Three Dimensional Human Neuro-Spheroid Model of Alzheimer's Disease Based on Differentiated Induced Pluripotent Stem Cells. PLoS One. 2016;11:e0163072. [PMID: 27684569 PMCID: PMC5042502 DOI: 10.1371/journal.pone.0163072]

Common proteomic profiles of induced pluripotent stem cell-derived three-dimensional neurons and brain tissue from Alzheimer patients

We established a unique platform for proteomic analysis of cultured three-dimensional (3D) neurons and brain tissue from Alzheimer's disease (AD) patients. We collected peripheral blood mononuclear cells (PBMC), converted PBMC to induced pluripotent stem cell (iPSC) lines, and differentiated the iPSC into human 3D neuro-spheroids. The postmortem brain tissue from the superior frontal cortex, inferior frontal cortex and cerebellum area of the AD patients was compared to the same regions from the control subjects. Proteomic analysis of 3D neuro-spheroids derived from AD subjects revealed the alteration of a number of proteins involved in axon growth, mitochondrial function, and antioxidant defense. Similar analysis of post-mortem AD brain tissue revealed significant alteration in proteins involved in oxidative stress, neuro-inflammation, along with proteins related to axonal injury. These results clearly indicate that the dysfunction of 3D neurons from AD patients in our in vitro environment is comparable to the post-mortem AD brain tissue in vivo. In conclusion, our study revealed a number of candidate proteins that have important implications in AD pathogenesis and supports the notion that the iPSC-derived 3D neuronal system functions as a model to examine novel aspects of AD pathology.

SIGNIFICANCE

In this study, we present a unique platform for proteomic analysis of induced pluripotent stem cell-derived three dimensional (3D) neurons and compare the results to those from three regions of post-mortem brain tissue from Alzheimer's disease patients and normal control subjects. Our results show that the dysfunction of 3D neurons from AD patients in our in vitro environment is comparable to the post-mortem AD brain tissue in vivo. Our results revealed several candidate proteins that have important implications in AD pathogenesis.

Materials for Neural Differentiation, Trans-Differentiation, and Modeling of Neurological Disease

Neuron regeneration from pluripotent stem cells (PSCs) differentiation or somatic cells trans-differentiation is a promising approach for cell replacement in neurodegenerative diseases and provides a powerful tool for investigating neural development, modeling neurological diseases, and uncovering the mechanisms that underlie diseases. Advancing the materials that are applied in neural differentiation and trans-differentiation promotes the safety, efficiency, and efficacy of neuron regeneration. In the neural differentiation process, matrix materials, either natural or synthetic, not only provide a structural and biochemical support for the monolayer or three-dimensional (3D) cultured cells but also assist in cell adhesion and cell-to-cell communication. They play important roles in directing the differentiation of PSCs into neural cells and modeling neurological diseases. For the trans-differentiation of neural cells, several materials have been used to make the conversion feasible for future therapy. Here, the most current applications of materials for neural differentiation for PSCs, neuronal trans-differentiation, and neurological disease modeling is summarized and discussed.

Genome engineering for CNS injury and disease

Recent developments in genome engineering methods have advanced our knowledge of central nervous system (CNS) function in both normal health and following disease or injury. This review discusses current literature using gene editing tools in CNS disease and injury research, such as improving viral-mediated targeting of cell populations, generating new methods for genome editing, reprogramming cells into CNS cell types, and using organoids as models of development and disease. Readers may gain inspiration for continuing research into new genome engineering methods and for therapies for CNS applications.

Recent Advances: Decoding Alzheimer's Disease With Stem Cells

Alzheimer’s disease (AD) is an irreversible neurodegenerative disorder that destroys cognitive functions. Recently, a number of high-profile clinical trials based on the amyloid cascade hypothesis have encountered disappointing results. The failure of these trials indicates the necessity for novel therapeutic strategies and disease models. In this review, we will describe how recent advances in stem cell technology have shed light on a novel treatment strategy and revolutionized the mechanistic investigation of AD pathogenesis. Current advances in promoting endogenous neurogenesis and transplanting exogenous stem cells from both bench research and clinical translation perspectives will be thoroughly summarized. In addition, reprogramming technology-based disease modeling, which has shown improved efficacy in recapitulating pathological features in human patients, will be discussed.

