Isolation and co-culture of rat parenchymal and non-parenchymal liver cells to evaluate cellular interactions and response

Liver sinusoidal endothelial cell: An important yet often overlooked player in the liver fibrosis

Liver sinusoidal endothelial cells (LSECs) are liver-specific endothelial cells with the highest permeability than other mammalian endothelial cells, characterized by the presence of fenestrae on their surface, the absence of diaphragms and the lack of basement membrane. Located at the interface between blood and other liver cell types, LSECs mediate the exchange of substances between the blood and the Disse space, playing a crucial role in maintaining substance circulation and homeostasis of multicellular communication. As the initial responders to chronic liver injury, the abnormal LSEC activation not only changes their own physicochemical properties but also interrupts their communication with hepatic stellate cells and hepatocytes, which collectively aggravates the process of liver fibrosis. In this review, we have comprehensively updated the various pathways by which LSECs were involved in the initiation and aggravation of liver fibrosis, including but not limited to cellular phenotypic change, the induction of capillarization, decreased permeability and regulation of intercellular communications. Additionally, the intervention effects and latest regulatory mechanisms of anti-fibrotic drugs involved in each aspect have been summarized and discussed systematically. As we studied deeper into unraveling the intricate role of LSECs in the pathophysiology of liver fibrosis, we unveil a promising horizon that pave the way for enhanced patient outcomes.

Anti-apoptotic treatment of warm ischemic male rat livers in machine perfusion improves symptoms of ischemia-reperfusion injury

Background

Liver donation after cardiac death (DCD) makes up a small percentage of the organs used in transplantation and poses a higher risk of graft loss compared to donation after brain death (DBD); this is a result of ischemia reperfusion for which the exact injury mechanisms are currently not fully understood. However, reperfusion injury has been shown to lead to necrosis as well as apoptosis through oxidative stress and mitochondrial dysfunction. In this work, we propose that use of the pro-survival, anti-apoptotic CEPT cocktail in post-ischemia normothermic machine perfusion (NMP) may improve recovery in rat livers subjected to extended durations of warm ischemia.

Materials and Methods

Livers procured from male Lewis rats were subjected to 90 min of warm ischemia, followed by 6 h of NMP where they were treated either with the survival-enhancing anti-apoptotic cocktail (CEPT), the vehicle (DMSO) or the base media with no additives.

Results

The CEPT-treated group exhibited lower expression of hepatic injury biomarkers, and improvement in a range of hepatocellular symptoms associated with the hepatic parenchyma, biliary epithelium and the sinusoidal endothelium, including recovery of bile secretion and lowered vascular resistance.

Conclusions

This study's findings suggest apoptosis plays a more significant role in ischemia-reperfusion injury than previously understood, and provide useful insight for further investigation of the specific underlying mechanisms and development of novel treatment methods.

Coculture model of a liver sinusoidal endothelial cell barrier and HepG2/C3a spheroids-on-chip in an advanced fluidic platform

The liver is one of the main organs involved in the metabolism of xenobiotics and a key organ in toxicity studies. Prior to accessing the hepatocytes, xenobiotics pass through the hepatic sinusoid formed by liver sinusoidal endothelial cells (LSECs). The LSECs barrier regulates the kinetics and concentrations of the xenobiotics before their metabolic processing by the hepatocytes. To mimic this physiological situation, we developed an in vitro model reproducing an LSECs barrier in coculture with a hepatocyte biochip, using a fluidic platform. This technology made dynamic coculture and tissue crosstalk possible. SK-HEP-1 and HepG2/C3a cells were used as LSECs and as hepatocyte models, respectively. We confirmed the LSECs phenotype by measuring PECAM-1 and stabilin-2 expression levels and the barrier's permeability/transport properties with various molecules. The tightness of the SK-HEP-1 barrier was enhanced in the dynamic coculture. The morphology, albumin secretion, and gene expression levels of markers of HepG2/C3a were not modified by coculture with the LSECs barrier. Using acetaminophen, a well-known hepatotoxic drug, to study tissue crosstalk, there was a reduction in the expression levels of the LSECs markers stabilin-2 and PECAM-1, and a modification of those of CLEC4M and KDR. No HepG2/C3a toxicity was observed. The metabolisation of acetaminophen by HepG2/C3a monocultures and cocultures was confirmed. Although primary cells are required to propose a fully relevant model, the present approach highlights the potential of our system for investigating xenobiotic metabolism and toxicity.

Exploring the impact of severity in hepatic fibrosis disease on the intrahepatic distribution of novel biodegradable nanoparticles targeted towards different disease biomarkers

Nanoparticle-based drug delivery systems (DDS) have shown promising results in reversing hepatic fibrosis, a common pathological basis of chronic liver diseases (CLDs), in preclinical animal models. However, none of these nanoparticle formulations has transitioned to clinical usage and there are currently no FDA-approved drugs available for liver fibrosis. This highlights the need for a better understanding of the challenges faced by nanoparticles in this complex disease setting. Here, we have systematically studied the impact of targeting strategy, the degree of macrophage infiltration during fibrosis, and the severity of fibrosis, on the liver uptake and intrahepatic distribution of nanocarriers. When tested in mice with advanced liver fibrosis, we demonstrated that the targeting ligand density plays a significant role in determining the uptake and retention of the nanoparticles in the fibrotic liver whilst the type of targeting ligand modulates the trafficking of these nanoparticles into the cell population of interest - activated hepatic stellate cells (aHSCs). Engineering the targeting strategy indeed reduced the uptake of nanoparticles in typical mononuclear phagocyte (MPS) cell populations, but not the infiltrated macrophages. Meanwhile, additional functionalization may be required to enhance the efficacy of DDS in end-stage fibrosis/cirrhosis compared to early stages.

Metformin pretreatment ameliorates busulfan-induced liver endothelial toxicity during haematopoietic stem cell transplantation

The success of Haematopoietic cell transplantation (HCT) is often limited by regimen-related toxicity (RRT) caused by conditioning regimen drugs. Among different conditioning drugs, busulfan (Bu) and treosulfan (Treo), although widely used in HCT, exhibit different toxicity profiles, the mechanism of which is still unclear. Here we investigated the effects of Bu and Treo in endothelial cells. While both Bu and Treo induced DNA damage in endothelial cells, we observed Bu alone to induce oxidative stress and sustained activation of phospho-ERK1/2, leading to apoptosis. However, Treo-treated cells exhibited no oxidative stress/apoptosis of endothelial cells. Screening of pharmacological inhibitors of both ROS and p-ERK revealed that metformin effectively ameliorates Bu-mediated toxicity in endothelial cells. In Balb/c mice, we observed a significant reduction in bone marrow endothelial cells in Bu-treated mice compared to Treo-treated mice. Further, liver sinusoidal endothelial cells (LSEC) was damaged by Bu, which is implicated in liver vasculature and their functional capacity to uptake FITC-albumin. However, Treo-treated mice liver vasculature was morphologically and functionally normal. When mice were pretreated with metformin followed by Bu, LSECs damage was ameliorated morphologically and functionally. Bone marrow transplants done on these mice did not affect the engraftment of donor cells.

Anti-apoptotic treatment of warm ischemic male rat livers in machine perfusion improves symptoms of ischemia-reperfusion injury

Liver donation after cardiac death (DCD) makes up a small percentage of the donor pool and poses a higher risk of graft loss compared to donation after brain death (DBD); this is a result of ischemia reperfusion for which the exact injury mechanisms are currently not fully understood. However, reperfusion injury has been shown to lead to necrosis as well as apoptosis at the cellular level. In this work, we propose that use of the pro-survival, anti-apoptotic CEPT cocktail in post-ischemia normothermic machine perfusion (NMP) may improve recovery in rat livers subjected to extended durations of warm ischemia. Livers procured from male lewis rats were subjected to 90 minutes of warm ischemia, followed by 6 hours of NMP where they were treated with the survival-enhancing anti-apoptotic cocktail (CEPT), the vehicle (DMSO) or the base media with no additives. The CEPT-treated group exhibited lower expression of hepatic injury biomarkers, and improvement in a range of hepatocellular functions associated with the hepatic parenchyma, biliary epithelium and especially the sinusoidal endothelium. This study's findings provide useful insight for further investigation of the extent of apoptotic contribution to ischemia reperfusion injury (IRI).

