Extracorporeal liver support

Extracorporeal liver support techniques: a comparison

ExtraCorporeal Liver Support (ECLS) systems were developed with the aim of supporting the liver in its detoxification function by clearing the blood from hepatic toxic molecules. We conducted a retrospective comparative analysis on patients presenting with liver failure who were treated with different extracorporeal techniques in our intensive care unit to evaluate and compare their detoxification abilities. To verify the effectiveness of the techniques, mass balance (MB) and adsorption per hour were calculated for total bilirubin (TB), direct bilirubin (DB), and bile acids (BA) from the concentrations measured. MB represents the total amount (mg or mcMol) of a molecule removed from a solution and is the only representative parameter to verify the purification effectiveness of one system as it is not affected by the continuous production of the molecules, released in the circulation from the tissues, as it is the case for the reduction rate (RR). The total adsorption per hour is calculated by the ratio between MB and the time duration and shows the adsorption ability in an hour. Our comparative study shows the superior adsorption capability of CytoSorb system regarding TB, DB, and BA, evaluated through the MB and adsorption per hour, in comparison with CPFA, MARS, Prometheus, and PAP. In conclusion, as extracorporeal purification in liver failure could be considered useful for therapeutic purposes, Cytosorb, being more performing than other systems considered, could represent the device of first choice.

Extracorporeal organ support and the kidney

The concept of extracorporeal organ support (ECOS) encompasses kidney, respiratory, cardiac and hepatic support. In an era of increasing incidence and survival of patients with single or multiple organ failure, knowledge on both multiorgan crosstalk and the physiopathological consequences of extracorporeal organ support have become increasingly important. Immerse within the cross-talk of multiple organ failure (MOF), Acute kidney injury (AKI) may be a part of the clinical presentation in patients undergoing ECOS, either as a concurrent clinical issue since the very start of ECOS or as a de novo event at any point in the clinical course. At any point during the clinical course of a patient with single or multiple organ failure undergoing ECOS, renal function may improve or deteriorate, as a result of the interaction of multiple factors, including multiorgan crosstalk and physiological consequences of ECOS. Common physiopathological ways in which ECOS may influence renal function includes: 1) multiorgan crosstalk (preexisting or de-novo 2)Hemodynamic changes and 3) ECOS-associated coagulation abnormalities and 3) Also, cytokine profile switch, neurohumoral changes and toxins clearance may contribute to the expected physiological changes related to ECOS. The main objective of this review is to summarize the described mechanisms influencing the renal function during the course of ECOS, including renal replacement therapy, extracorporeal membrane oxygenation/carbon dioxide removal and albumin dialysis.

Aggregate Removal Nanofiltration of Human Serum Albumin Solution Using Nanocellulose-Based Filter Paper

This study is dedicated to the rapid removal of protein aggregates and viruses from plasma-derived human serum albumin (HSA) product to reduce the risk of viral contamination and increase biosafety. A two-step filtration approach was implemented to first remove HSA aggregates and then achieve high model virus clearance using a nanocellulose-based filter paper of different thicknesses, i.e., 11 μm (prefilter) and 22 μm (virus filter) at pH 7.4 and room temperature. The pore size distribution of these filters was characterized by nitrogen gas sorption analysis. Dynamic light scattering (DLS) and size-exclusion high performance liquid chromatography (SE-HPLC) were performed to analyze the presence of HSA aggregates in process intermediates. The virus filter showed high clearance of a small-size model virus, i.e., log₁₀ reduction value (LRV) > 5, when operated at 3 and 5 bar, but a distinct decrease in LRV was detected at 1 bar, i.e., LRV 2.65–3.75. The throughput of HSA was also dependent on applied transmembrane pressure as was seen by Vmax values of 110 ± 2.5 L m⁻² and 63.6 ± 5.8 L m⁻² at 3 bar and 5 bar, respectively. Protein loss was low, i.e., recovery > 90%. A distribution of pore sizes between 40 nm and 60 nm, which was present in the prefilter and absent in the virus filter, played a crucial part in removing the HSA aggregates and minimizing the risk of virus filter fouling. The presented results enable the application of virus removal nanofiltration of HSA in bioprocessing as an alternative to virus inactivation methods based, e.g., on heat treatment.

