Human organotypic bioconstructs from organ-on-chip devices for human-predictive biological insights on drug candidates

Developing Liver Microphysiological Systems for Biomedical Applications

Microphysiological systems (MPSs), also known as organ chips, are micro-units that integrate cells with diverse physical and biochemical environmental cues. In the field of liver MPSs, cellular components have advanced from simple planar cell cultures to more sophisticated 3D formations such as spheroids and organoids. Additionally, progress in microfluidic devices, bioprinting, engineering of matrix materials, and interdisciplinary technologies have significant promise for producing MPSs with biomimetic structures and functions. This review provides a comprehensive summary of biomimetic liver MPSs including their clinical applications and future developmental potential. First, the key components of liver MPSs, including the principal cell types and engineered structures utilized for cell cultivation, are briefly introduced. Subsequently, the biomedical applications of liver MPSs, including the creation of disease models, drug absorption, distribution, metabolism, excretion, and toxicity, are discussed. Finally, the challenges encountered by MPSs are summarized, and future research directions for their development are proposed.

Recent advances in sensor-integrated brain-on-a-chip devices for real-time brain monitoring

Brain science has remained in the global spotlight as an important field of scientific and technological discovery. Numerous in vitro and in vivo animal studies have been performed to understand the pathological processes involved in brain diseases and develop strategies for their diagnosis and treatment. However, owing to species differences between animals and humans, several drugs have shown high rates of treatment failure in clinical settings, hindering the development of diagnostic and treatment modalities for brain diseases. In this scenario, microfluidic brain-on-a-chip (BOC) devices, which allow the direct use of human tissues for experiments, have emerged as novel tools for effectively avoiding species differences and performing screening for new drugs. Although microfluidic BOC technology has achieved significant progress in recent years, monitoring slight changes in neurochemicals, neurotransmitters, and environmental states in the brain has remained challenging owing to the brain's complex environment. Hence, the integration of BOC with new sensors that have high sensitivity and high selectivity is urgently required for the real-time dynamic monitoring of BOC parameters. As sensor-based technologies for BOC have not been summarized, here, we review the principle, fabrication process, and application-based classification of sensor-integrated BOC, and then summarize the opportunities and challenges for their development. Generally, sensor-integrated BOC enables real-time monitoring and dynamic analysis, accurately measuring minute changes in the brain and thus enabling the realization of in vivo brain analysis and drug development.

Evaluating Translational Methods for Personalized Medicine—A Scoping Review

The introduction of personalized medicine, through the increasing multi-omics characterization of disease, brings new challenges to disease modeling. The scope of this review was a broad evaluation of the relevance, validity, and predictive value of the current preclinical methodologies applied in stratified medicine approaches. Two case models were chosen: oncology and brain disorders. We conducted a scoping review, following the Joanna Briggs Institute guidelines, and searched PubMed, EMBASE, and relevant databases for reports describing preclinical models applied in personalized medicine approaches. A total of 1292 and 1516 records were identified from the oncology and brain disorders search, respectively. Quantitative and qualitative synthesis was performed on a final total of 63 oncology and 94 brain disorder studies. The complexity of personalized approaches highlights the need for more sophisticated biological systems to assess the integrated mechanisms of response. Despite the progress in developing innovative and complex preclinical model systems, the currently available methods need to be further developed and validated before their potential in personalized medicine endeavors can be realized. More importantly, we identified underlying gaps in preclinical research relating to the relevance of experimental models, quality assessment practices, reporting, regulation, and a gap between preclinical and clinical research. To achieve a broad implementation of predictive translational models in personalized medicine, these fundamental deficits must be addressed.

