A comprehensive understanding of the changes in gene expression in cell types involved in idiopathic pulmonary fibrosis (IPF) will shed light on the mechanisms underlying the loss of alveolar epithelial cells and development of honeycomb cysts and fibroblastic foci. We sought to understand changes in IPF lung cell transcriptomes and gain insight into innate immune aspects of pathogenesis. We investigated IPF pathogenesis using single-cell RNA-sequencing of fresh lung explants, comparing human IPF fibrotic lower lobes reflecting late disease, upper lobes reflecting early disease and normal lungs. IPF lower lobes showed increased fibroblasts, and basal, ciliated, goblet and club cells, but decreased alveolar epithelial cells, and marked alterations in inflammatory cells. We found three discrete macrophage subpopulations in normal and fibrotic lungs, one expressing monocyte markers, one highly expressing FABP4 and INHBA (FABP4 hi ), and one highly expressing SPP1 and MERTK (SPP1 hi ). SPP1 hi macrophages in fibrotic lower lobes showed highly upregulated SPP1 and MERTK expression. Low-level local proliferation of SPP1 hi macrophages in normal lungs was strikingly increased in IPF lungs. Co-localisation and causal modelling supported the role for these highly proliferative SPP1 hi macrophages in activation of IPF myofibroblasts in lung fibrosis. These data suggest that SPP1 hi macrophages contribute importantly to lung fibrosis in IPF, and that therapeutic strategies targeting MERTK and macrophage proliferation may show promise for treatment of this disease.
Systemic sclerosis (SSc) is a multifactorial autoimmune fibrotic disorder involving complex rewiring of cell-intrinsic and cell-extrinsic signaling coexpression networks involving a range of cell types. However, the rewired circuits as well as corresponding cell-cell interactions remain poorly understood. To address this, we used a predictive machine learning framework to analyze single-cell RNA-sequencing data from 24 SSc patients across the severity spectrum as quantified by the modified Rodnan skin score (MRSS).
Although T cells have been implicated in the pathogenesis of systemic sclerosis (SSc), a comprehensive study of T-cell-mediated immune responses in the affected skin of patients with progressive SSc is lacking. Droplet-based single-cell transcriptome analysis of SSc skin biopsies opens avenues for dissecting patient-specific T-cell heterogeneity, providing a basis for identifying novel gene expression related to functional pathways associated with severity of SSc skin disease.Single-cell RNA sequencing was performed by droplet-based sequencing (10x Genomics), focusing on 3729 CD3+ lymphocytes (867 cells from normal and 2862 cells from SSc skin samples) from skin biopsies of 27 patients with active SSc and 10 healthy donors. Confocal immunofluorescence microscopy of progressive SSc skin samples validated transcriptional results and visualised spatial localisations of T-cell subsets.We identified several subsets of recirculating and tissue-resident T cells in healthy and SSc skin that were associated with distinct signalling pathways. While most clusters shared a common gene expression signature between patients and controls, we identified a unique cluster of recirculating CXCL13+ T cells in SSc skin which expressed a T helper follicular-like gene expression signature and that appears to be poised to promote B-cell responses within the inflamed skin of patients.Current available therapies to reverse or even slow progression of SSc lead to broad killing of immune cells and consequent toxicities, including death. Identifying the precise immune mechanism(s) driving SSc pathogenesis could lead to innovative therapies that selectively target the aberrant immune response, resulting in better efficacy and less toxicity.
