Melatonin promotes human oocyte maturation and early embryo development by enhancing clathrin-mediated endocytosis

Melatonin supplementation does not improve ovine pre- or post-hatching development in vitro

Melatonin plays a crucial role in the regulation of reproductive seasonality in sheep. Melatonin supplementation has been widely used both in vivo to increase fertility and prolificacy, and in vitro during oocyte maturation, fertilization, and embryo culture. However, its effects have only been assessed in vitro up to the hatched blastocyst stage in conventional embryo culture systems. This study aimed to evaluate the effects of melatonin supplementation from oocyte in vitro maturation (IVM) through post-hatching embryonic stages in vitro on the development of the first three embryonic lineages. Supplementation with melatonin at 10-8 or 10-6 M during IVM, in vitro fertilization (IVF), and in vitro culture (IVC) did not affect cleavage and blastocyst rates at day (D) 8, nor embryo survival and growth at D12. While hypoblast development was not affected, epiblast survival was reduced in D12 embryos treated with 10-6 M melatonin from the blastocyst stage onward. In conclusion, melatonin supplementation did not show a clear beneficial effect on ovine in vitro embryo production or lineage development during post-hatching embryo culture.

Melatonin Rescues Hyperacetylation of Liver and Impaired Enzymatic Activities of Mitochondrial in IVF Offspring

Increased risks of obesity and abnormal glucose metabolism were observed in IVF offspring. However, the underlying molecular mechanism was still unclear. As an important post-translational modification (PTM), lysine acetylation changed with the changes in the metabolic environment and usually occurred on metabolic enzymes to regulate metabolic pathways and enzyme activities and participated in the regulation of downstream metabolites. In our previous study, we proved that supplementation of melatonin in the culture medium improved obesity and metabolic dysfunction in IVF mice. In this study, we further demonstrated that elevated levels of protein acetylation in hepatic cells might be associated with impaired glucose metabolism in IVF offspring, and melatonin could significantly reduce the acetylation level and improve the adverse phenotype of IVF mice. More importantly, we discovered that the supplementation of melatonin in the culture medium during in vitro fertilization significantly enhanced the activity of enzymes, especially citrate synthase (CS) and isocitrate dehydrogenase (IDH) which were involved in tricarboxylic acid recycling and played critical roles in glucose metabolism of liver. Thus, our findings elucidated a new perspective on the mechanisms of metabolic reprogramming of IVF mice.

Exploring melatonin's multifaceted role in female reproductive health: From follicular development to lactation and its therapeutic potential in obstetric syndromes

BACKGROUND

Melatonin is mainly secreted by the pineal gland during darkness and regulates biological rhythms through its receptors in the suprachiasmatic nucleus of the hypothalamus. In addition, it also plays a role in the reproductive system by affecting the function of the hypothalamic-pituitary-gonadal axis, and by acting as a free radical scavenger thus contributing to the maintenance of the optimal physiological state of the gonads. Besides, melatonin can freely cross the placenta to influence fetal development. However, there is still a lack of overall understanding of the role of melatonin in the reproductive cycle of female mammals.

AIM OF REVIEW

Here we focus the role of melatonin in female reproduction from follicular development to delivery as well as the relationship between melatonin and lactation. We further summarize the potential role of melatonin in the treatment of preeclampsia, polycystic ovary syndrome, endometriosis, and ovarian aging.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Understanding the physiological role of melatonin in female reproductive processes will contribute to the advancement of human fertility and reproductive medicine research.

Ovarian Endometrioma Disrupts Oocyte-Cumulus Communication and Mitochondrial Function, With Melatonin Mitigating the Effects

Ovarian endometrioma (OEM), a particularly severe form of endometriosis, is an oestrogen-dependent condition often associated with pain and infertility. The mechanisms by which OEM impairs fertility, particularly through its direct impact on oocyte-cumulus cell (CC) communication and related pathways, remain poorly understood. This study investigates the impact of OEM on oocyte-CC communication and explores melatonin's therapeutic potential. We used a mouse model of OEM and employed ovarian transcriptome and gene set enrichment analyses to identify disrupted gene pathways, alongside phalloidin staining for cytoskeletal analysis, gap junction coupling analysis for intercellular communication, and mitochondrial function assessments for cellular metabolism. Our results showed that OEM significantly impairs steroidogenesis and cumulus cell function, leading to increased apoptosis, disrupted transzonal projections (TZPs), and impaired antioxidant transfer to oocytes. This culminates in oxidative stress, mitochondrial dysfunction, and compromised ATP production. OEM oocytes also exhibited severe abnormalities, including DNA damage, maturation defects, spindle assembly disruptions, and increased aneuploidy. This study identifies disrupted TZPs as a key pathological feature in OEM and highlights melatonin's potential to restore intercellular communication, mitigate oxidative damage, and improve reproductive outcomes.

BDNF secreted by mesenchymal stem cells improves aged oocyte quality and development potential by activating the ERK1/2 pathway

BACKGROUND

Reduced oocyte quality is a key factor in age-related fertility decline, and there are no effective treatments available. The secretome of mesenchymal stem cells (MSC-sec) contains various bioactive factors and has the potential to improve oocyte quality. This study aimed to investigate the effective component and molecular mechanism of MSC-sec involved in improving oocyte quality from aged mice and humans.

METHODS

Immunofluorescence and chromosome spread were performed to investigate the effects of secretome from human umbilical cord-MSC on spindle assembly and aneuploidy in aged mouse oocytes. Brain-derived neurotrophic factor (BDNF) and its neutralization antibody was supplemented in both in vitro and in vivo experiments to verify the effective component in MSC-sec. RNA-seq analysis was used to reveal the alterations in maternal mRNA degradation in aged mouse oocytes after MSC-sec treatment. In vitro culture of oocytes from aged women was also used to verify the effectiveness of BDNF in improving oocyte quality.

RESULTS

MSC-sec treatment significantly increased first polar body emission, improved spindle assembly, promoted maternal RNA degradation, and reduced aneuploidy rate in aged mouse oocytes. While the addition of BDNF neutralization antibody blocked the effects of MSC-sec, BDNF alone also increased the oocyte quality from aged mice. Mechanistically, both MSC-sec and BDNF rescued the quality of aged mouse oocytes by activating the ERK1/2 signaling pathway to increase the expression of DAZL and BTG4. In situ injection of MSC-sec or BDNF into aged mouse ovaries significantly improved oocyte quality and early embryonic development. Finally, we demonstrated that BDNF treatment increased both the fertilization rate and blastocyst formation rate of aged human oocytes.

CONCLUSION

These findings demonstrate that BDNF secreted by mesenchymal stem cells can improve the quality and development potential of oocytes from both aged mice and humans by activating the ERK1/2 signaling pathway, suggesting that it has the potential to mitigate age-related declines in oocyte quality.

Stage-dependent changes in culture medium osmolality promote porcine oocyte maturation in vitro

Introduction

Early preimplantation embryos of mammals exhibit pronounced sensitivity to hyperosmotic conditions, which results in an embryonic developmental block. The reduction of medium osmolarity or the supplementation with organic osmolytes can eliminate this arrest. Therefore, cell volume homeostasis is essential for embryonic development in vitro. Oocytes become capable of independent volume regulation after detaching from the follicle microenvironment. Whether the efficiency and quality of oocyte maturation can be improved by optimizing cell volume regulation by adjusting the osmolality of the culture medium in the presence of the organic osmolyte of glycine remains to be determined.

Methods

The IVM of porcine oocytes was divided into two stages, i.e. the first 22 h as the first stage, and the last 22 h as the second stage. In the presence of 1 mM glycine, we adjusted the osmolality of the culture medium from low to high (290 mOsM for the first 22 h and 320 mOsM thereafter) by adding raffinose, which cannot be used by animal cells, in a culture stage-dependent manner.

