Induced Pluripotent Stem Cells Derived from Alzheimer's Disease Patients: The Promise, the Hope and the Path Ahead

CRISPR/Cas9 Mediated Therapeutic Approach in Huntington's Disease

The pathogenic mechanisms of these diseases must be well understood for the treatment of neurological disorders such as Huntington's disease. Huntington's Disease (HD), a dominant and neurodegenerative disease, is characterized by the CAG re-expansion that occurs in the gene encoding the polyglutamine-expanded mutant Huntingtin (mHTT) protein. Genome editing approaches include zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) and Clustered Regularly Interspaced Short Palindromic Repeats/Caspase 9 (CRISPR/Cas9) systems. CRISPR/Cas9 technology allows effective gene editing in different cell types and organisms. Through these systems are created isogenic control of human origin induced pluripotent stem cells (iPSCs). In human and mouse models, HD-iPSC lines can be continuously corrected using these systems. HD-iPSCs can be corrected through the CRISPR/Cas9 system and the cut-and-paste mechanism using isogenic control iPSCs. This mechanism is a piggyBac transposon-based selection system that can effectively switch between vectors and chromosomes. In studies conducted, it has been determined that in neural cells derived from HD-iPSC, there are isogenic controls as corrected lines recovered from phenotypic abnormalities and gene expression changes. It has been determined that trinucleotide repeat disorders occurring in HD can be cured by single-guide RNA (sgRNA) and normal exogenous DNA restoration, known as the single guideline RNA specific to Cas9. The purpose of this review in addition to give general information about HD, a neurodegenerative disorder is to explained the role of CRISPR/Cas9 system with iPSCs in HD treatment.

Protective Effect of Human-Neural-Crest-Derived Nasal Turbinate Stem Cells against Amyloid-β Neurotoxicity through Inhibition of Osteopontin in a Human Cerebral Organoid Model of Alzheimer’s Disease

The aim of this study was to validate the use of human brain organoids (hBOs) to investigate the therapeutic potential and mechanism of human-neural-crest-derived nasal turbinate stem cells (hNTSCs) in models of Alzheimer’s disease (AD). We generated hBOs from human induced pluripotent stem cells, investigated their characteristics according to neuronal markers and electrophysiological features, and then evaluated the protective effect of hNTSCs against amyloid-β peptide (Aβ1–42) neurotoxic activity in vitro in hBOs and in vivo in a mouse model of AD. Treatment of hBOs with Aβ1–42 induced neuronal cell death concomitant with decreased expression of neuronal markers, which was suppressed by hNTSCs cocultured under Aβ1–42 exposure. Cytokine array showed a significantly decreased level of osteopontin (OPN) in hBOs with hNTSC coculture compared with hBOs only in the presence of Aβ1–42. Silencing OPN via siRNA suppressed Aβ-induced neuronal cell death in cell culture. Notably, compared with PBS, hNTSC transplantation significantly enhanced performance on the Morris water maze, with reduced levels of OPN after transplantation in a mouse model of AD. These findings reveal that hBO models are useful to evaluate the therapeutic effect and mechanism of stem cells for application in treating AD.

Disease modeling and stem cell immunoengineering in regenerative medicine using CRISPR/Cas9 systems

CRISPR/Cas systems are popular genome editing tools that belong to a class of programmable nucleases and have enabled tremendous progress in the field of regenerative medicine. We here outline the structural and molecular frameworks of the well-characterized type II CRISPR system and several computational tools intended to facilitate experimental designs. The use of CRISPR tools to generate disease models has advanced research into the molecular aspects of disease conditions, including unraveling the molecular basis of immune rejection. Advances in regenerative medicine have been hindered by major histocompatibility complex-human leukocyte antigen (HLA) genes, which pose a major barrier to cell- or tissue-based transplantation. Based on progress in CRISPR, including in recent clinical trials, we hypothesize that the generation of universal donor immune-engineered stem cells is now a realistic approach to tackling a multitude of disease conditions.

Science Runs and the Debate Brakes: Somatic Gene-Editing as a New Tool for Gender-Specific Medicine in Alzheimer's Disease

Gender-specific medicine is a discipline that studies the influence of sex and gender on physiology, pathophysiology, and diseases. One example in light of how a genetic-based disease among other diseases, that impact on sex, can be represented by the risk of developing dementia or Alzheimer's disease. The question that comes into focus is whether gene-editing can represent a new line of investigation to be explored in the development of personalized, gender-specific medicine that guarantees gender equity in health policies. This article aims to discuss the relevance of adopting a gender-specific focus on gene-editing research, considered as a way of contributing to the advance of medicine's understanding, treatment, and prevention of dementia, particularly Alzheimer's disease. The development or improvement of cures could take advantage of the knowledge of the gender diversity in order to ascertain and develop differential interventions also at the genetic level between women and men, and this deserves special attention and deep ethical reflection.

