Peribiliary capillary plexus around interlobular bile ducts in various chronic liver diseases: An immunohistochemical and morphometric study

Gallstone and Gallbladder Disease: Biliary Tract and Cholangiopathies

Cholestatic liver diseases are named primarily due to the blockage of bile flow and buildup of bile acids in the liver. Cholestasis can occur in cholangiopathies, fatty liver diseases, and during COVID-19 infection. Most literature evaluates damage occurring to the intrahepatic biliary tree during cholestasis; however, there may be associations between liver damage and gallbladder damage. Gallbladder damage can manifest as acute or chronic inflammation, perforation, polyps, cancer, and most commonly gallstones. Considering the gallbladder is an extension of the intrahepatic biliary network, and both tissues are lined by biliary epithelial cells that share common mechanisms and properties, it is worth further evaluation to understand the association between bile duct and gallbladder damage. In this comprehensive article, we discuss background information of the biliary tree and gallbladder, from function, damage, and therapeutic approaches. We then discuss published findings that identify gallbladder disorders in various liver diseases. Lastly, we provide the clinical aspect of gallbladder disorders in liver diseases and ways to enhance diagnostic and therapeutic approaches for congruent diagnosis. © 2023 American Physiological Society. Compr Physiol 13:4909-4943, 2023.

Plasmalemmal Vesicle-Associated Protein Is Associated with Endothelial Cells Sprouting from the Peribiliary Capillary Plexus in Human Cirrhotic Liver

INTRODUCTION

Plasmalemmal vesicle-associated protein (PLVAP) is an endothelial-specific integral membrane glycoprotein that localizes to caveolae and fenestrae in animal models; however, little is known about PLVAP in endothelial cells (ECs) in hepatic sinusoids during liver cirrhosis (LC). Here, we aimed to elucidate PLVAP localization and expression in the human liver during LC progression.

METHODS

PLVAP protein expression was detected in specimens from normal control livers and hepatitis C-related cirrhotic livers using immunohistochemistry, Western blotting, and immunoelectron microscopy.

RESULTS

PLVAP mainly localized to the peribiliary capillary plexus (PCP) and was rarely observed in hepatic artery branches and portal venules in control tissue, but was aberrantly expressed in capillarized sinusoids and proliferated capillaries in fibrotic septa within cirrhotic liver tissue. Ultrastructural analysis indicated that PLVAP localized to thin ECs in some caveolae, whereas PLVAP localized primarily to caveolae-like structures and proliferative sinusoid capillary EC vesicles in cirrhotic liver tissue. Western blot analysis confirmed that PLVAP was overexpressed at the protein level in advanced cirrhotic liver tissue.

CONCLUSION

PLVAP was strongly expressed in the caveolae of proliferated capillaries directly connected with sinusoids linked with the PCP, suggesting that it plays a role in angiogenesis and sinusoidal remodeling in LC.

Experimentally Induced Biliary Atresia by Means of Rotavirus-Infection Is Directly Linked to Severe Damage of the Microvasculature in the Extrahepatic Bile Duct

Vascular damage has been reported to contribute to atresia formation in several diseases including biliary atresia. This study focused on the extrahepatic biliary plexus in experimental biliary atresia. Newborn BALB/cAnNCrl-pups were infected with rhesus rotavirus within 24 hr after birth to induce experimental biliary atresia. The extrahepatic biliary plexus was examined by confocal microscopy on whole-mount preparations, scored by three independent researchers, and further evaluated at the subcellular level with transmission electron microscopy. Imaging results revealed a progressive destruction of the extrahepatic biliary vascular plexus in the course of experimental biliary atresia induced by rotavirus infection. Endothelial cell damage was already visible as cell swelling and necrosis in the first days after infection and a damaged microcirculation that rapidly deteriorated with progression of obliterative cholangiopathy, was observed in the infected mice as early as 72 hr after birth. In experimental biliary atresia, the destruction of the extrahepatic biliary vascular plexus starts already in the first days postinfection and clearly precedes the morphological symptoms of atresia. The deterioration of the vascular bed architecture continues with disease progression. Therefore, we conclude that the (ultra)structural changes in the extrahepatic biliary microvasculature occurring before the visible onset of atresia has a predictive diagnostic value and this impairment in blood supply to the extrahepatic bile duct may be an important contributing factor to the pathogenesis of acquired biliary atresia. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 302:818-824, 2019. © 2018 Wiley Periodicals, Inc.