Results

Stage-dependent adjustment of simplified medium PZM-3 osmolarity (290 mOsM for the first 22 h and 320 mOsM thereafter) in the presence of 1 mM glycine significantly improved the quality of porcine oocyte maturation in vitro, manifested by the oocyte maturation rate, functional mitochondrial distribution and activity, the transcript levels of glycolysis genes in granulosa cells, and subsequent embryonic developmental ability and ROS levels.

Conclusion

Our study demonstrates that optimizing cell volume regulation can further enhance the developmental potential of oocytes cultured in vitro.

In vitro maturation of oocytes: what is already known?†

Assisted reproductive technologies (ARTs) involve the laboratory manipulation of gametes and embryos to help couples with fertility problems become pregnant. One of these procedures, controlled ovarian stimulation, uses pharmacological agents to induce ovarian and follicular maturation in vivo. Despite the effectiveness in achieving pregnancy and live births, some patients may have complications due to over-response to gonadotropins and develop ovarian hyperstimulation syndrome. In vitro maturation (IVM) of oocytes has emerged as a technique to reduce the risk of ovarian hyperstimulation syndrome, particularly in women with polycystic ovary syndrome, and for fertility preservation in women undergoing oncological treatment. Although there are some limitations, primarily due to oocyte quality, recent advances have improved pregnancy success rates and neonatal and infant outcomes. Different terms have been coined to describe variations of IVM, and the technique has evolved with the introduction of hormones to optimize results. In this review, we provide a comprehensive overview of IVM relating hormonal priming, culture system and media, and clinical indications for IVM with its reproductive outcomes during ARTs.

Formononetin promotes porcine oocytes maturation and improves embryonic development by reducing oxidative stress

Increasing evidence has demonstrated that oxidative stress impairs oocyte maturation and embryonic development. Conventionally, antioxidants have been applied in vitro systems to improve oocyte maturation and blastocyst rates. Formononetin (FMN) is a flavonoid that has been shown to have various pharmacological effects, including antioxidants. In this study, we delved into the impact of FMN, acting as an antioxidant, on the in vitro development of oocytes and blastocysts within the culture system. FMN supplementation at 0.5 μM enhanced the rate of first polar body extrusion and blastocyst formation post parthenogenetic activation. It also increased mitochondrial function and ATP levels, reduced intracellular reactive oxygen species, and elevated intracellular GSH levels in both oocytes and embryos. Moreover, FMN significantly decreased autophagy and apoptosis levels in blastocyst cells, potentially via regulation of the Nrf2/Keap1 pathway. This is the first study to report that FMN supplementation benefits the in vitro culture of oocytes and early embryo development, potentially by regulating oxidative stress, mitochondrial function, and autophagy.

The localization and function of the moonlighting protein Clathrin during oocyte maturation

Clathrin is one of the leading players in the endocytic process during oocyte maturation. Immunofluorescence and transmission electron analysis on fully-grown germinal vesicle (GV) mouse oocytes shows Clathrin localization on the cortical region with three peculiar patterns: complete, incomplete, and half-moon. The first configuration is characterized by Clathrin lattices along the cortex; the second is represented by Clathrin lattices interrupted by invaginations forming coated vesicles as an indication of active endocytosis. The half-moon profile, the less frequent but the most interesting one, refers to Clathrin lattices distributed to one-half of the cell. The in vivo analysis of organelles' positioning and cytoplasmic rearrangements, performed to understand the possible relation between endocytosis and oocyte maturation, suggests that the half-moon pattern indicates those fully-grown oocytes that may have likely undergone Germinal Vesicle Breakdown, MI, and MII. Our results show that, before oocytes undergo maturation, Clathrin localizes on the side of the cell, opposite to future spindle migration, thus marking spindle orientation in mouse oocytes.

Folic acids promote in vitro maturation of bovine oocytes by inhibition of ferroptosis via upregulated glutathione and downregulated Fe2+ accumulation

Bovine embryos by in vitro fertilization have become the primary source of commercial embryo transfers globally. However, the developmental capacity of in vitro maturation (IVM) oocytes is considerably lower than that of in vivo maturation (IVO) oocytes, owing to the production of reactive oxygen species (ROS) via mitochondrial metabolism, which was higher in IVM oocytes than in IVO oocytes. To avoid the negative effects of ROS on embryo quality, folic acid (FA) was supplemented directly into the IVM medium to antagonize ROS production, however, the mechanisms remain unknown. In the present study, five levels of FA (0, 25, 50, 100, and 200 µM) were supplemented into the bovine oocyte culture medium. The maturation, cleavage, and blastocyst formation rates increased by 8.95 %, 6.94 %, and 4.36 %, respectively, in the 50 µM group compared to the 0 µM group. Moreover, 7904 differential genes were identified between 0 µM and 50 µM groups by transcriptome sequencing, and they were mainly enriched in 8 pathways. The glutathione, ROS, and Fe2+ levels in oocytes were found to be associated with ferroptosis. Our results revealed that 50 µM FA promoted the IVM of bovine oocytes and affected the expression of genes involved in the ferroptosis pathway. The downregulation of TFR1 and STEAP3 led to a decrease in intracellular Fe2+ accumulation, and the upregulation of GCL increased oocyte GSH levels, thereby reducing the production of ROS in the ferroptosis pathway. Our study provides a new insight into the molecular mechanisms by which FA promotes bovine oocyte development in vitro.

Isorhamnetin Improves Oocyte Maturation by Activating the Pi3k/Akt Signaling Pathway

SCOPE

Isorhamnetin is a natural flavonoid with various pharmacological activities, which can be widely and continuously ingested by humans and animals through their daily diet. The aim of this study is to explore the benefits and molecular mechanisms of isorhamnetin on oocyte maturation.

METHODS AND RESULTS

Oocytes are incubated with isorhamnetin (5, 10, 20, and 30 µM) for 44 h. Isorhamnetin (10 µM) increases the polar body extrusion rate of oocytes. Furthermore, isorhamnetin alleviates oxidative stress by inhibiting reactive oxygen species levels and stimulating SOD2 protein expression. The changes in intracellular mitochondrial autophagy and apoptosis-related proteins (Bcl-2, Bax/Bcl-2, and C-Casp3) indicate that isorhamnetin inhibits oocyte apoptosis. Isorhamnetin inhibits endoplasmic reticulum stress by reducing the protein expression of CHOP and GRP78 and improving the normal distribution rate of endoplasmic reticulum. Mechanistic studies show that isorhamnetin activates the PI3K/Akt signaling pathway.

CONCLUSION

Isorhamnetin promotes oocyte maturation by inhibiting oxidative stress, mitochondrial dysregulation, apoptosis, and endoplasmic reticulum stress, which have important potential for improving oocyte quality and treating female infertility.

Enhancing the quality of inferior oocytes of buffalo for in vitro embryo production: The impact of melatonin on maturation, SCNT, and epigenetic modifications

Success of animal cloning is limited by oocyte quality, which is closely linked to reprogramming ability. The number of layers of cumulus cells is typically used to assess the quality of oocyte; a minimum of one-third of collected cumulus-oocyte complexes (COCs) are discarded as inferior oocytes because they have less cumulus cells. Melatonin, which has been recognised for its ability to sequester free radicals and perform multiple functions, has emerged as a potentially effective candidate for enhancing inferior oocytes quality and, consequently, embryo development competency. The current study investigates to improve the quality of inferior oocytes by supplementation of melatonin (10-9 M) during in vitro maturation (IVM) and subsequent cloned embryo production and its mechanism. The results indicate that melatonin supplementation significantly (p<0.05) enhances inferior oocytes maturation, reduces oxidative stress by reducing ROS levels, and improves mitochondrial function by boosting GSH levels. The melatonin treatment (10-9 M) enhances the expression of SOD, GPx1, GDF 9, BMP 15, ATPase 6, and ATPase 8 in inferior oocytes. Furthermore, melatonin treatment increases the total cell number in the treated groups, promoting cloned blastocyst formation rates derived from inferior oocytes. Furthermore, compared to the control, 10-9 M melatonin supplementation enhances H3K9ac acetylation and lowers H3K27me3 methylation in cloned blastocysts derived from inferior oocytes. In conclusion, 10-9 M melatonin supplementation during IVM increased inferior oocyte maturation and promoted cloned buffalo embryo development by lowering oxidative stress and promoting epigenetic alterations. These studies show that melatonin may improve the quality of poor oocytes and buffalo cloning.

