Signals and pathways for transcriptional (de)regulation of Extracellular Matrix Protein 1 in hepatic stellate cells and mechanism of its matrisomal degradation during liver fibrosis

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

ECM1 protects LTGF-β1 activation and exhibits a negative correlation with liver fibrosis, a condition driven primarily by activated HSCs. More recent data on expression profiling of HSC populations have shown that ECM1 is abundant in quiescent HSCs and undergoes a downregulation during activation. This also explains our results that hepatocyte specific depletion of ECM1 shows not the same severe liver phenotype as the complete knock out, suggesting that ECM1 from HSCs may compensate. The ECM1 downregulation during HSC activation indicates a role in maintaining HSC quiescence. As one project part, we now want to know (1) the regulatory mechanism of ECM1 expression and the signals for its downregulation in HSCs. Then, we hypothesize that there exists a (2) mechanism that leads to early degradation of the existing ECM1 protein within the extracellular matrix of the healthy liver that is initiated early upon damage. Candidates for such a mechanism are for example protease(s) produced by HSCs in early stages of activation, e.g. in parallel with the production of the proteases that induce activation of LTGF-β. In an approach to clinically translate our knowledge on ECM1, we want to (3) establish an experimental therapy based on hepatocyte directed ECM1 mRNA delivery to treat fibrotic diseases in preclinical models, to be tested later, if successful, in a clinical trial. To substantiate our hypotheses, we want to investigate the following objectives: 1) Mechanistic details of ECM1 expression regulation in HSC: (a) Exploration of the signaling pathways maintaining ECM1 expression in quiescent HSCs; (b) investigation of the signaling pathways impeding ECM1 transcription during HSC activation; (c) confirmation of findings in pertinent clinical data to establish clinical relevance. 2) Mechanism of ECM1 degradation in early stages of liver fibrosis: (a) Identification of protease(s) mediating ECM1 degradation; (b) localize the cleavage site(s) recognized by the protease(s) in the ECM1 protein and identify the resulting cleavage fragments; (c) evaluation of the inhibitory/phenocopying potential of a peptide fragment covering the cleavage site for TGF-β signaling, HSC activation and fibrogenesis; (c) assessment of the ECM1 cleavage products (split) as diagnostic marker for early-stage liver fibrosis. 3) Establishment of a clinically useful ECM1-derived anti-fibrotic treatment, using (a) lipid nanoparticle based ECM1 mRNA delivery, or (b) alternatively encoding the identified fragment that covers the ECM1 protease cleavage site.

• DFG Programme: Research Grants