Integrin-linked kinase mediates CTGF-induced epithelial to mesenchymal transition in alveolar type II epithelial cells

Abstract

Background: Overexpression of connective tissue growth factor (CTGF) in alveolar type II epithelial (AT II) cells disrupts alveolar structure, causes interstitial fibrosis, and upregulates integrin-linked kinase (ILK). Whether CTGF-ILK signaling induces epithelial to mesenchymal transition (EMT) in AT II cells is unknown. Methods: Transgenic mice with targeted overexpression of CTGF in AT II cells were generated utilizing the surfactant protein C (SP-C) gene promoter and doxycycline-inducible system. AT II cells were isolated from 4-wk-old CTGF-overexpressing (CTGF+) mice and control littermates, and cultured on Matrigel. Cells were transfected with ILK siRNA, and cell morphology and expression of cell differentiation markers were analyzed. results: The AT II cells from the control lungs grew in clusters and formed alveolar-like cysts and expressed SP-C. In contrast, the cells from CTGF+ lungs were spread and failed to form alveolar-like cysts. These cells expressed higher levels of CTGF, α smooth muscle actin (α-SMA), fibronectin and vimentin, the mesenchymal markers, suggesting EMT-like changes. Transfection with ILK siRNA not only dramatically attenuated ILK expression, but also decreased α-SMA expression as well as reversed cell morphological changes in CTGF+ AT II cells. conclusion: Overexpression of CTGF induces EMT in mouse primary AT II cells and this is mediated by ILK.

Inhibition of β-catenin signaling protects against CTGF-induced alveolar and vascular pathology in neonatal mouse lung

“…Second, it is unclear how CTGF activates β-catenin signaling in the neonatal lung. Our previous in vitro Articles studies have provided evidence that overexpression of CTGF in AT II cells induces EMT via ILK, suggesting an autocrine mechanism via integrin pathway (31). We have also showed that LRP5/6 is important in hyperoxia activation of β-catenin signaling in vascular smooth muscle cells but not in alveolar epithelial cells of the neonatal lung (39).…”

“…In CTGF transgenic lungs, part of the β-catenin nuclear translocation was detected in AT II cells (31). Furthermore, overexpression of CTGF induces β-catenin nuclear translocation and disrupts alveolar-like cyst formation in cultured AT II cells (12,31). In this study, we showed that administration of a β-catenin inhibitor significantly improved alveolarization in CTGF transgenic lungs.…”

“…Our previous studies have demonstrated that targeted overexpression of CTGF in AT II cells activates β-catenin signaling and disrupts alveolar epithelial cell homeostasis via an autocrine mechanism. In CTGF transgenic lungs, part of the β-catenin nuclear translocation was detected in AT II cells (31). Furthermore, overexpression of CTGF induces β-catenin nuclear translocation and disrupts alveolar-like cyst formation in cultured AT II cells (12,31).…”

The TGFβ/Notch axis facilitates Müller cell-to-epithelial transition to ultimately form a chronic glial scar

“…Figure S4 A-B). CTGF was already linked to MET in the pathogenesis of brotic diseases (e.g., renal, myocardial, pulmonary brosis; [43,44]. We could treat zebra sh for 24 h only as zebra sh treated further showed behavioral alterations (e.g., changes in activity, schooling behavior, social interaction) and, thus, excluded from the study.…”

A proteomics approach to identifying key protein targets involved in VEGF inhibitor mediated attenuation of bleomycin‐induced pulmonary fibrosis

“…ILK is a serine threonine protein kinase that is involved in regulating integrin‐mediated processes such as cell adhesion, proliferation, and extracellular matrix deposition and is a mediator of EMT . The only study exploring the role of ILK in BLM‐induced pulmonary fibrosis identified that although ILK expression was not altered and did not directly regulate pulmonary fibrosis, it mediated its profibrotic effect through the upregulation of vimentin .…”