Modeling the Human Body on Microfluidic Chips

Breaking barriers in obesity research: 3D models of dysfunctional adipose tissue

Obesity is a global health crisis characterised by excessive accumulation of adipose tissue (AT). Under obesogenic conditions, this metabolically active tissue undergoes fibrosis and inflammation, leading to obesity-linked comorbidities. Modelling AT is essential for understanding its pathophysiology and developing treatments to protect against metabolic complications. 3D in vitro AT models are promising tools that address the limitations of traditional 2D in vitro models and in vivo animal models, providing enhanced biomimetic and human-relevant platforms. 3D models facilitate the study of AT pathophysiology and therapeutic screening. This review discusses the crucial role of AT in obesity-linked comorbidities, its dynamicity and complexity, and recent advances in engineering 3D scaffold-based in vitro dysfunctional AT models, highlighting potential breakthroughs in metabolic research and beyond.

An immune-liver microphysiological system method for evaluation and quality control of hepatotoxicity induced by Polygonum multiflorum thunb. Extract

ETHNOPHARMACOLOGICAL RELEVANCE

Clinical applications of Polygonum multiflorum Thunb. (PMT) have occasionally reported adverse effects on liver function, linking these instances of hepatotoxicity to PMT samples. Evaluating the hepatotoxicity of PMT, given its intricate composition and mechanisms, presents a notable challenge. Notably, three toxic components display additive/synergistic effects, further complicating the establishment of a toxicological quality control method.

AIM OF THE STUDY

This study aims to develop a biology-based quality control method that can reflect the multi-mechanistic hepatotoxicity of PMT.

MATERIALS AND METHODS

We designed a microphysiological system tailored for the immune-liver interplay, termed the i-LOC, featuring three-cell channels. This i-LOC integrates hepatic cells with two distinct immune cell types to mimic inflammatory cell infiltration. As a control, a liver-on-chip devoid of immune cells was utilized to characterize hepatotoxicity induced by inflammatory stress.

RESULTS

The i-LOC system exhibited remarkable sensitivity in detecting both direct and inflammation-mediated hepatotoxic effects of the three PMT toxic components. This system significantly reduced the sample size requirements by thousandfold compared to animal models, presenting a cost-effective and attractive alternative for PMT toxicological assessments. Intriguingly, the system identified the present of previously unknown PMT compounds with potential hepatotoxic properties, emphasizing the need for a comprehensive biological evaluation method.

CONCLUSION

This study successfully developed an i-LOC method for effectively evaluating PMT's hepatotoxicity, overcoming the complexities posed by its intricate composition and mechanisms.

Cardiac-Focused Multi-Organ Chips: Advanced Disease Modeling, Drug Testing, and Inter-Organ Communication

Heart disease remains a leading cause of mortality worldwide, posing a significant challenge to global healthcare systems. Traditional animal models and cell culture techniques are instrumental in advancing the understanding of cardiac pathophysiology. However, these methods are limited in their ability to fully replicate the heart's intricate functions. This underscores the need for a deeper investigation into the fundamental mechanisms of heart disease. Notably, cardiac pathology is often influenced by systemic factors, with conditions in other organs contributing to disease onset and progression. Cardiac-focused multi-organ chip technology has emerged to better elucidate these complex inter-organ communications and address the limitations of current in vitro models. This technology offers a novel approach by recreating the cardiac microenvironment and integrating it with other organ systems, thereby enabling more precise disease modeling and drug toxicity assessment. This review provides a comprehensive overview of the heart's structure and function, explores the advancements in cardiac organ chip development, and highlights the applications of cardiac-focused multi-organ chips in medical research. Finally, the future potential of this technology in enhancing disease modeling and therapeutic evaluation is discussed.

Organoid models: applications and research advances in colorectal cancer

This review summarizes the applications and research progress of organoid models in colorectal cancer research. First, the high incidence and mortality rates of colorectal cancer are introduced, emphasizing the importance of organoids as a research model. Second, this review provides a detailed introduction to the concept, biological properties, and applications of organoids, including their strengths in mimicking the structural and functional aspects of organs. This article further analyzes the applications of adult stem cell-derived and pluripotent stem cell-derived organoids in colorectal cancer research and discusses advancements in organoids for basic research, drug research and development, personalized treatment evaluation and prediction, and regenerative medicine. Finally, this review summarizes the prospects for applying organoid technology in colorectal cancer research, emphasizing its significant value in improving patient survival rates. In conclusion, this review systematically explains the applications of organoids in colorectal cancer research, highlighting their tremendous potential and promising prospects in basic research, drug research and development, personalized treatment evaluation and prediction, and regenerative medicine.

Engineering organoids-on-chips for drug testing and evaluation

Organoids-on-chips is an emerging innovative integration of stem cell-derived organoids with advanced organ-on-chip technology, providing a novel platform for the in vitro construction of biomimetic micro-physiological systems. The synergistic merger transcends the limitations of traditional drug screening and safety assessment methodologies, such as 2D cell cultures and animal models. In this review, we examine the prevailing challenges and prerequisites of preclinical models utilized for drug screening and safety evaluations. We highlighted the salient features and merits of organoids-on-chip, elucidating their capability to authentically replicate human physiology, thereby addressing contemporary impediments. We comprehensively overviewed the recent endeavors where organoids-on-chips have been harnessed for drug screening and safety assessment and delved into potential opportunities and challenges for evolving sophisticated, near-physiological organoids-on-chips. Based on current achievements, we further discuss how to enhance the practicality of organoids-on-chips and accelerate the translation from preclinical to clinical stages in healthcare and industry by utilizing multidisciplinary convergent innovation.

Recapitulating the Cancer-Immunity Cycle on a Chip

The cancer-immunity cycle is a fundamental framework for understanding how the immune system interacts with cancer cells, balancing T cell recognition and elimination of tumors while avoiding autoimmune reactions. Despite advancements in immunotherapy, there remains a critical need to dissect each phase of the cycle, particularly the interactions among the tumor, vasculature, and immune system within the tumor microenvironment (TME). Innovative platforms such as organ-on-a-chip, organoids, and bioprinting within microphysiological systems (MPS) are increasingly utilized to enhance the understanding of these interactions. These systems meticulously replicate crucial aspects of the TME and immune responses, providing robust platforms to study cancer progression, immune evasion, and therapeutic interventions with greater physiological relevance. This review explores the latest advancements in MPS technologies for modeling various stages of the cancer-immune cycle, critically evaluating their applications and limitations in advancing the understanding of cancer-immune dynamics and guiding the development of next-generation immunotherapeutic strategies.

