Extracellular matrix regulation of cellular crosstalk in cardiac fibrosis

摘要： 心脏纤维化会损害心脏功能，增加发生心律失常的风险。转型 生长因子β(β)家族是包括心脏纤维化在内的纤维化的主要驱动力。潜在的转化生长因子β结合 蛋白(LTBP)是限制潜在转化生长因子β释放和活性的细胞外基质蛋白。我们之前 我们发现LTbP4是肌营养不良症的一种遗传修饰物，我们证明了LTbP4与S的结合能力 转化生长因子β与肌膜稳定性和纤维化密切相关。LTBP4沿着外表面被发现 肌纤维中的肌膜和LTBP4类似地存在于心肌细胞的外表面。 条纹图案。因为LTBP4在心脏中高度表达，所以LTBP4处于很好的位置来调节潜伏期 转化生长因子β在心肌纤维化中的释放。小鼠和人类的LTBP4基因具有天然的保护性 和有害形式，产生与不同的转化生长因子β活性和下游转化生长因子β相关的蛋白 发信号。携带保护性Ltbp4等位基因的小鼠株有12个氨基酸插入到ltbp4‘S铰链上 区域，使蛋白质更能抵抗蛋白降解和潜在的转化生长因子β释放。相应地，鼠标 携带有害等位基因Ltbp4的菌株缺乏12个氨基酸，产生一种LTBP4蛋白，这种蛋白质是 更容易发生蛋白分解，导致潜在的转化生长因子β过度释放、信号传导和纤维化。在慢性病 进行性心肌病，有基质重塑的失调，可进一步增强 适应不良的基质移位和不利改变心脏功能，增加心律失常的风险。我们现在要研究 通过三种途径探讨转化生长因子β的S与LTbP4在心脏中的相互作用。在目标1中，我们将使用 去细胞基质，称为dECM，从小鼠心脏中定义必要的成分和活性 心肌细胞和心肌成纤维细胞之间的细胞通讯。在目标2中，我们将评估人类 诱导多能干细胞来源的心肌细胞，我们还将进行体内阻断评估 转化生长因子β在小鼠体内释放促进心肌细胞膜稳定和减少 心脏纤维化。在目标3中，我们将评估LTBP4在人类工程心脏中介导的细胞串扰 组织(EHTS)。通过这项工作，我们将扩大对LTBP监管的机械性理解 转化生长因子β，目标是对基质进行治疗性修改。

Abstract: Cardiac fibrosis impairs heart function and increases risk for cardiac arrhythmias. The transforming growth factor beta (TGFβ) family is major driver of fibrosis, including cardiac fibrosis. Latent TGFβ binding proteins (LTBPs) are extracellular matrix proteins that restrict latent TGFβ release and activity. We previously identified LTBP4 as a genetic modifier of muscular dystrophy, where we showed that LTBP4’s ability to bind TGFβ was strongly linked to sarcolemmal stability and fibrosis. LTBP4 is found along the exterior surface of the sarcolemma in myofibers, and LTBP4 is similarly found on the exterior surface of cardiomyocytes in a striated pattern. Because LTBP4 is highly expressed in the heart, LTBP4 is well positioned to regulate latent TGFβ release in cardiac fibrosis. The LTBP4 genes in mice and humans have naturally occurring protective and deleterious forms which produce proteins associated with differential TGFβ activity and downstream TGFβ signaling. Mouse strains bearing the protective Ltbp4 allele have 12 amino acids inserted into LTBP4’s hinge region, rendering the protein more resistant to proteolysis and latent TGFβ release. Correspondingly, mouse strains harboring the deleterious allele of Ltbp4, lacking 12 amino acids, produce an LTBP4 protein that is more susceptible to proteolysis leading to excess latent TGFβ release, signaling and fibrosis. In chronic progressive cardiomyopathies, there is dysregulation of matrix remodeling, which can further enhance maladaptive matrix shifts and adversely alter heart function and promote arrhythmia risk. We will now study LTBP4 in the heart by probing TGFβ’s interaction with LTBP4 using three approaches. In Aim 1, we will use decellularized matrices, called dECMs, from mouse hearts to define components and activity necessary for cellular communication between cardiomyocytes and cardiac fibroblasts. In Aim 2, we will evaluate human induced pluripotent stem cell-derived cardiomyocytes, and we will also conduct in vivo assessment of blocking TGFβ release in mice using an anti-LTBP4 antibody to promote cardiac sarcolemmal stability and reduce cardiac fibrosis. In Aim 3, we will evaluate cellular crosstalk mediated by LTBP4 in human engineered heart tissues (EHTs). Through this work, we will expand the mechanistic understanding of LTBP’s regulation of TGFβ with the goal of therapeutically modifying the matrix.