<div>AbstractPurpose:<p>The heterogeneity of tumor cells presents a major challenge to cancer diagnosis and therapy. Cutaneous T-cell lymphomas (CTCL) are a group of T lymphocyte malignancies that primarily affect skin. Lack of highly specific markers for malignant lymphocytes prevents early diagnosis, while only limited treatment options are available for patients with advanced stage CTCL. Droplet-based single-cell transcriptome analysis of CTCL skin biopsies opens avenues for dissecting patient-specific T lymphocyte heterogeneity, providing a basis for identifying specific markers for diagnosis and cure of CTCL.</p>Experimental Design:<p>Single-cell RNA-sequencing was performed by Droplet-based sequencing (10X Genomics), focusing on 14,056 CD3<sup>+</sup> lymphocytes (448 cells from normal and 13,608 cells from CTCL skin samples) from skin biopsies of 5 patients with advanced-stage CTCL and 4 healthy donors. Protein expression of identified genes was validated in advanced stage CTCL skin tumors by immunohistochemistry and confocal immunofluorescence microscopy.</p>Results:<p>Our analysis revealed a large inter- and intratumor gene expression heterogeneity in the T lymphocyte subset, as well as a common gene expression signature in highly proliferating lymphocytes that was validated in multiple advanced-stage skin tumors. In addition, we established the immunologic state of reactive lymphocytes and found heterogeneity in effector and exhaustion programs across patient samples.</p>Conclusions:<p>Single-cell analysis of CTCL skin tumor samples reveals patient-specific landscapes of malignant and reactive lymphocytes within the local microenvironment of each tumor, giving an unprecedented view of lymphocyte heterogeneity and identifying tumor-specific molecular signatures, with important implications for diagnosis and personalized disease treatment.</p></div>
Rationale: Idiopathic Pulmonary Fibrosis (IPF) is a lethal disease with a mechanism of onset and progression that is not fully understood. Past genomic studies, focused on fibrotic lungs, provided valuable insights of its pathophysiology, but an important unanswered question remains: what are the cellular and molecular changes in the histologically normal looking parts of IPF lungs? The answer may help understand the early disease stages and unveil biological pathways that precede and likely lead to the histological changes in IPF. Methods: We reanalyzed our published single cell expression data from healthy controls and IPF patients (Morse et al, 2019, ERJ) . We used Seurat to identify cell types and perform all analyses. Results: We identified 20 cell types and further focused on 4 fibroblast sub-clusters. Two of the sub-clusters were significantly enriched for cells originating from the IPF lungs. Analysis of differentially expressed genes in each cluster identified unique expression profiles for IPF/control states. Interestingly, IPF upper non-fibrotic and lower fibrotic lobes didn't show significant differences in these profiles. This result shows that fibroblast types such as myofibroblasts which have been associated with the IPF state, are present in parts of the lung that are histologically non-fibrotic. We also found an enrichment in multiple copper-binding proteins supporting the role of metal copper in IPF pathogenesis. Conclusion: We showed histologically normal tissue in IPF lungs is a profibrotic environment representing an earlier stage where many disease-associated cellular alterations have not yet occurred. This establishes a more appropriate environment to study early interventions.
<div>AbstractPurpose:<p>The heterogeneity of tumor cells presents a major challenge to cancer diagnosis and therapy. Cutaneous T-cell lymphomas (CTCL) are a group of T lymphocyte malignancies that primarily affect skin. Lack of highly specific markers for malignant lymphocytes prevents early diagnosis, while only limited treatment options are available for patients with advanced stage CTCL. Droplet-based single-cell transcriptome analysis of CTCL skin biopsies opens avenues for dissecting patient-specific T lymphocyte heterogeneity, providing a basis for identifying specific markers for diagnosis and cure of CTCL.</p>Experimental Design:<p>Single-cell RNA-sequencing was performed by Droplet-based sequencing (10X Genomics), focusing on 14,056 CD3<sup>+</sup> lymphocytes (448 cells from normal and 13,608 cells from CTCL skin samples) from skin biopsies of 5 patients with advanced-stage CTCL and 4 healthy donors. Protein expression of identified genes was validated in advanced stage CTCL skin tumors by immunohistochemistry and confocal immunofluorescence microscopy.</p>Results:<p>Our analysis revealed a large inter- and intratumor gene expression heterogeneity in the T lymphocyte subset, as well as a common gene expression signature in highly proliferating lymphocytes that was validated in multiple advanced-stage skin tumors. In addition, we established the immunologic state of reactive lymphocytes and found heterogeneity in effector and exhaustion programs across patient samples.</p>Conclusions:<p>Single-cell analysis of CTCL skin tumor samples reveals patient-specific landscapes of malignant and reactive lymphocytes within the local microenvironment of each tumor, giving an unprecedented view of lymphocyte heterogeneity and identifying tumor-specific molecular signatures, with important implications for diagnosis and personalized disease treatment.</p></div>
Localized scleroderma (LS) is an autoimmune disease with both inflammatory and fibrotic components causing an abnormal deposition of collagen in the skin and underlying tissue, often leading to disfigurement and disability. Much of its pathophysiology is extrapolated from systemic sclerosis (SSc) since the histopathology findings in the skin are nearly identical. However, LS is critically understudied. Single-cell RNA sequencing (scRNA seq) technology provides a novel way to obtain detailed information at the individual cellular level, overcoming this barrier. Here, we analyzed the affected skin of 14 patients with LS (pediatric and adult) and 14 healthy controls. Fibroblast populations were the focus, since they are the main drivers of fibrosis in SSc. We identified 12 fibroblast subclusters in LS, which overall had an inflammatory gene expression (IFN and HLA-associated genes). A myofibroblast-like cluster (SFRP4/PRSS23) was more prevalent in LS subjects and shared many upregulated genes expressed in SSc-associated myofibroblasts, though it also had strong expression of CXCL9/10/11, known CXCR3 ligands. A CXCL2/IRF1 cluster identified was unique to LS, with a robust inflammatory gene signature, including IL-6, and according to cell communication analysis are influenced by macrophages. In summary, potential disease-propagating fibroblasts and associated gene signatures were identified in LS skin via scRNA seq.