Modeling Neurodegenerative Microenvironment Using Cortical Organoids Derived from Human Stem Cells

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders and causes cognitive impairment and memory deficits of the patients. The mechanism of AD is not well known, due to lack of human brain models. Recently, mini-brain tissues called organoids have been derived from human induced pluripotent stem cells (hiPSCs) for modeling human brain development and neurological diseases. Thus, the objective of this research is to model and characterize neural degeneration microenvironment using three-dimensional (3D) forebrain cortical organoids derived from hiPSCs and study the response to the drug treatment. It is hypothesized that the 3D forebrain organoids derived from hiPSCs with AD-associated genetic background may partially recapitulate the extracellular microenvironment in neural degeneration. To test this hypothesis, AD-patient derived hiPSCs with presenilin-1 mutation were used for cortical organoid generation. AD-related inflammatory responses, matrix remodeling and the responses to DAPT, heparin (completes with heparan sulfate proteoglycans [HSPGs] to bind Aβ42), and heparinase (digests HSPGs) treatments were investigated. The results indicate that the cortical organoids derived from AD-associated hiPSCs exhibit a high level of Aβ42 comparing with healthy control. In addition, the AD-derived organoids result in an elevated gene expression of proinflammatory cytokines interleukin-6 and tumor necrosis factor-α, upregulate syndecan-3, and alter matrix remodeling protein expression. Our study demonstrates the capacity of hiPSC-derived organoids for modeling the changes of extracellular microenvironment and provides a potential approach for AD-related drug screening.

Representing Diversity in the Dish: Using Patient-Derived in Vitro Models to Recreate the Heterogeneity of Neurological Disease

Neurological diseases, including dementias such as Alzheimer's disease (AD) and fronto-temporal dementia (FTD) and degenerative motor neuron diseases such as amyotrophic lateral sclerosis (ALS), are responsible for an increasing fraction of worldwide fatalities. Researching these heterogeneous diseases requires models that endogenously express the full array of genetic and epigenetic factors which may influence disease development in both familial and sporadic patients. Here, we discuss the two primary methods of developing patient-derived neurons and glia to model neurodegenerative disease: reprogramming somatic cells into induced pluripotent stem cells (iPSCs), which are differentiated into neurons or glial cells, or directly converting (DC) somatic cells into neurons (iNeurons) or glial cells. Distinct differentiation techniques for both models result in a variety of neuronal and glial cell types, which have been successful in displaying unique hallmarks of a variety of neurological diseases. Yield, length of differentiation, ease of genetic manipulation, expression of cell-specific markers, and recapitulation of disease pathogenesis are presented as determining factors in how these methods may be used separately or together to ascertain mechanisms of disease and identify therapeutics for distinct patient populations or for specific individuals in personalized medicine projects.

Human Neurospheroid Arrays for In Vitro Studies of Alzheimer's Disease

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.

Three-Dimensional Models of the Human Brain Development and Diseases

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.

Microdevice Platform for In Vitro Nervous System and Its Disease Model

The development of precise microdevices can be applied to the reconstruction of in vitro human microenvironmental systems with biomimetic physiological conditions that have highly tunable spatial and temporal features. Organ-on-a-chip can emulate human physiological functions, particularly at the organ level, as well as its specific roles in the body. Due to the complexity of the structure of the central nervous system and its intercellular interaction, there remains an urgent need for the development of human brain or nervous system models. Thus, various microdevice models have been proposed to mimic actual human brain physiology, which can be categorized as nervous system-on-a-chip. Nervous system-on-a-chip platforms can prove to be promising technologies, through the application of their biomimetic features to the etiology of neurodegenerative diseases. This article reviews the microdevices for nervous system-on-a-chip platform incorporated with neurobiology and microtechnology, including microfluidic designs that are biomimetic to the entire nervous system. The emulation of both neurodegenerative disorders and neural stem cell behavior patterns in micro-platforms is also provided, which can be used as a basis to construct nervous system-on-a-chip.

Key Aging-Associated Alterations in Primary Microglia Response to Beta-Amyloid Stimulation

