Cardiomyocyte cell cycle activity in injured hearts

心肌细胞周期诱导提供了心肌质量恢复的可能性， 心脏损伤后的收缩功能。因此，投入了相当大的努力来研究学位， 在正常和损伤的成人中，心肌细胞可以重新进入细胞周期并通过胞质分裂进行进展， 哺乳动物的心脏使用转基因报告系统鉴定组织切片中的心肌细胞核 结合连续BrdU输注，我们开发了一种数字成像和分析系统， 允许对整个心肌细胞的累积S期活动进行定量和3D解剖学映射。 整个心。使用这个系统，我们观察到离散的心肌细胞S期活动的集群， 永久性冠状动脉结扎我们还观察到在心肌细胞S期活动的高比率， 缺血/再灌注（I/R）损伤小鼠远端心肌。本申请中提出的研究将 确定观察到的不同心肌细胞细胞周期反应的潜在机制基础 心肌损伤后。在特定目标1中，心肌细胞S期诱导和细胞周期的变异性 将建立永久性冠状动脉结扎后的进展，所得数据集将 然后用于数学建模，目的是建立采样标准以定量总心脏 心肌细胞S期活动，考虑到这些内在的解剖学变化。其他研究 将确定所观察到的S期活性簇是否来自于 心肌细胞保留了细胞周期重新进入的潜力。在特定目标2中，将进行I/R损伤 在保持在近交遗传背景中的报告小鼠中，以确定损伤的性质和/或程度 负责远端心肌中高水平的细胞周期诱导。其他研究将利用 信息回交，以确定修饰基因影响心肌细胞周期的程度 I/R损伤后再进入。在这两个目的中，S期阳性心肌细胞进展的程度 也将对细胞周期进行定量。拟议的实验将建立一个3D地图集， 心肌细胞S期活动响应于常用的和临床相关的损伤模型，并将 确定心肌细胞DNA合成水平的增加对多倍化的贡献程度， 多核化和/或心肌细胞更新。此外，这些实验将描述 性别、遗传背景和损伤方式对心肌细胞周期重入的影响 以确定心肌细胞周期活动的自然变化对心脏功能的影响 受伤后。这些数据将为制定干预策略提供有用的见解， 促进心脏的再生生长，并为旨在 在诱导心肌细胞更新方面。

Cardiomyocyte cell cycle induction offers the potential for restoration of myocardial mass, and consequently contractile function, following cardiac injury. Considerable effort has thus been invested studying the degree to which cardiomyocytes can reenter the cell cycle and progress through cytokinesis in normal and injured adult mammalian hearts. Using a transgenic reporter system to identify cardiomyocyte nuclei in tissue sections in conjunction with continuous BrdU infusion, we have developed a digital imaging and analysis system which permits both quantitation and 3D anatomical mapping of cumulative cardiomyocyte S-phase activity across the entire heart. Using this system, we observed discrete clusters of cardiomyocyte S-phase activity in mice with permanent coronary artery ligation. We also observed very high rates of cardiomyocyte S-phase activity in the remote myocardium of mice with ischemia/reperfusion (I/R) injury. The studies proposed in this application will identify the underlying mechanistic basis for the differential cardiomyocyte cell cycle responses observed following myocardial injury. In Specific Aim 1, the variability in cardiomyocyte S-phase induction and cell cycle progression following permanent coronary artery ligation will be established and the resulting data sets will then be used for mathematical modeling with the goal of establish sampling criteria to quantitate total heart cardiomyocyte S-phase activity which takes into account these intrinsic anatomical variations. Other studies will determine if the observed clusters of S-phase activity arise from the clonal expansion of a subset of cardiomyocytes which retain the potential for cell cycle reentry. In Specific Aim 2, I/R injury will be performed in reporter mice maintained in an inbred genetic background to determine if the nature and/or degree of injury are responsible for high levels of cell cycle induction in the remote myocardium. Other studies will utilize informative backcrosses to determine the extent to which modifying genes can impact cardiomyocyte cell cycle reentry following I/R injury. In both Aims, the degree to which the S-phase positive cardiomyocytes progress through the cell cycle will also be quantitated. The proposed experiments will establish a 3D atlas of cardiomyocyte S-phase activity in response to commonly used and clinically relevant injury models, and will establish the degree to which increased levels of cardiomyocyte DNA synthesis contribute to polyploidization, multi-nucleation, and/or cardiomyocyte renewal. In addition, these experiments will characterize the impact of gender, genetic background and mode of injury on the magnitude of cardiomyocyte cell cycle reentry, as well as determine the consequences of natural variation in cardiomyocyte cell cycle activity on cardiac function post-injury. These data will provide useful insight for the development of interventional strategies with which to promote regenerative growth of the heart, as well as provide a comprehensive reference set for studies aimed at inducing cardiomyocyte renewal.