Artificial Liver Devices Research Articles

Adsorption behaviors and mechanisms of bilirubin onto charged amorphous carbon surface with and without water by a molecular dynamics simulation

The adsorption of bilirubin onto a carbon surface holds pivotal significance in enhancing bilirubin clearance efficiency within artificial liver devices. We performed molecular dynamics simulations to reveal the adsorption behaviors and mechanisms of bilirubin onto a charged amorphous carbon surface. The hydrogen atoms are used as binding sites facilitating the adsorption of bilirubin molecules onto the uncharged amorphous carbon surface. Conversely, the oxygen atoms are used as binding sites, enhancing bilirubin adsorption on charged amorphous carbon surfaces due to their higher electronegativity. The bilirubin adsorption rate, the mean-squared displacements of bilirubin, and the interaction energy between bilirubin and amorphous carbon increase as the surface charge increases, and the adsorption amount reaches an asymptotic value as the surface charge approaches a certain threshold. In the presence of water, the competitive adsorption between bilirubin and water would occur. The hydration layer formed on charged amorphous carbon surface and the electrostatic and near-wall hydrogen-bond interactions emerge as two pivotal factors influencing bilirubin adsorption. The structured arrangement of hydration water can hinder the bilirubin adsorption, whereas the electrostatic interaction and near-wall hydrogen-bond interaction promote it. The whole competitive adsorption process unfolded in distinct stages of bilirubin adsorption and desorption, and a critical value of surface charge exists for the complete desorption of bilirubin.

Liver Support Devices: Bridge to Transplant or Recovery

Liver failure, whether acute or acute on chronic, is a devastating disease with a very high mortality and morbidity. The recent therapeutic advances, especially liver transplant, have given reason for optimism to the ever-rising population affected by this disease. However, scarcity of organs and lack of resources make this an option that only few can afford. The hunt for an artificial device to assist or replace the functions of the liver has been on the rise since the past 40 years. These devices are classified into artificial and bioartificial liver (BAL) assist devices. Artificial liver devices such as molecular adsorbent recirculating system, Prometheus, single-pass albumin dialysis, and selective plasma filtration therapy are mostly aimed at taking over the blood purification systems of the liver. BAL-assisted devices incorporate hepatic cell lines to obtain a more comprehensive coverage of the complex functions of the liver. These include extracorporeal liver assist device, modular extracorporeal liver support, HepatAssist, and Amsterdam Medical Centre-BAL. Development of an ideal liver assist device has been difficult due to the complexity of the functions of the organ. The initial studies on these devices are promising but inconclusive. Therapeutic plasma exchange seems to have a very favorable profile in the treatment of these patients and has been successfully used in a large number of patients. To arrive at a more definitive conclusion of the usefulness of these devices in the management of liver failure, large randomized multicentric studies with more objective end points need to be carried out. A literature review was performed using PubMed and library searches to collect the recent studies in this regard. This review aims to provide a myopic view of the advances that have been made in the development and usefulness of these liver assist devices.

Adverse events, short- and long-term outcomes of extra corporeal liver therapy in the intensive care unit: 16 years experience with MARS® in a single center

BackgroundMolecular Adsorbent Recirculating System (MARS®) is a non-biological artificial liver device. The benefit risk ratio between uncertain clinical effects and potential adverse events remains difficult to assess. We sought to describe adverse events related to MARS® therapy as well as biological and clinical effects.MethodsAll intensive care unit (ICU) admissions to whom MARS® therapy was prescribed from March 2005 to August 2021 were consecutively and prospectively included. The main endpoint was the incidence of adverse events related to MARS® therapy. Secondary endpoints were the biological and clinical effects of MARS® therapy.ResultsWe reported 180 admissions treated with MARS® therapy. Among the 180 admissions, 56 (31.1%) were for acute-on-chronic liver failure, 32 (17.8%) for acute liver failure, 28 (15.5%) for post-surgery liver failure, 52 (28.9%) for pruritus and 12 (6.7%) for drug intoxication. At least one adverse event occurred in 95 (52.8%) admissions. Thrombocytopenia was the most frequent adverse event which was recorded in 55 admissions (30.6%). Overall, platelets count was 131 (± 95) × 109/L before and 106 (± 72) × 109/L after MARS® therapy (p < .001). After MARS® therapy, total bilirubin was significantly decreased in all groups (p < 0.05). Hepatic encephalopathy significantly improved in both the acute-on-chronic and in the acute liver failure group (p = 0.01). In the pruritus group, pruritus intensity score was significantly decreased after MARS® therapy (p < 0.01).ConclusionIn this large cohort of patients treated with MARS® therapy we report frequent adverse events. Thrombocytopenia was the most frequent adverse event. In all applications significant clinical and biological improvements were shown with MARS® therapy.

