Osteopontin is involved in the formation of epithelioid granuloma and bile duct injury in primary biliary cirrhosis

Primary biliary cholangitis has causal effects on systemic rheumatic diseases: a Mendelian randomization study

BACKGROUND

An association has been observed between primary biliary cholangitis (PBC) and systemic rheumatic diseases (SRDs) in observational studies, however the exact causal link remains unclear. We aimed to evaluate the causal effects of PBC on SRDs through Mendelian randomization (MR) analysis.

METHODS

The genome-wide association study (GWAS) summary data were obtained from MRC IEU OpenGWAS and FinnGen databases. Independent genetic variants for PBC were selected as instrumental variables. Inverse variance weighted was used as the main approach to evaluate the causal effects of PBC on Sjögren syndrome (SS), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic sclerosis (SSc), mixed connective tissue disease (MCTD) and polymyositis (PM). Horizontal pleiotropy and heterogeneity were measured by MR‒Egger intercept test and Cochran's Q value, respectively.

RESULTS

PBC had causal effects on SS (OR = 1.177, P = 8.02e-09), RA (OR = 1.071, P = 9.80e-04), SLE (OR = 1.447, P = 1.04e-09), SSc (OR = 1.399, P = 2.52e-04), MCTD (OR = 1.306, P = 4.92e-14), and PM (OR = 1.416, P = 1.16e-04). Based on the MR‒Egger intercept tests, horizontal pleiotropy was absent (all P values > 0.05). The robustness of our results was further enhanced by the leave-one-out method.

CONCLUSIONS

Our research has provided new insights into PBC and SRDs, indicating casual effects on various SRDs.

Causal associations between systemic lupus erythematosus and primary biliary cholangitis: A bidirectional Mendelian randomization study

Objectives

The association between systemic lupus erythematosus (SLE) and primary biliary cholangitis (PBC) has been increasingly recognized. However, the existence of causal connections between SLE and PBC has yet to be established. In this study, we aimed to investigate the bidirectional causation between SLE and PBC utilizing Mendelian randomization (MR) analysis.

Methods

We acquired summary data from Genome-wide association studies (GWAS) for SLE and PBC from the IEU Open GWAS and FinnGen database. The inverse variance weighted (IVW) was employed as the key method to ascertain the causality between SLE and PBC. Subsequently, a range of sensitivity analyses were applied. We also performed a fixed-effects model meta-analysis to combine the MR results from different databases. Moreover, multivariable MR were conducted to clarify the roles of potential confounding factors.

Results

Our univariable MR investigation provided compelling evidence supporting a causal relationship between SLE and PBC in both directions. Specifically, the IVW method demonstrated a strong casual effect of SLE on PBC (odds ratio (OR) = 1.17, 95 % confidence interval (CI) = 1.09-1.25, p < 0.001). In addition, the results of reverse MR analysis revealed that genetically predicted PBC was associated with an increased risk of SLE (OR = 1.39, 95 % CI = 1.32-1.45, p < 0.001). The sensitivity analyses indicated the absence of horizontal pleiotropy and heterogeneity. Furthermore, the causality between SLE and PBC remained significant even after adjusting for common risk factors in the multivariable MR analysis.

Conclusions

Our study provides statistical evidence of a potential causal relationship between SLE and PBC, but further research is needed to the explore of the underlying mechanisms of these disorders.

Targeting osteopontin to treat primary sclerosing cholangitis

PURPOSE OF REVIEW

Primary sclerosing cholangitis is a chronic cholestatic liver disease for which no pharmacological treatment options are available. It is an immune-mediated disease and macrophages have been implicated in disease pathogenesis. However, which specific macrophage populations contribute to disease, and how we can apply this as therapeutic strategy is still unclear.

RECENT FINDINGS

Recent studies have shown that fibrous tissue is characterized by osteopontin-positive macrophages, including in patients with primary sclerosing cholangitis. Experimental models indicate that intracellular osteopontin in macrophages confers protection, while secreted osteopontin contributes to disease. Serum osteopontin is increased in different liver diseases, including primary sclerosing cholangitis, and might thus serve as therapeutic target.

