Identification of transforming growth factors actively transcribed during the progress of liver fibrosis in biliary atresia

Systematic review of the mechanism and assessment of liver fibrosis in biliary atresia

PURPOSE

This study systematically reviewed our team's research on the mechanism and assessment of liver fibrosis in BA, summarized our experience, and discussed the future development direction.

METHODS

In this study, Pubmed and Wanfang databases were searched to collect the literature published by our team on the mechanisms of liver fibrosis in BA and the assessment of liver fibrosis in BA, and the above research results were systematically reviewed.

RESULTS

A total of 58 articles were retrieved. Among the included articles, 25 articles related to the mechanism of liver fibrosis in BA, and five articles evaluated liver fibrosis in BA. This article introduces the key pathways and molecules of liver fibrosis in BA and proposes a new grading system for liver fibrosis in BA.

CONCLUSIONS

The new BA liver fibrosis grading method is expected to assess children's conditions, guide treatment, and improve prognosis more accurately. In addition, we believe that the TGF-β1 signaling pathway is the most important in the study of liver fibrosis in BA, and at the same time, the study of EMT occurrence in BA should also be deepened to resolve the controversy on this issue.

Exosomes from human urine-derived stem cells carry NRF1 to alleviate bladder fibrosis via regulating miR-301b-3p/TGFβR1 pathway

Bladder outlet obstruction (BOO) is a common disease that always make the bladder develops from inflammation to fibrosis. This study was to investigate the effect of exosomes from human urine-derived stem cells (hUSCs) on bladder fibrosis after BOO and the underlying mechanism. The BOO mouse model was established by inserting a transurethral catheter, ligation of periurethral wire, and removal of the catheter. Mouse primary bladder smooth muscle cells (BSMCs) were isolated and treated with TGFβ1 to mimic the bladder fibrosis model in vitro. Exosomes from hUSCs (hUSC-Exos) were injected into the bladder of BOO mice and added into the culture of TGFβ1-induced BSMCs. The associated factors in mouse bladder tissues and BSMCs were detected. It was confirmed that the treatment of hUSC-Exos alleviated mouse bladder fibrosis and down-regulated fibrotic markers (a-SMA and collagen III) in bladder tissues and TGFβ1-induced BSMCs. Overexpression of NRF1 in hUSC-Exos further improved the effects of hUSC-Exos on bladder fibrosis both in vivo and in vitro. TGFβR1 was a target of NRF1 and miR-301b-3p, and miR-301b-3p was a target of NRF1. It was next characterized that hUSC-Exos carried NRF1 to up-regulate miR-301B-3p, thereby reducing TGFβR1level. Our results illustrated that hUSC-Exos carried NRF1 to alleviate bladder fibrosis through regulating miR-301b-3p/TGFβR1 pathway.

Liver secretin receptor predicts portoenterostomy outcomes and liver injury in biliary atresia

Biliary atresia (BA) is a chronic neonatal cholangiopathy characterized by fibroinflammatory bile duct damage. Reliable biomarkers for predicting native liver survival (NLS) following portoenterostomy (PE) surgery are lacking. Herein we explore the utility of 22 preidentified profibrotic molecules closely connected to ductular reaction (DR) and prevailing after successful PE (SPE), in predicting PE outcomes and liver injury. We used qPCR and immunohistochemistry in a BA cohort including liver samples obtained at PE (n = 53) and during postoperative follow-up after SPE (n = 25). Of the 13 genes over-expressed in relation to cholestatic age-matched controls at PE, only secretin receptor (SCTR) expression predicted cumulative 5-year NLS and clearance of jaundice. Patients in the highest SCTR expression tertile showed 34-55% lower NLS than other groups at 1-5 years after PE (P = 0.006-0.04 for each year). SCTR expression was also significantly lower [42 (24-63) vs 75 (39-107) fold, P = 0.015] among those who normalized their serum bilirubin after PE. Liver SCTR expression localized in cholangiocytes and correlated positively with liver fibrosis, DR, and transcriptional markers of fibrosis (ACTA2) and cholangiocytes (KRT7, KRT19) both at PE and after SPE. SCTR is a promising prognostic marker for PE outcomes and associates with liver injury in BA.