Extracorporeal liver support: trending epidemiology and mortality - a nationwide database analysis 2007-2015

Background

Extracorporeal liver support therapies (ELS) are technical options (for bridge-to-recovery as well as bridge-to-transplant) in patients with acute liver dysfunction (e.g. acute liver failure (ALF), acute-on chronic liver failure (AoCLF) or decompensated chronic liver disease (decomp. CLD)) to reduce effects of failing hepatic detoxification functions. The present study investigates the real-life utilization of ELS (annual incidences), mortality rates as well as data regarding specific populations of liver transplantation in Germany.

Methods

Data on patient cases receiving extracorporeal liver support therapy were identified in a nationwide data set from the Federal statistical Office of Germany from 1 January 2007 through 31 December 2015 and analyzed regarding in-hospital mortality, age- and sex-specific distribution and use of ELS in the context of liver transplantation. Mortality rates in patients with primary acute liver dysfunction and secondary acute liver dysfunction (in the context of cardiothoracic surgery) were evaluated.

Results

Annual incidences of ELS use remained stable between 0.39/100.000 in 2007 and 0.47/100.000 ELS in 2015. In-hospital mortality rate was 51.49% in the 2886 evaluated patient cases. Mortality was higher in men (56.04%) than in women (43.70) in the observed time period between 2007 and 2015. ELS utilization and case-related liver transplantation rates were low (12.47%). Since 2012, the annual numbers for ELS therapy in cardiosurgical patients exceeded the frequency of ELS utilization in cases of primary liver dysfunction (mortality rates: 68.39% versus 40.63%).

Conclusions

ELS utilization remained stable between 2007 and 2015. Mortality rates are high in this patient population of acute liver dysfunction, especially in combination with case-related cardiothoracic surgery. ELS is rarely used in the setting of liver transplantation. In 2015, more than 50% of all ELS cases in Germany were performed in the context of cardiothoracic surgery.

Effects of therapeutic plasma exchange on liver function test and coagulation parameters in acute liver failure patients

Background

Currently the treatment of choice for critical liver failure is liver transplantation. Liver failure is treated conservatively until a matching liver donor becomes available. The therapeutic plasma exchange (TPE) plays an important role as a bridge to transplantation by removing accumulated toxins from patient plasma, as well as restoring the coagulation profile.

Method

This was a retrospective study on critically ill liver disease patients who underwent TPE from January 2012 to September 2015. The data were collected for the analyses of coagulation parameters, liver function tests, renal function tests, model for end-stage liver disease (MELD) scores, mortality, and hospital stay.

Results

In the study duration, a total of 45 patients with critical liver disease underwent therapeutic plasma exchange. The TPE resulted in a statistically significant reduction in the bilirubin level, aspartate aminotransferase (AST), alanine aminotransferase (ALT), prothrombin time (PT), international normalized ratio (INR), serum ferritin level and MELD scores. Higher MELD scores in both pre- and post-TPE were associated with higher mortality during the hospital stay.

Conclusion

The TPE is safe and well-tolerated, and it improves coagulation profile and liver function tests in critically ill liver disease patients, but the overall survival remains low.

CAAP48, a New Sepsis Biomarker, Induces Hepatic Dysfunction in an in vitro Liver-on-Chip Model

Sepsis is a leading cause of mortality in the critically ill, characterized by life-threatening organ dysfunctions due to dysregulation of the host response to infection. Using mass spectrometry, we identified a C-terminal fragment of alpha-1-antitrypsin, designated CAAP48, as a new sepsis biomarker that actively participates in the pathophysiology of sepsis. It is well-known that liver dysfunction is an early event in sepsis-associated multi-organ failure, thus we analyzed the pathophysiological function of CAAP48 in a microfluidic-supported in vitro liver-on-chip model. Hepatocytes were stimulated with synthetic CAAP48 and several control peptides. CAAP48-treatment resulted in an accumulation of the hepatocyte-specific intracellular enzymes aspartate- and alanine-transaminase and impaired the activity of the hepatic multidrug resistant-associated protein 2 and cytochrome P450 3A4. Moreover, CAAP48 reduced hepatic expression of the multidrug resistant-associated protein 2 and disrupted the endothelial structural integrity as demonstrated by reduced expression of VE-cadherin, F-actin and alteration of the tight junction protein zonula occludens-1, which resulted in a loss of the endothelial barrier function. Furthermore, CAAP48 induced the release of adhesion molecules and pro- and anti-inflammatory cytokines. Our results show that CAAP48 triggers inflammation-related endothelial barrier disruption as well as hepatocellular dysfunction in a liver-on-chip model emulating the pathophysiological conditions of inflammation. Besides its function as new sepsis biomarker, CAAP48 thus might play an important role in the development of liver dysfunction as a consequence of the dysregulated host immune-inflammatory response in sepsis.

