Wang Wei Eric, Li Liangpeng, Xia Xuewei, Fu Wenbin, Liao Qiao, Lan Cong, Yang Dezhong, Chen Hongmei, Yue Rongchuan, Zeng Cindy, Zhou Lin, Zhou Bin, Duan Dayue Darrel, Chen Xiongwen, Houser Steven R, Zeng Chunyu
From Department of Cardiology, Chongqing Institute of Cardiology and Chongqing Cardiovascular Clinical Research Center, Daping Hospital, Third Military Medical University, China (W.E.W., L.L., X.X., W.F., Q.L., C.L., D.Y., H.C., R.Y., C.S.Z., L.Z., X.C., C.Z.); State Key Laboratory of Cell Biology, CAS Center for Excellence in Molecular Cell Science, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, China (B.Z.); Laboratory of Cardiovascular Phenomics, Center for Molecular Medicine, Department of Pharmacology, University of Nevada School of Medicine, Reno (D.D.D.); and Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, PA (X.C., S.R.H.).
Circulation. 2017 Aug 29;136(9):834-848. doi: 10.1161/CIRCULATIONAHA.116.024307. Epub 2017 Jun 22.
Adult mammalian hearts have a limited ability to generate new cardiomyocytes. Proliferation of existing adult cardiomyocytes (ACMs) is a potential source of new cardiomyocytes. Understanding the fundamental biology of ACM proliferation could be of great clinical significance for treating myocardial infarction (MI). We aim to understand the process and regulation of ACM proliferation and its role in new cardiomyocyte formation of post-MI mouse hearts.
β-Actin-green fluorescent protein transgenic mice and fate-mapping Myh6-MerCreMer-tdTomato/lacZ mice were used to trace the fate of ACMs. In a coculture system with neonatal rat ventricular myocytes, ACM proliferation was documented with clear evidence of cytokinesis observed with time-lapse imaging. Cardiomyocyte proliferation in the adult mouse post-MI heart was detected by cell cycle markers and 5-ethynyl-2-deoxyuridine incorporation analysis. Echocardiography was used to measure cardiac function, and histology was performed to determine infarction size.
In vitro, mononucleated and bi/multinucleated ACMs were able to proliferate at a similar rate (7.0%) in the coculture. Dedifferentiation proceeded ACM proliferation, which was followed by redifferentiation. Redifferentiation was essential to endow the daughter cells with cardiomyocyte contractile function. Intercellular propagation of Ca from contracting neonatal rat ventricular myocytes into ACM daughter cells was required to activate the Ca-dependent calcineurin-nuclear factor of activated T-cell signaling pathway to induce ACM redifferentiation. The properties of neonatal rat ventricular myocyte Ca transients influenced the rate of ACM redifferentiation. Hypoxia impaired the function of gap junctions by dephosphorylating its component protein connexin 43, the major mediator of intercellular Ca propagation between cardiomyocytes, thereby impairing ACM redifferentiation. In vivo, ACM proliferation was found primarily in the MI border zone. An ischemia-resistant connexin 43 mutant enhanced the redifferentiation of ACM-derived new cardiomyocytes after MI and improved cardiac function.
Mature ACMs can reenter the cell cycle and form new cardiomyocytes through a 3-step process: dedifferentiation, proliferation, and redifferentiation. Intercellular Ca signal from neighboring functioning cardiomyocytes through gap junctions induces the redifferentiation process. This novel mechanism contributes to new cardiomyocyte formation in post-MI hearts in mammals.
成年哺乳动物心脏生成新心肌细胞的能力有限。现有的成年心肌细胞（ACMs）增殖是新心肌细胞的一个潜在来源。了解ACMs增殖的基本生物学特性对于治疗心肌梗死（MI）可能具有重大临床意义。我们旨在了解ACMs增殖的过程和调控及其在MI后小鼠心脏新心肌细胞形成中的作用。
使用β-肌动蛋白-绿色荧光蛋白转基因小鼠和命运图谱Myh6-MerCreMer-tdTomato/lacZ小鼠来追踪ACMs的命运。在与新生大鼠心室肌细胞的共培养系统中，通过延时成像观察到有明显的胞质分裂证据，记录了ACMs的增殖情况。通过细胞周期标记物和5-乙炔基-2'-脱氧尿苷掺入分析检测成年小鼠MI后心脏中的心肌细胞增殖。使用超声心动图测量心脏功能，并进行组织学检查以确定梗死面积。
在体外，单核和双核/多核ACMs在共培养中能够以相似的速率（7.0%）增殖。去分化先于ACMs增殖，随后是再分化。再分化对于赋予子代细胞心肌细胞收缩功能至关重要。需要将收缩的新生大鼠心室肌细胞中的Ca通过细胞间传播到ACMs子代细胞中，以激活钙依赖性钙调神经磷酸酶-活化T细胞信号通路的核因子来诱导ACMs再分化。新生大鼠心室肌细胞Ca瞬变的特性影响ACMs再分化的速率。缺氧通过使其组成蛋白连接蛋白43去磷酸化来损害缝隙连接的功能，连接蛋白43是心肌细胞间细胞间Ca传播的主要介质，从而损害ACMs再分化。在体内，发现ACMs增殖主要发生在MI边缘区。一种抗缺血的连接蛋白43突变体增强了MI后ACMs来源的新心肌细胞的再分化并改善了心脏功能。
成熟的ACMs可以重新进入细胞周期，并通过去分化、增殖和再分化这三个步骤形成新的心肌细胞。来自相邻功能正常心肌细胞的细胞间Ca信号通过缝隙连接诱导再分化过程。这一新机制有助于哺乳动物MI后心脏中新心肌细胞的形成。
