Management of chronic liver failure until liver transplantation

Blood-Bile Barrier: Morphology, Regulation, and Pathophysiology

The term blood-bile barrier (BBlB) refers to the physical structure within a hepatic lobule that compartmentalizes and hence segregates sinusoidal blood from canalicular bile. Thus, this barrier provides physiological protection in the liver, shielding the hepatocytes from bile toxicity and restricting the mixing of blood and bile. BBlB is primarily composed of tight junctions; however, adherens junction, desmosomes, gap junctions, and hepatocyte bile transporters also contribute to the barrier function of the BBlB. Recent findings also suggest that disruption of BBlB is associated with major hepatic diseases characterized by cholestasis and aberrations in BBlB thus may be a hallmark of many chronic liver diseases. Several molecular signaling pathways have now been shown to play a role in regulating the structure and function and eventually contribute to regulation of the BBlB function within the liver. In this review, we will discuss the structure and function of the BBlB, summarize the methods to assess the integrity and function of BBlB, discuss the role of BBlB in liver pathophysiology, and finally, discuss the mechanisms of BBlB regulation. Collectively, this review will demonstrate the significance of the BBlB in both liver homeostasis and hepatic dysfunction.

Dysregulated Bile Transporters and Impaired Tight Junctions During Chronic Liver Injury in Mice

BACKGROUND & AIMS

Liver fibrosis, hepatocellular necrosis, inflammation, and proliferation of liver progenitor cells are features of chronic liver injury. Mouse models have been used to study the end-stage pathophysiology of chronic liver injury. However, little is known about differences in the mechanisms of liver injury among different mouse models because of our inability to visualize the progression of liver injury in vivo in mice. We developed a method to visualize bile transport and blood-bile barrier (BBlB) integrity in live mice.

METHODS

C57BL/6 mice were fed a choline-deficient, ethionine-supplemented (CDE) diet or a diet containing 0.1% 3,5-diethoxycarbonyl-1, 4-dihydrocollidine (DDC) for up to 4 weeks to induce chronic liver injury. We used quantitative liver intravital microscopy (qLIM) for real-time assessment of bile transport and BBlB integrity in the intact livers of the live mice fed the CDE, DDC, or chow (control) diets. Liver tissues were collected from mice and analyzed by histology, immunohistochemistry, real-time polymerase chain reaction, and immunoblots.

RESULTS

Mice with liver injury induced by a CDE or a DDC diet had breaches in the BBlB and impaired bile secretion, observed by qLIM compared with control mice. Impaired bile secretion was associated with reduced expression of several tight-junction proteins (claudins 3, 5, and 7) and bile transporters (NTCP, OATP1, BSEP, ABCG5, and ABCG8). A prolonged (2-week) CDE, but not DDC, diet led to re-expression of tight junction proteins and bile transporters, concomitant with the reestablishment of BBlB integrity and bile secretion.

CONCLUSIONS

We used qLIM to study chronic liver injury, induced by a choline-deficient or DDC diet, in mice. Progression of chronic liver injury was accompanied by loss of bile transporters and tight junction proteins.

Metabolite variations between acute-on-chronic liver failure and chronic liver failure caused by hepatitis B virus based on ultra-performance liquid chromatography mass spectrometry

OBJECTIVE

The present study aims to compare serum metabolite alterations between acute-on-chronic liver failure (ACLF) and chronic liver failure (CLF), and find the specific biomarkers associated with the diseases.

METHODS

Serum samples were collected from patients with ACLF (n=76) and CLF (n=56) as well as healthy individuals (n=20) and assayed by ultra-performance liquid chromatography mass spectrometry (UPLC-MS). The acquired data was analyzed using principal components analysis (PCA) and partial least squares discriminate analysis (PLS-DA).

RESULTS

The PLS-DA model with satisfactory explanatory and predictive ability (R2=0.979, Q2=0.918) is capable of discriminate ACLF patients from CLF patients. Significant difference in the metabolomics among the three groups was observed, metabolites that decreased significantly in the serum of ACLF and CLF included phosphatidylcholines (PCs) and lysophosphatidylcholines (LPCs), whereas conjugated bile acids (GCDCA, GUDCA) increased significantly, these metabolites considered as common biomarkers of liver failure. Linoleyl carnitine showed significant increase in CLF compared with controls while no significant change was observed in ACLF, it could be special biomarkers of ACLF and CLF.

CONCLUSION

Metabolomics based on ultra-performance liquid chromatography mass spectrometry provide a new way to diagnose and reveal the pathogenesis of ACLF and CLF.

Management and prognosis of acute liver failure in children

Although the etiologies of pediatric acute liver failure (ALF) are diverse, ultimate pathophysiologic pathways and management challenges for these disorders, usually lethal in the pre-transplant era, are similar. This review considers particularly the mechanisms of, and monitoring for, intracranial hypertension and coagulopathy; summarizes detailed advice for management of the ALF-associated failures of multiple body systems; and reviews the variety of prognostic scores available to guide management and assist in choosing the patients most apt to benefit from liver transplantation and the optimal timing for such transplantation.

[Evaluation of extracorporeal liver support systems in the treatment of liver failure. A systematic review]

OBJECTIVE

To evaluate the safety and efficacy of the MARS and Prometheus extracorporeal liver support systems in the treatment of liver failure.

DESIGN

We performed a systematic review of the literature from January 1999 to June 2009 in the Medline, Embase, HTA, DARE, NHSEED, Cochrane Library Plus, Clinical Trials Registry and HSRPROJ databases. Study selection was based on a series of previously established inclusion criteria related to the study design, population, type of intervention, language, and outcome measures.

PATIENTS AND INTERVENTIONS

Patients with acute liver failure or acute exacerbations of chronic liver failure treated with the MARS or Prometheus systems.

OUTCOME MEASURES

Data on safety, long-term survival, clinical effects and biochemical and hemodynamic variables.

RESULTS

We selected 22 studies evaluating the safety and efficacy of the MARS and Prometheus systems. Adequate evaluation of these techniques was hampered by the heterogeneity of the studies and their methodological limitations.

CONCLUSIONS

Extracorporeal liver support systems are able to purify both hydrosoluble and protein-bound substances. However, current data show that only the MARS system reduces mortality in acute liver failure and in acute exacerbations of chronic liver failure, although this reduction is non-significant. These techniques can be considered safe, with adverse effects similar to those of the control group. Their main indication is severe liver failure, for short periods while the liver recovers or a liver transplant becomes available.