Liver dECM-Gelatin Composite Bioink for Precise 3D Printing of Highly Functional Liver Tissues

In recent studies, liver decellularized extracellular matrix (dECM)-based bioinks have gained significant attention for their excellent compatibility with hepatocytes. However, their low printability limits the fabrication of highly functional liver tissue. In this study, a new liver dECM-gelatin composite bioink (dECM gBioink) was developed to overcome this limitation. The dECM gBioink was prepared by incorporating a viscous gelatin mixture into the liver dECM material. The novel dECM gBioink showed 2.44 and 10.71 times higher bioprinting resolution and compressive modulus, respectively, than a traditional dECM bioink. In addition, the new bioink enabled stable stacking with 20 or more layers, whereas a structure printed with the traditional dECM bioink collapsed. Moreover, the proposed dECM gBioink exhibited excellent hepatocyte and endothelial cell compatibility. At last, the liver lobule mimetic structure was successfully fabricated with a precisely patterned endothelial cell cord-like pattern and primary hepatocytes using the dECM gBioink. The fabricated lobule structure exhibited excellent hepatic functionalities and dose-dependent responses to hepatotoxic drugs. These results demonstrated that the gelatin mixture can significantly improve the printability and mechanical properties of the liver dECM materials while maintaining good cytocompatibility. This novel liver dECM gBioink with enhanced 3D printability and resolution can be used as an advanced tool for engineering highly functional liver tissues.

Microphysiological Models for Mechanistic-Based Prediction of Idiosyncratic DILI

Drug-induced liver injury (DILI) is a major contributor to high attrition rates among candidate and market drugs and a key regulatory, industry, and global health concern. While acute and dose-dependent DILI, namely, intrinsic DILI, is predictable and often reproducible in preclinical models, the nature of idiosyncratic DILI (iDILI) limits its mechanistic understanding due to the complex disease pathogenesis, and recapitulation using in vitro and in vivo models is extremely challenging. However, hepatic inflammation is a key feature of iDILI primarily orchestrated by the innate and adaptive immune system. This review summarizes the in vitro co-culture models that exploit the role of the immune system to investigate iDILI. Particularly, this review focuses on advancements in human-based 3D multicellular models attempting to supplement in vivo models that often lack predictability and display interspecies variations. Exploiting the immune-mediated mechanisms of iDILI, the inclusion of non-parenchymal cells in these hepatoxicity models, namely, Kupffer cells, stellate cells, dendritic cells, and liver sinusoidal endothelial cells, introduces heterotypic cell-cell interactions and mimics the hepatic microenvironment. Additionally, drugs recalled from the market in the US between 1996-2010 that were studies in these various models highlight the necessity for further harmonization and comparison of model characteristics. Challenges regarding disease-related endpoints, mimicking 3D architecture with different cell-cell contact, cell source, and the underlying multi-cellular and multi-stage mechanisms are described. It is our belief that progressing our understanding of the underlying pathogenesis of iDILI will provide mechanistic clues and a method for drug safety screening to better predict liver injury in clinical trials and post-marketing.

Investigation of the metabolomic crosstalk between liver sinusoidal endothelial cells and hepatocytes exposed to paracetamol using organ-on-chip technology

Organ-on-chip technology is a promising in vitro approach recapitulating human physiology for the study of responses to drug exposure. Organ-on-chip cell cultures have paved new grounds for testing and understanding metabolic dose-responses when evaluating pharmaceutical and environmental toxicity. Here, we present a metabolomic investigation of a coculture of liver sinusoidal endothelial cells (LSECs, SK-HEP-1) with hepatocytes (HepG2/C3a) using advanced organ-on-chip technology. To reproduce the physiology of the sinusoidal barrier, LSECs were separated from hepatocytes by a membrane (culture insert integrated organ-on-chip platform). The tissues were exposed to acetaminophen (APAP), an analgesic drug widely used as a xenobiotic model in liver and HepG2/C3a studies. The differences between the SK-HEP-1, HepG2/C3a monocultures and SK-HEP-1/HepG2/C3a cocultures, treated or not with APAP, were identified from metabolomic profiles using supervised multivariate analysis. The pathway enrichment coupled with metabolite analysis of the corresponding metabolic fingerprints contributed to extracting the specificity of each type of culture and condition. In addition, we analysed the responses to APAP treatment by mapping the signatures with significant modulation of the biological processes of the SK-HEP-1 APAP, HepG2/C3a APAP and SK-HEP-1/HepG2/C3a APAP conditions. Furthermore, our model shows how the presence of the LSECs barrier and APAP first pass can modify the metabolism of HepG2/C3a. Altogether, this study demonstrates the potential of a "metabolomic-on-chip" strategy for pharmaco-metabolomic applications predicting individual response to drugs.

Modeling drug-induced liver injury and screening for anti-hepatofibrotic compounds using human PSC-derived organoids

Preclinical models that can accurately predict the toxicity and efficacy of candidate drugs to human liver tissue are in urgent need. Human liver organoid (HLO) derived from human pluripotent stem cells offers a possible solution. Herein, we generated HLOs, and demonstrated the utility of these HLOs in modeling a diversity of phenotypes associated with drug-induced liver injury (DILI), including steatosis, fibrosis, and immune responses. Phenotypic changes in HLOs after treatment with tool compounds such as acetaminophen, fialuridine, methotrexate, or TAK-875 showed high concordance with human clinical data in drug safety testings. Moreover, HLOs were able to model liver fibrogenesis induced by TGFβ or LPS treatment. We further devised a high-content analysis system, and established a high-throughput anti-fibrosis drug screening system using HLOs. SD208 and Imatinib were identified that can significantly suppress fibrogenesis induced by TGFβ, LPS, or methotrexate. Taken together, our studies demonstrated the potential applications of HLOs in drug safety testing and anti-fibrotic drug screening.

The native liver as inspiration to create superior in vitro hepatic models

Drug induced liver injury (DILI) is one of the major reasons of drug withdrawal during the different phases of drug development. The later in the drug development a drug is discovered to be toxic, the higher the economical as well as the ethical impact will be. In vitro models for early detection of drug liver toxicity are under constant development, however to date a superior model of the liver is still lacking. Ideally, a highly reliable model should be established to maintain the different hepatic cell functionalities to the greatest extent possible, during a period of time long enough to allow for tracking of the toxicity of compounds. In the case of DILI, toxicity can appear even after months of exposure. To reach this goal, an in vitro model should be developed that mimics the in vivo liver environment, function and response to external stimuli. The different approaches for the development of liver models currently used in the field of tissue engineering will be described in this review. Combining different technologies, leading to optimal materials, cells and 3D-constructs will ultimately lead to an ideal superior model that fully recapitulates the liver.

PROM1-mediated cell signal transduction in cancer stem cells and hepatocytes

Prominin-1 (PROM1), also called CD133, is a penta-span transmembrane protein that is localized in membrane protrusions, such as microvilli and filopodia. It is known to be expressed in cancer stem cells and various progenitor cells of bone marrow, liver, kidney, and intestine. Accumulating evidence has revealed that PROM1 has multiple functions in various organs, such as eye, tooth, peripheral nerve, and liver, associating with various molecular protein partners. PROM1 regulates PKA-induced gluconeogenesis, TGFβ-induced fibrosis, and IL-6-induced regeneration in the liver, associating with Radixin, SMAD7, and GP130, respectively. In addition, PROM1 is necessary to maintain cancer stem cell properties by activating PI3K and β-Catenin. PROM1-deficienct mice also show distinct phenotypes in eyes, brain, peripheral nerves, and tooth. Here, we discuss recent findings of PROM1-mediated signal transduction. [BMB Reports 2023; 56(2): 65-70].