Identification of Liver Immune Microenvironment-Related Hub Genes in Liver of Biliary Atresia

Background: Biliary atresia (BA) is one of the most common and fatal abnormalities of newborns. Increasing evidences indicated that immunology was the critical part of the etiology. This research used a public gene expression database to explore the immune microenvironment of BA liver. Methods: The gene expression profiles GSE46960, GSE159720, and GSE15235, containing BA and normal liver gene expression data, were obtained from the Expression Omnibus Gene. We applied CIBERSORTx to quantify 22 subsets of immune cells in BA liver. The differentially expressed genes (DEGs) and immune cells were used to further explore their relationship with liver fibrosis and the inflammation status of BA. Results: The expression of immune-related genes CXCL6, CXCL8, CXCL10, CCL20, IL32, TGFB2, SPP1, and SLIT2 was significantly different between BA and normal liver, among which CXCL8 was the hub gene. Six of 22 immune cell proportions were significantly different between BA and normal liver. Specifically, M0 macrophages and resting memory CD4+ T cells were upregulated in BA liver compared with normal liver. Meanwhile, monocytes, resting natural killer (NK) cells, plasma cells, and regulatory T (Treg) cells were downregulated. A further correlation analysis revealed that SLIT2 and CXCL6 owned high positive correlation coefficients with fibrosis grade, while the proportion of resting NK cells was negatively correlated. Proportions of resting CD4+ memory T cells were strongly related to the inflammation grade of BA liver. Conclusion: Biliary atresia is a disease strongly correlated with immune response. Our results might provide a clue for further exploration of BA etiology, which may promote a potential prediction model based on immune infiltration features.

TGF-β Signaling Plays a Pivotal Role During Developmental Biliary Atresia in Sea Lamprey (Petromyzon marinus)

Biliary atresia (BA) is a rare neonatal disease with unknown causes. Approximately 10% of BA cases develop in utero with other congenital defects that span a large spectrum of disease variations, including degeneration of the gall bladder and bile duct as well as malformation of the liver, intestines, and kidneys. Similar developmental alterations are manifested in a unique animal model, the sea lamprey (Petromyzon marinus), in which BA occurs naturally during metamorphosis. With the likelihood of conserved developmental mechanisms underlying organogenesis and degeneration, lamprey developmental BA may be a useful model to infer mechanisms underlying human embryonic BA. We reasoned that hepatobiliary transcriptomes regulate the transition between landmark stages of BA. Therefore, we examined sea lamprey hepatobiliary transcriptomes at four stages (M0, metamorphic stage 0 or larval stage, no BA; M2, metamorphic stage 2, onset of BA; M5, metamorphic stage 5, BA, and heightened hepatocyte proliferation and reorganization; and JV, juvenile, completion of BA) using messenger RNA sequencing and Kyoto Encyclopedia of Genes and Genomes pathway analyses. We found gene-expression patterns associated with the transition between these stages. In particular, transforming growth factor β (TGF-β), hedgehog, phosphatidylinositol-4,5-bisphosphate 3-kinase-Akt, Wnt, and mitogen-activated protein kinase pathways were involved during biliary degeneration. Furthermore, disrupting the TGF-β signaling pathway with antagonist or small interfering RNA treatments at the onset of BA delayed gall bladder and bile duct degeneration. Conclusion: Distinctive gene-expression patterns are associated with the degeneration of the biliary system during developmental BA. In addition, disrupting TGF-β signaling pathway at the onset of BA delayed biliary degeneration.

Extrahepatic Upregulation of Transforming Growth Factor Beta 2 in HCV Genotype 4-Induced Liver Fibrosis

Elevated levels of transforming growth factor-β (TGF-β) family mediate myofibroblast generation and extracellular matrix deposition, thus making TGF-β recognized as major profibrogenic cytokines. In this article, we provide evidence that extrahepatic TGF-β2 expression at RNA and protein levels in peripheral leucocytes and serum, respectively, correlate with hepatic fibrogenesis. Current study includes a total of 110 subjects [89 naive hepatitis C virus (HCV)-infected patients (f0-f4) and 21 healthy controls]. Array profiling of 84 fibrosis-related transcripts revealed that TGF-β2 RNA was significantly upregulated compared with controls. Transcription results were confirmed by specific qRT-PCR on TGF-β2 RNA in peripheral leucocytes and TGF-β2 protein by ELISA in serum. PCR array and qRT-PCR for TGF-β2 RNA in peripheral leucocytes revealed that HCV-infected patients, regardless of the degree of fibrosis, had significantly elevated TGF-β2 RNA levels compared with controls (P = 0.018 and 0.047, respectively). This extrahepatic upregulation of TGF-β2 RNA was confirmed by elevated levels of secretory TGF-β2 protein in infected sera (P = 0.001). The Area Under the Curve of the receiver operating characteristic curve for the TGF-β2 protein between patients and controls was 0.80, a value that renders serum TGF-β2 protein a promising biomarker for liver fibrosis.

Divergent expression of liver transforming growth factor superfamily cytokines after successful portoenterostomy in biliary atresia

BACKGROUND

Pathogenesis of progressive liver fibrosis in biliary atresia after successful portoenterostomy remains unclear. We related hepatic expression of transforming growth factor beta (TGF-β) superfamily cytokines to histologic liver injury after successful portoenterostomy.