SUMMARY

Although several studies report on the role of osteopontin in liver disease, only a minority of the studies have focused on isoform-specific functions, and the importance of the cellular source of secreted osteopontin. Future studies investigating these aspects, and how this can be translated to therapies for primary sclerosing cholangitis, and other chronic liver diseases, are required.

Osteopontin Takes Center Stage in Chronic Liver Disease

Osteopontin (OPN) was first identified in 1986. The prefix osteo- means bone; however, OPN is expressed in other tissues, including liver. The suffix -pontin means bridge and denotes the role of OPN as a link protein within the extracellular matrix. While OPN has well-established physiological roles, multiple "omics" analyses suggest that it is also involved in chronic liver disease. In this review, we provide a summary of the OPN gene and protein structure and regulation. We outline the current knowledge on how OPN is involved in hepatic steatosis in the context of alcoholic liver disease and non-alcoholic fatty liver disease. We describe the mechanisms whereby OPN participates in inflammation and liver fibrosis and discuss current research on its role in hepatocellular carcinoma and cholangiopathies. To conclude, we highlight important points to consider when doing research on OPN and provide direction for making progress on how OPN contributes to chronic liver disease.

Liver Matrix in Benign and Malignant Biliary Tract Disease

The extracellular matrix is a highly reactive scaffold formed by a wide array of multifunctional molecules, encompassing collagens and noncollagenous glycoproteins, proteoglycans, glycosaminoglycans, and polysaccharides. Besides outlining the tissue borders, the extracellular matrix profoundly regulates the behavior of resident cells by transducing mechanical signals, and by integrating multiple cues derived from the microenvironment. Evidence is mounting that changes in the biostructure of the extracellular matrix are instrumental for biliary repair. Following biliary damage and eventually, malignant transformation, the extracellular matrix undergoes several quantitative and qualitative modifications, which direct interactions among hepatic progenitor cells, reactive ductular cells, activated myofibroblasts and macrophages, to generate the ductular reaction. Herein, we will give an overview of the main molecular factors contributing to extracellular matrix remodeling in cholangiopathies. Then, we will discuss the structural alterations in terms of biochemical composition and physical stiffness featuring the "desmoplastic matrix" of cholangiocarcinoma along with their pro-oncogenic effects.

The Role of Monocytes and Macrophages in Autoimmune Diseases: A Comprehensive Review

Monocytes (Mo) and macrophages (Mϕ) are key components of the innate immune system and are involved in regulation of the initiation, development, and resolution of many inflammatory disorders. In addition, these cells also play important immunoregulatory and tissue-repairing roles to decrease immune reactions and promote tissue regeneration. Several lines of evidence have suggested a causal link between the presence or activation of these cells and the development of autoimmune diseases. In addition, Mo or Mϕ infiltration in diseased tissues is a hallmark of several autoimmune diseases. However, the detailed contributions of these cells, whether they actually initiate disease or perpetuate disease progression, and whether their phenotype and functional alteration are merely epiphenomena are still unclear in many autoimmune diseases. Additionally, little is known about their heterogeneous populations in different autoimmune diseases. Elucidating the relevance of Mo and Mϕ in autoimmune diseases and the associated mechanisms could lead to the identification of more effective therapeutic strategies in the future.

Is Osteopontin a Friend or Foe of Cell Apoptosis in Inflammatory Gastrointestinal and Liver Diseases?

Osteopontin (OPN) is involved in a variety of biological processes, including bone remodeling, innate immunity, acute and chronic inflammation, and cancer. The expression of OPN occurs in various tissues and cells, including intestinal epithelial cells and immune cells such as macrophages, dendritic cells, and T lymphocytes. OPN plays an important role in the efficient development of T helper 1 immune responses and cell survival by inhibiting apoptosis. The association of OPN with apoptosis has been investigated. In this review, we described the role of OPN in inflammatory gastrointestinal and liver diseases, focusing on the association of OPN with apoptosis. OPN changes its association with apoptosis depending on the type of disease and the phase of disease activity, acting as a promoter or a suppressor of inflammation and inflammatory carcinogenesis. It is essential that the roles of OPN in those diseases are elucidated, and treatments based on its mechanism are developed.

