Mature induced-pluripotent-stem-cell-derived human podocytes reconstitute kidney glomerular-capillary-wall function on a chip. Nat Biomed Eng. 2017;1. [PMID: 29038743 PMCID: PMC5639718 DOI: 10.1038/s41551-017-0069]

Application of new approach methodologies for nonclinical safety assessment of drug candidates

The development of new approach methodologies (NAMs) and advances with in vitro testing systems have prompted revisions in regulatory guidelines and inspired dedicated in vitro/ex vivo studies for nonclinical safety assessment. This Review by a safety reflection initiative subgroup of the European Federation of Pharmaceutical Industries and Associations (EFPIA)/Preclinical Development Expert Group (PDEG) summarizes the current state and potential application of in vitro studies using human-derived material for safety assessment in drug development. It focuses on case studies from recent projects in which animal models alone proved to be limited or inadequate for safety testing. It further highlights four categories of drug candidates for which alternative in vitro approaches are applicable and discusses progress in using in vitro testing solutions for safety assessment in these categories. Finally, the article highlights new risk assessment strategies, initiatives and consortia promoting the advancement of NAMs. This collective work is meant to encourage the use of NAMs for more human-relevant safety assessment, which should ultimately result in reduced animal testing for drug development.

Interfacial engineering for biomolecule immobilisation in microfluidic devices

Microfluidic devices are used for various applications in biology and medicine. From on-chip modelling of human organs for drug screening and fast and straightforward point-of-care (POC) detection of diseases to sensitive biochemical analysis, these devices can be custom-engineered using low-cost techniques. The microchannel interface is essential for these applications, as it is the interface of immobilised biomolecules that promote cell capture, attachment and proliferation, sense analytes and metabolites or provide enzymatic reaction readouts. However, common microfluidic materials do not facilitate the stable immobilisation of biomolecules required for relevant applications, making interfacial engineering necessary to attach biomolecules to the microfluidic surfaces. Interfacial engineering is performed through various immobilisation mechanisms and surface treatment techniques, which suitably modify the surface properties like chemistry and energy to obtain robust biomolecule immobilisation and long-term storage stability suitable for the final application. In this review, we provide an overview of the status of interfacial engineering in microfluidic devices, covering applications, the role of biomolecules, their immobilisation pathways and the influence of microfluidic materials. We then propose treatment techniques to optimise performance for various biological and medical applications and highlight future areas of development.

Organ-on-a-chip: Quo vademus? Applications and regulatory status

Organ-on-a-chip systems, also referred to as microphysiological systems (MPS), represent an advance in bioengineering microsystems designed to mimic key aspects of human organ physiology and function. Drawing inspiration from the intricate and hierarchical architecture of the human body, these innovative platforms have emerged as invaluable in vitro tools with wide-ranging applications in drug discovery and development, as well as in enhancing our understanding of disease physiology. The facility to replicate human tissues within physiologically relevant three-dimensional multicellular environments empowers organ-on-a-chip systems with versatility throughout different stages of the drug development process. Moreover, these systems can be tailored to mimic specific disease states, facilitating the investigation of disease progression, drug responses, and potential therapeutic interventions. In particular, they can demonstrate, in early-phase pre-clinical studies, the safety and toxicity profiles of potential therapeutic compounds. Furthermore, they play a pivotal role in the in vitro evaluation of drug efficacy and the modeling of human diseases. One of the most promising prospects of organ-on-a-chip technology is to simulate the pathophysiology of specific subpopulations and even individual patients, thereby being used in personalized medicine. By mimicking the physiological responses of diverse patient groups, these systems hold the promise of revolutionizing therapeutic strategies, guiding them towards tailored intervention to the unique needs of each patient. This review presents the development status and evolution of microfluidic platforms that have facilitated the transition from cells to organs recreated on chips and some of the opportunities and applications offered by organ-on-a-chip technology. Additionally, the current potential and future perspectives of these microphysiological systems and the challenges this technology still faces are discussed.

Trametinib ameliorated Adriamycin-induced podocyte injury by inhibiting METTL3 modified m6A RCAN1 RNA methylation

N6-methyladenosine (m6A) plays a crucial role in kidney diseases. Methyltransferase-like 3 (METTL3) as a key m6A writer can be regulated by trametinib. However, the epigenetic regulation of trametinib in focal segmental glomerulosclerosis (FSGS) remains unclear. We investigated whether trametinib protects podocytes by modulating METTL3-methylated target RNAs. Regulator of calcineurin 1 (RCAN1) was predicted as a target binding RNA of METTL3 by THEW database. Immunostaining of METTL3 and RCAN1 with podocyte marker Wilm's tumor-1 (WT-1) confirmed their localization within podocytes in renal biopsy from FSGS patients. Transfection METTL3 to human podocytes reduced WT-1, synaptopodin (SYNPO), and RCAN1 protein levels. Total m6A, m6A methylated RNA of RCAN1 increased and total RCAN1 mRNA decreased. Inhibition of METTL3 using siRNA or trametinib reversed these changes and attenuated the ADR-induced downregulation of WT-1 and SYNPO in vitro. In ADR-induced FSGS mice, trametinib ameliorated proteinuria, hypoalbuminemia, renal dysfunction, glomerulosclerosis and podocyte foot process effacement. Additionally, trametinib preserved podocyte function assessed by WT-1 and SYNPO as well as delayed renal fibrosis assessed by α-smooth muscle actin and fibronectin. Consistent with results in vitro, trametinib also decreased the ADR-induced upregulation of METTL3 and reversed the changed levels of total m6A, m6A methylated Rcan1 and total Rcan1 in FSGS mice. In conclusion, trametinib may serve as a renal protective agent for FSGS by regulating METTL3-dependent RCAN1 methylation levels.

Unlocking the full potential of human pluripotent stem cell-derived kidney organoids through bioengineering

Human pluripotent stem cells hold inherent properties, allowing researchers to recapitulate key morphogenetic processes. These characteristics, coupled with bioengineering techniques, have led to the definition of early procedures to derive organ-like cell cultures, the so-called organoids. With regard to kidney organoids, challenges stand ahead, such as the need to enhance cellular composition, maturation, and function to that found in the native organ. To this end, the kidney organoid field has begun to nourish from innovative engineering approaches aiming to gain control on the externally imposed biochemical and biophysical cues. In this review, we first introduce how previous research in kidney development and human pluripotent stem cells has informed the establishment of current kidney organoid procedures. We then discuss recent engineering approaches to guide kidney organoid self-organization, differentiation, and maturation. In addition, we present current strategies to engineer vascularization and promote in vivo-like physiological microenvironments as potential solutions to increase kidney organoid lifespan and functionality. We finally emphasize how working at the cusp of cell mechanics and computational biology will set the ground for successful translational applications of kidney organoids.