Antibody-Mediated Rejection After Liver Transplant

Antibody-mediated rejection (AMR) in liver transplants is a field in its infancy compared with its allograft cohorts of the kidney and lung. Acute AMR is diagnosed based on specific clinical and histopathologic criteria: serum donor specific antibodies, C4d staining, histopathologic findings on liver biopsy, and exclusion of other entities. In contrast, the histologic features of chronic AMR are not as specific and it is a more challenging diagnosis to make. Treatments of acute and chronic AMR include some combination of steroids, immune-modulating agents, intravenous immunoglobulin, plasmapheresis, and proteasome inhibitors.

Functional Immune Anatomy of the Liver-As an Allograft

The liver is an immunoregulatory organ in which a tolerogenic microenvironment mitigates the relative "strength" of local immune responses. Paradoxically, necro-inflammatory diseases create the need for most liver transplants. Treatment of hepatitis B virus, hepatitis C virus, and acute T cell-mediated rejection have redirected focus on long-term allograft structural integrity. Understanding of insults should enable decades of morbidity-free survival after liver replacement because of these tolerogenic properties. Studies of long-term survivors show low-grade chronic inflammatory, fibrotic, and microvascular lesions, likely related to some combination of environment insults (i.e. abnormal physiology), donor-specific antibodies, and T cell-mediated immunity. The resultant conundrum is familiar in transplantation: adequate immunosuppression produces chronic toxicities, while lightened immunosuppression leads to sensitization, immunological injury, and structural deterioration. The "balance" is more favorable for liver than other solid organ allografts. This occurs because of unique hepatic immune physiology and provides unintended benefits for allografts by modulating various afferent and efferent limbs of allogenic immune responses. This review is intended to provide a better understanding of liver immune microanatomy and physiology and thereby (a) the potential structural consequences of low-level, including allo-antibody-mediated injury; and (b) how liver allografts modulate immune reactions. Special attention is given to the microvasculature and hepatic mononuclear phagocytic system.

ABO-compatible liver allograft antibody-mediated rejection: an update

PURPOSE OF REVIEW

Liver allograft antibody-mediated rejection (AMR) studies have lagged behind parallel efforts in kidney and heart because of a comparative inherent hepatic resistance to AMR. Three developments, however, have increased interest: first, solid phase antibody testing enabled more precise antibody characterization; second, increased expectations for long-term, morbidity-free survival; and third, immunosuppression minimization trials.

RECENT FINDINGS

Two overlapping liver allograft AMR phenotypic expressions are beginning to emerge: acute and chronic AMR. Acute AMR usually occurs within the several weeks after transplantation and characterized clinically by donor-specific antibodies (DSA) persistence, allograft dysfunction, thrombocytopenia, and hypocomplementemia. Acute AMR appears histopathologically similar to acute AMR in other organs: diffuse microvascular endothelial cell hypertrophy, C4d deposits, neutrophilic, eosinophilic, and macrophag-mediated microvasculitis/capillaritis, along with liver-specific ductular reaction, centrilobular hepatocyte swelling, and hepatocanalicular cholestasis often combined with T-cell-mediated rejection (TCMR). Chronic AMR is less well defined, but strongly linked to serum class II DSA and associated with late-onset acute TCMR, fibrosis, chronic rejection, and decreased survival. Unlike acute AMR, chronic AMR is a slowly evolving insult with a number of potential manifestations, but most commonly appears as low-grade lymphoplasmacytic portal and perivenular inflammation accompanied by unusual fibrosis patterns and variable microvascular C4d deposition; capillaritis can be more difficult to identify than in acute AMR.

SUMMARY

More precise DSA characterization, increasing expectations for long-term survival, and immunosuppression weaning precipitated a re-emergence of liver allograft AMR interest. Pathophysiological similarities exist between heart, kidney, and liver allografts, but liver-specific considerations may prove critical to our ultimate understanding of all solid organ AMR.