Novel use of Cytosorb™ haemadsorption to provide biochemical control in liver impairment

We describe the use of Cytosorb™, a synthetic extracorporeal haemoperfusion adsorption column, in the management of two patients with drug induced cholestasis and a third with alcoholic hepatitis and subsequent acute on chronic liver failure. Cytosorb was used in these patients to remove bilirubin and bile acids by supporting impaired excretory hepatic function, alleviating symptoms with the intention of serving as a bridge to endogenous recovery. The first two cases demonstrate favourable biochemical and symptomatic responses; the third case demonstrated a good biochemical response but subsequently died from the complications of multiple organ failure. These cases suggest Cytosorb™ be evaluated as an adjunct to support liver excretory functions in other arenas, such as acute liver failure or overdose. It remains unclear whether extracorporeal therapies removing liver toxins allow faster or more complete spontaneous recovery of endogenous function.

Functional hepatocyte clusters on bioactive blend silk matrices towards generating bioartificial liver constructs

The creation of in vitro functional hepatic tissue simulating micro-environmental niche of native liver is a keen area of research due to its demand in bioartificial liver (BAL) and cell-based tissue engineering. Here, we investigated the potential of novel blend (BA) silk scaffold fabricated by blending mulberry (Bombyx mori, BM) silk fibroin with cell adhesion motif (RGD) rich non-mulberry (Antheraea assamensis, AA) silk fibroin, in generating a functional liver construct. Three-dimensional (3D) porous silk scaffolds (BM, AA and BA) were physico-chemically characterized and functionally evaluated using human hepatocarcinoma cells (HepG2) and primary neonatal rat hepatocytes. The growth and distribution of hepatocytes within the scaffolds were tracked by FESEM, alamar blue proliferation assay and live/dead staining. Hemocompatible BA scaffolds supported the formation of high density hepatocyte clusters, facilitating cell-matrix and cell-cell interactions. Blend scaffolds evinced enhanced liver-specific functions of cultured hepatocytes in terms of albumin synthesis, urea synthesis and cytochrome P450 enzyme activity over 21 days. Subcutaneous implantation of scaffolds demonstrated minimal macrophage infiltration in blend scaffolds. These findings substantiate that the integral property of blend (BA) scaffold offers a befitting environment by influencing spheroidal growth of hepatocytes with enhanced biological activity. Collectively, the present study provides a new 3D bio-matrix niche for growing functional liver cells that would have future prospects in BAL as well as regenerative medicine.

STATEMENT OF SIGNIFICANCE

An end stage liver disease called cirrhosis perturbs the self-healing ability and physiological functions of liver. Due to the scarcity of healthy donors, a functional in vitro hepatic construct retaining the liver-specific functions is in great demand for its prospects in bioartificial liver (BAL) and cell-based tissue engineering. Physicochemical attributes of a matrix influence the behavior of cultured hepatocytes in terms of attachment, morphology and functionality. Mulberry and non-mulberry silk fibroin presents unique amino acid sequence with difference in hydrophobicity and crystallinity. Considering this, the present study focuses on the development of a suitable three-dimensional (3D) bioactive matrix incorporating both mulberry silk fibroin and cell adhesion motif (RGD) rich non-mulberry silk fibroin. Porous silk blend scaffolds facilitated the formation of hepatocyte clusters with enhanced liver-specific functions emphasizing both cell-cell and cell-matrix interactions. Hemocompatibility and integral property of blend scaffolds offers a biological niche for seeding functional liver cells that would have future prospects in biohybrid devices.

