Gut-liver microphysiological systems revealed potential crosstalk mechanism modulating drug metabolism

The small intestine and liver play important role in determining oral drug's fate. Both organs are also interconnected through enterohepatic circulation, which imply there are crosstalk through circulating factors such as signaling molecules or metabolites that may affect drug metabolism. Coculture of hepatocytes and intestinal cells have shown to increase hepatic drug metabolism, yet its crosstalk mechanism is still unclear. In this study, we aim to elucidate such crosstalk by coculturing primary human hepatocytes harvested from chimeric mouse (PXB-cells) and iPSc-derived intestinal cells in a microphysiological systems (MPS). Perfusion and direct oxygenation from the MPS were chosen and confirmed to be suitable features that enhanced PXB-cells albumin secretion, cytochrome P450 (CYP) enzymes activity while also maintaining barrier integrity of iPSc-derived intestine cells. Results from RNA-sequencing showed significant upregulation in gene ontology terms related to fatty acids metabolism in PXB-cells. One of such fatty acids, arachidonic acid, enhanced several CYP enzyme activity in similar manner as coculture. From the current evidences, it is speculated that the release of bile acids from PXB-cells acted as stimuli for iPSc-derived intestine cells to release lipoprotein which was ultimately taken by PXB-cells and enhanced CYP activity.

Standalone cell culture microfluidic device-based microphysiological system for automated cell observation and application in nephrotoxicity tests

Microphysiological systems (MPS) offer an alternative method for culturing cells on microfluidic platforms to model organ functions in pharmaceutical and medical sciences. Although MPS hardware has been proposed to maintain physiological organ function through perfusion culture, no existing MPS can automatically assess cell morphology and conditions online to observe cellular dynamics in detail. Thus, with this study, we aimed to establish a practical strategy for automating cell observation and improving cell evaluation functions with low temporal resolution and throughput in MPS experiments. We developed a versatile standalone cell culture microfluidic device (SCCMD) that integrates microfluidic chips and their peripherals. This device is compliant with the ANSI/SLAS standards and has been seamlessly integrated into an existing automatic cell imaging system. This integration enables automatic cell observation with high temporal resolution in MPS experiments. Perfusion culture of human kidney proximal tubule epithelial cells using the SCCMD improves cell function. By combining the proximal tubule MPS with an existing cell imaging system, nephrotoxicity studies were successfully performed to automate morphological and material permeability evaluation. We believe that the concept of building the ANSI/SLAS-compliant-sized MPS device proposed herein and integrating it into an existing automatic cell imaging system for the online measurement of detailed cell dynamics information and improvement of throughput by automating observation operations is a novel potential research direction for MPS research.

A Kinetic Pump Integrated Microfluidic Plate (KIM-Plate) with High Usability for Cell Culture-Based Multiorgan Microphysiological Systems

Microphysiological systems (MPSs), including organ-on-a-chip (OoC), have attracted attention as a novel method for estimating the effects and side effects of drugs in drug discovery. To reproduce the dynamic in vivo environment, previous MPSs were connected to pump systems to perfuse culture medium. Therefore, most MPSs are not user-friendly and have poor throughput. We aimed to develop a kinetic pump integrated microfluidic plate (KIM-Plate) by applying the stirrer-based micropump to an open access culture plate to improve the usability of MPSs. The KIM-Plate integrates six multiorgan MPS (MO-MPS) units and meets the ANSI/SBS microplate standards. We evaluated the perfusion function of the kinetic pump and found that the KIM-Plate had sufficient agitation effect. Coculture experiments with PXB cells and hiPS intestinal cells showed that the TEER of hiPS intestinal cells and gene expression levels related to the metabolism of PXB cells were increased. Hence, the KIM-Plate is an innovative tool for the easy coculture of highly conditioned cells that is expected to facilitate cell-based assays in the fields of drug discovery and biology because of its usability and high throughput nature.

A Microfluidic Probe Integrated Device for Spatiotemporal 3D Chemical Stimulation in Cells

Numerous in vitro studies have been conducted in conventional static cell culture systems. However, most of the results represent an average response from a population of cells regardless of their local microenvironment. A microfluidic probe is a non-contact technology that has been widely used to perform local chemical stimulation within a restricted space, providing elaborated modulation and analysis of cellular responses within the microenvironment. Although microfluidic probes developed earlier have various potential applications, the two-dimensional structure can compromise their functionality and flexibility for practical use. In this study, we developed a three-dimensional microfluidic probe integrated device equipped with vertically oriented microchannels to overcome crucial challenges and tested the potential utility of the device in biological research. We demonstrated that the device tightly regulated spatial diffusion of a fluorescent molecule, and the flow profile predicted by simulation replicated the experimental results. Additionally, the device modulated the physiological Ca²⁺ response of cells within the restricted area by altering the local and temporal concentrations of biomolecules such as ATP. The novel device developed in this study may provide various applications for biological studies and contribute to further understanding of molecular mechanisms underlying cellular physiology.

A pharmacokinetic-pharmacodynamic model based on multi-organ-on-a-chip for drug-drug interaction studies

In drug discovery, the emergence of unexpected toxicity is often a problem resulting from a poor understanding of the pharmacokinetics of drug-drug interactions (DDI). Organ-on-a-chip (OoC) has been proposed as an in vitro model to evaluate drug efficacy and toxicity in pharmacology, but it has not been applied to DDI studies yet. In this study, we aim to evaluate whether organ-on-a-chip technologies can be applied to DDI studies. To assess the usefulness of OoC for DDI studies, we proposed a multi-organ-on-a-chip (MOoC) with a liver part as the metabolic model and a cancer part as the drug target model, and a pharmacokinetic-pharmacodynamic (PK-PD) model describing the MOoC. An anticancer prodrug, CPT-11, was used to evaluate the drug efficacy of the metabolite in the liver part of the MOoC. To evaluate DDI using the MOoC, the inhibitory effect of simvastatin and ritonavir on the metabolism of CPT-11 was tested. The DDI estimation method was evaluated by comparing the results of the concomitant administration experiment using the MOoC and the results of simulation using the proposed PK-PD model with the estimated parameters. The results were similar, suggesting that the combination of the PK-PD model and the MOoC is a useful way to predict DDI. We conclude that OoC technologies could facilitate a better understanding of pharmacokinetic mechanisms with DDI.

Spatial Chemical Stimulation Control in Microenvironment by Microfluidic Probe Integrated Device for Cell-Based Assay

Cell—cell interactions play an important role in the development and function of multicellular organisms. To investigate these interactions in detail, it is necessary to evaluate the behavior of a cell population when the minimum number of cells in the population is stimulated by some chemical factors. We propose a microfluidic device integrated with microfluidic probe (MFP) functionality; this device is capable of imparting a chemical stimulus to cells within a microenvironment, for cell-based assays. The device contains MFP channels at the walls of the cell culture microchannels, and it can control a localized chemical stimulation area at the scale of a single cell to a few cells using MFP fluid control in a microspace. The results of a finite element method-based simulation indicated that it is possible to control the chemical stimulation area at the scale of a single cell to a few cells by optimizing the MFP channel apex width and the flow ratio. In addition, localized cell staining was demonstrated successfully using a spatial chemical stimulus. We confirmed the device functionality as a novel cell-based assay tool. We succeeded in performing localized cell collection using this method, which suggested that the single cell analysis of a cell monolayer that is subjected to a specific chemical stimulus is possible. The method proposed in this paper can contribute significantly to the fields of cell biology and drug development.