Progress in the Application of Organoids-On-A-Chip in Diseases

With the rapid development of the field of life sciences, traditional 2D cell culture and animal models have long been unable to meet the urgent needs of modern biomedical research and new drug development. Establishing a new generation of experimental models and research models is of great significance for deeply understanding human health and disease processes, and developing effective treatment measures. As is well known, long research and development cycles, high risks, and high costs are the "three mountains" facing the development of new drugs today. Organoids and organ-on-chips technology can highly simulate and reproduce the human physiological environment and complex reactions in vitro, greatly improving the accuracy of drug clinical efficacy prediction, reducing drug development costs, and avoiding the defects of drug testing animal models. Therefore, organ-on-chips have enormous potential in medical diagnosis and treatment.

Trends and challenges in organoid modeling and expansion with pluripotent stem cells and somatic tissue

The increasing demand for disease modeling, preclinical drug testing, and long waiting lists for alternative organ substitutes has posed significant challenges to current limitations in organoid technology. Consequently, organoid technology has emerged as a cutting-edge tool capable of accurately recapitulating the complexity of actual organs in physiology and functionality. To bridge the gaps between basic research and pharmaceutical as well as clinical applications, efforts have been made to develop organoids from tissue-derived stem cells or pluripotent stem cells. These developments include optimizing starting cells, refining culture systems, and introducing genetic modifications. With the rapid development of organoid technology, organoid composition has evolved from single-cell to multi-cell types, enhancing their level of biomimicry. Tissue structure has become more refined, and core challenges like vascularization are being addressed actively. These improvements are expected to pave the way for the construction of organoid atlases, automated large-scale cultivation, and universally compatible organoid biobanks. However, major obstacles remain to be overcome before urgently proof-of-concept organoids can be readily converted to practical applications. These obstacles include achieving structural and functional summarily to native tissue, remodeling the microenvironment, and scaling up production. This review aims to summarize the status of organoid development and applications, highlight recent progress, acknowledge existing limitations and challenges, and provide insights into future advancements. It is expected that this will contribute to the establishment of a reliable, scalable, and practical platform for organoid production and translation, further promoting their use in the pharmaceutical industry and regenerative medicine.

An Easy-to-Use Arrayed Brain-Heart Chip

Multi-organ chips are effective at emulating human tissue and organ functions and at replicating the interactions among tissues and organs. An arrayed brain-heart chip was introduced whose configuration comprises open culture chambers and closed biomimetic vascular channels distributed in a horizontal pattern, separated from each other by an endothelial barrier based on fibrin matrix. A 300 μm-high and 13.2 mm-long endothelial barrier surrounded each organoid culture chamber, thereby satisfying the material transport requirements. Numerical simulations were used to analyze the construction process of fibrin barriers in order to optimize the structural design and experimental manipulation, which exhibited a high degree of correlation with experiment results. In each interconnective unit, a cerebral organoid, a cardiac organoid, and endothelial cells were co-cultured stably for a minimum of one week. The permeability of the endothelial barrier and recirculating perfusion enabled cross talk between cerebral organoids and cardiac organoids, as well as between organoids and endothelial cells. This was corroborated by the presence of cardiac troponin I (cTnI) in the cerebral organoid culture chamber and the observation of cerebral organoid and endothelial cells invading the fibrin matrix after one week of co-culture. The arrayed chip was simple to manipulate, clearly visible under a microscope, and compatible with automated pipetting devices, and therefore had significant potential for application.

Microfluidics as a Powerful Tool to Investigate Microvascular Dysfunction in Trauma Conditions: A Review of the State-of-the-Art

Skeletal muscle trauma such as fracture or crush injury can result in a life-threatening condition called acute compartment syndrome (ACS), which involves elevated compartmental pressure within a closed osteo-fascial compartment, leading to collapse of the microvasculature and resulting in necrosis of the tissue due to ischemia. Diagnosis of ACS is complex and controversial due to the lack of standardized objective methods, which results in high rates of misdiagnosis/late diagnosis, leading to permanent neuro-muscular damage. ACS pathophysiology is poorly understood at a cellular level due to the lack of physiologically relevant models. In this context, microfluidics organ-on-chip systems (OOCs) provide an exciting opportunity to investigate the cellular mechanisms of microvascular dysfunction that leads to ACS. In this article, the state-of-the-art OOCs designs and strategies used to investigate microvasculature dysfunction mechanisms is reviewed. The differential effects of hemodynamic shear stress on endothelial cell characteristics such as morphology, permeability, and inflammation, all of which are altered during microvascular dysfunction is highlighted. The article then critically reviews the importance of microfluidics to investigate closely related microvascular pathologies that cause ACS. The article concludes by discussing potential biomarkers of ACS with a special emphasis on glycocalyx and providing a future perspective.

