Impact of cardiomyocyte cell cycle activity on atrial structural and functional remodeling following myocardial infarction

实验和临床研究都表明，慢性心肌梗死与 左房不良重塑，进而对左房功能产生不利影响。左房 扩张是心肌梗死后死亡率的一个强大而独立的预测因子，但其机制 人们对重塑过程背后的原因知之甚少。令人惊讶的是，我们观察到了非常高的比率 心肌梗死小鼠左心房心肌细胞周期活性的变化。然而，心肌细胞的作用 循环活动在减轻或加剧心肌梗死后结构和/或功能重构中的作用 目前尚不清楚是否有脑梗塞。为了直接解决这个问题，我们创造了一个转基因小鼠模型，其中 P16-INK4A(P16)表达继发于梗塞诱导的左心房细胞周期活动沉默(p16是一种有效的 已有研究表明，在成年动物中存在增殖激酶CDK4的抑制和转基因表达 成为一种有效的细胞周期抑制物)。在这里，我们建议比较野生型和p16转基因小鼠，以确定 左房心肌细胞周期激活对左房结构和功能重构的影响 脑梗塞。目标1中提出的实验将确定心肌细胞周期活动的程度 影响心肌梗死后结构性心房重构。将对左房结构进行分析 在组织水平上执行(A)以量化心肌质量、心肌细胞数量、纤维化、免疫细胞 渗透、自主神经支配和毛细血管密度，(B)在心肌细胞水平上定量 细胞周期进程和细胞肥大以及心肌细胞凋亡的频率，以及(C)在 分子水平来量化转录组的变化。目标2中提出的实验将决定 心肌梗死后心肌细胞周期活动对心房功能的影响程度。心房 将在整个生物体水平上进行功能分析，以量化超声心动图和 血流动力学参数，(B)在完整的心脏水平，以定量钙和电压瞬变参数 左心房(通过光学标测)和完整心脏内的细胞团(通过双光子激光扫描 (C)在分离的细胞水平上，以量化分数缩短和钙处理动力学。 重要的是，将AIM 1的细胞和分子数据与来自的成像和功能数据进行交叉参考 目标2应该使我们能够更好地确定哪些细胞周期介导的变化对心脏有相关影响 功能。这些信息可能暗示了旨在逆转左心房功能受损的干预措施。 梗塞的心脏。

Both experimental and clinical studies have demonstrated that chronic myocardial infarction is associated with adverse remodeling of the left atrium, which in turn has an adverse impact on left atrial function. Left atrial dilatation is a powerful and independent predictor of mortality after myocardial infarction, but the mechanisms underlying the remodeling process are only poorly understood. Surprisingly, we have observed very high rates of cardiomyocyte cell cycle activity in the left atrium of infarcted mice. However, the role that cardiomyocyte cell cycle activity plays in mitigating or exacerbating structural and/or functional remodeling following myocardial infarction is not known. To directly address this question, we have generated a transgenic mouse model wherein infarct-induced left atrial cell cycle activity is silenced secondary to p16-Ink4a (p16) expression (p16 is a potent inhibitor of the proliferative kinase Cdk4 and transgenic expression in adult animals has previously been shown to be a potent cell cycle inhibitor). Here we propose to compare wild-type and p16 transgenic mice to determine the impact of atrial cardiomyocyte cell cycle activation on left atrial structural and functional remodeling following infarction. The experiments proposed in Aim 1 will determine the degree to which cardiomyocyte cell cycle activity impacts structural atrial remodeling following myocardial infarction. Left atrial structural analyses will be performed (a) at the tissue level to quantitate myocardial mass, cardiomyocyte number, fibrosis, immune cell infiltration, autonomic innervation and capillary density, (b) at the cardiomyocyte level to quantitate the extent of cell cycle progression and cellular hypertrophy as well as frequency of cardiomyocyte apoptosis, and (c) at the molecular level to quantitate transcriptome changes. The experiments proposed in Aim 2 will determine the degree to which cardiomyocyte cell cycle activity impacts atrial function following myocardial infarction. Atrial functional analyses will be performed (a) at whole organism level to quantitate echocardiographic and hemodynamic parameters, (b) at the intact heart level to quantitate calcium and voltage transient parameters in the left atrium (via optical mapping) and of cell clusters within the intact heart (via two-photon laser scanning microscopy), and (c) at the isolated cell level to quantitate fractional shortening and calcium handling kinetics. Importantly, cross-referencing the cell and molecular data from Aim 1 with the imaging and functional data from Aim 2 should enable us to better determine which cell cycle-mediated changes have a relevant impact on cardiac function. Such information may suggest interventions aimed at reversing compromised left atrial function in infarcted hearts.