Merging organoid and organ-on-a-chip technology to generate complex multi-layer tissue models in a human retina-on-a-chip platform

Single-cell RNA sequencing in the study of human retinal organoids

Single-cell RNA sequencing (scRNA-seq) has transformed the study of retinal development and diseases by enabling a detailed analysis of cellular diversity within retinal organoids (ROs). ROs generated from pluripotent stem cells mimic the essential characteristics of the human retina and provide a valuable in vitro model for investigating retinal development, cell interactions, and disease mechanisms. This review summarizes the application of scRNA-seq on RO research, emphasizing its capacity to identify distinct cell populations, uncover developmental trajectories, and reveal the molecular signatures of retinal diseases. scRNA-seq provides new insights into retinal neurogenesis, cellular diversity, and the pathophysiology of retinal degenerative diseases. This technology has enabled the identification of novel biomarkers and potential therapeutic targets. Integrating scRNA-seq with other technologies, such as spatial transcriptomics and CRISPR-based screening, can further deepen our understanding of retinal biology and improve treatment strategies.

Cartilage repair: unleashing PRP's potential in organoid models

Platelet-rich plasma (PRP) has emerged as a promising biological therapy in regenerative medicine due to its high concentration of growth factors and cytokines, which promote tissue healing and regeneration. In recent years, its application in cartilage tissue engineering has garnered significant attention. This study explores the synergistic interaction between PRP and cartilage organoids, a novel three-dimensional in vitro culture system that closely mimics the structural and functional properties of native cartilage. Cartilage organoids serve as a physiologically relevant model for studying cartilage development, disease progression, and regeneration. By integrating PRP with cartilage organoids, this review aims to enhance chondrogenesis, extracellular matrix synthesis, and cellular proliferation within the organoids. Emerging evidence suggests that PRP supplementation significantly improves chondrocyte viability, growth, and differentiation in cartilage organoids, thereby accelerating their maturation. This combination holds great potential for advancing cartilage repair strategies, providing a robust platform for preclinical studies, and paving the way for innovative therapeutic approaches for cartilage-related injuries and degenerative diseases. These key aspects-chondrogenesis, matrix synthesis, and cellular proliferation-were specifically selected due to their fundamental roles in cartilage tissue engineering and regeneration. Chondrogenesis is crucial for chondrocyte differentiation and maintenance, matrix synthesis ensures the structural integrity and functional properties of regenerated cartilage, and cellular proliferation supports tissue viability and repair. Addressing these factors is essential, as current cartilage regeneration strategies often suffer from limited long-term efficacy and inadequate extracellular matrix production. By elucidating the synergistic effects of PRP and cartilage organoids in these areas, this study seeks to bridge existing knowledge gaps and provide valuable insights for improving regenerative approaches in clinical applications, particularly for osteoarthritis and cartilage defects.

Generation of Neural Organoids and Their Application in Disease Modeling and Regenerative Medicine

The complexity and precision of the human nervous system have posed significant challenges for researchers seeking suitable models to elucidate refractory neural disorders. Traditional approaches, including monolayer cell cultures and animal models, often fail to replicate the intricacies of human neural tissue. The advent of organoid technology derived from stem cells has addressed many of these limitations, providing highly representative platforms for studying the structure and function of the human embryonic brain and spinal cord. Researchers have induced neural organoids with regional characteristics by mimicking morphogen gradients in neural development. Recent advancements have demonstrated the utility of neural organoids in disease modeling, offering insights into the pathophysiology of various neural disorders, as well as in the field of neural regeneration. Developmental defects in neural organoids due to the lack of microglia or vascular systems are addressed. In addition to induction methods, microfluidics is used to simulate the dynamic physiological environment; bio-manufacturing technologies are employed to regulate physical signaling and shape the structure of complex organs. These technologies further expand the construction strategies and application scope of neural organoids. With the emergence of new material paradigms and advances in AI, new possibilities in the realm of neural organoids are witnessed.

Organoids-on-Chips Technology: Unveiling New Perspectives in Rare-Disease Research

The scarcity of robust models and therapeutic options for rare diseases continues to hamper their preclinical investigation. Traditional animal models and two-dimensional cell cultures are limited in their ability to replicate human heredity-associated traits and complex pathological features. Organoids-on-a-chip approaches open up new frontiers in rare-disease research via the integration of organ chips and organoid technology. This integrative strategy offers immense opportunities for the mimicry of disease-related traits, the clarification of the mechanisms underlying disease, and the prediction of treatment responses in a highly human-related manner. This forward-looking perspective suggests organoids on chips are transformative tools for parsing rare-disease pathogenesis, accelerating therapeutic discovery, and bridging the gap between basic research and precision medicine.

The advancements in precision medicine for Leber congenital amaurosis: Breakthroughs from genetic diagnosis to therapy

Leber congenital amaurosis (LCA) is a hereditary retinal disease, typically manifesting as severe vision impairment in infancy. With the advancement of precision medicine, genetic diagnosis and targeted therapies offer new hope for LCA patients, significantly improving both diagnostic accuracy and therapeutic efficacy. We summarize the epidemiological characteristics, clinical manifestations, and molecular genetics underlying LCA. It also highlights recent developments in precision treatment strategies, including gene replacement therapy, CRISPR/Cas9-mediated gene editing, and antisense oligonucleotide therapies. In addition, we discuss the applications of induced pluripotent stem cells and retinal organoids in LCA treatment research. Furthermore, we explore preventive strategies and future treatment directions for LCA, including the development of novel gene therapy vectors, the optimization of combinatorial treatment strategies, and the formulation of personalized treatment approaches. These advancements hold significant potential to offer improved treatment options and enhance the quality of life for LCA patients.

