3D microfluidic liver cultures as a physiological preclinical tool for hepatitis B virus infection

3D Primary Hepatocyte Culture Systems for Analyses of Liver Diseases, Drug Metabolism, and Toxicity: Emerging Culture Paradigms and Applications

Recent research has shown that the maintenance of relevant liver functions ex vivo requires models in which the cells exhibit an in vivo-like phenotype, often achieved by reconstitution of appropriate cellular interactions. Multiple different models have been presented that differ in the cells utilized, media, and culture conditions. Furthermore, several technologically different approaches have been presented including bioreactors, chips, and plate-based systems in fluidic or static media constituting of chemically diverse materials. Using such models, the ability to predict drug metabolism, drug toxicity, and liver functionality have increased tremendously as compared to conventional in vitro models in which cells are cultured as 2D monolayers. Here, the authors highlight important considerations for microphysiological systems for primary hepatocyte culture, review current culture paradigms, and discuss their opportunities for studies of drug metabolism, hepatotoxicity, liver biology, and disease.

Decellularized human liver scaffold-based three-dimensional culture system facilitate hepatitis B virus infection

Hepatitis B virus (HBV) study is hampered by lacking of idea cell model which support effective HBV infection and meanwhile recapitulate hepatocyte biology function in vivo. In this study, we developed decellularized human liver scaffolds for cell culture and further applied for HBV infection. As a result, primary human hepatocytes (PHHs) engrafted into liver scaffolds and maintained differentiation with stable albumin secretion and liver-specific gene expression. Comparing to mono-layer cell culture, scaffold-based three-dimensional (3D) culture system significantly augment HBV DNA (including cccDNA), RNA level as well as HBsAg secretion. Moreover, HepG2-NTCP cells cultured on 3D system exhibited higher infection efficiency and longer infection period in vitro. In addition, HBV DNA level was suppressed when anti-HBV medicine Entecavir (ETV) introduced into HepG2-NTCP 3D system. Herein, we evaluated the potential of decellularized human liver scaffold-based in 3D cell culture and disclosed that scaffold-based 3D culture system can facilitate HBV infection in vitro. This 3D culture system could be further applied in HBV-related study. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1744-1753, 2019.

A global scientific strategy to cure hepatitis B

Chronic hepatitis B virus (HBV) infection is a global public health challenge on the same scale as tuberculosis, HIV, and malaria. The International Coalition to Eliminate HBV (ICE-HBV) is a coalition of experts dedicated to accelerating the discovery of a cure for chronic hepatitis B. Following extensive consultation with more than 50 scientists from across the globe, as well as key stakeholders including people affected by HBV, we have identified gaps in our current knowledge and new strategies and tools that are required to achieve HBV cure. We believe that research must focus on the discovery of interventional strategies that will permanently reduce the number of productively infected cells or permanently silence the covalently closed circular DNA in those cells, and that will stimulate HBV-specific host immune responses which mimic spontaneous resolution of HBV infection. There is also a pressing need for the establishment of repositories of standardised HBV reagents and protocols that can be accessed by all HBV researchers throughout the world. The HBV cure research agenda outlined in this position paper will contribute markedly to the goal of eliminating HBV infection worldwide.

A cell lines derived microfluidic liver model for investigation of hepatotoxicity induced by drug-drug interaction

