Alexander I. Aspinall

CX3CR1 and vascular adhesion protein‐1‐dependent recruitment of CD16+ monocytes across human liver sinusoidal endothelium

The liver contains macrophages and myeloid dendritic cells (mDCs) that are critical for the regulation of hepatic inflammation. Most hepatic macrophages and mDCs are derived from monocytes recruited from the blood through poorly understood interactions with hepatic sinusoidal endothelial cells (HSECs). Human CD16+ monocytes are thought to contain the precursor populations for tissue macrophages and mDCs. We report that CD16+ cells localize to areas of active inflammation and fibrosis in chronic inflammatory liver disease and that a unique combination of cell surface receptors promotes the transendothelial migration of CD16+ monocytes through human HSECs under physiological flow. CX3CR1 activation was the dominant pertussis‐sensitive mechanism controlling transendothelial migration under flow, and expression of the CX3CR1 ligand CX3CL1 is increased on hepatic sinusoids in chronic inflammatory liver disease. Exposure of CD16+ monocytes to immobilized purified CX3CL1 triggered β1‐integrin‐mediated adhesion to vascular cell adhesion molecule‐1 and induced the development of a migratory phenotype. Following transmigration or exposure to soluble CX3CL1, CD16+ monocytes rapidly but transiently lost expression of CX3CR1. Adhesion and transmigration across HSECs under flow was also dependent on vascular adhesion protein‐1 (VAP‐1) on the HSECs. Conclusion: Our data suggest that CD16+ monocytes are recruited by a combination of adhesive signals involving VAP‐1 and CX3CR1 mediated integrin‐activation. Thus a novel combination of surface molecules, including VAP‐1 and CX3CL1 promotes the recruitment of CD16+ monocytes to the liver, allowing them to localize at sites of chronic inflammation and fibrosis. (Hepatology 2010)

Rituximab for the treatment of patients with autoimmune hepatitis who are refractory or intolerant to standard therapy

BACKGROUND Although most patients with autoimmune hepatitis (AIH) respond to treatment with prednisone and⁄or azathioprine, some patients are intolerant or refractory to standard therapy. Rituximab is an anti-CD20 monoclonal antibody that depletes B cells and has demonstrated efficacy in other autoimmune conditions. AIMS To evaluate the safety and efficacy of rituximab in patients with refractory AIH in an open-label, single-centre pilot study. METHODS Six patients with definite, biopsy-proven AIH who failed prednisone and azathioprine treatment received two infusions of rituximab 1000 mg two weeks apart and were followed for 72 weeks. RESULTS Rituximab was well tolerated with no serious adverse events. By week 24, mean (± SD) aspartate aminotransferase (AST) levels had significantly improved (90.0±23.3 U⁄L versus 31.3±4.2 U⁄L; P=0.03) and mean immunoglobulin G levels had fallen (16.4±2.0 g⁄L versus 11.5±1.1 g⁄L; P=0.056). The prednisone dose was weaned in three of four subjects, with one subject flaring after steroid withdrawal. Inflammation grade improved in all four subjects who underwent repeat liver biopsy at week 48. Regulatory T cell levels examined by FoxP3 immunohistochemistry paralleled inflammatory activity and did not increase on follow-up biopsies. There was no significant change in serum chemokine or cytokine levels from baseline to week 24 (n=5), although interferon-gamma-induced protein 10 levels improved in three of five subjects. CONCLUSIONS Rituximab was safe, well tolerated and resulted in biochemical improvement in subjects with refractory AIH. These results support further investigation of rituximab as a treatment for AIH.

Gender, renal function, and outcomes on the liver transplant waiting list: Assessment of revised MELD including estimated glomerular filtration rate

BACKGROUND & AIMS The Model for End-Stage Liver Disease (MELD) allocation system for liver transplantation (LT) may present a disadvantage for women by including serum creatinine, which is typically lower in females. Our objectives were to investigate gender disparities in outcomes among LT candidates and to assess a revised MELD, including estimated glomerular filtration rate (eGFR), for predicting waiting list mortality. METHODS Adults registered for LT between 2002 and 2007 were identified using the UNOS database. We compared components of MELD, MDRD-derived eGFR, and the 3-month probability of LT and death between genders. Discrimination of MELD, MELDNa, and revised models including eGFR for mortality were compared using c-statistics. RESULTS A total of 40,393 patients (36% female) met the inclusion criteria; 9% died and 24% underwent LT within 3 months of listing. Compared with men, women had lower median serum creatinine (0.9 vs. 1.0 mg/dl), eGFR (72 vs. 83 ml/min/1.73 m(2)), and mean MELD (16.5 vs. 17.2; all p <0.0005), but within most MELD strata, had higher bilirubin and INR. After adjusting for relevant covariates including creatinine and body weight, women were less likely than men to receive a LT (hazard ratio [HR] 0.85; 95% CI 0.79-0.87) and had greater 3-month mortality (HR 1.13; 95% CI 1.05-1.21). Revision of MELD and MELDNa to include eGFR did not improve discrimination for 3-month mortality (c-statistics: MELD 0.896, MELD-eGFR 0.894, MELDNa 0.911, MELDNa-eGFR 0.905). CONCLUSIONS Women are disadvantaged under MELD potentially due to its inclusion of creatinine. However, since including eGFR in MELD does not improve mortality prediction, alternative refinements are necessary.