A Hydrogel-Based Multiplex Coculture Platform for Retinal Component Cells

There is growing interest in generating in vitro models of tissues and tissue-related diseases to mimic normal tissue organization and pathogenesis for different purposes. The retina is a highly complex multicellular tissue where the organization of the cellular components relative to each other is critical for retinal function. Many retinopathies arise due to the disruption of this order. In this study, we aimed to generate a coculture model of retina-derived cells, namely RPE and Müller cells, in multiplexed 3D hydrogels. Using methacrylated gelatin (GelMA)-based 3D hydrogels, we compared the behavior of RPE and Müller cells when they were cultured together. These patterned multiplex hydrogels containing cells were cultured for several days to reflect how cells would reorganize themselves in the presence of another cellular component derived from the same tissue. Here, we present a multicellular multiplex platform for the creation of cellular networks with cells of retinal tissue that can be easily adapted to create more complex tissue-like alternatives for large-scale tissue modeling and screening purposes. We also present an alternative method of coculture by generating spheroids from one of the components while keeping the other component free and motile in the hydrogel. The latter model predicts enhanced possibilities of cellular interactions by retarding the movement of one of the component cells.

Organoids in Dynamic Culture: Microfluidics and 3D Printing Technologies

With the rapid advancement of biomaterials and tissue engineering technologies, organoid research and its applications have made significant strides. Organoids are increasingly utilized in pharmacology, regenerative medicine, and precision clinical medicine. Current trends in organoid research are moving toward multifunctional composite three-dimensional cultivation and dynamic cultivation strategies. Key technologies driving this evolution, including 3D printing and microfluidics, continue to impact new areas of discovery and clinical relevance. This review provides a systematic overview of these emerging trends, discussing the strengths and limitations of these critical technologies and offering insight and research directions for professionals working in the organoid field.

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.

Retinal Organoids: Innovative Tools for Understanding Retinal Degeneration

Retinal degenerative diseases (RDDs) comprise diverse genetic and phenotypic conditions that cause progressive retinal dysfunction and cell loss, leading to vision impairment or blindness. Most RDDs lack appropriate animal models for their study, which affects understanding their disease mechanisms and delays the progress of new treatment development. Recent advances in stem cell engineering, omics, and organoid technology are facilitating research into diseases for which there are no previously existing models. The development of retinal organoids produced from human stem cells has impacted the study of retinal development as well as the development of in vitro models of diseases, opening possibilities for applications in regenerative medicine, drug discovery, and precision medicine. In this review, we recapitulate research in the retinal organoid models for RDD, mentioning some of the main pathways underlying retinal neurodegeneration that can be studied in these new models, as well as their limitations and future challenges in this rapidly advancing field.

Biomedical applications of organoids in genetic diseases

Organoid technology has significantly transformed biomedical research by providing exceptional prospects for modeling human tissues and disorders in a laboratory setting. It has significant potential for understanding the intricate relationship between genetic mutations, cellular phenotypes, and disease pathology, especially in the field of genetic diseases. The intersection of organoid technology and genetic research offers great promise for comprehending the pathophysiology of genetic diseases and creating innovative treatment approaches customized for specific patients. This review aimed to present a thorough analysis of the current advancements in organoid technology and its biomedical applications for genetic diseases. We examined techniques for modeling genetic disorders using organoid platforms, analyze the approaches for incorporating genetic disease organoids into clinical practice, and showcase current breakthroughs in preclinical application, individualized healthcare, and transplantation. Through the integration of knowledge from several disciplines, such as genetics, regenerative medicine, and biological engineering, our aim is to enhance our comprehension of the complex connection between genetic variations and organoid models in relation to human health and disease.

Organoids - the future of pre-clinical development of AAV gene therapy for CNS disorders

Advancements in our understanding of genetic disease and adeno-associated virus has prompted great excitement into the field of AAV-mediated gene therapy, particularly for genetic diseases of the central nervous system, including retinal disorders. Despite significant progress, exemplified by the approval of therapies such as Luxturna® and Zolgensma®, a substantial number of therapies remain in pre-clinical or early clinical stages, with many failing to advance to later phases. Whilst the use of animal models to test safety and delivery route efficacy of AAV treatments is imperative, differences in tissue structure and physiology between humans and animal models has restricted precise disease modelling and gene therapy development for many CNS disorders. Alongside the FDA push for non-animal alternative models, researchers are increasingly turning to human-based models, including stem cell-derived organoids, which can offer a more accurate representation of human cellular microenvironments and niches. As such, this review explores the advantages and limitations of brain and retinal organoids as pre-clinical models of disease, with a primary focus on their utility in identifying novel AAV capsids, cell-specific promoters, and their role in recent pre-clinical AAV gene therapy studies.

Exploring organoid and assembloid technologies: a focus on retina and brain

BACKGROUND

The recent emergence of three-dimensional organoids and their utilization as in vitro disease models confirmed the complexities behind organ-specific functions and unravelled the importance of establishing suitable human models for various applications. Also, in light of persistent challenges associated with their use, researchers have been striving to establish more advanced structures (i.e. assembloids) that can help address the limitations presented in the current organoids.

METHODS

In this review, we discuss the distinct organoid types that are available to date, with a special focus on retinal and brain organoids, and highlight their importance in disease modelling.

RESULTS

We refer to published research to explore the extent to which retinal and brain organoids can serve as potential alternatives to organ/cell transplants and direct our attention to the topic of photostimulation in retinal organoids. Additionally, we discuss the advantages of incorporating microfluidics and organ-on-a-chip devices for boosting retinal organoid performance. The challenges of organoids leading to the subsequent development of assembloid fusion models are also presented.

CONCLUSION

In conclusion, organoid technology has laid the foundation for generating upgraded models that not only better replicate in vivo systems but also allow for a deeper comprehension of disease pathophysiology.

Retinal organoid chip: engineering a physiomimetic oxygen gradient for optimizing long term culture of human retinal organoids

An oxygen gradient across the retina plays a crucial role in its development and function. The inner retina resides in a hypoxic environment (2% O2) adjacent to the vitreous cavity. Oxygenation levels rapidly increase towards the outer retina (18% O2) at the choroid. In addition to retinal stratification, oxygen levels are critical for the health of retinal ganglion cells (RGCs), which relay visual information from the retina to the brain. Human stem cell derived retinal organoids are being engineered to mimic the structure and function of human retina for applications such as disease modeling, development of therapeutics, and cell replacement therapies. However, rapid degeneration of the retinal ganglion cell layers are a common limitation of human retinal organoid platforms. We report the design of a novel retinal organoid chip (ROC) that maintains a physiologically relevant oxygen gradient and allows the maturation of inner and outer retinal cell phenotypes for human retinal organoids. Our PDMS-free ROC holds 55 individual retinal organoids that were manually seeded, cultured for extended periods (over 150 days), imaged in situ, and retrieved. ROC was designed from first principles of liquid and gas mass transport, and fabricated from biologically- and chemically inert materials using rapid prototyping techniques such as micromachining, laser cutting, 3D printing and bonding. After computational and experimental validation of oxygen gradients, human induced pluripotent stem cell derived retinal organoids were transferred into the ROC, differentiated, cultured and imaged within the chip. ROCs that maintained active perfusion and stable oxygen gradients were successful in inducing higher viability of RGCs within retinal organoids than static controls, or ROC without oxygen gradients. Our physiologically relevant and higher-throughput retinal organoid culture system is well suited for applications in studying developmental perturbations to primate retinogenesis, including those driven by inherited traits, fetal environmental exposure to toxic agents, or acquired by genetic mutations, such as retinoblastoma.

