Microphysiological Systems: Stakeholder Challenges to Adoption in Drug Development

Comparison of wild-type and high-risk PNPLA3 variants in a human biomimetic liver microphysiology system for metabolic dysfunction-associated steatotic liver disease precision therapy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a worldwide health epidemic with a global occurrence of approximately 30%. The pathogenesis of MASLD is a complex, multisystem disorder driven by multiple factors, including genetics, lifestyle, and the environment. Patient heterogeneity presents challenges in developing MASLD therapeutics, creating patient cohorts for clinical trials, and optimizing therapeutic strategies for specific patient cohorts. Implementing pre-clinical experimental models for drug development creates a significant challenge as simple in vitro systems and animal models do not fully recapitulate critical steps in the pathogenesis and the complexity of MASLD progression. To address this, we implemented a precision medicine strategy that couples the use of our liver acinus microphysiology system (LAMPS) constructed with patient-derived primary cells. We investigated the MASLD-associated genetic variant patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs738409 (I148M variant) in primary hepatocytes as it is associated with MASLD progression. We constructed the LAMPS with genotyped wild-type and variant PNPLA3 hepatocytes, together with key non-parenchymal cells, and quantified the reproducibility of the model. We altered media components to mimic blood chemistries, including insulin, glucose, free fatty acids, and immune-activating molecules to reflect normal fasting (NF), early metabolic syndrome (EMS), and late metabolic syndrome (LMS) conditions. Finally, we investigated the response to treatment with resmetirom, an approved drug for metabolic syndrome-associated steatohepatitis (MASH), the progressive form of MASLD. This study, using primary cells, serves as a benchmark for studies using "patient biomimetic twins" constructed with patient induced pluripotent stem cell (iPSC)-derived liver cells using a panel of reproducible metrics. We observed increased steatosis, immune activation, stellate cell activation, and secretion of pro-fibrotic markers in the PNPLA3 GG variant compared to the wild-type CC LAMPS, consistent with the clinical characterization of this variant. We also observed greater resmetirom efficacy in the PNPLA3 wild-type CC LAMPS compared to the GG variant in multiple MASLD metrics, including steatosis, stellate cell activation, and the secretion of pro-fibrotic markers. In conclusion, our study demonstrates the capability of the LAMPS platform for the development of MASLD precision therapeutics, enrichment of patient cohorts for clinical trials, and optimization of therapeutic strategies for patient subgroups with different clinical traits and disease stages.

Microphysiological Systems for Cancer Immunotherapy Research and Development

Cancer immunotherapy focuses on the use of patients' adaptive immune systems to combat cancer. In the past decade, FDA has approved many immunotherapy products for cancer patients who suffer from primary tumors, tumor relapse, and metastases. However, these immunotherapies still show resistance in many patients and often lead to inconsistent responses in patients due to variations in tumor genetic mutations and tumor immune microenvironment. Microfluidics-based organ-on-a-chip technologies or microphysiological systems have opened new ways that can provide relatively fast screening for personalized immunotherapy and help researchers and clinicians understand tumor-immune interactions in a patient-specific manner. They also have the potential to overcome the limitations of traditional drug screening and testing, given the models provide a more realistic 3D microenvironment with better controllability, reproducibility, and physiological relevance. This review focuses on the cutting-edge microphysiological organ-on-a-chip devices developed in recent years for studying cancer immunity and testing cancer immunotherapeutic agents, as well as some of the largest challenges of translating this technology to clinical applications in immunotherapy and personalized medicine.

What public health challenges and unmet medical needs would benefit from interdisciplinary collaboration in the EU? A survey and multi-stakeholder debate

In the past decade, significant European calls for research proposals have supported translational collaborative research on non-communicable and infectious diseases within the biomedical life sciences by bringing together interdisciplinary and multinational consortia. This research has advanced our understanding of disease pathophysiology, marking considerable scientific progress. Yet, it is crucial to retrospectively evaluate these efforts' societal impact. Research proposals should be thoughtfully designed to ensure that the research findings can be effectively translated into actionable policies. In addition, the choice of scientific methods plays a pivotal role in shaping the societal impact of research discoveries. Understanding the factors responsible for current unmet public health issues and medical needs is crucial for crafting innovative strategies for research policy interventions. A multistakeholder survey and a roundtable helped identify potential needs for consideration in the EU research and policy agenda. Based on survey findings, mental health disorders, metabolic syndrome, cancer, antimicrobial resistance, environmental pollution, and cardiovascular diseases were considered the public health challenges deserving prioritisation. In addition, early diagnosis, primary prevention, the impact of environmental pollution on disease onset and personalised medicine approaches were the most selected unmet medical needs. Survey findings enabled the formulation of some research-policies interventions (RPIs), which were further discussed during a multistakeholder online roundtable. The discussion underscored recent EU-level activities aligned with the survey-derived RPIs and facilitated an exchange of perspectives on public health and biomedical research topics ripe for interdisciplinary collaboration and warranting attention within the EU's research and policy agenda. Actionable recommendations aimed at facilitating the translation of knowledge into transformative, science-based policies are also provided.

