A Human Brain-Chip for Modeling Brain Pathologies and Screening Blood–Brain Barrier Crossing Therapeutic Strategies

Organ Model: Brain (BBB)

Application: ADME, Inflammation

Abstract: The limited translatability of preclinical experimental findings to patients remains an obstacle for successful treatment of brain diseases. Relevant models to elucidate mechanisms behind brain pathogenesis, including cell-specific contributions and cell-cell interactions, and support successful targeting and prediction of drug responses in humans are urgently needed, given the species differences in brain and blood-brain barrier (BBB) functions. Human microphysiological systems (MPS), such as Organ-Chips, are emerging as a promising approach to address these challenges. Here, we examined and advanced a Brain-Chip that recapitulates aspects of the human cortical parenchyma and the BBB in one model. 

Methods: We utilized human primary astrocytes and pericytes, human induced pluripotent stem cell (hiPSC)-derived cortical neurons, and hiPSC-derived brain microvascular endothelial-like cells and included for the first time on-chip hiPSC-derived microglia. 

Results: Using Tumor necrosis factor alpha (TNFα) to emulate neuroinflammation, we demonstrate that our model recapitulates in vivo-relevant responses. Importantly, we show microglia-derived responses, highlighting the Brain-Chip’s sensitivity to capture cell-specific contributions in human disease-associated pathology. We then tested BBB crossing of human transferrin receptor antibodies and conjugated adeno-associated viruses. We demonstrate successful in vitro/in vivo correlation in identifying crossing differences, underscoring the model’s capacity as a screening platform for BBB crossing therapeutic strategies and ability to predict in vivo responses. Conclusions: These findings highlight the potential of the Brain-Chip as a reliable and time-efficient model to support therapeutic development and provide mechanistic insights into brain diseases, adding to the growing evidence supporting the value of MPS in translational research and drug discovery.

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Evaluation of Drug Blood-Brain-Barrier Permeability Using a Microfluidic Chip

Organ Model: Brain (Blood Brain Barrier)

Application: Neuroscience, ADME

Abstract: The blood-brain-barrier (BBB) is made up of blood vessels whose permeability enables the passage of some compounds. A predictive model of BBB permeability is important in the early stages of drug development. The predicted BBB permeabilities of drugs have been confirmed using a variety of in vitro methods to reduce the quantities of drug candidates needed in preclinical and clinical trials. Most prior studies have relied on animal or cell-culture models, which do not fully recapitulate the human BBB. The development of microfluidic models of human-derived BBB cells could address this issue. We analyzed a model for predicting BBB permeability using the Emulate BBB-on-a-chip machine. Ten compounds were evaluated, and their permeabilities were estimated. Our study demonstrated that the permeability trends of ten compounds in our microfluidic-based system resembled those observed in previous animal and cell-based experiments. Furthermore, we established a general correlation between the partition coefficient (𝐾𝑝) and the apparent permeability (𝑃𝑎𝑝𝑝). In conclusion, we introduced a new paradigm for predicting BBB permeability using microfluidic-based systems.

Organ-Chips Enhance the Maturation of Human iPSC-Derived Dopamine Neurons

Organ Model: Brain

Application: Neuroscience

Abstract: While cells in the human body function in an environment where the blood supply constantly delivers nutrients and removes waste, cells in conventional tissue culture well platforms are grown with a static pool of media above them and often lack maturity, limiting their utility to study cell biology in health and disease. In contrast, organ-chip microfluidic systems allow the growth of cells under constant flow, more akin to the in vivo situation. Here, we differentiated human induced pluripotent stem cells into dopamine neurons and assessed cellular properties in conventional multi-well cultures and organ-chips. We show that organ-chip cultures, compared to multi-well cultures, provide an overall greater proportion and homogeneity of dopaminergic neurons as well as increased levels of maturation markers. These organ-chips are an ideal platform to study mature dopamine neurons to better understand their biology in health and ultimately in neurological disorders.

