TGFB1 is a major factor for DNA demethylation and development of embryos

Components in the oviduct are crucial for embryonic development, are follicular fluid (FF) is considered a potential source of these factors. This study investigated FF-derived molecules that influence bovine embryonic development and global DNA methylation. Bovine oocyte and FF were collected from antral follicles of slaughterhousE−derived ovaries. Treatment of in vitro-fertilized zygotes with 1% FF for 30 h significantly reduced global DNA methylation levels in embryos at the 8-cell and blastocyst stages, an effect that persisted after removal of extracellular vesicles. RNA-seq analysis predicted transforming growth factor beta 1 (TGFB1) as an activated upstream regulator in FF-treated 8-cell stage embryos. Supplementation of in vitro culture medium with TGFB1-enriched FF improved embryonic development and reduced DNA methylation at the 8-cell and blastocyst stage embryos. TGFB1 concentration in FF were independent of estradiol levels but were associated with matrix metallopeptidase 2 (MMP2) expression. RNA-seq analysis of granulosa cells from TGFB1-enriched follicles further supported TGFB1 activation. Supplementation of embryo culture medium with TGFB1 promoted DNA demethylation, increased TET3A expression and H3K4 trimethylation, reduced H3K9 trimethylation, enhanced nuclear localization of yes-associated protein 1 (YAP1), and altered autophagy- and mitophagy-related gene expression. These findings demonstrate that TGFB1 plays a key role in regulating bovine embryonic development and epigenetic remodeling.