The poor metabolic ability of cell lines fails to meet the requirements of an in vitro model for drug interaction testing which is crucial for the development or clinical application of drugs. Herein, we describe a liver sinusoid-on-a-chip device composed of four kinds of transformed cell lines (HepG2 cells, LX-2 cells, EAhy926 cells, and U937 cells) that were ordered in a physiological distribution with artificial liver blood flow and biliary efflux flowing in the opposite direction. This microfluidic device applied three-dimensional culturing of HepG2 cells with high density (107 ml-1), forming a tightly connected monolayer of EAhy926 cells and achieving the active transport of drugs in HepG2 cells. Results showed that the device maintained synthetic and secretory functions, preserved cytochrome P450 1A1/2 and uridine diphosphate glucuronyltransferase enzymatic activities, as well as sensitivity of drug metabolism. The cell lines derived device enables the investigation of a drug-drug interaction study. We used it to test the hepatotoxicity of acetaminophen and the following combinations: "acetaminophen + rifampicin," "acetaminophen + omeprazole," and "acetaminophen + ciprofloxacin." The variations in hepatotoxicity of the combinations compared to acetaminophen alone, which is not found in a 96-well plate model, in the device were -17.15%, 14.88%, and -19.74%. In addition, this result was similar to the one tested by the classical primary hepatocyte plate model (-13.22%, 13.51%, and -15.81%). Thus, this cell lines derived liver model provides an alternative to investigate drug hepatotoxicity, drug-drug interaction.

Modelling the endocrine pancreas in health and disease

Diabetes mellitus is a multifactorial disease affecting increasing numbers of patients worldwide. Progression to insulin-dependent diabetes mellitus is characterized by the loss or dysfunction of pancreatic β-cells, but the pathomechanisms underlying β-cell failure in type 1 diabetes mellitus and type 2 diabetes mellitus are still poorly defined. Regeneration of β-cell mass from residual islet cells or replacement by β-like cells derived from stem cells holds great promise to stop or reverse disease progression. However, the development of new treatment options is hampered by our limited understanding of human pancreas organogenesis due to the restricted access to primary tissues. Therefore, the challenge is to translate results obtained from preclinical model systems to humans, which requires comparative modelling of β-cell biology in health and disease. Here, we discuss diverse modelling systems across different species that provide spatial and temporal resolution of cellular and molecular mechanisms to understand the evolutionary conserved genotype-phenotype relationship and translate them to humans. In addition, we summarize the latest knowledge on organoids, stem cell differentiation platforms, primary micro-islets and pseudo-islets, bioengineering and microfluidic systems for studying human pancreas development and homeostasis ex vivo. These new modelling systems and platforms have opened novel avenues for exploring the developmental trajectory, physiology, biology and pathology of the human pancreas.

Cell and Animal Models for Studying Hepatitis B Virus Infection and Drug Development

Many cell culture and animal models have been used to study hepatitis B virus (HBV) replication and its effects in the liver; these have facilitated development of strategies to control and clear chronic HBV infection. We discuss the advantages and limitations of systems for studying HBV and developing antiviral agents, along with recent advances. New and improved model systems are needed. Cell culture systems should be convenient, support efficient HBV infection, and reproduce responses of hepatocytes in the human body. We also need animals that are fully permissive to HBV infection, convenient for study, and recapitulate human immune responses to HBV and effects in the liver. High-throughput screening technologies could facilitate drug development based on findings from cell and animal models.

