In vitro organogenesis from pluripotent stem cells

Organoids as complex (bio)systems

Organoids are three-dimensional structures derived from stem cells that mimic the organization and function of specific organs, making them valuable tools for studying complex systems in biology. This paper explores the application of complex systems theory to understand and characterize organoids as exemplars of intricate biological systems. By identifying and analyzing common design principles observed across diverse natural, technological, and social complex systems, we can gain insights into the underlying mechanisms governing organoid behavior and function. This review outlines general design principles found in complex systems and demonstrates how these principles manifest within organoids. By acknowledging organoids as representations of complex systems, we can illuminate our understanding of their normal physiological behavior and gain valuable insights into the alterations that can lead to disease. Therefore, incorporating complex systems theory into the study of organoids may foster novel perspectives in biology and pave the way for new avenues of research and therapeutic interventions to improve human health and wellbeing.

Inventing Engineered Organoids for end-stage liver failure patients

End-stage liver disease (ESLD) is a term used clinically in reference to a group of liver diseases with liver transplantation as the choice of treatment. Due to the limitations of liver transplantation, alternative treatments are needed. The use of primary human hepatocytes represents a valid alternative treatment, but the limitations related to hepatocyte quality, viability, function, conservation, and storage need to be overcome. Transplanted hepatocytes have only been followed for 6–9 months. Therefore, long-term causes of failures are not yet established, including rejection, apoptosis, or other causes. Other alternative therapies to replace liver transplantation include plasmapheresis, hemodiafiltration, and artificial livers. Unfortunately, these methods are highly limited due to availability, high cost, anaphylaxis reaction, development-deposition of immune-complexes, and restricted functionality. Liver organoids, which utilize stem cells instead of ‘impractical’ adult hepatocytes, may be a solution for the development of a complex bioartificial liver. Recent studies have explored the benefits of differentiating mature hepatocytes from stem cells inside a bioreactor. When the use of human-induced Hepatocytes (hiHeps) was investigated in mouse and pig models of liver failure, liver failure markers were decreased, hepatocyte function indicated by albumin synthesis improved, and survival time increased. Bioartificial liver treatment may decrease the infiltration of inflammatory cells into liver tissue by down-regulating pro-inflammatory cytokines.

Reconstituting neurovascular unit based on the close relations between neural stem cells and endothelial cells: an effective method to explore neurogenesis and angiogenesis

The discovery of neural stem cells (NSCs) and their microenvironment, the NSC niche, brought new therapeutic strategies through neurogenesis and angiogenesis for stroke and most neurodegenerative diseases, including Alzheimer's disease. Based on the close links between NSCs and endothelial cells, the integration of neurogenesis and angiogenesis of the NSC niche is also a promising area to the neurovascular unit (NVU) modeling and is now offering a powerful tool to advance our understanding of the brain. In this review, critical aspects of the NVU and model systems are discussed. First, we briefly describe the interaction of each part in the NSC niche. Second, we introduce the co-culture system, microfluidic platforms, and stem cell-derived 3D reconstitution used in NVU modeling based on the close relations between NSCs and endothelial cells, and various characteristics of cell interactions in these systems are also described. Finally, we address the challenges in modeling the NVU that can potentially be overcome by employing strategies for advanced biomaterials and stem cell co-culture use. Based on these approaches, researchers will continue to develop predictable technologies to control the fate of stem cells, achieve accurate screening of drugs for the nervous system, and advance the clinical application of NVU models.

The Use of Stem Cell-Derived Organoids in Disease Modeling: An Update

Organoids represent one of the most important advancements in the field of stem cells during the past decade. They are three-dimensional in vitro culturing models that originate from self-organizing stem cells and can mimic the in vivo structural and functional specificities of body organs. Organoids have been established from multiple adult tissues as well as pluripotent stem cells and have recently become a powerful tool for studying development and diseases in vitro, drug screening, and host-microbe interaction. The use of stem cells-that have self-renewal capacity to proliferate and differentiate into specialized cell types-for organoids culturing represents a major advancement in biomedical research. Indeed, this new technology has a great potential to be used in a multitude of fields, including cancer research, hereditary and infectious diseases. Nevertheless, organoid culturing is still rife with many challenges, not limited to being costly and time consuming, having variable rates of efficiency in generation and maintenance, genetic stability, and clinical applications. In this review, we aim to provide a synopsis of pluripotent stem cell-derived organoids and their use for disease modeling and other clinical applications.

