Endothelial cell-derived MMP14 in lung alveolar regeneration and fibrosis

 描述（由申请人提供）：肺部疾病是美国死亡的主要原因。目前的治疗主要依赖于短期药物治疗和肺移植，持续临床获益有限。刺激肺泡上皮细胞（AECs）的增殖可以增加肺进行自我修复的能力。然而，AEC在患病肺中的扩增经常受到来自功能失调的周围微环境/生态位细胞的上皮活性线索的缺乏的阻碍。因此，受损的肺修复通常引起过度的瘢痕形成和纤维化，这可能抑制上皮扩张。我们已经证明，手术切除小鼠左肺叶（肺切除术）会导致右肺的代偿性肺泡再形成。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，右肺中沉积的血小板上调PCEC中的膜型金属蛋白酶MMP 14，以刺激肺泡上皮干/祖细胞如2型AEC（AEC 2）的增殖。因此，血小板上调PCEC中的上皮活性MMP 14以引起肺泡再生。由于这种“血液-血管生态位”易于进入循环，因此它代表了能够实现治疗性肺修复的有吸引力的靶点。内皮MMP 14通过释放激活EGF受体（EGFR）的跨膜肝素结合EGF（HB-EGF）的胞外域刺激AEC扩增。初步数据表明，定位于内皮细胞小窝的MMP 14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（Cyr 61）来阻断肺纤维化。血小板介导的成纤维细胞生长因子受体1（FGFR 1）激活PCEC诱导MMP 14的小窝富集。因此，我们假设内皮细胞小窝中的MMP 14促进肺再生并阻断纤维化。为了验证这一假设，我们将使用小鼠肺切除术和肺纤维化模型诱导的博莱霉素重复intrichelheal注射1）定义内皮MMP 14如何处理HB-EGF和Cyr 61调节肺再生和纤维化; 2）研究MMP 14功能的FGFR 1依赖性调节。此外，我们还将联合收割机靶向PCEC的基因转导系统与血小板输注相结合，引导MMP 14进入PCEC的小窝，以促进肺再生，防止纤维化。这项研究将有助于阐明微环境因素如内皮MMP 14如何调节肺再生和纤维化。所提出的实验的积极结果将有助于设计一种“利基靶向”再生疗法，以促进功能性肺修复而不发生纤维化。

 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.