Fibrocytes in the Pathogenesis of Sickle Cell Lung Disease

描述(申请人提供)：镰状细胞病(SCD)合并镰状细胞肺损伤(SCLI)可导致慢性镰状细胞肺病(CSCLD)。CSCLD以慢性间质性肺疾病为特征，伴有继发性肺高压和肺纤维化。循环纤维细胞(CD45+COL1+)的发现改变了我们对肺纤维化发病机制的看法。在临床前模型中，纤维细胞在介导肺纤维化中发挥作用。在IPF患者的循环和肺中发现纤维细胞升高，其循环水平的大小与这些患者的预后较差有关。将这些发现推广到SCD，我们发现使用临床前人类SCD转基因小鼠模型，表达CXC趋化因子受体4(CXCR4)的纤维细胞在促进肺纤维化方面发挥了重要作用，与肺源性CXCL12的表达有关。此外，我们还发现SCD患者循环中CXCR4+成纤维细胞增多。基于我们的初步数据，我们提出了一个全面的假设，即纤维细胞在介导SCLI的发病机制和CSCLD的发展中发挥了关键作用。为了验证这一假设，我们设计了以下特定目标，在分子、细胞、临床前动物模型和患者水平上评估纤维细胞生物学，以确定这些细胞是否对SCLI和CSCLD的发展起作用：1.SCD小鼠纤维细胞定位与纤维化和血管重塑的相关性，并阐明CXCL12/CXCR4在促进骨髓扩张、骨髓动员、2.检测mTOR抑制可导致CXCL12/CXCR4表达下调，肺组织纤维细胞外渗功能受损，这与SCLI转基因动物肺血管重塑和纤维化的减轻直接相关。3.确定纤维细胞数量和活化表型(即SMA+和pSmad2/3+纤维细胞)与成人SCD患者限制性肺疾病是否相关。该项目的长期目标将确定成纤维细胞是促进SCLI发病的关键细胞。这些发现将支持以纤维细胞为靶点的策略将导致新的治疗方法，以减弱其在CSCLD发病机制中的生物学作用。 与公共卫生相关：镰状细胞病是非裔美国人中最常见的遗传性疾病。虽然改善了对镰状细胞病的患者护理，提高了这些患者的存活率，但不幸的是，他们经历了慢性器官问题的频率增加，特别是与肺有关的问题。这些患者可能会发展成慢性肺部疾病，与血压升高和肺部疤痕组织的形成有关。这项提案中的研究将集中在镰状细胞病患者循环中发现的一种特殊细胞的作用，这可能导致我们在这些患者的肺部看到的问题。

DESCRIPTION (provided by applicant): Sickle cell disease (SCD) with associated sickle cell lung injury (SCLI) can lead to the development of chronic sickle cell lung disease (CSCLD). CSCLD is characterized as chronic interstitial lung disease with secondary pulmonary hypertension and fibrosis. The discovery of circulating fibrocytes (CD45+Col1+) has now changed our view on the pathogenesis of pulmonary fibrosis. Fibrocytes play a role in mediating pulmonary fibrosis in pre-clinical models. Fibrocytes are found elevated in the circulation and lungs of IPF patients, and the magnitude of their circulating levels is associated with a worse prognosis in these patients. Extending these findings to SCD, we found using a preclinical transgenic mouse model of human SCD that CXC chemokine receptor 4 (CXCR4) expressing fibrocytes play a significant role in promoting pulmonary fibrosis related to the expression of lung-derived CXCL12. In addition, we found that CXCR4+ fibrocytes were elevated in the circulation of patients with SCD. Based on our preliminary data, we generated an overall hypothesis that fibrocytes play a critical role in mediating the pathogenesis of SCLI and development of CSCLD. To test this postulate, we designed the following specific aims to assess fibrocyte biology at the molecular, cellular, pre-clinical animal model, and patient levels to determine if these cells contribute to SCLI and the development of CSCLD: 1. Correlation of fibrocyte localization in SCD mice with fibrosis and vascular remodeling, and elucidation of the role of CXCL12/CXCR4 in promoting BM expansion, BM mobilization, and extravasation of these cells into the lung during the pathogenesis of SCLI: 2. Determination of mTOR inhibition results in down-regulation of CXCL12/CXCR4 and impairment of fibrocyte extravasation in the lungs that directly correlates with attenuation of the pulmonary vascular remodeling and fibrosis during the pathogenesis of SCLI in transgenic SCD animals. 3. Determine whether fibrocyte number and activated phenotype (i.e., (SMA+ and pSmad2/3+ fibrocytes) are associated with restrictive lung disease in adult SCD patients. Long-term objectives of this project will establish that fibrocytes are critical cells in promoting the pathogenesis of SCLI. These findings will support the notion that strategies to target fibrocytes will lead to novel therapies to attenuate their biology in the pathogenesis of CSCLD. PUBLIC HEALTH RELEVANCE: Sickle cell disease is the most common inherited disorder in African-Americans. While improved patient care in Sickle cell disease has led to increased survival of these patients, they unfortunately experience an increase frequency of chronic organ problems, especially related to the lung. These patients can develop a chronic lung condition that is associated with elevated blood pressure and formation of scar tissue in their lungs. The studies in this proposal will focus on the role of a special cell found in the circulation of patients with sickle cell disease that may contribute to the problems we see in the lungs of these patients.