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Characterization of the immunologic impact of sarcoidosis in peripheral blood mononuclear cells via single-cell RNA-seq

ABSTRACT: Sarcoidosis is a systemic inflammatory disease characterized by infiltration of immune cells into granulomas. Previous gene expression studies using heterogeneous cell mixtures lack insight into cell-type-specific immune dysregulation. We performed the first single-cell RNA-sequencing study of sarcoidosis in peripheral immune cells in 48 patients and controls. Following unbiased clustering, differentially expressed genes were identified for 18 cell types and bioinformatically assessed for function and pathway enrichment. Our results reveal persistent activation of circulating classical monocytes with subsequent upregulation of trafficking molecules. Specifically, classical monocytes upregulated distinct markers of activation including adhesion molecules, pattern recognition receptors, and chemokine receptors, as well as enrichment of immunoregulatory pathways HMGB1, mTOR, and ephrin receptor signaling. Predictive modeling implicated TGFβ and mTOR signaling as drivers of persistent monocyte activation. Additionally, sarcoidosis T cell subsets displayed patterns of dysregulation. CD4 naïve T cells were enriched for markers of apoptosis and Th17/Treg differentiation, while effector T cells showed enrichment of anergy-related pathways. Differentially expressed genes in regulatory T cells suggested dysfunctional p53, cell death, and TNFR2 signaling. Using more sensitive technology and more precise units of measure, we identify cell-type specific, novel inflammatory and regulatory pathways. Based on our findings, we suggest a novel model involving four convergent arms of dysregulation: persistent hyperactivation of innate and adaptive immunity via classical monocytes and CD4 naïve T cells, regulatory T cell dysfunction, and effector T cell anergy. We further our understanding of the immunopathology of sarcoidosis and point to novel therapeutic targets.

ORGANISM(S): Homo sapiens

PROVIDER: GSE132338 | GEO | 2020/12/01

REPOSITORIES: GEO

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Project description:Introduction: In sarcoidosis, peripheral lymphopenia and anergy have been associated with increased inflammation and maladaptive immune activity, likely promoting development of chronic and progressive disease. However, the molecular mechanisms that lead to reduced lymphocyte proportions, particularly CD4+ T-cells, have not been fully elucidated. We posit that paradoxical peripheral lymphopenia is characterized by a dysregulated transcriptomic network associated with cell function and fate that results from altered transcription factor targeting activity. Methods: Messenger RNA-sequencing (mRNA-seq) was performed on peripheral blood mononuclear cells (PBMCs) from ACCESS study subjects with sarcoidosis and matched controls and findings validated on a sarcoidosis case-control cohort and a sarcoidosis case series. Preserved PBMC transcriptomic networks between case-control cohorts were assessed to establish cellular associations with gene modules and define regulatory targeting involved in sarcoidosis immune dysregulation utilizing weighted gene co-expression network analysis and differential transcription factor involvement analysis. Network centrality measures identified master transcriptional regulators of subnetworks related to cell proliferation and death. Predictive models of differential PBMC proportions constructed from ACCESS target gene expression corroborated the relationship between aberrant transcription factor regulatory activity and imputed and clinical PBMC populations in the validation cohorts. Results: We identified two unique and preserved gene modules significantly associated with sarcoidosis immune dysregulation. Strikingly, increased expression of a monocyte-driven, and not a lymphocyte-driven, gene module related to innate immunity and cell death was the best predictor of peripheral CD4+ T-cell proportions. Within the gene network of this monocyte-driven module, TLE3 and CBX8 were determined to be master regulators of the cell death subnetwork. A core gene signature of differentially over-expressed target genes of TLE3 and CBX8 involved in cellular communication and immune response regulation accurately predicted imputed and clinical monocyte expansion and CD4+ T-cell depletion. Conclusions: Altered transcriptional regulation associated with aberrant gene expression of a monocyte-driven transcriptional network likely influences lymphocyte function and survival. Although further investigation is warranted, this indicates that crosstalk between hyperactive monocytes and lymphocytes may instigate peripheral lymphopenia and underlie sarcoidosis immune dysregulation and pathogenesis. Future therapies selectively targeting master regulators, or their targets, may mitigate dysregulated immune processes in sarcoidosis and disease progression.

