Cardiomyocyte cell cycle activity in injured hearts

诱导心肌细胞周期提供了恢复心肌质量的可能性，从而 心脏损伤后的收缩功能。因此，人们投入了相当大的精力来研究 正常和损伤成人中哪些心肌细胞可以通过胞质分裂重新进入细胞周期和进展 哺乳动物的心脏。应用转基因报告系统鉴定大鼠心肌组织切片中的心肌细胞核 结合连续输注BrdU，我们开发了一套数字成像和分析系统，该系统 允许定量和3D解剖标测心肌细胞S时相的累积活动。 整颗心。利用该系统，我们观察到小鼠心肌细胞S时相活动的离散簇。 永久性冠状动脉结扎术。我们还观察到心肌细胞S时相活动率很高。 缺血/再灌流损伤小鼠远隔心肌。本申请书中建议的研究将 确定观察到的不同心肌细胞周期反应的潜在机制基础 在心肌损伤之后。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，结果数据集将 然后用于数学建模，目的是建立采样标准以量化总心脏 考虑到这些内在解剖变异的心肌细胞S时相活动。其他研究 将确定所观察到的S相活动的星团是否来自 保留细胞周期重入潜能的心肌细胞。在具体目标2中，将进行I/R损伤 在保持近亲繁殖遗传背景的报告鼠中，以确定损伤的性质和/或程度 在遥远的心肌中负责高水平的细胞周期诱导。其他研究将利用 确定修饰基因影响心肌细胞周期的程度的信息性回交 I/R损伤后再入。在这两个目标中，S期阳性心肌细胞的进展程度 通过细胞周期也会被量化。拟议的实验将建立一个3D地图集 常用和临床相关损伤模型对心肌细胞S时相活动的影响 确定心肌细胞DNA合成水平增加对多倍化的贡献程度， 多核和/或心肌细胞更新。此外，这些实验将表征 性别、遗传背景和损伤方式对心肌细胞周期折返程度的影响 AS测定心肌细胞周期活动自然变异对心功能的影响 受伤后。这些数据将为制定干预策略提供有用的见解，以便 促进心脏的再生生长，并为研究提供全面的参考 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.