bims-orenst Biomed News
on Organs-on-chips and engineered stem cell models
Issue of 2020‒12‒20
eleven papers selected by
Joram Mooiweer
University of Groningen

  1. Micromachines (Basel). 2020 Dec 16. pii: E1112. [Epub ahead of print]11(12):
      Microfluidic devices are used extensively in the development of new in vitro cell culture models like organs-on-chips. A typical feature of such devices is the patterning of biological hydrogels to offer cultured cells and tissues a controlled three-dimensional microenvironment. A key challenge of hydrogel patterning is ensuring geometrical confinement of the gel, which is generally solved by inclusion of micropillars or phaseguides in the channels. Both of these methods often require costly cleanroom fabrication, which needs to be repeated even when only small changes need be made to the gel geometry, and inadvertently expose cultured cells to non-physiological and mechanically stiff structures. Here, we present a technique for facile patterning of hydrogel geometries in microfluidic chips, but without the need for any confining geometry built into the channel. Core to the technique is the use of laminar flow patterning to create a hydrophilic path through an otherwise hydrophobic microfluidic channel. When a liquid hydrogel is injected into the hydrophilic region, it is confined to this path by the surrounding hydrophobic regions. The various surface patterns that are enabled by laminar flow patterning can thereby be rendered into three-dimensional hydrogel structures. We demonstrate that the technique can be used in many different channel geometries while still giving the user control of key geometric parameters of the final hydrogel. Moreover, we show that human umbilical vein endothelial cells can be cultured for multiple days inside the devices with the patterned hydrogels and that they can be stimulated to migrate into the gel under the influence of trans-gel flows. Finally, we demonstrate that the patterned gels can withstand trans-gel flow velocities in excess of physiological interstitial flow velocities without rupturing or detaching. This novel hydrogel-patterning technique addresses fundamental challenges of existing methods for hydrogel patterning inside microfluidic chips, and can therefore be applied to improve design time and the physiological realism of microfluidic cell culture assays and organs-on-chips.
    Keywords:  3D cell culture; cell migration; fabrication; hydrogel; microfluidics; surface patterning
  2. Methods Mol Biol. 2021 ;2258 205-219
      A preclinical blood-brain barrier (BBB) model is important for the study of fundamental transport mechanisms and in accessing the delivery of small molecules and antibodies that target brain. Transwell assays for BBB models are easy to create and use but lack the true 3D anatomy of the brain microvasculature and also often the cell-cell and cell-matrix interactions that are important in ensuring a tight BBB. Here we describe the formation of a BBB that expresses neurovascular membrane transporters, tight junction, and extracellular matrix proteins using the coculture of human-induced pluripotent stem cell-derived endothelial cells (iPSC-EC), brain pericytes (PC), and astrocytes (AC) in a microfluidic device. The BBB model recapitulates human brain vascular permeability with values that are lower than conventional in vitro models and are comparable to in vivo measurements in rat brain. This in vitro BBB model can therefore be used to screen for brain-targeting drugs or to study neurovascular functions.
    Keywords:  BBB preclinical model; BBB-on-a-chip; Human blood–brain barrier; In vitro drug testing; Microphysiological systems
  3. Micromachines (Basel). 2020 Dec 16. pii: E1118. [Epub ahead of print]11(12):
      In vitro models of the liver have a good simulation of the micro-liquid environment inside the human liver and the communication between cell tissues, which provides an important research tool for drug research and liver disease treatment. In this paper, we designed a 3D liver chip and real-time monitoring system based on microfluidic technology. The in vitro model of the liver on the chip was established by the three-dimensional microfluidic chip pipeline and the corresponding microwell array. Meanwhile, the culture medium is continuously injected on the chip, and the electrochemical impedance spectroscopy and near-infrared spectroscopy of the liver chip are recorded and analyzed from day one to day five. When the 3D cultured liver chip in vitro model reached a certain period and stabilized, paracetamol with varying gradients of concentration was applied to the cultured cells for drug resistance testing. The experimental results show that the liver chip and its monitoring system designed in this paper can maintain 100% cell viability of hepatocytes in vitro for a long time. Furthermore, it can meet the requirements of measurement technologies such as electrical impedance measurement and near-infrared spectroscopy in real-time, providing a stable culture platform for the further study of organ chips.
    Keywords:  drug testing; electrochemical impedance spectrum; in vitro model of the liver; microfluidic technology; near-infrared spectrum
  4. Nat Rev Gastroenterol Hepatol. 2020 Dec 17.
      Microphysiology systems (MPS), also called organs-on-chips and tissue chips, are miniaturized functional units of organs constructed with multiple cell types under a variety of physical and biochemical environmental cues that complement animal models as part of a new paradigm of drug discovery and development. Biomimetic human liver MPS have evolved from simpler 2D cell models, spheroids and organoids to address the increasing need to understand patient-specific mechanisms of complex and rare diseases, the response to therapeutic treatments, and the absorption, distribution, metabolism, excretion and toxicity of potential therapeutics. The parallel development and application of transdisciplinary technologies, including microfluidic devices, bioprinting, engineered matrix materials, defined physiological and pathophysiological media, patient-derived primary cells, and pluripotent stem cells as well as synthetic biology to engineer cell genes and functions, have created the potential to produce patient-specific, biomimetic MPS for detailed mechanistic studies. It is projected that success in the development and maturation of patient-derived MPS with known genotypes and fully matured adult phenotypes will lead to advanced applications in precision medicine. In this Review, we examine human biomimetic liver MPS that are designed to recapitulate the liver acinus structure and functions to enhance our knowledge of the mechanisms of disease progression and of the absorption, distribution, metabolism, excretion and toxicity of therapeutic candidates and drugs as well as to evaluate their mechanisms of action and their application in precision medicine and preclinical trials.