METHODS

Enrolled in our study were 28 patients with biliary atresia who had liver biopsies obtained during and after successful portoenterostomy, which normalized serum bilirubin (<20 µmol/l). Biopsies were evaluated for cholestasis, inflammation, ductal reaction, and fibrosis and were stained immunohistochemically for transforming growth factor beta 1, transforming growth factor beta 2, connective tissue growth factor, and decorin. Respective gene expression (TGFB1, TGFB2, TGFB3, CTGF, DCN) was analyzed at follow-up using quantitative reverse transcription polymerase chain reaction (qRT-PCR). Results were compared with fibrotic and healthy control livers.

RESULTS

After median follow-up of 3.0 years, histologic cholestasis resolved, whereas fibrosis had progressed only in isolated biliary atresia. Liver protein expression of transforming growth factor beta 1 and connective tissue growth factor (P < .001 for both), but not that of transforming growth factor beta 2 or decorin, decreased after successful portoenterostomy, although expression of all four cytokines remained elevated. In accordance with postportoenterostomy changes in protein expression, follow-up ribonucleic acid expression of TGFB2 and DCN, but not that of TGFB1 and CTGF, was upregulated when compared with the controls. Both protein and gene expression of transforming growth factor beta 1 and protein expression of transforming growth factor beta 2, connective tissue growth factor and decorin correlated with METAVIR fibrosis stage. Syndromic patients (n = 12) showed milder fibrosis and lower transforming growth factor beta 1 expression than patients with isolated biliary atresia.

CONCLUSION

These findings support a central role of transforming growth factor beta superfamily in mediating continuing liver fibrogenesis after successful portoenterostomy. Transforming growth factor beta pathway cytokines responded divergently to clearance of jaundice, which was reflected by differential progression of fibrosis between syndromic and isolated patients.

Correlation of Interleukin-33/ST2 Receptor and Liver Fibrosis Progression in Biliary Atresia Patients

Background/Aims: Biliary Atresia (BA) is a devastating pediatric liver disease and characterized by aggressive liver fibrosis progression. The Interleukin-33 (IL-33)/ST2 receptor signaling axis has been demonstrated to be involved in several autoimmune and liver diseases. Since immune dysregulation is a contributor to BA pathogenesis, we aimed to investigate the role of IL-33/ST2 receptor in the progression of liver fibrosis in BA patients. Materials and Methods: The study included 36 BA patients (18 good- and 18 poor-prognosis BA patients); and 8 cholestasis infants as the control group. Patients' information and clinical data were retrospectively collected and compared. Liver fibrosis stage was determined by Masson's trichrome staining. Gene expression levels of IL-33, ST2 receptor, and TFG-β1 were detected by quantitative real-time PCR. MC count, IL-33, TGF-β1, and Interleukin-13 (IL-13) expressions were evaluated by immunohistochemistry. Serum IL-33 expression level was detected by enzyme-linked immunosorbent assay. Co-expression of MC and ST2 receptor was detected by immunofluorescence. In vitro mast cell was cultured with IL-33 stimulation, and ST2 receptor and TGF-β1 expressions were detected. Results: Compared with cholestasis control, BA patients had significantly higher GGT level and Masson score. Expression levels of IL-33, TGF-β1, and IL-13 were significantly increased in BA patients compared to control group, especially in poor-prognosis BA patients. Co-expression of ST2 receptor and MC was found in BA liver tissues. The MC count was markedly higher in BA patients especially in poor-prognosis subgroup. Serum IL-33 level was significantly elevated in poor-prognosis BA patients and related to a higher Masson score. In vitro mast cell culture exhibited significant upregulation of ST2 receptor and TGF-β1 mRNA expression after IL-33 stimulation. Conclusions: IL-33/ST2 receptor signaling axis is correlated with liver fibrosis progression in BA patients, and mast cells participates in this process. These indicate potential prognostic evaluation factors for BA patients and can help in the postoperative management to achieve better long-term prognosis in BA patients.

Association of polymorphism in the VEGFA gene 3'-UTR +936T/C with susceptibility to biliary atresia in a Southern Chinese Han population

BACKGROUND

Biliary atresia (BA) is a neonatal disease characterized by chronic inflammation of the bile ducts and progressive aggravation of jaundice, but with a poor prognosis and high mortality. The etiology of BA is still uncertain which may be related to gene defect, virus infection, immune disorder, gene polymorphism. As a proinflammatory cytokine, VEGFA gene polymorphism (rs3025039) has been shown to be related to the pathogenesis of BA in Taiwanese population.

METHODS

We investigated the association between VEGFA gene polymorphism (rs3025039) and BA susceptibility using the largest case-control cohort, totaling with 506 BA patients and 1473 healthy controls in a Southern Chinese Han population. VEGFA gene polymorphism (rs3025039) was genotyped using the MassARRAY iPLEX Gold system (Sequenom). Odds ratios (OR) and 95% confidence intervals (CIs) were used to access the association between the VEGFA gene polymorphism (rs3025039) and BA risk.

RESULTS

No significant association was found between the VEGFA gene polymorphism (rs3025039) and BA risk in the overall analysis.

