Elucidating fibroblast heterogeneity as a pathway to target organ fibrosis

项目总结 在手术或创伤后，器官和组织可以通过再生来愈合，但通常比 不，修复过程因纤维化而变得复杂，导致功能下降，最终导致器官衰竭。 活化的成纤维细胞(FBS)是修复和纤维化的中心介质，因此很难靶向 纤维化而不影响修复。现在人们普遍认为，FBS代表着一种不同种类的 然而，我们对这种异质性的分子、细胞和功能基础了解很少。 我们的初步数据已经在小鼠的心脏、皮肤和皮肤中发现了两个主要和不同的激活Fb群体 损伤后肾脏：成纤维细胞特异性蛋白1表达的FBS和α-平滑肌肌动蛋白 (αSMA)-表达FBS，出现在损伤后的不同时间点，并保持离散 在康复过程中的人口。在FSP1或α-SMA启动子作用下表达绿色荧光蛋白的小鼠 分离心脏损伤后活化的FB群体并比较每个群体的基因表达谱 从未受伤的心脏中分离出的FBS。RNA测序显示不同的分子 签名。特别是，促纤维化基因，如I型胶原(COL I)和转化生长因子β信号通路 在αSMA-FBS中上调，而参与细胞内稳态、组织重塑和细胞-细胞的基因 FSP1-FBS的通讯功能上调。几项研究，包括我们小组的研究表明， 分泌型Frizzled相关蛋白2(SFRP2)是一种可能的WNT途径抑制物，通过以下途径介导伤口修复 抑制纤维化。我们开发了一种新的小鼠模型，在该模型中，我们可以诱导SFRP2在 损伤后激活FBS。我们发现，损伤后早期激活SFRP2导致纤维化减轻 心肌、肾脏和皮肤损伤后不抑制组织修复。有趣的是，我们的初步数据 结果表明，SFRP2只抑制转化生长因子β信号转导，而不抑制αSMA-FBS的I型胶原合成和Wnt信号转导 FSP-1胎牛血清在体外不表达。因此，SFRP2代表了一种抗纤维化旁分泌因子，它可能会减少组织 通过对损伤后(即激活的)FB亚型施加不同的分子效应而导致纤维化。在结束时 在这项研究建议中，我们将表征主要的细胞和功能的异质性 损伤激活的FB种群，也阐明了修复前， SFRP2通过对表达α-SMA的FBS的靶向性作用而发挥抗纤维化作用。

PROJECT SUMMARY Following surgical or traumatic injury, organs and tissues can heal by regeneration but more often than not, the repair process is complicated by fibrosis, resulting in reduced function and eventually organ failure. Activated fibroblasts (FBs) are the central mediators of both repair and fibrosis making it difficult to target fibrosis without affecting repair. It is now well accepted that FBs represent a heterogeneous population of cells, yet we have a poor understanding of the molecular, cellular and functional basis of this heterogeneity. Our preliminary data have identified two major and distinct activated FB populations in mouse heart, skin and kidney following injury: Fibroblast specific protein 1 (FSP1)-expressing FBs and α-smooth muscle actin (αSMA)-expressing FBs, which appear at different time points after injury and remained as discrete populations during the healing process. Using mice which express GFP under FSP1 or α-SMA promoters we isolated these activated FB populations post cardiac injury and compared the gene expression profile of each population to those of FBs isolated from the uninjured heart. RNA sequencing indicated distinct molecular signatures. Particularly, pro-fibrotic genes such as type I collagen (Col I) and TGFβ signaling were significantly upregulated in αSMA-FBs, whereas genes involved in cellular homeostasis, tissue remodeling and cell-cell communication were upregulated in FSP1-FBs. Several studies, including from our group, have suggested that Secreted Frizzled-related protein 2 (sFRP2), a putative wnt pathway inhibitor, mediates wound repair by inhibiting fibrosis. We developed a novel mouse model in which we can induce expression of sFRP2 in activated FBs following injury. We found that early post-injury sFRP2 activation resulted in reduced fibrosis after myocardial, kidney and skin injuries without inhibiting tissue repair. Interestingly, our preliminary data showed that sFRP2 inhibited Col I synthesis and TGFβ signaling (but not Wnt signaling) only in αSMA-FBs but not in FSP-1 FBs in vitro. As such, sFRP2 represents an anti-fibrotic paracrine factor which may reduce tissue fibrosis by exerting distinct molecular effects on the post-injury (i.e. activated) FB subtypes. At the conclusion of this research proposal we will have characterized the cellular and functional heterogeneity of the major injury-activated FB populations and also have elucidated the mechanistic basis of the pro-reparative, antifibrotic effects of sFRP2 via its targeted and distinct effects on α-SMA-expressing FBs.