Destruction of canals of Hering in primary biliary cirrhosis

Age-related differences in drug-induced liver injury: a retrospective single-center study from a large liver disease specialty hospital in China, 2002-2022

BACKGROUND AND AIMS

Drug-induced liver injury (DILI) is a prevalent adverse reaction in clinical settings. However, there is limited research on age-related differences in DILI. We performed a large-scale retrospective study to delineate the characteristics of DILI across different age groups.

METHODS

We collected data on a total of 17,946 patients with confirmed DILI hospitalized at the Fifth Medical Center of the People's Liberation Army (PLA) General Hospital in Beijing, China, from January 1, 2002, to December 31, 2022. The patients were stratified based on age into the following groups: children (< 18 years), young adults (18-44 years), middle-aged individuals (45-64 years), and elderly individuals (≥ 65 years). We gathered demographic information, medical histories, laboratory results, disease severity assessments, and mortality statistics for all patients.

RESULTS

Overall, the distribution of DILI cases across different age groups was as follows: 6.57% were children, 24.82% were young adults, 49.06% were middle-aged individuals, and 19.54% were elderly individuals. The percentage of females increased with age, rising from 36.47% in the pediatric group to 60.51% in the elderly group. Notably, central nervous system agents (15.44%) and anti-infectious agents (21.80%) were more commonly associated with DILI in children, while cardiovascular agents (10.58%) and herbal dietary supplements or traditional medicines (H/TMs) (26.29%) were more prevalent among elderly people with DILI. Among all age groups, hepatocellular-type DILI was more common in the pediatric group (p < 0.001), whereas cholestatic-type DILI and chronic DILI were more prevalent in the elderly group (p < 0.001). Acute liver failure (ALF) and fatal outcomes were more prevalent in the pediatric and elderly groups, particularly in the pediatric group (2.04%, p = 0.041; 0.85%, p = 0.007, respectively).

CONCLUSIONS

Children and elderly individuals face a higher risk of adverse outcomes following DILI.

Early histopathologic changes in primary biliary cholangitis: does 'minimal change' primary biliary cholangitis exist? A pathologist's view

Primary biliary cholangitis (PBC), formerly known as primary biliary cirrhosis, is an autoimmune, slowly progressive, cholestatic liver disease characterized by nonsuppurative destructive cholangitis, and interlobular bile duct destruction. Necroinflammatory activities of the hepatic parenchyma and limiting plates of milder form along with late liver fibrosis may develop. Serum liver tests include elevated serum alkaline phosphatase along with a positive antimitochondrial antibody (AMA) in nearly 95% of patients. Liver biopsies are an important confirmatory and staging tool and are additionally very helpful when AMA is negative. More specifically, the earliest changes in liver biopsy suspicious for PBC can be detected, namely loss of the canals of Hering (CoH), as proposed by various authors recently. CoH loss has been described as an early feature of PBC. We focus on early histologic features of PBC, investigating through the literature the possible role of 'minimal change' supporting the clinical diagnosis of PBC, even in the absence of characteristic granulomatous duct destructive lesions.

Differentiating Biliary Atresia From Idiopathic Neonatal Hepatitis: A Novel Keratin 7 Based Mathematical Approach on Liver Biopsies

BACKGROUND AND AIMS

Differentiating biliary atresia (BA) from idiopathic neonatal hepatitis (INH) is vital in routine pediatric practice. However, on liver biopsy, few cases offer a diagnostic challenge to discriminate these entities with certainty. Bile ductular reaction (DR), intermediate hepatobiliary cells (IHBC) and extra-portal ductules (EPD) indicate progenitor cell activation, as a response to various hepatic insults. The present study aims to quantify DR, IHBC and EPD by Keratin 7 (CK7) immunohistochemistry (IHC) in BA and INH and to devise a mathematical approach to better differentiate the two, especially in histologically equivocal cases.

METHODS

A total of 98 cases were categorized on biopsy as BA, INH or equivocal histology, favoring BA or INH. CK7 DR mean, IHBC mean and EPD mean values were compared between BA and INH. A formula was derived to help distinguish these two entities, the cut-off value, sensitivity and specificity of which were determined by receiver operating characteristic (ROC) curve. This formula was applied and validated on histologically equivocal cases.

RESULTS

Univariate logistic regression revealed significant difference between BA and INH with respect to CK7 DR and CK7 EPD mean (p < 0.001 in both); however, CK7 IHBC mean was not significant (p = 0.08). On multivariate logistic regression, only CK7 DR had significant impact on diagnosis (p < 0.001). A formula: (CK7 DR)² + (CK7 EPD)/(CK7 IHBC) was derived to help distinguish BA from INH. Cut off value of 10.5 and above, determined by ROC curve, favored a diagnosis of BA (sensitivity= 93.4%, specificity= 94.6%). Histologically equivocal and discrepant cases could be correctly categorized using this formula.

