Macrophage Expression of SPARC Contributes to Pressure-Overload Dependent Change in Collagen Content and Myocardial Stiffness

心肌重塑和舒张期功能异常是影响两者的关键事件。 我国退伍军人慢性心脏病患者的功能能力和致死事件发生率 故障(CHF)。CHF在退伍军人管理局系统中有一个指定的质量增强研究倡议(QUERI)，以 解决如何改善患有CHF的退伍军人的心血管保健。慢性压力- 由全身性高血压产生的过载(PO)是心肌梗死最常见的原因 肥厚和舒张期功能障碍，以及心力衰竭发展的最重要风险因素， 尤其是射血分数保留的心力衰竭(HFpEF)。我们最近对退伍军人的临床研究 研究表明，从代偿性高血压性心脏病(HHD)到失代偿性HFpEF的转变是 与舒张期特性的显著变化有关，包括被动舒张期僵硬的增加。 我们对退伍军人的翻译研究表明，这种僵硬增加的一个关键决定因素是 间质胶原增多。我们在PO诱导的小鼠纤维化模型上的研究表明， 控制胶原蛋白积累变化的机制是依赖于时间的 富含半胱氨酸的酸性分泌蛋白SPARC及其合成后调控 胶原蛋白加工。本申请中提出的初步研究支持心肌梗死的假说 巨噬细胞在影响基质细胞随时间增加的过程中起着重要作用 增加合成胶原蛋白加工后的蛋白质、胶原蛋白含量和心肌硬度 在PO中，并有助于心力衰竭的发展。这一假设将通过3个具体的 目标。在目标1中，将使用临床相关的PO诱导的纤维化小鼠模型来1)确定 心肌巨噬细胞的增加是否在驱动合成后胶原蛋白加工中起因果作用 这会导致心肌纤维化和舒张期功能障碍，以及2)是否存在时间依赖性的增加 在施加PO后的心肌巨噬细胞中。Aim 2中的实验将确定细胞特异性 抑制单核/巨噬细胞SPARC表达与靶向抑制成纤维细胞SPARC 减少和/或逆转PO诱导的心肌纤维化和舒张期功能障碍。在目标3中，研究 确定巨噬细胞依赖的机制是否导致舒张期功能障碍和心肌纤维化 在体内定义的AIMS 1和2在PO心脏成纤维细胞和分离的成纤维细胞中起因果作用 来自患有和不患有HHD诱导的纤维化的退伍军人。这些具体目标的完成将导致 更好地了解促进舒张期高血压形成的分子和细胞机制 PO功能障碍，导致向HFpEF过渡。机制因素的解释 HFpEF对于改进诊断方法和开发更好的治疗方法至关重要 患有慢性心力衰竭的退伍军人，这是一个重要的未得到满足的需求。

The development of myocardial remodeling and abnormal diastolic function are critical events that impact both functional capacity and the rates of morbid and mortal events in our Veteran population with chronic heart failure (CHF). CHF has a designated Quality Enhancement Research Initiative (QUERI) in the VA system to address ways to improve cardiovascular healthcare for Veteran’s suffering from CHF. Chronic pressure- overload (PO), produced by systemic hypertension, represents the most frequent cause of myocardial hypertrophy and diastolic dysfunction, and the most important risk factor for the development of heart failure, particularly heart failure with a preserved ejection fraction (HFpEF). Our recent clinical studies in Veterans showed that the transition from compensated hypertensive heart disease (HHD) to decompensated HFpEF is associated with significant changes in diastolic properties including an increase in passive diastolic stiffness. Our translational studies in Veterans showed that one pivotal determinant of this increase in stiffness is an increase in interstitial collagen. Our studies in murine models of PO-induced fibrosis showed that one mechanism that controls changes in collagen accumulation is the time dependent production of the matricellular protein SPARC (secreted protein acidic and rich in cysteine) and its regulation of post-synthetic collagen processing. Preliminary studies presented in this application support the hypothesis that myocardial macrophages serve a fundamental role in affecting the time-dependent increase in matricellular proteins that increases post synthetic collagen processing, collagen content, and myocardial stiffness in PO and contributes to the development of heart failure. This hypothesis will be tested with 3 Specific Aims. In Aim 1, the use of clinically relevant murine models of PO-induced fibrosis will be used to 1) determine whether increases in myocardial macrophages plays a causal role in driving post-synthetic collagen processing that results in myocardial fibrosis and diastolic dysfunction and 2) whether there is a time-dependent increase in myocardial macrophages after imposition of PO. Experiments in Aim 2 will determine whether cell-specific inhibition of SPARC expression in monocyte/macrophages versus targeted inhibition of SPARC in fibroblasts reduces and/or reverses PO-induced myocardial fibrosis and diastolic dysfunction. In Aim 3, studies to determine whether macrophage-dependent mechanisms driving diastolic dysfunction and myocardial fibrosis defined in vivo in Aims 1&2 play a causal role in fibroblasts isolated from PO hearts and in fibroblasts isolated from Veterans with and without HHD-induced fibrosis. The completion of these Specific Aims will lead to a better understanding of the molecular and cellular mechanisms that contribute to the development of diastolic dysfunction in PO and that lead to the transition to HFpEF. Elucidation of mechanistic factors that contribute to HFpEF are critical for improved methods of diagnosis and the development of better therapies to treat our Veterans with CHF, a significant unmet need.