# Regulatory of Oleuropein on the In Vitro Maturation of Oocytes and the Development of Parthenogenetic Embryos in Sheep

## TL;DR

Oleuropein improves sheep oocyte maturation and embryo development by reducing oxidative stress and enhancing antioxidant activity.

## Contribution

This study demonstrates that oleuropein optimally enhances sheep oocyte maturation and embryo development through antioxidant mechanisms.

## Key findings

- 20 μM oleuropein increases oocyte maturation rate, while 30 μM improves blastocyst formation.
- Oleuropein reduces ROS levels and increases glutathione and mitochondrial membrane potential.
- Oleuropein elevates antioxidant and anti-apoptotic gene expression and OCT4 in embryos.

## Abstract

Oleuropein, as an antioxidant, can alleviate the oxidative stress phenomenon during the in vitro culture of sheep oocytes and early embryos, thereby improving embryo quality. This study found that the appropriate addition of oleuropein can increase the maturation rate of oocytes and promote the development of early embryos. Optimizing the embryo culture system is important for improving the success rate and quality of early embryo development.

Oleuropein (OLE), as the main effective active component in olive leaves, is a natural cyclic ether terpene polyphenolic compound found in plants of the genus Olea. It has antioxidant, anti-inflammatory and anti-apoptotic properties, and can reduce damage caused by reactive oxygen species. These characteristics indicate that it can enhance the maturation rate of oocytes and the developmental capacity of embryos—two key indicators in animal breeding. This study evaluated the effects of OLE on the in vitro maturation and early embryonic development of sheep oocytes. 20 μM OLE has the best promoting effect on the maturation rate of oocytes, and 30 μM OLE has the best increasing effect on the blastocyst rate. Compared with the control group, glutathione (GSH) level and mitochondrial membrane potential (MMP) level were significantly increased, ROS level was significantly decreased, the expression of antioxidant genes SOD1 and GPX3 was significantly elevated, and the expression of anti-apoptotic gene BCL2 was significantly elevated in the experimental group. In addition, during the in vitro development stage of early embryos, the expression level of the embryo development-related gene OCT4 significantly increased. The study has shown that OLE can effectively alleviate oxidative stress during in vitro culture, increase oocyte maturation rate and promote embryo development.