How Donor and Surgical Factors Affect the Viability and Functionality of Human Hepatocytes Isolated From Liver Resections.

Liver resections are a significant source of primary human hepatocytes used mainly in artificial liver devices and pharmacological and biomedical studies. However, it is not well known how patient-donor and surgery-dependent factors influence isolated hepatocytes’ yield, viability, and function. Hence, we aimed to analyze the impact of all these elements on the outcome of human hepatocyte isolation.Patients and methodsHepatocytes were isolated from liver tissue from patients undergoing partial hepatectomy using a two-step collagenase method. Hepatocyte viability, cell yield, adhesion, and functionality were measured. In addition, clinical and analytical patient variables were collected and the use or absence of vascular clamping and its type (continuous or intermittent) plus the ischemia times during surgery.ResultsMalignant disease, previous chemotherapy, and male gender were associated with lower hepatocyte viability and isolation cell yields. The previous increase in transaminases was also associated with lower yields on isolation and lower albumin production. Furthermore, ischemia secondary to vascular clamping during surgery was inversely correlated with the isolated hepatocyte viability. An ischemia time higher than 15 min was related to adverse effects on viability.ConclusionSeveral factors correlated with the patient and the surgery directly influence the success of human hepatocyte isolation from patients undergoing liver resection.

Acute liver failure.

Present an outline of acute liver failure, from its definition to its management in critical care, updated with findings of selected newer research. Survival of patients with acute liver failure has progressively improved. Intracranial hypertension complicating hepatic encephalopathy is now much less frequent than in the past and invasive ICP monitoring is now rarely used. Early renal replacement therapy and possibly therapeutic plasma exchange have consolidated their role in the treatment. Further evidence confirms the low incidence of bleeding in these patients despite striking abnormalities in standard tests of coagulation and new findings of abnormalities on thromboelastographic testing. Specific coagulopathy profiles including an abnormal vWF/ADAMTS13 ratio may be associated with poor outcome and increased bleeding risk. Use of N-acetylcysteine in nonparacetamol-related cases remains unsupported by robust clinical evidence. New microRNA-based prognostic markers to select patients for transplantation are described but are still far from widespread clinical applicability; imaging-based prognostication tools are also promising. The use of extracorporeal artificial liver devices in clinical practice is yet to be supported by evidence. Medical treatment of patients with acute liver failure is now associated with significantly improved survival. Better prognostication and selection for emergency liver transplant may further improve care for these patients.

Pluripotent-Stem-Cell-Derived Hepatic Cells: Hepatocytes and Organoids for Liver Therapy and Regeneration.

The liver is a very complex organ that ensures numerous functions; it is thus susceptible to multiple types of damage and dysfunction. Since 1983, orthotopic liver transplantation (OLT) has been considered the only medical solution available to patients when most of their liver function is lost. Unfortunately, the number of patients waiting for OLT is worryingly increasing, and extracorporeal liver support devices are not yet able to counteract the problem. In this review, the current and expected methodologies in liver regeneration are briefly analyzed. In particular, human pluripotent stem cells (hPSCs) as a source of hepatic cells for liver therapy and regeneration are discussed. Principles of hPSC differentiation into hepatocytes are explored, along with the current limitations that have led to the development of 3D culture systems and organoid production. Expected applications of these organoids are discussed with particular attention paid to bio artificial liver (BAL) devices and liver bio-fabrication.

