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A2293 - In vivo Treatment with miR338-3p Reveals a Novel Epigenetic Regulator of Pulmonary Fibrosis
Author Block: A. Rackow1, J. L. Judge2, R. M. Kottmann3, C. F. Woeller4, T. H. Thatcher2, R. P. Phipps3, P. J. Sime5; 1Environmental Medicine, University of Rochester Medical Center, Rochester, NY, United States, 2University of Rochester, Rochester, NY, United States, 3Univ of Rochester, Rochester, NY, United States, 4University of Rochester Medical Center, Rochester, NY, United States, 5Univ of Rochester Medical Center, Rochester, NY, United States.
Rationale: Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease. The pathogenesis of IPF remains unclear. Our lab has identified a pro-fibrotic feed-forward loop in which TGFβ induces the enzyme lactate dehydrogenase A (LDHA) leading to generation of excess lactic acid which in turn activates latent TGFβ in the extracellular space. MicroRNAs (miRNAs) are epigenetic regulators of cellular metabolism demonstrated to be dysregulated in patients with pulmonary fibrosis. miR338-3p is significantly downregulated in patients with IPF and in silico analysis predicts that LDHA is a target of miR338-3p. We have already demonstrated that miR338-3p blocks production of lactate and prevents myofibroblast differentiation in vitro. Here, we hypothesize that miR338-3p will inhibit bleomycin induced pulmonary fibrosis in vivo. Methods: Six to eight week old C57/BL6 mice were administered 1.5 mg/kg bleomycin or saline via oropharyngeal aspiration (OA) on Day 0. Mice were subsequently administered miR338-3p (25 mg/kg) or a control miRNA on Days -1, 2, 8, 11 and 15 by OA. Mice were harvested on D7 and D21, and lung tissue was processed for mRNA, protein and histology. Results: As proof of principle, mice received two doses of miR338-3p before being sacrificed on Day 7. miR338-3p significantly reduced bleomycin induced collagen gene expression (Col1α1 and Col3α1) in treated mice compared to controls. To determine the effects of miR338-3p on the development of fibrosis we increased our dosing and extended our timepoint out to 21 days. On Day 21, lungs were collected for histology and hydroxyproline staining was performed on lung sections. miR338-3p reduced several key markers of fibrosis. Conclusions: miR338-3p is a novel anti-fibrotic agent which can be used to epigenetically target genes critical to the development and pathogenesis of pulmonary fibrosis. We have previously demonstrated that an inhibitor of LDHA significantly reduced fibrosis. Here we demonstrate that treatment with a regulatory miRNA can also attenuate fibrosis by inhibiting LDHA and dampening this pro-fibrotic feed forward loop. These data suggest an exciting new family of epigenetic regulators which may lead to a novel class of drug targets which can be interrogated to represent a new family of drug targets for pulmonary fibrosis.