Primary Hepatocyte Isolation and Cultures: Technical Aspects, Challenges and Advancements

Hepatocytes are differentiated cells that account for 80% of the hepatic volume and perform all major functions of the liver. In vivo, after an acute insult, adult hepatocytes retain their ability to proliferate and participate in liver regeneration. However, in vitro, prolonged culture and proliferation of viable and functional primary hepatocytes have remained the major and the most challenging goal of hepatocyte-based cell therapies and liver tissue engineering. The first functional cultures of rat primary hepatocytes between two layers of collagen gel, also termed as the "sandwich cultures", were reported in 1989. Since this study, several technical developments including choice of hydrogels, type of microenvironment, growth factors and culture conditions, mono or co-cultures of hepatocytes along with other supporting cell types have evolved for both rat and human primary hepatocytes in recent years. All these improvements have led to a substantial improvement in the number, life-span and hepatic functions of these cells in vitro for several downstream applications. In the current review, we highlight the details, limitations and prospects of different technical strategies being used in primary hepatocyte cultures. We discuss the use of newer biomaterials as scaffolds for efficient culture of primary hepatocytes. We also describe the derivation of mature hepatocytes from other cellular sources such as induced pluripotent stem cells, bone marrow stem cells and 3D liver organoids. Finally, we also explain the use of perfusion-based bioreactor systems and bioengineering strategies to support the long-term function of hepatocytes in 3D conditions.

Immune microenvironment and therapeutic progress of recurrent hepatocellular carcinoma after liver transplantation

HCC is a highly lethal tumor, and orthotopic liver transplantation, as one of the radical treatment methods for HCC, has opened-up a new therapeutic approach for the treatment of primary liver cancer. However, tumor recurrence after liver transplantation is the main reason that affects the long-term survival of recipients. At present, the application of ICIs has brought dawn to patients with refractory HCC. However, because of the special immune tolerance state created by long-term oral immunosuppressants in patients with HCC after liver transplantation, the current focus is how to regulate the immune balance of such patients and simultaneously maximize the anti-tumor effect. This article reviews the relationship between liver cancer and immunity, immune tolerance of liver transplantation, immune microenvironment after liver transplantation for HCC, and the application of immunotherapy in the recurrence of liver transplantation for HCC.

Liver-on-a-chip: Considerations, advances, and beyond

The liver is the largest internal organ in the human body with largest mass of glandular tissue. Modeling the liver has been challenging due to its variety of major functions, including processing nutrients and vitamins, detoxification, and regulating body metabolism. The intrinsic shortfalls of conventional two-dimensional (2D) cell culture methods for studying pharmacokinetics in parenchymal cells (hepatocytes) have contributed to suboptimal outcomes in clinical trials and drug development. This prompts the development of highly automated, biomimetic liver-on-a-chip (LOC) devices to simulate native liver structure and function, with the aid of recent progress in microfluidics. LOC offers a cost-effective and accurate model for pharmacokinetics, pharmacodynamics, and toxicity studies. This review provides a critical update on recent developments in designing LOCs and fabrication strategies. We highlight biomimetic design approaches for LOCs, including mimicking liver structure and function, and their diverse applications in areas such as drug screening, toxicity assessment, and real-time biosensing. We capture the newest ideas in the field to advance the field of LOCs and address current challenges.

Construction of polysaccharide scaffold-based perfusion bioreactor supporting liver cell aggregates for drug screening

Rebuilding a suitable microenvironment of liver cells is the key challenge to enhancing the expression of hepatic functions for drug screening in vitro. To improve the microenvironment by providing the specific adhesive ligands for hepatocytes in the three-dimensional dynamic culture, a perfusion bioreactor with a pectin/alginate blend porous scaffold was constructed in this study. The galactosyl component in the main chain of pectin was able to be specifically recognized by the asialoglycoprotein receptor on the surface of hepatocytes, and subsequently promoted the adhesion and aggregation of hepatocytes co-cultured with hepatic non-parenchymal cells. The bioreactor was optimized for 4 h of dynamic inoculation followed by perfusion at a flow rate of 2 mL/min, which provided adequate oxygen supply and good mass transfer to the liver cells. During dynamic cultured in the bioreactor for 14 days, more multicellular aggregates were formed and were evenly distributed in the pectin/alginate blend scaffolds. The expressions of intercellular interaction and hepatic functions of the hepatocytes in aggregates were significantly enhanced in the three-dimensional dynamic group. Furthermore, the bioreactor not only markedly upregulated the cell polarity markers expression of hepatocytes but also enhanced their metabolic capacity to acetaminophen, isoniazid, and tolbutamide, which exhibited a significant concentration-dependent manner. Therefore, the pectin/alginate blend scaffold-based perfusion bioreactor appeared to be a promising candidate in the field of drug development and liver regeneration research.

Pentoxifylline attenuates nonalcoholic fatty liver by inhibiting hepatic macrophage polarization to the M1 phenotype

BACKGROUND

Nonalcoholic fatty liver (NAFL), recognized as one of the most common causes of chronic liver diseases, is increasingly prevalent worldwide. Pentoxifylline, a derivative of theobromine extracted from Theobroma cacao and tea, has been studied for effects on blood viscosity, tissue oxygenation and inflammation. However, its effects on hepatic lipid accumulation and the potential mechanisms remain unclear.

PURPOSE

This study aimed to investigate the therapeutic effects of pentoxifylline on high-fat diet-induced NAFL and to explore the corresponding molecular mechanisms.

METHODS

NAFL mice were injected with or without 25, 50 or 100 mg/kg pentoxifylline for 2 weeks. Hepatic steatosis was observed by haematoxylin-eosin staining and Oil Red O staining, the levels of serum total cholesterol, triglyceride were detected by biochemical kits, and insulin resistance was evaluated by glucose and insulin tolerance tests. In addition, we measured the frequencies of macrophage and its polarization subsets in the liver using flow cytometry and immunofluorescence. The expressions of proteins associated with macrophage polarization signaling pathways were assessed by Western blotting and flow cytometry histograms. Molecular docking and cellular thermal shift assay were conducted to identify and verify the target protein of pentoxifylline in macrophage.

RESULTS

Pentoxifylline significantly alleviated hepatic lipid accumulation, reduced blood lipid levels and improved insulin resistance. Strikingly, the excessive M1 macrophages in NAFL development was abolished by pentoxifylline. And pentoxifylline was further evidenced it failed to reduce hepatocyte lipid accumulation in the absence of macrophages in vitro. Mechanistically, pentoxifylline competed with LPS for binding to toll-like receptor 4, dramatically inhibiting the TLR4/MyD88/NF-κB signaling pathway.

CONCLUSION

Pentoxifylline attenuated NAFL by inhibiting hepatic macrophage M1 polarization, indicating that pentoxifylline could be a therapeutic candidate for NAFL. This study first observed that M1 macrophages were increased in NAFL mice and then revealed the molecule targeted by pentoxifylline. In addition, we provided evidence that macrophage targeting may be an emerging strategy for NAFL treatment.

Point-of-use, automated fabrication of a 3D human liver model supplemented with human adipose microvessels

Advanced in vitro tissue models better reflect healthy and disease tissue conditions in the body. However, complex tissue models are often manufactured using custom solutions and can be challenging to manufacture to scale. Here, we describe the automated fabrication of a cell-dense, thick (≤ 1 cm), human vascularized liver tissue model using a robotic biomanufacturing platform and off-the-shelf components to build, culture, and sample liver tissues hands-free without compromising tissue health or function. Fabrication of the tissue involved 3D bioprinting and incorporation of primary human hepatocytes, primary human non-parenchymal cells, and isolated fragments of intact human microvessels as vascular precursors. No differences were observed in select assessments of the liver tissues fabricated by hand or via automation. Furthermore, constant media exchange, via perfusion, improved urea output and elevated tissue metabolism. Interestingly, inclusion of adipose-derived human microvessels enhanced functional gene expression, including an enhanced response to a drug challenge. Our results describe the fabrication of a thick liver tissue environment useful for a variety of applications including liver disease modeling, infectious agent studies, and cancer investigations. We expect the automated fabrication of the vascularized liver tissue, at the point of use and using off-the-shelf platforms, eases fabrication of the complex model and increases its utility.