Genetic, clinical, molecular, and pathogenic aspects of the South Asian-specific polymorphic MYBPC3Δ25bp variant

Hypertrophic cardiomyopathy (HCM) is a cardiac genetic disease characterized by ventricular enlargement, diastolic dysfunction, and increased risk for sudden cardiac death. Sarcomeric genetic defects are the predominant known cause of HCM. In particular, mutations in the myosin-binding protein C gene (MYBPC3) are associated with ~ 40% of all HCM cases in which a genetic basis has been established. A decade ago, our group reported a 25-base pair deletion in intron 32 of MYBPC3 (MYBPC3Δ25bp) that is uniquely prevalent in South Asians and is associated with autosomal dominant cardiomyopathy. Although our studies suggest that this deletion results in left ventricular dysfunction, cardiomyopathies, and heart failure, the precise mechanism by which this variant predisposes to heart disease remains unclear. Increasingly appreciated, however, is the contribution of secondary risk factors, additional mutations, and lifestyle choices in augmenting or modifying the HCM phenotype in MYBPC3Δ25bp carriers. Therefore, the goal of this review article is to summarize the current research dedicated to understanding the molecular pathophysiology of HCM in South Asians with the MYBPC3Δ25bp variant. An emphasis is to review the latest techniques currently applied to explore the MYBPC3Δ25bp pathogenesis and to provide a foundation for developing new diagnostic strategies and advances in therapeutics.

Brain Organoids: Tiny Mirrors of Human Neurodevelopment and Neurological Disorders

Unravelling the complexity of the human brain is a challenging task. Nowadays, modern neurobiologists have developed 3D model systems called "brain organoids" to overcome the technical challenges in understanding human brain development and the limitations of animal models to study neurological diseases. Certainly like most model systems in neuroscience, brain organoids too have limitations, as these minuscule brains lack the complex neuronal circuitry required to begin the operational tasks of human brain. However, researchers are hopeful that future endeavors with these 3D brain tissues could provide mechanistic insights into the generation of circuit complexity as well as reproducible creation of different regions of the human brain. Herein, we have presented the contemporary state of brain organoids with special emphasis on their mode of generation and their utility in modelling neurological disorders, drug discovery, and clinical trials.

The synergistic effect of low oxygen tension and macromolecular crowding in the development of extracellular matrix-rich tendon equivalents

Cellular therapies play an important role in tendon tissue engineering, with tenocytes being the most prominent and potent cell population available. However, for the development of a rich extracellular matrix tenocyte-assembled tendon equivalent, prolonged in vitro culture is required, which is associated with phenotypic drift. Recapitulation of tendon tissue microenvironment in vitro with cues that enhance and accelerate extracellular matrix synthesis and deposition, whilst maintaining tenocyte phenotype, may lead to functional cell therapies. Herein, we assessed the synergistic effect of low oxygen tension (enhances extracellular matrix synthesis) and macromolecular crowding (enhances extracellular matrix deposition) in human tenocyte culture. Protein analysis demonstrated that human tenocytes at 2% oxygen tension and with 50 μg ml^-1 carrageenan (macromolecular crowder used) significantly increased synthesis and deposition of collagen types I, III, V and VI. Gene analysis at day 7 illustrated that human tenocytes at 2% oxygen tension and with 50 μg ml^-1 carrageenan significantly increased the expression of prolyl 4-hydroxylase subunit alpha 1, procollagen-lysine 2- oxoglutarate 5-dioxygenase 2, scleraxis, tenomodulin and elastin, whilst chondrogenic (e.g. runt-related transcription factor 2, cartilage oligomeric matrix protein, aggrecan) and osteogenic (e.g. secreted phosphoprotein 1, bone gamma-carboxyglutamate protein) trans-differentiation markers were significantly down-regulated or remained unchanged. Collectively, our data clearly illustrates the beneficial synergistic effect of low oxygen tension and macromolecular crowding in the accelerated development of tissue equivalents.

