Dicer1 Deficiency in the Idiopathic Pulmonary Fibrosis Fibroblastic Focus Promotes Fibrosis by Suppressing MicroRNA Biogenesis.

Abstract

RATIONALE:

The lung extracellular matrix (ECM) in idiopathic pulmonary fibrosis (IPF) mediates progression of fibrosis by decreasing fibroblast expression of miR-29 (microRNA-29), a master negative regulator of ECM production. The molecular mechanism is undefined. IPF-ECM is stiffer than normal. Stiffness drives fibroblast ECM production in a YAP (yes-associated protein)-dependent manner, and YAP is a known regulator of miR-29. Therefore, we tested the hypothesis that negative regulation of miR-29 by IPF-ECM was mediated by mechanotransduction of stiffness.

OBJECTIVES:

To determine how IPF-ECM negatively regulates miR-29.

METHODS:

We decellularized lung ECM using detergents and prepared polyacrylamide hydrogels of defined stiffness by varying acrylamide concentrations. Mechanistic studies were guided by immunohistochemistry of IPF lung and used cell culture, RNA-binding protein assays, and xenograft models.

MEASUREMENTS AND MAIN RESULTS:

Contrary to our hypothesis, we excluded fibroblast mechanotransduction of ECM stiffness as the primary mechanism deregulating miR-29. Instead, systematic examination of miR-29 biogenesis revealed a microRNA processing defect that impeded processing of miR-29 into its mature bioactive forms. Immunohistochemical analysis of the microRNA processing machinery in IPF lung specimens revealed decreased Dicer1 expression in the procollagen-rich myofibroblastic core of fibroblastic foci compared with the focus perimeter and adjacent alveolar walls. Mechanistically, IPF-ECM increased association of the Dicer1 transcript with RNA binding protein AUF1 (AU-binding factor 1), and Dicer1 knockdown conferred primary human lung fibroblasts with cell-autonomous fibrogenicity in zebrafish and mouse lung xenograft models.

CONCLUSIONS:

Our data identify suppression of fibroblast Dicer1 expression in the myofibroblast-rich IPF fibroblastic focus core as a central step in the mechanism by which the ECM sustains fibrosis progression in IPF.

• Authors: Jeremy Herrera, Daniel J Beisang, Mark Peterson, Colleen Forster, Adam Gilbertsen, Alexey Benyumov, Karen Smith, Christopher E Korenczuk, Victor H Barocas, Kacey Guenther, Ryan Hite, Lin Zhang, Craig A Henke, Peter B Bitterman
• Journal: American journal of respiratory and critical care medicine (Am J Respir Crit Care Med) Vol. 198 Issue 4 Pg. 486-496 (08 15 2018) ISSN: 1535-4970 [Electronic] United States
• PMID: 29579397 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• MIRN29a microRNA, human
• MicroRNAs
• DICER1 protein, human
• Ribonuclease III
• DEAD-box RNA Helicases

Topics

• Animals
• Cell Proliferation
• Cells, Cultured
• DEAD-box RNA Helicases (genetics)
• Disease Models, Animal
• Extracellular Matrix (metabolism)
• Fibroblasts (metabolism)
• Fibrosis (genetics, pathology)
• Humans
• Idiopathic Pulmonary Fibrosis (genetics, metabolism, pathology)
• Lung (metabolism, pathology)
• Mice
• MicroRNAs (metabolism)
• Ribonuclease III (genetics)
• Zebrafish