HL-Role of c-Myc in myofibroblast differentiation in pulmonary fibrosis

 描述(申请人提供)：HL-131：特发性肺纤维化(IPF)是一种持续发展，最终致命的疾病，发病机制知之甚少，无法治愈。IPF患者通常在确诊后存活2至4年。IPF与活化的间充质细胞，特别是肌成纤维细胞对肺实质的逐渐侵袭有关，这些细胞间充质细胞形成“成纤维细胞灶”，并通过沉积过多的细胞外基质导致肺泡结构丧失而导致瘢痕形成。这项建议的目的是鉴定产生肌成纤维细胞的间充质细胞类型及其分化机制。我们的初步研究表明，在博莱霉素损伤后，脂肪成纤维细胞是大多数肌成纤维细胞的来源。此外，我们的数据表明，在TE分解阶段，肌成纤维细胞的一部分恢复为脂成纤维细胞系。我们的初步数据还表明，博莱霉素损伤后，肺间充质中关键的Wnt靶基因c-Myc在肺成纤维细胞中强烈表达。有趣的是，我们的初步数据还表明，c-Myc的过度表达本身(在没有肺损伤的情况下)足以驱动肌成纤维细胞在整个肺实质中分化和积聚。与周围或野生型间充质相比，这些肌成纤维细胞高度增殖，表达高水平的c-Myc、α-SMA和胶原。我们推测c-Myc在肺纤维化中诱导脂成纤维细胞转分化为肌成纤维细胞并随后增殖。我们还假设，肌成纤维细胞中c-Myc的失活将通过促进肌成纤维细胞向非增殖性脂肪成纤维细胞的去分化来促进纤维化肺疾病的解决。这些假设将以三个具体目标加以阐述。在特定的目标1中，我们将检验博莱霉素介导的肺损伤后脂成纤维细胞转分化为肌成纤维细胞，以及在小鼠纤维化消退过程中肌成纤维细胞去分化为脂成纤维细胞的假说。在特定的目标2中，我们将检验c-Myc足以将脂肪成纤维细胞转化为高增殖的肌成纤维细胞并维持其分化状态的假设。最后，在特定目标3中，我们将检验脂成纤维细胞中c-Myc对于 博莱霉素性肺损伤后肌成纤维细胞的发育、增殖和维持。从治疗的角度来看，对肌成纤维细胞分化状态的控制几乎是完全未知的。这项拟议的研究将显著提高我们对肺纤维化的认识：(I)通过鉴定在肺纤维化中产生肌成纤维细胞的细胞的起源；(Ii)通过验证操纵脂纤维细胞向肌成纤维细胞转分化的概念以及反向过程作为一种有趣的新的治疗方案用于治疗纤维增殖性肺疾病；(Iii)通过确定-Myc是LIF向MYF转分化及其随后的增殖的主要驱动因素，并验证c-Myc作为治疗肺纤维化的潜在治疗靶点。

 DESCRIPTION (provided by applicant): HL-131: Idiopathic pulmonary fibrosis (IPF) is a relentlessly progressive, and ultimately fatal disorder with a poorly understood pathogenesis and no cure. Patients with IPF typically survive 2 to 4 years after diagnosis. IPF is associated with the progressive invasion of the lung parenchyma by activated mesenchymal cells, in particular myofibroblasts, which form `fibroblastic foci' and cause scarring by depositing excessive extracellular matrix resulting in a loss of alveolar architecture. The goal of this proposal is to identify the mesenchymal cell type that gives rise to myofibroblasts and its mechanism of differentiation. Our preliminary studies show that lipofibroblasts are the source for the majority of myofibroblasts after bleomycin injury. In addition, our data indicate that during te resolution phase a subset of myofibroblasts revert back to the lipofibroblast lineage. Our preliminary data also demonstrate that c-Myc, a key Wnt target gene in lung mesenchyme, is strongly expressed in myofibroblasts in lungs after bleomycin injury. Interestingly, our preliminary data also indicate that overexpression of c-Myc by itself (in the absence of lung injury) is sufficient to drive the differentiation and accumulation of myofibroblasts throughout th lung parenchyma. These myofibroblasts are highly proliferative and express high levels of c-Myc, α-Sma and collagen compared to surrounding or wild type mesenchyme. We hypothesize that c-Myc induces lipofibroblast to myofibroblast transdifferentiation and their subsequent proliferation in pulmonary fibrosis. We also hypothesize that c-Myc inactivation in myofibroblasts will promote the resolution of fibrotic lung disease by promoting dedifferentiation of myofibroblasts into non proliferative lipofibroblasts. These hypotheses will be addressed with three specific aims. In specific aim 1 we will test the hypothesis that lipofibroblasts transdifferentiate into myofibroblasts after bleomycin-mediated lung injury and that myofibroblasts dedifferentiate into lipofibroblasts during the resolution of fibrosis in mice. In specific aim 2 we will test the hypothesis that c-Myc is sufficient to transdifferentiate lipofibroblasts into highly proliferative myofibroblasts and to maintain their differentiation stats. Lastly in specific aim 3 we will test the hypothesis that c-Myc in lipofibroblasts is necessary for the development, proliferation and maintenance of myofibroblasts after bleomycin-mediated lung injury. From a therapeutic point of view, the control of the differentiation status of the myofibroblasts is almost completely unexplored. The proposed studies should significantly advance our knowledge of pulmonary fibrosis: (i) by identifying the origin of the cells that give rise to myofibroblasts in pulmonary fibrosis; (ii) by validating the concept of manipulating lipofibroblast to myofibroblast transdifferentiation as well as the reverse process as an intriguin new therapeutic option for the treatment of fibroproliferative lung diseases; (iii) by identifying -Myc as the main driver of LIF to MYF transdifferentiation and their subsequent proliferation, and as such validating c-Myc as a potential therapeutic target to treat pulmonary fibrosis.