Challenges in the Development and Application of Organ-on-Chips for Intranasal Drug Delivery Studies.

With the growing demand for the development of intranasal (IN) products, such as nasal vaccines, which has been especially highlighted during the COVID-19 pandemic, the lack of novel technologies to accurately test the safety and effectiveness of IN products in vitro so that they can be delivered promptly to the market is critically acknowledged. There have been attempts to manufacture anatomically relevant 3D replicas of the human nasal cavity for in vitro IN drug tests, and a couple of organ-on-chip (OoC) models, which mimic some key features of the nasal mucosa, have been proposed. However, these models are still in their infancy, and have not completely recapitulated the critical characteristics of the human nasal mucosa, including its biological interactions with other organs, to provide a reliable platform for preclinical IN drug tests. While the promising potential of OoCs for drug testing and development is being extensively investigated in recent research, the applicability of this technology for IN drug tests has barely been explored. This review aims to highlight the importance of using OoC models for in vitro IN drug tests and their potential applications in IN drug development by covering the background information on the wide usage of IN drugs and their common side effects where some classical examples of each area are pointed out. Specifically, this review focuses on the major challenges of developing advanced OoC technology and discusses the need to mimic the physiological and anatomical features of the nasal cavity and nasal mucosa, the performance of relevant drug safety assays, as well as the fabrication and operational aspects, with the ultimate goal to highlight the much-needed consensus, to converge the effort of the research community in this area of work.

Development of a Lymphoid Organ-Chip to Evaluate Covid Vaccine Boosting Strategies

Background: Secondary lymphoid organs provide the adequate microenvironment for the development of antigen (Ag)-specific immune responses. The tight collaboration between CD4+ T cells and B cells in germinal centers is crucial to shape B cell fate and optimize antibody maturation. Dissecting these immune interactions remains challenging in humans, and animal models do not always recapitulate human physiology. To address this issue, we developed an in vitro 3D model of a human lymphoid organ. The model relies on a microfluidic device, enabling primary human cells to self-organize in an extracellular matrix (ECM) under continuous fluid perfusion. We applied this Lymphoid Organ-Chip (LO chip) system to the analysis of B cell recall responses to SARS-CoV-2 antigens. Method(s): We used a two-channel microfluidic Chip S1 from Emulate, where the top channel is perfused with antigen (spike protein or SARS-CoV-2 mRNA vaccine), while the bottom channel contains PBMC (n = 14 independent donors) seeded at high-density in a collagen-based ECM. Immune cell division and cluster formation were monitored by confocal imaging, plasmablast differentiation and spike-specific B cell amplification by flow cytometry, antibody secretion by a cell-based binding assay (S-flow). Result(s): Chip perfusion with the SARS-CoV-2 spike protein for 6 days resulted in the induction CD38hiCD27hi plasmablast maturation compared to an irrelevant BSA protein (P< 0.0001). Using fluorescent spike as a probe, we observed a strong amplification of spike-specific B cell (from 3.7 to 140-fold increase). In line with this rapid memory B cell response, spike-specific antibodies production could be detected as early as day 6 of culture. Spike perfusion also induced CD4+ T cell activation (CD38+ ICOS+), which correlated with the level of B cell maturation. The magnitude of specific B cell amplification in the LO chip was higher than in 2D and 3D static cultures at day 6, showing the added value of 3D perfused culture for the induction of recall responses. Interestingly, the perfusion of mRNA-based SARS-CoV-2 vaccines also led to strong B cell maturation and specific B cell amplification, indicating that mRNA-derived spike could be expressed and efficiently presented in the LO chip. Conclusion(s): We developed a versatile Lymphoid Organ-Chip model suitable for the rapid evaluation of B cell recall responses. The model is responsive to protein and mRNA-encoded antigens, highlighting its potential in the evaluation of SARS-CoV-2 vaccine boosting strategies.

Microfluidic devices for the detection of disease-specific proteins and other macromolecules, disease modelling and drug development: A review.

