CCL2-dependent infiltrating macrophages promote angiogenesis in progressive liver fibrosis
Matthias Bartneck1, Josef Ehling2,3, Xiao Wei1, Viktor Fech1, Chrisfer Boeck1, Kanishka Hittotiya4, Tom Luedde1, Fabian Kiessling2, Twan Lammers2,5, Christian Trautwein1, Frank Tacke1
1Department of Medicine III, Medical Faculty, RWTH University, Aachen, Germany; 2Department of Experimental Molecular Imaging, Medical Faculty, RWTH University, Aachen, Germany; 3Institute of Pathology, Medical Faculty, RWTH University, Aachen, Germany; 4Institute of Pathology, Medical Faculty, RWTH University, Bonn, Germany; 5Department of Targeted Therapeutics, MIRA Instifute for Biomedical Technology and Technical Medicine, Enschede, Netherlands
Purpose of the study: In conditions of chronic liver injury, angiogenesis is associated with progressive fibrosis and may contribute to the development of hepatocellular carcinoma. Although hypoxia-induced expression of vascular endothelial growth factor (VEGF) occurs in advanced fibrosis, we hypothesized that inflammation may endorse hepatic angiogenesis already at the early stages of liver fibrosis. Methods: We developed a novel micro-CT-based in vivo imaging approach for the visualization and quantification of hepatic blood volume and studied the development of angiogenesis and fibrosis progression. Angiogenesis was studied after 6 weeks of repetitive carbon tetrachloride (CCl4) liver injury in C57BL/6 mice, with and without inhibition of the chemokine CCL2 by an antagonist (mNOX-E36). Results summary: Angiogenesis and fibrosis progression were closely correlated in chronic liver injury and were determined non-invasively by functional contrastenhanced μCT (Figure). Inflammatory monocyte-derived macrophages (MDM) massively accumulated in injured livers and co-localized with newly formed vessels in portal tracts. MDM expressed high levels of proangiogenic factors like VEGF. Pharmacological inhibition of monocyte infiltration by targeting CCL2 almost completely prevented fibrosis-associated angiogenesis, but not fibrosis progression, as assessed by in vivo μCT scans. Specifically, MDM primarily promoted sprouting angiogenesis within the portal vein tract based on liver endothelial cell staining. Conclusion: We demonstrate that inflammation-associated angiogenesis is promoted by CCL2-dependent monocytes during fibrosis progression and introduce an innovative in vivo μCT methodology to monitor angiogenesis and anti-angiogenic therapy effects in experimental liver fibrosis. Our data suggest that fibrosis progression, at least at its early stages, is largely independent from hepatic angiogenesis.
Christian Trautwein - Grant/Research Support: BMS, Novartis, BMS, Novartis; Speaking and Teaching: Roche, BMS, Roche, BMS
Frank Tacke - Grant/Research Support: Novartis, Noxxon; Speaking and Teaching: Roche, BMS, Gilead, Falk, MSD, Janssen
The following people have nothing to disclose: Matthias Bartneck, Josef Ehling, Xiao Wei, Viktor Fech, Christer Baeck, Kanishka Hittatiya, Tom Luedde, Fabian Kiessling, Twan Lammers