3D cell culture models in research: applications to lung cancer pharmacology

Lung cancer remains one of the leading causes of cancer-related mortality worldwide, necessitating innovative research methodologies to improve treatment outcomes and develop novel strategies. The advent of three-dimensional (3D) cell cultures has marked a significant advancement in lung cancer research, offering a more physiologically relevant model compared to traditional two-dimensional (2D) cultures. This review elucidates the various types of 3D cell culture models currently used in lung cancer pharmacology, including spheroids, organoids and engineered tissue models, having pivotal roles in enhancing our understanding of lung cancer biology, facilitating drug development, and advancing precision medicine. 3D cell culture systems mimic the complex spatial architecture and microenvironment of lung tumours, providing critical insights into the cellular and molecular mechanisms of tumour progression, metastasis and drug responses. Spheroids, derived from commercialized cell lines, effectively model the tumour microenvironment (TME), including the formation of hypoxic and nutrient gradients, crucial for evaluating the penetration and efficacy of anti-cancer therapeutics. Organoids and tumouroids, derived from primary tissues, recapitulate the heterogeneity of lung cancers and are instrumental in personalized medicine approaches, supporting the simulation of in vivo pharmacological responses in a patient-specific context. Moreover, these models have been co-cultured with various cell types and biomimicry extracellular matrix (ECM) components to further recapitulate the heterotypic cell-cell and cell-ECM interactions present within the lung TME. 3D cultures have been significantly contributing to the identification of novel therapeutic targets and the understanding of resistance mechanisms against conventional therapies. Therefore, this review summarizes the latest findings in drug research involving lung cancer 3D models, together with the common laboratory-based assays used to study drug effects. Additionally, the integration of 3D cell cultures into lung cancer drug development workflows and precision medicine is discussed. This integration is pivotal in accelerating the translation of laboratory findings into clinical applications, thereby advancing the landscape of lung cancer treatment. By closely mirroring human lung tumours, these models not only enhance our understanding of the disease but also pave the way for the development of more effective and personalized therapeutic strategies.

The promise of Synovial Joint-on-a-Chip in rheumatoid arthritis

Rheumatoid arthritis (RA) affects millions of people worldwide, but there are limited drugs available to treat it, so acquiring a more comprehensive comprehension of the underlying reasons and mechanisms behind inflammation is crucial, as well as developing novel therapeutic approaches to manage it and mitigate or forestall associated harm. It is evident that current in vitro models cannot faithfully replicate all aspects of joint diseases, which makes them ineffective as tools for disease research and drug testing. Organ-on-a-chip (OoC) technology is an innovative platform that can mimic the microenvironment and physiological state of living tissues more realistically than traditional methods by simulating the spatial arrangement of cells and interorgan communication. This technology allows for the precise control of fluid flow, nutrient exchange, and the transmission of physicochemical signals, such as bioelectrical, mechanical stimulation and shear force. In addition, the integration of cutting-edge technologies like sensors, 3D printing, and artificial intelligence enhances the capabilities of these models. Here, we delve into OoC models with a particular focus on Synovial Joints-on-a-Chip, where we outline their structure and function, highlighting the potential of the model to advance our understanding of RA. We integrate the actual evidence regarding various OoC models and their possible integration for multisystem disease study in RA research for the first time and introduce the prospects and opportunities of the chip in RA etiology and pathological mechanism research, drug research, disease prevention and human precision medicine. Although many challenges remain, OoC holds great promise as an in vitro model that approaches physiology and dynamics.

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.

Organ-on-a-chip: future of female reproductive pathophysiological models

The female reproductive system comprises the internal and external genitalia, which communicate through intricate endocrine pathways. Besides secreting hormones that maintain the female secondary sexual characteristics, it also produces follicles and offspring. However, the in vitro systems have been very limited in recapitulating the specific anatomy and pathophysiology of women. Organ-on-a-chip technology, based on microfluidics, can better simulate the cellular microenvironment in vivo, opening a new field for the basic and clinical research of female reproductive system diseases. This technology can not only reconstruct the organ structure but also emulate the organ function as much as possible. The precisely controlled fluidic microenvironment provided by microfluidics vividly mimics the complex endocrine hormone crosstalk among various organs of the female reproductive system, making it a powerful preclinical tool and the future of pathophysiological models of the female reproductive system. Here, we review the research on the application of organ-on-a-chip platforms in the female reproductive systems, focusing on the latest progress in developing models that reproduce the physiological functions or disease features of female reproductive organs and tissues, and highlighting the challenges and future directions in this field.

Per- and poly-fluoroalkyl substances (PFAS) effects on lung health: a perspective on the current literature and future recommendations

Per- and poly-fluoroalkyl substances (PFAS) are a broad class of synthetic compounds widely used in commercial applications. The persistent nature of PFAS in the environment has earned them the epithet "forever chemicals." Concerns arise from widespread exposure to PFAS from occupational, household, and environmental sources. This widespread use of PFAS is particularly concerning, as emerging epidemiological evidence highlights their adverse effects on lung health. Such adverse impacts include impaired fetal lung development, reduced immune function in children, and potential links to lung cancer. Both in vivo and in vitro studies illuminate potential mechanisms underlying such adverse health outcomes subsequent to PFAS inhalation exposure, which may include immunomodulation, oxidative stress, and disruptions to epithelial barriers. However, evidence-based information focusing on the mechanisms of PFAS-mediated lung injury is lacking. Additionally, the discrepancies between data collected from animal and epidemiological studies highlight the need for improved approaches to better understand the toxicity results of PFAS exposure. To address these gaps, we recommend leveraging route-to-route extrapolation for risk assessment, prioritizing research on understudied PFAS, and adopting physiologically relevant, high-throughput approaches. These strategies are aimed at enhancing our understanding of PFAS inhalation effects, aiding in more informed risk management decisions. In this review, we summarize the current literature on PFAS exposure, emphasizing its adverse effects on lung health, particularly through inhalation. We then discuss the current knowledge on mechanisms underlying tissue- and cellular-level adverse outcomes caused by PFAS.

Advances and challenges in organ-on-chip technology: toward mimicking human physiology and disease in vitro

Organs-on-chips have been tissues or three-dimensional (3D) mini-organs that comprise numerous cell types and have been produced on microfluidic chips to imitate the complicated structures and interactions of diverse cell types and organs under controlled circumstances. Several morphological and physiological distinctions exist between traditional 2D cultures, animal models, and the growing popular 3D cultures. On the other hand, animal models might not accurately simulate human toxicity because of physiological variations and interspecies metabolic capability. The on-chip technique allows for observing and understanding the process and alterations occurring in metastases. The present study aimed to briefly overview single and multi-organ-on-chip techniques. The current study addresses each platform's essential benefits and characteristics and highlights recent developments in developing and utilizing technologies for single and multi-organs-on-chips. The study also discusses the drawbacks and constraints associated with these models, which include the requirement for standardized procedures and the difficulties of adding immune cells and other intricate biological elements. Finally, a comprehensive review demonstrated that the organs-on-chips approach has a potential way of investigating organ function and disease. The advancements in single and multi-organ-on-chip structures can potentially increase drug discovery and minimize dependency on animal models, resulting in improved therapies for human diseases.