Modeling and Targeting Alzheimer's Disease With Organoids

Human neurodegenerative diseases, such as Alzheimer’s disease (AD), are not easily modeled in vitro due to the inaccessibility of brain tissue and the level of complexity required by existing cell culture systems. Three-dimensional (3D) brain organoid systems generated from human pluripotent stem cells (hPSCs) have demonstrated considerable potential in recapitulating key features of AD pathophysiology, such as amyloid plaque- and neurofibrillary tangle-like structures. A number of AD brain organoid models have also been used as platforms to assess the efficacy of pharmacological agents in disease progression. However, despite the fact that stem cell-derived brain organoids mimic early aspects of brain development, they fail to model complex cell-cell interactions pertaining to different regions of the human brain and aspects of natural processes such as cell differentiation and aging. Here, we review current advances and limitations accompanying several hPSC-derived organoid methodologies, as well as recent attempts to utilize them as therapeutic platforms. We additionally discuss comparative benefits and disadvantages of the various hPSC-derived organoid generation protocols and differentiation strategies. Lastly, we provide a comparison of hPSC-derived organoids to primary tissue-derived organoids, examining the future potential and advantages of both systems in modeling neurodegenerative disorders, especially AD.

Human Induced Pluripotent Stem Cells : Clinical Significance and Applications in Neurologic Diseases

The generation of human induced pluripotent stem cells (iPSCs) from somatic cells using gene transfer opens new areas for precision medicine with personalized cell therapy and encourages the discovery of essential platforms for targeted drug development. iPSCs retain the genome of the donor, may regenerate indefinitely, and undergo differentiation into virtually any cell type of interest using a range of published protocols. There has been enormous interest among researchers regarding the application of iPSC technology to regenerative medicine and human disease modeling, in particular, modeling of neurologic diseases using patient-specific iPSCs. For instance, Parkinson’s disease, Alzheimer’s disease, and spinal cord injuries may be treated with iPSC therapy or replacement tissues obtained from iPSCs. In this review, we discuss the work so far on generation and characterization of iPSCs and focus on recent advances in the use of human iPSCs in clinical setting.

Programmable Molecular Scissors: Applications of a New Tool for Genome Editing in Biotech

Targeted genome editing is an advanced technique that enables precise modification of the nucleic acid sequences in a genome. Genome editing is typically performed using tools, such as molecular scissors, to cut a defined location in a specific gene. Genome editing has impacted various fields of biotechnology, such as agriculture; biopharmaceutical production; studies on the structure, regulation, and function of the genome; and the creation of transgenic organisms and cell lines. Although genome editing is used frequently, it has several limitations. Here, we provide an overview of well-studied genome-editing nucleases, including single-stranded oligodeoxynucleotides (ssODNs), transcription activator-like effector nucleases (TALENs), zinc-finger nucleases (ZFNs), and CRISPR-Cas9 RNA-guided nucleases (CRISPR-Cas9). To this end, we describe the progress toward editable nuclease-based therapies and discuss the minimization of off-target mutagenesis. Future prospects of this challenging scientific field are also discussed.

Small-molecule induction of Aβ-42 peptide production in human cerebral organoids to model Alzheimer's disease associated phenotypes

Human mini-brains (MB) are cerebral organoids that recapitulate in part the complexity of the human brain in a unique three-dimensional in vitro model, yielding discrete brain regions reminiscent of the cerebral cortex. Specific proteins linked to neurodegenerative disorders are physiologically expressed in MBs, such as APP-derived amyloids (Aβ), whose physiological and pathological roles and interactions with other proteins are not well established in humans. Here, we demonstrate that neuroectodermal organoids can be used to study the Aβ accumulation implicated in Alzheimer’s disease (AD). To enhance the process of protein secretion and accumulation, we adopted a chemical strategy of induction to modulate post-translational pathways of APP using an Amyloid-β Forty-Two Inducer named Aftin-5. Secreted, soluble Aβ fragment concentrations were analyzed in MB-conditioned media. An increase in the Aβ₄₂ fragment secretion was observed as was an increased Aβ₄₂/Aβ₄₀ ratio after drug treatment, which is consistent with the pathological-like phenotypes described in vivo in transgenic animal models and in vitro in induced pluripotent stem cell-derived neural cultures obtained from AD patients. Notably in this context we observe time-dependent Aβ accumulation, which differs from protein accumulation occurring after treatment. We show that mini-brains obtained from a non-AD control cell line are responsive to chemical compound induction, producing a shift of physiological Aβ concentrations, suggesting that this model can be used to identify environmental agents that may initiate the cascade of events ultimately leading to sporadic AD. Increases in both Aβ oligomers and their target, the cellular prion protein (PrP^C), support the possibility of using MBs to further understand the pathophysiological role that underlies their interaction in a human model. Finally, the potential application of MBs for modeling age-associated phenotypes and the study of neurological disorders is confirmed.

