Melatonin prevents postovulatory oocyte aging and promotes subsequent embryonic development in the pig

Abstract

Oxidative stress is known as a major contributing factor involved in oocyte aging, which negatively affects oocyte quality and development after fertilization. Melatonin is an effective free radical scavenger and its metabolites AFMK and AMK are powerful detoxifiers that eliminate free radicals. In this study, we used porcine oocytes to test the hypothesis that melatonin could scavenge free radicals produced during oocyte aging, thereby maintaining oocyte quality. We compared reactive oxygen species levels, apoptosis levels, mitochondrial membrane potential ratios, total glutathione contents and expression levels in fresh, aged and melatonin-treated aged porcine oocytes and observed the percentage of blastocyst formation following parthenogenetic activation. We found that melatonin could effectively maintain the morphology of oocytes observed in control oocytes, alleviate oxidative stress, markedly decrease early apoptosis levels, retard the decline of mitochondrial membrane potential and significantly promote subsequent embryonic development in oocytes aged for 24 hr in vitro. These results strongly suggest that melatonin can prevent postovulatory oocyte aging and promote subsequent embryonic development in the pig, which might find practical applications to control oocyte aging in other mammalian species including humans to maintain the quality of human oocytes when performing clinical assisted reproductive technology.

Melatonin supplementation during prolonged in vitro maturation improves the quality and development of poor‐quality porcine oocytes via anti‐oxidative and anti‐apoptotic effects

“…Our data showed that poor‐quality oocytes derived from prolonged IVM system significantly reduced mitochondrial membrane potential level, but this could be rescued by melatonin supplementation. Our result consistent with previous reports that melatonin had a significant function in keeping mitochondrial membrane potential (Liang et al, ; T. Wang et al, ).…”

“…For example, in pig (Do et al, ) or cattle (Zhao et al, ), melatonin can significantly reduce apoptosis index in oocytes relative to untreated oocytes. In the current study, results of the TUNEL assay showed that prolonged IVM culture time (52 hr) induced more apoptosis than non‐prolonged IVM, which agreed with previously reports that the increase of apoptosis index was observed in oocytes after extended IVM time (Liang et al, ; Lord, Nixon, Jones, & Aitken, ; T. Wang et al, ). However, melatonin supplementation significantly reduced apoptosis rate compared with melatonin‐free poor‐quality oocytes, suggesting that melatonin can protect poor‐quality oocytes subjected to longer IVM time culture by reducing apoptosis.…”

“…Recent evidence indicates that melatonin also has an antiapoptotic function in IVC conditions (Do et al, ; Li et al, ; Liang et al, ; T. Wang et al, ; Zhao et al, ). For example, in pig (Do et al, ) or cattle (Zhao et al, ), melatonin can significantly reduce apoptosis index in oocytes relative to untreated oocytes.…”

Melatonin regulates the activities of ovary and delays the fertility decline in female animals via MT1/AMPK pathway

“…In addition, the intracellular ROS of the oocytes treated with melatonin in vitro was lower than that in nontreated oocytes. The melatonin treatment also maintained ∆Ψm in the oocytes cultured in vitro condition, which is consistent with the results from the study using porcine oocytes . Antioxidant treatment is one of the mechanisms to combat the oxidative stress in organisms.…”

Allicin protects porcine oocytes against damage during aging in vitro

“…The level of apoptosis increases in a time‐dependent manner during oocyte aging (Wang et al, ). Hence, we investigated the extent of apoptosis by monitoring the expression levels of apoptosis‐related genes.…”