Synthesizing Living Tissues with Microfluidics

In native tissues, various cell types organize and spatiotemporally function and communicate with neighboring or remote cells in a highly regulated way. How can we replicate these amazing functional structures in vitro? From the view of a chemist, the heterogeneous cells and extracellular matrix (ECM) could be regarded as various chemical substrate materials for "synthetic" reactions during tissue engineering. But how can we accelerate these reactions? Microfluidics provides ideal solutions. Microfluidics could be metaphorically regarded as a miniature "biofactory", whereas the on-chip critical chemical cues such as biomolecule gradients and physical cues such as geometrical confinement, topological guidance, and mechanical stimulations, along with the external stimulations such as light, electricity, acoustics, and magnetics, could be regarded as "catalytic cues" which can accelerate the "synthetic reactions" by precisely and effectively manipulating a series of cell behaviors including cell adhesion, migration, growth, proliferation, differentiation, cell-cell interaction, and cell-matrix interaction to reduce activation energy of the "synthetic reactions". Thus, on the microfluidics platform, the "biofactory", various "synthetic" reactions take place to change the substrate materials (cells and ECM) into products (tissues) in a nonlinear way, which is a typical feature of a biological process. By precisely organizing the substrate materials and spatiotemporally controlling the activity of the products, as a "biofactory", the microfluidics system can not only "synthesize" living tissues but also recreate physiological or pathophysiological processes such as immune responses, angiogenesis, wound healing, and tumor metastasis in vitro to bring insights into the mechanisms underlying these processes taking place in vivo. In this Account, we borrow the concept of chemical "synthesis" to describe how to "synthesize" artificial tissues using microfluidics from a chemist's view. Accelerated by the built-in physiochemical cues on microfluidics and external stimulations, various tissues could be "synthesized" on a microfluidics platform. We summarize that there are "step-by-step synthesis" and "one-step synthesis" on microfluidics for creating desired tissues with unprecedented precision, accuracy, and speed. In recent years, researchers developed various microfluidic techniques including creating adhesive domains for mediating reverse and precise adhesion, chemical gradients for directing cell growth, geometrical confinements and topological cues for manipulating cell migration, and mechanics for stimulating cell differentiation. By employing and orchestrating these on-chip tissue "synthetic" conditions, "step-by-step synthesis" could be realized on chips to develop multilayered tissues such as blood vessels. "One-step synthesis" on chips could develop functional three-dimensional tissue structures such as neural networks or nephron-like structures. Based on these on-chip studies, many critical physiological and pathophysiological processes such as wound healing, tumor metastasis, and atherosclerosis could be deeply investigated, and the drugs or therapeutic approaches could also be evaluated or screened conveniently. The "synthetic tissues on microfluidics" system would pave an avenue for precise creation of artificial tissues for not only fundamental research but also biomedical applications such as tissue engineering.

Hepatitis B Virus Evasion From Cyclic Guanosine Monophosphate-Adenosine Monophosphate Synthase Sensing in Human Hepatocytes

Chronic hepatitis B virus (HBV) infection is a major cause of chronic liver disease and cancer worldwide. The mechanisms of viral genome sensing and the evasion of innate immune responses by HBV infection are still poorly understood. Recently, the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) was identified as a DNA sensor. In this study, we investigated the functional role of cGAS in sensing HBV infection and elucidate the mechanisms of viral evasion. We performed functional studies including loss-of-function and gain-of-function experiments combined with cGAS effector gene expression profiling in an infectious cell culture model, primary human hepatocytes, and HBV-infected human liver chimeric mice. Here, we show that cGAS is expressed in the human liver, primary human hepatocytes, and human liver chimeric mice. While naked relaxed-circular HBV DNA is sensed in a cGAS-dependent manner in hepatoma cell lines and primary human hepatocytes, host cell recognition of viral nucleic acids is abolished during HBV infection, suggesting escape from sensing, likely during packaging of the genome into the viral capsid. While the hepatocyte cGAS pathway is functionally active, as shown by reduction of viral covalently closed circular DNA levels in gain-of-function studies, HBV infection suppressed cGAS expression and function in cell culture models and humanized mice. Conclusion: HBV exploits multiple strategies to evade sensing and antiviral activity of cGAS and its effector pathways.

In vitro and ex vivo systems at the forefront of infection modeling and drug discovery

Bacterial infections and antibiotic resistant bacteria have become a growing problem over the past decade. As a result, the Centers for Disease Control predict more deaths resulting from microorganisms than all cancers combined by 2050. Currently, many traditional models used to study bacterial infections fail to precisely replicate the in vivo bacterial environment. These models often fail to incorporate fluid flow, bio-mechanical cues, intercellular interactions, host-bacteria interactions, and even the simple inclusion of relevant physiological proteins in culture media. As a result of these inadequate models, there is often a poor correlation between in vitro and in vivo assays, limiting therapeutic potential. Thus, the urgency to establish in vitro and ex vivo systems to investigate the mechanisms underlying bacterial infections and to discover new-age therapeutics against bacterial infections is dire. In this review, we present an update of current in vitro and ex vivo models that are comprehensively changing the landscape of traditional microbiology assays. Further, we provide a comparative analysis of previous research on various established organ-disease models. Lastly, we provide insight on future techniques that may more accurately test new formulations to meet the growing demand of antibiotic resistant bacterial infections.

