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Alzheimer's disease (AD) is characterized by beta-amyloid accumulation, phosphorylated tau formation, hyperactivation of glial cells, and neuronal loss. The mechanisms of AD pathogenesis, however, remain poorly understood, partially due to the lack of relevant models that can comprehensively recapitulate multistage intercellular interactions in human AD brains. Here we present a new three-dimensional (3D) human AD triculture model using neurons, astrocytes, and microglia in a 3D microfluidic platform. Our model provided key representative AD features: beta-amyloid aggregation, phosphorylated tau accumulation, and neuroinflammatory activity. In particular, the model mirrored microglial recruitment, neurotoxic activities such as axonal cleavage, and NO release damaging AD neurons and astrocytes. Our model will serve to facilitate the development of more precise human brain models for basic mechanistic studies in neural-glial interactions and drug discovery.

Stem cell technologies have facilitated the development of human cellular disease models that can be used to study pathogenesis and test therapeutic candidates. These models hold promise for complex neurological diseases such as Alzheimer’s disease (AD) because existing animal models have been unable to fully recapitulate all aspects of pathology. We recently reported the characterization of a novel three-dimensional (3D) culture system that exhibits key events in AD pathogenesis, including extracellular aggregation of β-amyloid and accumulation of hyperphosphorylated tau. Here we provide instructions for the generation and analysis of 3D human neural cell cultures, including the production of genetically modified human neural progenitor cells (hNPCs) with familial AD mutations, the differentiation of the hNPCs in a 3D matrix, and the analysis of AD pathogenesis. The 3D culture generation takes 1–2 days. The aggregation of β-amyloid is observed after 6-weeks of differentiation followed by robust tau pathology after 10–14 weeks.

Summary Alzheimer’s disease (AD) is the most common cause of dementia, and there is currently no cure. The “β-amyloid cascade hypothesis” of AD is the basis of current understanding of AD pathogenesis and drug discovery. However, no AD models have fully validated this hypothesis. We recently developed a human stem cell culture model of AD by cultivating genetically modified human neural stem cells in a three-dimensional (3D) cell culture system. These cells were able to recapitulate key events of AD pathology including β-amyloid plaques and neurofibrillary tangles. In this review, we will discuss the progress and current limitations of AD mouse models and human stem cell models as well as explore the breakthroughs of 3D cell culture systems. We will also share our perspective on the potential of dish models of neurodegenerative diseases for studying pathogenic cascades and therapeutic drug discovery.

Neurospheroids are commonly used for in vitro disease modeling and drug screening. However, the heterogeneity in size of the neurospheroids mixtures available through current methods limits their utility when employed for basic mechanistic studies of neurodegenerative diseases or screening for new interventions. Here, we generate neurospheroids from immortalized neural progenitor cells and human induced pluripotent stem cells that are uniform in size, into large-scale arrays. In proof of concept experiments, we validate the neurospheroids array as a sensitive and robust tool for screening compounds over extended time. We show that when suspended in three-dimensional extracellular matrix up to several weeks, the stem cell-derived neurospheroids display extensive neurite outgrowth and extend thick bundles of dendrites outward. We also cultivate genetically-engineered stem cell-derived neurospheroids with familial Alzheimer’s disease mutations for eight weeks in our microarray system. Interestingly, we observed robust accumulation of amyloid-β and phosphorylated tau, key hallmarks of Alzheimer’s disease. Overall, our in vitro model for engineering neurospheroid arrays is a valuable tool for studying complex neurodegenerative diseases and accelerating drug discovery.

Changes in intracellular [Ca 2 þ ] i levels have been shown to influence developmental processes that accompany the transition of human oligodendrocyte precursor cells (OPCs) into mature myelinating oligodendrocytes and are required for the initiation of the myelination and re-myelination processes. In the present study, we explored whether calcium signals mediated by the selective sodium calcium exchanger (NCX) family members NCX1, NCX2, and NCX3, play a role in oligodendrocyte maturation. Functional studies, as well as mRNA and protein expression analyses, revealed that NCX1 and NCX3, but not NCX2, were divergently modulated during OPC differentiation into oligodendrocyte phenotype. In fact, whereas NCX1 was downregulated, NCX3 was strongly upregulated during oligodendrocyte development. The importance of calcium signaling mediated by NCX3 during oligodendrocyte maturation was supported by several findings. Indeed, whereas knocking down the NCX3 isoform in OPCs prevented the upregulation of the myelin protein markers 2 0 ,3 0 -cyclic nucleotide-3 0 -phosphodiesterase (CNPase) and myelin basic protein (MBP), its overexpression induced an upregulation of CNPase and MBP. Furthermore, NCX3-knockout mice showed not only a reduced size of spinal cord but also marked hypo-myelination, as revealed by decrease in MBP expression and by an accompanying increase in OPC number. Collectively, our findings indicate that calcium signaling mediated by NCX3 has a crucial role in oligodendrocyte maturation and myelin formation. Oligodendrocytes, the myelin-forming cells of the CNS, arise from oligodendrocyte precursor cells (OPCs) that colonize both the gray and the white brain matter during development. 1 Although many OPCs differentiate into mature myelinating oligodendrocytes during the early and much later stages of human brain development, a considerable number of them do persist in the adult brain, and may provide a source of new oligodendrocytes, as well as protoplasmic astrocytes and neurons. 2,3 Because of their apparent stem-like characteristics, adult OPCs have recently gained much attention, for they are regarded as a potential reservoir of cells capable of self-renewal, differentiation, and re-myelination after CNS injury. 4 Thus, understanding how oligodendrocyte development proceeds and what factors govern the differentiation fate of OPCs is crucial to discover new effective therapeutic targets for de-myelinating diseases such as multiple sclerosis (MS).Changes in intracellular calcium levels have a critical role in OPC migration, lineage progression, and differentiation; furthermore, they are required for myelination and remyelination processes. [5][6][7] The Na þ /Ca 2 þ exchanger (NCX), 8 a transmembrane domain protein, which, by operating in a bidirectional way, couples the efflux of Ca 2 þ to the influx of Na þ into the cell or, vice versa, the influx of Ca 2 þ to the efflux of Na þ , is involved in the regulation of diverse neuronal and glial cell functions. 8,9 Furthermore, NCX is involved in regulating int...

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Deciphering the human brain pathophysiology remains one of the greatest challenges of the 21st century. Neurological disorders represent a significant proportion of diseases burden; however, the complexity of the brain physiology makes it challenging to model its diseases. Simple in vitro models have been very useful for precise measurements in controled conditions. However, existing models are limited in their ability to replicate complex interactions between various cells in the brain. Studying human brain requires sophisticated models to reconstitute the tangled architecture and functions of brain cells. Recently, advances in the development of three-dimensional (3D) brain cell culture models have begun to recapitulate various aspects of the human brain physiology in vitro and replicate basic disease processes of Alzheimer’s disease, amyotrophic lateral sclerosis, and microcephaly. In this review, we discuss the progress, advantages, limitations, and future directions of 3D cell culture systems for modeling the human brain development and diseases.