Circulating Fibrocytes in Hyperoxic Lung Vascular Remodeling

在许多患有BPD的婴儿中，肺微血管发育和肺动脉（PA）异常 观察到结构重塑。后一过程包括阻力PA的异常肌化 在肺外周，以及中膜肥大，外膜增厚和纤维化更近端PA。 BPD肺血管发育异常和结构重建的原因尚不清楚 明白长期以来，人们一直认为增厚的PA中细胞的扩增群体起源于 通过常驻肺成纤维细胞和平滑肌细胞（SMC）的增殖，以及通过 将肺原纤维细胞转化为肌成纤维细胞。然而，新的实验证据表明， 组织间充质细胞来源（成纤维细胞、肌成纤维细胞、SMC）。不同类型 间充质祖细胞是循环白细胞的一个亚群，称为纤维细胞， 作为愈合伤口中结构组织重塑和纤维化的主要贡献者，博来霉素诱导的 肺损伤和哮喘我们最近已经证明了慢性炎症中纤维细胞的PA积累 缺氧新生儿肺动脉高压，并表明这些循环细胞是至关重要的， 在这种情况下可以看到肺血管结构重塑。我们的初步数据表明， 纤维细胞也有助于在暴露于以下物质的新生大鼠和小鼠中观察到的血管重塑： 高氧（BPD动物模型）。初步数据支持氧化失衡和内皮素在 纤维细胞向肺的募集。因此，我们建议测试的总体假设，在 在高氧诱导的肺损伤的情况下，循环纤维细胞被募集到肺中， 间充质细胞的祖细胞，并显著促进肺血管重塑， EC-SOD和ET-1在此过程中起重要作用。康贝特人将以 纤维细胞向肺和肺血管系统募集的机制及其作用 到使用药理学策略和遗传模型来操纵 可能参与纤维细胞募集和分化的分子。这些实验将导致 更好地了解BPD的血管变化，并最终在选择性治疗的发展 减少循环间充质祖细胞向高氧肺募集的策略 患有BPD的人类婴儿

In many infants with BPD abnormal pulmonary microvascular development and pulmonary artery (PA) structural remodeling are observed. The latter process includes abnormal muscularization of resistance PA in the lung periphery, as well as medial hypertrophy, adventitial thickening and fibrosis in more proximal PA. The causes of abnormal pulmonary vascular development and structural remodeling in BPD are poorly understood. It has long been assumed that the expanded population of cells in the thickened PA originates via proliferation of resident lung fibroblasts and smooth muscle cells (SMC), as well as via differentiation of resident lung fibroblasts into myofibroblasts. However, new experimental evidence suggests a non-resident source for tissue mesenchymal cells (fibroblasts, myofibroblasts, SMC). Among different types of mesenchymal progenitors, a subpopulation of circulating leukocytes, termed fibrocytes, has been proposed as a major contributor to the structural tissue remodeling and fibrosis in healing wounds, bleomycin-induced lung injury, and asthma. We have recently demonstrated the robust PA accumulation of fibrocytes in chronic hypoxic neonatal pulmonary hypertension and showed that these circulating cells are crucial for the pulmonary vascular structural remodeling seen in that setting. Our preliminary data suggest that circulating fibrocytes also contribute to the vascular remodeling observed in neonatal rats and mice exposed to hyperoxia (animal models of BPD). Preliminary data support a role for oxidant imbalances and endothelin in the recruitment of fibrocytes to the lung. We therefore propose to test the overall hypothesis that, in the setting of hyperoxia-induced lung injury, circulating fibrocytes are recruited to the lung where they act as progenitors of mesenchymal cells, and contribute significantly to pulmonary vascular remodeling and pulmonary hypertension, and that EC-SOD and ET-1 play critical roles in this process. We will determine the mechanisms involved in the recruitment of fibrocytes to the lung and lung vasculature and their contribution to remodeling using both pharmacologic strategies and genetic models to manipulate expression of molecules potentially involved in fibrocyte recruitment and differentiation. These experiments will result in a better understanding of vascular changes in BPD and, ultimately in the development of selective therapeutic strategies to decrease the recruitment of circulating mesenchymal progenitors to the hyperoxic lung in human infants with BPD.