CONCLUSIONS

Formula using CK7 IHC parameters may aid pathologists better distinguish BA from INH, especially in histologically equivocal cases.

Keratin 19 and mesenchymal markers for evaluation of epithelial-mesenchymal transition and stem cell niche components in primary biliary cholangitis by sequential elution-stripping multiplex immunohistochemistry

Multiplexed immunohistochemical techniques give insight into contextual cellular relationships by offering the ability to collect cell-specific data with spatial information from formalin-fixed, paraffin-embedded tissue sections. We established an automated sequential elution-stripping multiplex immunohistochemical assay to address two controversial scientific questions in the field of hepatopathology: 1) whether epithelial-to-mesenchymal transition or mesenchymal-to-epithelial transition occurs during liver injury and repair of a chronic liver disease and 2) if there is a stromal:epithelial relationship along the canals of Hering that would support the concept of this biliary structure being a stem/progenitor cell niche. Our 4-plex assay includes both epithelial and mesenchymal clinical immunohistochemical markers and was performed on clinical human liver specimens in patients with primary biliary cholangitis. The assay demonstrated that in each specimen, co-expression of epithelial and mesenchymal markers was observed in extraportal cholangiocytes. In regard to possible mesenchymal components in a stem cell niche, 82.3% ± 5.5% of extraportal cholangiocytes were intimately associated with a vimentin-positive cell. Co-expression of epithelial and mesenchymal markers by extraportal cholangiocytes is evidence for epithelial to mesenchymal transition in primary biliary cholangitis. Vimentin-positive stromal cells are frequently juxtaposed to extraportal cholangiocytes, supporting an epithelial:mesenchymal relationship within the hepatobiliary stem cell niche. Our automated sequential elution-stripping multiplex immunohistochemical assay is a cost-effective multiplexing technique that can be readily applied to a small series of clinical pathology samples in order to answer scientific questions involving cell:cell relationships and cellular antibody expression.

Liver structural transformation after partial hepatectomy and repeated partial hepatectomy in rats: A renewed view on liver regeneration

BACKGROUND

The phenomenon of liver regeneration after partial hepatectomy (PH) is still a subject of considerable interest due to the increasing frequency of half liver transplantation on the one hand, and on the other hand, new surgical approaches which allow removal of massive space-occupying hepatic tumors, which earlier was considered as inoperable. Interestingly, the mechanisms of liver regeneration are extensively studied after PH but less attention is paid to the architectonics of the regenerated organ. Because of this, the question “How does the structure of regenerated liver differ from normal, regular liver?” has not been fully answered yet. Furthermore, almost without any attention is left the liver's structural transformation after repeated hepatectomy (of the re-regenereted liver).

AIM

To compare the architectonics of the lobules and circulatory bed of normal, re-generated and re-regenerated livers.

METHODS

The livers of 40 adult, male, albino Wistar rats were studied. 14 rats were subjected to PH - the 1^st study group (SG1); 10 rats underwent repeated PH – the 2^nd study group (SG2); 16 rats were subjected to sham operation - control group (CG); The livers were studied after 9 months from PH, and after 6 months from repeated PH. Cytological (Schiff reaction for the determination of DNA concen-tration), histological (H&E, Masson trichrome, CK8 Immunohistochemical marker, transparent slides after Indian Ink injection, ), morphometrical (hepatocytes areas, perimeters and ploidy) and Electron Microscopical (Scanning Electron Microscopy of corrosion casts) methods were used.

RESULTS

In the SG1 and SG2, the area of hepatocytes and their perimeter are increased compared to the CG (P < 0.05). However, the areas and perimeters of the hepatocytes of the SG₁ and SG₂ groups reveal a lesser difference. In regenerated (SG₁) and re-regenerated (SG₂) livers, the hepatocytes form the remodeled lobules, which size (300-1200 µm) exceeds the sizes of the lobules from CG (300-600 µm). The remodeled lobules (especially the “mega-lobules” with the sizes 1000-1200 µm) contain the transformed meshworks of the sinusoids, the part of which is dilated asymmetrically. This meshwork might have originated from the several portal venules (interlobular and/or inlet). The boundaries between the adjacent lobules (including mega-lobules) are widened and filled by connective tissue fibers, which gives the liver parenchyma a nodular look. In SG₂ the unevenness of sinusoid diameters, as well as the boundaries between the lobules (including the mega-lobules) are more vividly expressed in comparison with SG₁. The liver tissue of both SG₁ and SG₂ is featured by the slightly expressed ductular reaction.