Skin-on-a-chip technologies towards clinical translation and commercialization

Skin is the largest organ of the human body which plays a critical role in thermoregulation, metabolism (e.g. synthesis of vitamin D), and protection of other organs from environmental threats, such as infections, microorganisms, ultraviolet radiation, and physical damage. Even though skin diseases are considered to be less fatal, the ubiquity of skin diseases and irritation caused by them highlights the importance of skin studies. Furthermore, skin is a promising means for transdermal drug delivery, which requires a thorough understanding of human skin structure. Current animal andin vitrotwo/three-dimensional skin models provide a platform for disease studies and drug testing, whereas they face challenges in the complete recapitulation of the dynamic and complex structure of actual skin tissue. One of the most effective methods for testing pharmaceuticals and modeling skin diseases are skin-on-a-chip (SoC) platforms. SoC technologies provide a non-invasive approach for examining 3D skin layers and artificially creating disease models in order to develop diagnostic or therapeutic methods. In addition, SoC models enable dynamic perfusion of culture medium with nutrients and facilitate the continuous removal of cellular waste to further mimic thein vivocondition. Here, the article reviews the most recent advances in the design and applications of SoC platforms for disease modeling as well as the analysis of drugs and cosmetics. By examining the contributions of different patents to the physiological relevance of skin models, the review underscores the significant shift towards more ethical and efficient alternatives to animal testing. Furthermore, it explores the market dynamics ofin vitroskin models and organ-on-a-chip platforms, discussing the impact of legislative changes and market demand on the development and adoption of these advanced research tools. This article also identifies the existing obstacles that hinder the advancement of SoC platforms, proposing directions for future improvements, particularly focusing on the journey towards clinical adoption.

Bridging barriers: advances and challenges in modeling biological barriers and measuring barrier integrity in organ-on-chip systems

Biological barriers such as the blood-brain barrier, skin, and intestinal mucosal barrier play key roles in homeostasis, disease physiology, and drug delivery - as such, it is important to create representative in vitro models to improve understanding of barrier biology and serve as tools for therapeutic development. Microfluidic cell culture and organ-on-a-chip (OOC) systems enable barrier modelling with greater physiological fidelity than conventional platforms by mimicking key environmental aspects such as fluid shear, accurate microscale dimensions, mechanical cues, extracellular matrix, and geometrically defined co-culture. As the prevalence of barrier-on-chip models increases, so does the importance of tools that can accurately assess barrier integrity and function without disturbing the carefully engineered microenvironment. In this review, we first provide a background on biological barriers and the physiological features that are emulated through in vitro barrier models. Then, we outline molecular permeability and electrical sensing barrier integrity assessment methods, and the related challenges specific to barrier-on-chip implementation. Finally, we discuss future directions in the field, as well important priorities to consider such as fabrication costs, standardization, and bridging gaps between disciplines and stakeholders.

Roadblocks confronting widespread dissemination and deployment of Organs on Chips

Organ on Chip platforms hold significant promise as alternatives to animal models or traditional cell cultures, both of which poorly recapitulate human pathophysiology and human level responses. Within the last 15 years, we have witnessed seminal scientific developments from academic laboratories, a flurry of startups and investments, and a genuine interest from pharmaceutical industry as well as regulatory authorities to translate these platforms. This Perspective identifies several fundamental design and process features that may act as roadblocks that prevent widespread dissemination and deployment of these systems, and provides a roadmap to help position this technology in mainstream drug discovery.

