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dc.contributor.advisorIredale, John
dc.contributor.advisorSimpson, Ian
dc.contributor.authorGordon-Walker, Timothy Thomas
dc.contributor.authorWalker, Timothy Thomas Gordon
dc.date.accessioned2014-10-15T15:36:23Z
dc.date.available2014-10-15T15:36:23Z
dc.date.issued2014-07-05
dc.identifier.urihttp://hdl.handle.net/1842/9537
dc.description.abstractIntroduction: The development of liver fibrosis is characterised by dramatic changes in the biomechanical composition and mechanical properties of the extracellular matrix (ECM). Increases in matrix stiffness associated with inflammation and fibrosis are implicated in promoting cancer development. Clinical studies have demonstrated a close association between increases in liver stiffness and the incidence of hepatocellular carcinoma (HCC). The effect of changes in matrix stiffness on tissue-resident hepatic progenitor cells (HPC) is unknown. Aberrant HPC proliferation has been implicated in the pathogenesis of HCC. It was hypothesised that changes in the stiffness of the cellular microenvironment are important in regulating the behaviour of liver-resident cell populations and may promote the development of HCC. Aims: i) to determine how changes in the stiffness of the cancer cell niche might regulate proliferation, differentiation and chemotherapeutic resistance in HCC; ii) to determine the relationship between changes in liver stiffness and hepatic progenitor cell (HPC) response in rodent models of chronic liver disease; and iii) to determine whether changes in the stiffness of the HPC niche regulate proliferation and differentiation in these cells. A secondary aim of the thesis was to characterise the pattern of histological changes observed in rodent models of chronic hepatic congestion and whether this might provide insight into the effect of oedema and congestion on the development of liver fibrosis. Methods: Cell culture experiments in HCC (Huh7/ HepG2) and HPC cell lines were performed using a system of ligand-coated polyacrylamide (PA) gel supports of variable stiffness. The stiffness of the PA supports (expressed as shear modulus) was altered across a physiological change (1-12kPa) corresponding to values encountered in normal and fibrotic livers. Thiacetamide and carbon tetrachloride (CCl4) models of liver fibrosis were used to investigate the relationship between increasing liver fibrosis, changes in matrix stiffness and HPC response. The pattern of histological changes in the liver in response to hepatic congestion was assessed in two unrelated murine models of dilated cardiomyopathy; the python and CREB S133A mice. Results: Increases in matrix stiffness, as would be encountered in liver fibrosis, promote HCC cell proliferation. Increasing matrix stiffness is associated with enhanced basal and hepatocyte growth factor-mediated signalling though ERK, PKB/ Akt and STAT3. Stiffness-dependent HCC cell proliferation is modulated by β1-integrin and focal adhesion kinase. Increasing matrix stiffness is associated with a reduction in chemotherapy-induced apoptosis in HCC cells. However, following chemotherapy there was an increase in the frequency of clone-initiating cells for cells maintained in a low stiffness environment. Flow cytometry in HepG2 cells demonstrated that culture in a low stiffness environment was associated with an increase in the frequency of the stem cell markers CD44, CD133 and CXCR-4. This effect was further enhanced in the presence of chemotherapy. There is a close association between HPC numbers and liver stiffness measurements in a rat CCl4 model of chronic liver fibrosis. The major expansion in HPC numbers in this model coincides with a similarly large increase in fibrous tissue deposition. In vitro experiments using PA supports demonstrate that increasing matrix stiffness promotes the proliferation of both primary murine HPCs and an immortalised HPC line (BMOL). Changes in matrix stiffness regulate the expression of hepatocyte and biliary markers in BMOL cells. Histological studies in both the Python and CREB S133A models reveal findings consistent with acute on chronic cardiac hepatopathy (ischaemic hepatitis). Features of chronic passive congestion and centrilobular necrosis are present concurrently and develop rapidly. Bridging fibrosis and cirrhosis are not present. Conclusions: Physiologically-relevant changes in matrix stiffness regulate proliferation, differentiation, chemotherapeutic-resistance and stem cell marker expression in HCC cells. Similarly, increases in matrix stiffness are closely correlated to HPC response in vivo and regulate HPC proliferation and differentiation in vitro.en_US
dc.contributor.sponsorMRC Clinical Research Training Fellowshipen_US
dc.language.isoenen_US
dc.publisherThe University of Edinburghen_US
dc.relation.hasversionSchrader J, Gordon-Walker TT, Aucott RL, Van Deemter M, Quaas A, Walsh S, Benton D, Forbes SJ, Wells RG and Iredale JP. Matrix stiffness modulates proliferation, chemotherapeutic response and dormancy in hepatocellular carcinoma cells. Hepatology. 2011: 53(4); 1192-1205en_US
dc.relation.hasversionGordon-Walker TT, Schrader J, Aucott RL, Van Deemter M, Benton D, Forbes SJ, Wells RG and Iredale JP. Matrix stiffness modulates proliferation, differentiation and chemotherapy resistance in hepatocellular carcinoma. Hepatology. 2010: 52(4); 936Aen_US
dc.relation.hasversionGordon-Walker TT, Schrader J, Benton D, Van Deemter M, Forbes SJ, Wells RG and Iredale JP. Matrix stiffness regulates proliferation, differentiation and chemotherapeutic responsiveness in hepatocellular carcinoma. Gut. 2010: 59; A26-27en_US
dc.relation.hasversionFallowfield J, Hayden AL, Aucott RL, Schrader J, Gordon-Walker TT, Mole D, Collins JE and Iredale JP. Relaxin inhibits hepatic myofibroblast contractility and modulates portal hypertension in vivo. Hepatology. 2010: 52(4); 343Aen_US
dc.relation.hasversionSchrader J, Gordon-Walker TT, Aucott R and Iredale JP. Co-culture of hepatoma cells with hepatic stellate cells promotes tumour cell proliferation and survival. J Hepatology 2009; 50 Supplement 1: S200en_US
dc.subjecthepatocellular carcinomaen_US
dc.subjectmatrix stiffnessen_US
dc.subjectliver progenitor cellen_US
dc.subjectcongestive cardiac failureen_US
dc.titleEffect of matrix stiffness on the behaviour of liver resident cell populations in chronic liver disease and hepatocarcinogenesisen_US
dc.typeThesis or Dissertationen_US
dc.type.qualificationlevelDoctoralen_US
dc.type.qualificationnamePhD Doctor of Philosophyen_US


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