Exploring nicotinamide adenine dinucleotide precursors across biosynthesis pathways: Unraveling their role in the ovary

Natural Nicotinamide Adenine Dinucleotide (NAD+) precursors have attracted much attention due to their positive effects in promoting ovarian health. However, their target tissue, synthesis efficiency, advantages, and disadvantages are still unclear. This review summarizes the distribution of NAD+ at the tissue, cellular and subcellular levels, discusses its biosynthetic pathways and the latest findings in ovary, include: (1) NAD+ plays distinct roles both intracellularly and extracellularly, adapting its distribution in response to requirements. (2) Different precursors differs in target tissues, synthetic efficiency, biological utilization, and adverse effects. Importantly: tryptophan is primarily utilized in the liver and kidneys, posing metabolic risks in excess; nicotinamide (NAM) is indispensable for maintaining NAD+ levels; nicotinic acid (NA) constructs a crucial bridge between intestinal microbiota and the host with diverse functions; nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) increase NAD+ systemically and can be influenced by delivery route, tissue specificity, and transport efficiency. (3) The biosynthetic pathways of NAD+ are intricately intertwined. They provide multiple sources and techniques for NAD+ synthesis, thereby reducing the dependence on a single molecule to maintain cellular NAD+ levels. However, an excess of a specific precursor potentially influencing other pathways. In addition, Protein expression analysis suggest that ovarian tissues may preferentially utilize NAM and NMN. These findings summarize the specific roles and potential of NAD+ precursors in enhancing ovarian health. Future research should delve into the molecular mechanisms and intervention strategies of different precursors, aiming to achieve personalized prevention or treatment of ovarian diseases, and reveal their clinical application value.

Developmental, cytogenetic and epigenetic consequences of removing complex proteins and adding melatonin during in vitro maturation of bovine oocytes

Background

In vitro maturation (IVM) of germinal vesicle intact oocytes prior to in vitro fertilization (IVF) is practiced widely in animals. In human assisted reproduction it is generally reserved for fertility preservation or where ovarian stimulation is contraindicated. Standard practice incorporates complex proteins (CP), in the form of serum and/or albumin, into IVM media to mimic the ovarian follicle environment. However, the undefined nature of CP, together with batch variation and ethical concerns regarding their origin, necessitate the development of more defined formulations. A known component of follicular fluid, melatonin, has multifaceted roles including that of a metabolic regulator and antioxidant. In certain circumstances it can enhance oocyte maturation. At this stage in development, the germinal-vesicle intact oocyte is prone to aneuploidy and epigenetic dysregulation.

Objectives

To determine the developmental, cytogenetic and epigenetic consequences of removing CP and including melatonin during bovine IVM.

Materials and methods

The study comprised a 2 x 2 factorial arrangement comparing (i) the inclusion or exclusion of CP, and (ii) the addition (100 nM) or omission of melatonin, during IVM. Cumulus-oocyte complexes (COCs) were retrieved from stimulated cycles. Following IVM and IVF, putative zygotes were cultured to Day 8 in standard media. RNAseq was performed on isolated cumulus cells, cytogenetic analyses (SNP-based algorithms) on isolated trophectoderm cells, and DNA methylation analysis (reduced representation bisulfite sequencing) on isolated cells of the inner-cell mass.

Results

Removal of CP during IVM led to modest reductions in blastocyst development, whilst added melatonin was beneficial in the presence but detrimental in the absence of CP. The composition of IVM media did not affect the nature or incidence of chromosomal abnormalities but cumulus-cell transcript expression indicated altered metabolism (primarily lipid) in COCs. These effects preceded the establishment of distinct metabolic and epigenetic signatures several days later in expanded and hatching blastocysts.

Conclusions

These findings highlight the importance of lipid, particularly sterol, metabolism by the COC during IVM. They lay the foundation for future studies that seek to develop chemically defined systems of IVM for the generation of transferrable embryos that are both cytogenetically and epigenetically normal.

Melatonin enhances the developmental potential of immature oocytes from older reproductive-aged women by improving mitochondrial function

Aims

To evaluate whether melatonin (MT) supplementation during in vitro maturation (IVM) of human oocytes can reverse the age-related decline in oocyte quality.

Main methods

We enrolled 172 patients aged ≥35 years (older reproductive-aged women) and 83 patients aged <35 years (young women) who underwent in vitro fertilization between 2019 and 2022. We conducted IVM with and without 10 μM MT in immature oocytes of different ages. Oocyte fertilization and embryo development were observed using a stereomicroscope. We assessed the immunofluorescence intensity of mitochondrial function, measured the copy number of mitochondrial DNA (mtDNA), and examined the spindle and chromosome composition in in vitro mature stage II (IVM-MII) oocytes using immunofluorescence and second-generation sequencing.

Key findings

MT supplementation significantly improved the redox level in the IVM medium and IVM-MII oocytes in older reproductive-aged women. It also significantly increased the proportion of circular mtDNA and the adenosine triphosphate content in IVM-MII oocytes. In addition, the IVM-MII oocytes obtained with MT supplementation showed a significant improvement in the normal composition of the spindle and chromosomes. Thus, the aged immature oocytes also showed significantly improved maturation and blastocyst formation rates owing to the role of MT.

Significance

Supplementation with 10 μM MT in the IVM medium reverses the age-related decline in oocyte quality. Our findings provide a viable solution for enhancing fertility in older reproductive-aged women.

The Boosting Effects of Melatonin on the In Vitro Fertilization (IVF) of Women with Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is one of the most critical disorders, which affects approximately 20% of women of childbearing age and melatonin supplementation in these women can be effective. However, human studies in this area are particularly limited to IVF candidates. The aim of this clinical trial study was to evaluate the effect of melatonin on the in vitro fertilization (IVF) in PCOS involved women. In this clinical trial study, a total of 320 women with PCOS were randomly assigned to the intervention and control groups. Patients in the intervention group (n=160) received a combination of melatonin and metformin (3 mg and 500 mg, respectively) three times a day. The control group (n=160) received metformin 500 mg from the luteal phase of the cycle before the start of gonadotropin. Oocyte and embryo quality, number of oocytes, and pregnancy outcomes were compared in both groups. Our study revealed that the frequency of Metaphase II oocytes (69.9% vs. 57.9%, p<0.001) and the number of embryos of the top-quality (grade A) were higher in the group treated with melatonin (40.3% vs. 29.9%, p=0.001). The rate of clinical pregnancy and implantation were also higher in the intervention group. The odds of clinical pregnancy in the intervention group was 1.8 times (p=0.039). Moreover, oral melatonin supplementation was effective in patients with PCOS, who were candidates for IVF because of the increased quality of mature oocytes, top-quality embryos, and increased odds of clinical pregnancy.

