WILMS TUMOR 1 PROMOTES THE BRIDGING FIBROSIS FORMATION THROUGH THE INVASIVE HEPATIC STELLATE CELL INDUCTION IN LIVER FIBROSIS

Background: Chronic cholestatic liver diseases, such as primary sclerosing cholangitis (PSC), often lead to end-stage liver disease requiring liver transplantation. PSC also significantly increases the risk of cholangiocarcinoma (CCA). There is currently no effective therapeutic agent for PSC due to a limited understanding of its pathogenesis. Exosomes carry a variety of bioactive molecules, including miRNAs, lipids and proteins. The dysregulation of miRNAs is closely related to various pathological aspects of PSC. In this study, we aimed to investigate the expression profiles and function of exosomal miRNAs under cholestatic conditions.
Methods: One-year-old Mdr2^-/- mice (FVB background) and age-/gender- matched wild-type (WT) mice were used in this study. The serum exosomes were isolated using qEV isolation system (from IZON). Total RNA was isolated from the serum exosomes and liver tissues using Trizol. Total RNA transcriptome was determined by RNAseq. The miRNA profiles in the exosomes and livers were analyzed using the NanoString nCounter® miRNA Expression panel. TargetScan and mirnet2.0 were used to identify the potential target genes. Protein-protein interaction (PPI) was constructed based on the STRING database. Hub genes under cholestatic conditions were visualized by Cytoscape software. The human CCA patient data were downloaded from the Cancer Genome Atlas (TCGA) database.
Results: Bioinformatic analysis identified 74 differentially expressed miRNAs (DE-miRs) and 137 DE-miRs in the male and female Mdr2^-/- mice compared to corresponding WT controls, respectively. The identified DE-miRs were used to predict the target genes. GO and KEGG analysis further showed that these DE-miRs were linked to multiple signaling pathways related to cholestatic liver injury. We also identified 431 up-, and 1106 down- DE genes (DEGs) in the Mdr2^-/- mice compared to WT mice. From the PPI network analysis of the DEGs, the top 100 hug genes were determined. We identified 11 upregulated DE-miRs in Mdr2^-/- mice, which overlapped with the predicted miRs based on the the top 100 hug genes. Interestingly, among the overlapping DE-miRs, two miRs, miR-16 and let-7e, were also upregulated in the serum exosomes of Mdr2^-/- mice. Among the 100 hug genes, we identified nine downregulated genes that were potential targets of miR-16 and let-7e. Further analysis of TCGA CCA data showed upregulation of miR-16 and let-7e, and 7 out of the 9 identified targeted genes were also significantly downregulated in CCA compared to healthy controls.
Conclusion: This study identified potential DE-miRs in the liver and serum exosomes which may contribute to cholestatic liver injury. This study supports the possible use of exosomal miRs as diagnostic and prognostic markers and therapeutic targets for cholestatic liver diseases.

