Modeling schizophrenia using induced pluripotent stem cell-derived and fibroblast-induced neurons

Impaired migration of autologous induced neural stem cells from patients with schizophrenia and implications for genetic risk for psychosis

Stem cell technologies have presented explicit evidence of the neurodevelopmental hypothesis of schizophrenia. However, few studies investigated relevance of the schizophrenia genetic liability and the use of genetic reprogramming on pluripotent stem cells to the impaired neurodevelopment shown by stem cells. Therefore, this study sought to investigate the cellular phenotypes of induced neural stem cells (iNSCs) derived without genetic modification from patients with schizophrenia and from genetic high risk (GHR) individuals. Three patients with a diagnosis of schizophrenia, 3 GHR individuals who had two or more relatives with schizophrenia, and 3 healthy volunteers participated. iNSCs were derived using a small molecule-based lineage switch method, and their gene expression levels and migration capabilities were examined. Demographic characteristics were not different among the groups (age, χ² = 5.637, P = .060; education, χ² = 2.111, P = .348). All participants stayed well during the follow-up except one GHR individual who developed psychosis 1.5 years later. Migration capacity was impaired in iNSCs from patients with schizophrenia (SZ-iNSCs) compared to iNSCs from GHR individuals or controls (P < .001). iNSCs from a GHR individual who later developed schizophrenia showed migratory impairment that was similar to SZ-iNSCs. Gene expression levels of Sox2 in SZ-iNSCs were significantly lower than those in controls (P = .028). Defective migration in genetically unmodified SZ-iNSCs is the first direct demonstration of neurodevelopmental abnormalities in schizophrenia. Additionally, alterations in gene expression in SZ-iNSCs suggest mechanisms by which genetic liability leads to aberrant neurodevelopment.

A human iPSC-astroglia neurodevelopmental model reveals divergent transcriptomic patterns in schizophrenia

While neurodevelopmental abnormalities have been associated with schizophrenia (SCZ), the role of astroglia in disease pathophysiology remains poorly understood. In the present study, we used a human induced pluripotent stem cell (iPSC)-derived astrocyte model to investigate the temporal patterns of astroglia differentiation during developmental stages critical for SCZ using RNA sequencing. The model generated astrocyte-specific gene expression patterns during differentiation that corresponded well to astroglia-specific expression signatures of in vivo cortical fetal development. Using this model we identified SCZ-specific expression dynamics, and found that SCZ-associated differentially expressed genes were significantly enriched in the medial prefrontal cortex, striatum, and temporal lobe, targeting VWA5A and ADAMTS19. In addition, SCZ astrocytes displayed alterations in calcium signaling, and significantly decreased glutamate uptake and metalloproteinase activity relative to controls. These results implicate novel transcriptional dynamics in astrocyte differentiation in SCZ together with functional changes that are potentially important biological components of SCZ pathology.

Cellular Models in Schizophrenia Research

Schizophrenia (SZ) is a prevalent functional psychosis characterized by clinical behavioural symptoms and underlying abnormalities in brain function. Genome-wide association studies (GWAS) of schizophrenia have revealed many loci that do not directly identify processes disturbed in the disease. For this reason, the development of cellular models containing SZ-associated variations has become a focus in the post-GWAS research era. The application of revolutionary clustered regularly interspaced palindromic repeats CRISPR/Cas9 gene-editing tools, along with recently developed technologies for cultivating brain organoids in vitro, have opened new perspectives for the construction of these models. In general, cellular models are intended to unravel particular biological phenomena. They can provide the missing link between schizophrenia-related phenotypic features (such as transcriptional dysregulation, oxidative stress and synaptic dysregulation) and data from pathomorphological, electrophysiological and behavioural studies. The objectives of this review are the systematization and classification of cellular models of schizophrenia, based on their complexity and validity for understanding schizophrenia-related phenotypes.

