Myocardial Stiffness in Diastolic Heart Failure

描述（由申请人提供）：舒张性心力衰竭是疾病和死亡的主要原因。这种情况几乎总是与心室僵硬增加有关，在老年人和/或肥胖人群中更为常见。目前尚无有效的临床治疗方法。本研究的核心假设是舒张期心肌刚度是“主动”刚度成分（由于肌球蛋白头在舒张期继续循环）和“被动”刚度成分（归因于titin、胶原蛋白、弹性蛋白和中间纤维）的总和。提出的研究确定了这些成分在从单个肌细胞到整个心脏的制备中的相对贡献，并使用这些结果创建舒张刚度的预测计算模型。特异性目的1将确定负责老年大鼠心肌硬度增加的分子成分。目前的假设是，僵硬度的增加反映了肌球蛋白动动力学的减慢。实验将测量6、18、22和26月龄Fischer 344大鼠心肌的力学性能，方法是在不同水平的钙活化下，对化学渗透的单个肌细胞和多细胞制剂进行反复拉伸。另外的实验将通过在langendorff灌注心脏的左心室内放置快速充气的气球来测量不同年龄动物的心室僵硬度。凝胶电泳法测定肌球蛋白和肌球蛋白异构体的含量。胶原蛋白和弹性蛋白含量和胶原交联将使用组织学和生化技术来确定。特异性目标2将使用相同的方法来确定在饮食诱导的肥胖大鼠模型中明显增加心肌硬度的分子成分。这一目的的工作假设是，在肥胖的Sprague-Dawley大鼠中观察到的心肌硬度升高反映了胶原蛋白含量增加和/或胶原交联。具体的Aim 3使用Aims 1和Aims 2的实验结果来创建舒张刚度的预测计算模型。模型框架将由弹性和粘弹性元素（代表titin、胶原蛋白、弹性蛋白和中间纤维）组成，并与肌动蛋白相互作用的空间明确模拟平行排列。通过多维优化确定模型参数。最终的模型将被用来测试对心肌僵硬度的交叉桥分量的预测，并将被证明对评估舒张性心力衰竭潜在新疗法的可能效果有用。这项研究与公共卫生相关，因为它试图确定心脏在一种称为舒张性心力衰竭的常见心血管疾病中变得过度僵硬的原因。实验结果应该有助于科学家开发出更好的治疗超重和老年患者的方法。

DESCRIPTION (provided by applicant): Diastolic heart failure is a major cause of illness and death. The condition is nearly always associated with increased ventricular stiffness and is more common in elderly and/or obese populations. There are no effective clinical treatments. The central hypothesis underlying this research is that diastolic myocardial stiffness is the sum of an 'active' stiffness component (due to myosin heads that continue to cycle during diastole) and a 'passive' stiffness component (attributed to titin, collagen, elastin and intermediate filaments). The proposed research determines the relative contributions from these components in preparations ranging from single myocytes to whole hearts and uses these results to create a predictive computational model of diastolic stiffness. Specific Aim 1 will identify the molecular components responsible for the increased stiffness of myocardium from aged rats. The working hypothesis is that the increased stiffness reflects slowed acto-myosin kinetics. Experiments will measure the mechanical properties of myocardium from 6, 18, 22 and 26-month-old Fischer 344 rats by subjecting chemically permeabilized single myocytes and multicellular preparations to repeated stretches at different levels of calcium activation. Additional experiments will measure ventricular stiffness in the different aged animals by rapidly inflating balloons placed inside the left ventricles of Langendorff-perfused hearts. Titin and myosin isoform content will be measured by gel electrophoresis. Collagen and elastin content and collagen cross-linking will be determined using histological and biochemical techniques. Specific Aim 2 will use identical methods to identify the molecular components responsible for the increased myocardial stiffness evident in a rat model of diet-induced obesity. The working hypothesis for this aim is that the elevated myocardial stiffness observed in obese Sprague-Dawley rats reflects increased collagen content and/or collagen cross-linking. Specific Aim 3 uses the experimental results from Aims 1 and 2 to create a predictive computational model of diastolic stiffness. The model framework will consist of elastic and visco-elastic elements (representing titin, collagen, elastin and intermediate filaments) arranged in parallel with a spatially-explicit simulation of acto-myosin interactions. Model parameters will be determined by multi-dimensional optimization. The final model will be used to test predictions about the cross-bridge component of myocardial stiffness and should prove useful for assessing the likely effects of potential new treatments for diastolic heart failure. NARRATIVE This research is relevant to public health because it seeks to identify why hearts become excessively stiff in a common cardiovascular disease called Diastolic Heart Failure. The experimental results should help scientists to develop better treatments for the disease in overweight and elderly patients.