CONCLUSION

Regenerated and re-regenerated livers in comparison with normal liver contain hypertrophied hepatocytes with increased ploidy which together with transformed sinusoidal and biliary meshworks form the remodeled lobulli.

Canal of Hering loss is an initiating step for primary biliary cholangitis (PBC): A hypothesis

The origin and initiating features of PBC remain obscure despite decades of study. However, recent papers have demonstrated loss of canals of Hering (CoH) to be the earliest histologic change in liver biopsy specimens from patients with primary biliary cholangitis (PBC). We posit that CoH loss prior to significant inflammation or evidence of bile duct injury might be a very early, perhaps even an initiating lesion of PBC. As a potential target of inflammatory or toxic injury, CoH loss may initiate rather than follow the cascade of events leading to duct injury and loss and their sequelae. Toxins may be exogenous in origin, such as environmental toxins or drug exposures, or endogenous, resulting from genetic or epigenetic alterations in canalicular bile transporters upstream from the CoH. In turn, this hypothesis suggests that loss of CoH would lead to altered bile flow and composition injurious to downstream bile ducts, because bile composition has not been modulated by normal CoH physiologic functions or because, in the absence of CoH, canalicular fluid flow into the biliary tree is disrupted interfering with soluble trophic factors important for bile duct integrity. Regardless of the pathogenic mechanism causing CoH loss, only following such loss would the characteristic diagnostic findings of PBC become evident: damage to downstream interlobular and sub-lobular bile ducts. To the extent that the causal mechanisms for CoH loss can be identified, clinical identification (as through early identification of CoH loss) and intervention (depending on the inciting cause) may offer promise for treatment of this enigmatic disease.

Primary Biliary Cholangitis and Autoimmune Hepatitis

Primary biliary cholangitis and autoimmune hepatitis are common autoimmune diseases of the liver. Both have typical clinical presentations, including certain autoantibodies on serologic testing. Histologic features are also often typical: primary biliary cholangitis shows bile duct destruction (sometimes with granulomas), and autoimmune hepatitis shows prominent portal and lobular lymphoplasmacytic inflammation. Both have a wide differential diagnosis, including one another; they may also simultaneously occur within the same patient. Careful use of clinical and histologic criteria may be necessary for diagnosis. First-line therapy is immunosuppression for autoimmune hepatitis and ursodeoxycholic acid for primary biliary cholangitis. Both diseases may progress to cirrhosis.

Spermine oxidase promotes bile canalicular lumen formation through acrolein production

Spermine oxidase (SMOX) catalyzes oxidation of spermine to generate spermidine, hydrogen peroxide (H2O2) and 3-aminopropanal, which is spontaneously converted to acrolein. SMOX is induced by a variety of stimuli including bacterial infection, polyamine analogues and acetaldehyde exposure. However, the physiological functions of SMOX are not yet fully understood. We investigated the physiological role of SMOX in liver cells using human hepatocellular carcinoma cell line HepG2. SMOX localized to the bile canalicular lumen, as determined by F-actin staining. Knockdown of SMOX reduced the formation of bile canalicular lumen. We also found that phospho-Akt (phosphorylated protein kinase B) was localized to canalicular lumen. Treatment with Akt inhibitor significantly reduced the formation of bile canalicular lumen. Acrolein scavenger also inhibited the formation of bile canalicular lumen. PTEN, phosphatase and tensin homolog and an inhibitor of Akt, was alkylated in a SMOX-dependent manner. Our results suggest that SMOX plays a central role in the formation of bile canalicular lumen in liver cells by activating Akt pathway through acrolein production.

Persistent liver biochemistry abnormalities are more common in older patients and those with cholestatic drug induced liver injury

OBJECTIVES

The long-term outcomes of patients with drug induced liver injury (DILI) are not well described. The aim of this study was to determine the frequency and severity of persistent liver biochemistry abnormalities in DILI patients followed over 2 years.

METHODS

Subjects with evidence of liver injury at 6 months after DILI onset were offered a month 12 and 24 study visit.

RESULTS

Amongst the 99 patients with definite, probable, or very likely DILI and available laboratory data at 12 months after DILI onset, 74 (75%) had persistent liver injury (persisters) defined as a serum aspartate aminotransferase (AST) or alanine aminotransferase (ALT) >1.5 × upper limit of normal (ULN) or an alkaline phosphatase >ULN, while 25 (25%) had resolved liver injury (resolvers). On multivariate analysis, month 12 persisters were significantly older (52.6 vs. 43.7 years, P=0.01) and more likely to have a cholestatic lab profile at DILI onset (54 vs. 20%, P<0.01) than resolvers. The month 12 persisters also had significantly poorer SF-36 physical summary scores at DILI onset and throughout follow-up compared with the resolvers (P<0.01). Amongst the 17 subjects with a liver biopsy obtained at a median of 387 days after DILI onset, 9 had chronic cholestasis, 3 had steatohepatitis, and 3 had chronic hepatitis.