CONCLUSION

These results suggest that VEGFA gene polymorphism (rs3025039) may not be associated with the risk of BA in the Southern Chinese Han population.

Liver fibrosis in bile duct-ligated rats correlates with increased hepatic IL-17 and TGF-β2 expression

BACKGROUND AND RATIONALE FOR THE STUDY: IL-17, TGF-β1/2 are cytokines involved in the development of kidney, pulmonary and liver fibrosis. However, their expression kinetics in the pathogenesis of cholestatic liver fibrosis have not yet been fully explored. The aim of the study was to analyze the expression of IL-17, RORγt, NKp46, TGF-β1, and TGF-β2 in the liver of rats with bile duct ligation (BDL).

RESULTS

Hepatic IL-17A gene expression analyzed by qRT-PCR showed a dramatic increase of 350 and 10 fold, at 8 and 30 days post BDL, respectively. TGFβ1 and TGFβ2 gene expression significantly increased throughout the whole fibrotic process. At the protein level in liver homogenates, IL-17, TGF-β1, and RORγt significantly increased at 8 and 30 days after BDL. Interestingly, a significant increase in the protein levels of TGF-β2 and decrease of NKp46 was observed only 30 days after BDL. Unexpectedly, TGF-β2 exhibited stronger signals than TGF-β1 at the gene expression and protein levels. Histological analysis showed bile duct proliferation and collagen deposition.

CONCLUSIONS

Our results suggest that pro-fibrogenic cytokines IL-17, TGF-β1 and, strikingly, TGF-β2 might be important players of liver damage in the pathogenesis of early and advanced experimental cholestatic fibrosis. Th17 cells might represent an important source of IL-17, while NK cell depletion may account for the perpetuation of liver damage in the BDL model.

Integrin β-8, but not β-5 or -6, protein expression is increased in livers of children with biliary atresia

OBJECTIVES

Our previous work demonstrated altered messenger RNA expression of integrin β-5 and -8, using an in silico analysis of publically available data from patients with biliary atresia (BA); however, we were unable to demonstrate statistically significant differences in protein expression because of sample size. In the present study, we repeated the analysis of liver fibrosis and protein expression of the integrins in a larger cohort of patients with BA and compared them with patients undergoing liver biopsy for other diagnoses, with the hypothesis that ≥ 1 of the integrins would be differentially expressed.

METHODS

Liver specimens were obtained at 2 collaborating institutions. Samples from infants with BA (n = 23) were compared with samples from those who underwent liver biopsy for neonatal hepatitis (n = 9). All of the specimens were analyzed by 2 pathologists (C.R. and R.A.), who were blinded to the diagnoses. Standard Ishak scoring was performed to evaluate fibrosis and inflammation, and immunohistochemical (IHC) positivity was graded from 0 to 4. Comparisons between the IHC positivity and Ishak scoring for the BA and control groups were performed using the Student t test with P < 0.01 considered significant because of the multiple comparisons. Interobserver variability was assessed by intraclass correlation (ICC).

RESULTS

Pooled analysis from specimens from patients with BA showed significantly more fibrosis than controls based on Ishak scores (3.21 ± 1.82 vs 1.17 ± 1.00, P < 0.005). IHC evaluation showed increased integrin ανβ8 protein expression when compared with controls (2.67 ± 0.81 vs 1.72 ± 0.62, P < 0.005); however, there were no significant differences in integrin ανβ5 (1.93 ± 0.84 vs 1.50 ± 0.90, P = 0.23) or integrin ανβ6 (0.85 ± 1.20 vs 0.94 ± 0.85, P = 0.82) expression. These data were confirmed on individual analysis. Interobserver agreement was fair for integrin ανβ5 (ICC 0.52), good for integrin ανβ6 (ICC 0.72), and excellent for integrin ανβ8 (ICC 0.79) and fibrosis (ICC 0.89).

CONCLUSIONS

Our data show that integrin ανβ8, but not integrin ανβ5 or integrin ανβ6, protein expression is increased in liver specimens of patients with BA. These data support the mounting evidence that transforming growth factor-β (TGF-β) activation is responsible for the fibrosis found in BA. Anti-integrin ανβ8 or more global integrin blocking strategies may be therapeutic options in BA, but further work is clearly needed.

