Browsing by Subject "iPSC"

Schizophrenia is a debilitating psychiatric disorder associated with reduced life expectancy. The biological mechanism of schizophrenia is nebulous; however, many findings point to the central nervous system and neurons, where a reduction in dendritic spines has been indicated by previous research. The genetic findings support the involvement of synapses in the pathogenesis of schizophrenia. To study the biological properties stemming from genetics, relevant model systems and efficient methods are needed. Induced pluripotent stem cell (iPSC) technology offers a robust method for modeling the biological processes underlying schizophrenia. Somatic cells, e.g. fibroblasts, can be reprogrammed back to a pluripotent state resembling embryonic stem cells, and further differentiated into any cell type of the body, which might not be otherwise accessible. This allows establishing and characterizing neuronal cultures from patient and control cell lines, potentially revealing biological differences associated to the disease phenotype. The field of schizophrenia research has adopted iPSC technology and multiple studies have been conducted. These include assessments of synaptic density in the produced neuronal cultures, many of which reported decreased density associated with schizophrenia. In this thesis, a modified version of Nehme et al. (2018) protocol was used to differentiate iPSCs into neurons in co-cultures with human iPSC-derived astrocytes. The overarching aim was to construct an immunocytochemistry (ICC) -based assay to measure synaptic density in the produced co-cultures. First, suitable markers for characterization by ICC were tested and selected. The markers were selected to inform about neuronal identity, maturity, and synapses of the differentiated neurons. Next, the culturing conditions were optimized regarding the cell density and coating of the culturing wells. Finally, to estimate the utility of the assay, a pilot study was performed with three cell lines derived from a healthy control and a monozygotic twin pair discordant for schizophrenia. iPSCs from these cell lines were differentiated into neurons in co-cultures with astrocytes, and then characterized with ICC using selected markers and image analysis software. The synaptic density was quantified for each cell line. The performance of the assay was evaluated with analysis of variance (ANOVA) and restricted maximum likelihood model (RELM). An assay to quantify synaptic structures in mature neurons was established. The average synaptic density for all cell lines was approximately 1 synapse per 100μm of neurite. Analysis of the data produced with the assay revealed a notable batch effect and technical variation. This suggests that further optimization is needed to reduce variance from undesired sources. The pilot data suggests that the differences in synaptic density between cases and controls may be modest, further highlighting the need for minimizing noise in the assay to improve signal to noise ratio. However, indicated by power analysis, large sample sizes are needed to identify meaningful differences between cases and controls. In light of these results, more attention should be drawn to the methodology in the field of iPSC-based studies, as the principals of the assay constructed here were similar to other synaptic assays used in previous publications.

Schizophrenia, a mental disorder affecting over 1% of the world’s population, has a 41-65% chance of being acquired in monozygotic twins, and shows a complex heritable pattern. Research has shown the involvement of various neuronal and glial cell types in the disorder’s progression. Recent studies are focusing on cortical interneurons, as clinical features of schizophrenia such as working memory deficits emerge due to the abnormal activity of these cells . The advent of induced pluripotent stem cell (iPSC) technology has made it easier to study schizophrenia disease mechanisms, with studies revealing differences in morphological and physiological properties of cortical interneurons in patients with schizophrenia. In this thesis , the aim was to optimize iPSC-interneuron differentiation protocol and live-cell imaging method suitable for disease modelling. Interneurons were differentiated from iPSCs with overexpression of inducible transcription factor, Achaete-scute homolog 1 (ASCL1). The iPSCs were derived from twin pairs discordant for schizophrenia and from healthy controls. Expression of interneuron-specific markers was verified using RT-qPCR and validated at the protein level by an immunocytochemistry (ICC) assay in the control cell lines first. Additionally, to estimate the formation of neurites and differences in neurite length and branching, the differentiated interneurons from the controls were subjected to live-cell imaging by IncuCyte S3 live-cell imaging system. Imaging parameters such as cell body cluster filter was optimized to visualize the neurites. To study interneuron involvement in schizophrenia, iPSCs from one twin pair discordant for schizophrenia were successfully differentiated. Interneurons strongly expressed Gamma-aminobutyric acid (GABA) neurotransmitter related neuronal markers: glutamate decarboxylase 67 (GAD67) and GABA at protein level. The neurons were identified as somatostatin (SST) subtype GABAergic neurons by their mRNA and protein expression. While it was possible to observe differences in gene expression, there were no clear differences in the morphology of the differentiated cells as well as the localization of markers in comparison to the healthy controls. Further studies should focus on having a protracted time for differentiation where more mature interneurons can be produced by establishing co-cultures with excitatory neurons. This will help replicate the in vivo cortical machinery which in turn will aid in better understanding of disease mechanisms.