TGF-β3 Promotes Trophoblast Development in Sheep Embryos via ACSS2-Dependent Permissive Lipid Metabolism

Transforming growth factor-beta (TGF-β) supports the in vitro maintenance of embryonic and trophoblast stem cells. Here, we demonstrated that, in a sheep embryo model, the transition from morula to blastocyst is positively regulated by TGF-β3, primarily through its promotion of trophoblast development. Our results indicate that morulae treated with TGF-β3 develop at a higher rate into blastocysts, characterized by an expanded trophoblast layer marked by CDX-2 expression. In blastocysts, TGF-β3 mediates transcriptional activation of genes involved in cell adhesion and lipid metabolism pathways, leading to remarkable in vitro outgrowth expansion and a substantial increase in trophoblast lipid droplet content. Functional analysis reveals that the positive effects of TGF-β3 are mitigated by inhibition of Acetyl-CoA Synthetase Short-Chain Family Member 2 (ACSS2), a key enzyme upregulated by TGF-β3 and a promoter of de novo lipogenesis. These findings suggest that TGF-β3 modulates lipid metabolism during blastocyst formation and may play a potential role in regulating implantation and placental development.