Near-infrared fluorophore IR-61 delays postovulatory aging of mouse oocytes through suppressing oxidative stress mediated by mitochondrial protection.

Postovulatory aging can trigger deterioration of oocyte quality and subsequent embryonic development, and thus reduce the success rates of assisted reproductive technology (ART). The molecular mechanisms underlying postovulatory aging, and preventative strategies, remain to be explored. The near-infrared fluorophore IR-61, a novel heptamethine cyanine dye, has the potential for mitochondrial targeting and cell protection. In this study, we found that IR-61 accumulated in oocyte mitochondria and reduced the postovulatory aging-induced decline in mitochondrial function, including mitochondrial distribution, membrane potential, mtDNA number, ATP levels, and mitochondrial ultrastructure. In addition, IR-61 rescued postovulatory aging-caused oocyte fragmentation, defects in spindle structure, and embryonic developmental potential. RNA sequencing analysis indicated that the postovulatory aging-induced oxidative stress pathway might be inhibited by IR-61. We then confirmed that IR-61 decreased the levels of reactive oxygen species and MitoSOX, and increased GSH content in aged oocytes. Collectively, the results indicate that IR-61 may prevent postovulatory aging by rescuing oocyte quality, promoting successful rate in ART procedure.

Lactate regulates major zygotic genome activation by H3K18 lactylation in mammals.

Lactate is present at a high level in the microenvironment of mammalian preimplantation embryos in vivo and in vitro. However, its role in preimplantation development is unclear. Here, we report that lactate is highly enriched in the nuclei of early embryos when major zygotic genome activation (ZGA) occurs in humans and mice. The inhibition of its production and uptake results in developmental arrest at the 2-cell stage, major ZGA failure, and loss of lactate-derived H3K18lac, which could be rescued by the addition of Lac-CoA and recapitulated by overexpression of H3K18R mutation. By profiling the landscape of H3K18lac during mouse preimplantation development, we show that H3K18lac is enriched on the promoter regions of most major ZGA genes and correlates with their expressions. In humans, H3K18lac is also enriched in ZGA markers and temporally concomitant with their expressions. Taken together, we profile the landscapes of H3K18lac in mouse and human preimplantation embryos, and demonstrate the important role for H3K18lac in major ZGA, showing that a conserved metabolic mechanism underlies preimplantation development of mammalian embryos.

Astaxanthin protects oocyte maturation against cypermethrin-induced defects in pigs.

Cypermethrin (CYP), a pyrethroid insecticide, exerts the detrimental effect on the reproductive system, while astaxanthin (AST), a xanthophyll carotenoid, possesses the powerful antioxidant property and can protect oocyte maturation. However, the toxicity of CYP and the protective role of AST against CYP during oocyte maturation remain unclear. Here, porcine oocytes were applied to investigate the potential effects and underlying mechanisms of CYP and AST during oocyte maturation. This work demonstrated that CYP significantly decreased oocyte maturation rate and subsequent embryo development in a dose-dependent manner (P < 0.05). And, CYP obviously induced the overproduction of reactive oxygen species and the reduction of glutathione content by downregulating the expression of redox genes in oocytes (P < 0.05). Moreover, CYP significantly caused oocyte DNA damage and disturbed the function of endoplasmic reticulum by altering the transcription of DNA damage repair and endoplasmic reticulum stress related genes (P < 0.05). Whereas CYP-exposed oocytes were treated with AST, these defects caused by CYP were significantly ameliorated (P < 0.05). In conclusion, this study demonstrated that CYP exerted the toxic effect on porcine oocytes, while AST effectively alleviated CYP-induced defects. This work provides a potential strategy to prevent pesticide toxicity and protect oocyte maturation in mammalian reproduction.

Near-infrared fluorophore IR-61 improves the quality of oocytes in aged mice via mitochondrial protection.

Maternal aging is associated with a decline in oocyte quality, which leads to the decreased fertility. Therefore, developing approaches to reduce aging-induced deterioration of oocyte quality in older women is important. Near-infrared cell protector-61 (IR-61), a novel heptamethine cyanine dye, has the potential for antioxidant effects. In this study, we found that IR-61 can accumulate in the ovaries and improved ovarian function of naturally aged mice; it also increased the oocyte maturation rate and quality by maintaining the integrity of the spindle/chromosomal structure and reducing the aneuploidy rate. In addition, the embryonic developmental competence of aged oocytes was improved. Finally, RNA-sequencing analysis indicated that IR-61 might perform the beneficial effects on aged oocytes by regulating mitochondrial function, this was confirmed by immunofluorescence analysis of mitochondrial distribution and reactive oxygen species. Taken together, our findings demonstrate that IR-61 supplementation in vivo can increase oocyte quality and protect oocytes from aging-induced mitochondrial dysfunction, and thus could improve the fertility of older women and efficiency of assisted reproductive technology.