From organoids to organoids-on-a-chip: Current applications and challenges in biomedical research

ABSTRACT

The high failure rates in clinical drug development based on animal models highlight the urgent need for more representative human models in biomedical research. In response to this demand, organoids and organ chips were integrated for greater physiological relevance and dynamic, controlled experimental conditions. This innovative platform-the organoids-on-a-chip technology-shows great promise in disease modeling, drug discovery, and personalized medicine, attracting interest from researchers, clinicians, regulatory authorities, and industry stakeholders. This review traces the evolution from organoids to organoids-on-a-chip, driven by the necessity for advanced biological models. We summarize the applications of organoids-on-a-chip in simulating physiological and pathological phenotypes and therapeutic evaluation of this technology. This section highlights how integrating technologies from organ chips, such as microfluidic systems, mechanical stimulation, and sensor integration, optimizes organoid cell types, spatial structure, and physiological functions, thereby expanding their biomedical applications. We conclude by addressing the current challenges in the development of organoids-on-a-chip and offering insights into the prospects. The advancement of organoids-on-a-chip is poised to enhance fidelity, standardization, and scalability. Furthermore, the integration of cutting-edge technologies and interdisciplinary collaborations will be crucial for the progression of organoids-on-a-chip technology.

Kidney Fibrosis In Vitro and In Vivo Models: Path Toward Physiologically Relevant Humanized Models

Chronic kidney disease (CKD) affects over 10% of the global population and is a leading cause of mortality. Kidney fibrosis, a key endpoint of CKD, disrupts nephron tubule anatomy and filtration function, and disease pathomechanisms are not fully understood. Kidney fibrosis is currently investigated with in vivo models, that gradually support the identification of possible mechanisms of fibrosis, but with limited translational research, as they do not fully recapitulate human kidney physiology, metabolism, and molecular pathways. In vitro 2D cell culture models are currently used, as a starting point in disease modeling and pharmacology, however, they lack the 3D kidney architecture complexity and functions. The failure of several therapies and drugs in clinical trials highlights the urgent need for advanced 3D in vitro models. This review discusses the urinary system's anatomy, associated diseases, and diagnostic methods, including biomarker analysis and tissue biopsy. It evaluates 2D and in vivo models, highlighting their limitations. The review explores the state-of-the-art 3D-humanized in vitro models, such as 3D cell aggregates, on-chip models, biofabrication techniques, and hybrid models, which aim to mimic kidney morphogenesis and functions. These advanced models hold promise for translating new therapies and drugs for kidney fibrosis into clinics.

Sensor-combined organ-on-a-chip for pharmaceutical and medical sciences: from design and materials to typical biomedical applications

Organ-on-a-chip (OoC) is a breakthrough technology in biomedicine. As microphysiological systems constructed in vitro, OoCs can simulate the main structures and functions of human organs, thereby providing a powerful tool for drug screening and disease model construction. Furthermore, the coupling of OoCs and sensors has been an innovative discovery in the field of biomedical and electronic engineering in recent years. The integration of sensors into OoCs allows the real-time monitoring of the changes in the microenvironmental parameters within the chip, reflecting the physiological responses of cells or tissues in the OoC and providing more accurate data support for drug development and disease treatment. In this work, we briefly outline the design ideas of OoCs, summarize the commonly used materials for OoCs and their advantages and disadvantages, and provide the most recent practical examples of the combination of OoCs and sensors in pharmaceutical and medical sciences. Furthermore, perspectives, challenges and their solutions in the future development of this technology are provided, with the aim to inspire the researchers to work toward the subsequent development of OoCs having improved reliability.

Live Biotherapeutic Products for Metabolic Diseases: Development Strategies, Challenges, and Future Directions

Metabolic diseases, such as obesity, type 2 diabetes, and non-alcoholic fatty liver disease, have emerged as major global health challenges. Recent research has revealed that the gut microbiome is closely associated with the development of these conditions. The Food and Drug Administration has recognized certain probiotic strains with therapeutic potential, classifying them as live biotherapeutic products (LBPs). LBPs, which are derived from naturally occurring microorganisms, may present an effective strategy for treating metabolic diseases by restoring gut microbiota balance and regulating metabolic functions. This review explores the development of LBPs specifically for metabolic disease treatments, covering every phase from strain identification, non-clinical and clinical trials, manufacturing and formulation to regulatory approval. Furthermore, it addresses the challenges involved in the commercialization of these therapies. By offering critical insights into the research and development of LBPs for metabolic disease treatment, this review aims to contribute to the progress of these promising therapies.

Purinergic Receptor Activation Protects Glomerular Microvasculature from Increased Mechanical Stress in Angiotensin II-Induced Hypertension: A Modeling Study

Angiotensin II (Ang II)-induced hypertension increases afferent (AA) and efferent (EA) arteriole resistances via the actions of Ang II on the AT1 receptor. In addition to the increased interstitial levels of Ang II, the increased arterial pressure increases interstitial ATP concentrations. In turn, ATP acts on the purinergic receptors P2X1 and P2X7 to constrict the AA, preventing increases in plasma flow and single-nephron GFR (SNGFR). While the hemodynamic effects of P2 activation have been characterized, the resulting increases in mechanical stresses (shear stress and circumferential hoop stress) on the glomerular microvasculature have not been quantified. A mathematical microvascular hemodynamic glomerular model was developed to simulate blood flow and plasma filtration in an anatomically accurate rat glomerular capillary network. AA and EA resistances were adjusted to match glomerular hemodynamic data for control, Ang II-induced hypertension, and P2X1-blocked conditions. A blockade of the purinergic receptors reduced both afferent and efferent resistances, maintaining glomerular pressure at hypertensive levels but increasing blood flow and sheer stress significantly. Because glomerular pressure was maintained, hoop stress barely changed. Our results indicate that the activation of the purinergic system protects the glomerular microvasculature from elevated shear stress caused by increased blood flow that would occur in the absence of purinergic stimulation.

Advancements in Microphysiological systems: Exploring organoids and organ-on-a-chip technologies in drug development -focus on pharmacokinetics related organs

This study explored the evolving landscape of Microphysiological Systems (MPS), with a focus on organoids and organ-on-a-chip (OoC) technologies, which are promising alternatives to animal testing in drug discovery. MPS technology offers in vitro models with high physiological relevance, simulating organ function for pharmacokinetic studies. Organoids composed of 3D cell aggregates and OoCs mimicking in vivo environments based on microfluidic platforms represent the forefront of MPS. This paper provides a comprehensive overview of their application in studying the gut, liver, and kidney and their challenges in becoming reliable alternatives to in vivo models. Although MPS technology is not yet fully comparable to in vivo systems, its continued development, aided by in silico, automation, and AI approaches, is anticipated to bring about further advancements. Collaboration across multiple disciplines and ongoing regulatory discussions will be crucial in driving MPS toward practical and ethical applications in biomedical research and drug development.