Nanostructured Lipid Carriers Loaded with Dexamethasone Prevent Inflammatory Responses in Primary Non-Parenchymal Liver Cells

Liver inflammation represents a major clinical problem in a wide range of pathologies. Among the strategies to prevent liver failure, dexamethasone (DXM) has been widely used to suppress inflammatory responses. The use of nanocarriers for encapsulation and sustained release of glucocorticoids to liver cells could provide a solution to prevent severe side effects associated with systemic delivery as the conventional treatment regime. Here we describe a nanostructured lipid carrier developed to efficiently encapsulate and release DXM. This nano-formulation proved to be stable over time, did not interact in vitro with plasma opsonins, and was well tolerated by primary non-parenchymal liver cells (NPCs). Released DXM preserved its pharmacological activity, as evidenced by inducing robust anti-inflammatory responses in NPCs. Taken together, nanostructured lipid carriers may constitute a reliable platform for the delivery of DXM to treat pathologies associated with chronic liver inflammation.

Enrichment Methods for Murine Liver Non-Parenchymal Cells Differentially Affect Their Immunophenotype and Responsiveness towards Stimulation

Hepatocytes comprise the majority of the liver and largely exert metabolic functions, whereas non-parenchymal cells (NPCs)—comprising Kupffer cells, dendritic cells and liver sinusoidal endothelial cells—control the immunological state within this organ. Here, we compared the suitability of two isolation methods for murine liver NPCs. Liver perfusion (LP) with collagenase/DNase I applied via the portal vein leads to efficient liver digestion, whereas the modified liver dissociation (LD) method combines mechanical dissociation of the retrieved organ with enzymatic degradation of the extracellular matrix. In cases of both LP and LD, NPCs were enriched by subsequent gradient density centrifugation. Our results indicate that LP and LD are largely comparable with regards to the yield, purity, and composition of liver NPCs. However, LD-enriched liver NPCs displayed a higher degree of activation after overnight cultivation, and accordingly were less responsive towards stimulation with toll-like receptor ligands that are frequently used as adjuvants, e.g., in nano-vaccines. We conclude that LP is more suitable for obtaining liver NPCs for subsequent in vitro studies, whereas LD as the less laborious method, is more convenient for parallel isolation of larger numbers of samples for ex vivo analysis.

Three-dimensional (3D) liver cell models - a tool for bridging the gap between animal studies and clinical trials when screening liver accumulation and toxicity of nanobiomaterials

Despite the exciting properties and wide-reaching applications of nanobiomaterials (NBMs) in human health and medicine, their translation from bench to bedside is slow, with a predominant issue being liver accumulation and toxicity following systemic administration. In vitro 2D cell-based assays and in vivo testing are the most popular and widely used methods for assessing liver toxicity at pre-clinical stages; however, these fall short in predicting toxicity for NBMs. Focusing on in vitro and in vivo assessment, the accurate prediction of human-specific hepatotoxicity is still a significant challenge to researchers. This review describes the relationship between NBMs and the liver, and the methods for assessing toxicity, focusing on the limitations they bring in the assessment of NBM hepatotoxicity as one of the reasons defining the poor translation for NBMs. We will then present some of the most recent advances towards the development of more biologically relevant in vitro liver methods based on tissue-mimetic 3D cell models and how these could facilitate the translation of NBMs going forward. Finally, we also discuss the low public acceptance and limited uptake of tissue-mimetic 3D models in pre-clinical assessment, despite the demonstrated technical and ethical advantages associated with them.

Generation of Oxygenating Fluorinated Methacrylamide Chitosan Microparticles to Increase Cell Survival and Function in Large Liver Spheroids

Despite advances in the development of complex culture technologies, the utility, survival, and function of large 3D cell aggregates, or spheroids, are impeded by mass transport limitations. The incorporation of engineered microparticles into these cell aggregates offers a promising approach to increase spheroid integrity through the creation of extracellular spaces to improve mass transport. In this study, we describe the formation of uniform oxygenating fluorinated methacrylamide chitosan (MACF) microparticles via a T-shaped microfluidic device, which when incorporated into spheroids increased extracellular spacing and enhanced oxygen transport via perfluorocarbon substitutions. The addition of MACF microparticles into large liver cell spheroids supported the formation of stable and large spheroids (>500 μm in diameter) made of a heterogeneous population of immortalized human hepatoma (HepG2) and hepatic stellate cells (HSCs) (4 HepG2/1 HSC), especially at a 150:1 ratio of cells to microparticles. Further, as confirmed by the albumin, urea, and CYP3A4 secretion amounts into the culture media, biological functionality was maintained over 10 days due to the incorporation of MACF microparticles as compared to controls without microparticles. Importantly, we demonstrated the utility of fluorinated microparticles in reducing the number of hypoxic cells within the core regions of spheroids, while also promoting the diffusion of other small molecules in and out of these 3D in vitro models.

Progress of 3D Bioprinting in Organ Manufacturing

Three-dimensional (3D) bioprinting is a family of rapid prototyping technologies, which assemble biomaterials, including cells and bioactive agents, under the control of a computer-aided design model in a layer-by-layer fashion. It has great potential in organ manufacturing areas with the combination of biology, polymers, chemistry, engineering, medicine, and mechanics. At present, 3D bioprinting technologies can be used to successfully print living tissues and organs, including blood vessels, skin, bones, cartilage, kidney, heart, and liver. The unique advantages of 3D bioprinting technologies for organ manufacturing have improved the traditional medical level significantly. In this article, we summarize the latest research progress of polymers in bioartificial organ 3D printing areas. The important characteristics of the printable polymers and the typical 3D bioprinting technologies for several complex bioartificial organs, such as the heart, liver, nerve, and skin, are introduced.

A cell based assay for evaluating binding and uptake of an antibody using hepatic nonparenchymal cells

Evaluation of the binding and uptake of an antibody in liver non-parenchymal cells (NPC), including liver sinusoidal endothelial cells, is important for revealing its pharmacokinetic (PK) behavior, since NPC has important roles in eliminating an antibody from the blood via the Fc fragment of IgG receptor IIB (FcγRIIB). However, there is currently no in vitro quantitative assay using NPC. This study reports on the development of a cell-based assay for evaluating the binding and uptake of such an antibody using liver NPC of mice and monkeys. In mice, the FcγRIIB-expressing cells were identified in the CD146-positive and CD45-negative fraction by flow cytometry. A titration assay was performed to determine the PK parameters, and the obtained parameter was comparable to that determined by the fitting of the in vivo PK. This approach was also extended to NPC from monkeys. The concentration-dependent binding and uptake was measured to determine the PK parameters using monkey NPC, the FcγRIIB-expressing fraction of which was identified by CD31 and CD45. The findings presented herein demonstrate that the in vitro liver NPC assay using flow cytometry is a useful tool to determine the binding and uptake of biologics and to predict the PK.

