Pleural mesothelial cell transformation into myofibroblasts and haptotactic migration in response to TGF-β1 in vitro

Abstract

Idiopathic pulmonary fibrosis (IPF) is a disease of unknown etiology characterized by the development of subpleural foci of myofibroblasts that contribute to the exuberant fibrosis noted in the pulmonary parenchyma. Pleural mesothelial cells (PMC) are metabolically dynamic cells that cover the lung and chest wall as a monolayer and are in intimate proximity to the underlying lung parenchyma. The precise role of PMC in the pathogenesis of pulmonary parenchymal fibrosis remains to be identified. Transforming growth factor (TGF)-beta1, a cytokine known for its capacity to induce proliferative and transformative changes in lung cells, is found in significantly higher quantities in the lungs of patients with IPF. High levels of TGF-beta1 in the subpleural milieu may play a key role in the transition of normal PMC to myofibroblasts. Here we demonstrate that PMC activated by TGF-beta1 undergo epithelial-mesenchymal transition (EMT) and respond with haptotactic migration to a gradient of TGF-beta1 and that the transition of PMC to myofibroblasts is dependent on smad-2 signaling. The EMT of PMC was marked by upregulation of alpha-smooth muscle actin (alpha-SMA), fibroblast specific protein-1 (FSP-1), and collagen type I expression. Cytokeratin-8 and E-cadherin expression decreased whereas vimentin remained unchanged over time in transforming PMC. Knockdown of smad-2 gene by silencing small interfering RNA significantly suppressed the transition of PMC to myofibroblasts and significantly inhibited the PMC haptotaxis. We conclude that PMC undergo EMT when exposed to TGF-beta1, involving smad-2 signaling, and PMC may be a possible source of myofibroblasts in IPF.

A neutrophil elastase inhibitor prevents bleomycin-induced pulmonary fibrosis in mice

“…TGF-b is most efficiently secreted as a large latent complex and most TGF-b is stored in the extracellular matrix before activation [19]. A key feature of IPF is the presence of high levels of inactive precursor form TGF-b1 in the lung parenchyma [27].…”

Dendritic cell chemotaxis in 3D under defined chemokine gradients reveals differential response to ligands CCL21 and CCL19

“…However, our current understanding of DC chemotaxis is largely qualitative and limited to 2D (16)(17)(18)(19). Furthermore, while it is well established that cell migration requires different mechanisms in 3D vs. 2D (20)(21)(22)(23)(24)(25), nearly all chemotaxis studies to date have been performed in 2D or 2.5D conditions largely because of the lack of model systems in which well defined gradients can be created in 3D while evaluating cell invasion (especially because DC migration is relatively fast compared to the time scale of diffusion for gradient establishment).…”

miR-18a-5p Inhibits Sub-pleural Pulmonary Fibrosis by Targeting TGF-β Receptor II

“…3 Nasreen et al 9 reported that TGF-b1 induces PMC EMT, and PMCs are a source of myofibroblasts in IPF. PMCs undergoing EMT produce large amount of collagen and contribute to the overdeposition of ECM in sub-pleural fibrosis.…”

“…5,7,8 PMCs with EMT are considered a source of myofibroblasts, which are the key cells within fibroproliferative foci. 3,8,9 Bleomycin is a classical inducer of pulmonary fibrosis model. In animal models, lung fibrosis induced by intraperitoneal bleomycin injection exhibits a sub-pleural fibrotic distribution similar to what is seen in human IPF.…”