Gene expression profile analysis of the spontaneous reversal of rat hepatic fibrosis by cDNA microarray

Correlation between SDF-1α, CD34 positive hematopoietic stem cells and CXCR4 expression with liver fibrosis in CCl4 rat model

BACKGROUND

One of the most frequent disorders is liver fibrosis. An improved understanding of the different events during the process of liver fibrosis & its reversibility could be helpful in its staging and in finding potential therapeutic agents.

AIM

The goal of this research was to evaluate the relationship among CD34 + HPSCs, SDF-1α, and CXCR4 receptor expression with the percentage of the area of hepatic fibrosis.

MATERIALS AND METHODS

Thirty-six male Sprague-Dawley rats were separated into the control group, liver injury group & spontaneous reversion group. The liver injury was induced by using 2 ml/kg CCl4 twice a week. Flow cytometric examination of CD34 + cells in the blood & liver was performed. Bone marrow & liver samples were taken for evaluation of the SDF-1α mRNA by PCR. Liver specimens were stained for histopathological and CXCR4 immuno-expression evaluation.

RESULTS

In the liver injury group, the hepatic enzymes, fibrosis area percentage, CXCR4 receptor expression in the liver, CD34 + cells in the blood and bone marrow & the level SDF-1α in the liver and its concentration gradient were statistically significantly elevated with the progression of the liver fibrosis. On the contrary, SDF-1α in the bone marrow was statistically significantly reduced with the development of liver fibrosis. During the spontaneous reversion group, all the studied parameters apart from SDF-1α in the bone marrow were statistically substantially decreased compared with the liver injury group. We found a statistically substantial positive correlation between fibrosis area and all of the following: liver enzymes, CXCR4 receptor expression in the liver, CD34 + cells in the blood and liver, and SDF- 1α in the liver and its concentration gradient. In conclusion, in CCl4 rat model, the fibrosis area is significantly correlated with many parameters in the blood, bone marrow, and liver, which can be used during the process of follow-up during the therapeutic interventions.

Inhibition of Notch signaling by a γ-secretase inhibitor attenuates hepatic fibrosis in rats

Notch signaling is essential to the regulation of cell differentiation, and aberrant activation of this pathway is implicated in human fibrotic diseases, such as pulmonary, renal, and peritoneal fibrosis. However, the role of Notch signaling in hepatic fibrosis has not been fully investigated. In the present study, we show Notch signaling to be highly activated in a rat model of liver fibrosis induced by carbon tetrachloride (CCl₄), as indicated by increased expression of Jagged1, Notch3, and Hes1. Blocking Notch signaling activation by a γ-secretase inhibitor, DAPT, significantly attenuated liver fibrosis and decreased the expression of snail, vimentin, and TGF-β1 in association with the enhanced expression of E-cadherin. The study in vitro revealed that DAPT treatment could suppress the EMT process of rat hepatic stellate cell line (HSC-T6). Interestingly, DAPT treatment was found not to affect hepatocyte proliferation in vivo. In contrast, DAPT can inhibit hepatocyte apoptosis to some degree. Our study provides the first evidence that Notch signaling is implicated in hepatic fibrogenesis and DAPT treatment has a protective effect on hepatocytes and ameliorates liver fibrosis. These findings suggest that the inhibition of Notch signaling might present a novel therapeutic approach for hepatic fibrosis.

Evaluation of the Chinese Medicinal Herb, Graptopetalum paraguayense, as a Therapeutic Treatment for Liver Damage in Rat Models

The incidence of cirrhosis is rising due to the widespread occurrence of chronic hepatitis, as well as the evident lack of an established therapy for hepatic fibrosis. In the search for hepatoprotective therapeutic agents, Graptopetalum paraguayense (GP) showed greater cytotoxicity toward hepatic stellate cells than other tested herbal medicines. Histopathological and biochemical analyses suggest that GP treatment significantly prevented DMN-induced hepatic inflammation and fibrosis in rats. Microarray profiling indicated that expression of most of metabolism- and cell growth and/or maintenance-related genes recovered to near normal levels following GP treatment as classified by gene ontology and LSM analysis, was observed. ANOVA showed that expression of 64% of 256 liver damage-related genes recovered significantly after GP treatment. By examining rat liver samples with Q-RT-PCR, five liver damage-related genes were identified. Among them, Egr1 and Nrg1 may serve as necroinflammatory markers, and Btg2 may serve as a fibrosis marker. Oldr1 and Hmgcs1 were up- and down-regulated markers, respectively. A publicly accessible website has been established to provide access to these data Identification of 44 necroinflammation-related and 62 fibrosis-related genes provides useful insight into the molecular mechanisms underlying liver damage and provides potential targets for the rational development of therapeutic drugs such as GP.