Inhibition of miR-188-5p alleviates hepatic fibrosis by significantly reducing the activation and proliferation of HSCs through PTEN/PI3K/AKT pathway

Persistent hepatic damage and chronic inflammation in liver activate the quiescent hepatic stellate cells (HSCs) and cause hepatic fibrosis (HF). Several microRNAs regulate the activation and proliferation of HSCs, thereby playing a critical role in HF progression. Previous studies have reported that miR‐188‐5p is dysregulated during the process of HF. However, the role of miR‐188‐5p in HF remains unclear. This study investigated the potential role of miR‐188‐5p in HSCs and HF. Firstly, we validated the miR‐188‐5p expression in primary cells isolated from liver of carbon tetrachloride (CCl₄)‐induced mice, TGF‐β1‐induced LX‐2 cells, livers from 6‐month high‐fat diet (HFD)‐induced rat and 4‐month HFD‐induced mice NASH models, and human non‐alcoholic fatty liver disease (NAFLD) patients. Furthermore, we used miR‐188‐5p inhibitors to investigate the therapeutic effects of miR‐188‐5p inhibition in the HFD + CCl₄ induced in vivo model and the potential role of miR‐188‐5p in the activation and proliferation of HSCs. This present study reported that miR‐188‐5p expression is significantly increased in the human NAFLD, HSCs isolated from liver of CCl₄ induced mice, and in vitro and in vivo models of HF. Mimicking the miR‐188‐5p resulted in the up‐regulation of HSC activation and proliferation by directly targeting the phosphatase and tensin homolog (PTEN). Moreover, inhibition of miR‐188‐5p reduced the activation and proliferation markers of HSCs through PTEN/AKT pathway. Additionally, in vivo inhibition of miR‐188‐5p suppressed the HF parameters, pro‐fibrotic and pro‐inflammatory genes, and fibrosis. Collectively, our results uncover the pro‐fibrotic role of miR‐188‐5p. Furthermore, we demonstrated that miR‐188‐5p inhibition decreases the severity of HF by reducing the activation and proliferation of HSCs through PTEN/AKT pathway.

Biomaterial-based cell delivery strategies to promote liver regeneration

Chronic liver disease and cirrhosis is a widespread and untreatable condition that leads to lifelong impairment and eventual death. The scarcity of liver transplantation options requires the development of new strategies to attenuate disease progression and reestablish liver function by promoting regeneration. Biomaterials are becoming an increasingly promising option to both culture and deliver cells to support in vivo viability and long-term function. There is a wide variety of both natural and synthetic biomaterials that are becoming established as delivery vehicles with their own unique advantages and disadvantages for liver regeneration. We review the latest developments in cell transplantation strategies to promote liver regeneration, with a focus on the use of both natural and synthetic biomaterials for cell culture and delivery. We conclude that future work will need to refine the use of these biomaterials and combine them with novel strategies that recapitulate liver organization and function in order to translate this strategy to clinical use.

Autophagy-induced p62 accumulation is required for curcumol to regulate KLF5-mediated angiogenesis in liver sinusoidal endothelial cells

Liver pathological angiogenesis is considered to be one of the key events in the development of liver fibrosis. Autophagy is a defense and stress regulation mechanism. However, whether autophagy regulates pathological angiogenesis in liver fibrosis is still questionable. Here, we aimed to study how curcumol regulated liver sinusoidal endothelial cells (LSECs) angiogenesis through autophagy. We found that curcumol (10, 20 and 40 μM) could inhibit the expression of angiogenesis markers in the LSECs. Importantly, we showed that curcumol might influence LSEC pathological angiogenesis by regulating autophagy level. Furthermore, we indicated that the transcription factor Krüppel-like factor 5 (KLF5) was considered as a key target for curcumol to regulate LSEC angiogenesis. Interestingly, we also suggested that autophagy was as a potential mechanism for curcumol to restrain KLF5 expression. Increased autophagy level could impair the suppression effect of curcumol on KLF5. Fascinatingly, our results indicated that curcumol inhibited autophagy and led to p62 accumulation, which might be a regulation mechanism of KLF5 degradation. Finally, in mice liver fibrosis model, we unanimously showed that curcumol (30 mg/kg) inhibited pathological angiogenesis by reducing LSEC autophagy level and suppressing KLF5 expression. Collectively, these results provided a deeper insight into the molecular mechanism of curcumol to inhibit LSEC pathological angiogenesis during liver fibrosis.

Human Nonalcoholic Steatohepatitis on a Chip

Nonalcoholic steatohepatitis (NASH), an advanced stage of nonalcoholic fatty liver disease (NAFLD), is a rapidly growing and global health problem compounded by the current absence of specific treatments. A major limiting factor in the development of new NASH therapies is the absence of models that capture the unique cellular structure of the liver microenvironment and recapitulate the complexities of NAFLD progression to NASH. Organ-on-a-chip platforms have emerged as a powerful approach to dynamically model diseases and test drugs. Herein, we describe a NASH-on-a-chip platform. Four main types of human primary liver cells (hepatocytes [HCs], Kupffer cells, liver sinusoidal endothelial cells, and hepatic stellate cells [HSCs]) were cocultured under microfluidic dynamics. Our chip-based model successfully recapitulated a functional liver cellular microenvironment with stable albumin and urea secretion for at least 2 weeks. Exposing liver chips to a lipotoxic environment led to gradual development of NASH phenotypic characteristics, including intracellular lipid accumulation, hepatocellular ballooning, HSC activation, and elevation of inflammatory and profibrotic markers. Further, exposure of the chip to elafibranor, a drug under study for the therapy of NASH, inhibited the development of NASH-specific hallmarks, causing an ~8-fold decrease in intracellular lipids, a 3-fold reduction in number of ballooned HCs, a significant reduction in HSC activation, and a significant decrease in the levels of inflammatory and profibrotic markers compared with controls. Conclusion: We have successfully developed a microfluidic NASH-on-a-chip platform that recapitulates the main NASH histologic endpoints in a single chip and that can emerge as a powerful noninvasive, human-relevant, in vitro platform to study disease pathogenesis and develop novel anti-NASH drugs.

Curcumol inhibits KLF5-dependent angiogenesis by blocking the ROS/ERK signaling in liver sinusoidal endothelial cells

AIMS

Liver fibrosis is a difficult problem in the medical field. We previously reported that curcumol, a bioactive substance, may inhibit the pathological angiogenesis of liver sinusoidal endothelial cells (LSECs) and play a good anti-hepatic fibrosis effect. However, the mechanism of curcumol inhibiting angiogenesis in LSEC needs to be further clarified. Here, we focus on how curcumol inhibits LSEC angiogenesis in liver fibrosis.

MATERIALS AND METHODS

Primary rat LSECs were cultured in vitro, and various molecular experiments including real-time PCR, western blot, immunofluorescence, tube formation assay and transwell migration assay were used to clarify the potential mechanism of curcumol. Carbon tetrachloride (CCl4) was applied to create a mouse liver fibrosis model. Blood and livers were taken to elucidate the efficacy of curcumol in vivo.

KEY FINDINGS

We found that curcumol could effectively inhibit LSEC angiogenesis in vitro. Interestingly, this process may depend on curcumol's inhibition of the expression of transcription factor KLF5. Mice experiment also showed that curcumol could alleviate chronic liver injury by reducing KLF5 expression. In addition, we suggested that curcumol could reduce the production of mitochondrial ROS and improve mitochondrial morphology in LSEC. More importantly, we proved that curcumol could suppress KLF5-mediated LSEC angiogenesis by inhibiting ROS/ERK signaling.

SIGNIFICANCE

We suggested that transcription factor KLF5 could be considered as a new target molecule of curcumol in improving liver fibrosis, and pointed out that curcumol targeted ROS/ERK-mediated KLF5 expression could inhibit LSEC angiogenesis. This provided a new theoretical basis for curcumol to ameliorate liver fibrosis.

Photonic-chip assisted correlative light and electron microscopy

Correlative light and electron microscopy (CLEM) unifies the versatility of light microscopy (LM) with the high resolution of electron microscopy (EM), allowing one to zoom into the complex organization of cells. Here, we introduce photonic chip assisted CLEM, enabling multi-modal total internal reflection fluorescence (TIRF) microscopy over large field of view and high precision localization of the target area of interest within EM. The photonic chips are used as a substrate to hold, to illuminate and to provide landmarking of the sample through specially designed grid-like numbering systems. Using this approach, we demonstrate its applicability for tracking the area of interest, imaging the three-dimensional (3D) structural organization of nano-sized morphological features on liver sinusoidal endothelial cells such as fenestrations (trans-cytoplasmic nanopores), and correlating specific endo-lysosomal compartments with its cargo protein upon endocytosis.