Autoimmune gastrointestinal complications in patients with systemic lupus erythematosus: case series and literature review

The association of systemic lupus erythematosus (SLE) with gastrointestinal autoimmune diseases is rare, but has been described in the literature, mostly as case reports. However, some of these diseases may be very severe, thus a correct and early diagnosis with appropriate management are fundamental. We have analysed our data from the SLE patient cohort at University College Hospital London, established in 1978, identifying those patients with an associated autoimmune gastrointestinal disease. We have also undertaken a review of the literature describing the major autoimmune gastrointestinal pathologies which may be coincident with SLE, focusing on the incidence, clinical and laboratory (particularly antibody) findings, common aetiopathogenesis and complications.

Clinical Characteristics of Concomitant Systemic Lupus Erythematosus and Primary Biliary Cirrhosis: A Literature Review

Although autoimmune diseases often coexist, concomitant cases of systemic lupus erythematosus (SLE) and primary biliary cirrhosis (PBC) are uncommon. In this review paper, 34 cases of SLE with concomitant PBC found in English and Japanese scientific literature and Japanese proceedings were reviewed and summarized, including cases with liver dysfunction complicated by SLE. Of the 34 reported concomitant cases of SLE and PBC, 97.1% (33/34) were females, and PBC was diagnosed initially in 69.0% (20/29), except for five cases in which both SLE and PBC were simultaneously diagnosed. Sjögren's syndrome was the most common autoimmune disease complicating concomitant SLE and PBC (23.5%, 8/34). Five deaths have been reported: two elderly patients died of liver failure because of the worsening of PBC, and another two patients died from pulmonary infection associated with SLE pharmacotherapy. It is uncertain whether concomitant cases occur by chance or share a common immunological or genetic basis.

Challenge of liver disease in systemic lupus erythematosus: Clues for diagnosis and hints for pathogenesis

Systemic lupus erythematosus (SLE) encompass a broad spectrum of liver diseases. We propose here to classify them as follows: (1) immunological comorbilities (overlap syndromes); (2) non-immunological comorbilities associated to SLE; and (3) a putative liver damage induced by SLE itself, referred to as "lupus hepatitis". In the first group, liver injury can be ascribed to overlapping hepatopathies triggered by autoimmune mechanisms other than SLE occurring with higher incidence in the context of lupus (e.g., autoimmune hepatitis, primary biliary cirrhosis). The second group includes non-autoimmune liver diseases, such as esteatosis, hepatitis C, hypercoagulation state-related liver lesions, hyperplasic parenchymal and vascular lesions, porphyria cutanea tarda, and drug-induced hepatotoxicity. Finally, the data in the literature to support the existence of a hepatic disease produced by SLE itself, or the occurrence of a SLE-associated prone condition that increases susceptibility to acquire other liver diseases, is critically discussed. The pathological mechanisms underlying each of these liver disorders are also reviewed. Despite the high heterogeneity in the literature regarding the prevalence of SLE-associated liver diseases and, in most cases, lack of histopathological evidence or clinical studies large enough to support their existence, it is becoming increasingly apparent that liver is an important target of SLE. Consequently, biochemical liver tests should be routinely carried out in SLE patients to discard liver disorders, particularly in those patients chronically exposed to potentially hepatotoxic drugs. Diagnosing liver disease in SLE patients is always challenging, and the systematization of the current information carried out in this review is expected to be of help both to attain a better understanding of pathogenesis and to build an appropriate work-up for diagnosis.

