Hospital of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
Guangdong Provincial Key Laboratory of Stomatology, Guangzhou 510055, China.
J Bone Miner Res. 2024 Sep 2;39(9):1356-1370. doi: 10.1093/jbmr/zjae121.
The skeleton is a metabolically active organ undergoing continuous remodeling initiated by bone marrow stem cells (BMSCs). Recent research has demonstrated that BMSCs adapt the metabolic pathways to drive the osteogenic differentiation and bone formation, but the mechanism involved remains largely elusive. Here, using a comprehensive targeted metabolome and transcriptome profiling, we revealed that one-carbon metabolism was promoted following osteogenic induction of BMSCs. Methotrexate (MTX), an inhibitor of one-carbon metabolism that blocks S-adenosylmethionine (SAM) generation, led to decreased N6-methyladenosine (m6A) methylation level and inhibited osteogenic capacity. Increasing intracellular SAM generation through betaine addition rescued the suppressed m6A content and osteogenesis in MTX-treated cells. Using S-adenosylhomocysteine (SAH) to inhibit the m6A level, the osteogenic activity of BMSCs was consequently impeded. We also demonstrated that the pro-osteogenic effect of m6A methylation mediated by one-carbon metabolism could be attributed to HIF-1α and glycolysis pathway. This was supported by the findings that dimethyloxalyl glycine rescued the osteogenic potential in MTX-treated and SAH-treated cells by upregulating HIF-1α and key glycolytic enzymes expression. Importantly, betaine supplementation attenuated MTX-induced m6A methylation decrease and bone loss via promoting the abundance of SAM in rat. Collectively, these results revealed that one-carbon metabolite SAM was a potential promoter in BMSC osteogenesis via the augmentation of m6A methylation, and the cross talk between metabolic reprogramming, epigenetic modification, and transcriptional regulation of BMSCs might provide strategies for bone regeneration.
骨骼是一个代谢活跃的器官，不断进行由骨髓干细胞（BMSCs）启动的重塑。最近的研究表明，BMSCs 会适应代谢途径以驱动成骨分化和骨形成，但涉及的机制在很大程度上仍不清楚。在这里，我们使用全面的靶向代谢组学和转录组谱分析，揭示了 BMSCs 在成骨诱导后，一碳代谢被促进。甲氨蝶呤（MTX）是一种一碳代谢抑制剂，可阻断 S-腺苷甲硫氨酸（SAM）的生成，导致 N6-甲基腺苷（m6A）甲基化水平降低，并抑制成骨能力。通过添加甜菜碱增加细胞内 SAM 的生成，挽救了 MTX 处理细胞中受抑制的 m6A 含量和成骨作用。使用 S-腺苷同型半胱氨酸（SAH）抑制 m6A 水平，BMSCs 的成骨活性受到阻碍。我们还证明，一碳代谢介导的 m6A 甲基化的促成骨作用可归因于 HIF-1α 和糖酵解途径。这一发现得到了以下结果的支持：二甲草酰基甘氨酸通过上调 HIF-1α 和关键糖酵解酶的表达，挽救了 MTX 处理和 SAH 处理细胞的成骨潜能。重要的是，甜菜碱补充通过促进 SAM 在大鼠中的丰度，减轻了 MTX 诱导的 m6A 甲基化减少和骨丢失。总的来说，这些结果表明，一碳代谢物 SAM 通过增强 m6A 甲基化成为 BMSC 成骨的潜在促进剂，代谢重编程、表观遗传修饰和 BMSCs 转录调控之间的相互作用可能为骨再生提供策略。