Organoids-on-a-chip: microfluidic technology enables culture of organoids with enhanced tissue function and potential for disease modeling

Organoids are stem-cell derived tissue structures mimicking specific structural and functional characteristics of human organs. Despite significant advancements in the field over the last decade, challenges like limited long-term functional culture and lack of maturation are hampering the implementation of organoids in biomedical research. Culture of organoids in microfluidic chips is being used to tackle these challenges through dynamic and precise control over the organoid microenvironment. This review highlights the significant breakthroughs that have been made in the innovative field of "organoids-on-chip," demonstrating how these have contributed to advancing organoid models. We focus on the incorporation of organoids representative for various tissues into chips and discuss the latest findings in multi-organoids-on-chip approaches. Additionally, we examine current limitations and challenges of the field towards the development of reproducible organoids-on-chip systems. Finally, we discuss the potential of organoids-on-chip technology for both in vitro and in vivo applications.

Design, additive manufacturing, and characterization of an organ-on-chip microfluidic device for oral mucosa analogue growth

INTRODUCTION

Α customized organ-on-a-chip microfluidic device was developed for dynamic culture of oral mucosa equivalents (Oral_mucosa_chip-OMC).

MATERIALS AND METHODS

Additive Manufacturing (AM) was performed via stereolithography (SLA) printing. The dimensional accuracy was evaluated via microfocus computed tomography (mCT), the surface characteristics via scanning electron microscopy (SEM), while the mechanical properties via nanoindentation and compression tests. Computational fluid dynamics (CFD) optimized net forces towards the culture area. An oral mucosa equivalent comprising a multilayered epithelium derived by culture of TR146 cells at the air-liquid interface (ALI) and a lamina propria-analogue based on a collagen-I/fibrin hydrogel was maintained under ultra-precise flow conditions.

RESULTS

An open-type device concept encompassing two interconnected chambers for long-term dynamic culture was developed and characterized for AM parameters, mechanical and biological properties. The split-inlet flow channel architecture allowed even distribution and symmetric flow velocity to the culture area. Cell viability exceeded 90%, while mCT and SEM indicated the 0° building angle as the most accurate SLA condition. CFD further showed that the 0° and 30° building angles most accurately reproduced the channel flow velocity predicted by the initial CAD model.

CONCLUSION

This study developed a customized, easy-to-produce, and cell-friendly OMC device, providing a 3D tool for biocompatibility assessment of biomaterials.

Postnatal development of rat retina: a continuous observation and comparison between the organotypic retinal explant model and in vivo development

JOURNAL/nrgr/04.03/01300535-202503000-00033/figure1/v/2024-06-17T092413Z/r/image-tiff The organotypic retinal explant culture has been established for more than a decade and offers a range of unique advantages compared with in vivo experiments and cell cultures. However, the lack of systematic and continuous comparison between in vivo retinal development and the organotypic retinal explant culture makes this model controversial in postnatal retinal development studies. Thus, we aimed to verify the feasibility of using this model for postnatal retinal development studies by comparing it with the in vivo retina. In this study, we showed that postnatal retinal explants undergo normal development, and exhibit a consistent structure and timeline with retinas in vivo. Initially, we used SOX2 and PAX6 immunostaining to identify retinal progenitor cells. We then examined cell proliferation and migration by immunostaining with Ki-67 and doublecortin, respectively. Ki-67- and doublecortin-positive cells decreased in both in vivo and explants during postnatal retinogenesis, and exhibited a high degree of similarity in abundance and distribution between groups. Additionally, we used Ceh-10 homeodomain-containing homolog, glutamate-ammonia ligase (glutamine synthetase), neuronal nuclei, and ionized calcium-binding adapter molecule 1 immunostaining to examine the emergence of bipolar cells, Müller glia, mature neurons, and microglia, respectively. The timing and spatial patterns of the emergence of these cell types were remarkably consistent between in vivo and explant retinas. Our study showed that the organotypic retinal explant culture model had a high degree of consistency with the progression of in vivo early postnatal retina development. The findings confirm the accuracy and credibility of this model and support its use for long-term, systematic, and continuous observation.

Retina-on-chip: engineering functional in vitro models of the human retina using organ-on-chip technology

The retina is a complex and highly metabolic tissue in the back of the eye essential for human vision. Retinal diseases can lead to loss of vision in early and late stages of life, significantly affecting patients' quality of life. Due to its accessibility for surgical interventions and its isolated nature, the retina is an attractive target for novel genetic therapies and stem cell-based regenerative medicine. Understanding disease mechanisms and evaluating new treatments require relevant and robust experimental models. Retina-on-chip models are microfluidic organ-on-chip systems based on human tissue that capture multi-cellular interactions and tissue-level functions in vitro. Various retina-on-chip models have been described in literature. Some of them capture basic retinal barrier functions while others replicate key events underlying vision. In addition, some of these cellular systems have also been used in studies to explore their added value in retinal disease modeling. Most existing retina-on-chip models capture limited aspects of the phenotypic complexity of human diseases. This limitation arises primarily from the challenges related to controlled recapitulation of retinal function, including the relevant multi-cellular interactions and functional read-outs. In this review, we provide an update on recent advancements in the field of retina-on-chip, and we discuss the biotechnical strategies to further enhance the physiological relevance of the models. We emphasize that developers and researchers should prioritize the incorporation of the full spectrum of retinal complexity to effectuate a direct impact of retina-on-chip models in disease modeling and development of therapeutic strategies.

