The common bile duct ligation in rat: A relevant in vivo model to study the role of mechanical stress on cell and matrix behaviour

Surgical and histological boundary of the hepatic hilar plate system: basic study relevant to surgery for hilar cholangiocarcinoma regarding the "true" proximal ductal margin

BACKGROUND

We sought to expand the clinico-anatomical limit of the proximal ductal margin (Limit-PDM) for resectability of hilar cholangiocarcinoma (HCCA).

METHODS

The practical boundary of the hilar plate (PBHP) was defined as the location where the bile duct (BD) could not be isolated by dissection. The distance between PBHP and two well-known clinical landmarks of Limit-PDM, the right edge of the bifurcation of the anterior and posterior branch of the right portal vein (Posterior-Landmark) and the left edge of the umbilical portion of the portal vein (Left-Landmark), and histological features around the PBHP were assessed using 55 adult cadaver livers.

RESULTS

BD was almost always isolatable beyond the traditional clinical landmarks. The median distance was 6.9 mm (interquartile range [IQR] 6.0-8.3 mm) between the PBHP and the Posterior-Landmark, and 8.9 mm (IQR 6.7-10.2 mm) between the PBHP and the Left-Landmark. Histologically, the sheath surrounding the portal triad was loose, thick with few elastic fibers and small arteries near the hepatic hilum. Near the PBHP, the sheath was dense, thin, and abundant with elastic fibers and small arteries.

CONCLUSIONS

Limit-PDM is more peripheral than the traditional clinical landmark-based margin and histological transition near the PBHP was revealed.

Partial Bile Duct Ligation in the Mouse: A Controlled Model of Localized Obstructive Cholestasis

In rodents, complete bile duct ligation (cBDL) of the common bile duct is an established surgical technique for studying obstructive cholestasis and bile duct proliferation. However, long-term experiments can lead to increased morbidity and mortality. In select mouse strains with underlying liver disease, meaningful comparisons can be made even with ligation of a single lobe of the liver, which can reduce animal losses and expenses. Here, we describe partial bile duct ligation (pBDL) in the mouse, in which only the left hepatic bile duct is ligated, causing biliary obstruction in the left lobe but not the remaining lobes. With careful microsurgical technique, pBDL experiments can be cost-effective, since the unligated lobe serves as an internal control to the ligated lobes, when subjected to the same conditions in the same animal. Unlike cBDL, a separate sham-operated control group is not necessary. pBDL is highly useful to directly compare localized versus systemic effects of cholestasis and other retained bile components. pBDL can also be repurposed as a novel method to investigate mechanisms related to medications and cell migration.

Elastin in the Liver

A characteristic feature of liver cirrhosis is the accumulation of large amounts of connective tissue with the prevailing content of type I collagen. Elastin is a minor connective tissue component in normal liver but it is actively synthesized by hepatic stellate cells and portal fibroblasts in diseased liver. The accumulation of elastic fibers in later stages of liver fibrosis may contribute to the decreasing reversibility of the disease with advancing time. Elastin is formed by polymerization of tropoelastin monomers. It is an amorphous protein highly resistant to the action of proteases that forms the core of elastic fibers. Microfibrils surrounding the core are composed of fibrillins that bind a number of proteins involved in fiber formation. They include microfibril-associated glycoproteins (MAGPs), microfibrillar-associated proteins (MFAPs) and fibulins. Lysyl oxidase (LOX) and lysyl oxidase-like proteins (LOXLs) are responsible for tropoelastin cross-linking and polymerization. TGF-β complexes attached to microfibrils release this cytokine and influence the behavior of the cells in the neighborhood. The role of TGF-β as the main profibrotic cytokine in the liver is well-known and the release of the cytokines of TGF-β superfamily from their storage in elastic fibers may affect the course of fibrosis. Elastic fibers are often studied in the tissues where they provide elasticity and resilience but their role is no longer viewed as purely mechanical. Tropoelastin, elastin polymer and elastin peptides resulting from partial elastin degradation influence fibroblastic and inflammatory cells as well as angiogenesis. A similar role may be performed by elastin in the liver. This article reviews the results of the research of liver elastic fibers on the background of the present knowledge of elastin biochemistry and physiology. The regulation of liver elastin synthesis and degradation may be important for the outcome of liver fibrosis.