Melatonin improves the quality of rotenone-exposed mouse oocytes through association with histone modifications

Rotenone, an insecticide that inhibits mitochondrial complex I and generates oxidative stress, is responsible for neurological disorders and affects the female reproductive system. However, the underlying mechanism is not fully understood. Melatonin, a potential free-radical scavenger, has been shown to protect the reproductive system from oxidative damage. In this study, we investigated the impact of rotenone on mouse oocyte quality and evaluated the protective effect of melatonin on oocytes exposed to rotenone. Our results showed that rotenone impaired mouse oocyte maturation and early embryo cleavage. However, melatonin prevented these negative effects by ameliorating rotenone-induced mitochondrial dysfunction and dynamic imbalance, intracellular Ca²⁺ homeostasis damage, ER stress, early apoptosis, meiotic spindle formation disruption, and aneuploidy in oocytes. Additionally, RNA sequencing analysis showed that rotenone exposure changed the expression of multiple genes involved in histone methylation and acetylation modifications that result in mouse meiotic defects. However, melatonin partially rescued these defects. These findings suggest that melatonin has protective effects against rotenone-induced mouse oocyte defects.

The TH 22-mediated IL-22 deficiency associated with premature ovarian insufficiency

RESEARCH QUESTION

Is deficiency of IL-22 associated with premature ovarian insufficiency (POI)?

DESIGN

Levels of IL-22 and IL-22BP, IL-22-producing T cells, and IL22RA1/IL10R2 expression were measured and compared among 29 patients with POI, 42 with precursor stage of POI (pre-POI) and 46 control women. Correlation of serum IL-22 and IL-22⁺ CD4⁺ T subsets with ovarian reserve markers were further analyzed.

RESULTS

IL-22 levels in serum significantly differed among control women and patients with pre-POI and POI, with the lowest concentrations in POI group (p = .019). Significant reduction of peripheral CD4⁺ IL-22⁺ T cells was observed in patients with POI (p = .010), which mainly contributed by decrease of CD4⁺ IL-22⁺ IL-17^- T_H 22 cells (p = .012) but not T_H 17 cells (p = .125). Levels of serum IL-22 and IL-22-producing CD4⁺ T subsets were significantly correlated with ovarian reserve markers, including AMH, bilateral AFC, follicle-stimulating hormone (FSH), and E2 (p < .05). The specific receptor IL22RA1 expression was marginally reduced in granulosa cells from patients with pre-POI (p = .051). No difference of IL-22BP was observed either in serum (p = .216) or follicular fluid (p = .856) among groups.

CONCLUSIONS

Our study first demonstrated the significant association between T_H 22-mediated IL-22 deficiency and ovarian insufficiency, which provide new insights into the autoimmune disturbance and opens new avenues for exogenous IL-22 administration as potential intervention of POI.

IVM of human immature oocytes for infertility treatment and fertility preservation

Background

Thousands of healthy babies are born from in vitro maturation (IVM) procedures, but the rate of efficiency differs with the source of immature oocytes obtained. Recently, there are different IVM protocols proposed for infertility treatment and fertility preservation.

Methods

Based on the literature, the clinical application for IVM of immature oocytes was summarized.

Main findings Results

Immature oocytes may be retrieved from women after priming with or without the use of follicular stimulation hormone (FSH), human chorionic gonadotrophin (hCG) or a combination of both FSH and hCG. Successful pregnancy rates with IVM technology seem to be correlated with the number of immature oocytes obtained. With the source and culture course of immature oocytes, there are various IVM protocols. IVM of immature oocytes is profoundly affected by the culture conditions, but no breakthrough has been made by improving the IVM medium itself. Thus, the clinical application of IVM technology continues to evolve.

Conclusion

IVM technology is a useful technique for infertile women and fertility preservation. Mild stimulation IVF combined with IVM of immature oocytes is a viable alternative to the conventional stimulation IVF cycle treatment as it may prove to be an optimal first-line treatment approach.

Whole-genome methylation analysis reveals epigenetic variation between wild-type and nontransgenic cloned, ASMT transgenic cloned dairy goats generated by the somatic cell nuclear transfer

BACKGROUND

SCNT (somatic cell nuclear transfer) is of great significance to biological research and also to the livestock breeding. However, the survival rate of the SCNT cloned animals is relatively low compared to other transgenic methods. This indicates the potential epigenetic variations between them. DNA methylation is a key marker of mammalian epigenetics and its alterations will lead to phenotypic differences. In this study, ASMT (acetylserotonin-O-methyltransferase) ovarian overexpression transgenic goat was produced by using SCNT. To investigate whether there are epigenetic differences between cloned and WT (wild type) goats, WGBS (whole-genome bisulfite sequencing) was used to measure the whole-genome methylation of these animals.

RESULTS

It is observed that the different mCpG sites are mainly present in the intergenic and intronic regions between cloned and WT animals, and their CG-type methylation sites are strongly correlated. DMR (differentially methylated region) lengths are located around 1000 bp, mainly distributed in the exonic, intergenic and intronic functional domains. A total of 56 and 36 DMGs (differentially methylated genes) were identified by GO and KEGG databases, respectively. Functional annotation showed that DMGs were enriched in biological-process, cellular-component, molecular-function and other signaling pathways. A total of 10 identical genes related to growth and development were identified in GO and KEGG databases.

CONCLUSION

The differences in methylation genes among the tested animals have been identified. A total of 10 DMGs associated with growth and development were identified between cloned and WT animals. The results indicate that the differential patterns of DNA methylation between the cloned and WT goats are probably caused by the SCNT. These novel observations will help us to further identify the unveiled mechanisms of somatic cell cloning technology, particularly in goats.

Metformin promotes in vitro maturation of oocytes from aged mice by attenuating mitochondrial oxidative stress via SIRT3-dependent SOD2ac

Human female fecundity decreases irreversibly as chronological age rises, adversely affecting oocyte quality, consequently worsening pregnancy outcomes and increasing the extent of birth defects. The first-line type 2 diabetes treatment metformin has been associated with delayed aging and reduction of oxidative stress; yet it remains unclear if metformin confers any benefits for oocytes from aged mice, particularly in the context of the assisted human reproductive technology (ART) known as in vitro maturation (IVM). Here, we found that adding metformin into the M16 culture medium of oocytes from aged mice significantly improved both oocyte maturation and early embryonic development. This study showed that metformin reduced the extent of meiotic defects and maintained a normal distribution of cortical granules (CGs). RNA-seq analysis of metformin-treated oocytes revealed genes apparently involved in the reduction of mitochondrial ROS. Further, the results supported that the metformin improved mitochondrial function, reduced apoptosis, increased the extent of autophagy, and reduced mitochondrial ROS via SIRT3-mediated acetylation status of SOD2K68 in oocytes from aged mice. Thus, this finding demonstrated a protective effect for metformin against the decreased quality of oocytes from aged mice to potentially improve ART success rates and illustrated a potential strategy to prevent or delay reproductive aging.

Translatome and transcriptome co-profiling reveals a role of TPRXs in human zygotic genome activation

Translational regulation plays a critical role during the oocyte-to-embryo transition (OET) and zygotic genome activation (ZGA). Here, we integrated ultra-low-input Ribo-seq with mRNA-seq to co-profile the translatome and transcriptome in human oocytes and early embryos. Comparison with mouse counterparts identified widespread differentially translated genes functioning in epigenetic reprogramming, transposon defense, and small RNA biogenesis, in part driven by species-specific regulatory elements in 3' untranslated regions. Moreover, PRD-like homeobox transcription factors, including TPRXL, TPRX1, and TPRX2, are highly translated around ZGA. TPRX1/2/L knockdown leads to defective ZGA and preimplantation development. Ectopically expressed TPRXs bind and activate key ZGA genes in human embryonic stem cells. These data reveal the conservation and divergence of translation landscapes during OET and identify critical regulators of human ZGA.