Uniform sized cancer spheroids production using hydrogel-based droplet microfluidics: a review

Three-dimensional (3D) cell culture models have been extensively utilized in various mechanistic studies as well as for drug development studies as superior in vitro platforms than conventional two-dimensional (2D) cell culture models. This is especially the case in cancer biology, where 3D cancer models, such as spheroids or organoids, have been utilized extensively to understand the mechanisms of cancer development. Recently, many sophisticated 3D models such as organ-on-a-chip models are emerging as advanced in vitro models that can more accurately mimic the in vivo tissue functions. Despite such advancements, spheroids are still considered as a powerful 3D cancer model due to the relatively simple structure and compatibility with existing laboratory instruments, and also can provide orders of magnitude higher throughput than complex in vitro models, an extremely important aspects for drug development. However, creating well-defined spheroids remain challenging, both in terms of throughputs in generation as well as reproducibility in size and shape that can make it challenging for drug testing applications. In the past decades, droplet microfluidics utilizing hydrogels have been highlighted due to their potentials. Importantly, core-shell structured gel droplets can avoid spheroid-to-spheroid adhesion that can cause large variations in assays while also enabling long-term cultivation of spheroids with higher uniformity by protecting the core organoid area from external environment while the outer porous gel layer still allows nutrient exchange. Hence, core-shell gel droplet-based spheroid formation can improve the predictivity and reproducibility of drug screening assays. This review paper will focus on droplet microfluidics-based technologies for cancer spheroid production using various gel materials and structures. In addition, we will discuss emerging technologies that have the potential to advance the production of spheroids, prospects of such technologies, and remaining challenges.

Basic models to advanced systems: harnessing the power of organoids-based microphysiological models of the human brain

Understanding the complexities of the human brain's function in health and disease is a formidable challenge in neuroscience. While traditional models like animals offer valuable insights, they often fall short in accurately mirroring human biology and drug responses. Moreover, recent legislation has underscored the need for more predictive models that more accurately represent human physiology. To address this requirement, human-derived cell cultures have emerged as a crucial alternative for biomedical research. However, traditional static cell culture models lack the dynamic tissue microenvironment that governs human tissue function. Advancedin vitrosystems, such as organoids and microphysiological systems (MPSs), bridge this gap by offering more accurate representations of human biology. Organoids, which are three-dimensional miniaturized organ-like structures derived from stem cells, exhibit physiological responses akin to native tissues, but lack essential tissue-specific components such as functional vascular structures and immune cells. Recent endeavors have focused on incorporating endothelial cells and immune cells into organoids to enhance vascularization, maturation, and disease modeling. MPS, including organ-on-chip technologies, integrate diverse cell types and vascularization under dynamic culture conditions, revolutionizing brain research by bridging the gap betweenin vitroandin vivomodels. In this review, we delve into the evolution of MPS, with a particular focus on highlighting the significance of vascularization in enhancing the viability, functionality, and disease modeling potential of organoids. By examining the interplay of vasculature and neuronal cells within organoids, we can uncover novel therapeutic targets and gain valuable insights into disease mechanisms, offering the promise of significant advancements in neuroscience and improved patient outcomes.

Comparison of Wild-Type and High-risk PNPLA3 variants in a Human Biomimetic Liver Microphysiology System for Metabolic Dysfunction-associated Steatotic Liver Disease Precision Therapy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a worldwide health epidemic with a global occurrence of approximately 30%. The pathogenesis of MASLD is a complex, multisystem disorder driven by multiple factors including genetics, lifestyle, and the environment. Patient heterogeneity presents challenges for developing MASLD therapeutics, creation of patient cohorts for clinical trials and optimization of therapeutic strategies for specific patient cohorts. Implementing pre-clinical experimental models for drug development creates a significant challenge as simple in vitro systems and animal models do not fully recapitulate critical steps in the pathogenesis and the complexity of MASLD progression. To address this, we implemented a precision medicine strategy that couples the use of our liver acinus microphysiology system (LAMPS) constructed with patient-derived primary cells. We investigated the MASLD-associated genetic variant PNPLA3 rs738409 (I148M variant) in primary hepatocytes, as it is associated with MASLD progression. We constructed LAMPS with genotyped wild type and variant PNPLA3 hepatocytes together with key non-parenchymal cells and quantified the reproducibility of the model. We altered media components to mimic blood chemistries, including insulin, glucose, free fatty acids, and immune activating molecules to reflect normal fasting (NF), early metabolic syndrome (EMS) and late metabolic syndrome (LMS) conditions. Finally, we investigated the response to treatment with resmetirom, an approved drug for metabolic syndrome-associated steatohepatitis (MASH), the progressive form of MASLD. This study using primary cells serves as a benchmark for studies using patient biomimetic twins constructed with patient iPSC-derived liver cells using a panel of reproducible metrics. We observed increased steatosis, immune activation, stellate cell activation and secretion of pro-fibrotic markers in the PNPLA3 GG variant compared to wild type CC LAMPS, consistent with the clinical characterization of this variant. We also observed greater resmetirom efficacy in PNPLA3 wild type CC LAMPS compared to the GG variant in multiple MASLD metrics including steatosis, stellate cell activation and the secretion of pro-fibrotic markers. In conclusion, our study demonstrates the capability of the LAMPS platform for the development of MASLD precision therapeutics, enrichment of patient cohorts for clinical trials, and optimization of therapeutic strategies for patient subgroups with different clinical traits and disease stages.