Rat model of cholelithiasis with human gallstones implanted in cholestasis-induced virtual gallbladder

AIM: To facilitate translational research on cholelithiasis, we have developed a rat model of human gallstones by exploiting the unique biliopancreatic features of this species.

METHODS: Under anesthesia, 16 adult rats of equal genders underwent two times of abdominal surgery. First, their common bile duct (CBD) was ligated to cause cholestasis by total biliary obstruction (TBO). On day 0, 1, 3, 7, 14, 21 and 28 after TBO, magnetic resonance imaging (MRI) was conducted to monitor the dilatation of the CBD, and blood was sampled to analyze total serum bilirubin (TSB). Secondly, on day 30, the abdomen was re-opened and gallstone(s) collected from human patients were implanted in the dilated CBD as a virtual gallbladder (VGB), which was closed by suture ligation. This rat cholelithiasis model was examined by MRI, clinical observation, microcholangiography and histology.

RESULTS: All rats survived two laparotomies. After ligation, the CBD was dilated to a stable size of 4 to 30 mm in diameter on day 21-28, which became a VGB. The rats initially showed signs of jaundice that diminished over time, which paralleled with the evolving TSB levels from 0.6 ± 0.3 mg/dL before ligation, through a peak of 10.9 ± 1.9 mg/dL on day 14, until a nearly normalized value after day 28. The dilated CBD with thickened wall allowed an incision for implantation of human gallstones of 1-10 mm in diameter. The rat cholelithiasis was proven by in vivo MRI and postmortem microcholangiography and histomorphology.

CONCLUSION: A rat model cholelithiasis with human gallstones has been established, which proves feasible, safe, reliable, nontoxic and cost-effective. Given the gallstones of human origin, applications of this model may be of help in translational research such as optical detection and lysis of gallstones by systemic drug administration.

Partial Ligation of the Common Bile Duct Results in Reversible Cholestasis in Rats

The animal model of common bile duct ligation is very toxic; therefore, the aim of this study was to establish a new model of obstructive jaundice in rats with partial common bile duct obstruction. Male Sprague-Dawley rats were subjected to a sham operation or partial ligation of bile duct procedure. Serum biochemistry, liver histology, and expression of bile salt transporters were examined after surgery. Serum levels of aspartate aminotransferase, alkaline phosphatase, total bilirubin, and bile acids were significantly increased in the partial bile duct ligation group 3 days after surgery. However, these changes spontaneously normalized within 14 days after surgery in the partial bile duct ligation group compared with the sham group. Bile infarcts, ductular reaction, and abundant hepatocyte turnover were detected exclusively in the partial bile duct ligation group on postoperative day 3. However, these changes dramatically reversed 14 days after surgery. Bile salt transporter expression was significantly decreased at day 3 and gradually recovered in the following 2 weeks. In conclusion, the current rat model of obstructive cholestasis is reversible, representing the clinical characteristics of partial biliary obstruction, and may be used to investigate the effects of various therapeutic strategies on reversible acute cholestasis.

Imaging hamster model of bile duct cancer in vivo using fluorescent L-glucose derivatives

