Melatonin improves the effect of cryopreservation on human oocytes by suppressing oxidative stress and maintaining the permeability of the oolemma

Abstract

Cryopreservation causes cryoinjury to oocytes and impairs their developmental competence. Melatonin (MLT) can improve the effect of cryopreservation in animal oocytes. However, no such studies on human oocytes have been reported. In this study, collected in vitro‐matured human oocytes were randomly divided into the following groups: fresh group, MLT‐treated cryopreservation (MC) group, and no‐MLT‐treated cryopreservation (NC) group. After vitrification and warming, viable oocytes from these three groups were assessed for their mitochondrial function, ultrastructure, permeability of oolemma, early apoptosis, developmental competence, and cryotolerance‐related gene expression. First, fluorescence staining results revealed that oocytes from the 10−9 M subgroup showed the lowest intracellular reactive oxygen species and Ca2+ levels and highest mitochondrial membrane potential among the MC subgroups (10−11, 10−9, 10−7, and 10−5 M). In subsequent experiments, oocytes from the 10−9 M‐MC group were observed to maintain the normal ultrastructural features and the permeability of the oolemma. Compared with those of the oocytes in the NC group, the early apoptosis rate significantly decreased (P < .01), whereas both the high‐quality cleavage embryo and blastocyst rates significantly increased (both P < .05) in the oocytes of the 10−9 M‐MC group. Finally, single‐cell RNA sequencing and immunofluorescence results revealed that aquaporin (AQP) 1/2/11 gene expression and AQP1 protein expression were upregulated in the MC group. Therefore, these results suggest that MLT can improve the effect of cryopreservation on human oocytes by suppressing oxidative stress and maintaining the permeability of the oolemma.

Melatonin Promotes In Vitro Maturation of Vitrified-Warmed Mouse Germinal Vesicle Oocytes, Potentially by Reducing Oxidative Stress through the Nrf2 Pathway

“…The cryopreservation of mouse [ 27 ], bovine [ 50 ], pig [ 51 ], and human oocytes [ 52 ] increases oxidative stress, although exogenous melatonin reduce oxidative stress in vitrified-warmed oocytes [ 30 , 53 ]. The Nrf2 signaling pathway is an important intracellular antioxidant signaling pathway, critical for maintaining redox balance [ 31 , 54 ]. Melatonin is a regulatory molecule of the Nrf2 protein [ 18 ].…”

“…Cryopreservation can destroy some proteins in oocytes, e.g., porcine Nrf2, human aquaporin 1 (APQ1) [ 31 ], goat CDK1 [ 65 ], and mouse Mad2 [ 66 ], etc. After the vitrification of porcine COC oocytes, proteomics analysis revealed that 59 proteins were down-regulated [ 67 ].…”

“…Through the Nrf2 signaling pathway, melatonin, can antagonize oxidative injury induced by manganese (Mn) in the striatum of mice [ 19 ]; protect against early brain injury in a subarachnoid hemorrhage model in mice [ 20 ]; treat experimental allergic encephalomyelitis in mice [ 21 ]; attenuate acute kidney ischemia/reperfusion injury in diabetic rats [ 22 ]; prevent lipopolysaccharide- (LPS) induced epithelial–mesenchymal transition in human alveolar epithelial cells [ 23 ]; promote porcine embryo development [ 24 ]; and inhibit oxidative stress and apoptosis in cryopreserved ovarian tissues [ 25 ]. Although previously it has been shown that melatonin can reduce excessive ROS in oocytes induced by cryopreservation in mice [ 26 , 27 , 28 , 29 ], bovine animals [ 30 ], and humans [ 31 ], the underlying mechanism through which melatonin might regulate the Nrf2 signaling pathway remains to be elucidated.…”

Melatonin for the prevention of fetal injury associated with intrauterine inflammation

“…18,[51][52][53] Furthermore, studies, where melatonin was administered to improve the quality of the embryo and increase the implantation rate in in vitro fertilization and embryo transfer (IVF-ET) pregnancies, have been conducted in humans for many years; however, there have been no reports of side effects to date. [54][55][56][57] There have also been no reports of melatonin causing side effects in either adults or neonates. Many animal studies conducted on pregnant subjects and researches performed in human neonates suggest that the melatonin administration might be safe in human pregnancy as well.…”

Melatonin supplementation in the culture medium rescues impaired glucose metabolism in IVF mice offspring

“…24 In human studies, oral administration of melatonin improved oocyte quality, and increased the number of mature eggs, the rate of high-quality embryos and clinical pregnancy rate. 17,[25][26][27][28] Melatonin supplementation in the culture medium (mIVF) reversed vascular dysfunction and arterial hypertension in adult IVF mice. 29 Therefore, we hypothesized that mIVF might reverse impaired glucose metabolism in IVF mice offspring.…”