Project description:Cardiac involvement is an important determinant of mortality amongst sarcoidosis patients. While granulomatous inflammation is a hallmark finding in cardiac sarcoidosis, the precise immune cell populations that comprise the granuloma remain unresolved. Furthermore, it is unclear how the cellular and transcriptomic landscape of cardiac sarcoidosis differs from other inflammatory heart diseases. We leveraged spatial transcriptomics (GeoMx DSP) and single nucleus RNA sequencing (snRNAseq) to elucidate the cellular and transcriptional landscape of cardiac sarcoidosis. Using GeoMX DSP technology, we compared the transcriptomal profile of CD68+ rich immune cell infiltrates in human cardiac sarcoidosis, giant cell myocarditis, and lymphocytic myocarditis. We performed snRNAseq of human cardiac sarcoidosis to identify immune cell types and examined their transcriptomic landscape and regulation. Using multi-channel immunofluorescence staining, we validated immune cell populations identified by snRNAseq, determined their spatial relationship, and devised an immunostaining approach to distinguish cardiac sarcoidosis from other inflammatory heart diseases. Despite overlapping histological features, spatial transcriptomics identified transcriptional signatures and associated pathways that robustly differentiated cardiac sarcoidosis from giant cell myocarditis and lymphocytic myocarditis. snRNAseq revealed the presence of diverse populations of myeloid cells in cardiac sarcoidosis with distinct molecular features. We identified GPNMB as a novel marker of multinucleated giant cells and predicted that the MITF family of transcription factors regulated this cell type. We also detected additional macrophage populations in cardiac sarcoidosis including HLA-DR+ macrophages, SYTL3+ macrophages and CD163+ resident macrophages. HLA-DR+ macrophages were found immediately adjacent to GPMMB+ giant cells, a distinct feature compared with other inflammatory cardiac diseases. SYTL3+ macrophages were located scattered throughout the granuloma and CD163+ macrophages, CD1c+ dendritic cells, non-classical monocytes, and T-cells were located at the periphery and outside of the granuloma. Finally, we demonstrate mTOR pathway activation is associated with proliferation and is selectively found in HLA-DR+ and SYLT3+ macrophages. In this study, we identified diverse populations of immune cells with distinct molecular signatures that comprise the sarcoid granuloma. These findings provide new insights into the pathology of cardiac sarcoidosis and highlight opportunities to improve diagnostic testing.

Project description:Introduction: Sarcoidosis is a multisystem immuno-inflammatory disorder of unknown etiology that most commonly involves the lungs. We hypothesized that an unbiased approach to identify pathways activated in alveolar macrophagesâa key immuno-inflammatory cell in the lungâcan shed light on the pathogenesis of this complex disease. Methods: We recruited 15 patients with various stages of sarcoidosis and 12 healthy controls. All subjects underwent bronchoscopy with lavage. For each subject, total RNA was extracted from bronchoalveolar (BAL) cells and hybridized to an Affymetrix GeneChip Human Genome U133A 2.0 microarray. Rigorous statistical methods were applied to identify differential gene expression between subjects with sarcoidosis vs. controls. To better elucidate pathways differentially activated between these groups, we applied gene set enrichment analysis (GSEA) to the transcriptional profiles of BAL cells. We used false discovery rate (FDR) < 0.01 to designate significant enrichment. Results: Sarcoid patients were either non-smokers or ex-smokers, all had lung involvement and only 2 were on systemic prednisone. Healthy controls were all non-smokers. Comparison of BAL cell gene expression between sarcoidosis and healthy subjects revealed over 1200 differentially expressed genes at an FDR cutoff < 0.01. Several previously described immune mediators, such as interferon gamma, were up-regulated in the sarcoidosis subjects. Since genes often exert their influence through functionally coherent modules, we performed GSEA based on global expression profiles of alveolar macrophages between the subject groups. We identified more than 200 gene sets enriched in patients with sarcoidosis whereas very few pathways were over-represented in the healthy controls. Many of the sarcoidosis-associated pathways mapped to inflammatory and immune-related processes including T-cell signaling, graft vs. host disease, IL-12, IL-23, and IL-17 pathways, and oxidative phosphorylation. However, we also found and confirmed significant alteration in Proteasome-related pathways. Conclusions: BAL cells in sarcoidosis are characterized by enrichment of distinct transcriptional networks involved in immuno-inflammatory and proteasomal processes. Our findings add to the growing evidence implicating airspace resident cells in the pathogenesis of sarcoidoisis and identify specific pathways whose activation may modulate disease progression. Total RNA from BAL cells of 15 subjects with sarcoidosis and 12 healthy controls was hybridized to 27 Affymetrix Genechip Human U133A 2.0 microarrays

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Characterization of the immunologic impact of sarcoidosis in peripheral blood mononuclear cells via single-cell RNA-seq

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