Microfluidics is a revolutionary technology that has promising applications in the biomedical field.Integrating microfluidic technology with the traditional assays unravels the innumerable possibilities for translational biomedical research. Microfluidics has the potential to build up a novel platform for diagnosis and therapy through precise manipulation of fluids and enhanced throughput functions. The developments in microfluidics-based devices for diagnostics have evolved in the last decade and have been established for their rapid, effective, accurate and economic advantages. The efficiency and sensitivity of such devices to detect disease-specific macromolecules like proteins and nucleic acids have made crucial impacts in disease diagnosis. The disease modelling using microfluidic systems provides a more prominent replication of the in vivo microenvironment and can be a better alternative for the existing disease models. These models can replicate critical microphysiology like the dynamic microenvironment, cellular interactions, and biophysical and biochemical cues. Microfluidics also provides a promising system for high throughput drug screening and delivery applications. However, microfluidics-based diagnostics still encounter related challenges in the reliability, real-time monitoring and reproducibility that circumvents this technology from being impacted in the healthcare industry. This review highlights the recent microfluidics developments for modelling and diagnosing common diseases, including cancer, neurological, cardiovascular, respiratory and autoimmune disorders, and its applications in drug development.

Application of microfluidic technologies on COVID-19 diagnosis and drug discovery.

The ongoing coronavirus disease 2019 (COVID-19) pandemic has boosted the development of antiviral research. Microfluidic technologies offer powerful platforms for diagnosis and drug discovery for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnosis and drug discovery. In this review, we introduce the structure of SARS-CoV-2 and the basic knowledge of microfluidic design. We discuss the application of microfluidic devices in SARS-CoV-2 diagnosis based on detecting viral nucleic acid, antibodies, and antigens. We highlight the contribution of lab-on-a-chip to manufacturing point-of-care equipment of accurate, sensitive, low-cost, and user-friendly virus-detection devices. We then investigate the efforts in organ-on-a-chip and lipid nanoparticles (LNPs) synthesizing chips in antiviral drug screening and mRNA vaccine preparation. Microfluidic technologies contribute to the ongoing SARS-CoV-2 research efforts and provide tools for future viral outbreaks.

Microfluidic Organ-on-A-chip: A Guide to Biomaterial Choice and Fabrication.

Organ-on-A-chip (OoAC) devices are miniaturized, functional, in vitro constructs that aim to recapitulate the in vivo physiology of an organ using different cell types and extracellular matrix, while maintaining the chemical and mechanical properties of the surrounding microenvironments. From an end-point perspective, the success of a microfluidic OoAC relies mainly on the type of biomaterial and the fabrication strategy employed. Certain biomaterials, such as PDMS (polydimethylsiloxane), are preferred over others due to their ease of fabrication and proven success in modelling complex organ systems. However, the inherent nature of human microtissues to respond differently to surrounding stimulations has led to the combination of biomaterials ranging from simple PDMS chips to 3D-printed polymers coated with natural and synthetic materials, including hydrogels. In addition, recent advances in 3D printing and bioprinting techniques have led to the powerful combination of utilizing these materials to develop microfluidic OoAC devices. In this narrative review, we evaluate the different materials used to fabricate microfluidic OoAC devices while outlining their pros and cons in different organ systems. A note on combining the advances made in additive manufacturing (AM) techniques for the microfabrication of these complex systems is also discussed.

In vitro high-content tissue models to address precision medicine challenges.

The field of precision medicine allows for tailor-made treatments specific to a patient and thereby improve the efficiency and accuracy of disease prevention, diagnosis, and treatment and at the same time would reduce the cost, redundant treatment, and side effects of current treatments. Here, the combination of organ-on-a-chip and bioprinting into engineering high-content in vitro tissue models is envisioned to address some precision medicine challenges. This strategy could be employed to tackle the current coronavirus disease 2019 (COVID-19), which has made a significant impact and paradigm shift in our society. Nevertheless, despite that vaccines against COVID-19 have been successfully developed and vaccination programs are already being deployed worldwide, it will likely require some time before it is available to everyone. Furthermore, there are still some uncertainties and lack of a full understanding of the virus as demonstrated in the high number new mutations arising worldwide and reinfections of already vaccinated individuals. To this end, efficient diagnostic tools and treatments are still urgently needed. In this context, the convergence of bioprinting and organ-on-a-chip technologies, either used alone or in combination, could possibly function as a prominent tool in addressing the current pandemic. This could enable facile advances of important tools, diagnostics, and better physiologically representative in vitro models specific to individuals allowing for faster and more accurate screening of therapeutics evaluating their efficacy and toxicity. This review will cover such technological advances and highlight what is needed for the field to mature for tackling the various needs for current and future pandemics as well as their relevancy towards precision medicine.

Engineering organ-on-a-chip systems to model viral infections.