Summit proceedings: Biomedical countermeasure development for emerging vector-borne viral diseases

Emerging and re-emerging infectious diseases are an expanding global threat to public health, security, and economies. Increasing populations, urbanization, deforestation, climate change, anti-vaccination movements, war, and international travel are some of the contributing factors to this trend. The recent Ebola, MERS-CoV, and Zika outbreaks demonstrated we are insufficiently prepared to respond with proven safe and effective countermeasures (i.e., vaccines and therapeutics). The State University of New York Upstate Medical University and the Trudeau Institute convened a summit of key opinion and thought leaders in the life sciences and biomedical research and development enterprises to explore global biopreparedness challenges, take an inventory of existing capabilities and capacities related to preparation and response, assess current "gaps," and prospect what could be done to improve our position. Herein we describe the summit proceedings, "Translational Immunology Supporting Biomedical Countermeasure Development for Emerging Vector-borne Viral Diseases," held October 2-3, 2018, at the Trudeau Institute in Saranac Lake, NY.

Design Principles for Pluripotent Stem Cell-Derived Organoid Engineering

Human morphogenesis is a complex process involving distinct microenvironmental and physical signals that are manipulated in space and time to give rise to complex tissues and organs. Advances in pluripotent stem cell (PSC) technology have promoted the in vitro recreation of processes involved in human morphogenesis. The development of organoids from human PSCs represents one reliable source for modeling a large spectrum of human disorders, as well as a promising approach for drug screening and toxicological tests. Based on the "self-organization" capacity of stem cells, different PSC-derived organoids have been created; however, considerable differences between in vitro-generated PSC-derived organoids and their in vivo counterparts have been reported. Advances in the bioengineering field have allowed the manipulation of different components, including cellular and noncellular factors, to better mimic the in vivo microenvironment. In this review, we focus on different examples of bioengineering approaches used to promote the self-organization of stem cells, including assembly, patterning, and morphogenesis in vitro, contributing to tissue-like structure formation.

The Use of Pluripotent Stem Cell-Derived Organoids to Study Extracellular Matrix Development during Neural Degeneration

The mechanism that causes the Alzheimer's disease (AD) pathologies, including amyloid plaque, neurofibrillary tangles, and neuron death, is not well understood due to the lack of robust study models for human brain. Three-dimensional organoid systems based on human pluripotent stem cells (hPSCs) have shown a promising potential to model neurodegenerative diseases, including AD. These systems, in combination with engineering tools, allow in vitro generation of brain-like tissues that recapitulate complex cell-cell and cell-extracellular matrix (ECM) interactions. Brain ECMs play important roles in neural differentiation, proliferation, neuronal network, and AD progression. In this contribution related to brain ECMs, recent advances in modeling AD pathology and progression based on hPSC-derived neural cells, tissues, and brain organoids were reviewed and summarized. In addition, the roles of ECMs in neural differentiation of hPSCs and the influences of heparan sulfate proteoglycans, chondroitin sulfate proteoglycans, and hyaluronic acid on the progression of neurodegeneration were discussed. The advantages that use stem cell-based organoids to study neural degeneration and to investigate the effects of ECM development on the disease progression were highlighted. The contents of this article are significant for understanding cell-matrix interactions in stem cell microenvironment for treating neural degeneration.

Cell population balance of cardiovascular spheroids derived from human induced pluripotent stem cells

Stem cell-derived cardiomyocytes and vascular cells can be used for a variety of applications such as studying human heart development and modelling human disease in culture. In particular, protocols based on modulation of Wnt signaling were able to produce high quality of cardiomyocytes or vascular cells from human pluripotent stem cells (hPSCs). However, the mechanism behind the development of 3D cardiovascular spheroids into either vascular or cardiac cells has not been well explored. Hippo/Yes-associated protein (YAP) signaling plays important roles in the regulation of organogenesis, but its impact on cardiovascular differentiation has been less evaluated. In this study, the effects of seeding density and a change in YAP signaling on 3D cardiovascular spheroids patterning from hPSCs were evaluated. Compared to 2D culture, 3D cardiovascular spheroids exhibited higher levels of sarcomeric striations and higher length-to-width ratios of α-actinin⁺ cells. The spheroids with high seeding density exhibited more α-actinin⁺ cells and less nuclear YAP expression. The 3D cardiovascular spheroids were also treated with different small molecules, including Rho kinase inhibitor (Y27632), Cytochalasin D, Dasatinib, and Lysophosphatidic acid to modulate YAP localization. Nuclear YAP inhibition resulted in lower expression of active β-catenin, vascular marker, and MRTF, the transcription factor mediated by RhoGTPases. Y27632 also promoted the gene expression of MMP-2/-3 (matrix remodeling) and Notch-1 (Notch signaling). These results should help our understanding of the underlying effects for the efficient patterning of cardiovascular spheroids after mesoderm formation from hPSCs.

Generation of Pancreatic Ductal Organoids and Whole-Mount Immunostaining of Intact Organoids

Traditionally, studies of cells and tissues have been performed on isolated primary cells or immortalized cell lines by culturing them in 2D culture dishes or flasks. However, a caveat regarding 2D culture is that the cells poorly recapitulate their in vivo counterparts, mainly due to a lack of 3D cell-cell and cell-extracellular matrix interactions. In recent years, the development of in vitro organoids as 3D culture has gained substantial attention as a model to study different tissues. In adults, pancreatic ductal cells are considered as a source of stem or progenitor cells, so developing new methods to study ductal cells would be useful. Here, we provide a protocol to isolate mouse pancreatic ductal cells and a cost-effective protocol to generate 3D organoid structures from such ductal cells. Additionally, we have devised a protocol for immunostaining of intact whole organoids without sectioning. © 2018 by John Wiley & Sons, Inc.

Differential Effects of Heparin and Hyaluronic Acid on Neural Patterning of Human Induced Pluripotent Stem Cells

A lack of well-established animal models that can efficiently represent human brain pathology has led to the development of human induced pluripotent stem cell (hiPSC)-derived brain tissues. Brain organoids have enhanced our ability to understand the developing human brain and brain disorders (e.g., Schizophrenia, microcephaly), but the organoids still do not accurately recapitulate the anatomical organization of the human brain. Therefore, it is important to evaluate and optimize induction and signaling factors in order to engineer the next generation of brain organoids. In this study, the impact of hyaluronic acid (HA), a major brain extracellular matrix (ECM) component that interacts with cells through ligand-binding receptors, on the patterning of brain organoids from hiPSCs was evaluated. To mediate HA- binding capacity of signaling molecules, heparin was added in addition to HA or conjugated to HA to form hydrogels (with two different moduli). The neural cortical spheroids derived from hiPSCs were treated with either HA or heparin plus HA (Hep- HA) and were analyzed for ECM impacts on neural patterning. The results indicate that Hep-HA has a caudalizing effect on hiPSC-derived neural spheroids, in particular for stiff Hep-HA hydrogels. Wnt and Hippo/Yes-associated protein (YAP) signaling was modulated (using Wnt inhibitor IWP4 or actin disruption agent Cytochalasin D respectively) to understand the underlying mechanism. IWP4 and cytochalasin D promote forebrain identity. The results from this study should enhance the understanding of influence of biomimetic ECM factors for brain organoid generation.

Wnt/Yes-Associated Protein Interactions During Neural Tissue Patterning of Human Induced Pluripotent Stem Cells

Human induced pluripotent stem cells (hiPSCs) have special ability to self-assemble into neural spheroids or mini-brain-like structures. During the self-assembly process, Wnt signaling plays an important role in regional patterning and establishing positional identity of hiPSC-derived neural progenitors. Recently, the role of Wnt signaling in regulating Yes-associated protein (YAP) expression (nuclear or cytoplasmic), the pivotal regulator during organ growth and tissue generation, has attracted increasing interests. However, the interactions between Wnt and YAP expression for neural lineage commitment of hiPSCs remain poorly explored. The objective of this study is to investigate the effects of Wnt signaling and YAP expression on the cellular population in three-dimensional (3D) neural spheroids derived from hiPSCs. In this study, Wnt signaling was activated using CHIR99021 for 3D neural spheroids derived from human iPSK3 cells through embryoid body formation. Our results indicate that Wnt activation induces nuclear localization of YAP and upregulates the expression of HOXB4, the marker for hindbrain/spinal cord. By contrast, the cells exhibit more rostral forebrain neural identity (expression of TBR1) without Wnt activation. Cytochalasin D was then used to induce cytoplasmic YAP and the results showed the decreased HOXB4 expression. In addition, the incorporation of microparticles in the neural spheroids was investigated for the perturbation of neural patterning. This study may indicate the bidirectional interactions of Wnt signaling and YAP expression during neural tissue patterning, which have the significance in neurological disease modeling, drug screening, and neural tissue regeneration.

Generation of spatial-patterned early-developing cardiac organoids using human pluripotent stem cells

The creation of human induced pluripotent stem cells (hiPSCs) has provided an unprecedented opportunity to study tissue morphogenesis and organ development through 'organogenesis-in-a-dish'. Current approaches to cardiac organoid engineering rely on either direct cardiac differentiation from embryoid bodies (EBs) or generation of aligned cardiac tissues from predifferentiated cardiomyocytes from monolayer hiPSCs. To experimentally model early cardiac organogenesis in vitro, our protocol combines biomaterials-based cell patterning with stem cell organoid engineering. 3D cardiac microchambers are created from 2D hiPSC colonies; these microchambers approximate an early-development heart with distinct spatial organization and self-assembly. With proper training in photolithography microfabrication, maintenance of human pluripotent stem cells, and cardiac differentiation, a graduate student with guidance will likely be able to carry out this experimental protocol, which requires ∼3 weeks. We envisage that this in vitro model of human early heart development could serve as an embryotoxicity screening assay in drug discovery, regulation, and prescription for healthy fetal development. We anticipate that, when applied to hiPSC lines derived from patients with inherited diseases, this protocol can be used to study the disease mechanisms of cardiac malformations at an early stage of embryogenesis.

Derivation of Cortical Spheroids from Human Induced Pluripotent Stem Cells in a Suspension Bioreactor

Human induced pluripotent stem cells (hiPSCs) emerge as a promising source to construct human brain-like tissues, spheroids, or organoids in vitro for disease modeling and drug screening. A suspension bioreactor can be used to generate large size of brain organoids from hiPSCs through enhanced diffusion, but the influence of a dynamic bioreactor culture environment on neural tissue patterning from hiPSCs has not been well understood. The objective of this study is to assess the influence of a suspension bioreactor culture on cortical spheroid (i.e., forebrain-like aggregates) formation from hiPSCs. Single undifferentiated hiPSK3 cells or preformed embryoid bodies were inoculated into the bioreactor. Aggregate size distribution, neural marker expression (e.g., Nestin, PAX6, β-tubulin III, and MAP-2), and cortical tissue patterning markers (e.g., TBR1, BRN2, SATB2, and vGlut1) were evaluated with static control. Bioreactor culture was found to promote the expression of TBR1, a deep cortical layer VI marker, and temporally affect SATB2, a superficial cortical layer II-IV marker that appears later according to inside-out cortical tissue development. Prolonged culture after 70 days showed layer-specific cortical structure in the spheroids. Differential expression of matrix metalloproteinase-2 and -3 was also observed for bioreactor and static culture. The altered expression of cortical markers by a suspension bioreactor indicates the importance of culture environment on cortical tissue development from hiPSCs.

Low oxygen tension and macromolecular crowding accelerate extracellular matrix deposition in human corneal fibroblast culture

Development of implantable devices based on the principles of in vitro organogenesis has been hindered due to the prolonged time required to develop an implantable device. Herein we assessed the influence of serum concentration (0.5% and 10%), oxygen tension (0.5%, 2% and 20%) and macromolecular crowding (75 μg/ml carrageenan) in extracellular matrix deposition in human corneal fibroblast culture (3, 7 and 14 days). The highest extracellular matrix deposition was observed after 14 days in culture at 0.5% serum, 2% oxygen tension and 75 μg/ml carrageenan. These data indicate that low oxygen tension coupled with macromolecular crowding significantly accelerate the development of scaffold-free tissue-like modules. Copyright © 2016 John Wiley & Sons, Ltd.

Induced pluripotent stem cell technology: a decade of progress

Since the advent of induced pluripotent stem cell (iPSC) technology a decade ago, enormous progress has been made in stem cell biology and regenerative medicine. Human iPSCs have been widely used for disease modelling, drug discovery and cell therapy development. Novel pathological mechanisms have been elucidated, new drugs originating from iPSC screens are in the pipeline and the first clinical trial using human iPSC-derived products has been initiated. In particular, the combination of human iPSC technology with recent developments in gene editing and 3D organoids makes iPSC-based platforms even more powerful in each area of their application, including precision medicine. In this Review, we discuss the progress in applications of iPSC technology that are particularly relevant to drug discovery and regenerative medicine, and consider the remaining challenges and the emerging opportunities in the field.

Low, but not too low, oxygen tension and macromolecular crowding accelerate extracellular matrix deposition in human dermal fibroblast culture

A key challenge of in vitro organogenesis is the development in timely manner tissue equivalents. Herein, we assessed the simultaneous effect of oxygen tension (0.5%, 2% and 20%), foetal bovine serum concentration (0.5% and 10%) and macromolecular crowding (75μg/ml carrageenan) in human dermal fibroblast culture. Our data demonstrate that cells cultured at 2% oxygen tension, in the presence of carrageenan and at 0.5% serum concentration deposited within 3days in culture more extracellular matrix than cells grown for 14days, at 20% oxygen tension, 10% serum concentration and in the absence of carrageenan. These data suggest that optimal oxygen tension coupled with macromolecular crowding are important in vitro microenvironment modulators for accelerated development of tissue-like modules in vitro.

STATEMENT OF SIGNIFICANCE

To enable clinical translation and commercialisation of in vitro organogenesis therapies, we cultured human dermal fibroblast at 2% oxygen tension, under macromolecular crowding conditions (75μg/ml carrageenan) and at low foetal bovine serum concentration (0.5%). Within 3days in culture, more extracellular matrix was deposited under these conditions than cells grown for 14days, at 20% oxygen tension, 10% FBS concentration and in the absence of crowding agents. These data bring us closer to the development of more clinically relevant tissue-like modules.

Neural patterning of human induced pluripotent stem cells in 3-D cultures for studying biomolecule-directed differential cellular responses

INTRODUCTION

Appropriate neural patterning of human induced pluripotent stem cells (hiPSCs) is critical to generate specific neural cells/tissues and even mini-brains that are physiologically relevant to model neurological diseases. However, the capacity of signaling factors that regulate 3-D neural tissue patterning in vitro and differential responses of the resulting neural populations to various biomolecules have not yet been fully understood.

METHODS

By tuning neural patterning of hiPSCs with small molecules targeting sonic hedgehog (SHH) signaling, this study generated different 3-D neuronal cultures that were mainly comprised of either cortical glutamatergic neurons or motor neurons.

RESULTS

Abundant glutamatergic neurons were observed following the treatment with an antagonist of SHH signaling, cyclopamine, while Islet-1 and HB9-expressing motor neurons were enriched by an SHH agonist, purmorphamine. In neurons derived with different neural patterning factors, whole-cell patch clamp recordings showed similar voltage-gated Na(+)/K(+) currents, depolarization-evoked action potentials and spontaneous excitatory post-synaptic currents. Moreover, these different neuronal populations exhibited differential responses to three classes of biomolecules, including (1) matrix metalloproteinase inhibitors that affect extracellular matrix remodeling; (2) N-methyl-d-aspartate that induces general neurotoxicity; and (3) amyloid β (1-42) oligomers that cause neuronal subtype-specific neurotoxicity.

CONCLUSIONS

This study should advance our understanding of hiPSC self-organization and neural tissue development and provide a transformative approach to establish 3-D models for neurological disease modeling and drug discovery.

STATEMENT OF SIGNIFICANCE

Appropriate neural patterning of human induced pluripotent stem cells (hiPSCs) is critical to generate specific neural cells, tissues and even mini-brains that are physiologically relevant to model neurological diseases. However, the capability of sonic hedgehog-related small molecules to tune different neuronal subtypes in 3-D differentiation from hiPSCs and the differential cellular responses of region-specific neuronal subtypes to various biomolecules have not been fully investigated. By tuning neural patterning of hiPSCs with small molecules targeting sonic hedgehog signaling, this study provides knowledge on the differential susceptibility of region-specific neuronal subtypes derived from hiPSCs to different biomolecules in extracellular matrix remodeling and neurotoxicity. The findings are significant for understanding 3-D neural patterning of hiPSCs for the applications in brain organoid formation, neurological disease modeling, and drug discovery.

