Extracellular matrix regulation of cellular crosstalk in cardiac fibrosis

摘要： 心脏纤维化损害心脏功能并增加心律失常的风险。转化 生长因子β（TGFβ）家族是纤维化（包括心脏纤维化）的主要驱动因素。潜在TGFβ结合 蛋白质（LTBP）是限制潜在TGFβ释放和活性的细胞外基质蛋白。我们之前 将LTBP4鉴定为肌营养不良症的遗传修饰物，我们发现LTBP4的结合能力 TGFβ与肌膜稳定性和纤维化密切相关。LTBP 4沿着外表面发现， LTBP4类似地发现于心肌细胞的外表面， 条纹状由于LTBP4在心脏中高度表达，因此LTBP4很好地定位于调节潜伏性心肌梗死。 心脏纤维化中的TGFβ释放。小鼠和人类中的LTBP 4基因具有天然的保护作用， 和产生与不同TGFβ活性和下游TGFβ相关的蛋白质的有害形式 发信号。携带保护性Ltbp4等位基因的小鼠品系在LTBP 4的铰链中插入了12个氨基酸 区域，使蛋白质对蛋白水解和潜在的TGFβ释放更具抗性。相应地，老鼠 携带Ltbp4的有害等位基因（缺少12个氨基酸）的菌株产生LTBP 4蛋白， 更容易发生蛋白水解，导致过度的潜在TGFβ释放、信号传导和纤维化。慢性 在进行性心肌病中，存在基质重塑的失调，这可以进一步增强 适应不良的基质移位并不利地改变心脏功能并增加心律失常的风险。我们现在要学习 通过使用三种方法探测TGFβ与LTBP4的相互作用来研究心脏中的LTBP4。在目标1中，我们将使用 去细胞基质，称为dECM，从小鼠心脏，以定义必要的组件和活动， 心肌细胞和心脏成纤维细胞之间的细胞通讯。在目标2中，我们将评估人类 诱导多能干细胞衍生的心肌细胞，我们还将进行体内评估阻断 使用抗LTBP4抗体促进小鼠心脏肌膜稳定性并减少TGFβ释放 心脏纤维化在目标3中，我们将评估LTBP 4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LTBP的调节机制的理解， TGFβ，目的是治疗性地修饰基质。

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.