Retinal Organoids from Induced Pluripotent Stem Cells of Patients with Inherited Retinal Diseases: A Systematic Review

BACKGROUND

Currently, most inherited retinal diseases lack curative interventions, and available treatment modalities are constrained to symptomatic approaches. Retinal organoid technology has emerged as a method for treating inherited retinal diseases, with growing academic interest in recent years. The purpose of this review was to systematically organize the current protocols for generating retinal organoids using induced pluripotent stem cells from patients with inherited retinal disease and to investigate the application of retinal organoids in inherited retinal disease research.

METHODS

Data were collected from the PubMed, Scopus, and Web of Science databases using a keyword search. The main search term used was "retinal organoid," accompanied by secondary keywords such as "optic cup," "three-dimensional," and "self-organizing." The final search was conducted on October 2, 2024.

RESULTS

Of the 2,129 studies retrieved, 130 were included in the qualitative synthesis. The protocols for the generation of retinal organoids in inherited retinal disease research use five major approaches, categorized into 3D and a combination of 2D/3D approaches, implemented with modifications. Disease phenotypes have been successfully reproduced via the generation of retinal organoids from the induced pluripotent stem cells of individuals with inherited retinal diseases, facilitating the progression of research into novel therapeutic developments. Cells have been obtained from retinal organoids for cell therapy, and progress toward their potential integration into clinical practice is underway. Considering their potential applications, retinal organoid technology has shown promise across various domains.

CONCLUSION

In this systematic review, we organized protocols for generating retinal organoids using induced pluripotent stem cells from patients with inherited retinal diseases. Retinal organoid technology has various applications including disease modeling, screening for novel therapies, and cell replacement therapy. Further advancements would make this technology a clinically significant tool for patients with inherited retinal diseases.

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.

In Vitro Models of Diabetes: Focus on Diabetic Retinopathy

Diabetic retinopathy is a major eye complication in patients with diabetes mellitus, and it is the leading cause of blindness and visual impairment in the world. Chronic hyperglycemia induces endothelial damage with consequent vascular lesions, resulting in global vasculitis, which affects the small vessels of the retina. These vascular lesions cause ischemic conditions in certain areas of the retina, with a consequent increase in the release of pro-angiogenic mediators. In addition to pharmacological interventions for controlling the blood glycaemic level, the main strategies for treating diabetic retinopathy are the intravitreal injections of drugs, surgical treatments, and vitrectomies. The complexity of diabetic retinopathy is due to its close interactions with different cell types (endothelial cells, astrocytes, and Müller cells). The evaluation of the efficacy of novel pharmacological strategies is mainly performed through in vivo models. However, the use of different animal species leads to heterogenic results and ethical concerns. For these reasons, the development of new and reliable in vitro models, such as cell co-cultures and eye organoids, represents an urgent need in this area of research. This review features an overview of the in vitro models used to date and highlights the advances in technology used to study this pathology.

Methylglyoxal: A Key Factor for Diabetic Retinopathy and Its Effects on Retinal Damage

Background: Diabetic retinopathy is the most common retinal vascular disease, affecting the retina's blood vessels and causing chronic inflammation, oxidative stress, and, ultimately, vision loss. Diabetes-induced elevated glucose levels increase glycolysis, the main methylglyoxal (MGO) formation pathway. MGO is a highly reactive dicarbonyl and the most rapid glycation compound to form endogenous advanced glycation end products (AGEs). MGO can act both intra- and extracellularly by glycating molecules and activating the receptor for AGEs (RAGE) pathway. Conclusions: This review summarizes the sources of MGO formation and its actions on various cell pathways in retinal cells such as oxidative stress, glycation, autophagy, ER stress, and mitochondrial dysfunction. Finally, the detoxification of MGO by glyoxalases is discussed.

Advances in retinal pigment epithelial cell transplantation for retinal degenerative diseases

Retinal degenerative diseases are a leading cause of vision loss and blindness globally, impacting millions. These diseases result from progressive damage to retinal pigment epithelial (RPE) cells for which no curative or palliative treatments exist. Cell therapy, particularly RPE transplantation, has emerged as a promising strategy for vision restoration. This review provides a comprehensive overview of the recent advancements in clinical trials related to RPE transplantation. We discuss scaffold-free and scaffold-based approaches, including RPE cell suspensions and pre-organized RPE monolayers on biomaterial scaffolds. Key considerations, such as the form and preparation of RPE implants, delivery devices, strategies, and biodegradability of scaffolds, are examined. The article also explores the challenges and opportunities in RPE scaffold development, emphasising the crucial need for functional integration, immunomodulation, and long-term biocompatibility to ensure therapeutic efficacy. We also highlight ongoing efforts to optimise RPE transplantation methods and their potential to address retinal degenerative diseases.

Organoids: development and applications in disease models, drug discovery, precision medicine, and regenerative medicine

Organoids are miniature, highly accurate representations of organs that capture the structure and unique functions of specific organs. Although the field of organoids has experienced exponential growth, driven by advances in artificial intelligence, gene editing, and bioinstrumentation, a comprehensive and accurate overview of organoid applications remains necessary. This review offers a detailed exploration of the historical origins and characteristics of various organoid types, their applications-including disease modeling, drug toxicity and efficacy assessments, precision medicine, and regenerative medicine-as well as the current challenges and future directions of organoid research. Organoids have proven instrumental in elucidating genetic cell fate in hereditary diseases, infectious diseases, metabolic disorders, and malignancies, as well as in the study of processes such as embryonic development, molecular mechanisms, and host-microbe interactions. Furthermore, the integration of organoid technology with artificial intelligence and microfluidics has significantly advanced large-scale, rapid, and cost-effective drug toxicity and efficacy assessments, thereby propelling progress in precision medicine. Finally, with the advent of high-performance materials, three-dimensional printing technology, and gene editing, organoids are also gaining prominence in the field of regenerative medicine. Our insights and predictions aim to provide valuable guidance to current researchers and to support the continued advancement of this rapidly developing field.