Participation of miR-200a in TGF-β1-mediated hepatic stellate cell activation

Hepatic stellate cell (HSC) activation is a pivotal event in the initiation and progression of hepatic fibrosis since it mediates transforming growth factor beta 1 (TGF-β1)-driven extracellular matrix (ECM) deposition. MicroRNAs (miRNAs), small non-coding RNAs modulating messenger RNA (mRNA) and protein expression, have emerged as key factors to regulate cell proliferation, differentiation, and apoptosis. Although the function of miR-200a has been discussed in many cancers and fibrotic diseases, its role in hepatic fibrosis is still poorly understood. The aim of this study is to investigate whether miR-200a could attenuate hepatic fibrosis partly through Wnt/β-catenin and TGF-β-dependant mechanisms. Our study found that the expression of endogenous miR-200a was decreased in vitro in TGF-β1-induced HSC activation as well as in vivo in CCl4-induced rat liver fibrosis. Overexpression of miR-200a significantly inhibited α-SMA activity and further affected the proliferation of TGF-β1-dependent activation of HSC. In addition, we identified β-catenin and TGF-β2 as two functional downstream targets for miR-200a. Interestingly, miR-200a specifically suppressed β-catenin in the protein level, whereas miR-200a-mediated suppression of TGF-β2 was shown on both mRNA and protein levels. Our results revealed the critical regulatory role of miR-200a in HSC activation and implied miR-200a as a potential candidate for therapy by deregulation of Wnt/β-catenin and TGFβ signaling pathways, at least in part, via decreasing the expression of β-catenin and TGF-β2.

The role of vitamin d in primary biliary cirrhosis: possible genetic and cell signaling mechanisms

Primary biliary cirrhosis (PBC) is an immune-mediated chronic inflammatory disease of the liver of unknown etiology. Vitamin D deficiency is highly prevalent in patients with PBC, and many studies have demonstrated the significant effect of calcitriol on liver cell physiology. Vitamin D has antiproliferative and antifibrotic effects on liver fibrosis. Genetic studies have provided an opportunity to determine which proteins link vitamin D to PBC pathology (e.g., the major histocompatibility complex class II molecules, the vitamin D receptor, toll-like receptors, apolipoprotein E, Nramp1, and cytotoxic T lymphocyte antigen-4). Vitamin D also exerts its effect on PBC through cell signaling mechanisms, that is, matrix metalloproteinases, prostaglandins, reactive oxygen species, and the transforming growth factor betas. In conclusion, vitamin D may have a beneficial role in the treatment of PBC. The best form of vitamin D for use in the PBC is calcitriol because it is the active form of vitamin D3 metabolite, and its receptors are present in the sinusoidal endothelial cells, Kupffer cells, and stellate cells of normal livers, as well as in the biliary cell line.

Recent progress in understanding pathogenesis and liver pathology in biliary atresia

Biliary atresia is an infantile destructive inflammatory cholangiopathy that causes obliteration of both intrahepatic and extrahepatic bile ducts and eventually liver cirrhosis. So far, the exact etiology and pathogenesis of biliary atresia remain unclear, and possible etiologies include congenital and genetic factors, infection, inflammation, immune reaction, maternal factors, and vascular factors. Immunoinflammatory theory has been accepted by most researchers, which is supported by liver pathological changes. This review focuses on the recent progress in understanding pathogenesis and liver pathology in biliary atresia.

TGF-β1 mediated activation of Rho kinase induces TGF-β2 and endothelin-1 expression in human hepatic stellate cells

BACKGROUND & AIMS

TGF-β1 a key pro-fibrotic factor activates signaling via the canonical ALK/SMAD as well as the Rho GTPase pathways. Rho kinase is a major downstream effector of Rho GTPase signaling. To understand the contribution of Rho kinase activation towards the synthesis of fibrotic mediators by hepatic stellate cells (HSC), we first profiled activated HSC and fibrotic liver tissues to identify common transcripts that were most significantly up-regulated across all samples. We then applied a pharmacologic as well as a genomics approach in a TGF-β1 activated human HSC line (LX-2) to study the involvement of Rho kinase signaling in the expression of a subset of these up-regulated fibrotic genes.

METHODS

Total RNA was profiled using microarray chips. Data analysis was performed using Ingenuity Pathway Analysis software. LX-2 cells were activated with 10 ng/ml of TGF-β1 for 24 h. Activation of downstream pathways was assessed by Western blotting with phospho-specific target biomarker antibodies. Targeted knockdown of Rho kinase isoforms 1 and 2 was achieved with RNAi. Secreted levels of endothelin-1, TGF-β2, and thrombospondin-1 were measured by ELISA.

RESULTS

TGF-β1 activated Rho kinase and Smad pathways in LX-2 cells. The syntheses of endothelin-1 and TGF-β2 were significantly inhibited in TGF-β1 treated LX-2 cells, by isoform non-selective Rho kinase inhibitors. siRNA knockdown of each isoform suggested that endothelin-1 synthesis was largely mediated by the Rho kinase-1 isoform, while both isoforms contributed to the synthesis of TGF-β2.

CONCLUSIONS

The TGF-β1 mediated secretion of endothelin-1 and TGF-β2 is mediated by Rho kinase activation in human HSC.

Serum and tissue transforming [corrected] growth factor β1 in children with biliary atresia

BACKGROUND

Biliary atresia (BA) is an infantile disorder characterized by the obstruction of a portion or the entirety of the extrahepatic bile ducts, leading to hepatic fibrosis and loss of liver function. The gold standard for diagnosing and grading fibrosis is liver biopsy, but there are many groups searching for noninvasive biomarkers that could replace and/or complement this procedure.