Infectious diseases remain a public healthcare concern worldwide. Amidst the pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, increasing resources have been diverted to investigate the therapeutics targeting COVID-19 Spike glycoprotein and to develop various classes of vaccines. Most of the current investigations employ two-dimensional (2D) cell culture and animal models. However, 2D culture negates the multicellular interactions and 3D microenvironment, and animal models cannot mimic human physiology because of interspecies differences. On the other hand, organ-on-a-chip (OoC) research devices introduce a game-changer to model viral infections in human tissues, facilitating high-throughput screening of antiviral therapeutics. In this context, this review provides an overview of the in vitro OoC-based modeling of viral infection, highlighting the strengths and challenges for the future directions.

Engineering viral genomics and nano-liposomes in microfluidic platforms for patient-specific analysis of SARS-CoV-2 variants.

New variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are continuing to spread globally, contributing to the persistence of the COVID-19 pandemic. Increasing resources have been focused on developing vaccines and therapeutics that target the Spike glycoprotein of SARS-CoV-2. Recent advances in microfluidics have the potential to recapitulate viral infection in the organ-specific platforms, known as organ-on-a-chip (OoC), in which binding of SARS-CoV-2 Spike protein to the angiotensin-converting enzyme 2 (ACE2) of the host cells occurs. As the COVID-19 pandemic lingers, there remains an unmet need to screen emerging mutations, to predict viral transmissibility and pathogenicity, and to assess the strength of neutralizing antibodies following vaccination or reinfection. Conventional detection of SARS-CoV-2 variants relies on two-dimensional (2-D) cell culture methods, whereas simulating the micro-environment requires three-dimensional (3-D) systems. To this end, analyzing SARS-CoV-2-mediated pathogenicity via microfluidic platforms minimizes the experimental cost, duration, and optimization needed for animal studies, and obviates the ethical concerns associated with the use of primates. In this context, this review highlights the state-of-the-art strategy to engineer the nano-liposomes that can be conjugated with SARS-CoV-2 Spike mutations or genomic sequences in the microfluidic platforms; thereby, allowing for screening the rising SARS-CoV-2 variants and predicting COVID-19-associated coagulation. Furthermore, introducing viral genomics to the patient-specific blood accelerates the discovery of therapeutic targets in the face of evolving viral variants, including B1.1.7 (Alpha), B.1.351 (Beta), B.1.617.2 (Delta), c.37 (Lambda), and B.1.1.529 (Omicron). Thus, engineering nano-liposomes to encapsulate SARS-CoV-2 viral genomic sequences enables rapid detection of SARS-CoV-2 variants in the long COVID-19 era.

Applications of microphysiological systems to disease models in the biopharmaceutical industry: Opportunities and challenges.

Disease models enable researchers to investigate, test, and identify therapeutic targets that would alter patients' disease condition and improve quality of life. Advancements in genetic alteration and analytical techniques have enabled rapid development of disease models using preclinical animals and cell cultures. However, success rates of drug development remain low due to limited recapitulation of clinical pathophysiology by these models. To resolve this challenge, the pharmaceutical industry has explored microphysiological system (MPS) disease models, which are complex in vitro systems that include but are not limited to organ-on-a-chip, organoids, spheroids, and 3D bioengineered tissues (e.g., 3D printing, hydrogels). Capable of integrating key in vivo properties, such as disease-relevant human cells, multi-cellularity/dimensionality of organs, and/or well-controlled physical and molecular cues, MPS disease models are being developed for a variety of indications. With on-going qualifications or validations for wide adoption within the pharmaceutical industry, MPS disease models hold exciting potential to enable in-depth investigation of in vivo pathophysiology and enhance drug discovery and development processes. To introduce the present status of MPS disease models, this paper describes notable examples in six disease areas: cancer, liver/kidney diseases, respiratory diseases/COVID-19, neurodegenerative diseases, gastrointestinal diseases, and select rare diseases. Additionally, we describe current technical limitations and provide recommendations for future development that would expand application opportunities within the pharmaceutical industry.

3D engineered tissue models for studying human-specific infectious viral diseases

Viral infections cause damage to various organ systems by inducing organ-specific symptoms or systemic multi-organ damage. Depending on the infection route and virus type, infectious diseases are classified as respiratory, nervous, immune, digestive, or skin infections. Since these infectious diseases can widely spread in the community and their catastrophic effects are severe, identification of their causative agent and mechanisms underlying their pathogenesis is an urgent necessity. Although infection-associated mechanisms have been studied in two-dimensional (2D) cell culture models and animal models, they have shown limitations in organ-specific or human-associated pathogenesis, and the development of a human-organ-mimetic system is required. Recently, three-dimensional (3D) engineered tissue models, which can present human organ-like physiology in terms of the 3D structure, utilization of human-originated cells, recapitulation of physiological stimuli, and tight cell-cell interactions, were developed. Furthermore, recent studies have shown that these models can recapitulate infection-associated pathologies. In this review, we summarized the recent advances in 3D engineered tissue models that mimic organ-specific viral infections. First, we briefly described the limitations of the current 2D and animal models in recapitulating human-specific viral infection pathology. Next, we provided an overview of recently reported viral infection models, focusing particularly on organ-specific infection pathologies. Finally, a future perspective that must be pursued to reconstitute more human-specific infectious diseases is presented. Copyright © 2022 The Authors

