View Abstract

A4347 - Wilms’ Tumor 1 Is a Positive Regulator of Fibroblast Activation in Severe Fibrotic Lung Disease
Author Block: V. Sontake1, R. Kasam2, B. Geereddy3, D. Sinner4, E. S. White5, A. Jegga6, S. K. Madala7; 1Pulmonary Medicine, Cincinnati, OH, United States, 2Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States, 3National Institute of Nutrition, Hyderabad, India, 4Pulmonary Biology, Cincinnati, OH, United States, 5Univ of Michigan, Ann Arbor, MI, United States, 6Cincinnati Childrens Hospital Medical Center, Cincinnati, OH, United States, 7Pulm Med, Cincinnati Children's Hosp, Cincinnati, OH, United States.
Rationale: Developmental pathways that are usually suppressed in adult lung tissue but aberrantly reactivated in the pathogenesis of pulmonary fibrosis. Wilms’ tumor 1 (WT1) is a novel transcription regulator that is critical for the lung development but shown to be down-regulated in the adult lungs. Our recent study demonstrated that WT1 is upregulated in IPF and mouse models of pulmonary fibrosis. However, the role of WT1 in fibroblast activation such as proliferation, myofibroblast transformation, and extracellular matrix (ECM) protein production are unknown. Here, we hypothesized that WT1 acts as a positive regulator of fibroblast activation and the loss of WT1 attenuates fibroblast activation and pulmonary fibrosis.
Methods: To determine whether WT1 act as a positive regulator of fibroblast activation, we overexpressed the WT1 in primary lung resident fibroblasts and assessed the fibroproliferation, myofibroblast transformation and ECM production in vitro. To assess the role of WT1 in vivo, we measured fibroblast proliferation, myofibroblast accumulation and ECM production in WT1 haploinsufficient and wild-type mice during TGFα- and bleomycin-induced pulmonary fibrosis.
Results: Our in vitro data demonstrate that overexpression of WT1 alone is sufficient to induce the fibroblast proliferation, myofibroblast transformation and ECM production in primary fibroblasts isolated from normal lungs. Similarly, the knockdown of WT1 transcripts has attenuated fibroblast proliferation in lung resident fibroblasts isolated from fibrotic lung lesions of IPF or TGFα model. Importantly, using two alternative mouse models, we demonstrate that the reduced WT1 levels attenuate fibroproliferation, myofibroblast accumulation and ECM deposition during TGFα- and bleomycin-induced pulmonary fibrosis.
Summary: Our findings for the first time demonstrate that WT1 functions as a positive regulator of fibroblast proliferation, myofibroblast transformation, and ECM production in the pathogenesis of pulmonary fibrosis. Consistently, loss of WT1 led to decreased proliferation, myofibroblast accumulation and pulmonary fibrosis in vivo. Combined with our previous work, this study demonstrates that the reactivation of WT1 in IPF lungs is responsible for severe fibrotic lung disease.