Tinguely et al. develop a photonic chip-based correlative light-electron microscopy system to generate co-registered multi-modal total internal reflection fluorescence microscopy (TIRF) and electron microscopy (EM) images of biological samples at nanometer scale.

Signaling molecules orchestrating liver regenerative medicine

The liver is in charge of more than 500 functions in the human body, which any damage and failure to the liver can significantly compromise human life. Numerous studies are being carried out in regenerative medicine, as a potential driving force, toward alleviating the need for liver donors and fabrication of a 3D-engineered transplantable hepatic tissue. Liver tissue engineering brings three main factors of cells, extracellular matrix (ECM), and signaling molecules together, while each of these three factors tries to mimic the physiological state of the tissue to direct tissue regeneration. Signaling molecules play a crucial role in directing tissue fabrication in liver tissue engineering. When mimicking the natural in vivo process of regeneration, it is tightly associated with three main phases of differentiation, proliferation (progression), and tissue maturation through vascularization while directing each of these phases is highly regulated by the specific signaling molecules. The understanding of how these signaling molecules guide the dynamic behavior of regeneration would be a tool for further tailoring of bioengineered systems to help the liver regeneration with many cellular, molecular, and tissue-level functions. Hence, the signaling molecules come to aid all these phases for further improvements toward the clinical use of liver tissue engineering as the goal.

Biomimetic niches reveal the minimal cues to trigger apical lumen formation in single hepatocytes

The symmetry breaking of protein distribution and cytoskeleton organization is an essential aspect for the development of apicobasal polarity. In embryonic cells this process is largely cell autonomous, while differentiated epithelial cells collectively polarize during epithelium formation. Here, we demonstrate that the de novo polarization of mature hepatocytes does not require the synchronized development of apical poles on neighbouring cells. De novo polarization at the single-cell level by mere contact with the extracellular matrix and immobilized cadherin defining a polarizing axis. The creation of these single-cell liver hemi-canaliculi allows unprecedented imaging resolution and control and over the lumenogenesis process. We show that the density and localization of cadherins along the initial cell-cell contact act as key triggers of the reorganization from lateral to apical actin cortex. The minimal cues necessary to trigger the polarization of hepatocytes enable them to develop asymmetric lumens with ectopic epithelial cells originating from the kidney, breast or colon.

Folic acid and RAAS blockers in ischemia/reperfusion-induced hepatic injury: A current mechanistic concept for understanding the incidence, significance & outcome

Hepatic ischemia-reperfusion injury (IRI) is not only one of the pathophysiological process involving the liver, but also a complex systemic process affecting multiple tissues and organs. IRI after liver transplant occurs due to in major resections and occlusion of vessels, or during the perioperative period, leads to acute liver failure which shows the dynamic process that involves two interrelated phases of local ischemic insult and inflammation-mediated reperfusion injury and has an impact on morbidity and mortality. The renin-angiotensin-aldosterone system (RAAS) is activated locally in the injured cells by the occurrence of I/R, which plays an essential role in the fate of the damaged tissue. However, a preclinical study explores the protective role of RAAS inhibitor in acute liver injury in a model of inflammation caused by ischemia and reperfusion. In-addition to RAAS blockers in monotherapy does not effectively block the complete pathway. Thus, the present study is designed to explore the effect of combined folic acid with RAAS blockers in combination, produce a synergistic effect. Moreover, in this review, we will describe the understanding of the possible incidence of downregulatory molecular mechanisms associated with renin-angiotensin-aldosterone system and the significance & outcome of the combination of folic acid and RAAS blockers in liver injury due to ischemia/reperfusion.

Role of phosphatidylinositol 3-kinase signaling pathway in radiation-induced liver injury

Transforming growth factor-β1 (TGF-β1) is one of critical cytokines in radiation-induced liver injury. Hepatic stellate cells (HSC) are activated in the early stage of radiation-induced liver injury. However, it is currently unclear whether phosphatidylinositol 3-kinase (PI3K/Akt) signal pathway is activated in radiation-induced liver injury. Herein, male Sprague-Dawley rats were irradiated with 6 MV X-rays (30 Gy) on the right liver. Next, Hematoxylin and eosin staining, Masson staining, and electron microscopy were performed to examine pathological changes. Immunohistochemistry was performed to assess the expression of TGF-β1, α-SMA, and p-Akt (S473) in liver tissues. In vitro, rat HSC cell line HSC-T6 cells were given different doses of 6 MV X-ray irradiation (10 and 20 Gy) and treated with LY294002. The expression of α-SMA and p-Akt in mRNA and protein levels were measured by reverse transcription-polymerase chain reactioin (RT-PCR) and Western blot. TGF-β1 expression was detected by enzyme-linked immuno sorbent assay (ELISA). After irradiation, the liver tissues showed obvious pathological changes, indicating the establishment of the radiation-induced liver injury. Expression levels of TGF-β1, α-SMA, and p-Akt (S473) protein in liver tissues were significantly increased after irradiation, and this increase was in a time-dependent manner, suggesting the activation of HSC and PI3K/Akt signal pathway. in vitro experiments showed that the TGF-β1 secreted by HSCs, and the expression of Akt and α-SMA at mRNA and protein levels were significantly increased in irradiation groups. However, the expression of TGF-β1, Akt, and α-SMA were significantly decreased in PI3K/Akt signal pathway inhibitor LY294002-treated group. Our results suggest that during radiation-induced liver injury, HSCs are activated by TGF-β1-mediated PI3K/Akt signal pathway.

Annexin A5 regulates hepatic macrophage polarization via directly targeting PKM2 and ameliorates NASH

Nonalcoholic steatohepatitis (NASH), the progressive form of nonalcoholic fatty liver disease (NAFLD), is becoming a common chronic liver disease with the characteristics of steatosis, inflammation and fibrosis. Macrophage plays an important role in the development of NASH. In this study, Annexin A5 (Anx A5) is identified with the special effect on hepatic macrophage phenotype shift from M1 to M2. And it is further demonstrated that Anx A5 significantly switches metabolic reprogramming from glycolysis to oxidative phosphorylation in activated macrophages. Mechanistically, the main target of Anx A5 in energy metabolism is confirmed to be pyruvate kinase M2 (PKM2). And we following reveal that Anx A5 directly interacts with PKM2 at ASP101, LEU104 and ARG106, inhibits phosphorylation of Y105, and promotes PKM2 tetramer formation. In addition, based on the results of PKM2 inhibitor (compound 3k) and the phosphorylated mutation (PKM2 (Y105E)), it is proved that Anx A5 exhibits the function in macrophage polarization dependently on PKM2 activity. In vivo studies also show that Anx A5 improves steatosis, inflammation and fibrosis in NASH mice due to specially regulating hepatic macrophages via interaction with PKM2. Therefore, we have revealed a novel function of Anx A5 in hepatic macrophage polarization and HFD-induced NASH, providing important insights into the metabolic reprogramming, which is important for NASH therapy.

High Glucose-Aggravated Hepatic Insulin Resistance: Role of the NLRP3 Inflammasome in Kupffer Cells

OBJECTIVE

This study aimed to investigate whether the NLRP3 inflammasome in Kupffer cells (KCs) can be activated in response to high glucose (HG) and to evaluate its influence on hepatic insulin sensitivity.

METHODS

Primary KCs and hepatocytes were isolated from mice, and lipid accumulation, glucose output, and insulin sensitivity of hepatocytes were investigated after culturing either alone or with KCs exposed to HG. The influence of HG-induced NLRP3 inflammasome activation in KCs on insulin sensitivity of hepatocytes was examined. Treatment with gadolinium trichloride caused KC depletion, and, subsequently, a streptozotocin-induced hyperglycemic mouse model was used to confirm the influence of KCs on hepatic insulin sensitivity.