Nonylphenol exposure-induced oocyte quality deterioration could be reversed by melatonin supplementation in mice

Nonylphenol (NP) belongs to the metabolites of commercial detergents, which acts as an environmental endocrine disruptor. NP is reported to have multiple toxicity including reproductive toxicity. In present study, we reported the protective effects of melatonin on the NP-exposed oocyte quality. We set up a mouse in vivo model of NP exposure (500 μg/L), by daily drinking and continued feeding for 4 weeks; and we gave a daily dose of melatonin (30 mg/kg) to the NP-exposed mice. Melatonin supplementation restores the development ability of oocytes exposed to NP, and this was due to the reduction of ROS level and DNA damage by melatonin. Melatonin could rescue aberrant mitochondria distribution, mitochondria membrane potential, which also was reflected by ATP content and mtDNA copy number. Moreover, melatonin could restore the RPS3 expression to ensure the ribosome function for protein synthesis, and reduced GRP78 protein level to protect against ER stress and ER distribution defects. We also found that vesicle protein Rab11 from Golgi apparatus was protected by melatonin at the spindle periphery of oocytes of NP-exposed mice, which further moderated LAMP2 for lysosome function. Our results indicate that melatonin protects oocytes from NP exposure through its effects on the reduction of oxidative stress and DNA damage, which might be through its amelioration on the organelles in mice.

IGF2 reduces meiotic defects in oocytes from obese mice and improves embryonic developmental competency

BACKGROUND

Maternal obesity is a global issue that has devastating effects across the reproductive spectrum such as meiotic defects in oocytes, consequently worsening pregnancy outcomes. Different studies have shown that such types of meiotic defects originated from the oocytes of obese mothers. Thus, there is an urgent need to develop strategies to reduce the incidence of obesity-related oocyte defects that adversely affect pregnancy outcomes. Multiple growth factors have been identified as directly associated with female reproduction; however, the impact of various growth factors on female fertility in response to obesity remains poorly understood.

METHODS

The immature GV-stage oocytes from HFD female mice were collected and cultured in vitro in two different groups (HFD oocytes with and without 50 nM IGF2), however; the oocytes from ND mice were used as a positive control. HFD oocytes treated with or without IGF2 were further used to observe the meiotic structure using different analysis including, the spindle and chromosomal analysis, reactive oxygen species levels, mitochondrial functional activities, and early apoptotic index using immunofluorescence. Additionally, the embryonic developmental competency and embryos quality of IGF2-treated zygotes were also determined.

RESULTS

In our findings, we observed significantly reduced contents of insulin-like growth factor 2 (IGF2) in the serum and oocytes of obese mice. Our data indicated supplementation of IGF2 in a culture medium improves the blastocyst formation: from 46% in the HFD group to 61% in the HFD + IGF2-treatment group (50 nM IGF2). Moreover, adding IGF2 to the culture medium reduces the reactive oxygen species index and alleviates the frequency of spindle/chromosome defects. We found increased mitochondrial functional activity in oocytes from obese mice after treating the oocytes with IGF2: observed elevated level of adenosine triphosphate, increased mitochondrial distribution, higher mitochondrial membrane potentials, and reduced mitochondrial ultrastructure defects. Furthermore, IGF2 administration also increases the overall protein synthesis and decreases the apoptotic index in oocytes from obese mice.

CONCLUSIONS

Collectively, our findings are strongly in favor of adding IGF2 in culture medium to overcome obesity-related meiotic structural-developmental defects by helping ameliorate the known sub-optimal culturing conditions that are currently standard with assisted reproduction technologies.

Lipid Metabolic Process Involved in Oocyte Maturation During Folliculogenesis

Oocyte maturation is a complex and dynamic process regulated by the coordination of ovarian cells and numerous extraovarian signals. From mammal studies, it is learnt that lipid metabolism provides sufficient energy for morphological and cellular events during folliculogenesis, and numerous lipid metabolites, including cholesterol, lipoproteins, and 14-demethyl-14-dehydrolanosterol, act as steroid hormone precursors and meiotic resumption regulators. Endogenous and exogenous signals, such as gonadotropins, insulin, and cortisol, are the upstream regulators in follicular lipid metabolic homeostasis, forming a complex and dynamic network in which the key factor or pathway that plays the central role is still a mystery. Though lipid metabolites are indispensable, long-term exposure to a high-fat environment will induce irreversible damage to follicular cells and oocyte meiosis. This review specifically describes the transcriptional expression patterns of several lipid metabolism–related genes in human oocytes and granulosa cells during folliculogenesis, illustrating the spatiotemporal lipid metabolic changes in follicles and the role of lipid metabolism in female reproductive capacity. This study aims to elaborate the impact of lipid metabolism on folliculogenesis, thus providing guidance for improving the fertility of obese women and the clinical outcome of assisted reproduction.

Melatonin and the Programming of Stem Cells

Melatonin interacts with various types of stem cells, in multiple ways that comprise stimulation of proliferation, maintenance of stemness and self-renewal, protection of survival, and programming toward functionally different cell lineages. These various properties are frequently intertwined but may not be always jointly present. Melatonin typically stimulates proliferation and transition to the mature cell type. For all sufficiently studied stem or progenitor cells, melatonin’s signaling pathways leading to expression of respective morphogenetic factors are discussed. The focus of this article will be laid on the aspect of programming, particularly in pluripotent cells. This is especially but not exclusively the case in neural stem cells (NSCs) and mesenchymal stem cells (MSCs). Concerning developmental bifurcations, decisions are not exclusively made by melatonin alone. In MSCs, melatonin promotes adipogenesis in a Wnt (Wingless-Integration-1)-independent mode, but chondrogenesis and osteogenesis Wnt-dependently. Melatonin upregulates Wnt, but not in the adipogenic lineage. This decision seems to depend on microenvironment and epigenetic memory. The decision for chondrogenesis instead of osteogenesis, both being Wnt-dependent, seems to involve fibroblast growth factor receptor 3. Stem cell-specific differences in melatonin and Wnt receptors, and contributions of transcription factors and noncoding RNAs are outlined, as well as possibilities and the medical importance of re-programming for transdifferentiation.

Stress associated ovarian dysfunctions in a seasonal breeder Funambulus pennanti: Role of glucocorticoids and possible amelioration by melatonin

Studies have shown that stress caused by lack of physical activity disrupts the normal pattern of glucocorticoid secretion which adversely affects the reproductive axis. We studied the effect of chronic movement restriction on ovarian responses in the Indian Palm Squirrel Funambulus pennanti, a highly active diurnal rodent. Physical restraint of squirrels induced stress that led to a significant increase in plasma cortisol, corticosterone and decreased 17β-estradiol level leading to follicular atresia. Ovarian Reactive Oxygen Species (ROS) content, lipid peroxidation (LPO), activities of superoxide dismutase (SOD) and catalase (CAT) enzymes increased in restrained squirrels. Elevated ROS increased the oxidative load that led to ovarian cell death as evidenced by increased Bax and decreased Bcl2 expression causing further decline in Aromatase and ERα proteins. To elaborate the mechanism(s) involved in stress induced glucocorticoid mediated oxidative damages to the ovary we extended our study by exposing ovaries in vitro to the synthetic glucocorticoid dexamethasone (200 μM). We observed that glucocorticoid receptor (GR) expression was significantly increased in dexamethasone treated ovaries in vitro with a decrease in expression of Nrf2 and HO-1 proteins. Melatonin supplementation (10 nM) along with dexamethasone significantly decreased ovarian ROS production, lipid peroxidation and increased antioxidant enzyme activities by improving the expression of Nrf2 and HO-1, reinstating the cellular redox homeostasis. Therefore, it can be suggested that physical restraint induced glucocorticoid and its receptor activation interfered with the ovarian antioxidant defense mechanism. Melatonin via its receptor MT1 significantly alleviated ovarian damages acting as a cytoprotective agent.

