Assessing the efficacy of endoscopic office olfactory biopsy sites to produce neural progenitor cell cultures for the study of neuropsychiatric disorders

Cultured Mesenchymal Cells from Nasal Turbinate as a Cellular Model of the Neurodevelopmental Component of Schizophrenia Etiology

The study of neurodevelopmental molecular mechanisms in schizophrenia requires the development of adequate biological models such as patient-derived cells and their derivatives. We previously utilized cell lines with neural progenitor properties (CNON) derived from the superior or middle turbinates of patients with schizophrenia and control groups to study schizophrenia-specific gene expression. In this study, we analyzed single-cell RNA seq data from two CNON cell lines (one derived from an individual with schizophrenia (SCZ) and the other from a control group) and two biopsy samples from the middle turbinate (MT) (also from an individual with SCZ and a control). We compared our data with previously published data regarding the olfactory neuroepithelium and demonstrated that CNON originated from a single cell type present both in middle turbinate and the olfactory neuroepithelium and expressed in multiple markers of mesenchymal cells. To define the relatedness of CNON to the developing human brain, we also compared CNON datasets with scRNA-seq data derived from an embryonic brain and found that the expression profile of the CNON closely matched the expression profile one of the cell types in the embryonic brain. Finally, we evaluated the differences between SCZ and control samples to assess the utility and potential benefits of using CNON single-cell RNA seq to study the etiology of schizophrenia.

Cultured Mesenchymal Cells from Nasal Turbinate as a Cellular Model of the Neurodevelopmental Component of Schizophrenia Etiology

Study of the neurodevelopmental molecular mechanisms of schizophrenia requires the development of adequate biological models such as patient-derived cells and their derivatives. We previously used cell lines with neural progenitor properties (CNON) derived from superior or middle turbinates of patients with schizophrenia and control groups to study gene expression specific to schizophrenia. In this study, we compared single cell-RNA seq data from two CNON cell lines, one derived from an individual with schizophrenia (SCZ) and the other from a control group, with two biopsy samples from the middle turbinate (MT), also from an individual with SCZ and a control. In addition, we compared our data with previously published data from olfactory neuroepithelium (1). Our data demonstrated that CNON originated from a single cell type which is present both in middle turbinate and olfactory neuroepithelium. CNON express multiple markers of mesenchymal cells. In order to define relatedness of CNON to the developing human brain, we also compared CNON datasets with scRNA-seq data of embryonic brain (2) and found that the expression profile of CNON very closely matched one of the cell types in the embryonic brain. Finally, we evaluated differences between SCZ and control samples to assess usability and potential benefits of using single cell RNA-seq of CNON to study etiology of schizophrenia.

Characterisation of Neurospheres-Derived Cells from Human Olfactory Epithelium

A major problem in psychiatric research is a deficit of relevant cell material of neuronal origin, especially in large quantities from living individuals. One of the promising options is cells from the olfactory neuroepithelium, which contains neuronal progenitors that ensure the regeneration of olfactory receptors. These cells are easy to obtain with nasal biopsies and it is possible to grow and cultivate them in vitro. In this work, we used RNAseq expression profiling and immunofluorescence microscopy to characterise neurospheres-derived cells (NDC), that simply and reliably grow from neurospheres (NS) obtained from nasal biopsies. We utilized differential expression analysis to explore the molecular changes that occur during transition from NS to NDC. We found that processes associated with neuronal and vascular cells are downregulated in NDC. A comparison with public transcriptomes revealed a depletion of neuronal and glial components in NDC. We also discovered that NDC have several metabolic features specific to neuronal progenitors treated with the fungicide maneb. Thus, while NDC retain some neuronal/glial identity, additional protocol alterations are needed to use NDC for mass sample collection in psychiatric research.

Gene Expression in Patient-Derived Neural Progenitors Implicates WNT5A Signaling in the Etiology of Schizophrenia

BACKGROUND

Genome-wide association studies of schizophrenia have demonstrated that variations in noncoding regions are responsible for most of the common variation heritability of the disease. It is hypothesized that these risk variants alter gene expression. Therefore, studying alterations in gene expression in schizophrenia may provide a direct approach to understanding the etiology of the disease. In this study we use cultured neural progenitor cells derived from olfactory neuroepithelium (CNON cells) as a genetically unaltered cellular model to elucidate the neurodevelopmental aspects of schizophrenia.

METHODS

We performed a gene expression study using RNA sequencing of CNON cells from 111 control subjects and 144 individuals with schizophrenia. Differentially expressed genes were identified with DESeq2 software, using covariates to correct for sex, age, library batches, and 1 surrogate variable component.