Revolutionizing immune research with organoid-based co-culture and chip systems

The intertwined interactions various immune cells have with epithelial cells in our body require sophisticated experimental approaches to be studied. Due to the limitations of immortalized cell lines and animal models, there is an increasing demand for human in vitro model systems to investigate the microenvironment of immune cells in normal and in pathological conditions. Organoids, which are self-renewing, 3D cellular structures that are derived from stem cells, have started to provide gap-filling tissue modelling solutions. In this review, we first demonstrate with some of the available examples how organoid-based immune cell co-culture experiments can advance disease modelling of cancer, inflammatory bowel disease, and tissue regeneration. Then, we argue that to achieve both complexity and scale, organ-on-chip models combined with cutting-edge microfluidics-based technologies can provide more precise manipulation and readouts. Finally, we discuss how genome editing techniques and the use of patient-derived organoids and immune cells can improve disease modelling and facilitate precision medicine. To achieve maximum impact and efficiency, these efforts should be supported by novel infrastructures such as organoid biobanks, organoid facilities, as well as drug screening and host-microbe interaction testing platforms. All these together or in combination can allow researchers to shed more detailed, and often patient-specific, light on the crosstalk between immune cells and epithelial cells in health and disease.

Tissue Engineering of Outer Blood Retina Barrier for Therapeutic Development

Age related macular degeneration and other retinal degenerative disorders are characterized by disruption of the outer blood retinal barrier (oBRB) with subsequent ischemia, neovascularization, and atrophy. Despite the treatment advances, there remains no curative therapy, and no treatment targeted at regenerating native-like tissue for patients with late stages of the disease. Here we present advances in tissue engineering, focusing on bioprinting methods of generating tissue allowing for safe and reliable production of oBRB as well as tissue reprogramming with induced pluripotent stem cells for transplantation. We compare these approaches to organ-on-a-chip models for studying the dynamic nature of physiologic conditions. Highlighted within this review are studies that employ good manufacturing practices and use clinical grade methods that minimize potential risk to patients. Lastly, we illustrate recent clinical applications demonstrating both safety and efficacy for direct patient use. These advances provide an avenue for drug discovery and ultimately transplantation.

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.

Organoid as a promising tool for primary liver cancer research: a comprehensive review

Primary liver cancer (PLC) is one of the most common malignant gastrointestinal tumors worldwide. Limited by the shortage of liver transplantation donors and the heterogeneity of tumors, patients with liver cancer lack effective treatment options, which leads to rapid progression and metastasis. Currently, preclinical models of PLC fall short of clinical reality and are limited in their response to disease progression and the effectiveness of drug therapy. Organoids are in vitro three-dimensional cultured preclinical models with a high degree of heterogeneity that preserve the histomorphological and genomic features of primary tumors. Liver cancer organoids have been widely used for drug screening, new target discovery, and precision medicine; thus representing a promising tool to study PLC. Here, we summarize the progress of research on liver cancer organoids and their potential application as disease models. This review provides a comprehensive introduction to this emerging technology and offers new ideas for researchers to explore in the field of precision medicine.

Gastrointestinal Cancer Patient Derived Organoids at the Frontier of Personalized Medicine and Drug Screening

Cancer is a leading cause of death worldwide. Around one-third of the total global cancer incidence and mortality are related to gastrointestinal (GI) cancers. Over the past few years, rapid developments have been made in patient-derived organoid (PDO) models for gastrointestinal cancers. By closely mimicking the molecular properties of their parent tumors in vitro, PDOs have emerged as powerful tools in personalized medicine and drug discovery. Here, we review the current literature on the application of PDOs of common gastrointestinal cancers in the optimization of drug treatment strategies in the clinic and their rising importance in pre-clinical drug development. We discuss the advantages and limitations of gastrointestinal cancer PDOs and outline the microfluidics-based strategies that improve the throughput of PDO models in order to extract the maximal benefits in the personalized medicine and drug discovery process.

Advances in Microfluidic Technologies in Organoid Research

Organoids have emerged as major technological breakthroughs and novel organ models that have revolutionized biomedical research by recapitulating the key structural and functional complexities of their in vivo counterparts. The combination of organoid systems and microfluidic technologies has opened new frontiers in organoid engineering and offers great opportunities to address the current challenges of existing organoid systems and broaden their biomedical applications. In this review, the key features of the existing organoids, including their origins, development, design principles, and limitations, are described. Then the recent progress in integrating organoids into microfluidic systems is highlighted, involving microarrays for high-throughput organoid manipulation, microreactors for organoid hydrogel scaffold fabrication, and microfluidic chips for functional organoid culture. The opportunities in the nascent combination of organoids and microfluidics that lie ahead to accelerate research in organ development, disease studies, drug screening, and regenerative medicine are also discussed. Finally, the challenges and future perspectives in the development of advanced microfluidic platforms and modified technologies for building organoids with higher fidelity and standardization are envisioned.

Applications of 3D organoids in toxicological studies: a comprehensive analysis based on bibliometrics and advances in toxicological mechanisms

A mechanism exploration is an important part of toxicological studies. However, traditional cell and animal models can no longer meet the current needs for in-depth studies of toxicological mechanisms. The three-dimensional (3D) organoid derived from human embryonic stem cells (hESC) or induced pluripotent stem cells (hiPSC) is an ideal experimental model for the study of toxicological effects and mechanisms, which further recapitulates the human tissue microenvironment and provides a reliable method for studying complex cell-cell interactions. This article provides a comprehensive overview of the state of the 3D organoid technology in toxicological studies, including a bibliometric analysis of the existing literature and an exploration of the latest advances in toxicological mechanisms. The use of 3D organoids in toxicology research is growing rapidly, with applications in disease modeling, organ-on-chips, and drug toxicity screening being emphasized, but academic communications among countries/regions, institutions, and research scholars need to be further strengthened. Attempts to study the toxicological mechanisms of exogenous chemicals such as heavy metals, nanoparticles, drugs and organic pollutants are also increasing. It can be expected that 3D organoids can be better applied to the safety evaluation of exogenous chemicals by establishing a standardized methodology.