Extrahepatic bile duct cancer (cholangiocarcinoma) has a poor prognosis. Since surgical resection is the only way to prolong the patient’s life, it is of critical importance to correctly determine the extent of lesions. However, conventional pre-operative assessments have insufficient spatial resolution for determining the surgical margin. A fluorescent contrast agent might provide a more precise measure to identify anomalies in biliary surface, when combined with probe-based confocal laser endomicroscopy (pCLE). We have previously shown that 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-l-glucose (2-NBDLG), a fluorescent derivative of l-glucose (fLG), is specifically taken up into spheroids consisting of cells showing heterogeneous nuclear-cytoplasm ratio, a feature of malignant cells in clinical settings. In addition, a combined use of 2-TRLG, a membrane-impermeable fLG, with 2-NBDLG visualized membrane integrity as well. We therefore explored in the present study the availability of the fLGs in vivo as a contrast agent for pCLE by using a hamster model of cholangiocarcinoma. Extrahepatic cholangiocarcinoma developed in mid common duct in ~20 % of the animals subjected to cholecystoduodenostomy with the ligation at the distal end of the common duct followed by injection of a carcinogen N-nitrosobis(2-oxopropyl)amine. After infusing bile duct with a solution containing 2-NBDLG and 2-TRLG, the lumen was surgically exposed and examined by pCLE. Fluorescence pattern characterized by bright spots and dark clumps was detected in the areas diagnosed with cholangiocarcinoma in later histopathology, whereas no such pattern was detected in control animals. These findings may form a basis for elucidating a potential availability of fLGs in imaging cholangiocarcinoma by pCLE.

Portal Fibroblasts in Biliary Fibrosis

Portal fibroblasts are a minor population in the normal liver, found in the periportal mesenchyme surrounding the bile ducts. While many researchers have hypothesized that they are an important myofibroblast precursor population in biliary fibrosis, responsible for matrix deposition in early fibrosis and for recruiting hepatic stellate cells, the role of portal fibroblasts relative to hepatic stellate cells is controversial. Several papers published in the past year have addressed this point and have identified other potential roles for portal fibroblasts in biliary fibrosis. The goal of this review is to critically assess these recent studies, to highlight gaps in our knowledge of portal fibroblasts, and to suggest directions for future research.

Bone marrow cell transplantation is associated with fibrogenic cells apoptosis during hepatic regeneration in cholestatic rats

Liver fibrosis is accompanied by hepatocyte death and proliferation of α-SMA+ fibrogenic cells (activated hepatic stellate cells and myofibroblasts), which synthesize extracellular matrix components that contribute to disorganization of the hepatic parenchyma and loss of liver function. Therefore, apoptosis of these fibrogenic cells is important to hepatic regeneration. This study aimed to analyze the effect of cell therapy using bone marrow mononuclear cell (BMMNC) transplantation on α-SMA expression and on apoptosis of hepatic cells during liver fibrosis induced by bile duct ligation (BDL). Livers were collected from normal rats, fibrotic rats after 14 and 21 days of BDL, and rats that received BMMNC at 14 days of BDL and were analyzed after 7 days. Apoptosis in fibrogenic cells was analyzed by immunoperoxidase, confocal microscopy, and Western blotting, and liver regeneration was assessed by proliferating cell nuclear antigen staining. Results showed that caspase-3 and proliferating cell nuclear antigen expression were significantly increased in the BMMNC-treated group. Additionally, confocal microscopy analysis showed cells coexpressing α-SMA and caspase-3 in these animals, suggesting fibrogenic cell death. These results suggest a novel role for BMMNC in liver regeneration during fibrotic disease by stimulating fibrogenic cells apoptosis and hepatocyte proliferation, probably through secretion of specific cytokines that modulate the hepatic microenvironment toward an antifibrogenic balance.

Tissue mechanics and fibrosis

Mechanical forces are essential to the development and progression of fibrosis, and are likely to be as important as soluble factors. These forces regulate the phenotype and proliferation of myofibroblasts and other cells in damaged tissues, the activation of growth factors, the structure and mechanics of the matrix, and, potentially, tissue patterning. Better understanding of the variety and magnitude of forces, the characteristics of those forces in biological tissues, and their impact on fibrosis in multiple tissues is needed and may lead to identification of important new therapeutic targets. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

Elastin accumulation is regulated at the level of degradation by macrophage metalloelastase (MMP-12) during experimental liver fibrosis