Enhanced efficiency of nonviral direct neuronal reprogramming on topographical patterns

Nonviral direct neuronal reprogramming holds significant potential in the fields of tissue engineering and regenerative medicine. However, the issue of low reprogramming efficiency poses a major barrier to its application. We propose that topographical cues, which have been applied successfully to enhance lineage-directed differentiation and multipotent stem cell transdifferentiation, could improve nonviral direct neuronal reprogramming efficiency. To investigate, we used a polymer-BAM (Brn2, Ascl1, Myt1l) factor transfection polypex to reprogram primary mouse embryonic fibroblasts. Using a multiarchitecture chip, we screened for patterns that may improve transfection and/or subsequent induced neuron reprogramming efficiency. Selected patterns were then investigated further by analyzing β-tubulin III (TUJ1) and microtubule-associated protein 2 (MAP2) protein expression, cell morphology and electrophysiological function of induced neurons. Certain hierarchical topographies, with nanopatterns imprinted on micropatterns, significantly improved the percentage of TUJ1+ and MAP2+ cells. It is postulated that the microscale base pattern enhances initial BAM expression while the nanoscale sub-pattern promotes subsequent maturation. This is because the base pattern alone increased expression of TUJ1 and MAP2, while the nanoscale pattern was the only pattern yielding induced neurons capable of firing multiple action potentials. Nanoscale patterns also produced the highest fraction of cells showing spontaneous synaptic activity. Overall, reprogramming efficiency with one dose of polyplex on hierarchical patterns was comparable to that of five doses without topography. Thus, topography can enhance nonviral direct reprogramming of fibroblasts into induced neurons.

Transcriptome analysis reveals disparate expression of inflammation-related miRNAs and their gene targets in iPSC-astrocytes from people with schizophrenia

Despite the high heritability of schizophrenia (SCZ), details of its pathophysiology and etiology are still unknown. Recent findings suggest that aberrant inflammatory regulation and microRNAs (miRNAs) are involved. Here we performed a comparative analysis of the global miRNome of human induced pluripotent stem cell (iPSC)-astrocytes, derived from SCZ patients and healthy controls (CTRLs), at baseline and following inflammatory modulation using IL-1β. We identified four differentially expressed miRNAs (miR-337-3p, miR-127-5p, miR-206, miR-1185-1-3p) in SCZ astrocytes that exhibited significantly lower baseline expression relative to CTRLs. Group-specific differential expression (DE) analyses exploring possible distinctions in the modulatory capacity of IL-1β on miRNA expression in SCZ versus CTRL astroglia revealed trends toward altered miRNA expressions. In addition, we analyzed peripheral blood samples from a large cohort of SCZ patients (n = 484) and CTRLs (n = 496) screening for the expression of specific gene targets of the four DE miRNAs that were identified in our baseline astrocyte setup. Three of these genes, LAMTOR4, IL23R, and ERBB3, had a significantly lower expression in the blood of SCZ patients compared to CTRLs after multiple testing correction. We also found nominally significant differences for ERBB2 and IRAK1, which similarly displayed lower expressions in SCZ versus CTRL. Furthermore, we found matching patterns between the expressions of identified miRNAs and their target genes when comparing our in vitro and in vivo results. The current results further our understanding of the pathobiological basis of SCZ.

Decreased IL-1β-induced CCL20 response in human iPSC-astrocytes in schizophrenia: Potential attenuating effects on recruitment of regulatory T cells

Schizophrenia (SCZ) is a severe mental disorder with a high heritability. Although its pathophysiology is mainly unknown, dysregulated immune activation and inflammation have recently emerged as possible candidates in the underlying mechanisms of SCZ. Previous studies suggest that aberrant inflammasome activation, glia dysregulation, and brain inflammation may be involved in the pathophysiology of the disorder. Here, we studied the effects of inflammatory modulation on human induced pluripotent stem cell (iPSC)-derived astrocytes generated from SCZ patients and healthy controls (CTRL). Inflammasome activation was mimicked by short-term IL-1β exposure, and gene expression were measured with high-coverage RNA-Seq to ensure a global characterization of the transcriptional effects of the treatment. IL-1β exposure modulated several pathways involved in innate immune responses, cell cycle regulation, and metabolism in both SCZ and CTRL astrocytes. Significant differences were found in the expression of HILPDA and CCL20 genes, both of which had reduced up-regulation upon IL-1β treatment in SCZ astrocytes compared to CTRL astrocytes. CCL20 data were further validated and confirmed using qPCR, ELISA, and regulatory T lymphocyte (T_reg) migration assays. Additionally, we found significantly decreased mRNA expression of the T_reg-specific marker FOXP3 in the blood of a large cohort of SCZ patients (n = 484) compared to CTRL (n = 472). Since CCL20 is a specific chemoattractant for CD4⁺CD25⁺CCR6⁺ T_regs, which are crucially involved in anti-inflammatory responses during brain (auto)inflammation, our results imply a plausible role for an altered astroglia-CCL20-CCR6-T_reg axis in SCZ pathophysiology.