Biology-inspired microphysiological system approaches to solve the prediction dilemma of substance testing

The recent advent of microphysiological systems - microfluidic biomimetic devices that aspire to emulate the biology of human tissues, organs and circulation in vitro - is envisaged to enable a global paradigm shift in drug development. An extraordinary US governmental initiative and various dedicated research programs in Europe and Asia have led recently to the first cutting-edge achievements of human single-organ and multi-organ engineering based on microphysiological systems. The expectation is that test systems established on this basis would model various disease stages, and predict toxicity, immunogenicity, ADME profiles and treatment efficacy prior to clinical testing. Consequently, this technology could significantly affect the way drug substances are developed in the future. Furthermore, microphysiological system-based assays may revolutionize our current global programs of prioritization of hazard characterization for any new substances to be used, for example, in agriculture, food, ecosystems or cosmetics, thus, replacing laboratory animal models used currently. Thirty-six experts from academia, industry and regulatory bodies present here the results of an intensive workshop (held in June 2015, Berlin, Germany). They review the status quo of microphysiological systems available today against industry needs, and assess the broad variety of approaches with fit-for-purpose potential in the drug development cycle. Feasible technical solutions to reach the next levels of human biology in vitro are proposed. Furthermore, key organ-on-a-chip case studies, as well as various national and international programs are highlighted. Finally, a roadmap into the future is outlined, to allow for more predictive and regulatory-accepted substance testing on a global scale.

Challenges in understanding psychiatric disorders and developing therapeutics: a role for zebrafish

The treatment of psychiatric disorders presents three major challenges to the research and clinical community: defining a genotype associated with a disorder, characterizing the molecular pathology of each disorder and developing new therapies. This Review addresses how cellular and animal systems can help to meet these challenges, with an emphasis on the role of the zebrafish. Genetic changes account for a large proportion of psychiatric disorders and, as gene variants that predispose to psychiatric disease are beginning to be identified in patients, these are tractable for study in cellular and animal systems. Defining cellular and molecular criteria associated with each disorder will help to uncover causal physiological changes in patients and will lead to more objective diagnostic criteria. These criteria should also define co-morbid pathologies within the nervous system or in other organ systems. The definition of genotypes and of any associated pathophysiology is integral to the development of new therapies. Cell culture-based approaches can address these challenges by identifying cellular pathology and by high-throughput screening of gene variants and potential therapeutics. Whole-animal systems can define the broadest function of disorder-associated gene variants and the organismal impact of candidate medications. Given its evolutionary conservation with humans and its experimental tractability, the zebrafish offers several advantages to psychiatric disorder research. These include assays ranging from molecular to behavioural, and capability for chemical screening. There is optimism that the multiple approaches discussed here will link together effectively to provide new diagnostics and treatments for psychiatric patients.

Summary: In this review, we discuss strengths and limitations of prevalent laboratory models that are used for understanding psychiatric disorders and developing therapeutics, with emphasis on the zebrafish.

Generation of Neural Progenitor Spheres from Human Pluripotent Stem Cells in a Suspension Bioreactor

Conventional two-dimensional (2-D) culture systems cannot provide large numbers of human pluripotent stem cells (hPSCs) and their derivatives that are demanded for commercial and clinical applications in in vitro drug screening, disease modeling, and potentially cell therapy. The technologies that support three-dimensional (3-D) suspension culture, such as a stirred bioreactor, are generally considered as promising approaches to produce the required cells. Recently, suspension bioreactors have also been used to generate mini-brain-like structure from hPSCs for disease modeling, showing the important role of bioreactor in stem cell culture. This chapter describes a detailed culture protocol for neural commitment of hPSCs into neural progenitor cell (NPC) spheres using a spinner bioreactor. The basic steps to prepare hPSCs for bioreactor inoculation are illustrated from cell thawing to cell propagation. The method for generating NPCs from hPSCs in the spinner bioreactor along with the static control is then described. The protocol in this study can be applied to the generation of NPCs from hPSCs for further neural subtype specification, 3-D neural tissue development, or potential preclinical studies or clinical applications in neurological diseases.

Scaffold and scaffold-free self-assembled systems in regenerative medicine

Self-assembly in tissue engineering refers to the spontaneous chemical or biological association of components to form a distinct functional construct, reminiscent of native tissue. Such self-assembled systems have been widely used to develop platforms for the delivery of therapeutic and/or bioactive molecules and various cell populations. Tissue morphology and functional characteristics have been recapitulated in several self-assembled constructs, designed to incorporate stimuli responsiveness and controlled architecture through spatial confinement or field manipulation. In parallel, owing to substantial functional properties, scaffold-free cell-assembled devices have aided in the development of functional neotissues for various clinical targets. Herein, we discuss recent advancements and future aspirations in scaffold and scaffold-free self-assembled devices for regenerative medicine purposes. Biotechnol. Bioeng. 2016;113: 1155-1163. © 2015 Wiley Periodicals, Inc.