The chemokine CXCL9 inhibits neoangiogenesis and liver fibrosis in vivo

Aims: Recently we identified CXCR3 and its ligand CXCL9 as an antifibrotic pathway in the liver (Wasmuth et al. Gastroenterology 2009). Notably, ligands of CXCR3 also have angiostatic actions, rendering them as potential therapeutic options in liver fibrosis. The aims of the current projects were to characterise neoangiogenesis in CXCR3-/- and wild-type mice after CCl4 treatment and to investigate the possibility of influencing experimental liver fibrosis and angiogenesis by systemic administration of CXCL9.

Methods: Liver fibrosis was induced by repeated injections of CCl4 in CXCR3-/- and wild-type mice. In a separate experiment, CXCL9 or vehicle was administered concomitantly with CCl4 to wild-type mice for 6 weeks. Angiogenesis was quantified by fluorescence staining of CD31 and in vivo by VEGFR2 enrichment using fluorescence tomography. Fibrosis was assessed by staging of histology after sirius red staining. In vitro, chemotaxis of endothelial cells to VEGF and its inhibition by CXCL9 was analyzed by Boyden chamber experiments. Proliferation of endothelial cells was performed by Scratch and BRDU assay.

Results: Treatment of wild-type mice with CCl4 resulted in strongly enhanced neoangiogenesis. Compared to wild-type mice, CXCR3-/- mice showed a further significant increase of angiogenesis (p<0.01) and VEGFR2 levels in vivo. Notably, the systemic application of CXCL9 led to a significant inhibition of angiogenesis as well as of liver fibrosis (p<0.05). Functionally, CXCL9 represses the chemotactic and proliferative effect of VEGF on endothelial cells (p<0.05) in vitro.

Discussion: Genetic deletion of CXCR3 leads to enhanced liver fibrosis associated with increased angiogenesis that can be inhibited by systemic application of CXCL9. The modulation of angiogenesis and liver fibrosis by CXCL9 could be a promising target for new therapeutic approaches in chronic liver diseases.

CXCL9 - liver fibrosis - neoangiogenesis