IND04-01 Modernizing drug discovery & development with organ-chip technology

There is no doubt that scientific progress has accelerated the discovery and development of innovative medicines, a phenomenon acutely visible through the rapid advancement of vaccines against SARS-CoV-2. Outside of dealing with a global pandemic, the process of drug discovery and development remains painfully slow, extremely costly and can, despite appropriate measures, result in patient-safety concerns. Because only around 12% of drugs that enter clinical trials make it to approval, governments in the United States and Europe are taking steps towards modernizing the process of drug discovery and development. Whilst several solutions will ultimately be required, there are growing calls for the utilization of 21st century tools within drug discovery pipelines. One such tool is organ-on-a-chip technology that employs microfluidic systems engineering to recapitulate in vivo cell and tissue microenvironments in an organ-specific context. This is achieved by recreating tissue-tissue interfaces and providing fine control over fluid flow and mechanical forces, optionally including supporting interactions with immune cells and microbiome, and reproducing clinical drug exposure profiles. This seminar will showcase the Emulate Organ-Chip platform and will present the findings of the first of its kind Organ-Chip study which utilized the pharma consortium Innovation and Quality (IQ) roadmap for developing in vitro liver models for the prediction of drug-induced liver injury1. Using 780 Liver-Chips across a test set of 27 small molecule drugs, data will be presented indicating that the Liver-Chip has a 87% sensitivity and 100% specificity, thus making it a highly predictive tool compared to animal models and prior preclinical in vitro models. The seminar will complete with an overview on how such a tool can be implemented into drug discovery workflows whilst providing adopting organizations a significant productivity gain.

3D Lung Tissue Models for Studies on SARS-CoV-2 Pathophysiology and Therapeutics.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing the coronavirus disease 2019 (COVID-19), has provoked more than six million deaths worldwide and continues to pose a major threat to global health. Enormous efforts have been made by researchers around the world to elucidate COVID-19 pathophysiology, design efficacious therapy and develop new vaccines to control the pandemic. To this end, experimental models are essential. While animal models and conventional cell cultures have been widely utilized during these research endeavors, they often do not adequately reflect the human responses to SARS-CoV-2 infection. Therefore, models that emulate with high fidelity the SARS-CoV-2 infection in human organs are needed for discovering new antiviral drugs and vaccines against COVID-19. Three-dimensional (3D) cell cultures, such as lung organoids and bioengineered organs-on-chips, are emerging as crucial tools for research on respiratory diseases. The lung airway, small airway and alveolus organ chips have been successfully used for studies on lung response to infection by various pathogens, including corona and influenza A viruses. In this review, we provide an overview of these new tools and their use in studies on COVID-19 pathogenesis and drug testing. We also discuss the limitations of the existing models and indicate some improvements for their use in research against COVID-19 as well as future emerging epidemics.

Self-assembling short immunostimulatory duplex RNAs with broad-spectrum antiviral activity.

The current coronavirus disease 2019 (COVID-19) pandemic highlights the need for broad-spectrum antiviral therapeutics. Here we describe a new class of self-assembling immunostimulatory short duplex RNAs that potently induce production of type I and type III interferon (IFN-I and IFN-III). These RNAs require a minimum of 20 base pairs, lack any sequence or structural characteristics of known immunostimulatory RNAs, and instead require a unique sequence motif (sense strand, 5'-C; antisense strand, 3'-GGG) that mediates end-to-end dimer self-assembly. The presence of terminal hydroxyl or monophosphate groups, blunt or overhanging ends, or terminal RNA or DNA bases did not affect their ability to induce IFN. Unlike previously described immunostimulatory small interfering RNAs (siRNAs), their activity is independent of Toll-like receptor (TLR) 7/8, but requires the RIG-I/IRF3 pathway that induces a more restricted antiviral response with a lower proinflammatory signature compared with immunostimulant poly(I:C). Immune stimulation mediated by these duplex RNAs results in broad-spectrum inhibition of infections by many respiratory viruses with pandemic potential, including severe acute respiratory syndrome coronavirus (SARS-CoV)-2, SARS-CoV, Middle East respiratory syndrome coronavirus (MERS-CoV), human coronavirus (HCoV)-NL63, and influenza A virus in cell lines, human lung chips that mimic organ-level lung pathophysiology, and a mouse SARS-CoV-2 infection model. These short double-stranded RNAs (dsRNAs) can be manufactured easily, and thus potentially could be harnessed to produce broad-spectrum antiviral therapeutics.

