a-Ketoglutarate Promotes Cardiomyocyte Proliferation and Heart Regeneration after Myocardial Infarction

The neonatal mammalian heart is capable of substantial regeneration following injury through cardiomyocyte proliferation. However, this regenerative capacity is lost by postnatal (P) day 7. How to stimulate the adult cardiomyocyte to re-enter the cell cycle is still unknown. Accumulating evidence suggests that cardiomyocyte proliferation depends on its metabolic state. Due to the tight connection between the tricarboxylic acid cycle (TCA) and cell proliferation, we analyzed the TCA metabolites between P0.5 and P7 mouse hearts and found that a-ketoglutarate (a-KG) ranked first among the decreased metabolites. The intraperitoneal injection of exogenous a-KG extended the window of cardiomyocyte proliferation during heart development and promoted heart regeneration after myocardial infarction (MI) by inducing adult cardiomyocyte proliferation. This was confirmed in Ogdh-siRNA-treated mice with increased a-KG levels. Mechanistically, a-KG activates Jmjd3, a histone lysine demethylase, that decreases H3K27me3 expression and deposition of H3K4me3 at the promoters of cell cycle and structural maturation genes in cardiomyocytes. Our present study shows that a-KG promotes cardiomyocyte proliferation by Jmjd3-dependent demethylation and inactivation of H3K27me3 andH3K4me3, which is a potential therapeutic approach for treating MI and heart failure. Overall design: To gain insights into the potential pathways by which a-KG induced cardiomyocyte proliferation, we isolated cardiomyocytes from P21 mice that were daily injected with a-KG or PBS (Control) for 2 weeks and performed gene expression profiling analysis using data obtained from RNA-seq.

新生哺乳动物心脏可通过心肌细胞增殖实现损伤后的显著再生修复。然而，该再生能力会在出生后第7天（P7）丧失。如何诱导成年心肌细胞重新进入细胞周期，仍是尚未明确的科学问题。日益积累的研究证据表明，心肌细胞增殖与其代谢状态密切相关。鉴于三羧酸循环（TCA）与细胞增殖间存在紧密关联，我们分析了出生后0.5天（P0.5）至P7小鼠心脏的TCA代谢物谱，发现α-酮戊二酸（α-KG）是丰度下降最为显著的代谢物。向小鼠腹腔注射外源性α-KG，可延长心脏发育过程中心肌细胞增殖的窗口期，并通过诱导成年心肌细胞增殖，促进心肌梗死（MI）后的心脏再生修复。这一结论在α-酮戊二酸脱氢酶（Ogdh）siRNA处理、体内α-KG水平升高的小鼠模型中得到了验证。从机制层面而言，α-KG可激活组蛋白赖氨酸去甲基化酶Jmjd3，后者可降低心肌细胞中细胞周期基因与结构成熟基因启动子区域的H3K27me3（组蛋白H3第27位赖氨酸三甲基化）修饰水平，并调控H3K4me3（组蛋白H3第4位赖氨酸三甲基化）的沉积。本研究证实，α-KG可通过Jmjd3依赖的去甲基化作用，调控H3K27me3与H3K4me3的修饰状态以促进心肌细胞增殖，这为心肌梗死（MI）与心力衰竭的临床治疗提供了潜在策略。整体实验设计：为解析α-KG诱导心肌细胞增殖的潜在通路，我们从每日注射α-KG或磷酸盐缓冲液（PBS，对照组）、连续给药2周的21日龄（P21）小鼠中分离心肌细胞，利用RNA测序（RNA-seq）获得的转录组数据开展基因表达谱分析。