Evaluation of a Human Neurovascular Model to Complement a Parallel Non-human Primate Selection for Blood–Brain Barrier Penetrant AAV Capsids

INTRODUCTION

  • Delivery of genomic medicine to the central nervous system (CNS) is a major hurdle for clinical applications of gene therapy; the blood–brain barrier (BBB) limits the brain distribution of virtually all intravenously administered macromolecules.
  • Several adeno-associated virus (AAV) serotypes, most notably AAV9, distribute to the brain after intravenous (IV) administration but require high doses to achieve limited expression.
  • AAV capsid engineering has produced novel variants that are superior to their parental serotypes and have progressed into the clinic for several indications. However, translation of clinical programs from preclinical models to humans remains a challenge for the entire gene therapy field, including capsid engineering efforts.
    • Two factors for a stringent selection campaign have emerged: library designs that incorporate functional cellular transduction pressure, and selection of appropriate in vitro and/or in vivo models.
  • In this study, we employed SIFTER™ (Selecting In vivo For Transduction and Expression of RNA) to engineer capsids with improved CNS transduction following IV administration in Cynomolgus macaque (non-human primates [NHPs]). This was followed by implementation of an all human cell model of the BBB that recapitulates many key BBB properties to address discordant capsid performance observed in vitro vs in vivo and between species.

A Microengineered Brain-Chip to Model Neuroinflammation in Humans

iScience (2022)

Abstract

Species differences in brain and blood-brain barrier (BBB) biology hamper translation from findings in animal models to humans. This, in turn, impedes the development of medicines and brain diseases. Researchers from Emulate developed a human Brain-Chip that contains endothelial-like cells, pericytes, glia, and cortical neurons while maintaining BBB permeability at in vivo-relevant levels. With these features, the model is able to closely recapitulate neuroinflammation, allowing scientists to gain a mechanistic understanding of cell-cell interactions and BBB function during neuroinflammation with greater accuracy than they could with conventional models of the human brain.

Modeling alpha-synuclein pathology in a human Brain-Chip to assess blood-brain barrier disruption

Nature Communications (2021)

Abstract

Parkinson’s disease and related synucleinopathies are characterized by the abnormal accumulation of alpha-synuclein aggregates, loss of dopaminergic neurons, and gliosis of the substantia nigra. Although clinical evidence and in vitro studies indicate disruption of the Blood-Brain Barrier in Parkinson’s disease, the mechanisms mediating the endothelial dysfunction is not well understood. Here we leveraged the Organs-on-Chips technology to develop a human Brain-Chip representative of the substantia nigra area of the brain containing dopaminergic neurons, astrocytes, microglia, pericytes, and microvascular brain endothelial cells, cultured under fluid flow. Our αSyn fibril-induced model was capable of reproducing several key aspects of Parkinson’s disease, including accumulation of phosphorylated αSyn (pSer129-αSyn), mitochondrial impairment, neuroinflammation, and compromised barrier function. This model may enable research into the dynamics of cell-cell interactions in human synucleinopathies and serve as a testing platform for target identification and validation of novel therapeutics.

Development of a Human Brain-Chip Model to Study Neuroinflammatory Diseases

Abstract

Species differences in brain function and blood-brain barrier often preclude accurate extrapolation from animal models to human patients. There is an unmet need for human relevant systems that can recreate key aspects of brain physiology and pathophysiology of common diseases. We are developing a human Brain-Chip to model neuroinflammation, a hallmark of many neurodegenerative diseases, to enable studies on mechanistic aspects of neural pathology and disease progression. We provide evidence that this complex human Brain-Chip model can support co-culture and establishment of extensive interconnection between human iPSC-derived neurons and primary glia cells (astrocytes and microglia). Human iPSC-derived brain endothelial cells successfully maintained at the vascular channel of the Brain-Chip in the presence of fluidic shear stress, while exhibiting hallmark features of the human blood-brain barrier, such as development of specific tight junctions and minimal barrier permeability. Exposure to inflammatory triggers (e.g. TNF-α) or toxic protein oligomeric species (e.g. alpha-synuclein), resulted in neuronal death, glia activation, increased secretion of the corresponding proinflammatory cytokines, and a compromised barrier function. In summary, our current findings demonstrate the development of a human Brain-Chip that could support the development of models for the study of neuroinflammation and blood-brain barrier disfunction in neurological disorders.