RESULTS

A total of 80 genes were differentially expressed (false discovery rate < 10%), showing enrichment in cell migration, cell adhesion, developmental process, synapse assembly, cell proliferation, and related Gene Ontology categories. Cadherin and Wnt signaling pathways were positive in overrepresentation test, and, in addition, many genes were specifically involved in WNT5A signaling. The differentially expressed genes were modestly, but significantly, enriched in the genes overlapping single nucleotide polymorphisms with genome-wide significant association from the Psychiatric Genomics Consortium genome-wide association study of schizophrenia. We also found substantial overlap with genes associated with other psychiatric disorders or brain development, enrichment in the same Gene Ontology categories as genes with mutations de novo in schizophrenia, and studies of induced pluripotent stem cell-derived neural progenitor cells.

CONCLUSIONS

CNON cells are a good model of the neurodevelopmental aspects of schizophrenia and can be used to elucidate the etiology of the disorder.

[Isolation of neurospheres and neural progenitor cells from the olfactory epithelium]

The olfactory epithelium (OE) is an accessible source of neural stem cells and progenitor cells. The objective of the study was to compare the effectiveness of various biopsy sites to isolate and propagate neural progenitor cells from the olfactory epithelium (OE). The authors assessed OE cell count in OE in different sites of the nasal cavity and showed the possibility of isolation neurospheres from nasal biopsies. In total, 45 inpatinets were included in the study. Biopsy specimens were obtained from 30 patients undergoing septoplasty and/or turbinate surgery. Three areas of OE were biopsied: lower third section of the nasal septum (A), anterior part of the middle turbinate (B), upper third of the nasal septum (C). Immunocytochemistry and fluorescence-activated cell sorting showed that OE cells were NCAM-positive. Mean percentage of NCAM+ cells was 7.8% for A, 42.7% for B and 18.2% for C. The difference was significant between A and B (p=0.0001) and B and C (p=0.01). Therefore, the anterior part of the middle turbinate was an easily accessible and safe site to obtain neural cells. To confirm this, neurospheres were obtained in 15 patients with schizophrenia who underwent in-office endoscopy.

Is Olfactory Epithelium Biopsy Useful for Confirming Alzheimer's Disease?

OBJECTIVES

The clinical symptoms of Alzheimer's disease (AD) are preceded by a long asymptomatic period associated with "silent" deposition of aberrant paired helical filament (PHF)-tau and amyloid-beta proteins in brain tissue. Similar depositions have been reported within the olfactory epithelium (OE), a tissue that can be biopsied in vivo. The degree to which such biopsies are useful in identifying AD is controversial. This postmortem study had 3 main goals: first, to quantify the relative densities of AD-related proteins in 3 regions of the olfactory neuroepithelium, namely, the nasal septum, middle turbinate, and superior turbinate; second, to establish whether such densities are correlated among these epithelial regions as well as with semi-quantitative ratings of general brain cortex pathology; and third, to evaluate correlations between the protein densities and measures of antemortem cognitive function.

METHODS

Postmortem blocks of olfactory mucosa were obtained from 12 AD cadavers and 24 controls and subjected to amyloid-beta and PHF-tau immunohistochemistry.

RESULTS

We observed marked heterogeneity in the presence of the biomarkers of tau and amyloid-beta among the targeted olfactory epithelial regions. No significant difference was observed between the cadavers with AD and the controls regarding the concentration of these proteins in any of these epithelial regions. Only one correlation significant was evident, namely, that between the tau protein densities of the middle and the upper turbinate (r = .58, P = .002).

CONCLUSION

AD-related biomarker heterogeneity, which has not been previously demonstrated, makes comparisons across studies difficult and throws into question the usefulness of OE amyloid-beta and PHF-tau biopsies in detecting AD.

Using 3D epigenomic maps of primary olfactory neuronal cells from living individuals to understand gene regulation

As part of PsychENCODE, we developed a three-dimensional (3D) epigenomic map of primary cultured neuronal cells derived from olfactory neuroepithelium (CNON). We mapped topologically associating domains and high-resolution chromatin interactions using Hi-C and identified regulatory elements using chromatin immunoprecipitation and nucleosome positioning assays. Using epigenomic datasets from biopsies of 63 living individuals, we found that epigenetic marks at distal regulatory elements are more variable than marks at proximal regulatory elements. By integrating genotype and metadata, we identified enhancers that have different levels corresponding to differences in genetic variation, gender, smoking, and schizophrenia. Motif searches revealed that many CNON enhancers are bound by neuronal-related transcription factors. Last, we combined 3D epigenomic maps and gene expression profiles to predict enhancer-target gene interactions on a genome-wide scale. This study not only provides a framework for understanding individual epigenetic variation using a primary cell model system but also contributes valuable data resources for epigenomic studies of neuronal epithelium.

