Dll4 plays a critical role in HBV-associated liver fibrogenesis

Background & Aims: Notch signaling is crucial in the development of metazoans, determining cell fate, and is directly linked to multiple human organ disorders. In human, 5 Notch ligands (Jagged–1, Jagged–2, Delta–1, Delta–3 and Delta–4) and 4 receptors (Notch–1, Notch–2, Notch–3 and Notch–4) have been identified. Mutation of Jagged–1 gene leads to Alagille syndrome. However, patients with Alagille syndrome usually do not progress into serious liver fibrosis. In the present study, we investigated the role of Notch ligands in HBV associated liver fibrogenesis. Methods: The expression of Notch ligands, including Jagged1, Jagged2, Delta-like ligand (Dll)1, Dll3 and Dll4, was measured in 130 patients with chronic HBV infection by immunohistochemistry. The effect of Notch ligands was as well examined in TGF-β treated hepatic stellate cells (HSCs). Results: Immunohistochemistry analysis revealed positive expression of Jagged1, Dll3 and Dll4 in fibrotic liver tissues from chronic HBV infected patients. Distinct from Jagged1 and Dll3, which are mainly found in cholangiocytes and hepatocytes, sinusoidal cells and portal tracts were positive for Dll4. Confocol microscopy analysis confirmed these Dll4-positive cells were α-smooth muscle actin (α-SMA) positive, indicating that Dll4 was upregulated in activated HSCs or myofibroblasts in chronic HBV infected patients. Dll4 positive liver cells remarkably correlated with inflammatory grade (r=0.6, P<0.001) and fibrotic stage (r=0.68, P<0.001) in HBV infected patients. In vitro, knock-down of Dll4 significantly increased TGF-β induced protein expression of connective tissue growth factor and collagen I in CFSC cells, a cell line derived from cirrhotic rat HSCs. Conclusions: Dll4 plays a crucial role in liver fibrogenesis via influencing TGF-β dependent activation of HSCs and extracelluar matrix production.

fibrosis - HSC