Recapitulation of hepatitis B virus-host interactions in liver organoids from human induced pluripotent stem cells

Therapies against hepatitis B virus (HBV) have improved in recent decades; however, the development of individualized treatments has been limited by the lack of individualized infection models. In this study, we used human induced pluripotent stem cell (hiPSC) to generate a functional liver organoid (LO) that inherited the genetic background of the donor, and evaluated its application in modeling HBV infection and exploring virus-host interactions. To establish a functional hiPSC-LO, we cultured hiPSC-derived endodermal, mesenchymal, and endothelial cells with a chemically defined medium in a three-dimensional microwell culture system. Based on cell-cell interactions, these cells could organize themselves and gradually differentiate into a functional organoid, which exhibited stronger hepatic functions than hiPSC derived hepatic like cell (HLC). Moreover, the functional LO demonstrated more susceptibility to HBV infection than hiPSC-HLC, and could maintain HBV propagation and produce infectious virus for a prolonged duration. Furthermore, we found that virus infection could cause hepatic dysfunction of hiPSC-LOs, with down-regulation of hepatic gene expression, induced release of early acute liver failure markers, and altered hepatic ultrastructure. Therefore, our study demonstrated that HBV infection in hiPSC-LOs could recapitulate virus life cycle and virus induced hepatic dysfunction, suggesting that hiPSC-LOs may provide a promising individualized infection model for the development of individualized treatment for hepatitis.

3D microfluidic in vitro model and bioinformatics integration to study the effects of Spatholobi Caulis tannin in cervical cancer

Cervical cancer is considered the fourth most common malignant disease in women. Recently, tannin from Spatholobi Caulis (TTS) has been shown to have potent anticancer and antiproliferative characteristics in a few preliminary studies. This experiment used 3D microfluidic, flow cytometry, and gene chip technology to study the efficacy and mechanism of action of TTS, as well as molecular docking technology to study the effect of drugs on related proteins. The cell survival rates of the five groups measured by the 3D microfluidic chip were 94%, 85%, 64%, 55%, and 42%, respectively. With the increase in drug concentration, the cell survival rate gradually decreased. Apoptosis rates detected in the five groups were 2.12%, 15.87%, 33.40%, 41.13%, and 55.10%, respectively. These data suggest that TTS can promote cell apoptosis. The percentages of cells in the G0/G1 phase were 43.39%, 55.07%, 59.57%, 64.56%, and 67.39% in the five groups, respectively. TTS was demonstrated to inhibit the conversion of cells from G0/G1 to S phase and G2/M phase and inhibit gene and protein synthesis to block cell proliferation. TTS can effectively modulate pathogenic proteins. The results confirmed the efficacy of TTS against HeLa cells and that TTS can be used as an adjunct in cervical cancer prevention and treatment.

When Hepatitis B Virus Meets Interferons

Chronic hepatitis B virus (HBV) infection imposes a severe burden on global public health. Currently, there are no curative therapies for millions of chronic HBV-infected patients (Lok et al., 2017). Interferon (IFN; including pegylated IFN) is an approved anti-HBV drug that not only exerts direct antiviral activity, but also augments immunity against HBV infection. Through a systematic review of the literature, here we summarize and present recent progress in research regarding the interactions between IFN and HBV as well as dissect the antiviral mechanisms of IFN. We focus on inhibition of HBV replication by IFN-stimulated genes (ISGs) as well as inhibition of IFN signaling by HBV and viral proteins. Finally, we briefly discuss current IFN-based HBV treatment strategies. This review may help to better understand the mechanisms involved in the therapeutic action of IFN as well as the crosstalk between IFN and HBV, and facilitate the development of both direct-acting and immunology-based new HBV drugs.