Extracellular Matrix Protein 1 in liver homeostasis, chronic disease and regeneration

• Applicant: Professor Steven Dooley, Ph.D.
• Subject Area: Gastroenterology ; Pathology ; Public Health, Healthcare Research, Social and Occupational Medicine ; Veterinary Medical Science
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 445166284

The transforming growth factor (TGF)-β promotes liver fibrosis by activating hepatic stellate cells. TGF-β also contributes to liver regeneration after acute damage, most probably by terminating hepatocyte proliferation. The underlying mechanisms controlling TGF-β activation are not entirely clear. We have identified extracellular matrix protein 1 (ECM1) as crucial factor in liver pathophysiology. ECM1 is abundant in healthy human and mouse livers. It is synthesized by hepatocytes and upon liver damage, ECM1 levels are decreasing quickly. ECM1KO mice spontaneously develop liver fibrosis and die at an age of ~2 months. Liver tissue from these mice is characterized by high levels of phosphorylated Smad2/3 without showing upregulation of TGF-β expression. AAV8 mediated ectopic expression of soluble TGFβR2 in livers of ECM1KO mice and of ECM1 in 6 weeks CCl4-treated mice prolonged survival and prevented fibrogenesis. Preliminary mechanistic data indicate that ECM1 is involved in deposition and stability of latent TGF-β in the liver matrix. We aim to deepen insights on the relevance of this critical factor in liver for several aspects: (1) Using in silico and in vitro promoter analyses and stimulation/inhibition experiments, we will delineate ECM1 regulation in hepatocytes. Findings will be validated in healthy mice and during liver damage in the CCl4 model. This will provide knowledge on potential fibrosis treatment approaches by modulating ECM1 expression. (2) Preliminary data show distinct patterns of ECM1 downregulation in CCl4 and partial hepatectomy models of liver regeneration. By AAV8 mediated re-expression, we will delineate the impact of ECM1 on efficacy of regeneration, and evaluate the relation to TGF-β activation. (3) We will generate inducible ECM1KO mice to deplete ECM1 at selected disease stages during chronic liver disease (CLD) dynamics, e.g. in the CCl4 model. (4) Mechanistic insights on ECM1 functions in matrix deposition and activation of latent TGF-β will be obtained by studying protein-protein interactions and using a TGF-β/Smad reporter system, as well as by testing latent TGF-β binding partners and activators. Data will be complemented by colocalization studies in human patient samples and in mice expressing Tomato-ECM1. This mouse line will be generated and subsequently chronically challenged with CCl4. Thus, we will gain mechanistic knowledge on how ECM1 modulates TGF-β activation in CLD and regeneration. (5) Diagnosis: With extensive support from collaborating colleagues from several hospitals, we will test the predictive value of ECM1 blood levels for diagnosis of CLD stages. An ELISA is established and preliminary data show evidence of correlation. To establish ECM1 as biomarker, we will analyze abundance in large patient cohorts. In summary, the discoveries of this research project will provide important insights into mechanisms of liver fibrosis and regeneration that may have potential for clinical translation.

• DFG Programme: Research Grants