CONCLUSIONS

In all, 75% of subjects with liver injury at 6 months after DILI onset have laboratory evidence of persistent liver injury during prolonged follow-up. Higher serum alkaline phosphatase levels at presentation and older patient age were independent predictors of persistent liver injury. Subjects with persistent liver injury at 12 months after DILI onset should be carefully monitored and assessed for liver disease progression.

Pathophysiology and Diseases of the Proximal Pathways of the Biliary System

CONTEXT

Diseases of the proximal pathways of the biliary system can be divided into those that affect the interlobular bile ducts and those that affect the bile canaliculi. The former include primary biliary cirrhosis, small-duct variant of primary sclerosing cholangitis, graft-versus-host disease, and drug-induced liver injury, whereas the latter include progressive familial intrahepatic cholestasis, benign recurrent intrahepatic cholestasis, intrahepatic cholestasis of pregnancy, and drug-induced liver injury.

OBJECTIVE

To summarize the current state of knowledge of diseases of the proximal pathways of the biliary system, with special emphasis on clinical presentation, pathological features, and differential diagnosis.

DATA SOURCES

Clinicopathological information was extracted from pertinent published literature.

CONCLUSIONS

Care of the patient with cholestasis hinges on identifying the etiology. Diagnostic steps in cholestatic conditions comprise a thorough patient history, abdominal imaging, distinct serological studies, and liver biopsy. Primary biliary cirrhosis is characterized by distinctive serological and histological findings. The small-duct variant of primary sclerosing cholangitis is very rare and difficult to diagnose; imaging of the bile ducts is not helpful. Graft-versus-host disease is characterized by damage and loss of intrahepatic bile ducts. Drugs can cause injury variably at the level of bile canaliculus or the interlobular bile duct. Loss of bile ducts may be seen with primary biliary cirrhosis, primary sclerosing cholangitis, graft-versus-host disease, and drug-induced liver injury. Progressive familial intrahepatic cholestasis and progressive familial intrahepatic cholestasis represent 2 extreme ends of the spectrum of abnormalities in transporters responsible for bile formation. Intrahepatic cholestasis of pregnancy has a variable incidence in different parts of the world and may be due to abnormalities in transporter molecules.

Glutamine synthetase expression in activated hepatocyte progenitor cells and loss of hepatocellular expression in congestion and cirrhosis

BACKGROUND & AIMS

In normal human liver, glutamine synthetase (GS) is expressed in a rim of hepatocytes surrounding hepatic veins. GS expression is decreased in cirrhosis and increased in chronic hepatitis, focal nodular hyperplasia, peritumoural hyperplasia and some hepatocellular neoplasms. For the non-neoplastic conditions, there is limited information available on histological pattern of altered GS expression and the mechanisms of these changes.

METHODS

We examined GS expression in 58 large specimens and 45 needle biopsies with a variety of non-neoplastic human liver conditions and in 12 normal control livers. Expression was correlated with clinical and histological disease states.

RESULTS

We identified four patterns of GS expression: (i) Loss of normal perivenular expression was seen in states of chronic congestion, severe cirrhosis and zone 3 necrosis. (ii) Diffuse expression was seen in states with active hepatocellular injury and correlated with Ki-67 expression. (iii) Interface expression was seen in feathery degeneration of chronic cholestasis. (iv) GS expression in activated hepatocyte progenitor cells (HPCs) associated with small ducts and ductules was seen in fulminant hepatic failure and in early and late chronic liver disease and rarely in normal livers.

CONCLUSIONS

Glutamine synthetase expression is increased in regenerating hepatocytes and in early HPCs prior to morphological evidence of hepatocellular differentiation. This may be the earliest marker of HPCs yet demonstrated. Loss of expression may be a reflection of disrupted endothelium-hepatocyte contact in hepatic vein walls caused by congestive injury as found in congestive heart failure and advanced cirrhosis.

Keratin 19 demonstration of canal of Hering loss in primary biliary cirrhosis: "minimal change PBC"?

