microRNA-Based Approaches Targeting Alveolar Epithelial Cells as Pro-Regenerative Treatment in Idiopathic Pulmonary Fibrosis

Alveolar type II (ATIIs) to ATI cell trans-differentiation is an essential physiological process for effective alveolar repair after damage. In idiopathic pulmonary fibrosis (IPF) ATIIs are damaged and therefore cannot trans-differentiate ATIs, contributing to the progressive lung function damage. Available treatments for IPF patients, Nintedanib and Pirfenidone only reduce the progressive fibrotic scarring of the lungs, without curing the disease by stimulating the endogenous regenerative pathways. ATIIs represent a relevant target for the development of new pro-regenerative therapies for the lung. We performed a cell-based HTS assay on 2042 human microRNA mimics for their efficacy in regulating alveolar repair by promoting ATII to ATI trans-differentiation in primary mouse ATIIs. We identified 7 miRNAs increasing and 4 miRNAs reducing this process. With a translational perspective, we also validated 2 of these microRNAs in primary mouse fibroblasts, to evaluate their potential anti-fibrotic effect, in adenocarcinoma cell line (A549) to exclude any miRNA-induce tumorigenic effect, and in hepatocarcinoma cell line (HepG2), to exclude liver toxicity. Finally, we delivered the selected 2 microRNAs in a bleomycin-induced lung fibrosis mouse model using both viral (rAAV-6.2-FF) miRNA-delivery strategy to specifically target ATII cells or naked microRNAs to evaluate their efficacy in reducing lung fibrosis and promoting alveolar regeneration. We successfully identified 1 microRNA able to 1) promote ATII to ATI trans-differentiation in vitro 2) reduce fibroblasts activation 3) prevent and revert induced-lung fibrosis in mice, promoting alveolar regeneration.