From animal testing to in vitro systems: advancing standardization in microphysiological systems

Limitations with cell cultures and experimental animal-based studies have had the scientific and industrial communities searching for new approaches that can provide reliable human models for applications such as drug development, toxicological assessment, and in vitro pre-clinical evaluation. This has resulted in the development of microfluidic-based cultures that may better represent organs and organ systems in vivo than conventional monolayer cell cultures. Although there is considerable interest from industry and regulatory bodies in this technology, several challenges need to be addressed for it to reach its full potential. Among those is a lack of guidelines and standards. Therefore, a multidisciplinary team of stakeholders was formed, with members from the US Food and Drug Administration (FDA), the National Institute of Standards and Technology (NIST), European Union, academia, and industry, to provide a framework for future development of guidelines/standards governing engineering concepts of organ-on-a-chip models. The result of this work is presented here for interested parties, stakeholders, and other standards development organizations (SDOs) to foster further discussion and enhance the impact and benefits of these efforts.

The Current Status and Use of Microphysiological Systems by the Pharmaceutical Industry: The International Consortium for Innovation and Quality Microphysiological Systems Affiliate Survey and Commentary

Microphysiological systems (MPS) are comprised of one or multiple cell types of human or animal origins that mimic the biochemical/electrical/mechanical responses and blood-tissue barrier properties of the cells observed within a complex organ. The goal of incorporating these in vitro systems is to expedite and advance the drug discovery and development paradigm with improved predictive and translational capabilities. Considering the industry need for improved efficiency and the broad challenges of model qualification and acceptance, the International Consortium for Innovation and Quality (IQ) founded an IQ MPS working group in 2014 and Affiliate in 2018. This group connects thought leaders and end users, provides a forum for crosspharma collaboration, and engages with regulators to qualify translationally relevant MPS models. To understand how pharmaceutical companies are using MPS, the IQ MPS Affiliate conducted two surveys in 2019, survey 1, and 2021, survey 2, which differed slightly in the scope of definition of the complex in vitro models under question. The surveys captured demographics, resourcing, rank order for organs of interest, compound modalities tested, and MPS organ-specific questions, including nonclinical species needs and cell types. The major focus of this manuscript is on results from survey 2, where we specifically highlight the context of use for MPS within safety, pharmacology, or absorption, disposition, metabolism, and excretion and discuss considerations for including MPS data in regulatory submissions. In summary, these data provide valuable insights for developers, regulators, and pharma, offering a view into current industry practices and future considerations while highlighting key challenges impacting MPS adoption. SIGNIFICANCE STATEMENT: The application of microphysiological systems (MPS) represents a growing area of interest in the drug discovery and development framework. This study surveyed 20+ pharma companies to understand resourcing, current areas of application, and the key challenges and barriers to internal MPS adoption. These results will provide regulators, tech providers, and pharma industry leaders a starting point to assess the current state of MPS applications along with key learnings to effectively realize the potential of MPS as an emerging technology.

A (not) new Rx: Quality Improvement for NAM

New Approach Methodologies (NAMs) are a rapidly growing set of tools/methods for use food, drug, consumer product, or chemical safety assessment paradigms. The massive growth in NAMs tech development, publication, and legislation has been paralleled by a growing sense of frustration. The challenge of realizing the systems-level changes needed to catalyze the broad-scale adoption and use of NAMs is substantial. This Commentary asserts that these challenges may be less unique than perceived to date, and points to specific opportunities to learn from decades of experience (both positive and negative) from the Quality Improvement (QI) movement in the public health and healthcare arenas. Specific recommendations to inform and guide NAMs development are offered.