Droplet-based 3D bioprinting for drug delivery and screening

Recently, the conventional criterion of "one-size-fits-all" is not qualified for each individual patient, requiring precision medicine for enhanced therapeutic effects. Besides, drug screening is a high-cost and time-consuming process which requires innovative approaches to facilitate drug development rate. Benefiting from consistent technical advances in 3D bioprinting techniques, droplet-based 3D bioprinting techniques have been broadly utilized in pharmaceutics due to the noncontact printing mechanism and precise control on the deposition position of droplets. More specifically, cell-free/cell-laden bioinks which are deposited for the fabrication of drug carriers/3D tissue constructs have been broadly utilized for precise drug delivery and high throughput drug screening, respectively. This review summarizes the mechanism of various droplet-based 3D bioprinting techniques and the most up-to-date applications in drug delivery and screening and discusses the potential improvements of droplet-based 3D bioprinting techniques from both technical and material aspects. Through technical innovations, materials development, and the assistance from artificial intelligence, the formation process of drug carriers will be more stable and accurately controlled guaranteeing precise drug delivery. Meanwhile, the shape fidelity and uniformity of the printed tissue models will be significantly improved ensuring drug screening efficiency and efficacy.

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.

Utility of Induced Pluripotent Stem Cell-Based Microphysiological Systems for Drug Development and Testing

Microphysiological systems (MPS), i.e., miniaturized mimics of active biological systems, are considered resourceful tools for facilitating drug development. It presupposes that a microphysiological system can respond as organs and tissues in the human body to new drug candidates and that relevant cellular response can be monitored. If, or when, this is possible, microphysiological systems have the potential to support and accelerate the development and testing of new drug candidates.So far, the focus has been more on the design and fabrication of the microarchitecture of the MPS to recreate their cellular counterparts as closely and realistically as possible. Commercial MPS devices have been developed that focus on advanced technological design solutions, sometimes more than their actual biological functionality.This chapter discusses in brief terms the prerequisites for the design and construction of MPS devices in relation to their utility for drug development and testing in a more holistic manner. The use of induced pluripotent cells as a prime source for mimicking the in vivo conditions of diseased conditions is mainly considered. Existing limitations and needs are highlighted in relation to the space for improvements, based on recently published results.

One-Step Differentiation of Human-Induced Pluripotent Stem Cells into Podocytes

Within the glomerulus, podocytes are highly specialized visceral epithelial cells, that are part of the glomerular filtration barrier. Human podocyte cell culture is rather challenging for primary or immortalized cells, due to the non-proliferative state of the cells. In addition, de-differentiation is often observed rapidly. Hence, iPSC-derived podocytes offer an exciting alternative to culture podocyte-like cells from different donors over a prolonged time. Here we report an improved protocol of a simple and rapid one-step differentiation that drives iPSC into podocyte-like cells in 10 days and offers the possibility to transfer the podocyte-like cells into another plate format once.

Next-Generation Approaches for Biomedical Materials Evaluation: Microfluidics and Organ-on-a-Chip Technologies

Biological evaluation of biomedical materials faces constraints imposed by the limitations of traditional in vitro and animal experiments. Currently, miniaturized and biomimetic microfluidic technologies and organ-on-chip systems have garnered widespread attention in the field of drug development. However, their exploration in the context of biomedical material evaluation and medical device development remains relatively limited. In this review, a summary of existing biological evaluation methods, highlighting their respective advantages and drawbacks is provided. The application of microfluidic technologies in the evaluation of biomedical materials, emphasizing the potential of organ-on-chip systems as highly biomimetic in vitro models in material evaluation is then focused. Finally, the challenges and opportunities associated with utilizing organ-on-chip systems to evaluate biomedical materials in the field of material evaluation are discussed. In conclusion, the integration of advanced microfluidic technologies and organ-on-chip systems presents a potential paradigm shift in the biological assessment of biomedical materials, offering the prospective of more accurate and predictive in vitro models in the development of medical devices.

Fabrication of Biomimetic Cell Culture Membranes Using Robust and Reusable Nickel Micropillar Molds

In the practical application of organ-on-a-chip, mass production technology for flexible porous membranes is an essential element for mimicking the basement membrane of the body. Porous PDMS membrane is a promising material due to its high optical transparency, flexibility, and biocompatibility. However, the fabrication process is complex and costly. Even with soft lithography, a relatively straightforward method, there is a risk that the negative resist pillars used as molds peeling off from the substrate in mass production. In this study, we propose a novel mass production method for fabricating porous PDMS membranes using high-strength nickel (Ni) micropillars as molds by combining photolithography and electroforming technologies. The unibody structure of Ni micropillars ensures high reliability and provides a semi-permanent mold without degradation or detachment. We successfully fabricated two types of Ni micropillars and subsequently formed their corresponding porous PDMS membranes (D (diameter) = 8 μm, P (pitch) = 30 μm, and D = 10 μm, P = 20 μm). The porous PDMS membrane showed non-inferiority to the control group in terms of viability when cultured with human vascular endothelial cells. Furthermore, we showed that the porous PDMS membrane can be used to evaluate the vascular permeability of nanoparticles.

Transplantation of decellularized porcine kidney grafts repopulated with primary human cells demonstrates filtration function in pigs

BACKGROUND

End-stage renal disease is a growing global health issue, disproportionately impacting low- and middle-income countries. While kidney transplantation remains the best treatment for end-stage renal disease, access to this treatment modality is limited by chronic donor organ shortages. To address this critical need, we are developing transplantable bioengineered kidney grafts.

METHODS

Podocyte differentiation was achieved in adherent monoculture through Wnt and TGF-β inhibition with IWR-1 and SB431542, respectively. Podocytes along with endothelial cells were then used to recapitulate glomeruli within decellularized porcine kidney scaffolds to generate bioengineered kidneys grafts. These bioengineered kidney grafts were functionally assessed via normothermic perfusion which compared kidney grafts recellularized with only endothelial cells as a control to bi-culture kidney grafts comprised of endothelial cells and podocytes. Heterotopic implantation further tested bi-culture kidney graft function over 3 successive implant sessions with 1-2 grafts per session.

RESULTS

We demonstrate the ability to source primary human podocytes at scale. Decellularized porcine kidney grafts repopulated with podocytes and endothelial cells exhibit native glomerular structure and display blood filtration capabilities during normothermic perfusion testing. Extending these findings to a clinically relevant model, bioengineered kidneys produce urine with indices of filtration when heterotopically implanted in pigs.