Exogenous melatonin protects preimplantation embryo development from decabromodiphenyl ethane-induced circadian rhythm disorder and endogenous melatonin reduction

Decabromodiphenyl ethane (DBDPE) is a novel flame retardant that is widely used in plastics, electronic products, building materials and textiles. Our previous studies have revealed the oocyte toxicity of DBDPE, but the effect of DBDPE on preimplantation embryo development has not been reported. Here, we investigated whether and how DBDPE exposure affects preimplantation embryo development. Adult female mice were orally exposed to DBDPE (0, 5, 50, 500 μg/kg bw/day) for 14 days. First, we found that after DBDPE exposure, mice showed obvious circadian rhythm disorder. Moreover, the development of preimplantation embryos was inhibited in DBDPE-exposed mice after pregnancy. Then, we further explored and revealed that DBDPE exposure reduced the endogenous melatonin (MLT) level during pregnancy, thereby inhibiting the development of preimplantation embryos. Furthermore, we discovered that exogenous MLT supplementation (15 mg/kg bw/day) rescued the inhibition of preimplantation embryo development induced by DBDPE, and a mechanistic study demonstrated that exogenous MLT inhibited the overexpression of ROS and DNA methylation at the 5-position of cytosine (5-mC) in DBDPE-exposed preimplantation embryos. Simultaneously, MLT ameliorated the DBDPE-induced mitochondrial dysfunction by increasing the mitochondrial membrane potential (MMP), ATP, and Trp1 expression. Additionally, MLT restored DBDPE-induced changes in zona pellucida (ZP) hardness and trophectoderm (TE) cortical tension. Finally, the protective effect of MLT on embryos ameliorated the adverse reproductive outcomes (dead fetus, fetus with abnormal liver, fetal weight loss) induced by DBDPE. Collectively, DBDPE induced preimplantation embryo damage leading to adverse reproductive outcomes, and MLT has emerged as a potential tool to rescue adverse reproductive outcomes induced by DBDPE.

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

Increasing evidence suggests that in vitro fertilization (IVF) may be associated with an increased risk of developing obesity and metabolic diseases later in life in the offspring. Notably, the addition of melatonin to culture medium may improve embryo development and prevent cardiovascular dysfunction in IVF adult mice. This study aimed to determine if melatonin supplementation in the culture medium can reverse impaired glucose metabolism in IVF mice offspring and the underlying mechanisms. Blastocysts used for transfer were generated by natural mating (control group) or IVF with or without melatonin (10^-6  M) supplementation (mIVF and IVF group, respectively) in clinical-grade culture media. Here, we first report that IVF decreased hepatic expression of Fbxl7, which was associated with impaired glucose metabolism in mice offspring. Melatonin addition reversed the phenotype by up-regulating the expression of hepatic Fbxl7. In vitro experiments showed that Fbxl7 enhanced the insulin signaling pathway by degrading RhoA through ubiquitination and was up-regulated by transcription factor Foxa2. Specific knockout of Fbxl7 in the liver of adult mice, through tail intravenous injection of recombinant adeno-associated virus, impaired glucose tolerance, while overexpression of hepatic Fbxl7 significantly improved glucose tolerance in adult IVF mice. Thus, the data suggest that Fbxl7 plays an important role in maintaining glucose metabolism of mice, and melatonin supplementation in the culture medium may rescue the long-term risk of metabolic diseases in IVF offspring.

Melatonin mitigates Chloroquine-induced defects in porcine immature Sertoli cells

Chloroquine (CQ) could function as a lysosomotropic agent to inhibit the endolysosomal trafficking in the autophagy pathway, and is widely used on malarial, tumor and recently COVID-19. However, the effect of CQ treatment on porcine immature Sertoli cells (iSCs) remains unclear. Here we showed that CQ could reduce iSC viability in a dose-dependent manner. CQ treatment (20 μM) on iSCs for 36h could elevate oxidative stress, damage mitochondrial function and promote apoptosis, which could be partially rescued by melatonin (MT) (10 nM). Transcriptome profiling identified 1611 differentially expressed genes (DEGs) (776 up- and 835 down-regulated) (20 μM CQ vs. DMSO), mainly involved in MAPK cascade, cell proliferation/apoptosis, HIF-1, PI3K-Akt and lysosome signaling pathways. In contrast, only 467 (224 up- and 243 down-regulated) DEGs (CQ + MT vs. DMSO) could be found after MT (10 nM) addition, enriched in cell cycle, regulation of apoptotic process, lysosome and reproduction pathways. Therefore, the partial rescue effects of MT on CQ treatment were confirmed by multiple assays (cell viability, ROS level, mitochondrial function, apoptosis, and mRNA levels of selected genes). Collectively, CQ treatment could impair porcine iSC viability by deranging the signaling pathways related to apoptosis and autophagy, which could be partially rescued by MT supplementation.

Factors Influencing the In Vitro Maturation (IVM) of Human Oocyte

In vitro maturation (IVM) of oocytes is a promising assisted reproductive technology (ART) deemed as a simple and safe procedure. It is mainly used in patients with impaired oocyte maturation and in fertility preservation for women facing the risk of losing fertility. However, to date, it is still not widely used in clinical practice because of its underperformance. The influencing factors, such as biphasic IVM system, culture medium, and the supplementation, have a marked effect on the outcomes of oocyte IVM. However, the role of different culture media, supplements, and follicular priming regimens in oocyte IVM have yet to be fully clarified and deserve further investigation.

Players in Mitochondrial Dynamics and Female Reproduction

Mitochondrial dynamics (fission and fusion) are essential physiological processes for mitochondrial metabolic function, mitochondrial redistribution, and mitochondrial quality control. Various proteins are involved in regulating mitochondrial dynamics. Aberrant expression of these proteins interferes with mitochondrial dynamics and induces a range of diseases. Multiple therapeutic approaches have been developed to treat the related diseases in recent years, but their curative effects are limited. Meanwhile, the role of mitochondrial dynamics in female reproductive function has attracted progressively more attention, including oocyte development and maturation, fertilization, and embryonic development. Here, we reviewed the significance of mitochondrial dynamics, proteins involved in mitochondrial dynamics, and disorders resulting from primary mitochondrial dynamic dysfunction. We summarized the latest therapeutic approaches of hereditary mitochondrial fusion-fission abnormalities and reviewed the recent advances in female reproductive mitochondrial dynamics.

Melatonin and Myo-Inositol: Supporting Reproduction from the Oocyte to Birth

Human pregnancy is a sequence of events finely tuned by several molecular interactions that come with a new birth. The precise interlocking of these events affecting the reproductive system guarantees safe embryo formation and fetal development. In this scenario, melatonin and myo-inositol seem to be pivotal not only in the physiology of the reproduction process, but also in the promotion of positive gestational outcomes. Evidence demonstrates that melatonin, beyond the role of circadian rhythm management, is a key controller of human reproductive functions. Similarly, as the most representative member of the inositol’s family, myo-inositol is essential in ensuring correct advancing of reproductive cellular events. The molecular crosstalk mediated by these two species is directly regulated by their availability in the human body. To date, biological implications of unbalanced amounts of melatonin and myo-inositol in each pregnancy step are growing the idea that these molecules actively contribute to reduce negative outcomes and improve the fertilization rate. Clinical data suggest that melatonin and myo-inositol may constitute an optimal dietary supplementation to sustain safe human gestation and a new potential way to prevent pregnancy-associated pathologies.

Applications of Melatonin in Female Reproduction in the Context of Oxidative Stress

Oxidative stress has been recognized as one of the causal mediators of female infertility by affecting the oocyte quality and early embryo development. Improving oxidative stress is essential for reproductive health. Melatonin, a self-secreted antioxidant, has a wide range of effects by improving mitochondrial function and reducing the damage of reactive oxygen species (ROS). This minireview illustrates the applications of melatonin in reproduction from four aspects: physiological ovarian aging, vitrification freezing, in vitro maturation (IVM), and oxidative stress homeostasis imbalance associated with polycystic ovary syndrome (PCOS), emphasising the role of melatonin in improving the quality of oocytes in assisted reproduction and other adverse conditions.

