Genome editing of Spp1 by inhalable CRISPR/Cas9 formulation for treating pulmonary fibrosis

Secreted phosphoprotein 1 (Spp1) encoding osteopontin (OPN), a matrix cell protein with pro-inflammatory and pro-necrotic tissue properties, plays a crucial role in the onset and progression of idiopathic pulmonary fibrosis (IPF). In order to treat IPF by taking advantage of Spp1, we herein developed an inhalable system composed of calcium phosphate/ poly (lactic-co-glycolic acid) (PLGA) core-shell nanoparticles which are loaded with CRISPR/Cas9 system targeting Spp1 to investigate its therapeutic potential. Specifically, the plasmid encoding Cas9 and single-guide RNA (sgRNA) selectively targeting Spp1 gene was first condensed by calcium phosphate to form Cas9 complexes, which was then encapsulated by PLGA to formulate into a gene-editing inhalable delivery system (termed CaP/Cas9/PLGA). Interestingly, the aerosolized inhaled delivery of CaP/Cas9/PLGA nanoparticles results in the effective traverse of mucosal barriers to fibrotic lungs, where they are internalized by lung cells without inducing noticeable cytotoxicity. Following endo/lysosomal escape and gene expression of CRISPR system, the disruption of Spp1 gene by Cas9/sgRNA induces the mutation frequency exceeding 30 %, resulting in efficient down-regulation of OPN level. In a bleomycin-induced pulmonary fibrosis mouse model, the inhalation of aerosolized CaP/Cas9/PLGA complexes significantly attenuates fibrosis development and improves lung function with undetectable systemic toxicity. This current study defines an innovative inhalable gene-editing formulation and offers a promising gene therapy modality for treating IPF.