METHODS AND MATERIALS

In this study, we evaluated serum and tissue transforming growth factor β1 (TGFβ1) and aspartate aminotransferase [AST]-to-platelet ratio index (APRI) in patients with BA at the time of diagnosis and at liver transplantation and correlated these data with tissue collagen density, to verify if they could act as biomarkers for BA.

RESULTS

At the time of diagnosis, TGFβ1 levels were highly variable in BA patients. However, serum values at transplantation were significantly decreased (13.75 ± 3.68 ng/mL) as compared to controls (34.36 ± 9.35 ng/mL) (P = .01). No correlation was found between serum TGF1β1 and collagen density in both groups analyzed. Serum TGFβ1 showed no correlation with APRI at diagnosis. At the time of liver transplantation, all patients had low serum TGFβ1 and variable APRI, although all higher than 2.0. However, when platelet count was used, an inverse correlation with serum TGFβ1 was observed at the time of diagnostics (r(2) = 0.749; P = .03).

CONCLUSIONS

Our findings suggest that at the time of diagnosis the fibrogenic process is active, with higher levels of TGFβ1, whereas later on, there is scar tissue, with reduced TGFβ1 expression. Although our results should be confirmed in larger sets of patients with BA, the lack of TGFβ1 at the time of liver transplantation may have important consequences for the patient because it is a pleiotropic molecule, responsible for many functions in the body, mainly those related to immune response and cell growth.

Differential expression of hepatic fibrosis mediators in sick and spontaneously recovered mice with experimental biliary atresia

BACKGROUND

Hepatic fibrosis leading to cirrhosis is the major morbidity in patients with biliary atresia (BA). This fibrosis is due to an imbalance in extracellular matrix (ECM) breakdown and deposition. We have previously demonstrated increased mRNA expression for inhibitors of ECM breakdown without increased expression for mediators of ECM deposition in our animal model of BA by d 14. However, only a mild degree of hepatic fibrosis was seen at this time. We hypothesized that expression patterns for these proteins may change once more significant fibrosis had been established, and added resuscitation to the model to improve survival. Interestingly, we found that some mice spontaneously recovered at later time points with resuscitation, and thus compared expression for inhibitors of ECM breakdown and deposition in sick and recovered mice to determine the differences.

METHODS

Newborn Balb/c mice received an intraperitoneal injection 1.0 x 10(6) fluorescence forming units of rhesus rotavirus 24h after birth. Mice were monitored daily for weight gain, development of jaundice, acholic stools, and bilirubinuria. Fifty muL/g of 5% dextrose in normal saline were subcutaneously injected daily to each mouse starting on d 7 until sacrifice. Mice that survived past d 14 were sacrificed at d 21 after saline or RRV infection. Livers were then harvested post-injection d 21 for histologic and immunohistochemical analysis. RNA expression of known mediators of fibrosis was evaluated using quantitative real-time PCR. Protein expression was assessed using ELISA. Weights and normally distributed data were compared using Student's t test. Histologic findings were compared using Fisher's exact test. Comparisons of gene expression and skewed data were performed by the Mann-Whitney U test. Statistical significance was assigned to any P value less than 0.05.

RESULTS

Daily resuscitation resulted in a 35% (24/68) survival rate to d 21 in our model. Mice that recovered were significantly heavier than those that remained ill on d 14 (6.15 +/- 1.16 versus 4.94 +/- 0.82, P = 0.02) and 21 (7.31 +/- 1.41 versus 4.14 +/- 0.53, P < 0.001) despite the fact that there was no difference between the groups with respect to weight on d 7 (4.29 +/- 0.90 versus 3.89 +/- 0.81, P = 0.32). We found that all (10/10) animals that displayed clinical signs of biliary atresia on d 21 had moderate or severe histologic findings, while only one (1/9) of the recovered animals had liver abnormalities at sacrifice (P < 0.001 versus sick group). We also found that the sick mice had statistically significant median fold-increases of mRNA expression for TIMP-1 (31.9 versus 9.1, P = 0.041), TIMP-4 (88.1 versus 1.8, P = 0.022), and MMP-7 (51.8 versus 11.9, P = 0.006) compared with those that recovered. There was a trend toward decreased mRNA expression for PAI-1, which did not reach statistical significance (median 27.7 versus 2.19, P = 0.066). Increased protein expression for TIMP-1 and PAI-1 were also found in the sick group. The mRNA expression for the fibrillar collagens, fibronectin-1, connective tissue growth factor, snail-1, TIMP-2 and -3, and MMP-2 and MMP-9 was not different in the sick and recovered groups 21 d after RRV infection, and was not elevated from baseline gene expression.