A Pillar and Perfusion Plate Platform for Robust Human Organoid Culture and Analysis

Human organoids have the potential to revolutionize in vitro disease modeling by providing multicellular architecture and function that are similar to those in vivo. This innovative and evolving technology, however, still suffers from assay throughput and reproducibility to enable high-throughput screening (HTS) of compounds due to cumbersome organoid differentiation processes and difficulty in scale-up and quality control. Using organoids for HTS is further challenged by the lack of easy-to-use fluidic systems that are compatible with relatively large organoids. Here, these challenges are overcome by engineering "microarray three-dimensional (3D) bioprinting" technology and associated pillar and perfusion plates for human organoid culture and analysis. High-precision, high-throughput stem cell printing, and encapsulation techniques are demonstrated on a pillar plate, which is coupled with a complementary deep well plate and a perfusion well plate for static and dynamic organoid culture. Bioprinted cells and spheroids in hydrogels are differentiated into liver and intestine organoids for in situ functional assays. The pillar/perfusion plates are compatible with standard 384-well plates and HTS equipment, and thus may be easily adopted in current drug discovery efforts.

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.

Modeling inherited retinal diseases using human induced pluripotent stem cell derived photoreceptor cells and retinal pigment epithelial cells

Since the discovery of induced pluripotent stem cell (iPSC) technology, there have been many attempts to create cellular models of inherited retinal diseases (IRDs) for investigation of pathogenic processes to facilitate target discovery and validation activities. Consistency remains key in determining the utility of these findings. Despite the importance of consistency, quality control metrics are still not widely used. In this review, a toolkit for harnessing iPSC technology to generate photoreceptor, retinal pigment epithelial cell, and organoid disease models is provided. Considerations while developing iPSC-derived IRD models such as iPSC origin, reprogramming methods, quality control metrics, control strategies, and differentiation protocols are discussed. Various iPSC IRD models are dissected and the scientific hurdles of iPSC-based disease modeling are discussed to provide an overview of current methods and future directions in this field.

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

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

Bioengineering methods for vascularizing organoids

Organoids, self-organizing three-dimensional (3D) structures derived from stem cells, offer unique advantages for studying organ development, modeling diseases, and screening potential therapeutics. However, their translational potential and ability to mimic complex in vivo functions are often hindered by the lack of an integrated vascular network. To address this critical limitation, bioengineering strategies are rapidly advancing to enable efficient vascularization of organoids. These methods encompass co-culturing organoids with various vascular cell types, co-culturing lineage-specific organoids with vascular organoids, co-differentiating stem cells into organ-specific and vascular lineages, using organoid-on-a-chip technology to integrate perfusable vasculature within organoids, and using 3D bioprinting to also create perfusable organoids. This review explores the field of organoid vascularization, examining the biological principles that inform bioengineering approaches. Additionally, this review envisions how the converging disciplines of stem cell biology, biomaterials, and advanced fabrication technologies will propel the creation of increasingly sophisticated organoid models, ultimately accelerating biomedical discoveries and innovations.

Lab-on-a-chip: an advanced technology for the modernization of traditional Chinese medicine

Benefiting from the complex system composed of various constituents, medicament portions, species, and places of origin, traditional Chinese medicine (TCM) possesses numerous customizable and adaptable efficacies in clinical practice guided by its theories. However, these unique features are also present challenges in areas such as quality control, screening active ingredients, studying cell and organ pharmacology, and characterizing the compatibility between different Chinese medicines. Drawing inspiration from the holistic concept, an integrated strategy and pattern more aligned with TCM research emerges, necessitating the integration of novel technology into TCM modernization. The microfluidic chip serves as a powerful platform for integrating technologies in chemistry, biology, and biophysics. Microfluidics has given rise to innovative patterns like lab-on-a-chip and organoids-on-a-chip, effectively challenging the conventional research paradigms of TCM. This review provides a systematic summary of the nature and advanced utilization of microfluidic chips in TCM, focusing on quality control, active ingredient screening/separation, pharmaceutical analysis, and pharmacological/toxicological assays. Drawing on these remarkable references, the challenges, opportunities, and future trends of microfluidic chips in TCM are also comprehensively discussed, providing valuable insights into the development of TCM.

The application of retinal organoids in ophthalmic regenerative medicine: A mini-review

Retinal organoids are three-dimensional (3D) microscopic tissues that are induced and differentiated from stem cells or progenitor cells in vitro and have a highly similar structure to the retina. With the optimization and development of 3D retinal culture system and the improvement of induced differentiation technology, retinal organoids have broad application prospects in retinal development, regenerative medicine, biomaterial evaluation, disease mechanism investigation, and drug screening. In this review we summarize recent development of retinal organoids and their applications in ophthalmic regenerative medicine. In particular, we highlight the promise and challenges in the use of retinal organoids in disease modeling and drug discovery.

Modeling complex age-related eye disease

Modeling complex eye diseases like age-related macular degeneration (AMD) and glaucoma poses significant challenges, since these conditions depend highly on age-related changes that occur over several decades, with many contributing factors remaining unknown. Although both diseases exhibit a relatively high heritability of >50%, a large proportion of individuals carrying AMD- or glaucoma-associated genetic risk variants will never develop these diseases. Furthermore, several environmental and lifestyle factors contribute to and modulate the pathogenesis and progression of AMD and glaucoma. Several strategies replicate the impact of genetic risk variants, pathobiological pathways and environmental and lifestyle factors in AMD and glaucoma in mice and other species. In this review we will primarily discuss the most commonly available mouse models, which have and will likely continue to improve our understanding of the pathobiology of age-related eye diseases. Uncertainties persist whether small animal models can truly recapitulate disease progression and vision loss in patients, raising doubts regarding their usefulness when testing novel gene or drug therapies. We will elaborate on concerns that relate to shorter lifespan, body size and allometries, lack of macula and a true lamina cribrosa, as well as absence and sequence disparities of certain genes and differences in their chromosomal location in mice. Since biological, rather than chronological, age likely predisposes an organism for both glaucoma and AMD, more rapidly aging organisms like small rodents may open up possibilities that will make research of these diseases more timely and financially feasible. On the other hand, due to the above-mentioned anatomical and physiological features, as well as pharmacokinetic and -dynamic differences small animal models are not ideal to study the natural progression of vision loss or the efficacy and safety of novel therapies. In this context, we will also discuss the advantages and pitfalls of alternative models that include larger species, such as non-human primates and rabbits, patient-derived retinal organoids, and human organ donor eyes.