Epigenetic Reprogramming During Somatic Cell Nuclear Transfer: Recent Progress and Future Directions.

Somatic cell nuclear transfer (SCNT) has broad applications but is limited by low cloning efficiency. In this review, we mainly focus on SCNT-mediated epigenetic reprogramming in livestock and also describe mice data for reference. This review presents the factors contributing to low cloning efficiency, demonstrates that incomplete epigenetic reprogramming leads to the low developmental potential of cloned embryos, and further describes the regulation of epigenetic reprogramming by long non-coding RNAs, which is a new research perspective in the field of SCNT-mediated epigenetic reprogramming. In conclusion, this review provides new insights into the epigenetic regulatory mechanism during SCNT-mediated nuclear reprogramming, which could have great implications for improving cloning efficiency.

Optimizing 5-aza-2'-deoxycytidine treatment to enhance the development of porcine cloned embryos by inhibiting apoptosis and improving DNA methylation reprogramming.

Apoptosis and incomplete DNA methylation reprogramming in cloned embryos reduce cloning efficiency. 5-aza-2'-deoxycytidine (5-aza-dC) is proven to regulate apoptosis and DNA methylation reprogramming, however, the treatment method and potential role of 5-aza-dC during cloned embryo development are still not well studied. This study displayed that treating donor cells with 5-aza-dC (AN group) significantly reduced the blastocyst rate, while treating cloned embryos (NA group) or both donor cells and cloned embryos (ANA group) significantly promoted the blastocyst formation, and the ANA group was the best treatment of 5-aza-dC to enhance the development of cloned embryos. Then, compared with the NT group, the ANA group showed the significantly enhanced nuclear remodeling. The apoptotic cell numbers and rates of blastocysts were significantly reduced, and the expression levels of significantly upregulated anti-apoptosis gene Bcl2l1 and downregulated pro-apoptosis genes Bax, P53 and Caspase3 were observed in the ANA group. Further study demonstrated that the transcription levels of DNA methylation reprogramming genes Dnmt1, Dnmt3a, Tet1 and Tet3 were significantly upregulated, and, significant genomic DNA remethylation, DNA demethylation of pluripotency gene Oct4, and DNA remethylation of tissue specific gene Thy1 were observed at the blastocyst stage in the ANA group. Embryo development related genes including Igf2, H19, Oct4, Nanog, Sox2, Eif1a, Cdx2 and ATP1b1 were significantly upregulated, and Thy1 and Col5a2 were remarkably silenced at the 4-cell and blastocyst stages in the ANA group. In conclusion, the best 5-aza-dC treatment enhanced the development of cloned embryos by inhibiting apoptosis and improving DNA methylation reprogramming.

Melatonin Enhances the Development of Porcine Cloned Embryos by Improving DNA Methylation Reprogramming.

Incomplete DNA methylation reprogramming in cloned embryos leads to poor cloning efficiency. Melatonin has been proven to improve the development of cloned embryos, however, the role of melatonin during somatic cell nuclear transfer remains unclear. This work demonstrated that 10-7 M melatonin significantly enhanced the developmental progress, reduced the arrested rate before zygotic genome activation, and upregulated the blastocyst rate of cloned embryos. Melatonin also promoted the pseudo-pronucleus formation, increased blastocyst cell number, and reduced embryo apoptosis through upregulating the expression of antiapoptosis factors while downregulating the transcription of proapoptosis genes. Further study displayed that DNA methylation reprogramming related genes were greatly improved in cloned embryos when treated with melatonin; then, melatonin effectively promoted genomic DNA demethylation and DNA remethylation, DNA demethylation of pluripotency related gene Oct4, DNA methylation maintenance of imprinted gene H19/Igf2, and DNA remethylation of tissue-specific gene Thy1 in cloned embryos. Thus, zygotic genome activation related gene Eif1a, pluripotency related genes Oct4, Nanog, and Sox2, imprinted genes Igf2 and H19, and blastocyst quality related genes Cdx2 and ATP1b1 were remarkably upregulated, and tissue-specific genes Thy1 and Col5a2 were considerably silenced. In conclusion, melatonin enhanced the development of cloned embryos by ameliorating DNA methylation reprogramming. This work reveals that melatonin can regulate DNA methylation reprogramming and provides a novel insight to improve cloning efficiency.