A high-throughput model for investigating neuronal function and synaptic transmission in cultured neuronal networks

Loss of synapses or alteration of synaptic activity is associated with cognitive impairment observed in a number of psychiatric and neurological disorders, such as schizophrenia and Alzheimer’s disease. Therefore successful development of in vitro methods that can investigate synaptic function in a high-throughput format could be highly impactful for neuroscience drug discovery. We present here the development, characterisation and validation of a novel high-throughput in vitro model for assessing neuronal function and synaptic transmission in primary rodent neurons. The novelty of our approach resides in the combination of the electrical field stimulation (EFS) with data acquisition in spatially separated areas of an interconnected neuronal network. We integrated our methodology with state of the art drug discovery instrumentation (FLIPR Tetra) and used selective tool compounds to perform a systematic pharmacological validation of the model. We investigated pharmacological modulators targeting pre- and post-synaptic receptors (AMPA, NMDA, GABA-A, mGluR2/3 receptors and Nav, Cav voltage-gated ion channels) and demonstrated the ability of our model to discriminate and measure synaptic transmission in cultured neuronal networks. Application of the model described here as an unbiased phenotypic screening approach will help with our long term goals of discovering novel therapeutic strategies for treating neurological disorders.

Modern Genome Editing Technologies in Huntington's Disease Research

The development of new revolutionary technologies for directed gene editing has made it possible to thoroughly model and study NgAgo human diseases at the cellular and molecular levels. Gene editing tools like ZFN, TALEN, CRISPR-based systems, NgAgo and SGN can introduce different modifications. In gene sequences and regulate gene expression in different types of cells including induced pluripotent stem cells (iPSCs). These tools can be successfully used for Huntington's disease (HD) modeling, for example, to generate isogenic cell lines bearing different numbers of CAG repeats or to correct the mutation causing the disease. This review presents common genome editing technologies and summarizes the progress made in using them in HD and other hereditary diseases. Furthermore, we will discuss prospects and limitations of genome editing in understanding HD pathology.

Paving the Way Toward Complex Blood-Brain Barrier Models Using Pluripotent Stem Cells

A tissue with great need to be modeled in vitro is the blood-brain barrier (BBB). The BBB is a tight barrier that covers all blood vessels in the brain and separates the brain microenvironment from the blood system. It consists of three cell types [neurovascular unit (NVU)] that contribute to the unique tightness and selective permeability of the BBB and has been shown to be disrupted in many diseases and brain disorders, such as vascular dementia, stroke, multiple sclerosis, and Alzheimer's disease. Given the progress that pluripotent stem cells (PSCs) have made in the past two decades, it is now possible to produce many cell types from the BBB and even partially recapitulate this complex tissue in vitro. In this review, we summarize the most recent developments in PSC differentiation and modeling of the BBB. We also suggest how patient-specific human-induced PSCs could be used to model BBB dysfunction in the future. Lastly, we provide perspectives on how to improve production of the BBB in vitro, for example by improving pericyte differentiation protocols and by better modeling the NVU in the dish.

CRISPR-mediated genome editing and human diseases

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) technology has emerged as a powerful technology for genome editing and is now widely used in basic biomedical research to explore gene function. More recently, this technology has been increasingly applied to the study or treatment of human diseases, including Barth syndrome effects on the heart, Duchenne muscular dystrophy, hemophilia, β-Thalassemia, and cystic fibrosis. CRISPR/Cas9 (CRISPR-associated protein 9) genome editing has been used to correct disease-causing DNA mutations ranging from a single base pair to large deletions in model systems ranging from cells in vitro to animals in vivo. In addition to genetic diseases, CRISPR/Cas9 gene editing has also been applied in immunology-focused applications such as the targeting of C-C chemokine receptor type 5, the programmed death 1 gene, or the creation of chimeric antigen receptors in T cells for purposes such as the treatment of the acquired immune deficiency syndrome (AIDS) or promoting anti-tumor immunotherapy. Furthermore, this technology has been applied to the genetic manipulation of domesticated animals with the goal of producing biologic medical materials, including molecules, cells or organs, on a large scale. Finally, CRISPR/Cas9 has been teamed with induced pluripotent stem (iPS) cells to perform multiple tissue engineering tasks including the creation of disease models or the preparation of donor-specific tissues for transplantation. This review will explore the ways in which the use of CRISPR/Cas9 is opening new doors to the treatment of human diseases.