RESULTS

Hepatocytes cocultured with KCs showed enhanced lipid accumulation, glucose output, and impaired insulin sensitivity when exposed to HG. Enhanced NLRP3 inflammasome activation was also evident in both hepatocytes and KCs. Moreover, KCs that were pretreated with caspase-1 inhibitor, NLRP3 inhibitor, and NLRP3 small interfering RNA corrected coculture-induced aberrances in insulin action and NLRP3 inflammasome activation in hepatocytes. KC coculture also increased interleukin-1β (IL-1β)-mediated nuclear factor-κB (NF-κB) activation in hepatocytes. In hyperglycemic mice, KC depletion inhibited NLRP3 inflammasome activation and improved hepatic insulin sensitivity.

CONCLUSIONS

NLRP3 inflammasome activation impaired insulin sensitivity through KC-derived IL-1β-mediated NF-κB activation in hepatocytes exposed to HG.

The Influence of Chronic Liver Diseases on Hepatic Vasculature: A Liver-on-a-chip Review

In chronic liver diseases and hepatocellular carcinoma, the cells and extracellular matrix of the liver undergo significant alteration in response to chronic injury. Recent literature has highlighted the critical, but less studied, role of the liver vasculature in the progression of chronic liver diseases. Recent advancements in liver-on-a-chip systems has allowed in depth investigation of the role that the hepatic vasculature plays both in response to, and progression of, chronic liver disease. In this review, we first introduce the structure, gradients, mechanical properties, and cellular composition of the liver and describe how these factors influence the vasculature. We summarize state-of-the-art vascularized liver-on-a-chip platforms for investigating biological models of chronic liver disease and their influence on the liver sinusoidal endothelial cells of the hepatic vasculature. We conclude with a discussion of how future developments in the field may affect the study of chronic liver diseases, and drug development and testing.

Development of Bioengineered Organ Using Biological Acellular Rat Liver Scaffold and Hepatocytes

The increasing demand for organs for transplantation necessitates the development of substitutes to meet the structural and physiological functions. Tissue decellularization and recellularization aids in retaining the three-dimensional integrity, biochemical composition, tissue ultra-structure, and mechanical behavior, which makes them functionally suitable for organ transplantation. Herein, we attempted to rebuild functional liver grafts in small animal model (Wistar rat) with a potential of translation. A soft approach was adopted using 0.1% SDS (Sodium Dodecyl Sulfate) for decellularization and primary hepatocytes were used as a potential cell source for recellularization. The decellularization process was evaluated and confirmed using histology, DNA content, ultra-structure analysis. The resultant scaffold was re-seeded with the rat hepatocytes and their biocompatibility was assessed by its metabolic functions and gene expression. The structural components of the Extracellular matrix (ECM) (Laminins, Collagen type I, Reticulins) were conserved and the liver cell-specific proteins like CK-18, alpha-fetoprotein, albumin were expressed in the recellularized scaffold. The functionality and metabolic activity of the repopulated scaffold were evident from the albumin and urea production. Expression of Cytokeratin-19 (CK-19), Glucose 6-Phosphatase (G6P), Albumin, Gamma Glutamyl Transferase (GGT) genes has distinctly confirmed the translational signals after the repopulation process. Our study clearly elucidates that the native extracellular matrix of rat liver can be utilized as a scaffold for effective recellularization for whole organ regeneration.

ANGPTL8 enhances insulin sensitivity by directly activating insulin-mediated AKT phosphorylation

ANGPTL8 is a 22-KDa protein in the angiopoietin-like family. It is a liver-derived hormone that dynamically regulates glucose metabolism after refeeding. The mechanism of its regulation of glucose metabolism is unclear. We analyzed the effect of ANGPTL8 overexpression on glucose tolerance in the mouse liver by tail vein hydrodynamic transfection. The mechanism of ANGPTL8 improving insulin sensitivity was analyzed by the overexpression or knockdown of ANGPTL8 in mouse primary hepatocytes through in vitro synthetic mRNA and siRNA technology. The key site of ANGPTL8 protein regulating this signal pathway was screened by DNA point mutation and fragment truncation. The results showed that ANGPTL8 may directly regulate AKT protein phosphorylation in the insulin-mediated PI3K/AKT signaling pathway to improve insulin sensitivity. Ser94 and Thr98 are the key sites of ANGPTL8 protein in activating AKT protein phosphorylation. Present results indicate that ANGPTL8 may be a potential new agent to reduce postprandial blood glucose.

Human Liver Spheroids as a Model to Study Aetiology and Treatment of Hepatic Fibrosis

Non-alcoholic fatty liver disease affects approximately one billion adults worldwide. Non-alcoholic steatohepatitis (NASH) is a progressive disease and underlies the advancement to liver fibrosis, cirrhosis, and hepatocellular carcinoma, for which there are no FDA-approved drug therapies. We developed a hetero-cellular spheroid system comprised of primary human hepatocytes (PHH) co-cultured with crude fractions of primary human liver non-parenchymal cells (NPC) from several matched or non-matched donors, to identify phenotypes with utility in investigating NASH pathogenesis and drug screening. Co-culture spheroids displayed stable expression of hepatocyte markers (albumin, CYP3A4) with the integration of stellate (vimentin, PDGFRβ), endothelial (vWF, PECAM1), and CD68-positive cells. Several co-culture spheroids developed a fibrotic phenotype either spontaneously, primarily observed in PNPLA3 mutant donors, or after challenge with free fatty acids (FFA), as determined by COL1A1 and αSMA expression. This phenotype, as well as TGFβ1 expression, was attenuated with an ALK5 inhibitor. Furthermore, CYP2E1, which has a strong pro-oxidant effect, was induced by NPCs and FFA. This system was used to evaluate the effects of anti-NASH drug candidates, which inhibited fibrillary deposition following 7 days of exposure. In conclusion, we suggest that this system is suitable for the evaluation of NASH pathogenesis and screening of anti-NASH drug candidates.

Functionality of primary hepatic non-parenchymal cells in a 3D spheroid model and contribution to acetaminophen hepatotoxicity

In addition to hepatocytes, the liver comprises a host of specialised non-parenchymal cells which are important to consider in the development of in vitro models which are both physiologically and toxicologically relevant. We have characterized a 3D co-culture system comprising primary human hepatocytes (PHH) and non-parenchymal cells (NPC) and applied it to the investigation of acetaminophen-induced toxicity. Firstly, we titrated ratios of PHH:NPC and confirmed the presence of functional NPCs via both immunohistochemistry and activation with both LPS and TGF-β. Based on these data we selected a ratio of 2:1 PHH:NPC for further studies. We observed that spheroids supplemented with NPCs were protected against acetaminophen (APAP) toxicity as determined by ATP (up to threefold difference in EC50 at day 14 compared to hepatocytes alone) and glutathione depletion, as well as miR-122 release. APAP metabolism was also altered in the presence of NPCs, with significantly lower levels of APAP-GSH detected. Expression of several CYP450 enzymes involved in the bioactivation of APAP was also lower in NPC-containing spheroids. Spheroids containing NPCs also expressed higher levels of miRNAs which have been implicated in APAP-induced hepatotoxicity, including miR-382 and miR-155 which have potential roles in liver regeneration and inflammation, respectively. These data indicate that the interaction between hepatocytes and NPCs can have significant metabolic and toxicological consequences important for the correct elucidation of hepatic safety mechanisms.

Advanced Biomaterials and Processing Methods for Liver Regeneration: State-of-the-Art and Future Trends

Liver diseases contribute markedly to the global burden of mortality and disease. The limited organ disposal for orthotopic liver transplantation results in a continuing need for alternative strategies. Over the past years, important progress has been made in the field of tissue engineering (TE). Many of the early trials to improve the development of an engineered tissue construct are based on seeding cells onto biomaterial scaffolds. Nowadays, several TE approaches have been developed and are applied to one vital organ: the liver. Essential elements must be considered in liver TE-cells and culturing systems, bioactive agents or growth factors (GF), and biomaterials and processing methods. The potential of hepatocytes, mesenchymal stem cells, and others as cell sources is demonstrated. They need engineered biomaterial-based scaffolds with perfect biocompatibility and bioactivity to support cell proliferation and hepatic differentiation as well as allowing extracellular matrix deposition and vascularization. Moreover, they require a microenvironment provided using conventional or advanced processing technologies in order to supply oxygen, nutrients, and GF. Herein the biomaterials and the conventional and advanced processing technologies, including cell-sheets process, 3D bioprinting, and microfluidic systems, as well as the future trends in these major fields are discussed.