CONCLUSIONS

Our results showcase a human-scale, transplantable bioengineered kidney capable of performing requisite filtration function. This study reinforces the possibility for the bioengineering of transplantable human kidneys, which could someday provide increased and more equitable access to kidney grafts for the treatment of end-stage renal disease.

"Periodontal ligament-on-chip" as a Novel Tool for Studies on the Physiology and Pathology of Periodontal Tissues

Teeth exert fundamental physiological functions, such as mastication and speech, and are a key feature of oral health that affects life quality. Teeth are anchored to the alveolar bone via the periodontal ligament, which provides stability to the teeth and absorbs mechanical stresses during mastication. Periodontal infection leads to periodontitis, a severe inflammation of the supporting soft tissues that ultimately cause tooth loss. Despite the pressing need of periodontal regeneration for improved oral care, efficient in vitro models of the periodontal tissues are still missing, thus hampering the development of novel, faster, and more effective therapy modalities. Herein, a novel "periodontal ligament (PDL)-on-chip" model that integrates patient-derived periodontal ligament cells (PDLCs) and endothelial cells is introduced. This microfluidic platform provides optimal conditions for the formation of extensive and perfusable vascular networks. Furthermore, PDLCs elicit blood vessels' development and maturation while establishing close contacts with the endothelial cells. Potential applications for inflammatory periodontal diseases are also successfully displayed in the "PDL-on-chip" by stimulating inflammation and detecting inflammatory cytokines. This work offers a cornerstone for more complex and specialized microfluidic dental models, which are necessary to unravel complex oral diseases that affect individuals' general health that go beyond the field of dentistry.

Design and simulation of a microfluidics-based artificial glomerular ultrafiltration unit to reduce cell-induced fouling

BACKGROUND

The microfluidic-based Glomerulus-on-Chips (GoC) are mostly cell based, that is, 3D cell culture techniques are used to culture glomerular cells in order to mimic glomerular ultrafiltration. These chips require high maintenance to keep cell viability intact. There have been some approaches to build non-cell-based GoCs but many of these approaches have the drawback of membrane fouling. This article presents a structural design and simulation study of a dialysate free microfluidic channel for replicating the function of the human glomerular filtration barrier. The key advancement of the current work is addressing the fouling issue by combining a pre-filter to eliminate cellular components and performing filtration on the blood plasma.

METHODS

The Laminar Flow Mixture Model in COMSOL Multiphysics 5.6 has been utilized to simulate the behavior of blood flow in the microchannels. The geometrical effect of microchannels on the separation of the filtrate was investigated. The velocity at the inlet of the microchannel and pore size of the filtration membrane are varied to see the change in outflow and filtration fraction.

RESULTS

The efficiency of the device is calculated in terms of the filtration fraction (FF%) formed. Simulation results show that the filtrate obtained is ~20% of the plasma flow rate in the channel, which resembles the glomerular filtration fraction.

CONCLUSION

Given that it is not dependent on the functionality of grown cells, the proposed device is anticipated to have a longer lifespan due to its non-cell-based design. The device's cost can be reduced by avoiding cell cultivation inside of it. It can be integrated as a glomerular functional unit with other units of kidney model to build a fully developed artificial kidney.

Micro- and nano-fibers for organ-on-a-chip: Construction, applications, and prospects

Organ-on-a-chip, an in vitro biomimetic microsystem that enables precise regulation and real-time observation of the cell microenvironment, has the potential to become a powerful platform for recapitulating the real microenvironment of organs in vitro. Microenvironmental factors, such as living cells, three-dimensional (3D) culture, tissue-tissue interfaces, and biomechanical factors, are important cues in the construction of biomimetic microsystems. It is important to provide an appropriate 3D culture environment for living cells to grow. Fibers, particularly microfibers and nanofibers, can provide a suitable 3D culture environment for living cells via surface adhesion or internal loading. In addition, fibers can further expand their applications in tissue engineering and biomedical research by being assembled at a higher level in various ways to create functional 3D tissues or organs with more complex structures. The use of fiber to construct an organ-on-a-chip, whether as a 3D scaffold for cell culture or to more closely mimic real tissues/organs, will introduce new ideas and strategies for developing novel organ-on-a-chip systems. Based on this context, this review summarizes the research progress in the construction and applications of micro/nanofibers for organ-on-a-chip systems. It outlines the preparation methods and material selections for micro/nanofibers and provides a detailed overview of their respective strategies for cell 3D culture and organ-on-a-chip construction. This review also highlights the main research findings and applications of micro/nanofiber in this field, which have significant implications for future practice, and finally concludes by examining potential directions for future development.

A human stem cell-derived model reveals pathologic extracellular matrix remodeling in diabetic podocyte injury

Diabetic nephropathy results from chronic (or uncontrolled) hyperglycemia and is the leading cause of kidney failure. The kidney's glomerular podocytes are highly susceptible to diabetic injury and subsequent non-reversible degeneration. We generated a human induced pluripotent stem (iPS) cell-derived model of diabetic podocytopathy to investigate disease pathogenesis and progression. The model recapitulated hallmarks of podocytopathy that precede proteinuria including retraction of foot processes and podocytopenia (detachment from the extracellular matrix (ECM)). Moreover, hyperglycemia-induced injury to podocytes exacerbated remodeling of the ECM. Specifically, mature podocytes aberrantly increased expression and excessively deposited collagen (IV)α1α1α2 that is normally abundant in the embryonic glomerulus. This collagen (IV) imbalance coincided with dysregulation of lineage-specific proteins, structural abnormalities of the ECM, and podocytopenia - a mechanism not shared with endothelium and is distinct from drug-induced injury. Intriguingly, repopulation of hyperglycemia-injured podocytes on decellularized ECM scaffolds isolated from healthy podocytes attenuated the loss of synaptopodin (a mechanosensitive protein associated with podocyte health). These results demonstrate that human iPS cell-derived podocytes can facilitate in vitro studies to uncover the mechanisms of chronic hyperglycemia and ECM remodeling and guide disease target identification.