[Olfactory neuroepithelium as a model for the studies of molecular mechanisms of schizophrenia]

Olfactory neuroepithelium (OE) is shown to be a suitable experimental model to study neuronal biomarkers of psychiatric diseases including schizophrenia. Olfactory neuronal precursors can be useful for studying neurodevelopmental stages, neuronal markers, pharmacological screening. However, a limited number of research groups have used this cell model in a small number of patients and healthy people that can be explained by several factors. Based on literature reports and own research, the authors analyze the advantages and limitations of OE-derived cell/tissue models. The main limitations of these models are decreased rate of harvesting and culturing OE-derived cell and low percentage of patients who agreed to participate in the study. Our results showed that only 10% of patients with schizophrenia signed informed consent for nasal biopsy, 80% of them underwent biopsy.

Analysis of Gene Expression Variance in Schizophrenia Using Structural Equation Modeling

Schizophrenia (SCZ) is a psychiatric disorder of unknown etiology. There is evidence suggesting that aberrations in neurodevelopment are a significant attribute of schizophrenia pathogenesis and progression. To identify biologically relevant molecular abnormalities affecting neurodevelopment in SCZ we used cultured neural progenitor cells derived from olfactory neuroepithelium (CNON cells). Here, we tested the hypothesis that variance in gene expression differs between individuals from SCZ and control groups. In CNON cells, variance in gene expression was significantly higher in SCZ samples in comparison with control samples. Variance in gene expression was enriched in five molecular pathways: serine biosynthesis, PI3K-Akt, MAPK, neurotrophin and focal adhesion. More than 14% of variance in disease status was explained within the logistic regression model (C-value = 0.70) by predictors accounting for gene expression in 69 genes from these five pathways. Structural equation modeling (SEM) was applied to explore how the structure of these five pathways was altered between SCZ patients and controls. Four out of five pathways showed differences in the estimated relationships among genes: between KRAS and NF1, and KRAS and SOS1 in the MAPK pathway; between PSPH and SHMT2 in serine biosynthesis; between AKT3 and TSC2 in the PI3K-Akt signaling pathway; and between CRK and RAPGEF1 in the focal adhesion pathway. Our analysis provides evidence that variance in gene expression is an important characteristic of SCZ, and SEM is a promising method for uncovering altered relationships between specific genes thus suggesting affected gene regulation associated with the disease. We identified altered gene-gene interactions in pathways enriched for genes with increased variance in expression in SCZ. These pathways and loci were previously implicated in SCZ, providing further support for the hypothesis that gene expression variance plays important role in the etiology of SCZ.

The Olfactory Neural Epithelium As a Tool in Neuroscience

Capturing both dynamic changes (state) and persistent signatures (trait) directly associated with disease at the molecular level is crucial in modern medicine. The olfactory neural epithelium, easily accessible in clinical settings, is a promising surrogate model in translational brain medicine, complementing the limitations in current engineered cell models.

Office-based olfactory mucosa biopsies

BACKGROUND

Requests from researchers for olfactory mucosal biopsies are increasing as a result of advances in the fields of neuroscience and stem cell biology. Published studies report variable rates of success in obtaining true olfactory tissue, often below 50%. In cases where biopsies are not obtained carefully and confirmed through histological techniques, erroneous conclusions are made. Attention to the epithelium alone without submucosal analysis may add to the confusion. A consistent biopsy technique can help rhinologists obtain higher yields of olfactory mucosa. Confirmatory tissue staining analysis assures olfactory mucosa has been obtained, thereby strengthening clinical correlations and scientific conclusions.

METHODS

Biopsies of the septum within the anterior olfactory cleft were obtained under endoscopic guidance in an office procedure room using topical local anesthetic (lidocaine). After mucosal incision, a small, cupped, biopsy forceps was used to obtain specimens approximately 2 to 3 mm in size. Specimens were sectioned and analyzed with immunohistochemistry for presence of olfactory epithelium and/or olfactory fascicles.

RESULTS

A total of 14 subjects were biopsied in this analysis. Four subjects had biopsies in the operating room (OR). The remaining 10 underwent biopsies in the clinic. All biopsies obtained in the OR revealed evidence of olfactory mucosa. Of the 10 clinic biopsies, 8 (80%) revealed evidence of olfactory mucosa. No complications were encountered.

CONCLUSION

High yields of olfactory mucosa can be obtained safely in an office-based setting. Technique, including attention to the area of biopsy, and confirmatory analysis are important in assuring presence of olfactory tissue.