STUDYING CARDIAC SIDE EFFECTS OF SARS-COV-2 INFECTION AND SCREENING EXTRACELLULAR VESICLE THERAPEUTICS IN VITRO

Unlike seasonal coronaviruses, SARS-CoV-2 has a profound tropism for the heart. Estimates indicate 78% of individuals infected with SARS-CoV-2 experience cardiac side effects, with asymptomatic individuals still at risk of viral-induced heart failure, yet the mechanisms and consequences of such effects remain unclear. [1] Thus, therapeutics targeting SARS-CoV-2-induced heart failure remain elusive. The organ-on-a-chip industry has emerged at the intersection of microfluidics and tissue engineering, combining cells and biomaterials in arrangements that mimic organ processes, facilitating investigation of human physiology in a controlled and accessible environment. [2],[3] Recent studies indicate that cell signalling in the heart plays an integral role in tissue physiology and phenotype. [4],[5] For instance, it has been suggested that extracellular vesicles (EVs) released and taken up by cells in the heart are critical to regulating cardiac function and cellular responses to stress, disease, and injury. [6],[7] The “Biowire” model of cardiac tissueon-a-chip was used to study the cardiac side effects of coronavirus infection in the heart and to screen EV therapeutics for mitigating such effects. EVs sourced from induced pluripotent stem cells (iPSCs) facilitated the recovery of infected cardiac tissue function to baseline levels. miRNA sequencing and gene ontology analyses suggested several stress responsive pathways are targeted by iPSCEV miRNA that may alleviate some detrimental effects of coronavirus infection. Limited knowledge regarding SARS-CoV-2 side effects in the heart make tissue-on-a-chip models a novel tool to better understand the mechanisms of viral-induced heart failure and to study the potential for cell signalling-based therapeutics to improve patient outcomes.

Computational Simulations in Advanced Microfluidic Devices: A Review.

Numerical simulations have revolutionized research in several engineering areas by contributing to the understanding and improvement of several processes, being biomedical engineering one of them. Due to their potential, computational tools have gained visibility and have been increasingly used by several research groups as a supporting tool for the development of preclinical platforms as they allow studying, in a more detailed and faster way, phenomena that are difficult to study experimentally due to the complexity of biological processes present in these models-namely, heat transfer, shear stresses, diffusion processes, velocity fields, etc. There are several contributions already in the literature, and significant advances have been made in this field of research. This review provides the most recent progress in numerical studies on advanced microfluidic devices, such as organ-on-a-chip (OoC) devices, and how these studies can be helpful in enhancing our insight into the physical processes involved and in developing more effective OoC platforms. In general, it has been noticed that in some cases, the numerical studies performed have limitations that need to be improved, and in the majority of the studies, it is extremely difficult to replicate the data due to the lack of detail around the simulations carried out.

Application of lung microphysiological systems to COVID-19 modeling and drug discovery: a review.

There is a pressing need for effective therapeutics for coronavirus disease 2019 (COVID-19), the respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. The process of drug development is a costly and meticulously paced process, where progress is often hindered by the failure of initially promising leads. To aid this challenge, in vitro human microphysiological systems need to be refined and adapted for mechanistic studies and drug screening, thereby saving valuable time and resources during a pandemic crisis. The SARS-CoV-2 virus attacks the lung, an organ where the unique three-dimensional (3D) structure of its functional units is critical for proper respiratory function. The in vitro lung models essentially recapitulate the distinct tissue structure and the dynamic mechanical and biological interactions between different cell types. Current model systems include Transwell, organoid and organ-on-a-chip or microphysiological systems (MPSs). We review models that have direct relevance toward modeling the pathology of COVID-19, including the processes of inflammation, edema, coagulation, as well as lung immune function. We also consider the practical issues that may influence the design and fabrication of MPS. The role of lung MPS is addressed in the context of multi-organ models, and it is discussed how high-throughput screening and artificial intelligence can be integrated with lung MPS to accelerate drug development for COVID-19 and other infectious diseases.