Review on new approach methods to gain insight into the feto-maternal interface physiology

Non-human animals represent a large and important feature in the history of biomedical research. The validity of their use, in terms of reproducible outcomes and translational confidence to the human situation, as well as ethical concerns surrounding that use, have been and remain controversial topics. Over the last 10 years, the communities developing microphysiological systems (MPS) have produced new approach method (NAMs) such as organoids and organs-on-a-chip. These alternative methodologies have shown indications of greater reliability and translatability than animal use in some areas, represent more humane substitutions for animals in these settings, and - with continued scientific effort - may change the conduct of basic research, clinical studies, safety testing, and drug development. Here, we present an introduction to these more human-relevant methodologies and suggest how a suite of pregnancy associated feto-maternal interface system-oriented NAMs may be integrated as reliable partial-/full animal replacements for investigators, significantly aid animal-/environmental welfare, and improve healthcare outcomes.

Pumped and pumpless microphysiological systems to study (nano)therapeutics

Fluidic microphysiological systems (MPS) are microfluidic cell culture devices that are designed to mimic the biochemical and biophysical in vivo microenvironments of human tissues better than conventional petri dishes or well-plates. MPS-grown tissue cultures can be used for probing new drugs for their potential primary and secondary toxicities as well as their efficacy. The systems can also be used for assessing the effects of environmental nanoparticles and nanotheranostics, including their rate of uptake, biodistribution, elimination, and toxicity. Pumpless MPS are a group of MPS that often utilize gravity to recirculate cell culture medium through their microfluidic networks, providing some advantages, but also presenting some challenges. They can be operated with near-physiological amounts of blood surrogate (i.e., cell culture medium) that can recirculate in bidirectional or unidirectional flow patterns depending on the device configuration. Here we discuss recent advances in the design and use of both pumped and pumpless MPS with a focus on where pumpless devices can contribute to realizing the potential future role of MPS in evaluating nanomaterials. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

A Next-Generation 3D Tissue-Engineered Model of the Human Brain Microvasculature to Study the Blood-Brain Barrier

More than a billion people are affected by neurological disorders, and few have effective therapeutic options. A key challenge that has prevented promising preclinically proven strategies is the translation gap to the clinic. Humanized tissue engineering models that recreate the brain environment may aid in bridging this translational gap. Here, we showcase the methodology that allows for the practical fabrication of a comprehensive microphysicological system (MPS) of the blood-brain barrier (BBB). Compared to other existing 2D and 3D models of the BBB, this model features relevant cytoarchitecture and multicellular arrangement, with branching and network topologies of the vascular bed. This process utilizes 3D bioprinting with digital light processing to generate a vasculature lumen network surrounded by embedded human astrocytes. The lumens are then cellularized with primary human brain microvascular endothelial cells and pericytes. To initiate mechanotransduction pathways and complete maturation, vascular structures are continuously perfused for 7 days. Constructs are validated for complete endothelialization with viability dyes prior to functional assessments that include barrier integrity (permeability) and immune-endothelial interactions. This MPS has applications for the study of novel therapeutics, toxins, and elucidating mechanisms of pathophysiology.

The evolving role of investigative toxicology in the pharmaceutical industry

For decades, preclinical toxicology was essentially a descriptive discipline in which treatment-related effects were carefully reported and used as a basis to calculate safety margins for drug candidates. In recent years, however, technological advances have increasingly enabled researchers to gain insights into toxicity mechanisms, supporting greater understanding of species relevance and translatability to humans, prediction of safety events, mitigation of side effects and development of safety biomarkers. Consequently, investigative (or mechanistic) toxicology has been gaining momentum and is now a key capability in the pharmaceutical industry. Here, we provide an overview of the current status of the field using case studies and discuss the potential impact of ongoing technological developments, based on a survey of investigative toxicologists from 14 European-based medium-sized to large pharmaceutical companies.

Organs-on-chips: a decade of innovation

Recreating 'living organs' with groundbreaking organ-on-a-chip (OOC) technologies is facilitating a new era of drug discovery. Studies by Huh et al. and Ronaldson-Bouchard et al. underscore advances made over a decade, spanning single organ functionality to interconnected organs, that enable examination of drug toxicities and disease pathogenesis in reconstituted tissues.