Epigenetics of Hypertensive Nephropathy

Hypertensive nephropathy (HN) is a leading cause of chronic kidney disease (CKD) and end-stage renal disease (ESRD), contributing to significant morbidity, mortality, and rising healthcare costs. In this review article, we explore the role of epigenetic mechanisms in HN progression and their potential therapeutic implications. We begin by examining key epigenetic modifications-DNA methylation, histone modifications, and non-coding RNAs-observed in kidney disease. Next, we discuss the underlying pathophysiology of HN and highlight current in vitro and in vivo models used to study the condition. Finally, we compare various types of HN-induced renal injury and their associated epigenetic mechanisms with those observed in other kidney injury models, drawing inferences on potential epigenetic therapies for HN. The information gathered in this work indicate that epigenetic mechanisms can drive the progression of HN by regulating key molecular signaling pathways involved in renal damage and fibrosis. The limitations of Renin-Angiotensin-Aldosterone System (RAAS) inhibitors underscore the need for alternative treatments targeting epigenetic pathways. This review emphasizes the importance of further research into the epigenetic regulation of HN to develop more effective therapies and preventive strategies. Identifying novel epigenetic markers could provide new therapeutic opportunities for managing CKD and reducing the burden of ESRD.

Mechanosensitive Differentiation of Human iPS Cell-Derived Podocytes

Stem cell fate decisions, including proliferation, differentiation, morphological changes, and viability, are impacted by microenvironmental cues such as physical and biochemical signals. However, the specific impact of matrix elasticity on kidney cell development and function remains less understood due to the lack of models that can closely recapitulate human kidney biology. An established protocol to differentiate podocytes from human-induced pluripotent stem (iPS) cells provides a promising avenue to elucidate the role of matrix elasticity in kidney tissue development and lineage determination. In this study, we synthesized polyacrylamide hydrogels with different stiffnesses and investigated their ability to promote podocyte differentiation and biomolecular characteristics. We found that 3 kPa and 10 kPa hydrogels significantly support the adhesion, differentiation, and viability of podocytes. Differentiating podocytes on a more compliant (0.7 kPa) hydrogel resulted in significant cell loss and detachment. Further investigation of the mechanosensitive proteins yes-associated protein (YAP) and synaptopodin revealed nuanced molecular distinctions in cellular responses to matrix elasticity that may otherwise be overlooked if morphology and cell spreading alone were used as the primary metric for selecting matrices for podocyte differentiation. Specifically, hydrogels with kidney-like rigidities outperformed traditional tissue culture plates at modulating the molecular-level expression of active mechanosensitive proteins critical for podocyte health and function. These findings could guide the development of physiologically relevant platforms for kidney tissue engineering, disease modeling, and mechanistic studies of organ physiology and pathophysiology. Such advances are critical for realizing the full potential of in vitro platforms in accurately predicting human biological responses.

Engineering a Biomimetic Glomerular Filtration Barrier: Coculturing Endothelial Podocytes on Kidney ECM-Bacterial Cellulose Membrane Hybrid

A novel avenue for advancing our understanding of kidney disease mechanisms and developing targeted therapeutics lies in overcoming the limitations of the existing in vitro models. Traditional animal models, while useful, do not fully capture the intricacies of human kidney physiology and pathophysiology. Tissue engineering offers a promising solution, yet current models often fall short in replicating the complex microarchitecture and biochemical milieu of the kidney. To address this challenge, we propose the development of a sophisticated in vitro glomerular filtration barrier (GFB) utilizing advanced biomaterials and a kidney decellularized extracellular matrix (kdECM). In our approach, we employ a bacterial cellulose membrane (BC) as a scaffold, providing a robust framework for cell growth and interaction. Coating this scaffold with kdECM hydrogel derived from caprine kidney tissue via a detergent-free decellularization method ensures the preservation of vital extracellular matrix proteins crucial for cellular compatibility and signaling. Our engineered GFB not only supports the growth of endothelial and podocyte cells but also exhibits the presence of key markers such as CD31 and nephrin, indicating successful cellular integration. Furthermore, the expression of collagen IV, an essential extracellular matrix (ECM) protein, validates the fidelity of our model in simulating cellular interactions within a kdECM matrix. Additionally, we assessed the filtration efficiency of the developed GFB model using albumin, a standard protein, to evaluate its performance under conditions that closely mimic the native physiological environment. This innovative approach, which faithfully recapitulates the native microenvironment of the glomerulus, holds immense promise for elucidating kidney disease mechanisms, conducting permeability studies, and advancing personalized therapeutic strategies. By leveraging cutting-edge biomaterials and tissue-specific coculture technology, this study can be further extended to develop GFB for the treatment of renal diseases, ultimately improving patient outcomes and quality of life.

Progress and breakthroughs in human kidney organoid research

The three-dimensional (3D) kidney organoid is a breakthrough model for recapitulating renal morphology and function in vitro, which is grown from stem cells and resembles mammalian kidney organogenesis. Currently, protocols for cultivating this model from induced pluripotent stem cells (iPSCs) and patient-derived adult stem cells (ASCs) have been widely reported. In recent years, scientists have focused on combining cutting-edge bioengineering and bioinformatics technologies to improve the developmental accuracy of kidney organoids and achieve high-throughput experimentation. As a remarkable tool for mechanistic research of the renal system, kidney organoid has both potential and challenges. In this review, we have described the evolution of kidney organoid establishment methods and highlighted the latest progress leading to a more sophisticated kidney transformation research model. Finally, we have summarized the main applications of renal organoids in exploring kidney disease.

Unleashing the power of biomaterials to enhance organoid differentiation and function

Biomaterials are revolutionizing organoid development by offering tunable platforms that provide instructive cues, which enhance cell fate transitions, tissue-level functions and reproducibility. These advances are crucial for harnessing the translational potential of organoids.

Complexin vitromodels positioned for impact to drug testing in pharma: a review

Recent years have seen the creation and popularization of various complexin vitromodels (CIVMs), such as organoids and organs-on-chip, as a technology with the potential to reduce animal usage in pharma while also enhancing our ability to create safe and efficacious drugs for patients. Public awareness of CIVMs has increased, in part, due to the recent passage of the FDA Modernization Act 2.0. This visibility is expected to spur deeper investment in and adoption of such models. Thus, end-users and model developers alike require a framework to both understand the readiness of current models to enter the drug development process, and to assess upcoming models for the same. This review presents such a framework for model selection based on comparative -omics data (which we term model-omics), and metrics for qualification of specific test assays that a model may support that we term context-of-use (COU) assays. We surveyed existing healthy tissue models and assays for ten drug development-critical organs of the body, and provide evaluations of readiness and suggestions for improving model-omics and COU assays for each. In whole, this review comes from a pharma perspective, and seeks to provide an evaluation of where CIVMs are poised for maximum impact in the drug development process, and a roadmap for realizing that potential.