Background: Following biliary injury/senescence in rodent models of cholestatic liver injury and in patients with PSC, mast cells (MCs) infiltrate the liver and migrate toward cholangiocytes. Proteases such as chymase and tryptase are indicative of MC origination and function, while activated MCs release histamine (HA) that promotes liver inflammation. In human PSC, chymase gene expression is significantly higher than tryptase in these patients. MC chymase induces detrimental effects in cardiac dysfunction, asthma, and lung fibrosis. In vivo, inhibition of chymase reverses acute liver failure and CCl₄-induced damage. Similarly, in a PSC mouse model, Mdr2^-/-, has increased chymase- and tryptase-positive MC presence at baseline, but after treatment with cromolyn sodium (to block MC activation), these mice display reduced biliary damage/senescence, hepatic fibrosis, and inflammation. Aim: To determine the effects of INVA8001, a specific chymase inhibitor, on PSC phenotypes in Mdr2^-/- mice. Methods: 10 wk male Mdr2^-/- mice were treated with INVA8001 (20 mg/kg BW/day) for 14 days by daily IP injection. Serum, liver, cholangiocytes, and cholangiocyte supernatants were collected. FVB/NJ (wild-type, WT) and untreated Mdr2^-/- mice were utilized for comparison. Liver damage was assessed by H&E staining in liver and total bile acids (TBAs) were measured in serum by EIA. Changes in intrahepatic bile duct mass (i.e., ductular reaction, DR) were determined by semiquantitative CK-19 immunohistochemistry (IHC) and biliary senescence by immunofluorescence (IF) for p16 (costained with CK-19) and qPCR for p16, p21, and p18 in total liver mRNA. Hepatic fibrosis and collagen deposition were evaluated by quantitative Fast Green/Sirius Red staining and qPCR for collagen type 1a and TIMP1 in total liver samples. MC presence was determined by staining for mouse MC protease-1 (marks chymase-positive MCs) and tryptase beta 2 (marks tryptase-positive MCs) and activation by HA serum content and qPCR for mMCP-1 and FCeR1 in total liver. Changes in senescence-associated secretory phenotypes (SASPs) were determined by serum TGF-β1 content using EIA and total liver expression by qPCR. Results: Inhibition with INVA8001 ameliorated DR, hepatic damage, senescence/SASP, and fibrosis along with chymase-positive MC infiltration and activation in Mdr2^-/- mice compared to WT and untreated Mdr2^-/- mice. Conclusion: Specific inhibition of chymase targets PSC phenotypes ameliorating pathogenesis by decreased biliary senescence and SASP factors. Our studies demonstrate the damaging effects of chymase-positive MCs in PSC and the therapeutic benefit of INVA8001 treatment with potential applicability to other liver diseases wherein MCs promote pathogenesis.

Fibrosis development is associated with poor prognosis in the patient with chronic liver disease. The formation of bridging fibrosis (BF) is a critical step for developing advanced fibrosis and further cirrhosis. Preventing BF formation could be a strategy for inhibiting further advancement of fibrosis to cirrhosis. For that, underpinning the mechanisms of BF formation is to crucial. We previously showed Wilms tumor 1 (WT1) is a transcriptional regulator of profibrogenic HAS2 in liver fibrosis. Here, we further identified a novel profibrogenic function of WT1 in hepatic stellate cell (HSC) activation and invasion that is associated with BF formation in liver fibrosis.
First, we identified WT1 expression is upregulated in HSCs of BF area in advanced fibrosis in NAFLD patients, which is determined by our new experiment by combining scRNA-seq and spatial transcriptome analysis. Because HSC invasion to liver parenchyma and collagen production is critical for BF formation, we investigated the molecular mechanisms of HSC invasion using a collagen hydrogel invasion model in vitro. We performed RNA-seq for non-invaded HSCs and HSCs during and after invasion by PDGF treatment in vitro. During the invasion, HSCs quickly acquired the capacity to express WT1 and HSCs showed much higher proliferative and fibrogenic phenotype after invasion compared to HSCs without invasion. This invasive, proliferative, and fibrogenic HSC phenotype was inhibited by WT1 deletion. Expectedly, HSC-specific WT1 knockout mice showed reduced HSC invasion and BF development in murine liver fibrosis models induced by bile duct ligation (BDL) and choline-deficient high fat diet (CD-HFD) feeding, concluding WT1 is a potent pro-fibrogenic factor. Then, we investigated the regulatory mechanism of WT1 induction. We found WT1 promoter contains hypoxia inducible factor (HIF) binding site and hypoxic challenge is a strong inducer of WT1 and HSC invasion. Furthermore, our bioinformatics analysis revealed that WT1 is the most enriched transcription factor for hypoxia-induced invasive phenotype in HSCs. As the downstream effectors of WT1, our RNA-seq analysis by comparing wild-type and HSC-specific WT1 knockout mice found PDGFRB and Cathepsin K (CTSK). CTSK is also upregulated by WT1 overexpression in HSCs. Pharmacological inhibition of CTSK inhibited HSC activation in vitro and prevented BF formation in the BDL model. In conclusion, the WT1-CTSK-mediated profibrogenic actions in HSCs are crucial for HSC invasion and BF formation in liver fibrosis. Thus, targeting the WT1-CTSK axis to suppress invasive HSCs could be a novel strategy to prevent BF formation in patient with chronic liver disease.