Removal of stabilizers from human serum albumin by adsorbents and dialysis used in blood purification

INTRODUCTION

Human serum albumin (HSA) is a monomeric multi-domain protein that possesses an extraordinary binding capacity. It plays an important role in storing and transporting endogenous substances, metabolites, and drugs throughout the human circulatory system. Clinically, HSA is used to treat a variety of diseases such as hypovolemia, shock, burns, hemorrhage, and trauma in critically ill patients. Pharmaceutical-grade HSA contains the stabilizers sodium caprylate and N-acetyltryptophanate to protect the protein from oxidative stress and to stabilize it for heat treatment which is applied for virus inactivation.

MATERIAL AND METHODS

The aim of this study was to determine if the two stabilizers can be depleted by adsorbent techniques. Several, adsorbents, some of them are in clinical use, were tested in batch and in a dynamic setup for their ability to remove the stabilizers. Furthermore, the removal of the stabilizers was tested using a pediatric high flux dialyzer.

RESULTS

The outcome of this study shows that activated charcoal based adsorbents are more effective in removal of N-acetylthryptophanate, whereas polystyrene based adsorbents are better for the removal of caprylate from HSA solutions. An adsorbent cartridge which contains a mix of activated charcoal and polystyrene based material could be used to remove both stabilizers effectively. After 4 hours treatment with a high flux dialyzer, N-acetyltryptophanate was totally removed whereas 20% of caprylate remained in the HSA solution.

From organoids to organs: Bioengineering liver grafts from hepatic stem cells and matrix

Due to the complex function and structure of the liver, resourceful solutions for treating end-stage liver disease are required. Currently, liver transplantation is the only curative therapeutic option. However, due to a worldwide donor shortage, researchers have been looking in other fields for alternative sources of transplantable liver tissue. Recent advances in our understanding of liver physiology, stem cell and matrix biology, have accelerated tissue engineering research. Most notable is the discovery of a culture system to grow liver-like organoids from human hepatic stem cells. The extensive expansion capacity of these stem cells has contributed greatly to the availability of hepatocyte-like cells for tissue engineering. In addition, new techniques are explored to obtain biological liver scaffolds from full size donor organs. This review summarizes these state-of-art techniques which may lay the groundwork towards re-creating transplantable tissue from autologous or allogenic stem cells in the coming decade.

Small-for-Size Syndrome: Bridging the Gap Between Liver Transplantation and Graft Recovery

In living donor liver transplantation, optimal graft size is estimated from values like graft volume/standard liver volume and graft/recipient body weight ratio but the final functional hepatic mass is influenced by other donor and recipient factors. Grafts with insufficient functional hepatic mass can produce a life-threatening condition with rapidly progressive liver failure called small-for-size syndrome (SFSS). Diagnosis of SFSS requires careful surveillance for signs of inadequate hepatocellular function, residual portal hypertension, and systemic inflammation that suggest rapidly progressive liver failure. Early diagnosis, symptom control, and addressing the cause of SFSS may prevent the need for retransplantation. With increased attention to avoiding donor risk, intensivists will be confronted with more SFSS recipients. In this review, we aim to outline a systematic approach to the medical management of patients with SFSS by providing a concise synopsis of general supportive care—neurological, cardiovascular, and renal support, mechanical ventilation, nutritional support, infection control, and tailored immunosuppression—with an aim to avoid end-organ damage or death and a review of current interventions including liver support devices, portal flow modulating drugs, and other experimental interventions that aim to preserve existing hepatic mass and improve conditions for hepatic regeneration. We examine evidence for SFSS interventions to provide the reader with information that may assist in clinical decision making. Points of controversy in care are purposefully highlighted to identify areas where additional experimental work is still needed. A full understanding of the pathophysiology of SFSS and measures to support liver regeneration will guide effective management.

Alleviating liver failure conditions using an integrated hybrid cryogel based cellular bioreactor as a bioartificial liver support

Conventionally, some bioartificial liver devices are used with separate plasmapheresis unit to separate out plasma from whole blood and adsorbent column to detoxify plasma before it passes through a hepatocytes-laden bioreactor. We aim to develop a hybrid bioreactor that integrates the separate modules in one compact design improving the efficacy of the cryogel based bioreactor as a bioartificial liver support. A plasma separation membrane and an activated carbon cloth are placed over a HepG2-loaded cryogel scaffold in a three-chambered bioreactor design. This bioreactor is consequently connected extracorporeally to a rat model of acute liver failure for 3 h and major biochemical parameters studied. Bilirubin and aspartate transaminase showed a percentage decrease of 20-60% in the integrated bioreactor as opposed to 5-15% in the conventional setup. Urea and ammonia levels which showed negligible change in the conventional setup increase (40%) and decrease (18%), respectively in the integrated system. Also, an overall increase of 5% in human albumin in rat plasma indicated bioreactor functionality in terms of synthetic functions. These results were corroborated by offline evaluation of patient plasma. Hence, integrating the plasmapheresis and adsorbent units with the bioreactor module in one compact design improves the efficacy of the bioartificial liver device.