The Body as an Electronic Scheme

There is no clear evidence that acupuncture points and meridians are separate organs or specific tissues. However, in traditional Chinese medicine, the mechanism of acupuncture action is associated with the vital energy concept. To identify the body's energy source and the material basis of its transmission, transformation, and use, it is necessary to consider it as an energy-generating object, with all its components. By abstracting from the body's usual structural view, we found that it is an autonomous energy-generating object. The human body generates energy through the lungs and digestive tract, which are electrochemical generator organs. Because the generated energy must be transferred to the consumer, the body has wire and transformer analogs. It bears an obvious resemblance with an electronic circuit, where cellular structures, tissues, and their combinations act as electrical and radioelements. The heart, brain, and muscles, which have well-known electrical parameters, as well as acupuncture points, offer information about the state of these electronic circuits. This article describes an extra-organ approach for systematizing body structures. It also attempts to represent the meridians and acupuncture points system as integral electro-radioelements, as well as the local circuit components of the whole body's electronic scheme.

Application and challenge of pancreatic organoids in therapeutic research

The in-vivo non-human primate animal and in-vitro cell disease models play a crucial part in the study of the mechanisms underlying the occurrence and development of pancreatic diseases, but with increasingly prominent limitations with in-depth research. Organoids derived from human pluripotent and adult stem cells resemble human in-vivo organs in their cellular composition, spatial tissue structure and physiological function, making them as an advantageous research tool. Up until now, numerous human organoids, including pancreas, have been effectively developed, demonstrating significant potential for research in organ development, disease modeling, drug screening, and regenerative medicine. However, different from intestine, liver and other organs, the pancreas is the only special organ in the human body, consisting of an exocrine gland and an endocrine gland. Thus, the development of pancreatic organoid technology faces greater challenges, and how to construct a composite pancreatic organoid with exocrine and endocrine gland is still difficult in current research. By reviewing the fundamental architecture and physiological role of the human pancreas, along with the swiftly developing domain of pancreatic organoids, we summarize the method and characteristics of human pancreatic organoids, and its application in modeling pancreatic diseases, as a platform for individualized drug screening and in regenerative medicine study. As the first comprehensive review that focus on the pharmacological study of human pancreatic organoid, the review hopes to help scholars to have a deeper understanding in the study of pancreatic organoid.

Parkinson's disease and gut microbiota: from clinical to mechanistic and therapeutic studies

Parkinson's disease (PD) is one of the most prevalent neurodegenerative diseases. The typical symptomatology of PD includes motor symptoms; however, a range of nonmotor symptoms, such as intestinal issues, usually occur before the motor symptoms. Various microorganisms inhabiting the gastrointestinal tract can profoundly influence the physiopathology of the central nervous system through neurological, endocrine, and immune system pathways involved in the microbiota-gut-brain axis. In addition, extensive evidence suggests that the gut microbiota is strongly associated with PD. This review summarizes the latest findings on microbial changes in PD and their clinical relevance, describes the underlying mechanisms through which intestinal bacteria may mediate PD, and discusses the correlations between gut microbes and anti-PD drugs. In addition, this review outlines the status of research on microbial therapies for PD and the future directions of PD-gut microbiota research.

Effects of short-chain per- and polyfluoroalkyl substances (PFAS) on toxicologically relevant gene expression profiles in a liver-on-a-chip model

Short-chain per- and polyfluoroalkyl substances (PFAS) are highly stable and widely used environmental contaminants that pose potential health risks to humans. Aggregating reliable mechanistic information for safety assessments necessitates physiologically relevant high-throughput screening approaches. Here, we demonstrated the utility of a liver-on-a-chip model to investigate the effects of five short-chain PFAS at low (1 nM) and high (1 μM) concentrations on toxicologically-relevant gene expression profiles using the QuantiGene® Plex Assay. We found that the short-chain PFAS tested in this study modulated the expression of ABCG2, a gene encoding for the breast cancer resistance protein (BCRP), with marked and significant upregulation (up to 4-fold) observed for all but one of the short-chain PFAS tested. PFBS and HFPO-DA repressed SLCO1B3 expression, a gene that encodes for an essential liver-specific organic anion transporter. High concentrations of PFBS, PFHxA, and PFHxS upregulated the expression of genes encCYP1A1,CYP2B6 and CYP2C19 with the same treatments resulting in the repression of the expression of the gene encoding CYP1A2. This dysregulation could have consequences for the clearance of endogenous compounds and xenobiotics. However, we acknowledge that increased expression of genes encoding for transporters and biotransformation enzymes may or may not indicate changes to their protein expression or activity. Overall, our study provides important insights into the effects of short-chain PFAS on liver function and their potential implications for human health. The use of the liver-on-a-chip model in combination with the QuantiGene® Plex Assay may be a valuable tool for future high-throughput screening and gene expression profiling in toxicology studies.

Fluid flow to mimic organ function in 3D in vitro models

Many different strategies can be found in the literature to model organ physiology, tissue functionality, and disease in vitro; however, most of these models lack the physiological fluid dynamics present in vivo. Here, we highlight the importance of fluid flow for tissue homeostasis, specifically in vessels, other lumen structures, and interstitium, to point out the need of perfusion in current 3D in vitro models. Importantly, the advantages and limitations of the different current experimental fluid-flow setups are discussed. Finally, we shed light on current challenges and future focus of fluid flow models applied to the newest bioengineering state-of-the-art platforms, such as organoids and organ-on-a-chip, as the most sophisticated and physiological preclinical platforms.