Osteopontin Expression in Patients with Hepatolith

To investigate the role of osteopontin (OPN) in the formation of hepatolith, we have immunohistochemically studied the involvement of OPN in hepatolithiasis in the intrahepatic bile ducts and the intramural and extramural glands, and in stones. In our hospital, 17 hepatic resections for hepatolithiasis were carried out from June 2006 to October 2009. Immunohistochemistry was performed on 17 liver specimens with hepatolith and on 24 control liver specimens without hepatolith. We compared the osetopontin expression in the epithelia of the intrahepatic bile ducts and peribiliary glands or periglandular macrophages. Staining for OPN was positive in the cytoplasm of the epithelial cells of stone-containing intrahepatic bile ducts and the intramural and extramural glands, and in stones. But there were no significant differences between the hepatolithiasis group and the control group for the OPN immunoreactivity of the luminal surface of the epithelial cells of the intrahepatic bile ducts and intramural and extramural glands. The stone-containing intrahepatic bile ducts were infiltrated by macrophages that showed intense staining for OPN. The core and matrix of the stones showed OPN immunoreactivity. The degree of OPN from the cytoplasm of the epithelia of the intrahepatic bile ducts and peribiliary glands or periglandular macrophages was different between hepatolithiasis and control groups. Our result suggests that the OPN from the intrahepatic bile ducts and peribiliary glands plays a role in the formation of intrahepatic stone.

Late-onset systemic lupus erythematosus-associated primary biliary cirrhosis

Background

The development of Primary Biliary Cirrhosis (PBC) during the course of Systemic Lupus Erythematosus (SLE) is extremely rare. We report the case of a geriatric woman who was diagnosed with SLE at 69 years of age then with primary biliary cirrhosis one year later.

Case presentation

A 70-years-old woman, who had been diagnosed with SLE at 69 years, was admitted for further examination of liver dysfunction. PBC was confirmed based on elevated serum levels of transaminase, high levels of antimitochondrial antibodies and following a liver biopsy. The oral administration of ursodeoxycholic acid stabilized the liver dysfunction.

Conclusion

We described an original case report of elderly patient with coexisting PBC and SLE. To date, according to the best of our knowledge, there have been few case reports of SLE/PBC co-occurrence. The aetiology of this complex remains unknown, autoimmune mechanisms, environmental and genetic factors are considered important in the susceptibility to both diseases. Osteopontin might play an important role.

Serum osteopontin levels as a predictor of portal inflammation in patients with nonalcoholic fatty liver disease

BACKGROUND

Osteopontin is a secreted phosphorylated glycoprotein that is expressed by a variety of cell types and that mediates numerous and diverse biological functions. Osteopontin knockout mice are protected from obesity-induced hepatic steatosis. In the present study, we sought to investigate whether serum osteopontin concentrations are associated with liver histology in patients with nonalcoholic fatty liver disease.

METHODS

Serum levels of osteopontin were measured by enzyme-linked immunosorbent assay in 179 well-characterized patients with nonalcoholic fatty liver referred for liver histology and 123 control subjects.

RESULTS

Serum osteopontin levels were markedly higher in patients with nonalcoholic fatty liver disease than in controls (p<0.001). Multivariable analysis showed that osteopontin levels were strongly and independently associated with both portal inflammation (β=0.294, p<0.01) and serum aminotransferase levels (aspartate aminotransferase: β=0.295, p<0.01; alanine aminotransferase; β=0.285, p<0.01).

CONCLUSION

In summary, these data demonstrate that serum levels of osteopontin are elevated in nonalcoholic fatty liver disease and are a significant independent predictor of portal inflammation in this clinical entity.

Osteopontin is a novel downstream target of SOX9 with diagnostic implications for progression of liver fibrosis in humans

Osteopontin (OPN) is an important component of the extracellular matrix (ECM), which promotes liver fibrosis and has been described as a biomarker for its severity. Previously, we have demonstrated that Sex-determining region Y-box 9 (SOX9) is ectopically expressed during activation of hepatic stellate cells (HSC) when it is responsible for the production of type 1 collagen, which causes scar formation in liver fibrosis. Here, we demonstrate that SOX9 regulates OPN. During normal development and in the mature liver, SOX9 and OPN are coexpressed in the biliary duct. In rodent and human models of fibrosis, both proteins were increased and colocalized to fibrotic regions in vivo and in culture-activated HSCs. SOX9 bound a conserved upstream region of the OPN gene, and abrogation of Sox9 in HSCs significantly decreased OPN production. Hedgehog (Hh) signaling has previously been shown to regulate OPN expression directly by glioblastoma (GLI) 1. Our data indicate that in models of liver fibrosis, Hh signaling more likely acts through SOX9 to modulate OPN. In contrast to Gli2 and Gli3, Gli1 is sparse in HSCs and is not increased upon activation. Furthermore, reduction of GLI2, but not GLI3, decreased the expression of both SOX9 and OPN, whereas overexpressing SOX9 or constitutively active GLI2 could rescue the antagonistic effects of cyclopamine on OPN expression.