Biomaterials and Culture Technologies for Regenerative Therapy of Liver Tissue

Regenerative approach has emerged to substitute the current extracorporeal technologies for the treatment of diseased and damaged liver tissue. This is based on the use of biomaterials that modulate the responses of hepatic cells through the unique matrix properties tuned to recapitulate regenerative functions. Cells in liver preserve their phenotype or differentiate through the interactions with extracellular matrix molecules. Therefore, the intrinsic properties of the engineered biomaterials, such as stiffness and surface topography, need to be tailored to induce appropriate cellular functions. The matrix physical stimuli can be combined with biochemical cues, such as immobilized functional groups or the delivered actions of signaling molecules. Furthermore, the external modulation of cells, through cocultures with nonparenchymal cells (e.g., endothelial cells) that can signal bioactive molecules, is another promising avenue to regenerate liver tissue. This review disseminates the recent approaches of regenerating liver tissue, with a focus on the development of biomaterials and the related culture technologies.

Engineered biomimetic nanoabsorbent for cellular detoxification of chemotherapeutics

An approach to reduce the nonspecific cytotoxicity of chemotherapeutics has been put-forth using a biomimetic nanoabsorbent (NAb) as a detoxifying agent.

Albumin Dialysis for Liver Failure: A Systematic Review

Albumin dialysis is the best-studied extracorporeal nonbiologic liver support system as a bridge or destination therapy for patients with liver failure awaiting liver transplantation or recovery of liver function. We performed a systematic review to examine the efficacy and safety of 3 albumin dialysis systems (molecular adsorbent recirculating system [MARS], fractionated plasma separation, adsorption and hemodialysis [Prometheus system], and single-pass albumin dialysis) in randomized trials for supportive treatment of liver failure. PubMed, Ovid, EMBASE, Cochrane's Library, and ClinicalTrials.gov were searched. Two authors independently screened citations and extracted data on patient characteristics, quality of reports, efficacy, and safety end points. Ten trials (7 of MARS and 3 of Prometheus) were identified (620 patients). By meta-analysis, albumin dialysis achieved a net decrease in serum total bilirubin level relative to standard medical therapy of 8.0 mg/dL (95% confidence interval [CI], -10.6 to -5.4) but not in serum ammonia or bile acids. Albumin dialysis achieved an improvement in hepatic encephalopathy relative to standard medical therapy with a risk ratio of 1.55 (95% CI, 1.16-2.08) but had no effect survival with a risk ratio of 0.95 (95% CI, 0.84-1.07). Because of inconsistency in the reporting of adverse events, the safety analysis was limited but did not demonstrate major safety concerns. Use of albumin dialysis as supportive treatment for liver failure is successful at removing albumin-bound molecules, such as bilirubin and at improving hepatic encephalopathy. Additional experience is required to guide its optimal use and address safety concerns.

Albumin dialysis in artificial liver support systems: open-loop or closed-loop dialysis mode?

In artificial liver support systems, the open-loop albumin dialysis mode (OLM) is usually used to remove protein-bound toxins from the blood of patients with liver failure. However, there is still interest in the closed-loop albumin dialysis mode (CLM) because this mode may enable not only the regeneration and reuse of albumin but also the miniaturization of artificial liver systems. In this article, we compared the two modes under a fixed amount of albumin in dialysate experimentally and theoretically. The results show that according to the detoxification efficiency in the 3 hour dialysis for removing albumin-bound bilirubin, CLM is better than OLM. The usage efficiency of albumin in CLM is also higher. Moreover, the advantage of CLM is more significant when the concentration of bilirubin in blood is lower. Under a given amount of albumin in dialysate, if the concentration of bilirubin in blood is high, one may further increase the performance of CLM by means of increasing the flow rate of the albumin dialysate or using the highly concentrated albumin dialysate.