Endothelial cell-derived MMP14 in lung alveolar regeneration and fibrosis

 描述(申请人提供)：肺部疾病是美国死亡的主要原因。目前的治疗主要依靠短期药物治疗和肺移植，持续的临床益处有限。刺激肺泡上皮细胞(AECs)的增殖可以提高肺的自我修复能力。然而，AEC在病变肺中的扩张往往因为缺乏来自周围功能失调的微环境/壁龛细胞的上皮活性信号而受到阻碍。因此，肺修复受损通常会引起过度的疤痕形成和纤维化，这可能会抑制上皮细胞的扩张。我们已经证明，手术切除小鼠的左肺叶(肺切除术)会导致右肺代偿性肺泡化。这种肺泡再生由血小板和肺毛细血管内皮细胞(PCECs)刺激。肺切除术(PNX)后，沉积在右肺的血小板上调PCECs中的膜型金属蛋白酶MMP14，刺激肺泡上皮干/祖细胞如2型AECs(AEC2s)的增殖。因此，血小板上调PCECs上皮细胞活性的MMP14，以诱导肺泡再生。因为这个“血管壁龛”很容易进入血液循环，所以它是一个有吸引力的靶点，使治疗性肺修复成为可能。内皮MMP14通过释放跨膜性肝素结合EGF的胞外区(HB-EGF)激活EGF受体(EGFR)来刺激AEC的扩张。初步数据表明，定位于内皮细胞小窝的MMP14通过从细胞外基质中释放抗纤维化分子富含半胱氨酸的蛋白61(Cyr61)来抑制肺纤维化。血小板介导的成纤维细胞生长因子受体1(FGFR1)在PCECs中的激活诱导MMP14的腔内浓缩。因此，我们假设内皮细胞小窝中的MMP14促进肺再生并阻止纤维化。为了验证这一假设，我们将使用反复气管内注射博莱霉素诱导的小鼠肺切除和肺纤维化模型来1)确定内皮MMP14如何处理HB-EGF和Cyr61来调节肺再生和纤维化；2)研究FGFR1对MMP14功能的依赖调节。此外，我们还旨在将PCEC靶向基因转导系统与血小板输注相结合，在PCEC的小窝中定向MMP14，以促进肺再生，防止纤维化。这项研究将有助于阐明微环境信号，如内皮MMP14如何调节肺再生和纤维化。拟议实验的积极结果将有助于设计一种“利基靶向”的再生疗法，以促进无纤维化的功能性肺修复。

 DESCRIPTION (provided by applicant): Lung diseases are the leading cause of mortality in the U.S. Current therapy mainly relies on short-term pharmacotherapy and lung transplantation with limited sustained clinical benefit. Stimulating propagation of alveolar epithelial cells (AECs could increase the lung's capacity to undergo self-repair. Nevertheless, AEC expansion in a diseased lung is frequently handicapped by the lack of epithelially-active cues from the dysfunctional surrounding microenvironmental/niche cells. Consequently, impaired lung repair often provokes excessive scar formation and fibrosis that might inhibit epithelial expansion. We have shown that surgical removal of left lung lobe (pneumonectomy) in mice causes compensatory re-alveolarization in the right lungs. This alveolar regeneration is stimulated by platelets and pulmonary capillary endothelial cells (PCECs). Following pneumonectomy (PNX), platelets deposited in the right lungs upregulate membrane-type metalloproteinase MMP14 in PCECs to stimulate the proliferation of alveolar epithelial stem/progenitor cells such as type 2 AECs (AEC2s). Thus, platelets upregulate epithelially active MMP14 in PCECs to elicit alveolar regeneration. Since this "hemo-vascular niche" is readily accessible to the circulation, it represents an attractive target to enable therapeutic lung repair. Endothelial MMP14 stimulates AEC expansion by releasing the ectodomain of transmembrane heparin-binding EGF (HB-EGF) that activates EGF receptor (EGFR). Pilot data suggest that MMP14 localized in endothelial cell caveolae blocks lung fibrosis via liberating anti-fibrotic molecule cysteine-rich protein 61 (Cyr61 from extracellular matrix. Caveolar enrichment of MMP14 is induced by platelet-mediated fibroblast growth factor receptor 1 (FGFR1) activation in PCECs. Thus, we hypothesize that MMP14 in the endothelial cell caveolae promotes lung regeneration and blocks fibrosis. To test this hypothesis, we will use mouse pneumonectomy and lung fibrosis model induced by repeated intratracheal injection of Bleomycin to 1) define how endothelial MMP14 processes HB-EGF and Cyr61 to regulate lung regeneration and fibrosis; 2) investigate FGFR1-dependent regulation of MMP14 function. Moreover, we also aim to combine PCEC-targeted gene transduction system and platelet infusion to direct MMP14 in the caveolae of PCECs to promote lung regeneration and prevent fibrosis. This study will help to elucidate how microenvironmental cues such as endothelial MMP14 modulate lung regeneration and fibrosis. Positive outcome of the proposed experiments will help to design a "niche-targeted" regenerative therapy to facilitate functional lung repair without fibrosis.