Abstract Rationale Idiopathic pulmonary fibrosis (IPF) is an aggressive interstitial lung disease with a high mortality rate. Efforts to identify effective treatments are hindered by limited understanding of IPF pathogenesis. Among the molecular mediators of interest are the Inhibitor of DNA Binding (ID) proteins, key regulators of cellular differentiation, proliferation, and cell cycle progression. Despite their potential significance, the regulation, and the effects of ID proteins in IPF remain poorly understood. Methods Primary human lung fibroblasts were isolated from pulmonary tissue obtained from healthy control donors (NHLF) and patients diagnosed with IPF. Cell proliferation and fibroblast-to-myofibroblast differentiation were evaluated by BrdU incorporation assay and real-time qPCR, respectively. In vivo, three different approaches for ID1/ID3 inhibition (ID1/ID3 double KO mice, a pharmacological approach using a specific inhibitor, and a gene therapeutical approach using adeno-associated viruses expressing short hairpins targeting ID1 and ID3) were used to assess the effects of ID1/ID3 on lung function and pulmonary fibrosis using the bleomycin mouse model. Results qPCR results revealed a significant increase in ID1 and ID3 mRNA levels in human lung fibroblasts treated with TGF-β, a major contributor to lung fibrosis. Immunoblotting and qPCR showed upregulation of ID1 and ID3 mRNA and protein levels in the lungs and lung fibroblasts of mice and human patients with pulmonary fibrosis. ID1/ID3 inhibition, using a pharmacological inhibitor or specific siRNAs, decreased human lung fibroblasts proliferation and differentiation into myofibroblasts. ID1/ID3 deficient mice exhibited improved lung function and reduced lung fibrosis when exposed to the BLM model. A lung specific inhibition of ID1/ID3, using Adeno-associated Viruses expressing short hairpins targeting ID1 and ID3, effectively reversed pulmonary fibrosis in mice. Mechanistically, we found that ID1/ID3 inhibition decreased fibroblast proliferation through cell cycle genes and inhibited fibroblast differentiation through the MEK/ERK pathway. Conclusion Our findings demonstrate that targeting ID1 and ID3, either by pharmacological inhibition or genetic knockdown, effectively attenuates pulmonary fibrosis. These results establish the ID1/ID3 signaling as a promising therapeutic strategy for IPF. This abstract is funded by: American Heart Association and DC Women’s Board
Antar et al. (Fri,) studied this question.