TGF-R2 signaling coordinates pulmonary vascular repair after viral injury in mice and human tissue

Disruption of pulmonary vascular homeostasis is a central feature of viral pneumonia, wherein endothelial cell (EC) death and subsequent angiogenic responses are critical determinants of the outcome of severe lung injury. A more granular understanding of the fundamental mechanisms driving reconstitution of lung endothelium is necessary to facilitate therapeutic vascular repair. Here, we demonstrated that TGF-beta signaling through TGF-beta R2 (transforming growth factor-beta receptor 2) is activated in pulmonary ECs upon influenza infection, and mice deficient in endothelial Tgfbr2 exhibited prolonged injury and diminished vascular repair. Loss of endothelial Tgfbr2 prevented autocrine Vegfa (vascular endothelial growth factor alpha) expression, reduced endothelial proliferation, and impaired renewal of aerocytes thought to be critical for alveolar gas exchange. Angiogenic responses through TGF-beta R2 were attributable to leucine-rich alpha-2-glycoprotein 1, a proangiogenic factor that counterbalances canonical angiostatic TGF-beta signaling. Further, we developed a lipid nanoparticle that targets the pulmonary endothelium, Lung-LNP (LuLNP). Delivery of Vegfa mRNA, a critical TGF-beta R2 downstream effector, by LuLNPs improved the impaired regeneration phenotype of EC Tgfbr2 deficiency during influenza injury. These studies defined a role for TGF-beta R2 in lung endothelial repair and demonstrated efficacy of an efficient and safe endothelial-targeted LNP capable of delivering therapeutic mRNA cargo for vascular repair in influenza infection.