Division of Cardiology, Department of Medicine, Heart Rhythm Center (P.-C.C., C.-M.L., C.-H.W., J.-D.L., Y.-F.H.), Taipei Veterans General Hospital, Taiwan.
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan (P.-C.C., C.-H.W., K.-C.Y., Y.-C.L., R.-B.Y., B.-C.S., S.-K.S., J.-D.L., Y.-F.H.).
Circ Res. 2022 Jun 24;131(1):6-20. doi: 10.1161/CIRCRESAHA.121.320301. Epub 2022 May 25.
The sino atrial node (SAN) is characterized by the microenvironment of pacemaker cardiomyocytes (PCs) encased with fibroblasts. An altered microenvironment leads to rhythm failure. Operable cell or tissue models are either generally lacking or difficult to handle. The biological process behind the milieu of SANs to evoke pacemaker rhythm is unknown. We explored how fibroblasts interact with PCs and regulate metabolic reprogramming and rhythmic activity in the SAN.
Tbx18 (T-box transcription factor 18)-induced PCs and fibroblasts were used for cocultures and engineered tissues, which were used as the in vitro models to explore how fibroblasts regulate the functional integrity of SANs. RNA-sequencing, metabolomics, and cellular and molecular techniques were applied to characterize the molecular signals underlying metabolic reprogramming and identify its critical regulators. These pathways were further validated in vivo in rodents and induced human pluripotent stem cell-derived cardiomyocytes.
We observed that rhythmicity in Tbx18-induced PCs was regulated by aerobic glycolysis. Fibroblasts critically activated metabolic reprogramming and aerobic glycolysis within PCs, and, therefore, regulated pacemaker activity in PCs. The metabolic reprogramming was attributed to the exclusive induction of Aldoc (aldolase c) within PCs after fibroblast-PC integration. Fibroblasts activated the integrin-dependent mitogen-activated protein kinase-E2F1 signal through cell-cell contact and turned on Aldoc expression in PCs. Interruption of fibroblast-PC interaction or Aldoc knockdown nullified electrical activity. Engineered Tbx18-PC tissue sheets were generated to recapitulate the microenvironment within SANs. Aldoc-driven rhythmic machinery could be replicated within tissue sheets. Similar machinery was faithfully validated in de novo PCs of adult mice and rats, and in human PCs derived from induced pluripotent stem cells.
Fibroblasts drive Aldoc-mediated metabolic reprogramming and rhythmic regulation in SANs. This work details the cellular machinery behind the complex milieu of vertebrate SANs and opens a new direction for future therapy.
窦房结 (SAN) 的特征是被成纤维细胞包裹的起搏心肌细胞 (PCs) 的微环境。微环境的改变会导致节律衰竭。可操作的细胞或组织模型通常缺乏或难以处理。SAN 微环境背后引发起搏节律的生物学过程尚不清楚。我们探讨了成纤维细胞如何与 PCs 相互作用，并调节 SAN 中的代谢重编程和节律活动。
使用 Tbx18（T 盒转录因子 18）诱导的 PCs 和成纤维细胞进行共培养和工程组织，将其作为体外模型来探讨成纤维细胞如何调节 SAN 功能完整性。应用 RNA 测序、代谢组学以及细胞和分子技术来描述代谢重编程的分子信号，并鉴定其关键调控因子。这些途径在体内啮齿动物和诱导人多能干细胞衍生的心肌细胞中进一步得到验证。
我们观察到 Tbx18 诱导的 PCs 中的节律性受有氧糖酵解调节。成纤维细胞在 PCs 中关键地激活了代谢重编程和有氧糖酵解，因此调节了 PCs 中的起搏活性。代谢重编程归因于成纤维细胞-PC 整合后 PCs 中 Aldoc（醛缩酶 c）的特异性诱导。成纤维细胞通过细胞-细胞接触激活整合素依赖性丝裂原活化蛋白激酶-E2F1 信号，从而开启 PCs 中的 Aldoc 表达。中断成纤维细胞-PC 相互作用或 Aldoc 敲低会使电活性丧失。生成工程 Tbx18-PC 组织片以重现 SAN 内的微环境。Aldoc 驱动的节律机制可以在组织片中复制。类似的机制在成年小鼠和大鼠的新生 PCs 中以及诱导多能干细胞衍生的人类 PCs 中得到了忠实验证。
成纤维细胞驱动 SAN 中的 Aldoc 介导的代谢重编程和节律调节。这项工作详细说明了脊椎动物 SAN 复杂微环境背后的细胞机制，并为未来的治疗开辟了新的方向。