Liver biopsy is important for diagnosing primary biliary cirrhosis (PBC). Prior investigations suggest that immunostaining for biliary keratin 19 (K19) may show the earliest changes suspicious for PBC, namely, loss of the canals of Hering (CoH). We aimed to study the clinical outcomes of patients whose biopsy specimens appeared histologically near normal or with minimal inflammatory changes, but in which K19 staining revealed widespread periportal CoH loss, a finding we termed "minimal change PBC." Ten patients were identified prospectively as having nearly normal or mildly inflamed biopsy specimens without diagnostic or suggestive histologic features of PBC, but with near complete CoH loss; six had available follow-up clinical data, one had follow-up biopsy. Controls for clinical and/or K19 analysis included six normal livers and biopsy specimens from 10 patients with confirmed early PBC, 10 with early stage chronic hepatitis C (CHC), and nine with resolving, self-limited hepatitis (RSLH). Staining for K19 in normal controls, livers with "minimal change" PBC, CHC, and RSLH showed 9.2 ± 6.0, 0.44 ± 0.37 (P < 0.0001), 5.7 ± 4.6 (n.s.), 4.1 ± 2.1 (P < 0.02) CoH per portal tract, respectively. Patients with available clinical follow up, compared to patients with diagnostic early-stage PBC biopsies, showed identical treatment responses to ursodeoxycholic acid, similar rates and types of nonhepatic autoimmune diseases, and/or subsequent development of autoimmune hepatitis overlap syndrome.

CONCLUSION

We suggest that CoH loss demonstrated by K19 immunostaining is an early feature in PBC. Clinical findings in the years following biopsy, including response to ursodeoxycholic acid, show identical changes to patients with biopsy confirmed PBC. We suggest that this "minimal change" feature may support a clinical diagnosis of PBC even in the absence of characteristic, granulomatous, duct destructive lesions.

Telomere shortening in the damaged small bile ducts in primary biliary cirrhosis reflects ongoing cellular senescence

Telomere shortening is a trigger of cellular senescence. Biliary epithelial cells in damaged small bile ducts in primary biliary cirrhosis (PBC) show senescent features such as the expression of senescence-associated beta-galactosidase and the increased expression of p16(INK4a) and p21(WAF1/Cip1). We investigated whether the telomere shortening is involved in the pathogenesis of biliary cellular senescence in PBC. We analyzed the telomere length of biliary epithelial cells using quantitative fluorescence in situ hybridization in livers taken from the patients with PBC (n = 13) and control livers (n = 13). We also assessed immunohistochemically the prevalence of DNA damage and the expression of p16(INK4a) and p21(WAF1/Cip1). The study showed a significant decrease in telomere length in biliary epithelial cells in the damaged small bile ducts and bile ductules in PBC compared with normal-looking bile ducts and bile ductules in PBC, chronic viral hepatitis, and normal livers (P < 0.01). gammaH2AX-DNA-damage-foci were detected in biliary epithelial cells in damaged small bile ducts and bile ductules in PBC but were absent in biliary epithelial cells in chronic viral hepatitis and normal livers. The expression of p16(INK4a) and p21(WAF1/Cip1) was increased corresponding to telomere shortening and gammaH2AX-DNA-damage-foci in the damaged small bile ducts in PBC.

CONCLUSION

Telomere shortening and an accumulation of DNA damage coincide with increased expression of p16(INK4a) and p21(WAF1/Cip1) in the damaged bile ducts, characterize biliary cellular senescence, and may play a role in the following progressive bile duct loss in PBC.

Vanishing bile duct syndrome

Perhaps no condition associated with chronic cholestasis is less understood than vanishing bile duct syndrome, a term that refers loosely to the group of acquired disorders associated with progressive destruction and disappearance of the intrahepatic bile ducts and, ultimately, cholestasis. Although the array of insults resulting in poor bile flow is vast, most adult patients who have chronic cholestasis have either primary biliary cirrhosis (or primary sclerosing cholangitis; in some cases, however, a cause cannot be identified. This article reviews the multiple causes, postulated pathophysiology, clinical features, and treatment options for this syndrome.

Autoimmune liver disease: overlap and outliers

The three main categories of autoimmune liver disease are autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), and primary sclerosing cholangitis (PSC); all are well-defined entities with diagnosis based upon a constellation of clinical, serologic, and liver pathology findings. Although these diseases are considered autoimmune in nature, the etiology and possible environmental triggers of each remain obscure. The characteristic morphologic patterns of injury are a chronic hepatitis pattern of injury with prominent plasma cells in AIH, destruction of small intrahepatic bile ducts and canals of Hering in PBC, and periductal fibrosis and inflammation involving larger bile ducts with variable small duct damage in PSC. Serological findings include the presence of antimitochondrial antibodies in PBC, antinuclear, anti-smooth muscle, and anti-LKM antibodies in AIH, and pANCA in PSC. Although most cases of autoimmune liver disease fit readily into one of these three categories, overlap syndromes (primarily of AIH with PBC or PSC) may comprise up to 10% of cases, and variant syndromes such as antimitochondrial antibody-negative PBC also occur. Sequential syndromes with transition from one form of autoimmune liver disease to another are rare.

