# TGF-β3 promotes trophoblast development in sheep embryos via ACSS2-dependent permissive lipid metabolism

## TL;DR

TGF-β3 helps sheep embryos develop by boosting trophoblast growth through lipid metabolism.

## Contribution

TGF-β3's role in promoting trophoblast development via ACSS2-dependent lipid metabolism in sheep embryos is newly identified.

## Key findings

- TGF-β3 increases blastocyst formation by expanding the trophoblast layer marked by CDX-2.
- TGF-β3 activates genes for cell adhesion and lipid metabolism, increasing lipid droplets in trophoblasts.
- ACSS2 inhibition reduces TGF-β3's positive effects, showing its role in de novo lipogenesis.

## Abstract

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.

TGF-β3 promotes trophoblast development in sheep.

Graphical Abstract