Preclinical in vitro evaluation of implantable materials: conventional approaches, new models and future directions

Nowadays, implants and prostheses are widely used to repair damaged tissues or to treat different diseases, but their use is associated with the risk of infection, inflammation and finally rejection. To address these issues, new antimicrobial and anti-inflammatory materials are being developed. Aforementioned materials require their thorough preclinical testing before clinical applications can be envisaged. Although many researchers are currently working on new in vitro tissues for drug screening and tissue replacement, in vitro models for evaluation of new biomaterials are just emerging and are extremely rare. In this context, there is an increased need for advanced in vitro models, which would best recapitulate the in vivo environment, limiting animal experimentation and adapted to the multitude of these materials. Here, we overview currently available preclinical methods and models for biological in vitro evaluation of new biomaterials. We describe several biological tests used in biocompatibility assessment, which is a primordial step in new material's development, and discuss existing challenges in this field. In the second part, the emphasis is made on the development of new 3D models and approaches for preclinical evaluation of biomaterials. The third part focuses on the main parameters to consider to achieve the optimal conditions for evaluating biocompatibility; we also overview differences in regulations across different geographical regions and regulatory systems. Finally, we discuss future directions for the development of innovative biomaterial-related assays: in silico models, dynamic testing models, complex multicellular and multiple organ systems, as well as patient-specific personalized testing approaches.

Systems bioengineering approaches for developmental toxicology

Developmental toxicology is the field of study that examines the effects of chemical and physical agents on developing organisms. By using principles of systems biology and bioengineering, a systems bioengineering approach could be applied to study the complex interactions between developing organisms, the environment, and toxic agents. This approach would result in a holistic understanding of the effects of toxic agents on organisms, by considering the interactions between different biological systems and the impacts of toxicants on those interactions. It would be useful in identifying key biological pathways and mechanisms affected by toxic agents, as well as in the development of predictive models to assess potential risks of exposure to toxicants during development. In this review, we discuss the relevance of systems bioengineering to the field of developmental toxicity and provide up-to-date examples that illustrate the use of engineering principles for this application.

Emerging trends in organ-on-a-chip systems for drug screening

New drug discovery is under growing pressure to satisfy the demand from a wide range of domains, especially from the pharmaceutical industry and healthcare services. Assessment of drug efficacy and safety prior to human clinical trials is a crucial part of drug development, which deserves greater emphasis to reduce the cost and time in drug discovery. Recent advances in microfabrication and tissue engineering have given rise to organ-on-a-chip, an in vitro model capable of recapitulating human organ functions in vivo and providing insight into disease pathophysiology, which offers a potential alternative to animal models for more efficient pre-clinical screening of drug candidates. In this review, we first give a snapshot of general considerations for organ-on-a-chip device design. Then, we comprehensively review the recent advances in organ-on-a-chip for drug screening. Finally, we summarize some key challenges of the progress in this field and discuss future prospects of organ-on-a-chip development. Overall, this review highlights the new avenue that organ-on-a-chip opens for drug development, therapeutic innovation, and precision medicine.

3D cancer models: One step closer to in vitro human studies

Cancer immunotherapy is the great breakthrough in cancer treatment as it displayed prolonged progression-free survival over conventional therapies, yet, to date, in only a minority of patients. In order to broad cancer immunotherapy clinical applicability some roadblocks need to be overcome, first among all the lack of preclinical models that faithfully depict the local tumor microenvironment (TME), which is known to dramatically affect disease onset, progression and response to therapy. In this review, we provide the reader with a detailed overview of current 3D models developed to mimick the complexity and the dynamics of the TME, with a focus on understanding why the TME is a major target in anticancer therapy. We highlight the advantages and translational potentials of tumor spheroids, organoids and immune Tumor-on-a-Chip models in disease modeling and therapeutic response, while outlining pending challenges and limitations. Thinking forward, we focus on the possibility to integrate the know-hows of micro-engineers, cancer immunologists, pharmaceutical researchers and bioinformaticians to meet the needs of cancer researchers and clinicians interested in using these platforms with high fidelity for patient-tailored disease modeling and drug discovery.

Biosensors integrated 3D organoid/organ-on-a-chip system: A real-time biomechanical, biophysical, and biochemical monitoring and characterization

As a full-fidelity simulation of human cells, tissues, organs, and even systems at the microscopic scale, Organ-on-a-Chip (OOC) has significant ethical advantages and development potential compared to animal experiments. The need for the design of new drug high-throughput screening platforms and the mechanistic study of human tissues/organs under pathological conditions, the evolving advances in 3D cell biology and engineering, etc., have promoted the updating of technologies in this field, such as the iteration of chip materials and 3D printing, which in turn facilitate the connection of complex multi-organs-on-chips for simulation and the further development of technology-composite new drug high-throughput screening platforms. As the most critical part of organ-on-a-chip design and practical application, verifying the success of organ model modeling, i.e., evaluating various biochemical and physical parameters in OOC devices, is crucial. Therefore, this paper provides a logical and comprehensive review and discussion of the advances in organ-on-a-chip detection and evaluation technologies from a broad perspective, covering the directions of tissue engineering scaffolds, microenvironment, single/multi-organ function, and stimulus-based evaluation, and provides a more comprehensive review of the progress in the significant organ-on-a-chip research areas in the physiological state.

Synovial joint-on-a-chip for modeling arthritis: progress, pitfalls, and potential

Disorders of the synovial joint, such as osteoarthritis (OA) and rheumatoid arthritis (RA), afflict a substantial proportion of the global population. However, current clinical management has not been focused on fully restoring the native function of joints. Organ-on-chip (OoC), also called a microphysiological system, which typically accommodates multiple human cell-derived tissues/organs under physiological culture conditions, is an emerging platform that potentially overcomes the limitations of current models in developing therapeutics. Herein, we review major steps in the generation of OoCs for studying arthritis, discuss the challenges faced when these novel platforms enter the next phase of development and application, and present the potential for OoC technology to investigate the pathogenesis of joint diseases and the development of efficacious therapies.