Alternative Methods as Tools for Obesity Research: In Vitro and In Silico Approaches

The study of adipogenesis is essential for understanding and treating obesity, a multifactorial problem related to body fat accumulation that leads to several life-threatening diseases, becoming one of the most critical public health problems worldwide. In this review, we propose to provide the highlights of the adipogenesis study based on in vitro differentiation of human mesenchymal stem cells (hMSCs). We list in silico methods, such as molecular docking for identification of molecular targets, and in vitro approaches, from 2D, more straightforward and applied for screening large libraries of substances, to more representative physiological models, such as 3D and bioprinting models. We also describe the development of physiological models based on microfluidic systems applied to investigate adipogenesis in vitro. We intend to identify the main alternative models for adipogenesis evaluation, contributing to the direction of preclinical research in obesity. Future directions indicate the association of in silico and in vitro techniques to bring a clear picture of alternative methods based on adipogenesis as a tool for obesity research.

Human organs-on-chips for disease modelling, drug development and personalized medicine

The failure of animal models to predict therapeutic responses in humans is a major problem that also brings into question their use for basic research. Organ-on-a-chip (organ chip) microfluidic devices lined with living cells cultured under fluid flow can recapitulate organ-level physiology and pathophysiology with high fidelity. Here, I review how single and multiple human organ chip systems have been used to model complex diseases and rare genetic disorders, to study host-microbiome interactions, to recapitulate whole-body inter-organ physiology and to reproduce human clinical responses to drugs, radiation, toxins and infectious pathogens. I also address the challenges that must be overcome for organ chips to be accepted by the pharmaceutical industry and regulatory agencies, as well as discuss recent advances in the field. It is evident that the use of human organ chips instead of animal models for drug development and as living avatars for personalized medicine is ever closer to realization.

Microphysiological Systems Evaluation: Experience of TEX-VAL Tissue Chip Testing Consortium

Much has been written and said about the promise and excitement of microphysiological systems, miniature devices that aim to recreate aspects of human physiology on a chip. The rapid explosion of the offerings and persistent publicity placed high expectations on both product manufacturers and regulatory agencies to adopt the data. Inevitably, discussions of where this technology fits in chemical testing paradigms are ongoing. Some end-users became early adopters, whereas others have taken a more cautious approach because of the high cost and uncertainties of their utility. Here, we detail the experience of a public-private collaboration established for testing of diverse microphysiological systems. Collectively, we present a number of considerations on practical aspects of using microphysiological systems in the context of their applications in decision-making. Specifically, future end-users need to be prepared for extensive on-site optimization and have access to a wide range of imaging and other equipment. We reason that cells, related reagents, and the technical skills of the research staff, not the devices themselves, are the most critical determinants of success. Extrapolation from concentration-response effects in microphysiological systems to human blood or oral exposures, difficulties with replicating the whole organ, and long-term functionality remain as critical challenges. Overall, we conclude that it is unlikely that a rodent- or human-equivalent model is achievable through a finite number of microphysiological systems in the near future; therefore, building consensus and promoting the gradual incorporation of these models into tiered approaches for safety assessment and decision-making is the sensible path to wide adoption.

Kidney microphysiological models for nephrotoxicity assessment

Nephrotoxicity testing is an important step in preclinical development of new molecular entities (NMEs) and has traditionally been performed in 2-D cell culture systems and animal models. However, 2-D culture systems fail to replicate complex in vivo microenvironment and animal models face interspecies differences including the overexpression of drug transporters. In the last decade, 3-D microphysiological systems (MPS) have been developed to address these concerns. Here, we review recent advancements in kidney MPS and their application in drug-induced toxicity testing and kidney disease research. We find that current research is making significant progress addressing MPS limitations such as throughput, incorporating various regions of the nephron such as the glomerulus, and successfully modeling and predicting clinically relevant nephrotoxicity of current and new drugs.

3D printed scaffolds: Challenges toward developing relevant cellular in vitro models

Three-dimensional (3D) cell culture technology has rapidly emerged, as a result of the increasing demand for improved in vitro systems that better resemble human physiology. Promising microphysiological systems have been fabricated by combining complex 3D culture with 3D-printing technologies. These models overperform existing in vitro systems regarding potential for biofabrication and predictive power. However, most systems under development do not ultimately find a long-term application. We provide herein an overview of the challenges to be considered when developing 3D in vitro systems by means of printed scaffolds, as well as some of the limitations of existing models.