interest. The mechanism underlying resveratrol effects included the regulation of bioenergetic/redox status of the oocytes by the modulation of ROS and GSH levels and mitochondria function and the distribution of cytoplasmic organelles.