Nicotinamide Mononucleotide Alleviates Angiotensin II-Induced Human Aortic Smooth Muscle Cell Senescence in a Microphysiological Model

ABSTRACT

The occurrence and development of aortic aneurysms are accompanied by senescence of human aortic smooth muscle cells (HASMCs). Because the mechanism of HASMC senescence has not been fully elucidated, the efficacy of various antisenescence treatments varies. Decreased nicotinamide adenine dinucleotide (NAD + ) levels are one of the mechanisms of cell senescence, and there is a lack of evidence on whether increasing NAD + levels could alleviate HASMC senescence and further retard the progression of aortic aneurysms.We constructed an HASMC-based organ-on-a-chip microphysiological model. RNA sequencing was performed on cell samples from the vehicle control and angiotensin II groups to explore biological differences. We detected cellular senescence markers and NAD + levels in HASMC-based organ-on-a-chip. Subsequently, we pretreated HASMC using the synthetic precursor of NAD + , nicotinamide mononucleotide, and angiotensin II treatment, and used rhythmic stretching to investigate whether nicotinamide mononucleotide could delay HASMC senescence.The HASMC-based organ-on-a-chip model can simulate the biomechanical microenvironment of HASMCs in vivo, and the use of angiotensin II in the model replicated senescence in HASMCs. The senescence of HASMCs was accompanied by downregulation of the expression level of nicotinamide phosphoribosyltransferase and NAD + . Pretreatment with nicotinamide mononucleotide significantly increased the NAD + level and alleviated the senescence of HASMCs, but did not change the expression level of nicotinamide phosphoribosyltransferase.Our study provides a complementary research platform between traditional cell culture and animal experiments to explore HASMC senescence in aortic aneurysms. Furthermore, it provides evidence for NAD + boosting therapy in the clinical treatment of aortic aneurysms.

Organ-on-a-chip with integrated semitransparent organic electrodes for barrier function monitoring

Organs-on-a-chip (OoC) are cell culture platforms that replicate key functional units of tissues in vitro. Barrier integrity and permeability evaluation are of utmost importance when studying barrier-forming tissues. Impedance spectroscopy is a powerful tool and is widely used to monitor barrier permeability and integrity in real-time. However, data comparison across devices is misleading due to the generation of a non-homogenous field across the tissue barrier, making impedance data normalization very challenging. In this work, we address this issue by integrating PEDOT:PSS electrodes for barrier function monitoring with impedance spectroscopy. The semitransparent PEDOT:PSS electrodes cover the entire cell culture membrane providing a homogenous electric field across the entire membrane making the cell culture area equally accountable to the measured impedance. To the best of our knowledge, PEDOT:PSS has never been used solely to monitor the impedance of cellular barriers while enabling optical inspection in the OoC. The performance of the device is demonstrated by lining the device with intestinal cells where we monitored barrier formation under flow conditions, as well as barrier disruption and recovery under exposure to a permeability enhancer. The barrier tightness and integrity, and the intercellular cleft have been evaluated by analyzing the full impedance spectrum. Furthermore, the device is autoclavable paving the way toward more sustainable OoC options.

Nanostructured steady-state nanocarriers for nutrients preservation and delivery

Food bioactives possess specific physiological benefits of preventing certain diet-related chronic diseases or maintain human health. However, the limitations of the bioactives are their poor stability, lower water solubility and unacceptable bioaccessibility. Structure damage or degradation is often found for the bioactives under certain environmental conditions like high temperature, strong light, extreme pH or high oxygen concentration during food processing, packaging, storage and absorption. Nanostructured steady-state nanocarriers have shown great potential in overcoming the drawbacks for food bioactives. Various delivery systems including solid form delivery system, liquid form delivery system and encapsulation technology have been developed. The embedded food nutrients can largely decrease the loss and degradation during food processing, packaging and storage. The design and application of stimulus and targeted delivery systems can improve the stability, bioavailability and efficacy of the food bioactives upon oral consumption due to enzymatic degradation in the gastrointestinal tract. The food nutrients encapsulated in the smart delivery system can be well protected against degradation during oral administration, thus improving the bioavailability and releazing controlled or targeted release for food nutrients. The encapsulated food bioactives show great potential in nutrition therapy for sub-health status and disease. Much effort is required to design and prepare more biocompatible nanostructured steady-state nanocarriers using food-grade protein or polysaccharides as wall materials, which can be used in food industry and maintain the human health.

Physiological media advance cell culture experiments

The metabolism plays a fundamental role in cellular signaling pathways, but commonly used cell culture media do not reflect physiological metabolite concentrations. The metabolic control hub mammalian target of rapamycin complex 1 (mTORC1) kinase is an illuminating example that it is about time to advance our cell culture to become more physiological and relevant.

Engineered organoids in oral and maxillofacial regeneration

Oral and maxillofacial organoids, as three-dimensional study models of organs, have attracted increasing attention in tissue regeneration and disease modeling. However, traditional strategies for organoid construction still fail to precisely recapitulate the key characteristics of real organs, due to the difficulty in controlling the self-organization of cells in vitro. This review aims to summarize the recent progress of novel approaches to engineering oral and maxillofacial organoids. First, we introduced the necessary components and their roles in forming oral and maxillofacial organoids. Besides, we discussed cutting-edge technology in advancing the architecture and function of organoids, especially focusing on oral and maxillofacial tissue regeneration via novel strategy with designed cell-signal scaffold compounds. Finally, current limitations and future prospects of oral and maxillofacial organoids were represented to provide guidance for further disciplinary progression and clinical application to achieve organ regeneration.

A Stand-Alone Microfluidic Chip for Long-Term Cell Culture

Live-cell microscopy is crucial for biomedical studies and clinical tests. The technique is, however, limited to few laboratories due to its high cost and bulky size of the necessary culture equipment. In this study, we propose a portable microfluidic-cell-culture system, which is merely 15 cm×11 cm×9 cm in dimension, powered by a conventional alkali battery and costs less than USD 20. For long-term cell culture, a fresh culture medium exposed to 5% CO2 is programmed to be delivered to the culture chamber at defined time intervals. The 37 °C culture temperature is maintained by timely electrifying the ITO glass slide underneath the culture chamber. Our results demonstrate that 3T3 fibroblasts, HepG2 cells, MB-231 cells and tumor spheroids can be well-maintained for more than 48 h on top of the microscope stage and show physical characters (e.g., morphology and mobility) and growth rate on par with the commercial stage-top incubator and the widely adopted CO2 incubator. The proposed portable cell culture device is, therefore, suitable for simple live-cell studies in the lab and cell experiments in the field when samples cannot be shipped.