Bioengineering Organs for Blood Detoxification

For patients with severe kidney or liver failure the best solution is currently organ transplantation. However, not all patients are eligible for transplantation and due to limited organ availability, most patients are currently treated with therapies using artificial kidney and artificial liver devices. These therapies, despite their relative success in preserving the patients' life, have important limitations since they can only replace part of the natural kidney or liver functions. As blood detoxification (and other functions) in these highly perfused organs is achieved by specialized cells, it seems relevant to review the approaches leading to bioengineered organs fulfilling most of the native organ functions. There, the culture of cells of specific phenotypes on adapted scaffolds that can be perfused takes place. In this review paper, first the functions of kidney and liver organs are briefly described. Then artificial kidney/liver devices, bioartificial kidney devices, and bioartificial liver devices are focused on, as well as biohybrid constructs obtained by decellularization and recellularization of animal organs. For all organs, a thorough overview of the literature is given and the perspectives for their application in the clinic are discussed.

Generation of Hepatic Stellate Cells from Human Pluripotent Stem Cells Enables In Vitro Modeling of Liver Fibrosis

The development of complex invitro hepatic systems and artificial liver devices has been hampered by the lack of reliable sources for relevant cell types, such as hepatic stellate cells (HSCs). Here we reportefficient differentiation of human pluripotent stem cells into HSC-like cells (iPSC-HSCs). iPSC-HSCsclosely resemble primary human HSCs at the transcriptional, cellular, and functional levels and possess a gene expression profile intermediate between that of quiescent and activated HSCs. Functional analyses revealed that iPSC-HSCs accumulate retinyl esters in lipid droplets and are activated in response to mediators of wound healing, similar to their invivocounterparts. When maintained as 3D spheroids withHepaRG hepatocytes, iPSC-HSCs exhibit a quiescent phenotype but mount a fibrogenic response and secrete pro-collagen in response to known stimuli and hepatocyte toxicity. Thus, this protocol provides a robust invitro system for studying HSC development, modeling liver fibrosis, and drug toxicity screening.

Current Cell-Based Therapies in the Chronic Liver Diseases.

Liver diseases account for one of the leading causes of deaths in global health care. Furthermore, chronic liver failure such as liver cirrhosis is, namely, responsible for these fatal conditions. However, only liver transplantation is an established treatment for this end-stage condition, although the availability of this salvage treatment option is quite limited. Thus, the novel therapy such as artificial liver devices or cellular administration has been regarded as feasible. Especially cellular therapies have been proposed in decades. The technical advancement and progress of understanding of cellulardifferentiation have contributed to the development of basis of cellular therapy. This attractive therapeutic option has been advanced from original embryonic stem cells to more effective cellular fractions such as Muse cells. Indeed several cellular therapies including bone marrow-derived stem cells or peripheral blood-derived stem cells were initiated; the recent most organized clinical trials could not demonstrate its efficacy. Thus, truly innovative cellular therapy is needed to meet the scientific demands, and Muse cell administration is the remaining approach to this. In this article, we will discuss the current development and status of cellular therapy toward chronic liver failure.

The development and status of bioartificial liver

Liver failure is a serious stage during liver disease development of which mobidity is high. There is no effective treatment at present.Artificial liver support system is one of the important methods to treat liver failure which includes non-biological artificial liver, biological artificial liver and hybrid artificial liver. Among the artificial liver devices. The bioartificial liver is the most similar artifical liver device to human liver in terms of detoxification, synthesis and metabolism currently.The complexity of human liver function makes the biological artificial liver facing great challenges in selection of liver seed cells, construction of bioreactor and the best combination with auxiliary device, which leads to the slow development of bioartificial liver. In order to provide theoretical support for the study of bioartificial liver, the current status and its development are reviewed in the following aspects, the source of seed cells, the construction of bioreactor, the combination of auxiliary devices and the clinical application of bioartificial liver in this article.

A Review on Membranes for Clinical Treatment and Drug Delivery in Medical Applications

Membrane processes are used extensively in biomedical applications. This state of the art review presents the main applications including renal kidney, blood filtration, blood oxygenator, artificial liver, artificial pancreas, and drug delivery devices. For well-established treatments like dialysis, plasmapheresis, and blood oxygenator, the techniques are summarized by presenting membranes used, devices, configurations and treatments. The artificial liver and the artificial pancreas are not clinically used and some main aspects related to the development of these devices are given, including configurations and liver or pancreatic cells. Finally, drug delivery devices based on membranes, which are an important area in pharmaceutics, are summarized by focusing on diffusion and transdermal delivery systems, as well as colloids like liposomes and nanocapsules. These colloids with nanometric size are surrounded by a lipidic or polymeric thin membrane which controls drug transfer to the surrounding medium.

