Whether mitochondrial remodeling and metabolic reprogramming occur during the differentiation of human embryonic stem cells (hESCs) to definitive endoderm (DE) is unknown. We found that fragmented and punctate mitochondria in undifferentiated hESCs progressively fused into an extensive and branched network upon DE differentiation. Mitochondrial mass and mitochondrial DNA (mtDNA) content were significantly increased with the upregulated expression of mitochondrial biogenesis regulator PGC1-A upon DE differentiation, accompanied by the rise of the amount of ATP (2.5-fold) and its by-product reactive oxygen species (2.0-fold). We observed that in contrast to a shutoff of glycolysis, expressions of oxidative phosphorylation (OXPHOS) genes were increased, indicating that a transition from glycolysis to OXPHOS was tightly coupled to DE differentiation. In the meantime, we discovered that inhibition of TGF-β signaling led to impaired mitochondrial biogenesis and disturbed metabolic switch upon DE differentiation. Our work, for the first time, reports that TGF-β signaling–dependent mitochondrial biogenesis and metabolic reprogramming occur during early endodermal differentiation.

尚不清楚在人类胚胎干细胞（hESCs）向定形内胚层（DE）分化过程中是否发生线粒体重塑和代谢重编程。我们发现未分化的hESCs中的碎片和点状线粒体在DE分化后逐渐融合成一个广泛的分支网络。随着线粒体生物发生调节因子PGC1-A表达的上调，线粒体质量和线粒体DNA含量明显增加。在DE分化后，伴随着ATP量的增加（2.5倍）及其副产物活性氧（2.0倍）。我们观察到与糖酵解的关闭相反，氧化磷酸化（OXPHOS）基因的表达增加，表明从糖酵解到OXPHOS的过渡与DE分化紧密相关。同时，我们发现抑制TGF-β信号传导会导致线粒体生物发生受损，并影响DE分化后的代谢转换。我们的工作首次报道在早期内胚层分化过程中发生了TGF-β信号依赖的线粒体生物发生和代谢重编程。