Generation of Anterior Segment of the Eye Cells from hiPSCs in Microfluidic Platforms

Ophthalmic diseases affect many people, causing partial or total loss of vision and a reduced quality of life. The anterior segment of the eye accounts for nearly half of all visual impairment that can lead to blindness. Therefore, there is a growing demand for ocular research and regenerative medicine that specifically targets the anterior segment to improve vision quality. This study aims to generate a microfluidic platform for investigating the formation of the anterior segment of the eye derived from human induced pluripotent stem cells (hiPSC) under various spatial-mechanoresponsive conditions. Microfluidic platforms are developed to examine the effects of dynamic conditions on the generation of hiPSCs-derived ocular organoids. The differentiation protocol is validated, and mechanoresponsive genes are identified through transcriptomic analysis. Several culture strategies is implemented for the anterior segment of eye cells in a microfluidic chip. hiPSC-derived cells showed anterior eye cell characteristics in mRNA and protein expression levels under dynamic culture conditions. The expression levels of yes-associated protein and transcriptional coactivator PDZ binding motif (YAP/TAZ) and PIEZO1, varied depending on the differentiation and growth conditions of the cells, as well as the metabolomic profiles under dynamic culture conditions.

Pluripotent stem cell-derived models of retinal disease: Elucidating pathogenesis, evaluating novel treatments, and estimating toxicity

Blindness poses a growing global challenge, with approximately 26% of cases attributed to degenerative retinal diseases. While gene therapy, optogenetic tools, photosensitive switches, and retinal prostheses offer hope for vision restoration, these high-cost therapies will benefit few patients. Understanding retinal diseases is therefore key to advance effective treatments, requiring in vitro models replicating pathology and allowing quantitative assessments for drug discovery. Pluripotent stem cells (PSCs) provide a unique solution given their limitless supply and ability to differentiate into light-responsive retinal tissues encompassing all cell types. This review focuses on the history and current state of photoreceptor and retinal pigment epithelium (RPE) cell generation from PSCs. We explore the applications of this technology in disease modelling, experimental therapy testing, biomarker identification, and toxicity studies. We consider challenges in scalability, standardisation, and reproducibility, and stress the importance of incorporating vasculature and immune cells into retinal organoids. We advocate for high-throughput automation in data acquisition and analyses and underscore the value of advanced micro-physiological systems that fully capture the interactions between the neural retina, RPE, and choriocapillaris.

Review: 3D cell models for organ-on-a-chip applications

Two-dimensional (2D) cultures do not fully reflect the human organs' physiology and the real effectiveness of the used therapy. Therefore, three-dimensional (3D) models are increasingly used in bioanalytical science. Organ-on-a-chip systems are used to obtain cellular in vitro models, better reflecting the human body's in vivo characteristics and allowing us to obtain more reliable results than standard preclinical models. Such 3D models can be used to understand the behavior of tissues/organs in response to selected biophysical and biochemical factors, pathological conditions (the mechanisms of their formation), drug screening, or inter-organ interactions. This review characterizes 3D models obtained in microfluidic systems. These include spheroids/aggregates, hydrogel cultures, multilayers, organoids, or cultures on biomaterials. Next, the methods of formation of different 3D cultures in Organ-on-a-chip systems are presented, and examples of such Organ-on-a-chip systems are discussed. Finally, current applications of 3D cell-on-a-chip systems and future perspectives are covered.

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.

Understanding the Impact of Polyunsaturated Fatty Acids on Age-Related Macular Degeneration: A Review

Age-related Macular Degeneration (AMD) is a multifactorial ocular pathology that destroys the photoreceptors of the macula. Two forms are distinguished, dry and wet AMD, with different pathophysiological mechanisms. Although treatments were shown to be effective in wet AMD, they remain a heavy burden for patients and caregivers, resulting in a lack of patient compliance. For dry AMD, no real effective treatment is available in Europe. It is, therefore, essential to look for new approaches. Recently, the use of long-chain and very long-chain polyunsaturated fatty acids was identified as an interesting new therapeutic alternative. Indeed, the levels of these fatty acids, core components of photoreceptors, are significantly decreased in AMD patients. To better understand this pathology and to evaluate the efficacy of various molecules, in vitro and in vivo models reproducing the mechanisms of both types of AMD were developed. This article reviews the anatomy and the physiological aging of the retina and summarizes the clinical aspects, pathophysiological mechanisms of AMD and potential treatment strategies. In vitro and in vivo models of AMD are also presented. Finally, this manuscript focuses on the application of omega-3 fatty acids for the prevention and treatment of both types of AMD.

Microphysiological systems for human aging research

Recent advances in microphysiological systems (MPS), also known as organs-on-a-chip (OoC), enable the recapitulation of more complex organ and tissue functions on a smaller scale in vitro. MPS therefore provide the potential to better understand human diseases and physiology. To date, numerous MPS platforms have been developed for various tissues and organs, including the heart, liver, kidney, blood vessels, muscle, and adipose tissue. However, only a few studies have explored using MPS platforms to unravel the effects of aging on human physiology and the pathogenesis of age-related diseases. Age is one of the risk factors for many diseases, and enormous interest has been devoted to aging research. As such, a human MPS aging model could provide a more predictive tool to understand the molecular and cellular mechanisms underlying human aging and age-related diseases. These models can also be used to evaluate preclinical drugs for age-related diseases and translate them into clinical settings. Here, we provide a review on the application of MPS in aging research. First, we offer an overview of the molecular, cellular, and physiological changes with age in several tissues or organs. Next, we discuss previous aging models and the current state of MPS for studying human aging and age-related conditions. Lastly, we address the limitations of current MPS and present future directions on the potential of MPS platforms for human aging research.

Toward Retinal Organoids in High-Throughput

Human retinal organoids recapitulate the cellular diversity, arrangement, gene expression, and functional aspects of the human retina. Protocols to generate human retinal organoids from pluripotent stem cells are typically labor intensive, include many manual handling steps, and the organoids need to be maintained for several months until they mature. To generate large numbers of human retinal organoids for therapy development and screening purposes, scaling up retinal organoid production, maintenance, and analysis is of utmost importance. In this review, we discuss strategies to increase the number of high-quality retinal organoids while reducing manual handling steps. We further review different approaches to analyze thousands of retinal organoids with currently available technologies and point to challenges that still await to be overcome both in culture and analysis of retinal organoids.