Restoration of bile ducts in drug-induced vanishing bile duct syndrome due to zonisamide

Prolonged drug-induced cholestasis may be due to destruction and disappearance of bile ducts, sometimes referred to as vanishing bile duct syndrome. Although some of these cases progress to fibrosis, cirrhosis, and liver failure, others improve with time. We report a case of a 35-year-old man who developed vanishing bile duct syndrome after ingestion of zonisamide, an antiepileptic drug that is also prescribed for weight loss. His liver biopsy showed complete absence of bile ducts 3 weeks after starting treatment. There was no ductular reaction. The drug was stopped and a follow-up biopsy 3 months later showed strands of intermediate hepatobiliary cells at the periphery of the portal tracts that extended into lobules; these structures lacked lumina and expressed biliary cytokeratins, CK7 and CK19. A third biopsy, 7 months later, showed the presence of ductules with lumina located within portal tracts. Intermediate hepatobiliary cells were rare; although sparse clusters of hepatocytes with membrane staining for CK7 were present. Cholestasis and levels of bilirubin improved over time. The histologic features in this case document the sequence of events in restoration of the biliary tree after loss of bile ducts, which seems to be a process of maturation of intermediate hepatobiliary cells that arise from a proliferative compartment at the porto-hepatic interface.

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.

Preservation of bile ductules mitigates bile duct loss

The finer branches of the biliary tree (FBBT) contain a regenerative compartment. We hypothesized that preservation of the FBBT together with its microvasculature will lead to recovery of biliary damage and prolonged preservation of bile ductules during the development of chronic liver allograft rejection. The interlobular bile ducts, portal bile ductules and extraportal biliary cells with and without microvessels were studied in sequential biopsies in five patients who fulfilled the Banff criteria of early chronic rejection (CR) (imminence group). Biopsies of CR patients (n = 12) served as controls. Biopsies were double immunostained with CD34 (microvessels) and cytokeratin 7 (biliary structures). Proliferation and proangiogenic activity were assessed with Ki67 and VEGF-A immunostaining. Severe damage of bile ducts in the imminence group did not progress to significant bile duct loss. This was associated with a high proliferative activity in all biliary structures and preservation of the microvascular compartment. VEGF-A expression was increased in all but the reperfusion biopsies. In conclusion, both regenerative activity of the FBBT and an intact microvascular compartment are associated with less damage of the biliary tree and could therefore be prerequisites for biliary regeneration.

The finest branches of the biliary tree might induce biliary vascularization necessary for biliary regeneration

BACKGROUND/AIMS

The finer branches of the biliary tree play an important role in biliary regeneration. They are consistently escorted by microvessels. Defects in the vascularization of these structures could impair bile duct regeneration. Therefore, we investigated the pattern of the escorting microvessels during the development of bile duct loss in the human liver, using chronic rejection as a model.

METHODS

The number of interlobular bile ducts, bile ductules and extraportal biliary cells with and without escorting microvessels and the expression of VEGF-A were studied in follow-up biopsies of 12 patients with chronic rejection and 16 control patients with acute rejection without progression to chronic rejection.

RESULTS

The controls showed a proliferation of bile ductules at 1-week and 1-month. Proliferation of bile ductules without microvessels preceded proliferation of bile ductules with microvessels. Proliferation of the microvascular compartment followed biliary proliferation. This sequence of events was not observed in the chronic rejection group, in which all biliary structures decreased in time. VEGF-A expression was increased at 1-week and 1-month in both groups.

CONCLUSIONS

An immediate proliferative response of the finer branches of the biliary tree followed by proliferation of the microvascular compartment after biliary injury seems to be a prerequisite for bile duct regeneration.

Ductular proliferation in liver tissues with severe chronic hepatitis B: An immunohistochemical study

AIM: To clarify the pathogenesis of ductular proliferation and its possible association with oval cell activation and hepatocyte regeneration.

METHODS: Immunohistochemical staining and image analysis of the ductular structures in the liver tissues from 11 patients with severe chronic hepatitis B and 2 healthy individuals were performed. The liver specimens were sectioned serially, and then cytokeratin 8 (CK8), CK19, OV6, proliferating cell nuclear antigens (PCNA), glutathione-S-transferase (GST), α-fetal protein (AFP) and albumin were stained immunohistochemically.

RESULTS: Typical and atypical types of ductular proliferation were observed in the portal tracts of the liver tissues in all 11 patients. The proliferating ductular cells were positive for CK8, CK19, OV6 and PCNA staining. Some atypical ductular cells displayed the morphological and immunohistochemical characteristics of hepatic oval cells. Some small hepatocyte-like cells were between hepatic oval cells and mature hepatocytes morphometrically and immunohistochemically.

