Identification of Paired-related Homeobox Protein 1 as a key mesenchymal transcription factor in Idiopathic Pulmonary Fibrosis

Matrix remodeling is a salient feature of idiopathic pulmonary fibrosis (IPF). Targeting cells driving matrix production and remodeling could be a promising avenue for IPF treatment. Analysis of public transcriptomic database identified paired-related homeobox protein-1 (PRRX1) as an upregulated mesenchymal transcription factor (TF) in IPF. We confirmed that PRRX1 isoforms were upregulated in IPF lung tissue and strongly expressed by lung fibroblasts. In vitro, PRRX1 expression was up-regulated by cues associated with proliferative and anti-fibrotic properties in lung fibroblasts, while IPF fibroblast-derived matrix increased PRRX1 TFs expression in a PDGFR dependent manner in control ones. Meanwhile, signals promoting myofibroblastic differentiation decreased PRRX1 TF. We demonstrated that PRRX1 inhibition decreased fibroblast proliferation by downregulating the expression of S phase cyclins. PRRX1 inhibition also impacted TGF-{beta} driven myofibroblastic differentiation by inhibiting SMAD2/3 phosphorylation through phosphatase PPM1A upregulation and TGFBR2 downregulation, leading to a TGF-{beta} response global decrease. Finally, targeted inhibition of Prrx1 TFs attenuated fibrotic remodeling both in vivo with intra-tracheal antisense oligonucleotides in the bleomycin mice model of lung fibrosis and ex vivo using mouse and Human precision-cut lung slices stimulated with fibrosis cytokine cocktail. Altogether, our results identified PRRX1 as a mesenchymal transcription factor driving myofibroblastic phenotype and lung fibrogenesis. Brief SummaryInhibition of a single fibroblast-associated transcription factor, namely paired-related homeobox protein 1, is sufficient to dampen lung fibrogenesis.