Organ-on-a-chip: current gaps and future directions

As an emerging hot topic of the last decade, Organ on Chip (OoC) is a new technology that is attracting interest from both basic and translational scientists. The Biochemical Society, with its mission of supporting the advancement of science, with addressing grand challenges that have societal impact, has included OoC into their agenda to review the current state of the art, bottlenecks and future directions. This conference brought together representatives of the main stakeholders in the OoC field including academics, end-users, regulators and technology developers to discuss and identify requirements for this new technology to deliver on par with the expectations and the key challenges and gaps that still need to be addressed to achieve robust human-relevant tools, able to positively impact decision making in the pharmaceutical industry and reduce overreliance on poorly predictive animal models.

Organ-on-Chip platforms to study tumor evolution and chemosensitivity

Despite tremendous advancements in oncology research and therapeutics, cancer remains a primary cause of death worldwide. One of the significant factors in this critical challenge is a precise diagnosis and limited knowledge on how the tumor microenvironment (TME) behaves to the treatment and its role in chemo-resistance. Therefore, it is critical to understand the contribution of a heterogeneous TME in cancer drug response in individual patients for effective therapy management. Micro-physiological systems along with tissue engineering have facilitated the development of more physiologically relevant platforms, known as Organ-on-Chips (OoC). OoC platforms recapitulate the critical hallmarks of the TME in vitro and subsequently abet in sensitivity and efficacy testing of anti-cancer drugs before clinical trials. The OoC platforms incorporating conventional in vitro models enable researchers to control the cellular, molecular, chemical, and biophysical parameters of the TME in precise combinations while analyzing how they contribute to tumor progression and therapy response. This review discusses the application of OoC platforms integrated with conventional 2D cell lines, 3D organoids and spheroid models, and the organotypic tissue slices, including patient-derived and xenograft tumor slice cultures in cancer treatment responses. We summarize the relevance and drawbacks of conventional in vitro models in assessing cancer treatment response, challenges and limitations associated with OoC models, and future opportunities enabled by the OoC technologies towards developing personalized cancer diagnostics and therapeutics.

An Immersible Microgripper for Pancreatic Islet and Organoid Research

To improve the predictive value of in vitro experimentation, the use of 3D cell culture models, or organoids, is becoming increasingly popular. However, the current equipment of life science laboratories has been developed to deal with cell monolayers or cell suspensions. To handle 3D cell aggregates and organoids in a well-controlled manner, without causing structural damage or disturbing the function of interest, new instrumentation is needed. In particular, the precise and stable positioning in a cell bath with flow rates sufficient to characterize the kinetic responses to physiological or pharmacological stimuli can be a demanding task. Here, we present data that demonstrate that microgrippers are well suited to this task. The current version is able to work in aqueous solutions and was shown to position isolated pancreatic islets and 3D aggregates of insulin-secreting MIN6-cells. A stable hold required a gripping force of less than 30 μN and did not affect the cellular integrity. It was maintained even with high flow rates of the bath perfusion, and it was precise enough to permit the simultaneous microfluorimetric measurements and membrane potential measurements of the single cells within the islet through the use of patch-clamp electrodes.

The Future of 3D Brain Cultures in Developmental Neurotoxicity Testing

Human brain is undoubtedly the most complex organ in the body. Thus, it is difficult to develop adequate and at the same time human relevant test systems and models to cover the aspects of brain homeostasis and even more challenging to address brain development. Animal tests for Developmental Neurotoxicity (DNT) have been devised, but because of complex underlying mechanisms of neural development, and interspecies differences, there are many limitations of animal-based approaches. The high costs, high number of animals used per test and technical difficulties of these tests are prohibitive for routine DNT chemical screening. Therefore, many potential DNT chemicals remain unidentified. New approach methodologies (NAMs) are needed to change this. Experts in the field have recommended the use of a battery of human in vitro tests to be used for the initial prioritization of high-risk environmental chemicals for DNT testing. Microphysiological systems (MPS) of the brain mimic the in vivo counterpart in terms of cellular composition, recapitulation of regional architecture and functionality. These systems amendable to use in a DNT test battery with promising features such as (i) complexity, (ii) closer recapitulation of in vivo response and (iii) possibility to multiplex many assays in one test system, which can increase throughput and predictivity for human health. The resent progress in 3D brain MPS research, advantages, limitations and future perspectives are discussed in this review.

