Targeting mechanotransduction in myofibroblast like cells
File(s)
Author(s)
Lachowski, Dariusz
Type
Thesis
Abstract
Mechanical stimuli applied by the extracellular matrix (ECM) and the cells play an important role in the maintenance of tissue homeostasis. Mechanosensing and mechanotransduction are two processes by which cells transform mechanical forces into biochemical signals and adapt to changes in the microenvironment. Imbalanced cell response can create a positive feedback loop and lead to the pathological conditions, such as pancreatic ductal adenocarcinoma, which is characterised by the presence of extensive fibrotic stroma produced and maintained by pancreatic stellate cells (PSC). Here, it is shown that PSC are reversibly activated through mechanosensing of fibrosis-mimicking stiff substrates. Under the application of this mechanical cue, PSC exhibit rigidity-guided movement (durotaxis). This pattern of migration, which is regulated by a stiffness-dependent asymmetric distribution of active and inactive focal adhesion protein, is also observed in hepatic stellate cells (HSC).
HSC, durotactically migrating to the fibrotic sites, can perpetuate the disease through their stiffness-initiated activation and resulting aberrant matrix remodelling capabilities. Experiments revealed a mechanical network allowing HSC to maintain fibrotic ECM by decreasing the matrix-digesting enzyme MMP-9 expression and activity, and increasing the activity of its secreted inhibitor, TIMP-1. Furthermore, these results shed light on a new mechanism, through which stiff matrix can initiate exocytosis. This is identified as an effect of membrane homeostasis maintenance, where an increase in plasma membrane tension via β1 integrin mechanosensing and RhoA activation is followed by tension-relieving secretion.
With RhoA and cell activation as a common factor in the cell mechanical response, final experiments focused on G protein-coupled receptor (GPER), here identified as a novel mechanoregulator in fibroblasts. GPER activation decreases RhoA activity and impacts overall mechanical response in cells, opening new possibilities for potential therapies in cancer and fibrosis.
HSC, durotactically migrating to the fibrotic sites, can perpetuate the disease through their stiffness-initiated activation and resulting aberrant matrix remodelling capabilities. Experiments revealed a mechanical network allowing HSC to maintain fibrotic ECM by decreasing the matrix-digesting enzyme MMP-9 expression and activity, and increasing the activity of its secreted inhibitor, TIMP-1. Furthermore, these results shed light on a new mechanism, through which stiff matrix can initiate exocytosis. This is identified as an effect of membrane homeostasis maintenance, where an increase in plasma membrane tension via β1 integrin mechanosensing and RhoA activation is followed by tension-relieving secretion.
With RhoA and cell activation as a common factor in the cell mechanical response, final experiments focused on G protein-coupled receptor (GPER), here identified as a novel mechanoregulator in fibroblasts. GPER activation decreases RhoA activity and impacts overall mechanical response in cells, opening new possibilities for potential therapies in cancer and fibrosis.
Version
Open Access
Date Issued
2019-08
Date Awarded
2020-03
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
del Rio Hernandez, Armando
Sponsor
European Research Council
Grant Number
282051
Publisher Department
Bioengineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)