Functional Consequences of CHRNA7 Copy-Number Alterations in Induced Pluripotent Stem Cells and Neural Progenitor Cells

Copy-number variants (CNVs) of chromosome 15q13.3 manifest clinically as neuropsychiatric disorders with variable expressivity. CHRNA7, encoding for the α7 nicotinic acetylcholine receptor (nAChR), has been suggested as a candidate gene for the phenotypes observed. Here, we used induced pluripotent stem cells (iPSCs) and neural progenitor cells (NPCs) derived from individuals with heterozygous 15q13.3 deletions and heterozygous 15q13.3 duplications to investigate the CHRNA7-dependent molecular consequences of the respective CNVs. Unexpectedly, both deletions and duplications lead to decreased α7 nAChR-associated calcium flux. For deletions, this decrease in α7 nAChR-dependent calcium flux is expected due to haploinsufficiency of CHRNA7. For duplications, we found that increased expression of CHRNA7 mRNA is associated with higher expression of nAChR-specific and resident ER chaperones, indicating increased ER stress. This is likely a consequence of inefficient chaperoning and accumulation of α7 subunits in the ER, as opposed to being incorporated into functional α7 nAChRs at the cell membrane. Here, we showed that α7 nAChR-dependent calcium signal cascades are downregulated in both 15q13.3 deletion and duplication NPCs. While it may seem surprising that genomic changes in opposite direction have consequences on downstream pathways that are in similar direction, it aligns with clinical data, which suggest that both individuals with deletions and duplications of 15q13.3 manifest neuropsychiatric disease and cognitive deficits.

Induced Pluripotent Stem Cells: Global Research Trends

The induced pluripotent stem cell (iPSC) was first described more than 10 years ago and is currently used in various basic science and clinical research fields. The aim of this report is to examine the trends in research using iPSCs over the last 10 years. The 2006-2016 PubMed database was searched using the MeSH term "induced pluripotent stem cells." Only original research articles were selected, with a total of 3323 articles. These were classified according to research theme into reprogramming, differentiation protocols for specific cells and/or tissues, pathophysiological research on diseases, and discovery of new drugs, and then the trends over the years were analyzed. We also focused on 232 research publications on the pathophysiological causes of diseases and drug discovery with impact factor (IF; Thomson Reuters) of six or more. The IF of each article was summed up by year, by main target disease, and by country, and the total IF score was expressed as trends of research. The trends of research activities of reprogramming and differentiation on specific cells and/or tissues reached maxima in 2013/2014. On the other hand, research on pathophysiology and drug discovery increased continuously. The 232 articles with IF ≥6 dealt with neurological, immunological/hematological, cardiovascular, and digestive tract diseases, in that order. The majority of articles were published from the United States, followed by Japan, Germany, and United Kingdom. In conclusion, iPSCs have become a general tool for pathophysiological research on disease and drug discovery.

Are reprogrammed cells a useful tool for studying dopamine dysfunction in psychotic disorders? A review of the current evidence

Since 2006, reprogrammed cells have increasingly been used as a biomedical research technique in addition to neuro-psychiatric methods. These rapidly evolving techniques allow for the generation of neuronal sub-populations, and have sparked interest not only in monogenetic neuro-psychiatric diseases, but also in poly-genetic and poly-aetiological disorders such as schizophrenia (SCZ) and bipolar disorder (BPD). This review provides a summary of 19 publications on reprogrammed adult somatic cells derived from patients with SCZ, and five publications using this technique in patients with BPD. As both disorders are complex and heterogeneous, there is a plurality of hypotheses to be tested in vitro. In SCZ, data on alterations of dopaminergic transmission in vitro are sparse, despite the great explanatory power of the so-called DA hypothesis of SCZ. Some findings correspond to perturbations of cell energy metabolism, and observations in reprogrammed cells suggest neuro-developmental alterations. Some studies also report on the efficacy of medicinal compounds to revert alterations observed in cellular models. However, due to the paucity of replication studies, no comprehensive conclusions can be drawn from studies using reprogrammed cells at the present time. In the future, findings from cell culture methods need to be integrated with clinical, epidemiological, pharmacological and imaging data in order to generate a more comprehensive picture of SCZ and BPD.