Engineered human iPS cell models reveal altered podocytogenesis and glomerular capillary wall in CHD-associated SMAD2 mutations

Early developmental programming involves extensive cell lineage diversification through shared molecular signaling networks. Clinical observations of congenital heart disease (CHD) patients carrying SMAD2 genetic variants revealed correlations with multi-organ impairments at the developmental and functional levels. For example, many CHD patients present with glomerulosclerosis, periglomerular fibrosis, and albuminuria. Still, it remains largely unknown whether SMAD2 variants associated with CHD can directly alter kidney cell fate, tissue patterning, and organ-level function. To address this question, we engineered human iPS cells (iPSCs) and organ-on-a-chip systems to uncover the role of pathogenic SMAD2 variants in kidney podocytogenesis. Our results show that abrogation of SMAD2 causes altered patterning of the mesoderm and intermediate mesoderm (IM) cell lineages, which give rise to nearly all kidney cell types. Upon further differentiation of IM cells, the mutant podocytes failed to develop arborizations and interdigitations. A reconstituted glomerulus-on-a-chip platform exhibited significant proteinuria as clinically observed in glomerulopathies. This study implicates CHD-associated SMAD2 mutations in kidney tissue malformation and provides opportunities for therapeutic discovery in the future.

Gene Delivery From Granular Scaffolds for Tunable Biologics Manufacturing

The understanding of the molecular basis for disease has generated a myriad of therapeutic biologics, including therapeutic proteins, antibodies, and viruses. However, the promise that biologics can resolve currently incurable diseases hinges in their manufacturability. These therapeutics require that their genetic material be introduced to mammalian cells such that the cell machinery can manufacture the biological components. These are then purified, validated, and packaged. Most manufacturing uses batch processes that collect the biologic a few days following genetic modification, due to toxicity or difficulty in separating product from cells in a continuous operation, limiting the amount of biologic that can be produced and resulting in yearlong backlogs. Here, a scaffold-based approach for continuous biologic manufacturing is presented, with sustained production of active antibodies and viruses for 30 days. The use of scaffold-based biologic production enabled perfusion-based bioreactors to be used, which can be incorporated into a fully continuous process.

An Integrated and Modular Compartmentalized Microfluidic System with Tunable Electrospun Porous Membranes for Epithelialized Organs-on-a-Chip

A modular and 3D compartmentalized microfluidic system with electrospun porous membranes (PMs) for epithelialized organ-on-a-chip systems is presented. Our novel approach involves direct deposition of polymer nanofibers onto a patterned poly(methyl methacrylate) (PMMA) substrate using electrospinning, resulting in an integrated PM within the microfluidic chip. The in situ deposition of the PM eliminates the need for additional assembly processes. To demonstrate the high throughput membrane integration capability of our approach, we successfully deposited nanofibers onto various chip designs with complex microfluidic planar structures and expanded dimensions. We characterized and tested the fully PMMA chip by growing an epithelial monolayer using the Caco-2 cell line to study drug permeability. A comprehensive analysis of the bulk and surface properties of the membrane's fibers made of PMMA and polystyrene (PS) was conducted to determine the polymer with the best performance for cell culture and drug transport applications. The PMMA-based membrane, with a PMMA/PVP ratio of 5:1, allowed for the fabrication of a uniform membrane structure along the aligned nanofibers. By modulating the fiber diameter and total thickness of the membrane, we could adjust the membrane's porosity for specific cell culture applications. The PMMA-PVP nanofibers exhibited a low polydispersity index value, indicating monodispersed nanofibers and a more homogeneous and uniform fiber network. Both types of membranes demonstrated excellent mechanical integrity under medium perfusion flow rates. However, the PMMA-PVP composition offered a tailored porous structure with modulable porosity based on the fiber diameter and thickness. Our developed platform enables dynamic in vitro modeling of the epithelial barrier and has applications in drug transport and in vitro microphysiological systems.

Mesenchymal Stem Cell and Hematopoietic Stem and Progenitor Cell Co-Culture in a Bone-Marrow-on-a-Chip Device toward the Generation and Maintenance of the Hematopoietic Niche

Bone marrow has raised a great deal of scientific interest, since it is responsible for the vital process of hematopoiesis and is affiliated with many normal and pathological conditions of the human body. In recent years, organs-on-chips (OoCs) have emerged as the epitome of biomimetic systems, combining the advantages of microfluidic technology with cellular biology to surpass conventional 2D/3D cell culture techniques and animal testing. Bone-marrow-on-a-chip (BMoC) devices are usually focused only on the maintenance of the hematopoietic niche; otherwise, they incorporate at least three types of cells for on-chip generation. We, thereby, introduce a BMoC device that aspires to the purely in vitro generation and maintenance of the hematopoietic niche, using solely mesenchymal stem cells (MSCs) and hematopoietic stem and progenitor cells (HSPCs), and relying on the spontaneous formation of the niche without the inclusion of gels or scaffolds. The fabrication process of this poly(dimethylsiloxane) (PDMS)-based device, based on replica molding, is presented, and two membranes, a perforated, in-house-fabricated PDMS membrane and a commercial poly(ethylene terephthalate) (PET) one, were tested and their performances were compared. The device was submerged in a culture dish filled with medium for passive perfusion via diffusion in order to prevent on-chip bubble accumulation. The passively perfused BMoC device, having incorporated a commercial poly(ethylene terephthalate) (PET) membrane, allows for a sustainable MSC and HSPC co-culture and proliferation for three days, a promising indication for the future creation of a hematopoietic bone marrow organoid.

Reconstitution of human tissue barrier function for precision and personalized medicine

Tissue barriers in a body, well known as tissue-to-tissue interfaces represented by endothelium of the blood vessels or epithelium of organs, are essential for maintaining physiological homeostasis by regulating molecular and cellular transports. It is crucial for predicting drug response to understand physiology of tissue barriers through which drugs are absorbed, distributed, metabolized and excreted. Since the FDA Modernization Act 2.0, which prompts the inception of alternative technologies for animal models, tissue barrier chips, one of the applications of organ-on-a-chip or microphysiological system (MPS), have only recently been utilized in the context of drug development. Recent advancements in stem cell technology have brightened the prospects for the application of tissue barrier chips in personalized medicine. In past decade, designing and engineering these microfluidic devices, and demonstrating the ability to reconstitute tissue functions were main focus of this field. However, the field is now advancing to the next level of challenges: validating their utility in drug evaluation and creating personalized models using patient-derived cells. In this review, we briefly introduce key design parameters to develop functional tissue barrier chip, explore the remarkable recent progress in the field of tissue barrier chips and discuss future perspectives on realizing personalized medicine through the utilization of tissue barrier chips.

