MicroRNA-326 regulates profibrotic functions of transforming growth factor-β in pulmonary fibrosis

Am J Respir Cell Mol Biol. 2014 May;50(5):882-92. doi: 10.1165/rcmb.2013-0195OC.


Idiopathic pulmonary fibrosis (IPF) is a fatal disorder resulting from the progressive remodeling of lungs, with no known effective treatment. Although transforming growth factor (TGF)-β has a well-established role in lung fibrosis, clinical experience with neutralizing antibodies to TGF-β has been disappointing, and strategies to directly suppress TGF-β1 secretion are needed. In this study we used a combination of in silico, in vitro, and in vivo approaches to identify microRNAs involved in TGF-β1 regulation and to validate the role of miR-326 in pulmonary fibrosis.We show that hsa-miR-326 regulates TGF-β1 expression and that hsa-miR-326 levels are inversely correlated to TGF-β1 protein levels in multiple human cell lines. The increase in TGF-β1 expression during the progression of bleomycin-induced lung fibrosis in mice was associated with loss of mmu-miR-326. Restoration of mmu-miR-326 levels by intranasal delivery of miR-326 mimics was sufficient to inhibit TGF-β1 expression and attenuate the fibrotic response. Moreover, human IPF lung specimens had markedly diminished miR-326 expression as compared with nonfibrotic lungs. Additional targets of miR-326 controlling TGF-β signaling and fibrosis-related pathways were identified, and miR-326 was found to down-regulate profibrotic genes, such as Ets1, Smad3, and matrix metalloproteinase 9, whereas it up-regulates antifibrotic genes, such as Smad7. Our results suggest for the first time that miR-326 plays a key role in regulating TGF-β1 expression and other profibrotic genes and could be useful in developing better therapeutic strategies for alleviating lung fibrosis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions
  • Animals
  • Cell Line
  • Gene Expression
  • Humans
  • Lung / metabolism
  • Lung / pathology
  • Lung / physiology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • MicroRNAs / genetics*
  • MicroRNAs / metabolism*
  • Pulmonary Fibrosis / genetics*
  • Pulmonary Fibrosis / metabolism*
  • Pulmonary Fibrosis / pathology
  • Transforming Growth Factor beta1 / genetics*
  • Transforming Growth Factor beta1 / metabolism*


  • 3' Untranslated Regions
  • MIRN326 microRNA, human
  • MicroRNAs
  • Transforming Growth Factor beta1