Bioartificial Liver Device Based on Induced Pluripotent Stem Cell-Derived Hepatocytes

Decompensated liver disorders require liver transplantation. However, the donor organ shortage is a limiting factor. Harnessing the power of human induced pluripotent stem cell (iPSC) technology in combination with hollow fiber-based bioartificial liver (BAL) device can be beneficial to patients with liver failure. Our goal is to develop a BAL module comprised of iPSC-derived hepatocytes (iHeps) arrayed on the extracapillary space (ECS) of hollow fiber membranous capillaries that allow the flow of blood through the intracapillary space (ICS), thus mimicking the tissue microarchitecture. For the proof-of-concept in vitro study, a cartridge having semipermeable polysulfone membrane fibers was used as an artificial liver device. As a source for human liver cells, we derived metabolically active hepatocytes from iPSCs. The iHeps on microcarrier beads were loaded into the ECS of a hollow fiber bioreactor cartridge and cultured using a closed-circuit continuous flow system. The iHeps secreted human albumin, prothrombin, and apolipoprotein B into the hollow fiber ICS media, and the continuous flow system also improved maturation of iHeps. In conclusion, the iPSC-hepatocytes in the bioartificial liver device maintained the secretory function and exhibited cell maturation. The iPSC-hepatocyte BAL has the potential to be further developed as a liver support device for the treatment of decompensated liver diseases.

Artificial liver support systems: a patient‐device model

ABSTRACTMany efforts have been carried out for over 40 years in the attempt to design liver support devices suitable for a temporary clinical use, either to bridge the patients to liver transplantation or to help to keep them alive until the recovery of native liver function. Really, a deeper knowledge of the physicochemical basis of their functioning is essential to ‘engineer’ these devices, that is, to design new artificial liver devices, to optimize the existing ones and to taylor the patient treatment on his clinical state. In this framework, this work has been finalized to obtain a mathematical model of the whole patient‐artificial device system as useful tool for a chemical engineering point of view analysis. © 2014 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Micropatterned co-culture of hepatocyte spheroids layered on non-parenchymal cells to understand heterotypic cellular interactions

Microfabrication and micropatterning techniques in tissue engineering offer great potential for creating and controlling cellular microenvironments including cell–matrix interactions, soluble stimuli and cell–cell interactions. Here, we present a novel approach to generate layered patterning of hepatocyte spheroids on micropatterned non-parenchymal feeder cells using microfabricated poly(ethylene glycol) (PEG) hydrogels. Micropatterned PEG-hydrogel-treated substrates with two-dimensional arrays of gelatin circular domains (φ = 100 μm) were prepared by photolithographic method. Only on the critical structure of PEG hydrogel with perfect protein rejection, hepatocytes were co-cultured with non-parenchymal cells to be led to enhanced hepatocyte functions. Then, we investigated the mechanism of the functional enhancement in co-culture with respect to the contributions of soluble factors and direct cell–cell interactions. In particular, to elucidate the influence of soluble factors on hepatocyte function, hepatocyte spheroids underlaid with fibroblasts (NIH/3T3 mouse fibroblasts) or endothelial cells (BAECs: bovine aortic endothelial cells) were compared with physically separated co-culture of hepatocyte monospheroids with NIH3T3 or BAEC using trans-well culture systems. Our results suggested that direct heterotypic cell-to-cell contact and soluble factors, both of these between hepatocytes and fibroblasts, significantly enhanced hepatocyte functions. In contrast, direct heterotypic cell-to-cell contact between hepatocytes and endothelial cells only contributed to enhance hepatocyte functions. This patterning technique can be a useful experimental tool for applications in basic science, drug screening and tissue engineering, as well as in the design of artificial liver devices.