Ion-Depleting Action of Perm-Selective Membranes for Enhancing Electrical Communication and Gated Ion Channel Activity in Cell Cultures

Ion-depletion action of an ion-selective membrane produces a moat channel that electrically insulates a cell colony and elevates the cell medium potential uniformly to synchronously activate and deactivate the voltage-gated ion channels of all cells. The result is robust synchronization with strong intercellular electrical communication and the discovery of ion channel deactivation that is only possible when the cells are in communication. The study suggests that the collective response of a cell colony to external stimuli is distinct from that of a single cell. Cell proliferation must hence be guided with strong intercellular communication and proper exogenous stimuli.

Organ-on-chip applications in drug discovery: an end user perspective

Organ-on-chip (OoC) systems are in vitro microfluidic models that mimic the microstructures, functions and physiochemical environments of whole living organs more accurately than two-dimensional models. While still in their infancy, OoCs are expected to bring ground-breaking benefits to a myriad of applications, enabling more human-relevant candidate drug efficacy and toxicity studies, and providing greater insights into mechanisms of human disease. Here, we explore a selection of applications of OoC systems. The future directions and scope of implementing OoCs across the drug discovery process are also discussed.

Lab-on-a-Chip Platforms as Tools for Drug Screening in Neuropathologies Associated with Blood-Brain Barrier Alterations

Lab-on-a-chip (LOC) and organ-on-a-chip (OOC) devices are highly versatile platforms that enable miniaturization and advanced controlled laboratory functions (i.e., microfluidics, advanced optical or electrical recordings, high-throughput screening). The manufacturing advancements of LOCs/OOCs for biomedical applications and their current limitations are briefly discussed. Multiple studies have exploited the advantages of mimicking organs or tissues on a chip. Among these, we focused our attention on the brain-on-a-chip, blood-brain barrier (BBB)-on-a-chip, and neurovascular unit (NVU)-on-a-chip applications. Mainly, we review the latest developments of brain-on-a-chip, BBB-on-a-chip, and NVU-on-a-chip devices and their use as testing platforms for high-throughput pharmacological screening. In particular, we analyze the most important contributions of these studies in the field of neurodegenerative diseases and their relevance in translational personalized medicine.

Microfluidic System for In Vivo-Like Drug Permeation Studies with Dynamic Dilution Profiles

Automated biomimetic systems for the preclinical testing of drugs are of great interest. Here, an in vitro testing platform for in vivo adapted drug absorption studies is presented. It has been designed with a focus on easy handling and the usability of established cell cultivation techniques in standard well plate inserts. The platform consists of a microfluidic device, which accommodates a well plate insert with pre-cultivated cells, and provides a fluid flow with dynamic drug dilution profiles. A low-cost single-board computer with a touchscreen was used as a control unit. This provides a graphical user interface, controls the syringe pump flow rates, and records the transepithelial electrical resistance. It thereby enables automated parallel testing in multiple devices at the same time. To demonstrate functionality, an MDCK cell layer was used as a model for an epithelial barrier for drug permeation testing. This confirms the possibility of performing absorption studies on barrier tissues under conditions close to those in vivo. Therefore, a further reduction in animal experiments can be expected.

Dynamic placenta-on-a-chip model for fetal risk assessment of nanoparticles intended to treat pregnancy-associated diseases

Pregnant women often have to take medication either for pregnancy-related diseases or for previously existing medical conditions. Current maternal medications pose fetal risks due to off target accumulation in the fetus. Nanoparticles, engineered particles in the nanometer scale, have been used for targeted drug delivery to the site of action without off-target effects. This has opened new avenues for treatment of pregnancy-associated diseases while minimizing risks on the fetus. It is therefore instrumental to study the potential transfer of nanoparticles from the mother to the fetus. Due to limitations of in vivo and ex vivo models, an in vitro model mimicking the in vivo situation is essential. Placenta-on-a-chip provides a microphysiological recapitulation of the human placenta. Here, we reviewed the fetal risks associated with current therapeutic approaches during pregnancy, analyzed the advantages and limitations of current models used for nanoparticle assessment, and highlighted the current need for using dynamic placenta-on-a-chip models for assessing the safety of novel nanoparticle-based therapies during pregnancy.