CONCLUSION

These data reinforce SOX9, downstream of Hh signaling, as a core factor mediating the expression of ECM components involved in liver fibrosis. Understanding the role and regulation of SOX9 during liver fibrosis will provide insight into its potential modulation as an antifibrotic therapy or as a means of identifying potential ECM targets, similar to OPN, as biomarkers of fibrosis.

Mechanisms of disease progression in NASH: new paradigms

The incidence of nonalcoholic fatty liver disease is increasing at an astonishing rate in the US population. Although only a small proportion of these patients develop steatohepatitis (NASH), those who do have a greater likelihood of developing end-stage liver disease and complications. Research on liver fibrosis and NASH progression shows that hedgehog (Hh) is reactivated after liver injury to assist in liver repair and regeneration. When the process of tissue repair and regeneration is prolonged or when Hh ligand and related genes are aberrantly regulated and excessive, tissue repair goes awry and NASH progresses to cirrhosis and hepatocellular carcinoma.

Osteopontin upregulation in rotavirus-induced murine biliary atresia requires replicating virus but is not necessary for development of biliary atresia

Biliary atresia (BA) is a progressive fibro-inflammatory pediatric liver disease in which osteopontin (OPN), a glycoprotein with inflammatory and fibrogenic activity, may play a pathogenic role. The current studies were conducted in a mouse model of rotavirus-induced BA to test the hypotheses that live but not inactivated rotavirus causes antigenemia, upregulation of hepatic OPN expression, and induction of BA and fibrosis; and that OPN is necessary for development of BA. Prolonged or transient antigenemia developed in mice inoculated with live or inactivated virus, respectively, but only live virus upregulated hepatic OPN and caused BA and fibrosis. OPN was expressed in intra- and extrahepatic bile ducts in healthy mice and in mice with BA. OPN-deficient mice, similar to WT mice, developed BA. Together, these data show that live but not inactivated rotavirus causes upregulation of hepatic OPN expression and BA but that OPN is not necessary for development of BA.

Osteopontin in macrophage function

The secreted phosphorylated protein osteopontin (OPN) is expressed in a variety of tissues and bodily fluids, and is associated with pathologies including tissue injury, infection, autoimmune disease and cancer. Macrophages are ubiquitous, heterogeneous cells that mediate aspects of cell and tissue damage in all these pathologies. Here, the role of OPN in macrophage function is reviewed. OPN is expressed in macrophage cells in multiple pathologies, and the regulation of its expression in these cells has been described in vitro. The protein has been implicated in multiple functions of macrophages, including cytokine expression, expression of inducible nitric oxide synthase, phagocytosis and migration. Indeed, the role of OPN in cells of the macrophage lineage might underlie its physiological role in many pathologies. However, there are numerous instances where the published literature is inconsistent, especially in terms of OPN function in vitro. Although the heterogeneity of OPN and its receptors, or of macrophages themselves, might underlie some of these inconsistencies, it is important to understand the role of OPN in macrophage biology in order to exploit its function therapeutically.

A case of primary biliary cirrhosis which developed eight years after diagnosis of systemic lupus erythematosus

A 29-year-old Japanese female was diagnosed with systemic lupus erythematosus (SLE) at the age of 21 and went into remission after administration of prednisolone. Although no liver dysfunction had been observed upon diagnosis of SLE or during follow-up, an increase of hepatobiliary enzyme levels was seen eight years after the diagnosis of SLE. Antimitochondrial antibodies were positive. Cell infiltration around intrahepatic bile ducts and granuloma formation were observed in the liver. Therefore, she was diagnosed with primary biliary cirrhosis (PBC). Administration of ursodeoxycholic acid resulted in normalization of hepatobiliary enzyme levels. Development of PBC after SLE is extremely rare.

