Length-dependent activation in human myocardium

摘要 这个转化项目使用从器官捐赠者和接受手术的患者中获得的人类生物标本。 心脏移植，以促进对支撑弗兰克-八哥的细胞水平机制的理解 关系具体来说，该项目的重点是长度依赖性激活，定义为增加的最大值 力和Ca 2+敏感性的心肌牵张引起的收缩。长度背后的机制- 依赖性激活尚不清楚，但可能涉及粗丝调节和新的神经元之间的转换。 发现了肌球蛋白的OFF和ON状态。 共同研究员坎贝尔花了十年时间建立了一个生物样本库，现在包含了超过10，000个心肌标本， >360例患者。Co-PI坦纳用这些样品进行的初步实验表明， 非缺血性心力衰竭患者心肌中Ca 2+敏感性的变化被消除，但 保存在器官捐赠者和缺血性心力衰竭患者的心肌中。新电脑 模型预测，这些功能效应反映了肌球蛋白OFF状态的不稳定， 患有非缺血性心力衰竭这一假设得到了其他实验的支持， 极化技术来评估人类心肌的粗丝中的OFF/ON动态。其他试点 研究测试了靶向粗丝的肽的作用。稳定OFF状态的肽减少 长肌节收缩Ca ~（2+）敏感性，去稳定肽增强Ca ~（2+）敏感性 在短的长度。这些效应的长度依赖性是通过我们的计算机建模预测的。 该项目建立在这些来自人类生物标本的数据基础上，并整合了五个国家的技能和资源。 心血管研究人员，统计学家和专门研究晚期心力衰竭的医生科学家。 本研究的目的是探索一个总体假设，即在非糖尿病患者中， 缺血性心力衰竭，因为他们的心脏粗丝偏向ON状态。 目的1：检验以下假设，即心肌中Ca 2+敏感性的长度依赖性变化从 非缺血性心力衰竭患者。 目的2：检验患者心肌中粗细丝的OFF状态不稳定的假设 非缺血性心力衰竭患者 目的3：靶向OFF/ON转换以操纵人心肌的Ca 2+敏感性。

ABSTRACT This translational project uses human biospecimens procured from organ donors and patients undergoing cardiac transplant to advance understanding of a cellular-level mechanism that underpins the Frank-Starling relationship. Specifically, the project focuses on length-dependent activation, defined as the increased maximum force and Ca2+ sensitivity of contraction induced by myocardial stretch. The mechanisms that underlie length- dependent activation remain unclear, but may involve thick-filament regulation and transitions between the newly discovered OFF and ON states of myosin. Co-PI Campbell has spent a decade building a biobank that now contains >10,000 myocardial specimens from >360 patients. Pilot experiments performed by Co-PI Tanner with these samples show that length-dependent changes in Ca2+ sensitivity are eliminated in myocardium from patients who have non-ischemic heart failure, but preserved in myocardium from organ donors and patients who have ischemic heart failure. New computer modeling predicts that these functional effects reflect destabilization of the myosin OFF state in patients who have non-ischemic heart failure. This hypothesis is supported by additional experiments that used fluorescent polarization techniques to assess OFF/ON dynamics in the thick filaments of human myocardium. Further pilot studies tested the effects of peptides targeted to the thick filament. Peptides that stabilize the OFF state reduced the Ca2+ sensitivity of contraction at long sarcomere length while destabilizing peptides enhanced Ca2+ sensitivity at short length. The length-dependence of these effects was predicted by our computer modeling. The project builds on these data from human biospecimens and integrates the skills and resources of five cardiovascular researchers, a statistician, and a physician-scientist who specializes in advanced heart failure. The Aims explore the global hypothesis that length-dependent activation is reduced in patients who have non- ischemic heart failure because their cardiac thick filaments are biased towards the ON state. Aim 1: Test the hypothesis that length-dependent changes in Ca2+ sensitivity are reduced in myocardium from patients who have non-ischemic heart failure. Aim 2: Test the hypothesis that the OFF state of the thick filament is destabilized in myocardium from patients who have non-ischemic heart failure. Aim 3: Target OFF/ON transitions to manipulate the Ca2+ sensitivity of human myocardium.