Cell release during perfusion reflects cold ischemic injury in rat livers

The global shortage of donor organs has made it crucial to deeply understand and better predict donor liver viability. However, biomarkers that effectively assess viability of marginal grafts for organ transplantation are currently lacking. Here, we showed that hepatocytes, sinusoidal endothelial, stellate, and liver-specific immune cells were released into perfusates from Lewis rat livers as a result of cold ischemia and machine perfusion. Perfusate comparison analysis of fresh livers and cold ischemic livers showed that the released cell profiles were significantly altered by the duration of cold ischemia. Our findings show for the first time that parenchymal cells are released from organs under non-proliferative pathological conditions, correlating with the degree of ischemic injury. Thus, perfusate cell profiles could serve as potential biomarkers of graft viability and indicators of specific injury mechanisms during organ handling and transplantation. Further, parenchymal cell release may have applications in other pathological conditions beyond organ transplantation.

DNA damage in kidney and parenchymal and non-parenchymal liver cells of adult Wistar rats after subchronic oral treatment with tembotrione

DNA damage in the liver and kidney cells of adult male Wistar rats was studied using the comet assay after a 28-day oral administration of tembotrione at doses of 0.0007, 0.0013 and 0.7 mg/kg b.w./day [AOEL (acceptable operator exposure level), REL (residual exposure level) and 1000× AOEL]. As a descriptor of DNA damage, tail intensity was used. Antioxidant status was assessed by activity of glutathione peroxidase (GPx). Significant DNA damage was recorded in the kidney cells at all three doses as compared to negative control. In parenchymal liver cells, significant DNA damage was observed in AOEL and 1000× AOEL doses, while in non-parenchymal liver cells, only AOEL-treated group was significantly different compared to negative control. In both types of liver cells, REL and 1000× AOEL doses were significantly different from the AOEL dose. No significant changes in GPx activity compared to control were observed at any exposure level. The results of the present study suggest that repeated in vivo exposure to tembotrione led to low-level DNA instability in kidney and liver cells. Exposure to the highest tembotrione dose showed a relatively weak response with the alkaline comet assay. Further research should focus on the effects of this herbicide in other models along with different exposure scenarios.

In Vitro Human Liver Model of Nonalcoholic Steatohepatitis by Coculturing Hepatocytes, Endothelial Cells, and Kupffer Cells

The liver has a complex and unique microenvironment with multiple cell-cell interactions and internal vascular networks. Although nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease with multiple phases, no proper model could fully recapitulate the in vivo microenvironment to understand NAFLD progression. Here, an in vitro human liver model of NAFLD by coculturing human hepatocytes, umbilical vein endothelial cells (HUVECs), and Kupffer cells (KCs) into spheroids is presented. Analysis of indirect cross-talk using conditioned media between steatotic spheroids-composed of hepatocellular carcinoma-derived cells (HepG2) and HUVECs-and mouse KCs reveals that the latter can be activated showing increased cell area, elevated production of reactive oxygen species (ROS), and proinflammatory cytokines. Spheroids incorporating human KCs (HKCs) can also be induced into steatotic stage by supplementing fat. Steatotic spheroids with/without HKCs show different levels of steatotic stages through lipid accumulation and ROS production. Steatotic spheroids made from an immortalized hepatic progenitor cell line (HepaRG) compared to those made from HepG2 cells display similar trends of functionality, but elevated levels of proinflammatory cytokines, and improved reversibility of steatosis. The in vitro human liver system proposed makes strides in developing a model to mimic and monitor the progression of NAFLD.

Current progress in hepatic tissue regeneration by tissue engineering

Liver, as a vital organ, is responsible for a wide range of biological functions to maintain homeostasis and any type of damages to hepatic tissue contributes to disease progression and death. Viral infection, trauma, carcinoma, alcohol misuse and inborn errors of metabolism are common causes of liver diseases are a severe known reason for leading to end-stage liver disease or liver failure. In either way, liver transplantation is the only treatment option which is, however, hampered by the increasing scarcity of organ donor. Over the past years, considerable efforts have been directed toward liver regeneration aiming at developing new approaches and methodologies to enhance the transplantation process. These approaches include producing decellularized scaffolds from the liver organ, 3D bio-printing system, and nano-based 3D scaffolds to simulate the native liver microenvironment. The application of small molecules and micro-RNAs and genetic manipulation in favor of hepatic differentiation of distinct stem cells could also be exploited. All of these strategies will help to facilitate the application of stem cells in human medicine. This article reviews the most recent strategies to generate a high amount of mature hepatocyte-like cells and updates current knowledge on liver regenerative medicine.

Gastrointestinal Failure in Critically Ill Patients With Cirrhosis

Gastrointestinal failure (GIF) is frequent in patients managed in the intensive care units and manifests as gut paralysis or ileus. GIF is often associated with sepsis or multiorgan failure. In critically ill patients, the precipitating causes of GIF include inflammation, sepsis, electrolyte abnormalities, and acidosis. It is possible that GIF is associated with an increase in bacterial translocation, especially in those with cirrhosis and portal hypertension, and this may play a significant pathogenic or prognostic role in acute-on-chronic liver failure (ACLF). The critical care literature suggests that GIF is associated with a higher mortality risk. In this review, we summarize the evidence for a potential association between GIF and ACLF and propose treatment options for the management of GIF. Moreover, we suggest GIF to be considered as another organ failure when the severity of ACLF is assessed.

A high-throughput microfluidic microphysiological system (PREDICT-96) to recapitulate hepatocyte function in dynamic, re-circulating flow conditions

Microphysiological systems (MPSs) are dynamic cell culture systems that provide micro-environmental and external cues to support physiologically relevant, organ-specific functions. Recent progresses in MPS fabrication technologies have enabled the development of advanced models to capture microenvironments with physiological relevance, while increasing throughput and reducing material-based artefacts. In addition to conventional cell culture systems, advanced MPSs are emerging as ideal contenders for disease modeling and incorporation into drug screening. Since liver is a central organ for drug metabolism, liver-on-chip models have been developed to recapitulate hepatic microenvironment with varying complexities, while allowing long-term culture. Recently, we have developed a novel thermoplastic, oxygen-permeable MPS for primary human hepatocyte (PHH) culture. Herein, we have adapted and extended the MPS to a) a 96 microfluidic array (PREDICT-96 array) and b) integrated a novel, ultra-low volume, re-circulating pumping system (PREDICT-96 pump) - collectively known as the PREDICT-96 platform. The PREDICT-96 platform conforms to the industrial standard 96-well footprint and enables media re-circulation. First, we demonstrate the introduction of PHHs into the PREDICT-96 array using standard handling procedures for multi-well plates and allow cells to stabilize in static conditions. Next, we introduce recirculating flow into the bottom channel (using PREDICT-96 pump) to mimic mass transport in vivo. Our results indicate an increase in metabolic and secretory functions of PHHs in the PREDICT-96 platform, and their maintenance over 10 days of flow. Furthermore, long-term culture with fluid flow allows for the periodic introduction of media components (e.g., fatty acids, cytokines) and capture cellular responses to chronic stimuli. The low-volume footprint of the pump and small media volume in the MPS allow for the interrogation of hepatic responses incorporating secretion feedback to a stimulus, which is essential for disease model development and drug interrogation. We envision future development of this liver model to incorporate key primary hepatic cells, multi-cellular co-cultures and adaptation, integration with high-throughput analytical tools.