  5. Lab Chip. 2020 Dec 15.
      The poor predictive power of existing preclinical models has spurred efforts to develop human-relevant models for accurate assessment of drug safety. In this work, we developed a multi-organoids-on-a-chip system derived from human induced pluripotent stem cells (hiPSCs), which allows for the assessment of the cardiac safety of an antidepressant drug, following liver metabolism in vitro. This liver-heart organoids-on-chip device contains compartmentalized chambers separated by a porous membrane, which permits the co-culture of 3D human liver organoids in the upper multi-well chamber and cardiac organoids in the bottom micropillar array simultaneously. The co-cultured liver and heart organoids on chip maintained good viability and human organ-specific functions respectively, including the synthesis of albumin and urea of liver organoids, and the beating function of cardiac organoids. In particular, the liver organoids displayed proper metabolic capabilities with high expression of CYP450 enzyme genes. Clomipramine, a widely used antidepressant drug, can be metabolized into an active metabolite (desmethylclomipramine) through the hepatic CYP450 enzymes of liver organoids on chip identified by mass spectrometry. After exposure to 1 μM clomipramine in the liver chamber for 24 h and 48 h, the co-cultured heart organoids in the bottom layer showed significantly reduced cell viability, impaired functions of cardiac beating and calcium flux, indicating the hepatic metabolism-dependent cardiotoxicity induced by clomipramine. By combining stem cell biology and microengineered technology, this proposed hiPSC-derived multi-organoids-on-a-chip system can reflect human organ-specific functions, as well as the complex process of drug metabolism and responses at the multi-organ level. It may provide a novel platform for the assessment of drug effectiveness and safety in vitro.
  6. Lab Chip. 2020 Dec 15.
      Previous in vitro studies have reported on the use of direct current electric fields (DC-EFs) to regulate vascular endothelial permeability, which is important for tissue regeneration and wound healing. However, these studies have primarily used static 2D culture models that lack the fluid mechanical forces associated with blood flow experienced by endothelial cells (ECs) in vivo. Hence, the effect of DC-EF on ECs under physiologically relevant fluid forces is yet to be systematically evaluated. Using a 3D microfluidic model of a bifurcating vessel, we report the role of DC-EF on regulating endothelial permeability when co-applied with physiologically relevant fluid forces that arise at the vessel bifurcation. The application of a 70 V m-1 DC-EF simultaneously with 1 μL min-1 low perfusion rate (generating 3.8 dyn cm-2 stagnation pressure at the bifurcation point and 0.3 dyn cm-2 laminar shear stress in the branched vessel) increased the endothelial permeability 7-fold compared to the static control condition (i.e., without flow and DC-EF). When the perfusion rate was increased to 10 μL min-1 (generating 38 dyn cm-2 stagnation pressure at the bifurcation point and 3 dyn cm-2 laminar shear stress in the branched vessel) while maintaining the same electrical stimulation, a 4-fold increase in endothelial permeability compared to the static control was observed. The lower increase in endothelial permeability for the higher fluid forces but the same DC-EF suggests a competing role between fluid forces and the applied DC-EF. Moreover, the observed increase in endothelial permeability due to combined DC-EF and flow was transient and dependent on the Akt signalling pathway. Collectively, these findings provide significant new insights into how the endothelium serves as an electro-mechanical interface for regulating vessel permeability.
  7. Stem Cell Reports. 2020 Dec 03. pii: S2213-6711(20)30461-6. [Epub ahead of print]
      Human heart (patho)physiology is now widely studied using human pluripotent stem cells, but the immaturity of derivative cardiomyocytes has largely limited disease modeling to conditions associated with mutations in cardiac ion channel genes. Recent advances in tissue engineering and organoids have, however, created new opportunities to study diseases beyond "channelopathies." These synthetic cardiac structures allow quantitative measurement of contraction, force, and other biophysical parameters in three-dimensional configurations, in which the cardiomyocytes in addition become more mature. Multiple cardiac-relevant cell types are also often combined to form organized cardiac tissue mimetic constructs, where cell-cell, cell-extracellular matrix, and paracrine interactions can be mimicked. In this review, we provide an overview of some of the most promising technologies being implemented specifically in personalized heart-on-a-chip models and explore their applications, drawbacks, and potential for future development.
    Keywords:  cardiovascular disease modeling; engineered heart tissue; force of contraction; heart-on-a-chip; human pluripotent stem cells
  8. Methods Mol Biol. 2021 ;2258 221-239
      Cancer mortality predominantly results from distant metastases that are undetectable at diagnosis and escape initial therapies to lie as dormant micrometastases for years. To study the behavior of micrometastases-how they resist initial treatments and then awaken from a dormant state-we utilize the Legacy LiverChip®, an all-human ex vivo hepatic microphysiological system. The functional liver bioreactor, comprising hepatocytes and non-parenchymal cells in a 3D microperfused culture format, mimics the dormant-emergent metastatic progression observed in human patients: (a) a subpopulation of cancer cells spontaneously enter dormancy, (b) cycling cells are eliminated by standard chemotherapies, while quiescent dormant cells remain, and (c) chemoresistant dormant cells can be stimulated to emerge. The system effluent and tissue can be queried for proteomic and genomic data, immunofluorescent imaging as well as drug efficacy and metabolism. This microphysiological system continues to provide critical insights into the biology of dormant and re-emergent micrometastases and serves as an accessible tool to identify new therapeutic strategies targeting the various stages of metastasis, while concurrently evaluating antineoplastic agent efficacy for metastasis, metabolism, and dose-limiting toxicity.
    Keywords:  Cancer; Dormancy; Emergence; Microphysiological system; Model of metastasis; Organ-on-a-chip
  9. Nat Protoc. 2020 Dec 11.
      Early post-implantation human embryonic development has been challenging to study due to both technical limitations and ethical restrictions. Proper modeling of the process is important for infertility and toxicology research. Here we provide details of the design and implementation of a microfluidic device that can be used to model human embryo development. The microfluidic human embryo model is established from human pluripotent stem cells (hPSCs), and the resulting structures exhibit molecular and cellular features resembling the progressive development of the early post-implantation human embryo. The compartmentalized configuration of the microfluidic device allows the formation of spherical hPSC clusters in prescribed locations in the device, enabling the two opposite regions of each hPSC cluster to be exposed to two different exogenous chemical environments. Under such asymmetrical chemical conditions, several early post-implantation human embryo developmental landmarks, including lumenogenesis of the epiblast and the resultant pro-amniotic cavity, formation of a bipolar embryonic sac, and specification of primordial germ cells and gastrulating cells (or mesendoderm cells), can be robustly recapitulated using the microfluidic device. The microfluidic human embryo model is compatible with high-throughput studies, live imaging, immunofluorescence staining, fluorescent in situ hybridization, and single-cell sequencing. This protocol takes ~5 d to complete, including microfluidic device fabrication (2 d), cell seeding (1 d), and progressive development of the microfluidic model until gastrulation-like events occur (1-2 d).
  10. Sci Rep. 2020 Dec 18. 10(1): 22294
      The failure of the osteosarcoma conventional therapies leads to the growing need for novel therapeutic strategies. The lack of specificity for the Cancer Stem Cells (CSCs) population has been recently identified as the main limitation in the current therapies. Moreover, the traditional two-dimensional (2D) in vitro models, employed in the drug testing and screening as well as in the study of cell and molecular biology, are affected by a poor in vitro-in vivo translation ability. To overcome these limitations, this work provides two tumour engineering approaches as new tools to address osteosarcoma and improve therapy outcomes. In detail, two different hydroxyapatite-based bone-mimicking scaffolds were used to recapitulate aspects of the in vivo tumour microenvironment, focusing on CSCs niche. The biological performance of human osteosarcoma cell lines (MG63 and SAOS-2) and enriched-CSCs were deeply analysed in these complex cell culture models. The results highlight the fundamental role of the tumour microenvironment proving the mimicry of osteosarcoma stem cell niche by the use of CSCs together with the biomimetic scaffolds, compared to conventional 2D culture systems. These advanced 3D cell culture in vitro tumour models could improve the predictivity of preclinical studies and strongly enhance the clinical translation.
  11. Biomicrofluidics. 2020 Nov;14(6): 064107
      Hepatoprotectant is critical for the treatment of liver disease. This study first reported the application of a liver chip in the hepatoprotective effect assessment. We first established a biomimetic sinusoid-on-a-chip by laminating four types of hepatic cell lines (HepG2, HUVEC, LX-2, and U937 cells) in a single microchannel with the help of laminar flow in the microchannel and some micro-fences. This chip was straightforward to fabricate and operate and was able to be long-term cultured. It also demonstrated better hepatic activity (cell viability, albumin synthesis, urea secretion, and cytochrome P450 enzyme activities) over the traditional planar cell culture model. Then, we loaded three hepatoprotectants (tiopronin, bifendatatum, and glycyrrhizinate) into the chip followed by the addition of acetaminophen as a toxin. We successfully observed the hepatoprotective effect of these hepatoprotectants in the chip, and we also found that bifendatatum predominantly reduced alanine transaminase secretion, tiopronin predominantly reduced lactate dehydrogenase secretion, and glycyrrhizinate predominantly reduced aspartate transaminase secretion, which revealed the different mechanisms of these hepatoprotectants and provided a clue for following molecular biological study of the protecting mechanism.