CONCLUSIONS

With resuscitation added to the animal model of BA, some mice spontaneously recover while others progress to more significant hepatic fibrosis. Mice with hepatic fibrosis have a continued increase in mRNA expression of TIMP-1, TIMP-4, and MMP-7, with a trend toward increased mRNA expression of PAI-1 on d 21. Protein levels for TIMP-1 and PAI-1 were also increased in the sick mice. Recovered mice display mild to no hepatic parenchymal disease and a normal pattern of mRNA expression for the mediators of fibrosis tested. No increase in mRNA expression for the mediators of ECM deposition was found in either group. These data further support the notion that inhibition of ECM breakdown alone is sufficient to induce hepatic fibrosis. Modulation of this process may be a putative target for preventing liver injury in patients with BA.

Hepatitis C virus core protein triggers hepatic angiogenesis by a mechanism including multiple pathways

Chronic hepatitis C virus (HCV) infection is associated with the production of serum cytokines, including transforming growth factor (TGF)-beta2. Despite the occurrence of hepatic angiogenesis in liver conditions, the role of HCV proteins in this context is currently unknown. We demonstrated that the development of hepatic neoangiogenesis in patients infected with HCV is associated with the expression of TGF-beta2 and vascular endothelial growth factor (VEGF) and with activation of endothelial cells, as evidenced by CD34 expression. The analysis of liver biopsies of HCV-positive and HCV-negative patients using immunostaining showed significant elevation of TGF-beta2, VEGF, and CD34 expression in patients who were HCV-positive. Using an HCV established culture system, we confirmed further the production of both TGF-beta2 and VEGF proteins, in the hepatoma cell lines HepG2 and Huh7 by transfection with full-length HCV RNA (JFH1) or by the regulated expression of core. In addition, regulated expression of core protein in HepG2 or Huh7 cells was found to induce expression and activation of the transcription factor E2F1 and apoptosis signal-regulating kinase 1 (ASK1), activation of c-jun-N-terminal kinase (JNK) and p38, and extracellular-regulated kinase (ERK), and transcription factors activator protein 1 (AP-1), activating transcription factor 2 (ATF-2), cyclic adenosine monophosphate response element binding (CREB), E2F1, hypoxia inducing factor 1 alpha (HIF-1alpha), and specificity protein 1. Furthermore, data obtained from inhibitor experiments revealed the importance of E2F1 and ASK1 in the modulation of core-induced activation of JNK and p38 pathways and suggested an essential role for JNK, p38, and ERK pathways in the regulation of core-induced production of TGF-beta2 and VEGF proteins. Thus, our data provide insight into the molecular mechanisms whereby core protein mediates the development of hepatic angiogenesis in patients with chronic HCV infection.

Effect of selective cyclooxygenase-2 inhibitor meloxicam on liver fibrosis in rats with ligated common bile ducts

AIM

Cholestasis triggers fibrogenesis in the liver. Hepatic cyclooxygenase-2 (COX-2) expression increases in various chronic liver diseases caused either by viruses or toxins. We hypothesized that selective COX-2 inhibitor meloxicam could suppress inflammation and fibrogenesis in a rat model of cholestasis induced by bile duct ligation (BDL).

METHODS

Forty-three Sprague-Dawley rats were assigned to one of four treatment groups (sham-operation, BDL, daily meloxicam injections following BDL, and daily meloxicam injection without BDL). Liver histopathology was analyzed with hematoxylin-eosin and Masson's trichrome staining. The expression of alpha-smooth muscle actin (alpha-SMA), transforming growth factor-beta1 (TGF-beta1), and COX-2 were measured with immunohistochemical staining. The levels of COX-2, TGF-beta1, and matrix metalloproteinase-9 (MMP-9) production were measured with the Western blot method and an enzyme immunoassay.

RESULTS

Meloxicam treatment attenuated the expression of alpha-SMA, TGF-beta1, and COX-2 in rats that were treated with BDL for 3 weeks. This was associated with a marked reduction in collagen accumulation and histological improvement. In addition, meloxicam treatment was found to downregulate the levels of hepatic COX-2, TGF-beta1, and MMP-9 production.

CONCLUSION

Cholestasis in BDL rats induces hepatic COX-2 expression. Selective COX-2 inhibitor meloxicam reduces BDL-induced hepatic fibrosis, and this is associated with reduced hepatic TGF-beta1 expression as well as decreased cyclooxygenase activity in the liver.

Integrin alphavbeta6 and mediators of extracellular matrix deposition are up-regulated in experimental biliary atresia

INTRODUCTION

Biliary atresia (BA) is a progressive obliteration of the extrahepatic bile ducts resulting in hepatic fibrosis. The underlying mechanisms have not been defined. We used an animal model of BA to evaluate mediators of extracellular matrix (ECM) processing to determine which factors may be involved.

