Investigating Matrix-Fibroblast Regulation of MicroRNAs. A Dice(r)y Proposition.
Investigating Matrix-Fibroblast Regulation of MicroRNAs. A Dice(r)y Proposition.
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研究 MicroRNA 的基质成纤维细胞调节。
DOI：
10.1164/rccm.201803-0532ed
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发表时间：
2018
影响因子：
24.7
通讯作者：
Horowitz,JeffreyC
中科院分区：
文献类型：
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作者：
Horowitz,JeffreyC
伤口修复是一种精心安排的反应，涉及一系列驻留细胞和募集细胞，这些细胞在以动态生化和生物力学变化为特征的微环境中受到多种可溶性介质的调节(1)。我们对细胞功能障碍导致异常修复和纤维化的机制的理解已经大大扩展(2)。最近，研究越来越关注基质本身如何主要通过调节肌成纤维细胞的行为来维持异常修复的循环（3-6）。然而，“基质”代表了一种复杂的结构，它可以被组织、交联和重塑成具有不同机械性能和生化成分的支架。基质生物学的不同方面如何调节成纤维细胞的功能仍然是一个积极研究的领域。细胞主要通过机械转导信号蛋白感知和响应基质，包括整合素、FAK（局灶黏附激酶）、ROCK （rho激酶）、心肌素相关转录因子- a以及希波蛋白激酶相关的Yap和Taz。这些蛋白中的每一种都可以通过暴露于坚硬（而不是柔顺）底物而激活，在体外促进促纤维化肌成纤维细胞表型，并在体内促进肺纤维化（1,5,7 - 9）。在本期杂志上发表的一项研究中，Herrera及其同事（第486-496页）试图确定脱细胞特发性肺纤维化细胞外基质（IPF-ECM）如何降低正常成纤维细胞中的基质基因抑制剂miR-29（10）。先前的研究表明，在IPFECM上，miR-29在成纤维细胞中受到抑制，miR-29的降低与肺纤维化有关，但尚未探讨其机制（4,6,11）。其他研究表明，在坚硬底物上的成纤维细胞中，Yap的激活也推动了促纤维化基因的表达，并促进了肺纤维化的发生(8)。因此，研究人员假设暴露于IPF-ECM的成纤维细胞中的Yap激活会抑制miR-29并促进基质基因表达的增加。在一系列严格的实验中，他们使用正常和IPF-ECM以及聚丙烯酰胺水凝胶在体外模拟正常或纤维化肺以及两种体内异种移植纤维化模型，他们发现Yap和上述列出的其他机械转导相关蛋白都不是IPF-ECM抑制miR-29的原因。相反，他们发现了一种新的机制，IPF-ECM通过改变microRNA （miRNA）加工机制来阻止miR-29的成熟。在确认miR-29抑制与IPF-ECM细胞中胶原合成增加相结合后，他们发现，在坚硬的水凝胶底物上的细胞中，miR-29增加（而不是预期的减少），而在IPF-ECM上的细胞中，Yap核定位减少（而不是增加）。他们还观察到IPF-ECM细胞中miR-29前体的增加，这表明miRNA加工缺陷可能导致成熟miR-29的减少。事实上，IPF-ECM降低了miRNA加工酶Dicer1、Ago2和Drosha。然而，它们不受聚丙烯酰胺水凝胶刚度差异的影响。在这三种酶中，Dicer1在IPF组织中富含成纤维细胞的成纤维灶核心内明显减少。一致地，Dicer1敲低与对照ECM成纤维细胞中miR-29的降低和ECM蛋白表达的增加有关。最后，将dicer1缺陷成纤维细胞导入斑马鱼胚胎或小鼠中，促进病变的发展，前胶原表达增加，提示纤维化。这些研究定义了…
Wound repair is an orchestrated response involving an array of resident and recruited cells that are regulated by multiple soluble mediators in a microenvironment characterized by dynamic biochemical and biomechanical changes (1). Our understanding of the mechanisms by which cellular dysfunction leads to aberrant repair and fibrosis has expanded dramatically (2). Recently, research has increasingly focused on how the matrix itself serves to perpetuate the cycle of aberrant repair, primarily through regulation of myofibroblast behavior (3–6). However,“the matrix” represents a complex structure that can be organized, cross-linked, and remodeled into scaffolds with varying mechanical properties and biochemical compositions. How different aspects of matrix biology regulate fibroblast function remains an area of active investigation. Cells sense and respond to the matrix largely through mechanotransduction signaling proteins, including integrins, FAK (focal adhesion kinase), ROCK (Rho-kinase), myocardin-related transcription factor-A, and the Hippo-kinase–associated Yap and Taz. Each of these proteins is activated by exposure to stiff (rather than compliant) substrates, promotes a profibrotic myofibroblast phenotype in vitro, and contributes to lung fibrosis in vivo (1, 5, 7–9). In a study presented in this issue of the Journal, Herrera and colleagues (pp. 486–496) sought to determine how decellularized idiopathic pulmonary fibrosis extracellular matrices (IPF-ECM) diminished the stromal gene inhibitor miR-29 in normal fibroblasts (10). Prior work showed miR-29 suppression in fibroblasts on IPFECM and linked decreased miR-29 to pulmonary fibrosis, but the mechanisms involved have not been explored (4, 6, 11). Other studies showed that Yap activation in fibroblasts on stiff substrates also drove profibrotic gene expression and contributed to lung fibrogenesis (8). Thus, the investigators postulated that that Yap activation in fibroblasts exposed to an IPF-ECM would suppress miR-29 and promote increased stromal gene expression. In a series of rigorous experiments using normal and IPF-ECM and polyacrylamide hydrogels to model normal or fibrotic lungs in vitro along with two in vivo xenograft models of fibrosis, they found that that neither Yap nor the other mechanotransduction-related proteins listed above were responsible for miR-29 suppression by the IPF-ECM. Instead, they identified a novel mechanism by which the IPF-ECM alters microRNA (miRNA) processing machinery to prevent maturation of miR-29.After confirming that miR-29 suppression was coupled with increased collagen synthesis in cells on IPF-ECM, they discovered that miR-29 was increased (not decreased, as expected) in cells on stiff hydrogel substrates, and that Yap nuclear localization was reduced (not increased) in cells on the IPF-ECM. They also observed increased miR-29 precursors in cells on the IPF-ECM, suggesting that defective miRNA processing might account for the decreased mature miR-29. Indeed, the miRNA processing enzymes Dicer1, Ago2, and Drosha were decreased by the IPF-ECM. However, they were not influenced by differences in the stiffness of polyacrylamide hydrogels. Among the three enzymes, Dicer1 was notably diminished within the myofibroblast-rich core of fibroblastic foci in IPF tissue. Consistently, Dicer1 knockdown was associated with decreased miR-29 and increased ECM protein expression in fibroblasts on control ECMs. Finally, the introduction of Dicer1-deficient fibroblasts into zebrafish embryos or into mice promoted the development of lesions with increased procollagen expression suggestive of fibrosis. These studies define a …