The role of osteopontin and tumor necrosis factor alpha receptor-1 in xenobiotic-induced cholangitis and biliary fibrosis in mice

Proinflammatory and profibrotic cytokines such as osteopontin (OPN) and tumor necrosis factor-alpha receptor-1 (TNFR(1)) may be critically involved in the pathogenesis of cholangiopathies and biliary fibrosis. We therefore aimed to determine the role of genetic loss of either OPN or TNFR(1) in 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-fed mice as a model of xenobiotic-induced sclerosing cholangitis with biliary-type liver fibrosis using respective knock-out mice. OPN and TNFR(1) knock-out mice were fed a 0.1% DDC-supplemented diet for 4 weeks and compared with corresponding wild-type (WT) controls. Liver morphology (H&E staining), serum markers of liver injury and cholestasis (ALT, AP, bilirubin), markers of inflammation in liver (CD11b and F4/80 immunostaining, mRNA expression of iNOS, MCP-1, IL-1beta, INF-gamma, TNF-alpha and OPN), degree of ductular reaction (immunohistochemistry with morphometric analysis and western blotting for cholangiocyte-specific marker keratin 19) and degree of liver fibrosis (Sirius-red staining, hepatic hydroxyproline content for quantification) were compared between groups. DDC feeding in OPN and TNFR(1) knock-out mice and respective WT controls resulted in comparable extent of liver injury, inflammatory response, ductular reaction and liver fibrosis. Our data indicate that genetic loss of neither OPN nor TNFR(1) significantly effects on the pathogenesis of DDC-induced sclerosing cholangitis, ductular reaction and resulting biliary fibrosis.

An immunohistochemical study of osteopontin in hepatolithiasis

BACKGROUND/PURPOSE

Mucin glycoprotein from the intrahepatic bile ducts, and from the intramural and extramural glandular epithelia, is thought to contribute to the formation of the matrix, or nucleus, in hepatolithiasis and to contribute to biomineralization systems. Osteopontin (OPN), a noncollagenous acidic bone matrix glycoprotein that possesses calcium-binding properties. To investigate the role of OPN in the genesis of hepatolithiasis, OPN was immunohistochemically studied in the intrahepatic bile ducts, intramural and extramural glands, and in stones.

METHODS

An immunohistochemical study was performed in 21 human liver specimens with hepatolithiasis, by the EnVision (Dako Japan, Kyoto, Japan) method.

RESULTS

Staining for OPN was strongly positive in the epithelium of stone-laden intrahepatic bile ducts, intramural and extramural glands, and in stones. The stone-laden intrahepatic bile ducts were infiltrated by macrophages showing intense staining for OPN. Sections of the hepatolithiasis, viewed under low magnification, showed a lamellar pattern of OPN immunolabeling, and they showed a reticular pattern under high magnification. In the center of the stones, large nestlike membranous structures were frequently present.

CONCLUSIONS

Our result indicates that OPN, an acidic glycoprotein from intrahepatic bile ducts and from intramural and extramural glandular epithelia, seems to be involved in lithiasis, both as a core protein in the early phase, and in the late phase.

Osteopontin expression in the liver with severe perisinusoidal fibrosis: autopsy case of Down syndrome with transient myeloproliferative disorder

Down syndrome with transient myeloproliferative disorder (TMD) is often associated with perinatal liver fibrosis. The authors recently encountered an autopsy case of this disease with a characteristic severe perisinusoidal liver fibrosis. Osteopontin (OPN) is a molecule that plays an important role in diverse fibro-inflammatory diseases. The purpose of the present report was to examine the involvement of OPN in development of the Down syndrome-associated liver fibrosis. Histology indicated severe perisinusoidal fibrosis and ductular arrangements of hepatocytes in the liver. Appearance of atypical megakaryocytes in the liver, a feature of TMD associated with Down syndrome, was not evident. On immunohistochemistry expression of OPN was observed in hepatocytes often having ductular arrangements and infiltrating macrophages. In contrast, a small number of transforming growth factor-beta1 (TGF-beta1)-positive mononuclear cells were present in the liver. Numerous activated hepatic stellate cells (HSC) expressing alpha-smooth muscle actin (alpha-SMA) were seen in the perisinusoidal area. A recent report indicated that OPN could directly activate the HSC. Thus, it is suggested that OPN produced by hepatocytes and macrophages induces activation of the HSC, and leads to the development of perisinusoidal liver fibrosis.

