The effects of ascorbate on adult cell fate specification remain largely unknown. Using our stepwise and chemically defined system to derive lateral mesoderm progenitors from human pluripotent stem cells (hPSCs), we found that ascorbate increased the expression of mesenchymal stromal cell (MSC) markers, purity of MSCs, the long-term self-renewal and osteochondrogenic capacity of hPSC-MSCs in vitro. Moreover, ascorbate promoted MSC specification in an iron-dependent fashion, but not in a redox-dependent manner. Further studies revealed that iron synergized with ascorbate to regulate hPSC-MSC histone methylation, promote their long-term self-renewal, and increase their osteochondrogenic capacity. We found that one of the histone demethylases affected by ascorbate, KDM4B, was necessary to promote the specification of hPSC-MSCs. This mechanistic understanding led to the metabolic optimization of hPSC-MSCs with an extended lifespan in vitro and the ability to fully repair cartilage defects upon transplantation in vivo. Our results highlight the importance of ascorbate and iron metabolism in adult human cell fate specification.

抗坏血酸对成年细胞命运规范的影响仍然未知。使用我们的逐步化学定义系统从人多能干细胞（hPSCs）衍生中胚层外侧祖细胞，我们发现抗坏血酸盐可提高间充质基质细胞（MSC）标记物的表达，MSC的纯度，长期自我更新和成骨软骨细胞hPSC-MSCs体外能力。此外，抗坏血酸以铁依赖的方式促进了MSC的规范，但不是以氧化还原的方式促进了。进一步的研究表明，铁与抗坏血酸协同作用来调节hPSC-MSC组蛋白甲基化，促进其长期自我更新，并增加其骨软骨形成能力。我们发现受抗坏血酸影响的一种组蛋白脱甲基酶KDM4B对于促进hPSC-MSC的规格是必要的。这种机理上的理解导致了hPSC-MSC在体外的使用寿命延长以及在体内移植后完全修复软骨缺损的能力方面的代谢优化。我们的结果突出了抗坏血酸和铁代谢在成人细胞命运规范中的重要性。