Ph.D Thesis

Ph.D StudentMawasi Nidal
SubjectImproving Cirrhotic Liver Regeneration Following Partial
DepartmentDepartment of Medicine
Supervisor ASSOCIATE PROF. Gad Spira
Full Thesis textFull thesis text - English Version


Hepatic fibrosis involves excess deposition of extracellular connective tissue of which collagen type I forms the predominant component. Hepatic stellate cells (HSCs) are the major source of extracellular matrix. They can also influence the extracellular matrix through synthesis of matrix metalloproteinases (MMPs) and their tissue inhibitors, TIMPs. Left untreated, hepatic fibrosis develops into cirrhosis, often linked with hepatocellular carcinoma (HCC). Owing to the fact that cirrhotic liver regeneration is impaired, resection of HCC associated with cirrhosis is questionable. The aim of the present study was to determine the potential of halofuginone, an anti-fibrotic alkaloid agent, to improve rat cirrhotic liver regeneration following 70% partial hepatectomy (PHx) and to unravel the mechanism by which it affects liver fibrosis both in thioacetamide (TAA) administered rats and in HSCs. In addition, we tested the potential of a combined treatment of halofuginone and transfection in vivo of vascular endothelial growth factor (VEGF) to further support liver regeneration. Cirrhotic rats were treated with halofuginone alone or subjected to VEGF transfection along with halofuginone treatment. Both groups underwent PHx and liver regeneration was monitored by mass and proliferating cell nuclear antigen immunohistochemistry. The Ishak staging system and hydroxyproline content were used to evaluate fibrosis stage. Halofuginone alleviated fibrosis and improved cirrhotic liver regeneration. Yet, the combination of the two, halofuginone and VEGF proved more effective than each one of them. To assess halofuginone’s mechanism of action, two models were used in vivo: the prevention and the treatment models. In the first, halofuginone was administered along with TAA. In the second; halofuginone was given following cessation of TAA administration. In both models TAA administration was associated with elevated levels of pro-collagen 1(I), MMP-2, MMP-3, MMP-13 and their inhibitor TIMP-1. Spontaneous recovery from liver fibrosis was accompanied by reduced levels of all the above. Treatment with halofuginone further augmented the reductive pattern. In the prevention model halofuginone attenuated the expression of all parameters tested. In vitro, halofuginone was associated with down regulation of pro-collagen 1(I) and MMP-2 and increasing levels of MMP-3 and MMP-13 transcripts. These data suggest that halofuginone’s therapeutic effect on fibrotic rats is the result of multiple pathways which includes inhibition of pro-collagen α1(I) synthesis and acceleration of ECM degradation. The multifunctional effect of halofuginone as observed in the present study may place the drug at the centre of future studies aimed at improving survival of patients with hepatocellular carcinoma and cirrhosis undergoing surgical resection.