Myocardin in the pathogenesis of pleural remodeling

胸膜损伤通常导致胸膜表面的广泛重塑，在严重的情况下， 胸膜纤维化（PF）。PF可由细菌性肺炎、创伤、辐射暴露和 石棉相关的胸膜损伤严重时，PF可导致限制性肺病或纤维胸。PF与 肺限制在医学实践中经常见到，但目前的治疗不令人满意且有效 没有药物治疗。PF的特征是α-平滑肌肌动蛋白（α-SMA）的增殖 表达肌成纤维细胞。这些肌成纤维细胞通过增加胸膜增厚， 细胞外基质沉积肌成纤维细胞的扩增主要是由于间充质转化（MT） 称为MesoMT。我们的初步数据表明，TGF-β诱导 myocardin的表达和活性。此外，肌心蛋白及其效应蛋白，平滑肌肌球蛋白， 钙调蛋白和KIF 5A在我们的胸膜损伤小鼠模型中上调。相反，心肌素下降- 调节减弱TGF-β介导的MesoMT标记物α-SMA的诱导，胶原蛋白的分泌和 纤维连接蛋白和胸膜纤维化。我们还报道了KIF 5A在TGF-β诱导的PF中上调， 胶原蛋白的分泌。根据这些观察和强有力的初步数据，我们强烈推断， myocardin的表达和激活实质上有助于PF的进展。在这个项目中，我们将 验证中心假设，即心肌素及其效应蛋白的激活和上调是关键的 决定因素的收购激活PMC表型和PF的进展。我们的目标是 使用最先进的细胞、生物化学、分子、生理学和成像技术来检验这一假设。 原代人（H）和小鼠（M）PMC将用于定义调节MesoMT的机制。 将使用三种鼠模型来评估心肌蛋白和KIF 5信号传导在PF：碳中和中的作用。 布莱克/博莱霉素（CBB）诱导的PF、肺炎链球菌诱导的脓胸/PF和TGF-β诱导的PF。 我们的具体目标是：1）确定心肌素诱导的HPMCs MesoMT的机制，2）确定 MesoMT中KIF 5活化和HPMC的ECM沉积的机制，以及3）确定 myocardin和相关效应蛋白在PF的体内进展中对新基质沉积的影响。我们将使用 新的纤维化胸膜损伤小鼠模型，包括使用间皮素标记的小鼠，以实现命运绘图 分析，分子，生物化学和免疫组织化学技术，我们有专业知识， 最先进的CT成像和肺功能分析，以实现这些目标。该机制通过 TGF-β和myocardin对MesoMT和PF的调控机制目前尚不清楚， 我们对胸膜机化的发病机制的理解和我们识别新的治疗方法的能力存在差距， 目标的该提案解决了这些差距中的每一个，并且可以预见的是，将确定可以实现的新目标。 旨在改善PF/纤维胸患者的结局。

Pleural injury often leads to extensive remodeling of the pleural surfaces, which in severe cases leads to pleural fibrosis (PF). PF can occur as a result of bacterial pneumonia, trauma, radiation exposure and asbestos-related pleural injury. When severe, PF can cause restrictive lung disease or fibrothorax. PF with lung restriction is often seen in medical practice but current treatment is unsatisfactory and effective pharmacotherapy is not available. PF is characterized by proliferation of alpha-smooth muscle actin (α-SMA) expressing myofibroblasts. These myofibroblasts contribute to the thickening of the pleura via increased extracellular matrix deposition. The expansion of myofibroblasts is largely due to mesenchymal transition (MT) of resident pleural mesothelial cells, termed MesoMT. Our preliminary data show that TGF-β induces myocardin expression and activity. Further, myocardin and its effector proteins, smooth muscle myosin, calponin, and KIF5A are upregulated in our mouse models of pleural injury. Conversely, myocardin down- regulation attenuates TGF-β mediated induction of MesoMT marker, α-SMA, secretion of collagen and fibronectin and pleural fibrosis. We also reported that KIF5A is upregulated in TGF-β induced PF and critical for collagen secretion. Based on these observations and strong preliminary data, we strongly infer that myocardin expression and activation substantively contribute to the progression of PF. In this project, we will test the central hypothesis that the activation and upregulation of myocardin and its effector proteins are critical determinants in the acquisition of the activated PMC phenotypes and the progression of PF. Our objective is to test this postulate using state of the art cellular, biochemical, molecular, physiologic and imaging techniques. Primary human (H) and mouse (M) PMCs will be used to define mechanisms by which MesoMT is regulated. Three murine models will be used to assess the role of myocardin and KIF5 signaling in PF: carbon black/bleomycin (CBB) induced PF, Streptococcus pneumoniae-induced empyema/PF and TGF-β induced PF. Our specific aims are: 1) To define the mechanism of myocardin-induced MesoMT of HPMCs, 2) to define the mechanism of KIF5 activation in MesoMT and ECM deposition by HPMCs and 3) to define the contribution of myocardin and related effector proteins to neo-matrix deposition in the progression of PF in vivo. We will use new murine models of fibrosing pleural injury, including mice with mesothelial labelling to enable fate-mapping analyses, molecular, biochemical and immunohistochemical techniques with which we have expertise and state of the art CT imaging and pulmonary function analyses to accomplish these aims. The mechanism(s) by which TGF-β and myocardin regulate MesoMT and PF are currently unclear, representing potentially important gaps in our understanding of the pathogenesis of pleural organization and our ability to identify new therapeutic targets. This proposal addresses each of these gaps and predictably will identify novel targets that could be developed to improve outcomes of patients with PF/fibrothorax.