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Embryonic genome activation (EGA) is a critical step during embryonic development. Several transcription factors have been identified that play major roles in initiating EGA; however, this gradual and complex mechanism still needs to be explored. In this study, we investigated the role of nuclear transcription factor Y subunit A (NFYA) in bovine EGA and bovine embryonic development and its relationship with the platelet-derived growth factor receptor-β (PDGFRβ) by using a potent selective activator (PDGF-BB) and inhibitor (CP-673451) of PDGF receptors. Activation and inhibition of PDGFRβ using PDGF-BB and CP-673451 revealed that NFYA expression is significantly (p < 0.05) affected by the PDGFRβ. In addition, PDGFRβ mRNA expression was significantly increased (p < 0.05) in the activator group and significantly decreased (p < 0.05) in the inhibitor group when compared with PDGFRα. Downregulation of NFYA following PDGFRβ inhibition was associated with the expression of critical EGA-related genes, bovine embryo development rate, and implantation potential. Moreover, ROS and mitochondrial apoptosis levels and expression of pluripotency-related markers necessary for inner cell mass development were also significantly (p < 0.05) affected by the downregulation of NFYA while interrupting trophoblast cell (CDX2) differentiation. In conclusion, the PDGFRβ-NFYA axis is critical for bovine embryonic genome activation and embryonic development. [ABSTRACT FROM AUTHOR]

Context: Telomerase reverse transcriptase is a key factor responsible for structural and cellular alterations in aged oocytes and changes in the structure of the zona pellucida and mitochondria. Telomerase expression is reduced in aged cumulus oocyte complexes, and its activation or enhanced expression would be beneficial for in vitro oocyte maturation and in vitro embryo development. Aims: This study aimed to investigate telomerase activation by cycloastragenol and its effect on bovine oocyte in vitro maturation, fertilisation, and early embryo development. Methods: We used qPCR, Western blot, immunofluorescence, reactive oxygen species (ROS) assay,TUNEL assay, JC-1 assay, and invasion assay to analyse the affect of cycloastragenol (CAG) on bovine oocyte maturation, embryo development, embryo quality and implantation potential. Key results: Cycloastragenol treatment of oocytes in in vitro maturation (IVM) media significantly (P < 0.05) improved oocyte IVM (90.87%), embryo cleavage (90.78%), blastocyst hatching (27.04%), and embryo implantation potential. Telomerase also interacts with mitochondria, and JC-1 staining results showed significantly (P < 0.05) higher mitochondrial membrane potential (Δ Ψ m) in the CAG-treated group. Furthermore, the inner cell mass (OCT4 and SOX2) and trophoblasts (CDX2) of the control and CAG groups were examined. Moreover, CAG treatment to primary cultured bovine cumulus cells substantially enhanced telomerase activity. Conclusions: Telomerase activation via cycloastragenol is beneficial for bovine oocyte IVM and for the production of high-quality bovine embryos. Implications: Cycloastragenol is a natural telomerase activator, and could be useful as a permanent component of oocyte maturation media. The female reproductive system is more vulnerable to ageing, and advanced maternal age affects embryo development. Pre-implanted embryos grown in the lab also exhibit ageing like characteristics due to in vitro conditions. We employed cycloastragenol, a naturally occurring substance with reported anti-aging and healing properties, in embryo growth media. Cycloastragenol greatly increased telomerase expression levels, enhanced embryo quality, and increased the embryo's ability for implantation. We suggest that cycloastragenol might constitute a valuable addition to media used for oocyte maturation and embryo development. [ABSTRACT FROM AUTHOR]

Transforming growth factor-beta (TGF-β) plays a critical role in regulating trophoblast invasion and proliferation. Growth differentiation factor-8 (GDF-8) is a member of the TGF-β superfamily and is categorized as a myostatin subtype. It is primarily a secreted protein synthesized in skeletal muscle cells. It is expressed in the placenta, reproductive tissues, and cells. In this study, we investigated the role of GDF-8 in the development and hatching rate of bovine embryos. We noted a notable elevation ( p < 0.05) in the development and hatching rates compared to the control embryos. Furthermore, the GDF-8 group showed a significantly improved total cell number ( p < 0.05) and an increase in trophectoderm ratio inner cell mass (trophectoderm: inner cell mass) cells ( p < 0.001) compared to the control group. Additionally, blastocysts treated with GDF-8 exhibited significantly higher mRNA levels of caudal-type homeobox 2 ( CDX2 ) ( p < 0.05). The trophoblast invasion area was significantly larger in the GDF-8 group than in the control group ( p < 0.01). Furthermore, qRT-PCR analysis revealed significantly higher mRNA levels ( p < 0.05) of matrix metalloproteinases 9 ( MMP9 ) and follistatin-like 3( FSTL3 ), both of which are associated with the ALK5-SMAD2/3 signaling pathway, in the GDF-8 group than those in the control group. The mRNA expression levels of genes related to tight junctions (TJ) and adherent junctions were higher in the GDF-8 group than those in the control group ( p < 0.05). After 24 h of thawing, blastocysts were analyzed using 4-kDa FITC-dextran, which revealed a higher TJ integrity in the GDF-8 group ( p < 0.01). Thus, GDF-8 plays a crucial role in bovine embryonic development, in vitro implantation, and cryotolerance., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Kang, Idrees, Perera, Lee, Zhang, Yu, Jin and Kong.)