Effect of Circulation Parameters on Functional Status of HepaRG Spheroids Cultured in Microbioreactor

Microfluidic Chip as a Tool for Effective In Vitro Evaluation of Cyclophosphamide Prodrug Toxicity

Most drugs are metabolized in the liver, which can lead to their activation or inactivation with a change in the parent compound pharmacology, as well as liver damage by active metabolites. Preclinical animal studies of drug safety do not always predict its effect on humans due to species specificity. Thus, for the rapid drug screening, and especially prodrugs, an in vitro system is required that allows predicting xenobiotic cytotoxicity with consideration of their metabolism in liver cells. The use of a microfluidic chip (BioClinicum) made it possible to cultivate a 2D culture of human HaCaT keratinocytes with spheroids of human hepatoma HepaRG cells. After incubation in a specially selected universal serum-free medium containing 3.8 mM cyclophosphamide, pronounced death of HaCaT cells was observed in comparison with culturing in the absence of liver cells.

Comparison of gene expression and biotransformation activity of HepaRG cells under static and dynamic culture conditions

Flow conditions have been shown to be important in improving longevity and functionality of primary hepatocytes, but the impact of flow on HepaRG cells is largely unknown. We studied the expression of genes encoding CYP enzymes and transporter proteins and CYP1 and CYP3A4 activity during 8 weeks of culture in HepaRG cells cultured under static conditions (conventional 24-/96-well plate culture with common bicarbonate/CO2 buffering) and under flow conditions in an organ-on-chip (OOC) device. Since the OOC-device is a closed system, bicarbonate/CO2 buffering was not possible, requiring application of another buffering agent, such as HEPES. In order to disentangle the effects of HEPES from the effects of flow, we also applied HEPES-supplemented medium in static cultures and studied gene expression and CYP activity. We found that cells cultured under flow conditions in the OOC-device, as well as cells cultured under static conditions with HEPES-supplemented medium, showed more stable gene expression levels. Furthermore, only cells cultured in the OOC-device showed relatively high baseline CYP1 activity, and their gene expression levels of selected CYPs and transporters were most similar to gene expression levels in human primary hepatocytes. However, there was a decrease in baseline CYP3A4 activity under flow conditions compared to HepaRG cells cultured under static conditions. Altogether, the present study shows that HepaRG cells cultured in the OOC-device were more stable than in static cultures, being a promising in vitro model to study hepatoxicity of chemicals upon chronic exposure.

Microfluidic devices for studying coagulation biology

The ability to study the behavior of cells, proteins, and cell-cell or cell-protein interactions under dynamic forces such as shear stress under fluid flow, provides a more accurate understanding of the physiopathology of hemostasis. This review touches upon the traditional methods for studying blood coagulation and platelet aggregation and provides an overview on cellular and protein response to shear stress. We also elaborate on the biological aspects of how cells recognize mechanical forces and convert them into biochemical signals that can drive various signaling pathways. We give a detailed description of the various types of microfluidic devices that are employed to study the complex processes of platelet aggregation and blood coagulation under flow conditions as well as to investigate endothelial shear-response. We also highlight works mimicking artificial vessels as platforms to study the mechanisms of coagulation, and finish our review by describing anticipated clinical uses of microfluidics devices and their standardization.

New Frontiers for Biofabrication and Bioreactor Design in Microphysiological System Development

Microphysiological systems (MPSs) have been proposed as an improved tool to recreate the complex biological features of the native niche with the goal of improving in vitro-in vivo extrapolation. In just over a decade, MPS technologies have progressed from single-tissue chips to multitissue plates with integrated pumps for perfusion. Concurrently, techniques for biofabrication of complex 3D constructs for regenerative medicine and 3D in vitro models have evolved into a diverse toolbox for micrometer-scale deposition of cells and cell-laden bioinks. However, as the complexity of biological models increases, experimental throughput is often compromised. This review discusses the existing disparity between MPS complexity and throughput, then examines an MPS-terminated biofabrication line to identify the hurdles and potential approaches to overcoming this disparity.