A feeder-cell independent subpopulation of the PICM-19 pig liver stem cell line capable of long-term growth and extensive expansion

A method for the feeder-independent culture of PICM-19 pig liver stem cell line was recently devised, but the cell line's growth was finite and the cells essentially ceased dividing after approximately 20 passages over a 1year culture period. Here we report the isolation, continuous culture, and initial characterization of a spontaneously arising feeder-independent PICM-19 subpopulation, PICM-19FF, that maintained replication rate and hepatocyte functions over an extended culture period. PICM-19FF cells grew to 90-98% confluency after each passage at 2week intervals, and the cells maintained a high cell density after 2years and 48 passages in culture (average of 2.6×10(6) cells/T25 flask or 1×10(5) cells/cm(2)). Morphologically, the PICM-FF cells closely resembled the finite feeder-independent PICM-19 cultures previously reported, and, as before, no spontaneous formation of 3D multicellular ductules occurred in the cells' monolayer. Their bipotent stem cell nature was therefore not evident. Over extensive passage, cytochrome P450 (EROD) activity was maintained, although urea production was reduced on a per mg protein basis at later passages. Two other attributes of fetal hepatocytes, γ-glutamyl transpeptidase activity and serum-protein secretion, were also shown to be maintained by the PICM-19FF cells. The PICM-19FF cells therefore appear to have indefinite growth potential as a feeder-independent cell line and this should enhance the experimental usefulness of the cell line, in general, and may also improve its application to toxicological/pharmacological assays and artificial liver devices.

Artificial liver devices: A chemical engineering analysis

AbstractAll the most widely used liver support devices implement the same elementary unit operations, mainly membrane separation and adsorption, to remove albumin‐bound toxins. Mathematical modeling of these operations is a well‐consolidated knowledge of chemical engineering, and the evaluation of the performance of these apparatus can be confidently carried out once equilibrium conditions and transport phenomena kinetics are known. In this work, a device‐focused analysis of liver support devices is presented, with the aim of providing a framework for the quantitative and semiquantitative assessment of their performance. The analysis is based on simple mathematical models of the single unit operations implemented in the detoxification processes. A preliminary validation of the models against data obtained during a clinical molecular adsorbent recirculating system (MARS) session, and referring to bilirubin detoxification was performed; the results showed that the models used are consistent and possess a very good order‐of‐magnitude prediction capability. Copyright © 2010 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

An evaluation of the utility of the hepatic differentiation method using hollow fiber/organoid culture for the development of a hybrid artificial liver device

To put the hybrid artificial liver (HAL) using cultured hepatocytes into practical use, it is necessary to develop a high-performance artificial liver device. We developed a novel hollow fiber (HF)/organoid culture method to induce the differentiation of pluripotent stem cells into hepatocytes. In this study, we compared the results of the hepatic differentiation using the HF/organoid culture with those using monolayer culture to evaluate its utility as a hepatic differentiation method. In both cell cultures, ES cells showed high proliferative activity immediately after cell seeding. The up-regulation of hepatocyte-specific markers such as albumin (ALB), carbamoyl phosphate synthetase 1 ( CPS-1) and tryptophan 2, 3-dioxygenase ( TDO) were observed as the culture progressed, and the expression of liver-specific functions such as the removal of ammonia and albumin secretion were detected after about 2 weeks of the hepatic differentiation induction in the HF/organoid culture. However, the results were not observed in the monolayer culture. In conclusion, the HF/organoid culture method has promise as an effective tool for the differentiation of ES cells into hepatocytes.

Artificial Liver Devices and Bioartificial Liver Systems: Current Status

Acute liver failure is a rapidly progressive disease of the liver associated with high morbidity and mortality without liver transplantation. Although good survival after transplantation can be achieved, due to the disparity between patients awaiting transplantation and available organs, many patients die due to progression of the disease while waiting for a liver graft. To reduce the high morbidity and mortality associated with acute liver failure, attempts have been made during the last several decades to develop a temporary liver support system, such as artificial and bioartificial livers. The artificial liver is a non-biological device mainly aimed at the removal of accumulated toxins during liver failure, and the bioartificial liver is a biological device that has bioreactors containing living hepatocytes which provide both biotransformation and synthetic liver functions. There are currently 3 artificial livers available in the market that have been actively used in the clinical field, and 11 bioartificial livers that have been developed and have undergone clinical trials. In this article, we will discuss about the 3 artificial liver devices and 5 bioartificial liver systems that are the most advanced and have been widely evaluated clinically. Also, the characteristics and the preclinical data of the first bioartificial liver system developed in Korea that is currently under clinical investigation, will be discussed.