An In Vitro Whole-Organ Liver Engineering for Testing of Genetic Therapies

Explosion of gene therapy approaches for treating rare monogenic and common liver disorders created an urgent need for disease models able to replicate human liver cellular environment. Available models lack 3D liver structure or are unable to survive in long-term culture. We aimed to generate and test a 3D culture system that allows long-term maintenance of human liver cell characteristics. The in vitro whole-organ "Bioreactor grown Artificial Liver Model" (BALM) employs a custom-designed bioreactor for long-term 3D culture of human induced pluripotent stem cells-derived hepatocyte-like cells (hiHEPs) in a mouse decellularized liver scaffold. Adeno-associated viral (AAV) and lentiviral (LV) vectors were introduced by intravascular injection. Substantial AAV and LV transgene expression in the BALM-grown hiHEPs was detected. Measurement of secreted proteins in the media allowed non-invasive monitoring of the system. We demonstrated that humanized whole-organ BALM is a valuable tool to generate pre-clinical data for investigational medicinal products.

Analysis of reproducibility and robustness of a human microfluidic four-cell liver acinus microphysiology system (LAMPS)

A human microfluidic four-cell liver acinus microphysiology system (LAMPS), was evaluated for reproducibility and robustness as a model for drug pharmacokinetics and toxicology. The model was constructed using primary human hepatocytes or human induced pluripotent stem cell (iPSC)-derived hepatocytes and 3 human cell lines for the endothelial, Kupffer and stellate cells. The model was tested in two laboratories and demonstrated to be reproducible in terms of basal function of hepatocytes, Terfenadine metabolism, and effects of Tolcapone (88 μM), Troglitazone (150 μM), and caffeine (600 μM) over 9 days in culture. Additional experiments compared basal outputs of albumin, urea, lactate dehydrogenase (LDH) and tumor necrosis factor (TNF)α, as well as drug metabolism and toxicity in the LAMPS model, and in 2D cultures seeded with either primary hepatocytes or iPSC-hepatocytes. Further experiments to study the effects of Terfenadine (10 μM), Tolcapone (88 μM), Trovafloxacin (150 μM with or without 1 μg/mL lipopolysaccharide), Troglitazone (28 μM), Rosiglitazone (0.8 μM), Pioglitazone (3 μM), and caffeine (600 μM) were carried out over 10 days. We found that both primary human hepatocytes and iPSC-derived hepatocytes in 3D culture maintained excellent basal liver function and Terfenadine metabolism over 10 days compared the same cells in 2D cultures. In 2D, non-overlay monolayer cultures, both cell types lost hepatocyte phenotypes after 48 h. With respect to drug effects, both cell types demonstrated comparable and more human-relevant effects in LAMPS, as compared to 2D cultures. Overall, these studies show that LAMPS is a robust and reproducible in vitro liver model, comparable in performance when seeded with either primary human hepatocytes or iPSC-derived hepatocytes, and more physiologically and clinically relevant than 2D monolayer cultures.