Revision of MELD to Include Serum Albumin Improves Prediction of Mortality on the Liver Transplant Waiting List

Background Allocation of donor livers for transplantation in most regions is based on the Model for End-Stage Liver Disease (MELD) or MELD-sodium (MELDNa). Our objective was to assess revisions to MELD and MELDNa that include serum albumin for predicting waiting list mortality. Methods Adults registered for liver transplantation in the United States (2002–2007) were identified from the United Network for Organ Sharing (UNOS) database. Cox regression was used to determine the association between serum albumin and 3-month mortality, and to derive revised MELD and MELDNa scores incorporating albumin (‘MELD-albumin’ and ‘5-variable MELD [5vMELD]’). Results Among 40,393 patients, 9% died and 24% underwent transplantation within 3 months of listing. For serum albumin concentrations between 1.0 and 4.0 g/dL, a linear, inverse relationship was observed between albumin and 3-month mortality (adjusted hazard ratio per 1 g/dL reduction in albumin: 1.44; 95% CI 1.35–1.54). The c-statistics for 3-month mortality of MELD-albumin and MELD were 0.913 and 0.896, respectively (P<0.001); 5vMELD was superior to MELDNa (c-statistics 0.922 vs. 0.912, P<0.001). The potential benefit of 5vMELD was greatest in patients with low MELD (<15). Among low MELD patients who died, 27% would have gained ≥10 points with 5vMELD over MELD versus only 4–7% among low MELD survivors and high MELD (≥15) candidates (P<0.0005). Conclusion Modification of MELD and MELDNa to include serum albumin is associated with improved prediction of waiting list mortality. If validated and shown to be associated with reduced mortality, adoption of 5vMELD as the basis for liver allograft allocation may improve outcomes on the liver transplant waiting list.

Validation of the five‐variable Model for End‐stage Liver Disease (5vMELD) for prediction of mortality on the liver transplant waiting list

Modifications to the Model for End‐Stage Liver Disease (MELD) have been proposed to improve prioritization of liver transplant (LT) candidates. Using a U.S. database, we derived a revised MELD including sodium and albumin [5‐variable MELD (5vMELD)] that improved prediction of waiting list mortality. Our objectives were to confirm the association between hypoalbuminaemia and mortality and to externally validate 5vMELD in Canadian LT candidates.

Tempo di marzo o di valse: migration kinetics of leucocytes that home to the liver

Lymphocytes are implicated in the pathogenesis of many inflammatory liver diseases. In autoimmune hepatitis, lymphocytes respond to autoantigens on hepatocytes to mediate hepatocellular damage (1) whereas in viral hepatitis, lymphocytes destroy infected hepatocytes that express viral antigens (2). In addition to recruitment in response to a specific antigen or an inflammatory signal, there is evidence that the normal liver is patrolled by lymphocytes and dendritic cells (DC) that provide immune surveillance for the detection and rapid response to infecting pathogens (3, 4). In chronic inflammatory liver disease, these processes are dysregulated and inappropriate inflammation is established that persists, leading to chronic hepatitis, fibrosis and cirrhosis. A common histopathological feature of many chronic liver diseases is an often-striking periportal inflammatory infiltrate. The composition and size of the periportal infiltrate vary according to the aetiology and chronicity of the underlying disease and may include plasma cells, CD4 and CD8 T cells and macrophages. Where the lymphocytes are activated and how they enter and traffic through the liver to draining lymph nodes is poorly understood but is clearly critical to understand not only hepatic immune surveillance but also the pathogenesis of chronic inflammatory liver disease. The situation is made more complex by the liver’s dual blood supply from the portal vein and hepatic artery that converge at the sinusoids. Furthermore, although leucocyte egress from the liver occurs via draining lymphatics, these are not present in the parenchyma but originate within the portal areas. Recently, a second route of egress via the hepatic veins has been proposed. Because of the unique fenestrated endothelium of the liver sinusoids, T lymphocytes can interface with antigen-presenting hepatocytes while in circulation and without exiting the sinusoids (5), and then presumably enter the systemic circulation via the hepatic veins. The molecules governing leucocyte entry into the liver are partially understood and vary by cell type. Previously, it was believed that physical trapping in the low flow and low shear hepatic sinusoids, together with retention mediated by molecules such as intercellular adhesive molecule-1 (ICAM-1), was sufficient to explain leucocyte accumulation in the liver (6). Subsequently, distinct molecular pathways were reported including roles for specific integrins and the endothelial adhesion molecule vascular adhesion protein (VAP)-1 (7, 8). Bonder et al. (9) established in the concanavalin A model of acute liver inflammation that murine Th1 and Th2 lymphocytes use 41 integrin and VAP-1, respectively, to adhere to hepatic sinusoidal endothelium. In humans, CXCR3 activation promotes lymphocyte transendothelial migration in vitro in a model mimicking chronic endothelial inflammation (10, 11) and DC precursors circulating in peripheral blood use fractalkine and VAP-1 to adhere to and transmigrate across the sinusoidal endothelium (A. I. Aspinall and D. H. Adams, unpublished). Thus, both active and passive processes are involved in lymphocyte recruitment (12, 13). Effective immune surveillance requires that lymphocytes and DC recirculate between blood, liver tissue and draining lymph nodes but until the present study there was little documentation of the specific routes taken during entry into, migration through and egress from the liver. Similarly, the rates at which these events occur and the anatomical sites of entry were poorly understood. The elegant study by Xu and colleagues in this issue of Liver International is an important advance (14). The authors describe the recirculation kinetics of lymphocytes, predominantly T cells, through the liver under steady-state conditions in the absence of inflammation or activation. Thoracic ducts were cannulated and the collected cells, which include emigrant cells from the liver and gastrointestinal tract, were fluorescently labelled, re-injected into congenic recipients and cells that homed to the liver and hepatic lymph nodes were identified. The time taken for thoracic duct lymphocytes (TDL) to accumulate in the liver sinusoids, portal tracts and hepatic lymph nodes was 30 min, 3–5 h and 5–8 h respectively. This supports a route of lymphocyte migration from sinusoid to portal tract to hepatic lymph node. A similar route has been shown previously by the same group