Portal blood flow via the peribiliary vascular plexus demonstrated by contrast-enhanced ultrasonography with Sonazoid

PURPOSE

We report two cases in which portal blood flow via the peribiliary vascular plexus (PBP) was clearly demonstrated using contrast-enhanced intra-operative ultrasonography (CE-IOUS).

METHODS

Two patients who underwent hemihepatectomies were investigated using CE-IOUS. Before injection of the contrast medium, both the hepatic arterial and portal venous flows of the hemiliver to be resected were interrupted by ligating those corresponding vessels at the hepatic hilum. Subsequently, the perfluorobutane microbubbles were injected intravenously.

RESULTS

In the early vascular phase, a remarkable intermittent flow was visualized in the lumen of the portal branches whose inflows were interrupted. The flow of the portal vein then disappeared as a result of ligating the hepatic duct concomitantly with the surrounding connective tissue. We considered that the portal venous flow appearing under the condition of total disruption of original inflow was supplied from the hepatic artery through the PBP.

CONCLUSIONS

This is the first report of blood flow via the PBP in human liver visualized by dynamic image study.

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.

Pathogenesis of primary biliary cirrhosis: A unifying model

Primary biliary cirrhosis (PBC) is a disease of unknown etiology leading to progressive destruction of small intrahepatic bile ducts and eventually to liver cirrhosis and failure. It is characterised by female predominance and serum auto-antibodies to mitochondrial antigens targeting the E2 components of the 2-oxoacid dehydrogenase complex. Although they are associated with disease pathogenesis, no concrete evidence has been presented so far. Epidemiological data indicate that a geographical clustering of cases and possible environmental factors are implicated in pathogenesis. A number of genetic factors play a role in determining disease susceptibility or progression, although no definitive conclusion has been reached so far. A key factor to immune pathogenesis is considered to be the breakdown of immune tolerance, either through molecular mimicry or through the so called determinant density model. In this review, the available data regarding the pathogenesis of primary biliary cirrhosis are described and discussed. A new unifying hypothesis based on early endothelin overproduction in primary biliary cirrhosis (PBC) is presented and discussed.

Vascular endothelial growth factor stimulates rat cholangiocyte proliferation via an autocrine mechanism

BACKGROUND & AIMS

Vascular endothelial growth factor (VEGF) is secreted by several epithelia and modulates cellular functions by autocrine and paracrine mechanisms. The role of VEGF in cholangiocyte pathophysiology is unknown. We evaluated the role of VEGF in the regulation of cholangiocyte proliferation in rats that underwent bile duct ligation.

METHODS

The expression of VEGF-A and VEGF-C and their receptors in cholangiocytes from normal and BDL rats was evaluated. Normal or BDL rats were treated with recombinant-VEGF-A or recombinant-VEGF-C or anti-VEGF antibodies, and proliferation of cholangiocytes was evaluated in situ by morphometry and in vitro by proliferating cell nuclear antigen immunoblots and MTS assay. In vitro, normal rat cholangiocyte cultures were stimulated with r-VEGF-A or r-VEGF-C and proliferation and signal transduction were evaluated.

RESULTS

We found that (1) cholangiocytes express messenger RNA and protein for VEGF-A, VEGF-C, VEGF receptor 2 (VEGFR-2), and VEGF receptor 3 (VEGFR-3) and secrete VEGF; (2) secretion of VEGF and expression of VEGFR-2 and VEGFR-3 increases in BDL cholangiocytes; (3) blocking VEGF in vivo by anti-VEGF-A or anti-VEGF-C antibodies decreases cholangiocyte proliferation; (4) the in vivo administration of r-VEGF-A or r-VEGF-C induces cholangiocyte proliferation in normal rats; and (5) in vitro, VEGF-A increases normal rat cholangiocyte culture proliferation by activation of inositol 1,4,5-triphosphate/Ca2+/protein kinase C alpha and phosphorylation of Src/ERK1/2.