Elastin has been linked to maturity of liver fibrosis. To date, the regulation of elastin secretion and its degradation in liver fibrosis has not been characterized. The aim of this work was to define elastin accumulation and the role of the paradigm elastase macrophage metalloelastase (MMP-12) in its turnover during fibrosis. Liver fibrosis was induced by either intraperitoneal injections of carbon tetrachloride (CCl(4) ) for up to 12 weeks (rat and mouse) or oral administration of thioacetamide (TAA) for 1 year (mouse). Elastin synthesis, deposition, and degradation were investigated by immunohistochemistry, quantitative polymerase chain reaction (qPCR), western blotting, and casein zymography. The regulation of MMP-12 elastin degradation was defined mechanistically using CD11b-DTR and MMP-12 knockout mice. In a CCl(4) model of fibrosis in rat, elastin deposition was significantly increased only in advanced fibrosis. Tropoelastin expression increased with duration of injury. MMP-12 protein levels were only modestly changed and in coimmunoprecipitation experiments MMP-12 was bound in greater quantities to its inhibitor TIMP-1 in advanced versus early fibrosis. Immunohistochemistry and macrophage depletion experiments indicated that macrophages were the sole source of MMP-12. Exposure of CCl(4) in MMP-12(-/-) mice led to a similar degree of overall fibrosis compared to wildtype (WT) but increased perisinusoidal elastin. Conversely, oral administration of TAA caused both higher elastin accumulation and higher fibrosis in MMP-12(-/-) mice compared with WT.

CONCLUSION

Elastin is regulated at the level of degradation during liver fibrosis. Macrophage-derived MMP-12 regulates elastin degradation even in progressive experimental liver fibrosis. These observations have important implications for the design of antifibrotic therapies.

The precarious state of the liver after a Fontan operation: summary of a multidisciplinary symposium

As the cohort of survivors with the single-ventricle type of congenital heart disease grows, it becomes increasingly evident that the state of chronically elevated venous pressure and decreased cardiac output inherent in the Fontan circulation provides the substrate for a progressive decline in functional status. One organ at great risk is the liver. Wedged between two capillary beds, with the pulmonary venous bed downstream, which typically has no pulsatile energy added in the absence of a functional right ventricle, and the splanchnic bed upstream, which may have compromised inflow due to inherent cardiac output restriction characteristic of the Fontan circulation, the liver exists in a precarious state. This review summarizes a consensus view achieved at a multidisciplinary symposium held at The Children's Hospital of Philadelphia in June 2011. The discussion includes current knowledge concerning the hemodynamic foundations of liver problems, the diagnostic tools available, the unique histopathology of the liver after the Fontan operation, and proposed mechanisms for hepatic fibrosis at the cellular level. At the completion of the symposium, a consensus recommendation was made by the authors' group to pursue a new prospective protocol for clinical evaluation of the liver for all patients in our practice 10 years after the Fontan operation.

A series of six cases of sphincter of Oddi pathology in the cat (2008-2009)

The sphincter of Oddi (SO) is located within the wall of the duodenum as the terminal part of the common bile duct. Six cats are reported with obstructive processes within their SO. Three of them may have had some form of sphincter dysfunction associated with the pre-existing complex known as 'inflammatory bowel disease' (IBD), two may have had the equivalent of the infant human condition known as 'bile plug syndrome' and the sixth had sphincter dysfunction associated with a tumour at the confluence of the common and right hepatic duct. In all six cases, the sphincter obstructions were surgically managed. The outcomes for 4/6 were favourable but 1/6 was euthanased intraoperatively, and 1/6 had a metastatic neoplasia and was euthanased 2 months postoperatively.

Increased melibiose/rhamnose ratio in bile of rats with acute cholestasis

BACKGROUND AND AIM

Melibiose/rhamnose permeability test is used for noninvasive intestinal mucosa barrier testing. However, the possible escape route of the absorbed saccharides through either intact or impaired blood-biliary barriers has not so far been explored. The objective of the present study was therefore two-fold: First, to describe in detail the biliary pharmacokinetics of melibiose and rhamnose in rats; second, to evaluate the changes of both sugars' pharmacokinetics upon impairment of the blood-biliary barrier by acute extrahepatic cholestasis in rats.