CONCLUSION: The proliferating ductules in the liver of patients with severe chronic liver disease may have different origins. Some atypical ductular cells are actually activated hepatic oval cells. Atypical ductular proliferation is related to hepatocyte regeneration and small hepatocyte-like cells may be intermediate transient cells between hepatic oval cells and mature hepatocytes.

Expression of adhesion molecules on mature cholangiocytes in canal of Hering and bile ductules in wedge biopsy samples of primary biliary cirrhosis

AIM: To examine the expression of intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) expression on canals of Hering (CoH) and bile ductules associated with the autoimmune process of bile duct destruction in primary biliary cirrhosis (PBC).

METHODS: Ten wedged liver biopsies of PBC (five cases each of stages 2 and 3) were studied. The liver specimens were processed for transmission electron microscopy. Immunohistochemistry was performed using anti-ICAM-1 and anti-LFA-1 mouse mAbs. In situ hybridization was done to examine the messenger RNA expression of ICAM-1 in formalin-fixed, paraffin-embedded sections using peptide nucleic acid probes and the catalyzed signal amplification (CSA) technique. Immunogold-silver staining for electron microscopy was performed using anti-ICAM and anti-LFA-1 mouse mAbs. The immunogold particles on epithelial cells of bile ductules and cholangiocytes of CoH cells were counted and analyzed semi-quantitatively. Western blotting was performed to confirm ICAM-1 protein expression.

RESULTS: In liver tissues of PBC patients, immunohi-stochemistry showed aberrant ICAM-1 expression on the plasma membrane of epithelial cells lining bile ductules, and also on mature cholangiocytes but not on hepatocytes in CoH. LFA-1-positive lymphocytes were closely associated with epithelial cells in bile ductules. ICAM-1 expression at protein level was confirmed by Western blot. In situhybridization demonstrated ICAM-1 mRNA expression in bile ductules and LFA-1 mRNA in lymphocytes infiltrating the bile ductules. By immunoelectron microscopy, ICAM-1 was demonstrated on the basal surface of epithelial cells in bile ductules and on the luminal surfaces of cholangiocytes in damaged CoH. Cells with intermediate morphology resembling progenitor cells in CoH were not labeled with ICAM-1 and LFA-1.

CONCLUSION: De novo expression of ICAM-1 both on mature cholangiocytes in CoH and epithelial cells in bile ductules in PBC implies that lymphocyte-induced destruction through adhesion by ICAM-1 and binding of LFA-1-expressing activated lymphocytes takes place not only in bile ductules but also in the CoH.

Frequent cellular senescence in small bile ducts in primary biliary cirrhosis: a possible role in bile duct loss

The pathogenesis of progressive bile duct loss in primary biliary cirrhosis remains unclear. In this study, the involvement of cellular senescence of biliary epithelial cells was examined in liver tissue samples from patients with primary biliary cirrhosis (n = 33), and compared with control diseased and normal livers (n = 83). In addition, cellular senescence was induced by oxidative stress in cultured mouse biliary epithelial cells. Biliary epithelial cells in small bile ducts in primary biliary cirrhosis, especially those in patients presenting with chronic non-suppurative cholangitis, frequently expressed senescence-associated beta-galactosidase, and senescence-associated p16(INK4) and p21(WAF1/CIP). In contrast, senescence-associated markers were rarely expressed in small bile ducts in control livers. The infiltration of myeloperoxidase-positive inflammatory cells into biliary epithelial cell layers was closely associated with the cellular senescence of biliary epithelial cells in early-stage PBC. Cellular senescence of cultured mouse biliary epithelial cells was induced by treatment with H2O2 via the p38MAPK-dependent pathway and nitric oxide-augmented H2O2-induced cellular senescence. Oxidative stress- and nitric oxide-mediated cellular senescence may be involved in bile duct lesions, which are followed by progressive bile duct loss in primary biliary cirrhosis.

Progenitor cell expansion: an important source of hepatocyte regeneration in chronic hepatitis

BACKGROUND/AIMS

Progenitor cell activation with subsequent maturation to hepatocytes and cells of the biliary lineage has been demonstrated in a variety of chronic liver diseases but the kinetics and magnitude of the progenitor cell response has not been adequately studied in detail in chronic hepatitis. We undertook this study to evaluate factors responsible for the progenitor cell/ductular response and further dissect the role of disease grade and stage as determinants of hepatocellular differentiation of bipotential progenitor cells in chronic hepatitis.