Generation and transplantation of reprogrammed human neurons in the brain using 3D microtopographic scaffolds

Cell replacement therapy with human pluripotent stem cell-derived neurons has the potential to ameliorate neurodegenerative dysfunction and central nervous system injuries, but reprogrammed neurons are dissociated and spatially disorganized during transplantation, rendering poor cell survival, functionality and engraftment in vivo. Here, we present the design of three-dimensional (3D) microtopographic scaffolds, using tunable electrospun microfibrous polymeric substrates that promote in situ stem cell neuronal reprogramming, neural network establishment and support neuronal engraftment into the brain. Scaffold-supported, reprogrammed neuronal networks were successfully grafted into organotypic hippocampal brain slices, showing an ∼3.5-fold improvement in neurite outgrowth and increased action potential firing relative to injected isolated cells. Transplantation of scaffold-supported neuronal networks into mouse brain striatum improved survival ∼38-fold at the injection site relative to injected isolated cells, and allowed delivery of multiple neuronal subtypes. Thus, 3D microscale biomaterials represent a promising platform for the transplantation of therapeutic human neurons with broad neuro-regenerative relevance.

Human pluripotent stem cell derived neurons have the potential for cell replacement therapy for brain injury and disease but problems on transplantation need to be overcome. Here, the authors use a microtopographic scaffold to graft neurons into both hippocampal organoids and the mouse brain striatum.

Induced Pluripotent Stem Cells as a Novel Tool in Psychiatric Research

Reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) provides a valuable opportunity to study neurodevelopmental and neurodegenerative psychiatric diseases by offering an unlimited source for patient-specific neuronal and glial cells. The present review focuses on the recent advancements in modeling psychiatric disorders such as Phelan-McDermid syndrome, Timothy syndrome, Rett syndrome, schizophrenia, bipolar disorder, and dementia. The treatment effects identified in studies on iPSCs using known therapeutic compounds are also summarized in this review. Here we discuss validation of cellular models and explore iPSCs as a novel drug screening tool. Although there are several limitations associated with the current methods used to study mental disorders, using iPSCs as a model system provides the advantage of rewinding and reviewing the development and degeneration of human neural cells.

Characterization of Genetic Networks Associated with Alzheimer's Disease

At the molecular level, the genetics of complex disease such as Alzheimer's disease (AD) manifests itself as series of alterations in the molecular interactions in pathways and networks that define biological processes underlying the pathophysiological states of disease. While large-scale genome-wide association (GWA) studies of late-onset alzheimer's disease (LOAD) have uncovered prominent genomic regions linked to the disease, the cause for the vast majority of LOAD cases still remains unknown. Increasingly available large-scale genomic and genetic data related to LOAD has made it possible to comprehensively uncover the mechanisms causally lined to LOAD in a completely data-driven manner. Here we review the various aspects of systems/network biology approaches and methodology in constructing genetic networks associated with AD from large sampling of postmortem brain tissues. We describe in detail a multiscale network modeling approach (MNMA) that integrates interaction and causal gene networks to analyze large-scale DNA, gene expression and pathophysiological data from multiple post-mortem brain regions of LOAD patients as well non-demented normal controls. MNMA first employs weighted gene co-expression network analysis (WGCNA) to construct multi-tissue networks that simultaneously capture intra-tissue and inter-tissue gene-gene interactions and then quantifies the change in connectivity among highly co-expressed genes in LOAD with respect to the normal state. Co-expressed gene modules are then rank ordered by relevance to pathophysiological traits and enrichment of genes differentially expressed in LOAD. Causal regulatory relationships among the genes in each module are then determined by a Bayesian network inference framework that is used to formally integrate genetic and gene expression information. MNMA has uncovered a massive remodeling of network structures in LOAD and identified novel subnetworks and key regulators that are causally linked to LOAD. In the end, we will outline the challenges in systems/network approaches to LOAD.

