Abnormal B lymphocyte activation and function in systemic sclerosis

Exploring the molecular mechanism of Epimedium for the treatment of ankylosing spondylitis based on network pharmacology, molecular docking, and molecular dynamics simulations

Ankylosing spondylitis (AS) is a rheumatic disease that causes inflammation and bone formation in the spine. Despite significant advances in treatment, adverse side effects have triggered research into natural compounds. Epimedium (EP) is a traditional Chinese herb with a variety of pharmacological activities, including antirheumatic, anti-inflammatory, and immunomodulatory activities; however, its direct effects on AS treatment and the underlying molecular mechanisms have not been systematically studied. Thus, here, we used network pharmacology, molecular docking, and molecular dynamics simulations to explore the targets of EP for treating AS. We constructed an interaction network to elucidate the complex relationship between EP and AS. Sixteen active ingredients in EP were screened; 80 potential targets were identified. In particular, 8-(3-methylbut-2-enyl)-2-phenylchromone, anhydroicaritin, and luteolin were the core components and TNF, IL-6, IL-1β, MMP9, and PTGS2 were the core targets. The GO and KEGG analyses indicated that EP may modulate multiple biological processes and pathways, including the AGE-RAGE, TNF, NF-κB/MAPK, and TLR signaling pathways, for AS treatment. Molecular docking and molecular dynamics simulations showed good affinity between the active components and core targets of EP, with stable binding within 100 nanoseconds. In particular, 8-(3-methylbut-2-enyl)-2-phenylchromone possessed the highest free energy of binding to PTGS2 and TNF (-115.575 and - 87.676 kcal/mol, respectively). Thus, EP may affect AS through multiple pathways, including the alleviation of inflammation, oxidative stress, and immune responses. In summary, we identified the active components and potential targets of EP, highlighting new strategies for the further experimental validation and exploration of lead compounds for treating AS.

Single cell analysis in systemic sclerosis - A systematic review

In recent years, rapid advances in research methods have made single cell analysis possible. Systemic sclerosis (SSc), a disease characterized by the triad of immune abnormalities, fibrosis, and vasculopathy, has also been the subject of various analyses. To summarize the results of single cell analysis in SSc accumulated to date and to deepen our understanding of SSc. Four databases were used to perform a database search on 23rd June 2023. Assessed Grading of Recommendations Assessment, Development and Evaluation certainty of evidence were performed according to PRISMA guidelines. The analysis was completed on July 2023. 17 studies with 358 SSc patients were included. Three studies used PBMCs, six used skin, nine used lung with SSc-interstitial lung diseases (ILDs), and one used lung with SSc-pulmonary arterial hypertension (PAH). The cells studied included immune cells such as T cells, natural killer cells, monocytes, macrophages, and dendritic cells, as well as endothelial cells, fibroblasts, keratinocytes, alveolar type I cells, basal epithelial cells, smooth muscle cells, mesothelial cells, etc. This systematic review revealed the results of single cell analysis, suggesting that PBMCs, skin, SSc-ILD, and SSc-PAH show activation and dysfunction of cells associated with immune-abnormalities, fibrosis, and vasculopathy, respectively.

The role of B cells in systemic sclerosis

Systemic sclerosis (SSc) is a rare and refractory systemic disease characterized by fibrosis and vasculopathy in the presence of autoimmune abnormalities. While the exact cause of SSc is incompletely understood, the specific autoantibodies identified in SSc are closely linked to disease severity and prognosis, indicating a significant role of autoimmune abnormalities in the pathogenesis of SSc. Although the direct pathogenic mechanisms of autoantibodies in SSc are not fully elucidated, numerous prior investigations have demonstrated the involvement of B cells in the pathogenesis of SSc through various mechanisms. Additionally, several clinical trials have explored the efficacy of B-cell depletion therapy for SSc, with many reporting positive outcomes. However, the role of B cells in SSc pathogenesis is multifaceted, as they can both promote inflammation and exert inhibitory functions. This article provides an overview of the involvement of B cells in SSc development, incorporating the latest research findings.

Involvement of B cells in the development of systemic sclerosis

Systemic sclerosis (SSc) is a rare intractable systemic disease that causes fibrosis and vasculopathy against a background of autoimmune abnormalities. Although the etiology is not yet fully understood, the type of autoantibodies detected in SSc is closely associated with disease severity and prognosis, supporting that those autoimmune abnormalities play an important role in the pathogenesis of SSc. Although the direct pathogenicity of autoantibodies found in SSc is unknown, many previous studies have shown that B cells are involved in the development of SSc through a variety of functions. Furthermore, a number of clinical studies have been conducted in which B-cell depletion therapy has been tried for SSc, and many of these studies have found B-cell depletion therapy to be effective for SSc. However, the involvement of B cells in pathogenesis is complex, as they not only promote inflammation but also play an inhibitory role. This article outlines the role of B cells in the development of SSc, including the latest research.