METHODS

Newborn BALB/c mice received an intraperitoneal injection with rhesus rotavirus or saline within 24 h of birth. Livers were harvested on days 7 and 14 for histology and immunohistochemistry (IHC). RNA expression was determined using quantitative real-time PCR. Human liver from patients with BA and those having a resection for nonfibrosing diseases was also evaluated.

RESULTS

In experimental mice, mRNA expression for tissue inhibitor of metalloproteinase (TIMP)-1 and matrix metalloproteinase (MMP)-7 was increased 18-fold and 69-fold, respectively on day 7, with further increases on day 14. On day 14, mRNA expression for plasminogen activator inhibitor (PAI)-1 (38-fold), TIMP-4 (9.5-fold), and MMP-9 (5.5-fold) mRNA was also observed. Furthermore, integrin alpha(v) beta(6) mRNA expression was increased on days 7 (11-fold) and 14 (6-fold). Presence of integrin alpha(v) beta(6) protein was confirmed by IHC in both mouse and human specimens in the proliferating biliary epithelium.

CONCLUSIONS

Our data suggest experimental BA is associated with increased mRNA expression of ECM degradation inhibitors, TIMP-1, PAI-1, and TIMP-4. MMP-7 and MMP-9 expression is also elevated in this model. Furthermore, increased gene expression of integrin alpha(v)beta(6) was demonstrated and IHC confirmed protein expression. Integrin alpha(v)beta(6) or the inhibitors of ECM breakdown may be attractive targets for future treatment strategies.

Evidence for the epithelial to mesenchymal transition in biliary atresia fibrosis

The epithelial to mesenchymal transition has recently been implicated as a source of fibrogenic myofibroblasts in organ fibrosis, particularly in the kidney. There is as yet minimal evidence for the epithelial to mesenchymal transition in the liver. We hypothesized that this process in biliary epithelial cells plays an important role in biliary fibrosis and might be found in patients with especially rapid forms, such as is seen in biliary atresia. We therefore obtained liver tissue from patients with biliary atresia as well as a variety of other pediatric and adult liver diseases. Tissues were immunostained with antibodies against the biliary epithelial cell marker CK19 as well as with antibodies against proteins characteristically expressed by cells undergoing the epithelial to mesenchymal transition, including fibroblast-specific protein 1, the collagen chaperone heat shock protein 47, the intermediate filament protein vimentin, and the transcription factor Snail. The degree of colocalization was quantified using a multispectral imaging system. We observed significant colocalization between CK19 and other markers of the epithelial to mesenchymal transition in biliary atresia as well as other liver diseases associated with significant bile ductular proliferation, including primary biliary cirrhosis. There was minimal colocalization seen in healthy adult and pediatric livers, or in livers not also demonstrating bile ductular proliferation. Multispectral imaging confirmed significant colocalization of the different markers in biliary atresia. In conclusion, we present significant histologic evidence suggesting that the epithelial to mesenchymal transition occurs in human liver fibrosis, particularly in diseases such as biliary atresia and primary biliary cirrhosis with prominent bile ductular proliferation.

Evaluation of matrix metalloproteinases and their endogenous tissue inhibitors in biliary atresia-associated liver fibrosis

BACKGROUND/PURPOSE

Matrix metalloproteinases (MMPs) and their endogenous tissue inhibitors (TIMPs) are major proteases responsible for remodeling the liver tissue, but their roles in biliary atresia (BA)--associated liver fibrosis are not clear.

METHODS

A DNA microarray containing complementary DNA clones of 10 MMPs and 4 TIMPs was used to compare the expression profiles of the liver cytokines among 3 patients with BA at the time of Kasai procedure (KP) with 3 at the time of liver transplantation (LT). Liver samples from 2 children without liver fibrosis were used as normal controls. Those genes that were differentially expressed by more than 2-fold between groups were further quantified with real time quantitative reverse transcription-polymerase chain reaction (QRT-PCR) and validated with gel electrophoresis.

RESULTS

In normal human liver, messenger RNAs (mRNAs) of TIMP-1, -2, and -3, but not of TIMP-4 and none of the 10 MMPs studied, were expressed in DNA microarray. With progression of liver fibrosis, only mRNA of MMP-7, but not other MMPs, was induced to express at a significantly higher level in the array. Despite its low level of expression, MMP-9 mRNA was significantly upregulated in KP but downregulated in LT, whereas MMP-2, which was not showed in the array, was significantly upregulated in LT than in KP and control in real time QRT-PCR. There was a more than 2-fold increase in TIMP-1 and TIMP-2 mRNA expression in LT over control in the array, which was confirmed in subsequent real time QRT-PCR. The expression of TIMP-3 mRNA was significantly downregulated in KP than in control.

CONCLUSIONS

This study verified differential expression of MMPs and TIMPs in different stages of BA, with emphasis on the role of TIMP-1, -2, and -3 as well as MMP-2, -7, and -9 transcripts in remodeling of liver tissue during the progress of BA-associated liver fibrosis.