Feeder-independent continuous culture of the PICM-19 pig liver stem cell line

The PICM-19 pig liver stem cell line is a bipotent cell line, i.e., capable of forming either bile ductules or hepatocyte monolayers in vitro, that was derived from the primary culture of pig embryonic stem cells. The cell line has been strictly feeder-dependent in that cell replication, morphology, and function were lost if the cells were cultured without STO feeder cells. A method for the feeder-independent continuous culture of PICM-19 cells (FI-PICM-19) is presented. PICM-19 cells were maintained and grown without feeder cells on collagen I-coated tissue culture plastic for 26 passages (P26) with initial split ratios of 1:3 that diminished to split ratios of less than 1:2 after passage 16. Once plated, the FI-PICM-19 cells were overlaid with a 1:12 to 1:50 dilution of Matrigel or related extracellular matrix product. Growth of the cells was stimulated by daily refeedings with STO feeder-cell conditioned medium. The FI-PICM-19 cells grew to an approximate confluence of 50% prior to each passage at 2-wk intervals. Growth curve analysis showed their average cell number doubling time to be ~96 h. Morphologically, the feeder-independent cells closely resembled PICM-19 cells grown on feeder cells, and biliary canalicui were present at cell-to-cell junctions. However, no spontaneous multicellular ductules formed in the monolayers of FI-PICM-19 cells. Ultrastructural subcellular features of the FI-PICM-19 cells were similar to those of PICM-19 cells cultured on feeder cells. The FI-PICM-19 cells produced a spectrum of serum proteins and expressed many liver/hepatocyte-specific genes. Importantly, cytochrome P450 (EROD) activity, ammonia clearance, and urea production were maintained by the feeder-independent cells. This simple method for the propagation of the PICM-19 cell line without feeder cells should simplify the generation and selection of functional mutants within the population and enhances the cell line's potential for use in toxicological/pharmacological screening assays and for use in an artificial liver device.

Characterization of Two Subpopulations of the PICM-19 Porcine Liver Stem Cell Line for use in Cell-Based Extracorporeal Liver Assistance Devices

Two cell lines, PICM-19H and PICM-19B, were derived from the bipotent PICM-19 pig liver stem cell line and assessed for their potential application in artificial liver devices (ALD). The study included assessments of growth rate and cell density in culture, morphological features, serum protein production, gamma-glutamyltranspeptidase (GGT) activity and hepatocyte detoxification functions, i.e., inducible P450 activity, ammonia clearance, and urea production. The PICM-19H cell line was derived by temperature selection at 33-34 degrees C. After each passage, PICM-19H cells grew to a nearly confluent monolayer of cells of hepatocyte morphology, i.e., cuboidal cells with centrally located nuclei joined by biliary canaliculi. No differentiation and self-organization into multi-cellular bile ductules, as observed in the parental PICM-19 cell line, occurred within the PICM-19H cell monolayers. The PICM-19H cells contained numerous mitochondria, Golgi apparatus, smooth and rough endoplasmic reticulum, vesicular bodies and occasional lipid vacuoles. The cells had a doubling time of 48-72 h and reached a final density of 1.5 x 10(5) cells/cm(2) at approximately10 d post-passage from a 1:6 split ratio. PICM-19H cells displayed inducible P450 activity, cleared ammonia, and produced urea in a glutamine-free medium. The PICM-19B cells were colony-cloned after spontaneous generation from the PICM-19 parental cell line. PICM-19B cells grew as a tightly knit dome-forming monolayer with no visible biliary canaliculi. Their doubling time was 48-72 h with a final cell density of 2.6 x 10(5) cells/cm(2). Ultrastructural analysis of the PICM-19B monolayers showed the roughly cuboidal cells displayed basal-apical polarization and were joined by tight junction-like complexes. Other ultrastructure features were similar to those of PICM-19H cells except that they possessed numerous cell bodies resembling mucus vacuoles. The PICM-19B cells had relatively high levels of GGT activity, but did retain some inducible P450 activity, and some ammonia clearance and urea synthesis ability. PICM-19B cells produced markedly less serum proteins than PICM-19H cells. These data indicated that both cell lines, either together or alone, may be useful as the cellular substrate for an ALD.