The role of Fli1 in myeloid cells and its contribution to cardiac fibrosis

摘要 心脏病是美国的主要死亡原因，而纤维化是大多数心脏病患者的共同终点。 疾病。最近的研究表明，单核细胞和巨噬细胞是心脏纤维化的重要介质。 我们发现系统性硬化症(SSC)患者单核细胞中转录因子FLI1水平降低。 患者，一种以广泛的组织纤维化和纤维化为特征的自身免疫性结缔组织病 心肌病。人心脏成纤维细胞与去除FlI1的单核细胞共培养后 诱导半乳糖凝集素-3和其他激活标志物在髓系细胞和丰富的胶原沉积 成纤维细胞，这种作用可被mTOR抑制剂雷帕霉素阻断。初步实验表明， 利用LysMCre小鼠通过Cre介导的重组缺失单核/巨噬细胞中的FlI1 (LysMCre/Fli1fl/fl)易致小鼠心肌纤维化。 根据已发表的数据和我们的初步结果，我们假设巨噬细胞中缺乏FLI1 会导致SSC纤维化和心肌病，而雷帕霉素可以阻断这些作用。为了测试这一点 假设，我们提出了以下具体目标： 特异性目标1：确定血管紧张素转换酶抑制因子1缺失后导致肝纤维化的分子机制 单核/巨噬细胞。我们预计单核/巨噬细胞中FLI1的减少将导致 迁移，心肌细胞肥大，并将促进细胞外基质的产生，通过FLI1/Galetin- 3/mTOR通路。 特异性目标2：确定巨噬细胞中FLI1的缺失是否会导致活体心肌病。我们 预计LysMCre/Fli1fl/fl小鼠将有更强的炎症渗透、心脏纤维化和舒张期 对血管紧张素II的反应功能障碍，这将被雷帕霉素抑制。 具体目的3.研究髓系FLI1是否在SSc相关性心肌病中起作用。我们预计 患有心肌病的SSc患者的单核细胞和巨噬细胞将表现出与 LysMCre/Fli1fl/f1巨噬细胞。 提出的研究应该能让我们更好地了解心脏纤维化的分子机制。 在SSc，并确定未来治疗SSc-心肌病是否应该针对FLI1和髓系 通过雷帕霉素系统，从而为潜在的更安全、更有效的治疗提供了基础。

ABSTRACT Heart disease is the leading cause of death in the USA and fibrosis is a common endpoint for most cardiac diseases. Recent research has shown monocytes and macrophages are important mediators of heart fibrosis. We found reduced levels of the transcription factor Fli1 in monocytes isolated from systemic sclerosis (SSc) patients, an autoimmune connective tissue disease characterized by widespread tissue fibrosis and fibrotic cardiomyopathy. Co-culture of human cardiac fibroblasts and Fli1 depleted monocytes resulted in potent induction of galectin-3, and alternative activation markers in myeloid cells, and abundant collagen deposition by fibroblasts, and this was blocked by the mTOR inhibitor Rapamycin. Preliminary experiments revealed that deletion of Fli1 in monocytes/macrophages via Cre-mediated recombination using LysMCre mice (LysMCre/Fli1fl/fl) predisposed mice to develop myocardial fibrosis. Based on published data and our preliminary results, we hypothesize that Fli1 deficiency in macrophages contributes to SSc fibrosis and cardiomyopathy, and that Rapamycin may block these effects. To test this hypothesis, we propose the following specific aims: Specific aim 1: Determine the molecular mechanism leading to fibrosis following Fli1 depletion in monocytes/macrophages. We expect that decreased Fli1 in monocytes/macrophages will result in enhanced migration, cardiomyocyte hypertrophy, and will promote the production of extracellular matrix via Fli1/galetin- 3/mTOR pathway. Specific aim 2: Determine whether loss of Fli1 in macrophages leads to cardiomyopathy in vivo. We expect that the LysMCre/Fli1fl/fl mice will have enhanced inflammatory infiltrates, heart fibrosis and diastolic dysfunction in response to Angiotensin II, which will be inhibited by Rapamycin. Specific aim 3. Investigate whether myeloid Fli1 has a role in SSc-associated cardiomyopathy. We expect that monocytes and macrophages from SSc patients with cardiomyopathy will display a similar phenotype to the LysMCre/Fli1fl/fl macrophages. The studies proposed should allow us to gain better understanding of the molecular mechanisms of heart fibrosis in SSc, and determine whether future treatments for SSc-cardiomyopathy, should target Fli1 and the myeloid system via Rapamycin, thus providing the basis for potentially safer, more effective therapies.