CONCLUSIONS

Cholangiocytes secrete VEGF and express VEGFR-2 and VEGFR-3, all of which are amplified in BDL cholangiocytes. VEGF induces cholangiocyte proliferation by activation of inositol 1,4,5-triphosphate/[Ca2+]i/protein kinase C alpha and phosphorylation of Src/ERK1/2. VEGF mediates the adaptive proliferative response of cholangiocytes to cholestasis.

MRI findings of primary biliary cirrhosis: correlation with Scheuer histologic staging

Magnetic resonance imaging (MRI) findings of primary biliary cirrhosis (PBC; currently regarded as a vanishing bile duct syndrome) are not established. In this report, we describe our preliminary analysis of the relation between MRI findings and histopathologic staging of PBC and review clinical, morphologic, and MRI findings of PBC especially focusing on the staging of PBC.

Evidence of angiogenesis in primary biliary cirrhosis: an immunohistochemical descriptive study

BACKGROUND/AIMS

The intrahepatic inflammatory process occurring during primary biliary cirrhosis contributes to bile duct destruction, but the cellular and molecular pathways involved are largely unknown. Furthermore, additional pathogenetic mechanisms may exist. We aimed at evaluating the cellular infiltrate phenotype; the expression of lymphocyte activation, antigen recognition and cell-adhesion molecules; the occurrence of hepatic angiogenesis and the molecules involved.

METHODS

Immunohistochemical investigations were performed in frozen liver biopsy sections from primary biliary cirrhosis patients.

RESULTS

CD8+ and CD69+ T cells were predominant in inflammatory infiltrates around damaged cholangiocytes; beta2-microglobulin conformational epitope and intercellular adhesion molecule-1 expression were enhanced in bile ducts and hepatocytes. Inflamed portal areas showed vascular cell adhesion molecule-1 up-regulation; formation of tubule-like structures (neovessels) by endothelial cells expressing vascular endothelial-cadherin and CD-31; vascular endothelial growth factor expression in surrounding sinusoidal endothelial cells; and enhanced expression of angiopoietins 1 and 2, their receptor Tie-2 and endoglin, suggesting their involvement in new vascular structure formation.

CONCLUSIONS

The inflammatory infiltrate in primary biliary cirrhosis shows an increased reactivity for lymphocyte activation, antigen recognition and cell- and vascular-adhesion molecules. Additionally, intrahepatic angiogenesis occurs, involving vascular endothelial growth factor, angiopoietins 1 and 2, Tie-2 and endoglin in neovessel formation.

Angiogenesis in chronic inflammatory liver disease

Intrahepatic hypoxia may occur during the inflammatory and fibrotic processes that characterize several chronic liver diseases of viral and autoimmune origin. As a consequence, new vascular structures are formed to provide oxygen and nutrients. Angiogenesis involves a tightly regulated network of cellular and molecular mechanisms that result in the formation of functional vessels. Of particular importance are growth factors, molecules involved in matrix remodeling and cell migration, and vessel maturation-related factors. In recent years, a number of studies have examined the expression and function of many pro- and antiangiogenic molecules in the setting of nontumoral chronic liver diseases and liver regeneration. This review examines the potential pathogenetic role of angiogenesis in the context of viral hepatitis, cirrhosis, autoimmune hepatitis, primary biliary cirrhosis, and alcoholic liver disease. The future perspectives for research in this field are outlined.

Aberrant local renin-angiotensin II responses in the pathogenesis of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is an idiopathic inflammatory disorder of the biliary tract characterized by diffuse biliary tract stricture formation, progressive chronic cholestasis and the development of secondary biliary cirrhosis. Biliary tract ischemia can produce morphological changes identical to PSC. We propose the existence of a localized renin-angiotensin system within the liver and extend the hypothesis that aberrant production of angiotensin II within the portal tract is the critical event contributing to the pathogenesis of PSC. A chronic reparative and proliferative state caused by chronic ischemia may promote carcinogenesis. Proof of this hypothesis will have implications for future therapeutic approaches given that current treatments for PSC aimed at reducing inflammation or the effects of cholestasis have proven ineffective.