Generation of a Human iPSC-Based Blood-Brain Barrier Chip

Organ Model: Brain (BBB)

Applications: Neuroscience

Abstract: The blood brain barrier (BBB) is formed by neurovascular units (NVUs) that shield the central nervous system (CNS) from a range of factors found in the blood that can disrupt delicate brain function. As such, the BBB is a major obstacle to the delivery of therapeutics to the CNS. Accumulating evidence suggests that the BBB plays a key role in the onset and progression of neurological diseases. Thus, there is a tremendous need for a BBB model that can predict penetration of CNS-targeted drugs as well as elucidate the BBB’s role in health and disease. We have recently combined organ-on-chip and induced pluripotent stem cell (iPSC) technologies to generate a BBB chip fully personalized to humans. This novel platform displays cellular, molecular, and physiological properties that are suitable for the prediction of drug and molecule transport across the human BBB. Furthermore, using patient-specific BBB chips, we have generated models of neurological disease and demonstrated the potential for personalized predictive medicine applications. Provided here is a detailed protocol demonstrating how to generate iPSC-derived BBB chips, beginning with differentiation of iPSC-derived brain microvascular endothelial cells (iBMECs) and resulting in mixed neural cultures containing neural progenitors, differentiated neurons, and astrocytes. Also described is a procedure for seeding cells into the organ chip and culturing of the BBB chips under controlled laminar flow. Lastly, detailed descriptions of BBB chip analyses are provided, including paracellular permeability assays for assessing drug and molecule permeability as well as immunocytochemical methods for determining the composition of cell types within the chip.

Human iPSC-Derived Blood-Brain Barrier Chips Enable Disease Modeling and Personalized Medicine Applications

Organ Model: Brain (BBB)

Application: Neuroscience

Abstract: The blood-brain barrier (BBB) tightly regulates the entry of solutes from blood into the brain and is disrupted in several neurological diseases. Using Organ-Chip technology, we created an entirely human BBB-Chip with induced pluripotent stem cell (iPSC)-derived brain microvascular endothelial-like cells (iBMECs), astrocytes, and neurons. The iBMECs formed a tight monolayer that expressed markers specific to brain vasculature. The BBB-Chip exhibited physiologically relevant transendothelial electrical resistance and accurately predicted blood-to-brain permeability of pharmacologics. Upon perfusing the vascular lumen with whole blood, the microengineered capillary wall protected neural cells from plasma-induced toxicity. Patient-derived iPSCs from individuals with neurological diseases predicted disease-specific lack of transporters and disruption of barrier integrity. By combining Organ-Chip technology and human iPSC-derived tissue, we have created a neurovascular unit that recapitulates complex BBB functions, provides a platform for modeling inheritable neurological disorders, and advances drug screening, as well as personalized medicine.

Human iPSC-Derived Endothelial Cells and Microengineered Organ-Chip Enhance Neuronal Development

Published in: Stem Cell Reports

Abstract

Human stem cell-derived models of development and neurodegenerative diseases are challenged by cellular immaturity in vitro. Microengineered organ-on-chip (or Organ-Chip) systems are designed to emulate microvolume cytoarchitecture and enable co-culture of distinct cell types. Brain microvascular endothelial cells (BMECs) share common signaling pathways with neurons early in development, but their contribution to human neuronal maturation is largely unknown. To study this interaction and influence of microculture, we derived both spinal motor neurons and BMECs from human induced pluripotent stem cells and observed increased calcium transient function and Chip-specific gene expression in Organ-Chips compared with 96-well plates. Seeding BMECs in the Organ-Chip led to vascular-neural interaction and specific gene activation that further enhanced neuronal function and in vivo-like signatures. The results show that the vascular system has specific maturation effects on spinal cord neural tissue, and the use of Organ-Chips can move stem cell models closer to an in vivo condition.