A perfusable, vascularized kidney organoid-on-chip model

The ability to controllably perfuse kidney organoids would better recapitulate the native tissue microenvironment for applications ranging from drug testing to therapeutic use. Here, we report a perfusable, vascularized kidney organoid on chip model composed of two individually addressable channels embedded in an extracellular matrix (ECM). The channels are respectively seeded with kidney organoids and human umbilical vein endothelial cells that form a confluent endothelium (macrovessel). During perfusion, endogenous endothelial cells present within the kidney organoids migrate through the ECM towards the macrovessel, where they form lumen-on-lumen anastomoses that are supported by stromal-like cells. Once micro-macrovessel integration is achieved, we introduced fluorescently labeled dextran of varying molecular weight and red blood cells into the macrovessel, which are transported through the microvascular network to the glomerular epithelia within the kidney organoids. Our approach for achieving controlled organoid perfusion opens new avenues for generating other perfused human tissues.

Kidney Disease Modeling with Organoids and Organs-on-Chips

Kidney disease is a global health crisis affecting more than 850 million people worldwide. In the United States, annual Medicare expenditures for kidney disease and organ failure exceed $81 billion. Efforts to develop targeted therapeutics are limited by a poor understanding of the molecular mechanisms underlying human kidney disease onset and progression. Additionally, 90% of drug candidates fail in human clinical trials, often due to toxicity and efficacy not accurately predicted in animal models. The advent of ex vivo kidney models, such as those engineered from induced pluripotent stem (iPS) cells and organ-on-a-chip (organ-chip) systems, has garnered considerable interest owing to their ability to more accurately model tissue development and patient-specific responses and drug toxicity. This review describes recent advances in developing kidney organoids and organ-chips by harnessing iPS cell biology to model human-specific kidney functions and disease states. We also discuss challenges that must be overcome to realize the potential of organoids and organ-chips as dynamic and functional conduits of the human kidney. Achieving these technological advances could revolutionize personalized medicine applications and therapeutic discovery for kidney disease.

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.

Current trends and research topics regarding organoids: A bibliometric analysis of global research from 2000 to 2023

The use of animal models for biological experiments is no longer sufficient for research related to human life and disease. The development of organ tissues has replaced animal models by mimicking the structure, function, development and homeostasis of natural organs. This provides more opportunities to study human diseases such as cancer, infectious diseases and genetic disorders. In this study, bibliometric methods were used to analyze organoid-related articles published over the last 20+ years to identify emerging trends and frontiers in organoid research. A total of 13,143 articles from 4125 institutions in 86 countries or regions were included in the analysis. The number of papers increased steadily over the 20-year period. The United States was the leading country in terms of number of papers and citations. Harvard Medical School had the highest number of papers published. Keyword analysis revealed research trends and focus areas such as organ tissues, stem cells, 3D culture and tissue engineering. In conclusion, this study used bibliometric and visualization methods to explore the field of organoid research and found that organ tissues are receiving increasing attention in areas such as cancer, drug discovery, personalized medicine, genetic disease modelling and gene repair, making them a current research hotspot and a future research trend.

Microfluidics as a promising technology for personalized medicine

Introduction

Due to the recent advances in biomedicine and the increasing understanding of the molecular mechanism of diseases, healthcare approaches have tended towards preventive and personalized medicine. Consequently, in recent decades, the utilization of interdisciplinary technologies such as microfluidic systems had a significant increase to provide more accurate high throughput diagnostic/therapeutic methods.

Methods

In this article, we will review a summary of innovations in microfluidic technologies toward improving personalized biomolecular diagnostics, drug screening, and therapeutic strategies.

Results

Microfluidic systems by providing a controllable space for fluid flow, three-dimensional growth of cells, and miniaturization of molecular experiments are useful tools in the field of personalization of health and treatment. These conditions have enabled the potential to carry out studies like; disease modeling, drug screening, and improving the accuracy of diagnostic methods.

Conclusion

Microfluidic devices have become promising point-of-care (POC) and personalized medicine instruments due to their ability to perform diagnostic tests with small sample volumes, cost reduction, high resolution, and automation.

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.

An ultrathin membrane mediates tissue-specific morphogenesis and barrier function in a human kidney chip

Organ-on-chip (OOC) systems are revolutionizing tissue engineering by providing dynamic models of tissue structure, organ-level function, and disease phenotypes using human cells. However, nonbiological components of OOC devices often limit the recapitulation of in vivo-like tissue-tissue cross-talk and morphogenesis. Here, we engineered a kidney glomerulus-on-a-chip that recapitulates glomerular morphogenesis and barrier function using a biomimetic ultrathin membrane and human-induced pluripotent stem cells. The resulting chip comprised a proximate epithelial-endothelial tissue interface, which reconstituted the selective molecular filtration function of healthy and diseased kidneys. In addition, fenestrated endothelium was successfully induced from human pluripotent stem cells in an OOC device, through in vivo-like paracrine signaling across the ultrathin membrane. Thus, this device provides a dynamic tissue engineering platform for modeling human kidney-specific morphogenesis and function, enabling mechanistic studies of stem cell differentiation, organ physiology, and pathophysiology.

Optimizing Nodal, Wnt and BMP signaling pathways for robust and efficient differentiation of human induced pluripotent stem cells to intermediate mesoderm cells

Several differentiation protocols have enabled the generation of intermediate mesoderm (IM)-derived cells from human pluripotent stem cells (hPSC). However, the substantial variability between existing protocols for generating IM cells compromises their efficiency, reproducibility, and overall success, potentially hindering the utility of urogenital system organoids. Here, we examined the role of high levels of Nodal signaling and BMP activity, as well as WNT signaling in the specification of IM cells derived from a UCSD167i-99-1 human induced pluripotent stem cells (hiPSC) line. We demonstrate that precise modulation of WNT and BMP signaling significantly enhances IM differentiation efficiency. Treatment of hPSC with 3 μM CHIR99021 induced TBXT+/MIXL1+ mesoderm progenitor (MP) cells after 48 h of differentiation. Further treatment with a combination of 3 μM CHIR99021 and 4 ng/mL BMP4 resulted in the generation of OSR1+/GATA3+/PAX2+ IM cells within a subsequent 48 h period. Molecular characterization of differentiated cells was confirmed through immunofluorescence staining and RT-qPCR. Hence, this study establishes a consistent and reproducible protocol for differentiating hiPSC into IM cells that faithfully recapitulates the molecular signatures of IM development. This protocol holds promise for improving the success of protocols designed to generate urogenital system organoids in vitro, with potential applications in regenerative medicine, drug discovery, and disease modeling.