Single-cell-level protein analysis revealing the roles of autoantigen-reactive B lymphocytes in autoimmune disease and the murine model

Despite antigen affinity of B cells varying from cell to cell, functional analyses of antigen-reactive B cells on individual B cells are missing due to technical difficulties. Especially in the field of autoimmune diseases, promising pathogenic B cells have not been adequately studied to date because of its rarity. In this study, functions of autoantigen-reactive B cells in autoimmune disease were analyzed at the single-cell level. Since topoisomerase I is a distinct autoantigen, we targeted systemic sclerosis as autoimmune disease. Decreased and increased affinities for topoisomerase I of topoisomerase I-reactive B cells led to anti-inflammatory and pro-inflammatory cytokine production associated with the inhibition and development of fibrosis, which is the major symptom of systemic sclerosis. Furthermore, inhibition of pro-inflammatory cytokine production and increased affinity of topoisomerase I-reactive B cells suppressed fibrosis. These results indicate that autoantigen-reactive B cells contribute to the disease manifestations in autoimmune disease through their antigen affinity.

B cell depletion inhibits fibrosis via suppressing pro-fibrotic macrophage differentiation in a mouse model of systemic sclerosis

OBJECTIVE

We investigated the effect of B cell depletion on fibrosis in systemic sclerosis (SSc) and its mechanism of action.

METHODS

Bleomycin-induced SSc (BLM-SSc) model mice were treated with anti-CD20 antibody, and skin and lung fibrosis was evaluated histopathologically. T cells and macrophages were co-cultured with B cells, and the effect of B cells on their differentiation was assessed by flow cytometry. We also co-cultured B cells and monocytes from SSc patients and analyzed the correlation between fibrosis and pro-fibrotic macrophage induction by B cells.

RESULTS

B cell depletion inhibited fibrosis in BLM-SSc mice. B cells from BLM-SSc mice increased pro-inflammatory cytokine producing T cells in co-culture. In BLM-SSc mice, B cell depletion before BLM treatment (pre-depletion) inhibited fibrosis more strongly than B cell depletion after BLM treatment (post-depletion). However, the frequencies of pro-inflammatory T cells were lower in the post-depletion group than in the pre-depletion group. This discrepancy suggests that the effect of B cell depletion on fibrosis cannot be explained by its effect on T cell differentiation. On the other hand, pro-fibrotic macrophages were markedly decreased in the pre-depletion group than in the post-depletion group. Furthermore, B cells from BLM-SSc mice increased pro-fibrotic macrophage differentiation in co-culture. In SSc patients, the extent of pro-fibrotic macrophage induction by B cells correlated with the severity of fibrosis.

CONCLUSION

These findings suggest that B cell depletion inhibits tissue fibrosis via suppressing pro-fibrotic macrophage differentiation in BLM-SSc mice, providing a new rationale for B cell depletion therapy in SSc.

Analysis of PI3K Pathway Associated Molecules Reveals Dysregulated Innate and Adaptive Functions of B Cells in Early Diffuse Cutaneous Systemic Sclerosis

B cell activation is an early event in the development of systemic sclerosis (SSc). The classical activation of B cells downstream of the B-cell receptor (BCR) involves the phosphatidylinositol-3 kinase (PI3K) pathway that integrates the effects of multiple co-stimulatory receptors. Our analysis of PI3K pathway associated molecules in peripheral blood B cells of early diffuse cutaneous SSc (dcSSc) patients showed altered mRNA expression of Toll-like receptor (TLR) homolog CD180, TLR4, complement component 3, IL-4 receptor and secreted phosphoprotein 1 (SPP1). Parallel to this, we found elevated basal SPP1 secretion in dcSSc B cells, but, with BCR + IL-4 receptor co-stimulation, we could not induce further secretion. CD180 stimulation alone resulted in NF-κB activation in more B cells than CD180 + BCR co-stimulation both in dcSSc and healthy control (HC), but the co-engagement increased the phosphorylation of NF-κB only in dcSSc B cells. Additionally, in contrast with HC B cells, the lower basal production of IL-10 by dcSSc B cells could not be elevated with CD180 stimulation. Furthermore, activation via CD180 increased the percentage of CD86+ switched memory (CD27+IgD−) B cells in dcSSc compared to HC. Our results suggest that alternative B cell activation and CD180 dysfunction cause imbalance of regulatory mechanisms in dcSSc B cells.

Systemic Sclerosis Perturbs the Architecture of the Immunome

Systemic sclerosis (SSc) is an autoimmune disease characterized by excessive fibrosis of skin and internal organs, and vascular dysfunction. Association of T and B cell subsets has been reported in SSc; however, there is lack of systematic studies of functional relations between immune cell subsets in this disease. This lack of mechanistic knowledge hampers targeted intervention. In the current study we sought to determine differential immune cell composition and their interactions in peripheral blood of SSc patients. Mononuclear cells from blood of SSc patients (n = 20) and healthy controls (n = 10) were analyzed by mass cytometry using a 36-marker (cell surface and intracellular) panel. