Background: Decreasing the amount of liquid inside microphysiological systems (MPS) can help uncover the presence of toxic drug metabolites. However, maintaining near-physiological volume ratios among blood surrogate and multiple organ mimics is technically challenging. Here, we developed a body cube and tested its ability to support four human tissues (kidney, GI tract, liver, and bone marrow) scaled down from in vivo functional volumes by a factor of 73,000 with 80 μL of cell culture medium (corresponding to ~1/73,000th of in vivo blood volume). Methods: GI tract cells (Caco-2), liver cells (HepG2/C3A), bone marrow cells (Meg-01), and kidney cells (HK-2) were co-cultured inside the body cube with 80 μL of common, recirculating cell culture medium for 72 h. The system was challenged with acetaminophen and troglitazone, and concentrations of aspartate aminotransferase (AST), albumin, and urea were monitored over time. Results: Cell viability analysis showed that 95.5%±3.2% of liver cells, 89.8%±4.7% of bone marrow cells, 82.8%±8.1% of GI tract cells, and 80.1%±11.5% of kidney cells were viable in co-culture for 72 h. Both acetaminophen and troglitazone significantly lowered cell viability in the liver chamber as indicated by viability analysis and a temporary increase of AST in the cell culture medium. Both drugs also lowered urea production in the liver by up to 45%. Conclusions: Cell viability data and the production of urea and albumin indicate that the co-culture of GI tract, liver, bone marrow, and kidney tissues with near-physiological volume ratios of tissues to blood surrogate is possible for up to 72 h. The body-cube was capable of reproducing liver toxicity to HepG2/C3A liver cells via acetaminophen and troglitazone. The developed design provides a viable format for acute toxicity testing with near-physiological blood surrogate to tissue volume ratios.
The outbreak of the novel coronavirus disease 2019 (COVID-19) has since reached pandemic status, with over 93 million cumulative confirmed cases as of January 17th 2021 (1). Vascular complications, including thrombotic microangiopathy, vasculopathy, and intravascular coagulopathy, are of growing concern in patients with COVID-19 as they can lead to devastating vital organ injury at various stages of the disease course (2). Despite the growing concern, there is still limited research on the downstream effects of endothelial cell infection with severe acute respiratory coronavirus 2 (SARS-CoV-2). Considering the potential for virally-driven vascular injury, there is a utility in studying the characteristics that influence the pro-inflammatory hypercoagulability seen among some proportion of patients with COVID-19. Investigating the consequences and long-term disease processes of COVID-19 patients with damage to vasculature will be crucial for informing future avenues of clinical care.
Myocardial infarction together with subsequent heart failures are among the main reasons for death related to cardiovascular diseases (CVD). Restoring cardiac function and replacing scar tissue with healthy regenerated cardiomyocytes (CMs) is a hopeful therapy for heart failure. Human-induced pluripotent stem cell (hiPSC) derived CMs (hiPSC-CMs) offer the advantages of not having significant ethical issues and having negligible immunological rejection compared to other myocardial regeneration methods. hiPSCs can also produce an unlimited number of human CMs, another advantage they have compared with other cell sources for cardiac regeneration. Numerous researchers have focused their work on promoting the functional maturity of hiPSC-CMs, as well as finding out the precise regulatory mechanisms of each differentiation stage together with the economical and practical methods of acquisition and purification. However, the clinical applications of hiPSC-CMs in drug discovery and cardiac regeneration therapy have yet to be achieved. In this review, we present an overview of various methods for improving the differentiation efficiency of hiPSC-CMs and discuss the differences of electrophysiological characteristics between hiPSC-CMs and matured native CMs. We also introduce approaches for obtaining a large quantity of iPSC-CMs, which are needed to achieve biomanufacturing strategies for building biomimetic three-dimensional tissue constructs using combinations of biomaterials and advanced microfabrication techniques. Recent advances in specific iPSC technology-based drug screening platforms and regeneration therapies can suggest future directions for personalized medicine in biomedical applications.
BACKGROUND:Decreasing the amount of liquid inside microphysiological systems (MPS) can help uncover the presence of toxic drug metabolites. However, maintaining near-physiological volume ratios among blood surrogate and multiple organ mimics is technically challenging. Here, we developed a body cube and tested its ability to support four human tissues (kidney, GI tract, liver, and bone marrow) scaled down from in vivo functional volumes by a factor of 73,000 with 80 μL of cell culture medium (corresponding to ~1/73000th of in vivo blood volume).METHODS:GI tract cells (Caco-2), liver cells (HepG2/C3A), bone marrow cells (Meg-01), and kidney cells (HK-2) were co-cultured inside the body cube with 80 μL of common, recirculating cell culture medium for 72 h. The system was challenged with acetaminophen and troglitazone, and concentrations of aspartate aminotransferase (AST), albumin, and urea were monitored over time.RESULTS:Cell viability analysis showed that 95.5%±3.2% of liver cells, 89.8%±4.7% of bone marrow cells, 82.8%±8.1% of GI tract cells, and 80.1%±11.5% of kidney cells were viable in co-culture for 72 h. Both acetaminophen and troglitazone significantly lowered cell viability in the liver chamber as indicated by viability analysis and a temporary increase of AST in the cell culture medium. Both drugs also lowered urea production in the liver by up to 45%.CONCLUSIONS:Cell viability data and the production of urea and albumin indicate that the co-culture of GI tract, liver, bone marrow, and kidney tissues with near-physiological volume ratios of tissues to blood surrogate is possible for up to 72 h. The body-cube was capable of reproducing liver toxicity to HepG2/C3A liver cells via acetaminophen and troglitazone. The developed design provides a viable format for acute toxicity testing with near-physiological blood surrogate to tissue volume ratios.
Bone marrow is the permanent hematopoietic organ; the main function is to produce blood cells for the body through life. The microenvironment of bone marrow contains a complex set of cellular, chemical, and physical signals to maintain the hematopoietic system (1-3). The hematopoietic niche regulates hematopoietic stem cells (HSCs) to facilitate a balance between self-renewal and differentiation into progenitor cells that produce all types of blood cells.
The growing demand for improvements in in vitro drug screening, disease modelling, and regenerative tissue therapies poses an urgent clinical need for the continued development of innovative tissue engineering strategies. Several promising biofabrication and aggregation solutions have been developed to overcome these challenges, such as three-dimensional (3D) bioprinting and chip-based physiological models. However, replicating the structural and cytoarchitectural complexities of native tissue types to achieve biomimicry of epithelial, nervous, muscular, and connective tissues remains a significant area of investigation. Innovative research efforts focused on the thread-like morphologies of bodily tissues have been developed to overcome these challenges. This review features the recent and current work done in fiber fabrication methods and the associated textile assembly techniques utilized to create fiber-based microphysiological systems, specifically for applications in disease modelling and high throughput drug testing. The advantages and disadvantages of these different fiber fabrication and assembly approaches are compared. Finally, the applications of these textile-based biofabrication approaches in epithelial, nervous, connective, and muscle tissue engineering are reviewed.
Welcome to the collection of the current must-read open-access papers in the field of organs-on-chips that have become available in the second half of 2018. This quarterly editorial column will be compiled by Dr. Andries D. van der Meer, University of Twente, The Netherlands. Feel free to contact him with tips about open-access papers on organs-on-chips and microphysiological systems that you feel should be included in upcoming collections.
Organ-on-a-chip systems integrate microengineering, microfluidics, and biomimetic principles to create bionic systems for organ-level physiological simulation, disease research, and drug screening. Despite the limitations of cell sources, novel materials, and high-sensitivity detection equipment, various organ-on-a-chip systems have been developed for the evaluation of drug toxicity in vitro . They show an unparalleled capacity to bridge the gap between preclinical and clinical outcomes, as well as improve the predictability of drug toxicity. In this review, we introduce some recent advances in novel organ-on-a-chip systems that primarily target drug toxicity testing. Further, we discuss the current status of heart-, liver-, kidney-, brain-, and multi-organ-on-a-chip systems for drug assessment, as well as the challenges and future directions that need to be pursued.
As a paradigm shifting player of tissue engineering, organs-on-chips (OOCs) are considered to hold great potential for future “clinical trials on chip” as well as a step forward to design personalized medicine. Despite all ethical concerns raised by community and suspicious attitude of medical authorities, the field keeps evolving with a remarkable speed. Although the majority of efforts have been made on making OOCs more physiologically relevant via 3D cell culture techniques, incorporation of smart biomaterial matrices and microfluidic designs, considerable amount of studies have also been focused on these providing monitoring tools to these platforms. The aim of this review is to provide, for the first time, a comprehensive report on already available methods for monitoring OOCs. In that regard, this paper critically reviews physical, chemical and biochemical sensors that have been implemented for OOCs and cell culture monitoring by also discussing the advantages and disadvantages associated with each proposed method.
Theart of three-dimensional (3D) cell culture is to place cells in an environmentthat facilitates their differentiation into physiologically relevant tissues.The mammary gland was the original model for the development of 3D cellculture. With simple microphysiological systems for this model relying on thepresence of extracellular matrix (ECM) components, we initially showed thatnormal differentiation, illustrated by the formation of a basoapical polarityaxis and cell quiescence, relied on a specific organization of the cellnucleus, including the epigenome, itself under the control of the ECMmicroenvironment. To further explore microenvironment-nucleus interaction, werecently developed two organ-on-a-chip systems. The disease-on-a-chip was used tostudy mechanical influence by creating a model of ductal environment made ofcarved hemichannels. It revealed that the curvature of hemichannels directsnuclear morphometry to such an extent that tumors growing inside this geometry(as they do in vivo ) display distinct sensitivity to anticancer drugs.These findings shed light on previous observation that the expression ofproteins involved in anticancer drug response correlate with nuclearmorphometry and highlight the importance of choosing the appropriate 3D cellculture system for in vitro preclinical screening of drugs. Thegradient-on-a-chip was used to create, via microfluidics, a range ofextracellular concentrations of soluble components within the same culturechamber. With this system, it became apparent that oxidizing molecules presentin the ECM of cancers and suspected to contribute to progression and resistanceto treatment, have an influence on nuclear morphometric features recognized asa sign of aggressiveness; however, oxidizer concentration-mediated phenotypicswitch depends on ECM stiffness. These findings suggest that tissueheterogeneity characterizing cancers is directed by competitive and synergisticinfluences among extracellular factors controlling cell phenotype via an impacton the cell nucleus.
Microphysiological systems (MPS) as a promising alternative can recapitulate the structure and function of native tissues in vitro , accelerating drug development and toxicity screening. DNA mediated self- assembly may encourages cell to communicate with one another and differentiates cells self-assemble into the desired microphysiological structure. Extensive studies have been conducted to construct DNA-mediated self-assembled DNA-lipid hybrid systems by integrating DNA with lipid for achieving multicellular MPS. Realization of multicellular MPS also is allowed to study physicochemical and physiological features of membrane assemblies. In addition, these arti cial DNA-lipid hybrid systems show wide applications in drug delivery, synthetic biology, and chemical process control. Herein, we present a critical review on lipid-DNA hybrid systems. After briefly introducing biophysical and biochemical characteristics of membranes, we highlight representative approaches to interact DNA with membranes, including electrostatic interactions, membrane anchors, and membrane-bound proteins. Then, we discuss the properties of DNA-functionalized membrane and factors for membrane-anchored DNA, followed by overview on applications of lipid-DNA hybrid systems in recent years. Finally, considering the great potential presented by this system, we provide insight into the outlook and challenges for future developments.
Thousandsof new cases of myocardial infarctions (MI) emerge each year. The destructivenature of MI can cause irreparable damage to cardiac tissue so severe that 10%of survivors die within two years from their initial MI and only 50% ofsurvivors live beyond 10 years. Advances in human induced pluripotent stem cell(hiPSC) technology has offered unprecedented possibilities in cardiac tissueengineering for regenerative medicine. However, engineering physiologicallyfunctional adult cardiac tissue has been a challenge. Cardiomyocytes (CMs)organically rely on both mechanical and electrical stimulation to contractsimultaneously and grow effectively, meaning that the mechanisms used tostimulate stem cell-derived CMs in vitro is critical to CM development.Microsystems that more accurately mimic the complex in vivo environmentthrough electromechanical stimulation have been found to produce healthier CMs.This review analyzes the applications, benefits, and drawbacks to the mostpopular microphysiological systems (MPS) used for mechanical and electricalstimulation. Stimulation from these microsystems consistently produced CMs withhealthier and mature characteristics.
During the past two decades, microfluidics has become an enabling technology in many fields, including cell-biology, biophysics, biochemistry, optofluidics, etc. In the meantime, researchers are paying more attention to device materials because of the problems and unique functions they brought. As the most popular material in current microfluidic research, polydimethylsiloxane (PDMS) also has some drawbacks, such as absorption of small molecules and poor organic solvent compatibility. Thus, perfluorinated polymers (Teflons), which retain most advantages of PDMS but also has excellent inertness and anti-fouling properties, came into researchers’ perspective. After the initial period when liquid Teflon were directly coated on PDMS, whole-Teflon microfluidic chips were successfully fabricated and performed excellently in long-term cell culture, organic solvent-involved synthesis, etc. Since then, materials such as metals, biomolecules and other plastics have been integrated into Teflon chips and expanded their use to electrochemical sensing and immunoassay. Furthermore, perfluoropolymers have also been broadly used to assist mold release due to their nonstick property. Aiming to illustrate this progress, current review focuses on the recent development of Teflon microfabrication and applications in microfluidics, and provides critical discussion on this trend.
Microphysiological systems (MPS) offer great potential for improving pre-clinical testing for pharmaceutical treatments and novel therapies. These advanced in vitro models are designed to recapitulate the basic functions of living tissues or organs through dynamic culture and biomimetic microarchitecture. Increasing advancements in MPS design require advanced fabrication methods, such as extrusion bioprinting. Extrusion bioprinting presents the ability to automate fabrication of these systems in a simplified, one-step process, while providing the ability to fabricate complex, reproducible designs that incorporate dynamic culture, 3D microtissues and integrated sensors for analysis into a single system. This work reviews the main components that constitute these systems, current state-of-the-art MPS fabricated via extrusion bioprinting, and future considerations for the development of MPS.
Overwhelming scientific evidence today confirms that the gut microbiota is a central player in human health. Knowledge about interactions between human gut microbiota and human health has evolved rapidly in the last decade, based on experimental work involving analysis of human fecal samples or animal models (mainly rodents). A more detailed and cost-effective description of this interplay is now being enabled by the use of in vitro systems (i.e., gut-microbiota-on-chip systems) that recapitulate key aspects of the interaction between microbiota and human cells. Here, we review recent examples of the design and use of pioneering on-chip platforms for the study of the cross-talk between representative members of human microbiota and human microtissues. In these systems, the combined use of state-of-the-art microfluidics, biomaterials, cell culture techniques, classical microbiology, and a touch of genetic expression profiling have converged for the development of gut-on-chip platforms capable of recreating key features of the interplay between human microbiota and host human tissues. We foresee that the integration of novel microfabrication techniques and stem cell technologies will further accelerate the development of more complex and physiologically relevant microbiota-on-chip platforms. In turn, this will foster the faster acquisition of knowledge regarding human microbiota and will enable important advances in the understanding of how to control or prevent disease.
The field of microphysiological systems (or organs-on-a-chip) experienced, in the past decade, a surge in publications and efforts towards commercialization. Such systems hold the promise to advance drug discovery, diagnostics, and many other areas. In this review we summarize and analyze the current status of the field, describe the commercial advances and discuss standing challenges and the commercial outlook of the field.
Skin-on-a-chip models are highly desirable in drug testing compared to conventional 2D cell culture and animal models as they can replicate organ-specific 3D structural organization and physiological functions at a relatively low cost. To engineer a physiologically relevant skin model, human skin structures have been integrated onto microfluidic platforms to construct skin-on-a-chip systems that can mimic the complex in vivo situation. In this mini-review, we first briefly introduce some critical technologies employed to develop in vitro skin-on-a-chip models. We then review the applications of the state-of-the-art skin-on-a-chip models in drug testing, with a focus on using models of full-thickness skin equivalents (FTSEs), skin models with additional components such as vasculature, immune cells and hair follicles as well as multi-organ-on-a-chip models. Finally, we discuss some current challenges and future directions of development of complex, and in vivo-like skin-on-a-chip models.
Though in vivo models provide the most physiologically-relevant environment for studying tissue development and function, an in vitro substitute is being offered by the advancement of three-dimensional (3D) bioprinting technology, which is a reproducible and scalable fabrication strategy providing precise 3D control compared to conventional microfluidic tissue fabrication methods. In this review, vasculature models printed using extrusion-, droplet-, and laser-based bioprinting techniques are summarized and compared. Besides bioprinting of hydrogels as bioinks, an alternative method to obtain vascular models by bioprinting is to use exogenous biomaterial-free cell aggregates such as tissue spheroids and cell pellet, which has also been discussed here. In addition, there have been efforts to fabricate micro-vasculature constructs (e.g., capillaries) to overcome the practical limitations of bioprinting of large scale vascular networks. At the end of the review, limitations and prospective of bioprinting in vasculature modelling has also been expounded.
Microphysiological systems, often referred to as "organs-on-chips", are in vitro platforms designed to model the spatial, chemical, structural, and physiological elements of in vivo cellular environments. They enhance the evaluation of complex engineered biological systems and are a step between traditional cell culture and in vivo experimentation. As neurochemists and measurement scientists studying the molecules involved in intercellular communication in the nervous system, we focus here on recent advances in neuroscience using microneurological systems and their potential to interface with mass spectrometry. We discuss a number of examples - microfluidic devices, spheroid cultures, hydrogels, scaffolds, and fibers - highlighting those that would benefit from mass spectrometric technologies to obtain improved chemical information.
Respiratory diseases are amongst the leading causes of morbidity and mortality worldwide. There is therefore significant interest in developing more efficient treatment strategies for respiratory diseases particularly where there is irreversible tissue damage and loss of function. Despite recent advances in tissue engineering and stem cell technologies the reconstruction of large defects of upper airway and similar pathologies in respiratory system remains an unmet clinical need. The complex organisation of respiratory epithelium still has not been completely recapitulated in vitro . Therefore, novel strategies for the regeneration of functional ciliated respiratory epithelium are required to address the need for the treatment of life threatening respiratory diseases as well as developing biomimetic in vitro models that can be used in drug discovery and disease modelling. This review primarily focuses on current cell based approaches including available cell sources which have shown potential for developing biomimetic models/replacements of upper respiratory epithelium. Most of the tissue engineering approaches for the development of airway epithelium use epithelial basal cells, autologous or allogenic adult stem cells, induced pluripotent stem cells (iPSCs), embryonic stem cells (ESCs) or other stromal cells to induce the organised epithelial differentiation. However, the viability and function of injected/implanted cells could suffer from the host immune response and fail to perform the desired therapeutic functions. Also, given the key role of immune cells in the respiratory epithelium in maintaining defense against external insults, the importance of immune-competency of engineered respiratory epithelia is also discussed. To this end, modulation of immune system and application of biomaterials could play an important role in improving the therapeutic value of cell based respiratory epithelium regeneration. Overall, efforts for reconstruction of functional airway epithelium can be further improved by using optimal cell sources, biomaterials and modulation of immune response. The ability to engineer organised, functional respiratory epithelium can not only provide a remedy for several debilitating diseases but also provide a strong tool for in vitro drug assessment and disease modelling.