Recent progress in translational engineered in vitro models of the central nervous system

The complexity of the human brain poses a substantial challenge for the development of models of the CNS. Current animal models lack many essential human characteristics (in addition to raising operational challenges and ethical concerns), and conventional in vitro models, in turn, are limited in their capacity to provide information regarding many functional and systemic responses. Indeed, these challenges may underlie the notoriously low success rates of CNS drug development efforts. During the past 5 years, there has been a leap in the complexity and functionality of in vitro systems of the CNS, which have the potential to overcome many of the limitations of traditional model systems. The availability of human-derived induced pluripotent stem cell technology has further increased the translational potential of these systems. Yet, the adoption of state-of-the-art in vitro platforms within the CNS research community is limited. This may be attributable to the high costs or the immaturity of the systems. Nevertheless, the costs of fabrication have decreased, and there are tremendous ongoing efforts to improve the quality of cell differentiation. Herein, we aim to raise awareness of the capabilities and accessibility of advanced in vitro CNS technologies. We provide an overview of some of the main recent developments (since 2015) in in vitro CNS models. In particular, we focus on engineered in vitro models based on cell culture systems combined with microfluidic platforms (e.g. 'organ-on-a-chip' systems). We delve into the fundamental principles underlying these systems and review several applications of these platforms for the study of the CNS in health and disease. Our discussion further addresses the challenges that hinder the implementation of advanced in vitro platforms in personalized medicine or in large-scale industrial settings, and outlines the existing differentiation protocols and industrial cell sources. We conclude by providing practical guidelines for laboratories that are considering adopting organ-on-a-chip technologies.

Functional assays to assess the therapeutic potential of extracellular vesicles

An important aspect in the development of extracellular vesicle (EV) therapeutics is identifying and quantifying the key features defining their identity, purity, sterility, potency and stability to ensure batch-to-batch reproducibility of their therapeutic efficacy. Apart from EV-inherent features, therapeutic efficacy depends on a variety of additional parameters, like dosing, frequency of application, and administration route, some of which can be addressed only in clinical trials. Before initiating clinical trials, EV-inherent features should be tested in well-standardized quantitative assays in vitro or in appropriate animal models in vivo. Ideally, such assays would predict if a particular EV preparation has the potential to achieve its intended therapeutic effects, and could be further developed into formal potency assays as published by the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use guidelines. Furthermore, such assays should facilitate the comparison of EV preparations produced in different batches, on different manufacturing platforms or deriving from different cell sources. For now, a wide spectrum of in vitro and in vivo assays has been used to interrogate the therapeutic functions of EVs. However, many cannot accurately predict therapeutic potential. Indeed, several unique challenges make it difficult to set up reliable assays to assess the therapeutic potential of EVs, and to develop such assays into formal potency tests. Here, we discuss challenges and opportunities around in vitro and in vivo testing of EV therapeutic potential, including the need for harmonization, establishment of formal potency assays and novel developments for functional testing.

A public-private partnership for the express development of antiviral leads: a perspective view

INTRODUCTION

The COVID-19 pandemic raises the question of strategic readiness for emergent pathogens. The current case illustrates that the cost of inaction can be higher in the future. The perspective article proposes a dedicated, government-sponsored agency developing anti-viral leads against all potentially dangerous pathogen species.

AREAS COVERED

The author explores the methods of computational drug screening and in-silico synthesis and proposes a specialized government-sponsored agency focusing on leads and functioning in collaboration with a network of labs, pharma, biotech firms, and academia, in order to test each lead against multiple viral species. The agency will employ artificial intelligence and machine learning tools to cut the costs further. The algorithms are expected to receive continuous feedback from the network of partners conducting the tests.

EXPERT OPINION

The author proposes a bionic principle, emulating antibody response by producing a combinatorial diversity of high q uality generic antiviral leads, suitable for multiple potentially emerging species. The availability of multiple pre-tested agents and an even greater number of combinations would reduce the impact of the next outbreak. The methodologies developed in this effort are likely to find utility in the design of chronic disease therapeutics.