Patient-Derived Microphysiological Systems for Precision Medicine

Patient-derived microphysiological systems (P-MPS) have emerged as powerful tools in precision medicine that provide valuable insight into individual patient characteristics. This review discusses the development of P-MPS as an integration of patient-derived samples, including patient-derived cells, organoids, and induced pluripotent stem cells, into well-defined MPSs. Emphasizing the necessity of P-MPS development, its significance as a nonclinical assessment approach that bridges the gap between traditional in vitro models and clinical outcomes is highlighted. Additionally, guidance is provided for engineering approaches to develop microfluidic devices and high-content analysis for P-MPSs, enabling high biological relevance and high-throughput experimentation. The practical implications of the P-MPS are further examined by exploring the clinically relevant outcomes obtained from various types of patient-derived samples. The construction and analysis of these diverse samples within the P-MPS have resulted in physiologically relevant data, paving the way for the development of personalized treatment strategies. This study describes the significance of the P-MPS in precision medicine, as well as its unique capacity to offer valuable insights into individual patient characteristics.

Retinal Ciliopathies and Potential Gene Therapies: A Focus on Human iPSC-Derived Organoid Models

The human photoreceptor function is dependent on a highly specialised cilium. Perturbation of cilial function can often lead to death of the photoreceptor and loss of vision. Retinal ciliopathies are a genetically diverse range of inherited retinal disorders affecting aspects of the photoreceptor cilium. Despite advances in the understanding of retinal ciliopathies utilising animal disease models, they can often lack the ability to accurately mimic the observed patient phenotype, possibly due to structural and functional deviations from the human retina. Human-induced pluripotent stem cells (hiPSCs) can be utilised to generate an alternative disease model, the 3D retinal organoid, which contains all major retinal cell types including photoreceptors complete with cilial structures. These retinal organoids facilitate the study of disease mechanisms and potential therapies in a human-derived system. Three-dimensional retinal organoids are still a developing technology, and despite impressive progress, several limitations remain. This review will discuss the state of hiPSC-derived retinal organoid technology for accurately modelling prominent retinal ciliopathies related to genes, including RPGR, CEP290, MYO7A, and USH2A. Additionally, we will discuss the development of novel gene therapy approaches targeting retinal ciliopathies, including the delivery of large genes and gene-editing techniques.

Modular tissue-in-a-CUBE platform to model blood-brain barrier (BBB) and brain interaction

With the advent of increasingly sophisticated organoids, there is growing demand for technology to replicate the interactions between multiple tissues or organs. This is challenging to achieve, however, due to the varying culture conditions of the different cell types that make up each tissue. Current methods often require complicated microfluidic setups, but fragile tissue samples tend not to fare well with rough handling. Furthermore, the more complicated the human system to be replicated, the more difficult the model becomes to operate. Here, we present the development of a multi-tissue chip platform that takes advantage of the modularity and convenient handling ability of a CUBE device. We first developed a blood-brain barrier-in-a-CUBE by layering astrocytes, pericytes, and brain microvascular endothelial cells in the CUBE, and confirmed the expression and function of important tight junction and transporter proteins in the blood-brain barrier model. Then, we demonstrated the application of integrating Tissue-in-a-CUBE with a chip in simulating the in vitro testing of the permeability of a drug through the blood-brain barrier to the brain and its effect on treating the glioblastoma brain cancer model. We anticipate that this platform can be adapted for use with organoids to build complex human systems in vitro by the combination of multiple simple CUBE units.

Modeling early pathophysiological phenotypes of diabetic retinopathy in a human inner blood-retinal barrier-on-a-chip

Diabetic retinopathy (DR) is a microvascular disorder characterized by inner blood-retinal barrier (iBRB) breakdown and irreversible vision loss. While the symptoms of DR are known, disease mechanisms including basement membrane thickening, pericyte dropout and capillary damage remain poorly understood and interventions to repair diseased iBRB microvascular networks have not been developed. In addition, current approaches using animal models and in vitro systems lack translatability and predictivity to finding new target pathways. Here, we develop a diabetic iBRB-on-a-chip that produces pathophysiological phenotypes and disease pathways in vitro that are representative of clinical diagnoses. We show that diabetic stimulation of the iBRB-on-a-chip mirrors DR features, including pericyte loss, vascular regression, ghost vessels, and production of pro-inflammatory factors. We also report transcriptomic data from diabetic iBRB microvascular networks that may reveal drug targets, and examine pericyte-endothelial cell stabilizing strategies. In summary, our model recapitulates key features of disease, and may inform future therapies for DR.

Modelling neurodegeneration and inflammation in early diabetic retinopathy using 3D human retinal organoids

Purpose

Diabetic retinopathy (DR) is a complication of diabetes and a primary cause of visual impairment amongst working-age individuals. DR is a degenerative condition in which hyperglycaemia results in morphological and functional changes in certain retinal cells. Existing treatments mainly address the advanced stages of the disease, which involve vascular defects or neovascularization. However, it is now known that retinal neurodegeneration and inflammation precede these vascular changes as early events of DR. Therefore, there is a pressing need to develop a reliable human in vitro model that mimics the early stage of DR to identify new therapeutic approaches to prevent and delay its progression.

Methods

Here, we used human-induced pluripotent stem cells (hiPSCs) differentiated into three-dimensional (3D) retinal organoids, which resemble the complexity of the retinal tissue. Retinal organoids were subjected to high-glucose conditions to generate a model of early DR.

Results

Our model showed well-established molecular and cellular features of early DR, such as (i) loss of retinal ganglion and amacrine cells; (ii) glial reactivity and inflammation, with increased expression of the vascular endothelial-derived growth factor (VEGF) and interleukin-1β (IL-1β), and monocyte chemoattractant protein-1 (MCP-1) secretion; and (iii) increased levels of reactive oxygen species accompanied by activation of key enzymes involved in antioxidative stress response.

Conclusion

The data provided highlight the utility of retinal organoid technology in modelling early-stage DR. This offers new avenues for the development of targeted therapeutic interventions on neurodegeneration and inflammation in the initial phase of DR, potentially slowing the disease's progression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s44164-024-00068-1.