TRPV4 mediates myofibroblast differentiation and pulmonary fibrosis in mice
Shaik O. Rahaman, … , Daniel J. Tschumperlin, Mitchell A. Olman
Shaik O. Rahaman, … , Daniel J. Tschumperlin, Mitchell A. Olman
Published December 1, 2014; First published November 3, 2014
Citation Information: J Clin Invest. 2014;124(12):5225-5238. https://doi.org/10.1172/JCI75331.
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Research Article Pulmonology

TRPV4 mediates myofibroblast differentiation and pulmonary fibrosis in mice

Abstract

Idiopathic pulmonary fibrosis (IPF) is a fatal fibrotic lung disorder with no effective medical treatments available. The generation of myofibroblasts, which are critical for fibrogenesis, requires both a mechanical signal and activated TGF-β; however, it is not clear how fibroblasts sense and transmit the mechanical signal(s) that promote differentiation into myofibroblasts. As transient receptor potential vanilloid 4 (TRPV4) channels are activated in response to changes in plasma membrane stretch/matrix stiffness, we investigated whether TRPV4 contributes to generation of myofibroblasts and/or experimental lung fibrosis. We determined that TRPV4 activity is upregulated in lung fibroblasts derived from patients with IPF. Moreover, TRPV4-deficient mice were protected from fibrosis. Furthermore, genetic ablation or pharmacological inhibition of TRPV4 function abrogated myofibroblast differentiation, which was restored by TRPV4 reintroduction. TRPV4 channel activity was elevated when cells were plated on matrices of increasing stiffness or on fibrotic lung tissue, and matrix stiffness–dependent myofibroblast differentiation was reduced in response to TRVP4 inhibition. TRPV4 activity modulated TGF-β1–dependent actions in a SMAD-independent manner, enhanced actomyosin remodeling, and increased nuclear translocation of the α-SMA transcription coactivator (MRTF-A). Together, these data indicate that TRPV4 activity mediates pulmonary fibrogenesis and suggest that manipulation of TRPV4 channel activity has potential as a therapeutic approach for fibrotic diseases.

Authors

Shaik O. Rahaman, Lisa M. Grove, Sailaja Paruchuri, Brian D. Southern, Susamma Abraham, Kathryn A. Niese, Rachel G. Scheraga, Sudakshina Ghosh, Charles K. Thodeti, David X. Zhang, Magdalene M. Moran, William P. Schilling, Daniel J. Tschumperlin, Mitchell A. Olman

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Figure 6

Increased matrix stiffness augments TRPV4-induced Ca2+ influx and myofibroblast differentiation.

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Increased matrix stiffness augments TRPV4-induced Ca2+ influx and myofib...
(A and B) HLFs were plated (15,000 cells per well) on collagen-coated (100 μg/ml) hydrogels with varying degrees of stiffness (1, 6, 8, and 25 kPa) under vehicle-treated or AB1-treated (50 μM) conditions, with or without TGF-β1 (2 ng/ml, 24 hours). (A) GSK-induced (10 nM) Ca2+ influx, measured as in Figure 2C, is increased by stiffness and abrogated by AB1. (B) Fluorescence microscopy analysis shows that the TGF-β1 response in myofibroblast differentiation seen with increasing stiffness of the matrix is dependent on TRPV4 channel activity. *P < 0.05, **P < 0.01 by ANOVA; n > 12 cells per group. Int., integrated. (C and D) HLFs were plated on normal or stiffer fibrotic lung tissue sections with or without TRPV4 antagonist, AB1 (50 μM). (C) Representative confocal micrographs (original magnification, ×63) of phalloidin-stained F-actin (red). (D) Quantification of actin stress fiber density from C. The results are expressed as mean ± SD. *P < 0.05 by ANOVA for vehicle-treated normal lung vs. fibrotic lung; †P < 0.05 by ANOVA for vehicle-treated vs. AB1-treated fibrotic lung.