Pulmonary fibrosis is increasingly understood to involve dysfunction within and across multiple cellular compartments, with recent attention highlighting the involvement of pulmonary vascular dysfunction in failed repair and progression of fibrosis. Formulation and delivery of lung-targeting lipid nanoparticles may provide a means to selectively target the lung but not systemic vasculature. However, the feasibility and efficacy of such approaches in the fibrotic lung are unknown. We sought to test whether intravenously administered lung-targeting lipid nanoparticles can safely deliver mRNA to the healthy and fibrotic lung vasculature in young and aged mice and whether delivery of mRNA encoding a matricellular protein could promote fibrosis resolution. We used a Selective Organ Targeting (SORT) LNP formulation and characterized cell-specificity of delivery after bleomycin-induced lung fibrosis. We then delivered Ccn3 mRNA (encoding cellular communication network factor 3) to aged mice in the setting of established lung fibrosis and evaluated fibrotic regression and vascular repair. The matricellular protein encoded bywas previously identified by our group as an important regulator of lung endothelial function. We found that LNP delivery was lung specific and predominantly endothelial targeting in the setting of lung fibrosis. Delivery ofmRNA to aged mice via LNPs modestly reduced fibrosis and improved microvascular density in the lungs. Our results support the concept that cell-specific and repair-promoting cargos delivered via lung targeting LNPs may have utility for treatment of established fibrosis. Ccn3Ccn3
