Mitochondrial fission and bioenergetics mediate human lung fibroblast durotaxis
Ting Guo, Chun-sun Jiang, Shan-Zhong Yang, Yi Zhu, Chao He, A. Brent Carter, Veena B. Antony, Hong Peng, Yong Zhou
Ting Guo, Chun-sun Jiang, Shan-Zhong Yang, Yi Zhu, Chao He, A. Brent Carter, Veena B. Antony, Hong Peng, Yong Zhou
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Research Article Cell biology Pulmonology

Mitochondrial fission and bioenergetics mediate human lung fibroblast durotaxis

Abstract

Pulmonary fibrosis is characterized by stiffening of the extracellular matrix. Fibroblasts migrate in the direction of greater stiffness, a phenomenon termed durotaxis. The mechanically guided fibroblast migration could be a crucial step in the progression of lung fibrosis. In this study, we found primary human lung fibroblasts sense increasing matrix stiffness with a change of mitochondrial dynamics in favor of mitochondrial fission and increased production of ATP. Mitochondria polarize in the direction of a physiologically relevant stiffness gradient, with conspicuous localization to the leading edge, primarily lamellipodia and filopodia, of migrating lung fibroblasts. Matrix stiffness–regulated mitochondrial fission and durotactic lung fibroblast migration are mediated by a dynamin-related protein 1/mitochondrial fission factor–dependent (DRP1/MFF-dependent) pathway. Importantly, we found that the DRP1/MFF pathway is activated in fibrotic lung myofibroblasts in both human IPF and bleomycin-induced mouse lung fibrosis. These findings suggest that energy-producing mitochondria need to be sectioned via fission and repositioned in durotactic lung fibroblasts to meet the higher energy demand. This represents a potentially new mechanism through which mitochondria may contribute to the progression of fibrotic lung diseases. Inhibition of durotactic migration of lung fibroblasts may play an important role in preventing the progression of human idiopathic pulmonary fibrosis.

Authors

Ting Guo, Chun-sun Jiang, Shan-Zhong Yang, Yi Zhu, Chao He, A. Brent Carter, Veena B. Antony, Hong Peng, Yong Zhou

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Figure 3

Redistribution of mitochondria in lamellipodia/filopodia is associated with human lung fibroblast durotaxis.

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Redistribution of mitochondria in lamellipodia/filopodia is associated w...
(A) Human lung fibroblasts were initially seeded at ~2 kPa region (circle) on stiffness gradient gels. Cells completely attached to the gels after 2 hours. Cells were allowed to migrate on stiffness gradient gels for 7 days. The overall distance of cell migration (750 μm) was the distance between the centroids of the cell population at 2 hours (red cross) and 7 days (green cross). The distance of durotactic migration (700 μm) was defined as the distance of migration in the direction of the stiffness gradient. Scale bar = 500 μm. (B) Human lung fibroblasts cultured on stiffness gradient gels or gels with uniform stiffness (soft and stiff) were stained with MitoTracker (red) and phalloidin (green). Nuclei were stained with DAPI (blue). Cell body was divided into pre- (right) and postnuclear (left) regions. Mitochondrial distribution in pre- and postnuclear regions was quantified as the percentage of mitochondria in each region. Bar graphs represent mean ± SD per cell from 30 cells derived from 3 human participants (n = 10 cells per participant) under each condition. Box plots show the interquartile range (box), median (line), and minimum and maximum (whiskers). Mitochondrial polarization was evaluated by differential distribution of mitochondria in pre- versus postnuclear regions. Statistical analysis was performed by 1-way ANOVA. Scale bar = 20 μm. (C) Human lung fibroblasts migrating on stiffness gradient gels were stained with MitoTracker (red) and ER Tracker (green). Nuclei were stained with DAPI (blue). Colocalization of mitochondria and ER from 30 individual cells was quantified by Pearson’s correlation coefficient analysis. Scale bar = 20 μm. (D) Human lung fibroblasts were cultured on stiffness gradient gels in the presence or absence of nocodazole. Cells were stained with MitoTracker (red) and anti–α-tubulin antibody (green). Nuclei were stained with DAPI (blue). Scale bar = 20 μm.