METHODS

Bile duct obstructed (BDO), sham-operated and intact (unoperated) male Wistar rats were administered, 24 h after the appropriate intervention, with a single intravenous dose of melibiose and rhamnose, and a 4-h pharmacokinetic study was performed.

RESULTS

In intact animals, the biliary excretion of melibiose and rhamnose was only 0.06% and 0.4% of the administered dose, respectively, while the urinary excretion accounted for 70.6% and 61.7%, respectively. In BDO animals, the biliary excretion rate of both saccharides, especially that of melibiose, was increased with a consequent 4.4-fold rise of the biliary melibiose/rhamnose ratio, the accepted paracellular permeability indicator. Both, the renal clearance of melibiose and the urinary melibiose/rhamnose ratio remained uninfluenced by cholestasis.

CONCLUSION

The present study is the first to describe in detail pharmacokinetic parameters and the biliary excretion of melibiose and rhamnose in healthy and cholestatic rats. The altered melibiose/rhamnose biliary excretion ratio in BDO rats indicates that the test is able to detect the impairment of the blood-biliary barrier in acute extrahepatic cholestasis.

The role of matrix stiffness in regulating cell behavior

Matrix stiffness (resistance to deformation), one of the many mechanical forces acting on cells, is increasingly appreciated as an important mediator of cell behavior. It regulates cell signaling broadly, with effects on growth, survival, and motility. Although the stiffness optima for different kinds of adherent cells vary widely, it is generally true that cell proliferation and differentiation increase with the stiffness of the matrix. This review summarizes recent data exploring the nature of matrix stiffness, mechanotransducers, and the many effects of changes in stiffness on cell function. Particular mention is made of data suggesting that cells of the liver are mechanosensitive, highlighting the potential importance of these findings in understanding the biology of normal and diseased liver.

Gene modulation for treating liver fibrosis

Despite tremendous progress in our understanding of fibrogenesis, injury stimuli process, inflammation, and hepatic stellate cell (HSC) activation, there is still no standard treatment for liver fibrosis. Delivery of small molecular weight drugs, proteins, and nucleic acids to specific liver cell types remains a challenge due to the overexpression of extracellular matrix (ECM) and consequent closure of sinusoidal gaps. In addition, activation of HSCs and subsequent release of inflammatory cytokines and infiltration of immune cells are other major obstacles to the treatment of liver fibrosis. To overcome these barriers, different therapeutic approaches are being investigated. Among them, the modulation of certain aberrant protein production is quite promising for treating liver fibrosis. In this review, we describe the mechanism of antisense, antigene, and RNA interference (RNAi) therapies and discuss how the backbone modification of oligonucleotides affects their in vivo stability, biodistribution, and bioactivity. Strategies for delivering these nucleic acids to specific cell types are discussed. This review critically addresses various insights developed with each individual strategy and for multipronged approaches, which will be helpful in achieving more effective outcomes.

Recent progress in histochemistry

The progress in discerning the structure and function of cells and tissues in health and disease has been achieved to a large extent by the continued development of new reagents for histochemistry, the improvement of existing techniques and new imaging techniques. This review will highlight some advancements made in these fields.

The histochemistry and cell biology vade mecum: a review of 2005–2006

The procurement of new knowledge and understanding in the ever expanding discipline of cell biology continues to advance at a breakneck pace. The progress in discerning the physiology of cells and tissues in health and disease has been driven to a large extent by the continued development of new probes and imaging techniques. The recent introduction of semi-conductor quantum dots as stable, specific markers for both fluorescence light microscopy and electron microscopy, as well as a virtual treasure-trove of new fluorescent proteins, has in conjunction with newly introduced spectral imaging systems, opened vistas into the seemingly unlimited possibilities for experimental design. Although it oftentimes proves difficult to predict what the future will hold with respect to advances in disciplines such as cell biology and histochemistry, it is facile to look back on what has already occurred. In this spirit, this review will highlight some advancements made in these areas in the past 2 years.