Melatonin Improves Parthenogenetic Development of Vitrified⁻Warmed Mouse Oocytes Potentially by Promoting G1/S Cell Cycle Progression.

Bo Pan,Qingyong Meng,Guangbin Zhou,Hongbing Han,Haoxuan Yang,Guoshi Liu,Zhenzheng Wu,Izhar Qazi

doi:10.3390/ijms19124029

Abstract

This study aimed to investigate the effect of melatonin on the cell cycle of parthenogenetic embryos derived from vitrified mouse metaphase II (MII) oocytes. Fresh oocytes were randomly allocated into three groups: untreated (control), or vitrified by the open-pulled straw method without (Vitrification group) or with melatonin (MT) supplementation (Vitrification + MT group). After warming, oocytes were parthenogenetically activated and cultured in vitro, then the percentage of embryos in the G1/S phase, the levels of reactive oxygen species (ROS) and glutathione (GSH), and the mRNA expression of cell cycle-related genes (P53, P21 and E2F1) in zygotes and their subsequent developmental potential in vitro were evaluated. The results showed that the vitrification/warming procedures significantly decreased the frequency of the S phase, markedly increased ROS and GSH levels and the expression of P53 and P21 genes, and decreased E2F1 expression in zygotes at the G1 stage and their subsequent development into 2-cell and blastocyst stage embryos. However, when 10−9 mol/L MT was administered for the whole duration of the experiment, the frequency of the S phase in zygotes was significantly increased, while the other indicators were also significantly improved and almost recovered to the normal levels shown in the control. Thus, MT might promote G1-to-S progression via regulation of ROS, GSH and cell cycle-related genes, potentially increasing the parthenogenetic development ability of vitrified–warmed mouse oocytes.

Highlights

Oocyte cryopreservation, an adjunct to artificial assisted reproductive technologies, has been widely applied in the fields of medicine, agriculture and scientific research [1,2,3,4]
This was confirmed by the fact that the parthenogenetic development of mouse oocytes into blastocysts significantly decreased from 66.67% to 33.61% after vitrification
In the present study we tried to elucidate the underlying mechanism by which melatonin promotes the development of vitrified–warmed mouse oocytes in vitro potentially by regulating cell cycle progression, expression of cell cycle-related genes and redox homeostasis

Summary

Introduction

An adjunct to artificial assisted reproductive technologies, has been widely applied in the fields of medicine, agriculture and scientific research [1,2,3,4]. The decreased developmental potential due to oocyte cryopreservation may inevitably result from the alteration of intracellular levels of reactive oxygen species (ROS) [14] or glutathione (GSH) [15], and/or gene expression [16,17,18]. After oocytes are subjected to vitrification and warming, ROS levels are generally increased [13,14] and, GSH levels tend to decline [15,26,27]. In such situations, redox homeostasis would be perturbed, potentially weakening the quality of oocytes and reducing their developmental competence [28]. Taking the foregoing facts into consideration, it is worthwhile to further elucidate how ROS and GSH levels are altered when oocytes are subjected to the vigorous procedures of cryopreservation and whether these induced changes affect the transition of cell cycle progression in parthenogenetic zygotes derived from vitrified–warmed mouse oocytes

Objectives

Methods

Findings

Conclusion