Role of biophysics and mechanobiology in podocyte physiology

Podocytes form the backbone of the glomerular filtration barrier and are exposed to various mechanical forces throughout the lifetime of an individual. The highly dynamic biomechanical environment of the glomerular capillaries greatly influences the cell biology of podocytes and their pathophysiology. Throughout the past two decades, a holistic picture of podocyte cell biology has emerged, highlighting mechanobiological signalling pathways, cytoskeletal dynamics and cellular adhesion as key determinants of biomechanical resilience in podocytes. This biomechanical resilience is essential for the physiological function of podocytes, including the formation and maintenance of the glomerular filtration barrier. Podocytes integrate diverse biomechanical stimuli from their environment and adapt their biophysical properties accordingly. However, perturbations in biomechanical cues or the underlying podocyte mechanobiology can lead to glomerular dysfunction with severe clinical consequences, including proteinuria and glomerulosclerosis. As our mechanistic understanding of podocyte mechanobiology and its role in the pathogenesis of glomerular disease increases, new targets for podocyte-specific therapeutics will emerge. Treating glomerular diseases by targeting podocyte mechanobiology might improve therapeutic precision and efficacy, with potential to reduce the burden of chronic kidney disease on individuals and health-care systems alike.

Revolutionizing renal research: The future of kidney-on-a-chip in biotechnology

In vitro models of kidneys have limited effectiveness owing to the complex structure and functions of the kidney when compared with other organs. Therefore many renal function evaluations are currently being carried out through animal experiments. In contrast, efforts are being made to apply biomimetic systems, such as organ-on-a-chip, which is based on microfluidic device technology, to serve as an in vitro model for the kidney. These systems aimed to recreate a physiological cultivation environment. This review has provided an overview of organ-on-a-chip research focused on glomeruli and tubules as in vitro models for the kidney and discusses future prospects.

Induced pluripotent stem cells (iPSCs): molecular mechanisms of induction and applications

The induced pluripotent stem cell (iPSC) technology has transformed in vitro research and holds great promise to advance regenerative medicine. iPSCs have the capacity for an almost unlimited expansion, are amenable to genetic engineering, and can be differentiated into most somatic cell types. iPSCs have been widely applied to model human development and diseases, perform drug screening, and develop cell therapies. In this review, we outline key developments in the iPSC field and highlight the immense versatility of the iPSC technology for in vitro modeling and therapeutic applications. We begin by discussing the pivotal discoveries that revealed the potential of a somatic cell nucleus for reprogramming and led to successful generation of iPSCs. We consider the molecular mechanisms and dynamics of somatic cell reprogramming as well as the numerous methods available to induce pluripotency. Subsequently, we discuss various iPSC-based cellular models, from mono-cultures of a single cell type to complex three-dimensional organoids, and how these models can be applied to elucidate the mechanisms of human development and diseases. We use examples of neurological disorders, coronavirus disease 2019 (COVID-19), and cancer to highlight the diversity of disease-specific phenotypes that can be modeled using iPSC-derived cells. We also consider how iPSC-derived cellular models can be used in high-throughput drug screening and drug toxicity studies. Finally, we discuss the process of developing autologous and allogeneic iPSC-based cell therapies and their potential to alleviate human diseases.

Advances in the Model Structure of In Vitro Vascularized Organ-on-a-Chip

Microvasculature plays a crucial role in human physiology and is closely related to various human diseases. Building in vitro vascular networks is essential for studying vascular tissue behavior with repeatable morphology and signaling conditions. Engineered 3D microvascular network models, developed through advanced microfluidic-based techniques, provide accurate and reproducible platforms for studying the microvasculature in vitro, an essential component for designing organ-on-chips to achieve greater biological relevance. By optimizing the microstructure of microfluidic devices to closely mimic the in vivo microenvironment, organ-specific models with healthy and pathological microvascular tissues can be created. This review summarizes recent advancements in in vitro strategies for constructing microvascular tissue and microfluidic devices. It discusses the static vascularization chips' classification, structural characteristics, and the various techniques used to build them: growing blood vessels on chips can be either static or dynamic, and in vitro blood vessels can be grown in microchannels, elastic membranes, and hydrogels. Finally, the paper discusses the application scenarios and key technical issues of existing vascularization chips. It also explores the potential for a novel organoid chip vascularization approach that combines organoids and organ chips to generate better vascularization chips.

Advancing Organoid Engineering for Tissue Regeneration and Biofunctional Reconstruction

Tissue damage and functional abnormalities in organs have become a considerable clinical challenge. Organoids are often applied as disease models and in drug discovery and screening. Indeed, several studies have shown that organoids are an important strategy for achieving tissue repair and biofunction reconstruction. In contrast to established stem cell therapies, organoids have high clinical relevance. However, conventional approaches have limited the application of organoids in clinical regenerative medicine. Engineered organoids might have the capacity to overcome these challenges. Bioengineering-a multidisciplinary field that applies engineering principles to biomedicine-has bridged the gap between engineering and medicine to promote human health. More specifically, bioengineering principles have been applied to organoids to accelerate their clinical translation. In this review, beginning with the basic concepts of organoids, we describe strategies for cultivating engineered organoids and discuss the multiple engineering modes to create conditions for breakthroughs in organoid research. Subsequently, studies on the application of engineered organoids in biofunction reconstruction and tissue repair are presented. Finally, we highlight the limitations and challenges hindering the utilization of engineered organoids in clinical applications. Future research will focus on cultivating engineered organoids using advanced bioengineering tools for personalized tissue repair and biofunction reconstruction.

Lab on chip for testing of repurposed drugs

The lab-on-chip technique broadly comprises of microfluidics and aims to progress multidimensionally by changing the outlook of medicine and pharmaceuticals as it finds it roots in miniaturization. Moreover, microfluidics facilitates precise physiological simulation and possesses biological system-mimicking capabilities for drug development and repurposing. Thus, organs on chip could pave a revolutionary pathway in the field of drug development and repurposing by reducing animal testing and improving drug repurposing.

Advancements in therapeutic development: kidney organoids and organs on a chip

The use of animal models in therapeutic development has long been the standard practice. However, ethical concerns and the inherent species differences have prompted a reevaluation of the experimental approach in human disease studies. The urgent need for alternative model systems that better mimic human pathophysiology has led to the emergence of organoids, innovative in vitro models, to simulate human organs in vitro. These organoids have gained widespread acceptance in disease models and drug development research. In this mini review, we explore the recent strides made in kidney organoid differentiation and highlight the synergistic potential of incorporating organ-on-chip systems. The emergent use of microfluidic devices reveals the importance of fluid flow in the maturation of kidney organoids and helps decipher pathomechanisms in kidney diseases. Recent research has uncovered their potential applications across a wide spectrum of kidney research areas, including hemodynamic forces at stake in kidney health and disease, immune cell infiltration, or drug delivery and toxicity. This convergence of cutting-edge technologies not only holds promise for expediting therapeutic development but also reflects an acknowledgment of the need to embrace innovative and more human-centric research models.