Concept on the pathogenesis and treatment of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an organ-specific autoimmune disease that predominantly affects women and is characterized by chronic, progressive destruction of small intrahepatic bile ducts with portal inflammation and ultimately fibrosis, leading to liver failure in the absence of treatment. Little is known about the etiology of PBC. PBC is characterized by anti-mitochondrial antibodies and destruction of intra-hepatic bile ducts. The serologic hallmark of PBC is the presence of auto-antibodies to mitochondria, especially to the E2 component of the pyruvate dehydrogenase complex (PDC). Current theories on the pathogenesis of PBC favor the hypothesis that the disease develops as a result of an inappropriate immune response following stimulation by an environmental or infectious agent. Some reports suggest that xenobiotics and viral infections may induce PBC. The pathogenetic mechanism is believed to be caused by a defect in immunologic tolerance, resulting in the activation and expansion of self-antigen specific T and B lymphocyte clones and the production of circulating autoantibodies in addition to a myriad of cytokines and other inflammatory mediators. This leads to ductulopenia and persistent cholestasis, by developing end-stage hepatic-cell failure. In this review are given our own and literary data about mechanisms of development of intrahepatic cholestasis and possible ways of its correction.

Analysis of osteopontin in pericystic layer of hepatic hydatid cyst by Western blotting and immunohistochemical technique

AIM: To investigate the expression and distribution of osteopontin (OPN) in hepatic hydatid cyst and its significances.

METHODS: Proteins extracted from 60 surgically excised hydatid cyst tissues were subjected to polyacrylamide gel electrophoresis followed by Western blotting, using polyclonal antibodies directed against OPN; the distribution of OPN was also observed by immunohistochemical techniques.

RESULTS: OPN expression was detected in 48(80%) cases of cysts by Western blotting. OPN was mainly distributed in the side of pericystic layer near the parasite, which was significantly higher than that distributed near the liver (75% vs 8.3%, P < 0.05).

CONCLUSION: OPN plays a regulated role in the granuloma reaction of the pericystic layer of hepatic hydatid cyst.

Global gene expression profiling of dimethylnitrosamine-induced liver fibrosis: from pathological and biochemical data to microarray analysis

The development of hepatocellular carcinoma (HCC) is generally preceded by cirrhosis, which occurs at the end stage of fibrosis. This is a common and potentially lethal problem of chronic liver disease in Asia. The development of microarrays permits us to monitor transcriptomes on a genome-wide scale; this has dramatically speeded up a comprehensive understanding of the disease process. Here we used dimethylnitrosamine (DMN), a nongenotoxic hepatotoxin, to induce rat necroinflammatory and hepatic fibrosis. During the 6-week time course, histopathological, biochemical, and quantitative RT-PCR analyses confirmed the incidence of necroinflammatory and hepatic fibrosis in this established rat model system. Using the Affymetrix microarray chip, 256 differentially expressed genes were identified from the liver injury samples. Hierarchical clustering of gene expression using a gene ontology database allowed the identification of several stage-specific characters and functionally related clusters that encode proteins related to metabolism, cell growth/maintenance, and response to external challenge. Among these genes, we classified 44 potential necroinflammatory-related genes and 62 potential fibrosis-related markers or drug targets based on histopathological scores. We also compared the results with other data on well-known markers and various other microarray datasets that are available. In conclusion, we believe that the molecular picture of necroinflammatory and hepatic fibrosis from this study may provide novel biological insights into the development of early liver damage molecular classifiers than can be used for basic research and in clinical applications. A public accessible website is available at http://LiverFibrosis.nchc.org.tw:8080/LF.