METHODS

Cytokeratin 7 (and 19) stained biopsies from patients with chronic hepatitis C (n = 47), hepatitis B (n = 20), and autoimmune hepatitis (n = 20) were studied. Ploidy analysis and proliferation indices were evaluated in a subset of cases.

RESULTS

Ductular reactions were present in the majority of cases (97%), appeared early in disease, and correlated with disease activity, while progenitor cell derived hepatocyes appeared later in disease and their extent correlated with disease stage. Proliferation indices of all cell types correlated with disease activity.

CONCLUSIONS

Progenitor cell derived hepatocytes accrue in chronic hepatitis, possibly related to native hepatocellular dysfunction. However, the fate of these hepatocytes is unclear.

Impaired regeneration of biliary cells in human chronic liver allograft rejection. Special emphasis on the role of the finest branches of the biliary tree

Severe loss of bile ducts is a hallmark of chronic liver rejection. We hypothesize that loss of the finest branches of the biliary tree, including the intralobular segments, contributes to an impaired regenerative response of bile ducts in chronic rejection. The number and proliferative response of bile ducts, intraportal ductules, and extraportal biliary cells were studied in graft biopsies of 12 chronic-rejection patients. Twenty-two long-term-surviving patients who experienced acute rejection without chronic rejection served as controls. Reperfusion, 1-week, 1-month, and 1-year biopsies were studied. Monochlonal antibody Ki67 was applied to assess proliferation, and cytokeratin 7 antibody to identify bile ducts, intraportal ductules, and extraportal biliary cells. Progressive loss of bile ducts, intraportal ductules, and extraportal biliary cells was observed in the chronic-rejection group. In controls, all of these structures remained well preserved. Additionally, a significant increase of intraportal ductules was present at 1 week in controls, which was not the case in the chronic-rejection group. Proliferative activity of intraportal ductules and extraportal biliary cells was significantly increased at 1 week in controls. This proliferative activity was higher in the intraportal ductules of controls, compared with the chronic-rejection group. After 1 week, proliferative activity was virtually absent in both groups. In conclusion, our results showed that a deficient proliferative response of the finer branches of the biliary tree, including its intralobular segments, might contribute to bile-duct loss in chronic rejection. This finding supports the postulation that these structures represent a regenerative compartment of the biliary unit in the liver.

Hepatobiliary pathology

Insights provided by molecular biology, immunohistochemistry, and transmission electron microscopy have increased our understanding of the pathogenesis and histopathology of hepatitis C virus (HCV) infection, nonalcoholic steatohepatitis (NASH), and bile ductular proliferative reactions in a number of liver diseases. Human and chimpanzee liver infected with HCV showed viral-like particles (50 to 60 nm in diameter) as well as aggregates of short tubules that represent viral envelope material. Interactions of HCV core protein with apolipoproteins have a role in the pathogenesis of HCV-related steatosis. Pathologists should be aware of the spectrum of liver pathology described with the use of highly active antiretroviral therapy (HAART) agents for the human immunodeficiency virus infection, which includes microvesicular steatosis and more severe hepatic injury with confluent necrosis. Proliferation of bile ductular structures is influenced by specific molecules and proteins (eg, the mucin-associated trefoil proteins and estrogens). The interplay between Notch receptors and Jagged 1 protein, as expressed by many cells of the liver (including bile duct epithelium) varies in primary sclerosing cholangitis (PSC) and primary biliary cirrhosis (PBC). Cholangiocarcinoma does not appear to be a long-term complication of small duct PSC. The fatty liver diseases, both alcoholic and nonalcoholic, are characterized by production of reactive oxygen species that have detrimental effects such as opening mitochondrial permeability transition pores with resultant release of cytochrome c into the cytosol. Hepatocellular carcinoma is now a recognized late complication of NASH. The derivation of hepatic stem cells, the roles of HFE protein and other hepatic and intestinal transport proteins in hemochromatosis, and the histopathologic interpretive challenge of centrilobular lesions in posttransplant liver biopsies are among other recent studies considered in this review.

Cholestatic syndromes

Further insights into the cellular and molecular mechanisms underlying hepatobiliary transport function and its regulation now permit a better understanding of the pathogenesis and treatment options of cholestatic liver diseases. Identification of the molecular basis of hereditary cholestatic syndromes will result in an improved diagnosis and management of these conditions. New insights into the pathogenesis of extrahepatic manifestations of cholestasis (eg, pruritus) have facilitated new treatment strategies. Important new studies have been published about the pathogenesis, clinical features, diagnosis, and treatment of primary biliary cirrhosis, primary sclerosing cholangitis, cholestasis of pregnancy, total parenteral nutrition-induced cholestasis, drug-induced cholestasis, and viral cholestatic syndromes.