Toxicogenomic biomarkers for liver toxicity

Toxicogenomics (TGx) is a widely used technique in the preclinical stage of drug development to investigate the molecular mechanisms of toxicity. A number of candidate TGx biomarkers have now been identified and are utilized for both assessing and predicting toxicities. Further accumulation of novel TGx biomarkers will lead to more efficient, appropriate and cost effective drug risk assessment, reinforcing the paradigm of the conventional toxicology system with a more profound understanding of the molecular mechanisms of drug-induced toxicity. In this paper, we overview some practical strategies as well as obstacles for identifying and utilizing TGx biomarkers based on microarray analysis. Since clinical hepatotoxicity is one of the major causes of drug development attrition, the liver has been the best documented target organ for TGx studies to date, and we therefore focused on information from liver TGx studies. In this review, we summarize the current resources in the literature in regard to TGx studies of the liver, from which toxicologists could extract potential TGx biomarker gene sets for better hepatotoxicity risk assessment.

Inhibition of plasminogen activator inhibitor-1 expression by siRNA in rat hepatic stellate cells

BACKGROUND AND AIM

The plasminogen activator/plasmin system is known to regulate the extracellular matrix turnover. The aim of this study was to detect the role of plasminogen activator inhibitor-1 (PAI-1) during liver fibrogenesis and investigate the functional effects of PAI-1 gene silencing in rat hepatic stellate cells (HSCs) using small interfering RNA (siRNA).

METHODS

Hepatic fibrosis in rats was induced through serial subcutaneously injections of CCl(4) and the expression of PAI-1 was detected by immunohistochemistry and reverse transcription-polymerase chain reaction (PCR). PAI-1 siRNA molecules were constructed and transiently transfected into HSC-T6 using the cell suspension transfection method. The pSUPER RNA interfering system was used to establish the HSC stable cell line pSUPER-shPAI. Expression of alpha-smooth muscle actin, transforming growth factor-beta, tissue inhibitor of metalloproteinases-1, and collagen types I and III were evaluated by real-time PCR. Cell proliferation and the cell cycle were determined by the methyl thiazolyl tetrazolium (MTT) method and flow cytometry. Collagen content in HSCs supernatant was evaluated by enzyme-linked immunosorbent assay.

RESULTS

The results showed that PAI-1 was upregulated during liver fibrosis, and its expression was closely correlated with the deposition of collagens. SiRNA molecules were successfully transfected into HSCs and induced inhibition of PAI-1 expression time dependently. Moreover, PAI-1 siRNA treatment downregulated alpha-smooth muscle actin, transforming growth factor-beta, tissue inhibitor of metalloproteinases-1 expression, and inhibited collagen types I and III synthesis both at the mRNA and protein level in transiently and stably transfected HSCs.

CONCLUSIONS

This study suggests a significant functional role for PAI-1 in the development of liver fibrosis and that downregulating PAI-1 expression might present as a potential strategy to treat liver fibrosis.

Screening of genes associated with human hepatic fibrosis using cDNA microarray

AIM: To screen the genes associated with human hepatic fibrosis and explore the mechanism of hepatic fibrosis.

METHODS: Total mRNA was obtained from human hepatic fibrosis tissues and normal liver tissues respectively to prepare probe. After hybridization and cleaning, computer scan technique was used to analyze the gene expression maps of liver fibrosis tissues and normal liver tissue. Real-time fluorescence quantitative polymerase chain reaction (FQ-PCR) was adopted to verify the expression changes of some differential genes.

RESULTS: Sixty-eight differential genes were screened out, of which 35 were up-regulated and 33 were down-regulated. These genes were categorized according to their functions as cell signal transmission-regulating genes, DNA impairment and repair genes, translation-regulating factors, metabolism-related genes and function-unknown genes. As compared with that in normal liver tissues, C/EBPβ mRNA expression was down-regulated (22.02 ± 4.82 vs 59.13 ± 8.21, P < 0.01), while MMP-14 mRNA expression was up-regulated (257.33 ± 26.58 vs 21.65 ± 4.37, P < 0.01). This conformed to the results of cDNA microarray.

CONCLUSION: Multiple genes are involved in the formation of hepatic fibrosis and there is a significant difference in gene expression between normal and fibrotic liver tissues.