Expression of osteopontin correlates with portal biliary proliferation and fibrosis in biliary atresia

The acquired or perinatal form of biliary atresia is a Th1 fibro-inflammatory disease affecting both the extrahepatic and intrahepatic bile ducts. Osteopontin (OPN) is a Th1 cytokine implicated in several fibro-inflammatory and autoimmune diseases. We examined the expression of OPN in acquired biliary atresia in comparison to normal liver and several pediatric cholestatic liver diseases. We also assessed OPN expression by cultured human bile duct epithelial cells. We found that liver OPN mRNA and protein expression were significantly increased in biliary atresia versus normal and other cholestatic diseases. OPN expression in biliary atresia was localized to epithelium of proliferating biliary structures (ductules and/or ducts) and bile plugs contained therein. No portal biliary OPN expression could be demonstrated in normal liver, syndromic biliary atresia, biliary obstruction not due to biliary atresia, and idiopathic neonatal hepatitis. OPN expression by human bile duct epithelial cells in culture was responsive to IL-2 and TNF-alpha. Our results demonstrate an up-regulation of OPN expression by interlobular biliary epithelium in biliary atresia, which correlates with biliary proliferation and portal fibrosis. These findings suggest a role for OPN in the pathogenesis of biliary atresia.

Effects and regulation of osteopontin in rat hepatic stellate cells

Using a cDNA microarray, we identified osteopontin (OPN) as one of the genes upregulated in cultured activated hepatic stellate cells (HSCs). Northern and western blot analyses showed that OPN was increasingly expressed during the progressive activation of cultured rat HSCs, and a significant increase in OPN was observed in carbon tetrachloride-induced rat liver fibrosis. In biliary atresia, OPN protein was predominantly expressed in Kupffer cells and HSCs in the necrotic areas. Incubation of HSCs with recombinant OPN-induced significant proliferative and migratory effects, and induced matrix metalloproteinase 2 production and activation. Moreover, OPN increased type I collagen production and type II transforming growth factor-beta receptor mRNA and protein. In conclusion, this study shows that OPN is expressed in activated HSCs and suggests that the upregulation of OPN might be a central pathway of HSC activation.

Osteopontin expression in proliferated bile ductules: the correlation with liver damage in fulminant hepatitis

There have been many reports about the severity of hepatic necrosis caused by fulminant hepatitis; however, the relation between proliferated bile ductules and osteopontin (OPN) expression in inflamed areas in each of the clinical forms of fulminant hepatitis has not been described. To analyze the mechanism in the onset of fulminant hepatitis, we classified not only 16 autopsy cases of fulminant hepatitis into two clinical forms--acute and subacute--but also 3 autopsy cases of late-onset hepatic failure (LOHF) associated with fulminant hepatitis, and examined liver specimens by light microscopy and immunohistochemistry and also serum transaminase levels. Histopathologic study revealed that some of the proliferated bile ductules were associated directly with deteriorating hepatocytes and that bile plugs were present in the proliferated bile ductules. The value of the proliferative cell nuclear antigen labeling index (PCNA-L I) for proliferated bile ductules was very high during the acute form of fulminant hepatitis. Immunohistochemical analysis revealed that OPN expression was higher in the proliferated bile ductules of acute-form fulminant hepatitis than in cirrhotic and normal liver bile ducts. Transaminase levels in acute-form fulminant hepatitis were significantly elevated in comparison with levels in the other forms of the disease. Comparison of acute form fulminant hepatitis with the subacute form and LOHF showed OPN expression in proliferated bile ductules and serum aspartate aminotransferase (ALT)max to be decreased in the subacute form of fulminant hepatitis. OPN expression is an important marker of the degree of liver inflammation, and its regulation mechanism is very important to understanding the pathophysiology of fulminant hepatitis.

Cholestatic syndromes

PURPOSE OF REVIEW

This review highlights recent developments in the molecular pathogenesis of cholestasis as well new aspects of pathogenesis and management of clinical cholestatic disorders.

RECENT FINDINGS

Highlights include the role of nuclear receptors including FXR ligands as potential therapeutic agents, new genetic defects for pediatric cholestasis and sclerosing cholangitis, and novel infections and environmental agents as etiologies for primary biliary cirrhosis. Important clinical studies have been published in the area of pediatric cholestatic syndromes, intrahepatic cholestasis of pregnancy, primary biliary cirrhosis, primary and secondary sclerosing cholangitis, cholestasis of sepsis, viral cholestatic syndromes, and drug-induced cholestasis.

SUMMARY

These advances continue to improve understanding of the pathophysiology, diagnosis, and management of cholestatic liver disease.