GAS6 ameliorates advanced age-associated meiotic defects in mouse oocytes by modulating mitochondrial function

Previously, we reported that the silencing of growth arrest-specific gene 6 (Gas6) expression in oocytes impairs cytoplasmic maturation by suppressing mitophagy and inducing mitochondrial dysfunction, resulting in fertilization failure. Here, we show that oocyte aging is accompanied by an increase in meiotic defects associated with chromosome misalignment and abnormal spindle organization. Intriguingly, decreased Gas6 mRNA and protein expression were observed in aged oocytes from older females. We further explored the effect of GAS6 on the quality and fertility of aged mouse oocytes using a GAS6 rescue analysis. After treatment with the GAS6 protein, aged oocytes matured normally to the meiosis II (MII) stage. Additionally, maternal age-related meiotic defects were reduced by GAS6 protein microinjection. Restoring GAS6 ameliorated the mitochondrial dysfunction induced by maternal aging. Ultimately, GAS6-rescued MII oocytes exhibited increased ATP levels, reduced ROS levels and elevated glutathione (GSH) levels, collectively indicating improved mitochondrial function in aged oocytes. Thus, the age-associated decrease in oocyte quality was prevented by restoring GAS6. Importantly, GAS6 protein microinjection in aged oocytes also rescued fertility. We conclude that GAS6 improves mitochondrial function to achieve sufficient cytoplasmic maturation and attenuates maternal age-related meiotic errors, thereby efficiently safeguarding oocyte quality and fertility.

Melatonin promotes in vitro maturation of vitrified-warmed mouse GV oocytes potentially by modulating MAD2 protein expression of SAC component through MTRs

Previous studies have shown that melatonin (MT) can ameliorate vitrification-inflicted damage in mouse germinal vesicle (GV) oocytes, however, the key mechanistic basis of this improvement still remains poorly understood. This study was conducted to investigate whether MT can improve in vitro developmental potential of vitrified-warmed GV oocytes through its receptors. The fresh oocytes were randomly divided into four groups: untreated (control group, F), vitrified by open-pulled straw method (vitrification group, V), vitrification group with 100 nmol/L MT supplementation (vitrification + MT group, VM), and with 100 nmol/L MT plus 100 nmol/L luzindole administration (vitrification + MT + luzindole group, VML) or with 50 nmol/L ramelteon addition (vitrification + ramelteon group; VR). After warming, oocytes were cultured in vitro, and MT receptors (MTRs), MAD2 (mitotic arrest deficient 2), Securin and CyclinB1 protein levels and spindle morphology were evaluated. The ratio of oocytes developed to the metaphase I (MI) and metaphase II (MII) stages was also assessed. The results showed that after vitrification-warming, the in vitro maturation rate of GV oocytes was significantly lower compared to the control (F) group. Vitrification also significantly impaired the spindle morphology, decreased the protein level of MTRs and Securin, and decreased MAD2 levels in MI oocytes. However, when MT or ramelteon (MTRs agonist) were added (group wise) to warming and maturation media, the maturation rate of GV oocytes was significantly increased, the normal proportion of the spindle morphology increased, and the expression level of MAD2 increased in their resulting MI oocytes compared to the vitrification group. However, following addition of both MT and ramelteon, the maturation rate of GV oocyte showed no significant difference between VML and vitrification groups. The spindle morphology and MAD2 levels in MI oocytes were comparable to the vitrification group but differed significantly from the VM group. Taken together, finding of the present study shows that MT (100 nmol/L) can ameliorate the in vitro maturation of vitrified-warmed mouse GV oocytes, potentially by improving the spindle morphology, modulating MAD2 protein level and promoting the development of MI stage oocytes through MTRs.

Melatonin improves the first cleavage of parthenogenetic embryos from vitrified-warmed mouse oocytes potentially by promoting cell cycle progression

Background

This study investigated the effect of melatonin (MT) on cell cycle (G1/S/G2/M) of parthenogenetic zygotes developed from vitrified-warmed mouse metaphase II (MII) oocytes and elucidated the potential mechanism of MT action in the first cleavage of embryos.

Results

After vitrification and warming, oocytes were parthenogenetically activated (PA) and in vitro cultured (IVC). Then the spindle morphology and chromosome segregation in oocytes, the maternal mRNA levels of genes including Miss, Doc1r, Setd2 and Ythdf2 in activated oocytes, pronuclear formation, the S phase duration in zygotes, mitochondrial function at G1 phase, reactive oxygen species (ROS) level at S phase, DNA damage at G2 phase, early apoptosis in 2-cell embryos, cleavage and blastocyst formation rates were evaluated. The results indicated that the vitrification/warming procedures led to following perturbations 1) spindle abnormalities and chromosome misalignment, alteration of maternal mRNAs and delay in pronucleus formation, 2) decreased mitochondrial membrane potential (MMP) and lower adenosine triphosphate (ATP) levels, increased ROS production and DNA damage, G1/S and S/G2 phase transition delay, and delayed first cleavage, and 3) increased early apoptosis and lower levels of cleavage and blastocyst formation. Our results further revealed that such negative impacts of oocyte cryopreservation could be alleviated by supplementation of warming, recovery, PA and IVC media with 10^− 9 mol/L MT before the embryos moved into the 2-cell stage of development.

Conclusions

MT might promote cell cycle progression via regulation of MMP, ATP, ROS and maternal mRNA levels, potentially increasing the first cleavage of parthenogenetic zygotes developed from vitrified–warmed mouse oocytes and their subsequent development.

Research progress of melatonin (MT) in improving ovarian function: a review of the current status

Melatonin (MT) is an endogenous hormone mainly synthesized by pineal cells, which has strong endogenous effects of eliminating free radicals and resisting oxidative damages. Melatonin (MT) can not only regulate the body’s seasonal and circadian rhythms; but also delay ovarian senescence, regulate ovarian biological rhythm, promote follicles formation, and improve oocyte quality and fertilization rate. This review aimd to provide evidence concerning the synthesis and distribution, ovarian function, and role of MT in development of follicles and oocytes. Moreover, the role of MT as antioxidative, participating in biological rhythm regulation, was also reviewed. Furthermore, the effects of MT on various ovarian related diseases were analyzed, particularly for the ovarian aging and polycystic ovary syndrome (PCOS).

Melatonin alleviates deoxynivalenol-induced apoptosis of human granulosa cells by reducing mutually accentuated FOXO1 and ER stress‡

Deoxynivalenol (DON) is one of the most prevalent Fusarium mycotoxins, which cause detrimental effects on human and animal reproductive systems by inducing oxidative stress. Increasing evidence has suggested the potential roles of melatonin in protecting granulosa cells from oxidative injury, but the underlying mechanisms remain largely elusive. Here, we demonstrated that suppression of FOXO1 and endoplasmic reticulum (ER) stress was engaged in melatonin-mediated protection against oxidative damage in human granulosa cells upon DON exposure in vitro. DON induced excess reactive oxygen species accumulation, cells viability loss, reduced estradiol-17β, and progesterone production in human granulosa cells, whereas melatonin ameliorated these phenotypes. Next, we found that the protective effect of melatonin against apoptosis was via reducing ER stress because the inhibition of ER stress displayed similar protective effects during DON treatment. Moreover, melatonin provided no additional protection when ER stress was inhibited. We further found that FOXO1 is a pivotal downstream effector of melatonin and ER stress in regulating DON-induced apoptosis in human granulosa cells. Blocking of FOXO1 reduced DON-induced cells death and FOXO1 activation could be suppressed by melatonin or ER stress inhibitor. However, melatonin failed to further restore cells viability in the presence of FOXO1 inhibitor. Collectively, our results reveal a new mechanism of melatonin in protecting against DON-induced apoptosis and dysfunction by suppressing ER stress and FOXO1 in human granulosa cells.

