Mechanisms of myofibroblast survival in fibrosis

特发性肺纤维化/通常间质性肺炎（IPF/UIP）是一种致命的肺实质疾病，以间质和肺泡纤维增生和肌成纤维细胞的出现为特征。关于IPF/UIP中肌成纤维细胞积累的机制，以及为什么它们在正常伤口修复过程中不能被清除，我们知之甚少。本实验室和其他实验室先前的研究表明，IPF/UIP中巨噬细胞和肺泡上皮细胞大量表达生存因子，特别是IGF-I。在本提案中，我们将验证IPF/UIP患者的薄壁组织和空气中存在生存因子（包括IGF-I）保护肌成纤维细胞免于凋亡的假设。在这种情况下，肌成纤维细胞会大量积累，从而导致实质纤维化持续较长时间。本研究的主要目的有三个：(1)研究生长因子和牵张退出条件下肌成纤维细胞凋亡的介导条件和机制；（ii）确定IGF-I如何保护肌成纤维细胞免于凋亡；（iii）探讨IPF/UIP中肌成纤维细胞凋亡失调的机制。这些目标将通过四个具体目标来实现。具体目标一将讨论生长因子，物理力和IGF-I在肌成纤维细胞分化，成纤维细胞表型逆转和细胞凋亡中的作用。这些研究将为确定促进肌成纤维细胞凋亡的机制奠定基础，重点关注caspase激活的机制（具体目的二）。具体目标三的目的是揭示通过IGF-I阻止启动死亡程序的机制。这些研究的重点将包括效应辣椒酶的失活机制（3,6和7）和抗凋亡蛋白的潜在作用。最后，在具体目标四中，我们建议应用从本提案中进行的研究中学到的知识来解决促进IPF/UIP患者肺部细胞凋亡保护的机制。这项工作的发现有望为肌成纤维细胞凋亡的机制以及这一过程如何在IPF/UIP中变得失调提供新的见解。

Idiopathic pulmonary fibrosis/usual interstitial pneumonitis (IPF/UIP) is a fatal parenchymal lung disease characterized by interstitial and alveolar fibroproliferation and the appearance of myofibroblasts. Little is known about the mechanisms of myofibroblast accumulation in IPF/UIP or why they fail to be eliminated as occurs during normal wound repair. Previous studies from this and other laboratories have shown that survival factors, especially IGF-I, are abundantly expressed by macrophages and alveolar epithelial cells in IPF/UIP. In this proposal, we will test the hypothesis that the presence of survival factors, including IGF-I, in the parenchyma and airspaces of patients with IPF/UIP protect myofibroblasts from apoptosis. Under these conditions, myofibroblasts are proposed to accumulate in numbers and can thus contribute to parenchymal fibrosis for extended periods of time. The major goals of this proposal are three-fold: (1) to investigate the conditions and mechanisms that mediate myofibroblast apoptosis under conditions of growth factor and stretch withdrawal; (ii) to determine how IGF-I serves to protect myofibroblasts from undergoing apoptosis; and (iii) to investigate the mechanism of dysregulation of myofibroblast apoptosis in IPF/UIP. These goals will be addressed by four specific aims. Specific aim one will address the role of growth factors, physical forces and IGF-I in myofibroblast differentiation, reversion to a fibroblast phenotype and apoptosis. These studies will form a basis for determining the mechanisms that promote myofibroblast apoptosis with a focus on the mechanisms of caspase activation (specific aim two). The objective of specific aim three is to uncover the mechanisms through which IGF-I prevents the initiation of the death program. The focus of these studies will include the mechanism of inactivation of the effector capsases (3, 6 and 7) and the potential role of anti-apoptotic proteins. Lastly, in specific aim four, we propose to apply what has been learned from this studies conducted in this proposal to address the mechanisms that promote protection from apoptosis in the lungs of patients with IPF/UIP. The findings from this work are expected to provide new insights into the mechanism of myofibroblast apoptosis and how this process becomes dysregulated in IPF/UIP.