Developing scalable cultivation systems of hepatic spheroids for drug metabolism via genomic and functional analyses

Spheroids, a widely used three-dimensional (3D) culture model, are standard in hepatocyte culture as they preserve long-term hepatocyte functionality and enhance survivability. In this study, we investigated the effects of three operation modes in 3D culture - static, orbital shaking, and under vertical bidirectional flow using spheroid forming units (SFUs) on hepatic differentiation and drug metabolism to propose the best for mass production of functionally enhanced spheroids. Spheroids in SFUs exhibited increased hepatic gene expression, albumin secretion, and cytochrome P450 3A4 (CYP3A4) activity during the differentiation period (12 days). SFUs advantages include facilitated mass production and a relatively earlier peak of CYP3A4 activity. However, CYP3A4 activity was not well maintained under dimethyl sulfoxide (DMSO)-free conditions (13-18 days), dramatically reducing drug metabolism capability. Continued shear stimulation without differentiation stimuli in assay conditions markedly attenuated CYP3A4 activity, which was less severe in static conditions. In this condition, SFU spheroids exhibited dedifferentiation characteristics, such as increased proliferation and Notch signaling genes. We found that the dedifferentiation could be overcome by using the serum-free medium formulation. Therefore, we suggest that SFUs represent the best option for the mass production of functionally improved spheroids and so the serum-free conditions should be maintained during drug metabolism analysis.

"Branched Tail" Oxyquinoline Inhibitors of HIF Prolyl Hydroxylase: Early Evaluation of Toxicity and Metabolism Using Liver-on-a-chip

BACKGROUND

"Branched tail" oxyquinolines, and adaptaquin in particular, are potent HIF prolyl hydroxylase inhibitors showing promising results in in vivo hemorrhagic stroke models. The further improvement of the potency resulted in identification of a number of adaptaquin analogs. Early evaluation of toxicity and metabolism is desired right at the step of lead selection.

OBJECTIVE

The aim of the study is to characterize the toxicity and metabolism of adaptaquin and its new improved analogs.

METHOD

Liver-on-a-chip technology with differentiated HepaRG cells followed by LC-MS detection of the studied compounds and metabolites of the P450 substrate-inhibitor panel for CYP2B6, CYP2C9, CYP2C19, and CYP3A4.

RESULTS

The optimized adaptaquin analogs show no toxicity up to a 100-fold increased range over EC50. The drugs are metabolized by CYP3A4 and CYP2B6 as shown with the use of the cytochrome P450 substrate-inhibitor panel designed and optimized for preclinical evaluation of drugs' in vitro biotransformation on a 3D human histotypical cell model using "liver-on-a-chip" technology. Activation of CYP2B6 with the drugs tested has been observed. A scheme for adaptaquin oxidative conversion is proposed.

CONCLUSION

The optimized adaptaquin analogs are suitable for further preclinical trials. Activation of CYP2B6 with adaptaquin and its variants points to a potential increase in Tylenol toxicity if administered together.

Which cytochrome P450 metabolizes phenazepam? Step by step in silico, in vitro, and in vivo studies

BACKGROUND

Phenazepam (bromdihydrochlorphenylbenzodiazepine) is the original Russian benzodiazepine tranquilizer belonging to 1,4-benzodiazepines. There is still limited knowledge about phenazepam's metabolic liver pathways and other pharmacokinetic features.

METHODS

To determine phenazepam's metabolic pathways, the study was divided into three stages: in silico modeling, in vitro experiment (cell culture study), and in vivo confirmation. In silico modeling was performed on the specialized software PASS and GUSAR to evaluate phenazepam molecule affinity to different cytochromes. The in vitro study was performed using a hepatocytes' cell culture, cultivated in a microbioreactor to produce cytochrome P450 isoenzymes. The culture medium contained specific cytochrome P450 isoforms inhibitors and substrates (for CYP2C9, CYP3A4, CYP2C19, and CYP2B6) to determine the cytochrome that was responsible for phenazepam's metabolism. We also measured CYP3A activity using the 6-betahydroxycortisol/cortisol ratio in patients.

RESULTS

According to in silico and in vitro analysis results, the most probable metabolizer of phenazepam is CYP3A4. By the in vivo study results, CYP3A activity decreased sufficiently (from 3.8 [95% CI: 2.94-4.65] to 2.79 [95% CI: 2.02-3.55], p=0.017) between the start and finish of treatment in patients who were prescribed just phenazepam.

CONCLUSIONS

Experimental in silico and in vivo studies confirmed that the original Russian benzodiazepine phenazepam was the substrate of CYP3A4 isoenzyme.