Mitochondria: emerging therapeutic strategies for oocyte rescue

As the vital organelles for cell energy metabolism, mitochondria are essential for oocyte maturation, fertilization, and embryo development. Abnormalities in quantity, quality, and function of mitochondria are closely related to poor fertility and disorders, such as decreased ovarian reserve (DOR), premature ovarian aging (POA), and ovarian aging, as well as maternal mitochondrial genetic disease caused by mitochondrial DNA (mtDNA) mutations or deletions. Mitochondria have begun to become a therapeutic target for infertility caused by factors such as poor oocyte quality, oocyte aging, and maternal mitochondrial genetic diseases. Mitochondrial replacement therapy (MRT) has attempted to use heterologous or autologous mitochondria to rebuild healthy state of oocyte by increasing the amount of mitochondria (e.g., partial ooplasm transfer, autologous mitochondrial transfer), or to stop the transmission of mtDNA diseases by replacing abnormal maternal mitochondria (e.g., pronuclei transfer, spindle transfer, polar body transfer). Among them, autologous mitochondrial transfer is the most promising therapeutic technology as of today which does not involve using a third party, but its clinical efficacy is controversial due to many factors such as the aging phenomenon of germ line cells, the authenticity of the existence of ovarian stem cells (OSC), and secondary damage caused by invasive surgery to patients with poor ovarian function. Therefore, the research of optimal autologous cell type that can be applied in autologous mitochondrial transfer is an area worthy of further exploration. Besides, the quality of germ cells can also be probably improved by the use of compounds that enhance mitochondrial activity (e.g., coenzyme Q10, resveratrol, melatonin), or by innovative gene editing technologies which have shown capability in reducing the risk of mtDNA diseases (e.g., CRISPR/Cas9, TALENTs). Though the current evidences from animal and clinical trials are not sufficient, and some solutions of technical problems are still needed, we believe this review will guide a new direction in the possible clinical applied mitochondrial-related therapeutic strategies in reproductive medicine.

Roles of melatonin in the teleost ovary: A review of the current status

Melatonin, the neurohormone mainly synthesized in and secreted from the pineal gland of vertebrates following a circadian rhythm, is an important factor regulating various physiological processes, including reproduction. Recent data indicate that melatonin is also synthesized in the ovary and that it acts directly at the level of the ovary to modulate ovarian physiology. In some teleosts, melatonin is reported to affect ovarian steroidogenesis. The direct action of melatonin on the ovary could be a possible factor promoting oocyte maturation in teleosts. A role for melatonin in follicle rupture during ovulation in the teleost medaka has recently emerged. In addition, melatonin is suggested to affect oocyte maturation by its antioxidant activity. However, the molecular mechanisms underlying these direct effects of melatonin are largely unknown.

IGF2 improves the developmental competency and meiotic structure of oocytes from aged mice

Advanced maternal-age is a major factor adversely affecting oocyte quality, consequently worsening pregnancy outcomes. Thus, developing strategies to reduce the developmental defects associated with advanced maternal-age would benefit older mothers. Multiple growth factors involved in female fertility have been extensively studied; however, the age-related impacts of various growth factors remain poorly studied. In the present study, we identified that levels of insulin-like growth factor 2 (IGF2) are significantly reduced in the serum and oocytes of aged mice. We found that adding IGF2 in culture medium promotes oocyte maturation and significantly increases the proportion of blastocysts: from 41% in the untreated control group to 64% (50 nM IGF2) in aged mice (p < 0.05). Additionally, IGF2 supplementation of the culture medium reduced reactive oxygen species production and the incidence of spindle/chromosome defects. IGF2 increases mitochondrial functional activity in oocytes from aged mice: we detected increased ATP levels, elevated fluorescence intensity of mitochondria, higher mitochondrial membrane potentials, and increased overall protein synthesis, as well as increased autophagy activity and decreased apoptosis. Collectively, our findings demonstrate that IGF2 supplementation in culture media improves oocyte developmental competence and reduces meiotic structure defects in oocytes from aged mice.

Quercetin promotes in vitro maturation of oocytes from humans and aged mice

Maternal fertility declines irreversibly with aging, and advanced maternal age is mostly related to impaired oocyte quality. The flavonol compound quercetin is considered to be an anti-aging agent due to its cytoprotective actions as an antioxidant. However, its role and mechanisms on aged oocytes are unclear. In this study, the quercetin promotes in vitro maturation (IVM) and early embryonic development of oocytes from aged mice. It is extended these findings in human oocytes, showing that quercetin promotes the IVM rate by 19.6% and increases the blastocyst formation rate by 15.5% compared to untreated controls. The overall oocyte quality of aged mice is improved by quercetin treatment, assessed as spindle/chromosome morphology and cortical granule distribution. Mitochondria is the primary endogenous source of age-related oxidative stress, and an RNA-seq analysis of quercetin-treated oocytes reveals molecular insights including scavenged mitochondrial-ROS, reduced apoptosis, and improved autophagy. Further, this study demonstrates that quercetin reduces ROS via SIRT3-mediated acetylation of SOD2's K68 residue. Thus, beyond demonstrating that quercetin confers beneficial mitochondria-related impacts in aged oocytes, this study illustrates a potential strategy to prevent or delay oocyte aging and to improve success rates of assisted human reproductive technologies (ART).

Melatonin attenuates 17β-trenbolone induced insomnia-like phenotype and movement deficiency in zebrafish

17β-trenbolone (17β-TBOH) is one of the dominant metabolites of trenbolone acetate, which is widely applied in beef cattle operations around the globe. The effects of environmental concentrations of 17β-trenbolone on the early development of zebrafish embryos have received very little attention. Melatonin could regulate sleep-wake cycle and plays a protective role in various adverse conditions. Here, environmentally realistic concentrations of 17β-trenbolone (1 ng/L, 10 ng/L, 50 ng/L) has been exposure to zebrafish embryos at 2 h postfertilization (hpf). The results showed that 10 ng/L and 50 ng/L 17β-trenbolone disturbed the distribution of caudal primary motoneurons and downregulated expression of motoneuron development related genes along with locomotion decreasing. While melatonin could recover the detrimental effects caused by 17β-trenbolone. Interestingly, 17β-trenbolone exposure increased waking activity and decreased rest even in a low dose (1 ng/L). Moreover, it upregulated hypocretin/orexin (Hcrt) signaling which promotes wakefulness. Melatonin restored the insomnia-like alternation induced by 17β-trenbolone exposure. Collectively, we conclude that 17β-trenbolone disturbed motoneuron development and altered sleep/wake behavior, while melatonin could alleviate the deleterious influence on motoneuron development and recover the circadian rhythm.

Melatonin promotes the development of immature oocytes from the COH cycle into healthy offspring by protecting mitochondrial function

Melatonin (MT) regulates reproductive performance as a potent antioxidant; however, its beneficial effects on oocyte development remain largely unknown, especially in human oocytes. The collected 193 immature oocytes from the controlled ovarian hyperstimulation (COH) cycle underwent in vitro maturation (IVM) in IVM medium contained 10 μmol/L MT (n = 105, M group) and no MT (n = 88, NM group), followed by insemination and embryo culture. The results showed that the high-quality blastocyst formation rate in the M group (28.4%) was significantly higher than that in the NM group (2.0%) (P = .0001), and the aneuploidy rate was low (15.8%). In the subsequent clinical trials, three healthy infants were delivered. Next, single-cell RNA-seq data revealed 1026 differentially expressed genes (DEGs) between the two groups, KEGG enrichment analysis revealed that the majority of DEGs involved in oxidative phosphorylation pathway, which associated with ATP generation, was upregulated in the M group. Finally, confocal fluorescence staining results revealed that the mitochondrial membrane potential in the oocytes significantly increased and intracellular ROS and Ca²⁺ levels greatly decreased in the M group. Melatonin can promote the development of immature human oocytes retrieved from the COH cycle into healthy offspring by protecting mitochondrial function.