Microfluidic dose-response platform to track the dynamics of drug response in single mycobacterial cells

Preclinical analysis of drug efficacy is critical for drug development. However, conventional bulk-cell assays statically assess the mean population behavior, lacking resolution on drug-escaping cells. Inaccurate estimation of efficacy can lead to overestimation of compounds, whose efficacy will not be confirmed in the clinic, or lead to rejection of valuable candidates. Time-lapse microfluidic microscopy is a powerful approach to characterize drugs at high spatiotemporal resolution, but hard to apply on a large scale. Here we report the development of a microfluidic platform based on a pneumatic operating principle, which is scalable and compatible with long-term live-cell imaging and with simultaneous analysis of different drug concentrations. We tested the platform with mycobacterial cells, including the tubercular pathogen, providing the first proof of concept of a single-cell dose-response assay. This dynamic in-vitro model will prove useful to probe the fate of drug-stressed cells, providing improved predictions of drug efficacy in the clinic.

Organs-on-Chips Platforms Are Everywhere: A Zoom on Biomedical Investigation

Over the decades, conventional in vitro culture systems and animal models have been used to study physiology, nutrient or drug metabolisms including mechanical and physiopathological aspects. However, there is an urgent need for Integrated Testing Strategies (ITS) and more sophisticated platforms and devices to approach the real complexity of human physiology and provide reliable extrapolations for clinical investigations and personalized medicine. Organ-on-a-chip (OOC), also known as a microphysiological system, is a state-of-the-art microfluidic cell culture technology that sums up cells or tissue-to-tissue interfaces, fluid flows, mechanical cues, and organ-level physiology, and it has been developed to fill the gap between in vitro experimental models and human pathophysiology. The wide range of OOC platforms involves the miniaturization of cell culture systems and enables a variety of novel experimental techniques. These range from modeling the independent effects of biophysical forces on cells to screening novel drugs in multi-organ microphysiological systems, all within microscale devices. As in living biosystems, the development of vascular structure is the salient feature common to almost all organ-on-a-chip platforms. Herein, we provide a snapshot of this fast-evolving sophisticated technology. We will review cutting-edge developments and advances in the OOC realm, discussing current applications in the biomedical field with a detailed description of how this technology has enabled the reconstruction of complex multi-scale and multifunctional matrices and platforms (at the cellular and tissular levels) leading to an acute understanding of the physiopathological features of human ailments and infections in vitro.

Tissue hydraulics in reproduction

The development of functional eggs and sperm are critical processes in mammalian development as they ensure successful reproduction and species propagation. While past studies have identified important genes that regulate these processes, the roles of luminal flow and fluid stress in reproductive biology remain less well understood. Here, we discuss recent evidence that support the diverse functions of luminal fluid in oogenesis, spermatogenesis and embryogenesis. We also review emerging techniques that allow for precise quantification and perturbation of tissue hydraulics in female and male reproductive systems, and propose new questions and approaches in this field. We hope this review will provide a useful resource to inspire future research in tissue hydraulics in reproductive biology and diseases.

Microbiome as an immune regulator in health, disease, and therapeutics

New discoveries in drugs and drug delivery systems are focused on identifying and delivering a pharmacologically effective agent, potentially targeting a specific molecular component. However, current drug discovery and therapeutic delivery approaches do not necessarily exploit the complex regulatory network of an indispensable microbiota that has been engineered through evolutionary processes in humans or has been altered by environmental exposure or diseases. The human microbiome, in all its complexity, plays an integral role in the maintenance of host functions such as metabolism and immunity. However, dysregulation in this intricate ecosystem has been linked with a variety of diseases, ranging from inflammatory bowel disease to cancer. Therapeutics and bacteria have an undeniable effect on each other and understanding the interplay between microbes and drugs could lead to new therapies, or to changes in how existing drugs are delivered. In addition, targeting the human microbiome using engineered therapeutics has the potential to address global health challenges. Here, we present the challenges and cutting-edge developments in microbiome-immune cell interactions and outline novel targeting strategies to advance drug discovery and therapeutics, which are defining a new era of personalized and precision medicine.

Lab-on-PCB: One step away from the accomplishment of μTAS?

The techniques, protocols, and advancements revolving around printed circuit boards (PCBs) have been gaining sustained attention in the realm of micro-total analysis systems (μTAS) as more and more efforts are devoted to searching for standardized, highly reliable, and industry-friendly solutions for point-of-care diagnostics. In this Perspective, we set out to identify the current state in which the field of μTAS finds itself, the challenges encountered by researchers in the implementation of these technologies, and the potential improvements that can be targeted to meet the current demands. We also line up some trending innovations, such as 3D printing and wearable devices, along with the development of lab-on-PCB to increase the possibility of multifunctional biosensing activities propelled by integrated microfluidic networks for a wider range of applications, anticipating to catalyze the full potential of μTAS.

Bioengineering Strategies to Create 3D Cardiac Constructs from Human Induced Pluripotent Stem Cells

Human induced pluripotent stem cells (hiPSCs) can be used to generate various cell types in the human body. Hence, hiPSC-derived cardiomyocytes (hiPSC-CMs) represent a significant cell source for disease modeling, drug testing, and regenerative medicine. The immaturity of hiPSC-CMs in two-dimensional (2D) culture limit their applications. Cardiac tissue engineering provides a new promise for both basic and clinical research. Advanced bioengineered cardiac in vitro models can create contractile structures that serve as exquisite in vitro heart microtissues for drug testing and disease modeling, thereby promoting the identification of better treatments for cardiovascular disorders. In this review, we will introduce recent advances of bioengineering technologies to produce in vitro cardiac tissues derived from hiPSCs.