In Vitro Model for Studying of the Role of IGFBP6 Gene in Breast Cancer Metastasizing

IGFBP6 gene plays an important role in the pathogenesis of breast cancer. In this work, we performed knockdown of IGFBP6 gene in MDA-MB-231 cells and obtained a stable cell line. Knockdown of IGFBP6 gene was confirmed by the real-time PCR. The influence of IGFBP6 gene on migration and proliferation of breast cancer cells was studied. Knockdown of IGFBP6 gene reduced migration activity of MDA-MB-231 cells and increased their proliferation rate. This in vitro cell model can be used for the further analysis of the role of IGFBP6 gene in the pathogenesis of breast cancer.

Role of IGFBP6 Protein in the Regulation of Epithelial-Mesenchymal Transition Genes

Protein IGFBP6 plays an important role in the pathogenesis of many malignant tumors, including breast cancer. The relationship between IGFBP6 protein and the expression of genes associated with the epithelial-mesenchymal transition is studied. Gene IGFBP6 knockdown does not trigger the epithelial-mesenchymal transition in MDA-MB-231 cells, but modifies significantly the expression of many genes involved in this process. A decrease of IGFBP6 expression can involve a decrease in the expression of N-cadherin and transcription factor Slug.

Mimicking liver sinusoidal structures and functions using a 3D-configured microfluidic chip

Physiologically, four major types of hepatic cells - the liver sinusoidal endothelial cells, Kupffer cells, hepatic stellate cells, and hepatocytes - reside inside liver sinusoids and interact with flowing peripheral cells under blood flow. It is hard to mimic an in vivo liver sinusoid due to its complex multiple cell-cell interactions, spatiotemporal construction, and mechanical microenvironment. Here we developed an in vitro liver sinusoid chip by integrating the four types of primary murine hepatic cells into two adjacent fluid channels separated by a porous permeable membrane, replicating liver's key structures and configurations. Each type of cells was identified with its respective markers, and the assembled chip presented the liver-specific unique morphology of fenestration. The flow field in the liver chip was quantitatively analyzed by computational fluid dynamics simulations and particle tracking visualization tests. Intriguingly, co-culture and shear flow enhance albumin secretion independently or cooperatively, while shear flow alone enhances HGF production and CYP450 metabolism. Under lipopolysaccharide (LPS) stimulations, the hepatic cell co-culture facilitated neutrophil recruitment in the liver chip. Thus, this 3D-configured in vitro liver chip integrates the two key factors of shear flow and the four types of primary hepatic cells to replicate key structures, hepatic functions, and primary immune responses and provides a new in vitro model to investigate the short-duration hepatic cellular interactions under a microenvironment mimicking the physiology of a liver.

Structure-activity relationship for branched oxyquinoline HIF activators: Effect of modifications to phenylacetamide "tail"

HIF prolyl hydroxylase is a major regulator of HIF stability. Branched tail oxyquinolines have been identified as specific inhibitors of HIF prolyl hydroxylase and recently demonstrated clear benefits in various scenarios of neuronal failure. The structural optimization for branched tail oxyquinolines containing an acetamide bond has been performed in the present study using HIF1 ODD-luc reporter assay. The special attention has been paid to the length of a linker between acetamide group and phenyl ring, as well as substitutions in the phenyl ring in the other branch of the tail. The optimized version of branched tail oxyquinolines is 3-fold more potent than the original one identified before and shows a submicromolar EC₅₀ in the reporter assay. The compounds have been studied in a "liver-on-a-chip" device to question their hepatotoxicity towards differentiated human HepaRG "hepatocytes": the absence of hepatotoxicity is observed up to 200 μM concentrations for all studied derivatives of branched tail oxyquinolines.

Development of a Specific Substrate-Inhibitor Panel (Liver-on-a-Chip) for Evaluation of Cytochrome P450 Activity

We developed a cytochrome P450 substrate-inhibitor panel for preclinical in vitro evaluation of drugs in a 3D histotypical microfluidic cell model of human liver (liver-on-a-chip technology). The concentrations of substrates and inhibitors were optimized to ensure reliable detection of the principal metabolites by HPLC-mass-spectroscopy. The selected specific substrate-inhibitor pairs, namely bupropion/2-phenyl-2-(1-piperidinyl)propane) for evaluation of CYP2B6B activity, tolbutamide/sulfaphenazole for CYP2C9, omeprazole/(+)-N-benzylnirvanol for CYP2C19, and testosterone/ketoconazole for CYP3A4, enable reliable evaluation of the drug metabolism pathway. In contrast to animal models characterized by species-specific expression profile and activity of cytochrome P450 isoforms, our in vitro model reflects the metabolism of human hepatocytes in vivo.