Alzheimer's disease (AD) is characterized by a progressive cognitive decline and believed to be driven by the self-aggregation of amyloid-β (Aβ) peptide into oligomers and fibrils that accumulate as senile plaques. It is widely accepted that microglia-mediated inflammation is a significant contributor to disease pathogenesis; however, different microglia phenotypes were identified along AD progression and excessive Aβ production was shown to dysregulate cell function. As so, the contribution of microglia to AD pathogenesis remains to be elucidated. In this study, we wondered if isolated microglia cultured for 16 days in vitro (DIV) would react differentially from the 2 DIV cells upon treatment with 1000 nM Aβ_1-42 for 24 h. No changes in cell viability were observed and morphometric alterations associated to microglia activation, such as volume increase and process shortening, were obvious in 2 DIV microglia, but less evident in 16 DIV cells. These cells showed lower phagocytic, migration and autophagic properties after Aβ treatment than the 2 DIV cultured microglia. Reduced phagocytosis may derive from increased CD33 expression, reduced triggering receptor expressed on myeloid cells 2 (TREM2) and milk fat globule-EGF factor 8 protein (MFG-E8) levels, which were mainly observed in 16 DIV cells. Activation of inflammatory mediators, such as high mobility group box 1 (HMGB1) and pro-inflammatory cytokines, as well as increased expression of Toll-like receptor 2 (TLR2), TLR4 and fractalkine/CX3C chemokine receptor 1 (CX3CR1) cell surface receptors were prominent in 2 DIV microglia, while elevation of matrix metalloproteinase 9 (MMP9) was marked in 16 DIV cells. Increased senescence-associated β-galactosidase (SA-β-gal) and upregulated miR-146a expression that were observed in 16 DIV cells showed to increase by Aβ in 2 DIV microglia. Additionally, Aβ downregulated miR-155 and miR-124, and reduced the CD11b+ subpopulation in 2 DIV microglia, while increased the number of CD86+ cells in 16 DIV microglia. Simultaneous M1 and M2 markers were found after Aβ treatment, but at lower expression in the in vitro aged microglia. Data show key-aging associated responses by microglia when incubated with Aβ, with a loss of reactivity from the 2 DIV to the 16 DIV cells, which course with a reduced phagocytosis, migration and lower expression of inflammatory miRNAs. These findings help to improve our understanding on the heterogeneous responses that microglia can have along the progression of AD disease and imply that therapeutic approaches may differ from early to late stages.

Generating CNS organoids from human induced pluripotent stem cells for modeling neurological disorders

Understanding human brain development and disease is largely hampered by the relative inaccessibility of human brain tissues. Recent advances in human induced pluripotent stem cells (hiPSCs) have led to the generation of unlimited human neural cells and thereby facilitate the investigation of human brain development and pathology. Compared with traditional 2-dimensional (2D) culture methods, culturing the hiPSC-derived neural cells in a three-dimensional (3D) free-floating manner generates human central nervous system (CNS) organoids. These 3D CNS organoids possess the unique advantage of recapitulating multi-regional or region-specific cytoarchitecture seen in the early human fetal brain development. The CNS organoids are becoming a strong complement to the animal model in studying brain development and pathology, and developing new therapies to treat neurodevelopmental diseases. Further improvements to the long-term maintenance and neural maturation of the organoids may allow them to model neurodegenerative diseases. In this review, we will summarize the current development of hiPSCs to generate CNS organoids for modeling neurological disorders and future perspective.

Stem cell models of Alzheimer's disease: progress and challenges

A major challenge to our understanding of the molecular mechanisms of Alzheimer’s disease (AD) has been the lack of physiologically relevant in vitro models which capture the precise patient genome, in the cell type of interest, with physiological expression levels of the gene(s) of interest. Induced pluripotent stem cell (iPSC) technology, together with advances in 2D and 3D neuronal differentiation, offers a unique opportunity to overcome this challenge and generate a limitless supply of human neurons for in vitro studies. iPSC-neuron models have been widely employed to model AD and we discuss in this review the progress that has been made to date using patient-derived neurons to recapitulate key aspects of AD pathology and how these models have contributed to a deeper understanding of AD molecular mechanisms, as well as addressing the key challenges posed by using this technology and what progress is being made to overcome these. Finally, we highlight future directions for the use of iPSC-neurons in AD research and highlight the potential value of this technology to neurodegenerative research in the coming years.

3D culture models of Alzheimer's disease: a road map to a "cure-in-a-dish"

Alzheimer's disease (AD) transgenic mice have been used as a standard AD model for basic mechanistic studies and drug discovery. These mouse models showed symbolic AD pathologies including β-amyloid (Aβ) plaques, gliosis and memory deficits but failed to fully recapitulate AD pathogenic cascades including robust phospho tau (p-tau) accumulation, clear neurofibrillary tangles (NFTs) and neurodegeneration, solely driven by familial AD (FAD) mutation(s). Recent advances in human stem cell and three-dimensional (3D) culture technologies made it possible to generate novel 3D neural cell culture models that recapitulate AD pathologies including robust Aβ deposition and Aβ-driven NFT-like tau pathology. These new 3D human cell culture models of AD hold a promise for a novel platform that can be used for mechanism studies in human brain-like environment and high-throughput drug screening (HTS). In this review, we will summarize the current progress in recapitulating AD pathogenic cascades in human neural cell culture models using AD patient-derived induced pluripotent stem cells (iPSCs) or genetically modified human stem cell lines. We will also explain how new 3D culture technologies were applied to accelerate Aβ and p-tau pathologies in human neural cell cultures, as compared the standard two-dimensional (2D) culture conditions. Finally, we will discuss a potential impact of the human 3D human neural cell culture models on the AD drug-development process. These revolutionary 3D culture models of AD will contribute to accelerate the discovery of novel AD drugs.