Vertical Organic Electrochemical Transistors and Electronics for Low Amplitude Micro-Organ Signals

Electrical signals are fundamental to key biological events such as brain activity, heartbeat, or vital hormone secretion. Their capture and analysis provide insight into cell or organ physiology and a number of bioelectronic medical devices aim to improve signal acquisition. Organic electrochemical transistors (OECT) have proven their capacity to capture neuronal and cardiac signals with high fidelity and amplification. Vertical PEDOT:PSS-based OECTs (vOECTs) further enhance signal amplification and device density but have not been characterized in biological applications. An electronic board with individually tuneable transistor biases overcomes fabrication induced heterogeneity in device metrics and allows quantitative biological experiments. Careful exploration of vOECT electric parameters defines voltage biases compatible with reliable transistor function in biological experiments and provides useful maximal transconductance values without influencing cellular signal generation or propagation. This permits successful application in monitoring micro-organs of prime importance in diabetes, the endocrine pancreatic islets, which are known for their far smaller signal amplitudes as compared to neurons or heart cells. Moreover, vOECTs capture their single-cell action potentials and multicellular slow potentials reflecting micro-organ organizations as well as their modulation by the physiological stimulator glucose. This opens the possibility to use OECTs in new biomedical fields well beyond their classical applications.

Multiorgan microphysiological systems as tools to interrogate interorgan crosstalk and complex diseases

Metabolic and inflammatory disorders such as autoimmune and neurodegenerative diseases are increasing at alarming rates. Many of these are not tissue-specific occurrences but complex, systemic pathologies of unknown origin for which no cure exists. Such complexity obscures causal relationships among factors regulating disease progression. Emerging technologies mimicking human physiology, such as microphysiological systems (MPSs), offer new possibilities to provide clarity in systemic metabolic and inflammatory diseases. Controlled interaction of multiple MPSs and the scalability of biological complexity in MPSs, supported by continuous multiomic monitoring, might hold the key to identifying novel relationships between interorgan crosstalk, metabolism, and immunity. In this perspective, I aim to discuss the current state of modeling multiorgan physiology and evaluate current opportunities and challenges.

The use of in vitro methods in assessing human health risks associated with short-chain perfluoroalkyl and polyfluoroalkyl substances (PFAS)

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a large class of industrial chemicals with a ubiquitous and persistent presence in the environment. Of the thousands of PFAS used by consumers and industry, very few have been thoroughly characterized for potential adverse effects. This is especially true for the novel short-chain (C < 8) alternatives that replaced legacy PFAS. Perfluoroalkyl and polyfluoroalkyl substances have revealed inconsistencies in the toxicokinetics predicted by animal models and empirical findings in humans. To adequately assess the possible health effects of short-chain PFAS, there is a need for robust aggregated data sets on the mechanistic underpinnings and physiochemical properties of these alternatives. Acquiring relevant data on the health effects of short-chain PFAS can be achieved through high-throughput methods supported by in vitro human cell-based models. This review briefly summarizes some of the toxicity data obtained using human cells in vitro, discusses the advantages and limitations of cell-based models, and provides insights on potential solutions to challenges presented with the use of these methods for use in safety assessments.

Stem Cell-Based Embryo Models: En Route to a Programmable Future

Early-stage human embryogenesis, such as implantation, gastrulation, and neurulation, are critical for successful pregnancy. For decades, our knowledge about these stages has been limited by the inaccessibility to such embryo specimens in vivo and the difficulty in rebuilding them in vitro. Although human embryos could be cultured in vitro beyond implantation, it remains challenging for the cultured embryos to recapitulate the continuous, coordinated morphogenesis and cytodifferentiation as seen in vivo. Stem cell-based embryo models, mainly derived from human pluripotent stem cells, are organized structures mimicking essential developmental processes in the early-stage human embryos. Despite their invaluable potentials, most embryo models are based on the self-organization of human pluripotent stem cells, which are limited in controllability, reproducibility, and developmental fidelity. Recently, the integration of bioengineered tools and stem cell biology has fueled a technological transformation towards programmable, highly complex, high-fidelity stem cell-based embryo models. Given its scientific and clinical significance, we present an overview of recent paradigm-shifting advances as well as historical perspectives regarding the past, present, and future of synthetic human embryology. Following the developmental roadmap of human embryogenesis, we critically review existing stem cell-based models for implantation, gastrulation, and neurulation, respectively. We highlight the limitations encountered by autonomous self-organization strategy and discuss the concept and application of guided cell organization as a game-changer for innovating next-generation embryo models. Future endeavors in synthetic human embryology should rationally leverage both the self-organizing power and programmable microenvironmental guidance to secure faithful reconstructions of the hierarchical orders of human embryogenesis in vitro.

Microneedle arrays integrated with living organisms for smart biomedical applications

Various living organisms have proven to influence human health significantly, either in a commensal or pathogenic manner. Harnessing the creatures may remarkably improve human healthcare and cure the intractable illness that is challenged using traditional drugs or surgical approaches. However, issues including limited biocompatibility, poor biosafety, inconvenience for personal handling, and low patient compliance greatly hinder the biomedical and clinical applications of living organisms when adopting them for disease treatment. Microneedle arrays (MNAs), emerging as a promising candidate of biomedical devices with the functional diversity and minimal invasion, have exhibited great potential in the treatment of a broad spectrum of diseases, which is expected to improve organism-based therapies. In this review, we systemically summarize the technologies employed for the integration of MNAs with specific living organisms including diverse viruses, bacteria, mammal cells and so on. Moreover, their applications such as vaccination, anti-infection, tumor therapy and tissue repairing are well illustrated. Challenges faced by current strategies, and the perspectives of integrating more living organisms, adopting smarter materials, and developing more advanced technologies in MNAs for future personalized and point-of-care medicine, are also discussed. It is believed that the combination of living organisms with functional MNAs would hold great promise in the near future due to the advantages of both biological and artificial species.

[Hepatic organoids: What are the challenges?]

The study and understanding of liver organogenesis have allowed the development of protocols for pluripotent stem cells differentiation to overcome the lack of primary cells, providing an almost unlimited source of liver cells. However, as their differentiation in conventional 2D culture systems has shown serious limits, hepatic organoids derived from human pluripotent stem cells represent a promising alternative. These complex and organized structures, containing one or more cell types, make it possible to recapitulate in vitro some of the organ functions, thus enabling numerous applications such as the study of the liver development, the mass production of functional liver cells for transplantation or the development of bioartificial livers, as well as the in vitro modeling of hepatic pathologies allowing high throughput applications in drug screening or toxicity studies. Economic and ethical issues must also be taken into account before using these organoids in therapeutic applications.