A Dishful of a Troubled Mind: Induced Pluripotent Stem Cells in Psychiatric Research

Neuronal differentiation of induced pluripotent stem cells and direct reprogramming represent powerful methods for modeling the development of neurons in vitro. Moreover, this approach is also a means for comparing various cellular phenotypes between cell lines originating from healthy and diseased individuals or isogenic cell lines engineered to differ at only one or a few genomic loci. Despite methodological constraints and initial skepticism regarding this approach, the field is expanding at a fast pace. The improvements include the development of new differentiation protocols resulting in selected neuronal populations (e.g., dopaminergic, GABAergic, hippocampal, and cortical), the widespread use of genome editing methods, and single-cell techniques. A major challenge awaiting in vitro disease modeling is the integration of clinical data in the models, by selection of well characterized clinical populations. Ideally, these models will also demonstrate how different diagnostic categories share overlapping molecular disease mechanisms, but also have unique characteristics. In this review we evaluate studies with regard to the described developments, to demonstrate how differentiation of induced pluripotent stem cells and direct reprogramming can contribute to psychiatry.

Engineered in vitro disease models

The ultimate goal of most biomedical research is to gain greater insight into mechanisms of human disease or to develop new and improved therapies or diagnostics. Although great advances have been made in terms of developing disease models in animals, such as transgenic mice, many of these models fail to faithfully recapitulate the human condition. In addition, it is difficult to identify critical cellular and molecular contributors to disease or to vary them independently in whole-animal models. This challenge has attracted the interest of engineers, who have begun to collaborate with biologists to leverage recent advances in tissue engineering and microfabrication to develop novel in vitro models of disease. As these models are synthetic systems, specific molecular factors and individual cell types, including parenchymal cells, vascular cells, and immune cells, can be varied independently while simultaneously measuring system-level responses in real time. In this article, we provide some examples of these efforts, including engineered models of diseases of the heart, lung, intestine, liver, kidney, cartilage, skin and vascular, endocrine, musculoskeletal, and nervous systems, as well as models of infectious diseases and cancer. We also describe how engineered in vitro models can be combined with human inducible pluripotent stem cells to enable new insights into a broad variety of disease mechanisms, as well as provide a test bed for screening new therapies.

Transcriptomics of maternal and fetal membranes can discriminate between gestational-age matched preterm neonates with and without cognitive impairment diagnosed at 18-24 months

BACKGROUND

Neurocognitive impairment among children born preterm may arise from complex interactions between genes and the intra-uterine environment.

OBJECTIVES

(1) To characterize the transcriptomic profiles of chorioamniotic membranes in preterm neonates with and without neurocognitive impairment via microarrays and (2) to determine if neonates with neurocognitive impairment can be identified at birth.

MATERIALS/METHODS

A retrospective case-control study was conducted to examine the chorioamniotic transcriptome of gestational-age matched very preterm neonates with and without neurocognitive impairment at 18-24 months' corrected-age defined by a Bayley-III Cognitive Composite Score <80 (n = 14 each). Pathway analysis with down-weighting of overlapping genes (PADOG) was performed to identify KEGG pathways relevant to the phenotype. Select differentially expressed genes were profiled using qRT-PCR and a multi-gene disease prediction model was developed using linear discriminant analysis. The model's predictive performance was tested on a new set of cases and controls (n = 19 each).

RESULTS

1) 117 genes were differentially expressed among neonates with and without subsequent neurocognitive impairment (p<0.05 and fold change >1.5); 2) Gene ontology analysis indicated enrichment of 19 biological processes and 3 molecular functions; 3)PADOG identified 4 significantly perturbed KEGG pathways: oxidative phosphorylation, Parkinson's disease, Alzheimer's disease and Huntington's disease (q-value <0.1); 4) 48 of 90 selected differentially expressed genes were confirmed by qRT-PCR, including genes implicated in energy metabolism, neuronal signaling, vascular permeability and response to injury (e.g., up-regulation of SEPP1, APOE, DAB2, CD163, CXCL12, VWF; down-regulation of HAND1, OSR1)(p<0.05); and 5) a multi-gene model predicted 18-24 month neurocognitive impairment (using the ratios of OSR1/VWF and HAND1/VWF at birth) in a larger, independent set (sensitivity = 74%, at specificity = 83%).

