Identification of vascular-derived signals for alveolar lung repair

描述（由申请人提供）：目前用于修复受损肺组织的治疗方法在恢复肺功能方面没有重大的长期益处。我们已经阐述了肺毛细血管内皮细胞（PCEC）不仅是输送氧气和营养物质的被动管道，而且通过建立支持性生态位在肺再生和修复中发挥关键作用的概念。该项目的首要目标是确定肺损伤后，通过产生生长因子（定义为血管分泌因子）激活PCEC支持肺泡再生而不引起异常纤维化的机制。我们已经建立了PCEC的表型定义，并表明左肺全肺切除术（PNX）后，PCEC上表达的VEGF-A受体-2（VEGFR 2）和FGFR 1的激活导致金属蛋白酶MMP 14的上调。MMP 14通过暴露隐藏的EGF受体配体结构域刺激肺泡再生。值得注意的是，将表达MMP 14的野生型PCEC移植和植入VEGFR 2/FGFR 1缺陷小鼠的肺中恢复了肺泡化而不刺激纤维化。然而，PNX激活PCEC产生血管分泌因子的机制尚不清楚。我们的初步数据表明，PNX，高氧和博莱霉素诱导的肺损伤后，髓样细胞和血小板被招募到受伤的肺组织，并通过沉积的VEGF-A和基质衍生因子-1（SDF- 1，CXCl 12）激活其同源受体VEGFR 2和CXCR 4表达的PCECs产生血管分泌因子启动肺修复。基于这些数据，我们假设肺损伤后，造血细胞被募集到肺毛细血管，并通过部署VEGF-A和SDF-1刺激VEGFR 2 + CXCR 4 + PCEC产生支持肺修复的肺泡活性血管分泌因子，同时防止异常纤维化。我们计划利用我们实验室开发的肺损伤模型和技术，包括将羊膜细胞重编程为血管内皮细胞（rAC-VEC）的新方法，以执行以下实验：目的1。分析VEGFR 2 + PCECs中CXCR 4激活促进和维持血管分泌介导的肺修复的机制。目标2.检查招募的造血细胞在介导PCEC活化、血管分泌因子产生和肺修复同时预防异常纤维化中对受损肺血管的作用。目标3. 确定造血细胞和PCEC之间的相互串扰在诱导血管分泌信号和加速肺泡再生和修复中的作用。我们提出的实验将为临床前策略的开发奠定基础，其中通过适当激活PCEC或移植肺特异性工程化PCEC将允许刺激肺修复，从而改善呼吸功能并最大限度地减少纤维化组织的适应不良重塑。

DESCRIPTION (provided by applicant): Current therapeutic approaches for the repair of the injured lung tissue have had no major long-term benefit in restoring pulmonary function. We have set forth the concept that pulmonary capillary endothelial cells (PCECs) are not just passive conduits that deliver oxygen and nutrients but rather by establishing a supportive niche play a key role in lung regeneration and repair. The overarching goal of this project is to define the mechanism by which after lung injury, activated PCECs through production of growth factors, defined as angiocrine factors, support alveolar regeneration without provoking aberrant fibrosis. We have established the phenotypic definition of PCECs and have shown that after left lung pneumonectomy (PNX), activation of the VEGF-A receptor-2 (VEGFR2) and FGFR1 expressed on the PCECs leads to upregulation of the metalloproteinase MMP14. MMP14 via unmasking cryptic EGF-receptor ligand domains stimulate alveolar regeneration. Notably, transplantation and engraftment of wild-type PCECs expressing MMP14 into the lung of VEGFR2/FGFR1 deficient mice restores lung alveolarization without stimulating fibrosis. However, the mechanism by which PNX activates PCECs to produce angiocrine factors is unknown. Our preliminary data indicate that after PNX, hyperoxia and bleomycin-induced lung injury, myeloid cells and platelets are recruited to the injured lung tissue and by deposition of VEGF-A and stromal derived factor-1 (SDF- 1, CXCl12) activate their cognate receptors VEGFR2 and CXCR4 expressed on PCECs to produce angiocrine factors initiating lung repair. Based on these data, we hypothesize that after lung injury, hematopoietic cells are recruited to pulmonary capillary vessels and by deploying VEGF-A and SDF-1 stimulate VEGFR2+CXCR4+ PCECs to produce alveolar-active angiocrine factors that support lung repair, while preventing aberrant fibrosis. We plan to leverage lung injury models and technologies developed in our lab, including a new approach to reprogram amniotic cells into vascular endothelial cells (rAC-VECs) to execute the following experiments: Aim 1. Dissect the mechanism by which activation of CXCR4 in VEGFR2+ PCECs elicits and maintains angiocrine-mediated lung repair. Aim 2. Examine the role of recruited hematopoietic cells to damaged lung vessels in mediating PCEC activation, angiocrine factor production and lung repair while preventing aberrant fibrosis. Aim 3. Determine the role of reciprocal crosstalk between hematopoietic cells and PCECs in inducing angiocrine signaling and accelerating alveolar regeneration and repair. Our proposed experiments will set the stage for development of pre-clinical strategies in which by proper activation of PCECs or transplantation of lung-specific engineered PCECs will allow for stimulating lung repair, thus improving respiratory functions and minimizing maladaptive remodeling into fibrotic tissues.