Recent Developments in Microfluidic Technologies for Central Nervous System Targeted Studies

Neurodegenerative diseases (NDs) bear a lot of weight in public health. By studying the properties of the blood-brain barrier (BBB) and its fundamental interactions with the central nervous system (CNS), it is possible to improve the understanding of the pathological mechanisms behind these disorders and create new and better strategies to improve bioavailability and therapeutic efficiency, such as nanocarriers. Microfluidics is an intersectional field with many applications. Microfluidic systems can be an invaluable tool to accurately simulate the BBB microenvironment, as well as develop, in a reproducible manner, drug delivery systems with well-defined physicochemical characteristics. This review provides an overview of the most recent advances on microfluidic devices for CNS-targeted studies. Firstly, the importance of the BBB will be addressed, and different experimental BBB models will be briefly discussed. Subsequently, microfluidic-integrated BBB models (BBB/brain-on-a-chip) are introduced and the state of the art reviewed, with special emphasis on their use to study NDs. Additionally, the microfluidic preparation of nanocarriers and other compounds for CNS delivery has been covered. The last section focuses on current challenges and future perspectives of microfluidic experimentation.

Predicting tubular reabsorption with a human kidney proximal tubule tissue-on-a-chip and physiologically-based modeling

Kidney is a major route of xenobiotic excretion, but the accuracy of preclinical data for predicting in vivo clearance is limited by species differences and non-physiologic 2D culture conditions. Microphysiological systems can potentially increase predictive accuracy due to their more realistic 3D environment and incorporation of dynamic flow. We used a renal proximal tubule microphysiological device to predict renal reabsorption of five compounds: creatinine (negative control), perfluorooctanoic acid (positive control), cisplatin, gentamicin, and cadmium. We perfused compound-containing media to determine renal uptake/reabsorption, adjusted for non-specific binding. A physiologically-based parallel tube model was used to model reabsorption kinetics and make predictions of overall in vivo renal clearance. For all compounds tested, the kidney tubule chip combined with physiologically-based modeling reproduces qualitatively and quantitatively in vivo tubular reabsorption and clearance. However, because the in vitro device lacks filtration and tubular secretion components, additional information on protein binding and the importance of secretory transport is needed in order to make accurate predictions. These and other limitations, such as the presence of non-physiological compounds such as antibiotics and bovine serum albumin in media and the need to better characterize degree of expression of important transporters, highlight some of the challenges with using microphysiological devices to predict in vivo pharmacokinetics.

The Challenge of Bringing iPSCs to the Patient

The implementation of induced pluripotent stem cells (iPSCs) in biomedical research more than a decade ago, resulted in a huge leap forward in the highly promising area of personalized medicine. Nowadays, we are even closer to the patient than ever. To date, there are multiple examples of iPSCs applications in clinical trials and drug screening. However, there are still many obstacles to overcome. In this review, we will focus our attention on the advantages of implementing induced pluripotent stem cells technology into the clinics but also commenting on all the current drawbacks that could hinder this promising path towards the patient.

18th Annual Meeting of the Safety Pharmacology Society: drug safety assessment on gastrointestinal system functions

Introduction: The 18^th Annual Meeting of the Safety Pharmacology Society included a session dedicated to the assessment of drug safety on the gastrointestinal (GI) system.Areas covered: GI anatomy, physiology, adverse effects (AEs) of chemical and biological therapies, and approaches to mitigate them.Expert opinion: GI AEs, albeit common and generally of minor intensity, may prolong clinical development time and reduce patient compliance.

18th world congress of basic and clinical pharmacology: thought-provoking lectures on drug safety issues

Introduction: Pharmacology of the Future for Science, Drug Development and Therapeutics was the leitmotif which guided the presentations at the 18th World Congress of Basic and Clinical Pharmacology held in Kyoto in July 2018 (WPC2018).Areas covered: Of the 380 invited lectures, this report reviews the opening presentation on immune checkpoint inhibitors and three talks dealing with drug safety issues (irreproducibility of nonclinical data, clinical Phase 1 catastrophes by TGN1214 and BIA-102,474-101 in healthy volunteers, and Phase I sentinel dosing to reduce risk to clinical study participants).Expert opinion: The nonclinical safety assessment of drug candidates preceding clinical investigations requires the adoption of more human predictable biological assays and a careful and critical analysis of all available knowledge on a candidate to ensure the safety of clinical trial participants.