CONCLUSIONS

Gene expression patterns in the chorioamniotic membranes link neurocognitive impairment in preterm infants to neurodegenerative disease pathways and might be used to predict neurocognitive impairment. Further prospective studies are needed.

RNA Sequencing in Schizophrenia

Schizophrenia (SCZ) is a serious psychiatric disorder that affects 1% of general population and places a heavy burden worldwide. The underlying genetic mechanism of SCZ remains unknown, but studies indicate that the disease is associated with a global gene expression disturbance across many genes. Next-generation sequencing, particularly of RNA sequencing (RNA-Seq), provides a powerful genome-scale technology to investigate the pathological processes of SCZ. RNA-Seq has been used to analyze the gene expressions and identify the novel splice isoforms and rare transcripts associated with SCZ. This paper provides an overview on the genetics of SCZ, the advantages of RNA-Seq for transcriptome analysis, the accomplishments of RNA-Seq in SCZ cohorts, and the applications of induced pluripotent stem cells and RNA-Seq in SCZ research.

Unlocking the treasure trove: from genes to schizophrenia biology

Significant progress is being made in defining the genetic etiology of schizophrenia. As the list of implicated genes grows, parallel developments in gene editing technology provide new methods to investigate gene function in model systems. The confluence of these two research fields--gene discovery and functional biology--may offer novel insights into schizophrenia etiology. We review recent advances in these fields, consider the likely obstacles to progress, and consider strategies as to how these can be overcome.

Stem cells on the brain: modeling neurodevelopmental and neurodegenerative diseases using human induced pluripotent stem cells

Seven years have passed since the initial report of the generation of induced pluripotent stem cells (iPSCs) from adult human somatic cells, and in the intervening time the field of neuroscience has developed numerous disease models using this technology. Here, we review progress in the field and describe both the advantages and potential pitfalls of modeling neurodegenerative and neurodevelopmental diseases using this technology. We include tables with information on neural differentiation protocols and studies that developed human iPSC lines to model neurological diseases. We also discuss how one can: investigate effects of genetic mutations with iPSCs, examine cell fate-specific phenotypes, best determine the specificity of a phenotype, and bring in vivo relevance to this in vitro technique.

Biomarkers for combat-related PTSD: focus on molecular networks from high-dimensional data

Posttraumatic stress disorder (PTSD) and other deployment-related outcomes originate from a complex interplay between constellations of changes in DNA, environmental traumatic exposures, and other biological risk factors. These factors affect not only individual genes or bio-molecules but also the entire biological networks that in turn increase or decrease the risk of illness or affect illness severity. This review focuses on recent developments in the field of systems biology which use multidimensional data to discover biological networks affected by combat exposure and post-deployment disease states. By integrating large-scale, high-dimensional molecular, physiological, clinical, and behavioral data, the molecular networks that directly respond to perturbations that can lead to PTSD can be identified and causally associated with PTSD, providing a path to identify key drivers. Reprogrammed neural progenitor cells from fibroblasts from PTSD patients could be established as an in vitro assay for high throughput screening of approved drugs to determine which drugs reverse the abnormal expression of the pathogenic biomarkers or neuronal properties.

Will brain cells derived from induced pluripotent stem cells or directly converted from somatic cells (iNs) be useful for schizophrenia research?

The reprogramming of nonneuronal somatic cells to induced pluripotent stem cells and their derivation to functional brain cells as well as the related methods for direct conversion of somatic cells to neurons have opened up the possibility of conducting research on cellular disease models from living schizophrenia patients. We review the published literature on schizophrenia that has used this rapidly developing technology, highlighting the need for specific aims and reproducibility. The key issues for consideration for future schizophrenia research in this field are discussed and potential investigations using this technology are put forward for critical assessment by the reader.