Hypoxia induces pulmonary fibroblast differentiation

描述(由申请人提供)： 成纤维细胞分化为肌成纤维细胞的能力(由α-SM-肌动蛋白和其他SM相关蛋白的表达定义)已经得到了很好的证明，并被认为在各种血管和纤维疾病的病理生理学中是必不可少的。然而，尽管微血管缺血和/或全肺缺氧分别被认为是体循环和肺循环中成纤维细胞激活的关键起始者，但对于缺氧在调节成纤维细胞分化中的作用知之甚少。因此，我们进行了一系列实验，以检验低氧直接诱导成纤维细胞分化为肌成纤维细胞的可能性。我们观察到在慢性低氧动物的外膜成纤维细胞中，SM相关蛋白的表达增加，特别是α-SM-肌动蛋白，但也有SM22α的表达。我们发现，中等程度的缺氧诱导肌动蛋白聚合和α-SM-肌动蛋白表达增加，主要是通过Galphai 启动依赖Rho激酶、PI3K和JNK的信号通路培养PA成纤维细胞。我们还发现，细胞外的三磷酸腺苷可以诱导成纤维细胞的这种分化程序，细胞外的三磷酸腺苷浓度因低氧而增加。初步结果还表明，缺氧引起的细胞表型变化可被抑制细胞外ATP信号的药物减弱。我们还发现，转化生长因子β诱导培养的肺动脉外膜成纤维细胞表达α-SM-肌动蛋白，但低氧诱导的α-SM-肌动蛋白表达是通过与转化生长因子β无关的途径发生的。因此，本研究的总体目标是确定低氧诱导成纤维细胞分化为肌成纤维细胞的分子机制和信号通路，并确定细胞外ATP和/或转化生长因子β是否是这一反应的重要调节器。此外，由于已知调节许多SM相关基因的机制因不同而不同 根据细胞类型和施加的刺激，我们将确定低氧诱导的血管外膜成纤维细胞中α-SM-肌动蛋白的表达是否需要不同于血管SMC使用的转录因子。

DESCRIPTION (provided by the applicant): The ability of fibroblasts to differentiate into myofibroblasts (defined by expression of alpha-SM-actin and other SM-related proteins) is well documented and thought to be essential in the pathophysiology of a variety of vascular and fibrotic diseases. Little, however, is known regarding the role of hypoxia in regulating fibroblast differentiation despite the fact that microvascular ischemia and/or global hypoxia are considered critical initiators of fibroblast activation in the systemic and pulmonary circulations, respectively. We therefore performed a series of experiments to examine the possibility that hypoxia directly induces differentiation of fibroblasts into myofibroblasts. We observed increases in the expression of SM-related proteins, especially alpha-SM-actin but also SM22alpha by adventitial fibroblasts in the pulmonary artery (PA) adventitia of chronically hypoxic animals. We found that moderate levels of hypoxia induced actin polymerization and increased expression of alpha-SM-actin, largely through Galphai initiated Rho kinase-, PI3K- and JNK-dependent signaling pathways cultured PA fibroblasts. We also found this differentiation program in fibroblasts could be induced by extracellular ATP whose concentration was increased by hypoxia. Preliminary results also demonstrated that hypoxia-induced changes in cell phenotype were attenuated by agents which inhibits extracellular ATP signaling. We also found that TGFbeta induces alpha-SM-actin expression in cultured PA adventitial fibroblasts, but that hypoxia induced alpha-SM-actin expression occurred through pathways which appear largely independent of TGFbeta. The overall goal of this proposal is thus to determine the molecular mechanisms and signaling pathways through which hypoxia induces the differentiation of fibroblasts into myofibroblasts and to determine if extracellular ATP and/or TGFbeta are important modulators of this response. In addition, since it is known that the mechanisms regulating many SM-related genes differ depending on cell type and the stimulus imposed, we will determine whether hypoxia-induced alpha-SM-actin expression in vascular adventitial fibroblast requires transcription factors that differ from those used by vascular SMC.