Lung on a Chip Development from Off-Stoichiometry Thiol-Ene Polymer.

Current in vitro models have significant limitations for new respiratory disease research and rapid drug repurposing. Lung on a chip (LOAC) technology offers a potential solution to these problems. However, these devices typically are fabricated from polydimethylsiloxane (PDMS), which has small hydrophobic molecule absorption, which hinders the application of this technology in drug repurposing for respiratory diseases. Off-stoichiometry thiol-ene (OSTE) is a promising alternative material class to PDMS. Therefore, this study aimed to test OSTE as an alternative material for LOAC prototype development and compare it to PDMS. We tested OSTE material for light transmission, small molecule absorption, inhibition of enzymatic reactions, membrane particle, and fluorescent dye absorption. Next, we microfabricated LOAC devices from PDMS and OSTE, functionalized with human umbilical vein endothelial cell (HUVEC) and A549 cell lines, and analyzed them with immunofluorescence. We demonstrated that compared to PDMS, OSTE has similar absorption of membrane particles and effect on enzymatic reactions, significantly lower small molecule absorption, and lower light transmission. Consequently, the immunofluorescence of OSTE LOAC was significantly impaired by OSTE optical properties. In conclusion, OSTE is a promising material for LOAC, but optical issues should be addressed in future LOAC prototypes to benefit from the material properties.

Role of biomaterials in the diagnosis, prevention, treatment, and study of corona virus disease 2019 (COVID-19).

Recently emerged novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the resulting corona virus disease 2019 (COVID-19) led to urgent search for methods to prevent and treat COVID-19. Among important disciplines that were mobilized is the biomaterials science and engineering. Biomaterials offer a range of possibilities to develop disease models, protective, diagnostic, therapeutic, monitoring measures, and vaccines. Among the most important contributions made so far from this field are tissue engineering, organoids, and organ-on-a-chip systems, which have been the important frontiers in developing tissue models for viral infection studies. Also, due to low bioavailability and limited circulation time of conventional antiviral drugs, controlled and targeted drug delivery could be applied alternatively. Fortunately, at the time of writing this paper, we have two successful vaccines and new at-home detection platforms. In this paper, we aim to review recent advances of biomaterial-based platforms for protection, diagnosis, vaccination, therapeutics, and monitoring of SARS-CoV-2 and discuss challenges and possible future research directions in this field.

SARS-CoV-2 induced intestinal responses with a biomimetic human gut-on-chip.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global pandemic. Clinical evidence suggests that the intestine is another high-risk organ for SARS-CoV-2 infection besides the lungs. However, a model that can accurately reflect the response of the human intestine to the virus is still lacking. Here, we created an intestinal infection model on a chip that allows the recapitulation of human relevant intestinal pathophysiology induced by SARS-CoV-2 at organ level. This microengineered gut-on-chip reconstitutes the key features of the intestinal epithelium-vascular endothelium barrier through the three-dimensional (3D) co-culture of human intestinal epithelial, mucin-secreting, and vascular endothelial cells under physiological fluid flow. The intestinal epithelium showed permissiveness for viral infection and obvious morphological changes with injury of intestinal villi, dispersed distribution of mucus-secreting cells, and reduced expression of tight junction (E-cadherin), indicating the destruction of the intestinal barrier integrity caused by virus. Moreover, the vascular endothelium exhibited abnormal cell morphology, with disrupted adherent junctions. Transcriptional analysis revealed abnormal RNA and protein metabolism, as well as activated immune responses in both epithelial and endothelial cells after viral infection (e.g., upregulated cytokine genes), which may contribute to the injury of the intestinal barrier associated with gastrointestinal symptoms. This human organ system can partially mirror intestinal barrier injury and the human response to viral infection, which is not possible in existing in vitro culture models. It provides a unique and rapid platform to accelerate COVID-19 research and develop novel therapies.

Potential Applications of Microfluidics to Acute Kidney Injury Associated with Viral Infection.

The kidneys are susceptible to adverse effects from many diseases, including several that are not tissue-specific. Acute kidney injury is a common complication of systemic diseases such as diabetes, lupus, and certain infections including the novel coronavirus (SARS-CoV-2). Microfluidic devices are an attractive option for disease modeling, offering the opportunity to utilize human cells, control experimental and environmental conditions, and combine with other on-chip devices. For researchers with expertise in microfluidics, this brief perspective highlights potential applications of such devices to studying SARS-CoV-2-induced kidney injury.