The Research Of Notch's Role In Murine Liver Fibrosis

Cirrhosis is a worldwide disease which seriously threatens people's health. Liver fibrosis is the common and key path in the development of cirrhosis for most chronic liver diseases. Whether complete resolution of cirrhosis can occur is currently unknown. However, recent reports show that fibrotic liver can return to near-normal architecture under effective treatments. Thus the phage of fibrosis is a critical stage for treatment. Liver fibrosis is a wound-healing response for chronic liver injury, which contains the progress of liver damage and regeneration, the chronic inflammation, and the dynamic balance between synthesis and degradation of matrix. The anti-fibrotic therapy focuses on these aspects.The Notch signaling pathway is conserved during evolution which mediates the signal transduction between neighbor cells. Notch signaling plays an important role in cell fate decision, cell differentiation, proliferation and apoptosis. But there is no report about the relation of Notch signaling and chronic liver injury. Previous researches show that Notch signaling has essential roles in the development of bile ducts and liver regeneration, and regulates the development and function of immune cells. From these reports we speculate that Notch signaling would play a critical role in liver fibrosis. Several experiments were included as follows:1. Established the model of CCl4-induced liver fibrosis, and detected the changes of Notch associated moleculars by real-time PCR and immuno- ?uorescence stainings.2. Established the fibrosis model in RBP-J knockout mice, and detected the fibrosis level with the HE, Masson, and Sirius Red staining.3. Distinguished the function of liver factor and bone marrow factor with bone marrow transplantation experiments.4. Quantified the infiltrating inflammatory cells recruited to injured livers by FACS.5. Detected the macrophages'function, such as phagocytosis, the expression of MMPs and polarization.6. Compared the miRNAs profiles between RBP-J knockout bone marrow derived macrophages and control macrophages.7. Rescue the impaired macrophages with miRNA in vitro and vivo.Results: Notch signaling was upregulated in murine fibrotic livers. RBP-J knockout leaded to increased inflammatory cells in liver, more serious liver damage and liver fibrosis. BMT showed that Notch signaling mediated anti-fibrogenic effects partly through a BM-derived cell population. Notch blockade leaded to increased macrophages and neutrophils. The resolution was delayed in RBP-J knockout mice. And the phagocytosis and expression of MMP2 or MMP13 decreased in RBP-J knockout macrophages. Notch blockade leaded to uncontrolled activation of wound-healing macrophages. MiRNAs were differentially expressed in RBP-J knockout macrophages, and further Notch regulated the expression of MMP2 or MMP13 through miR-188-5p. In vivo experiments showed that LPS induction or miR-188-5p inhibition in macrophages could promote the resolution.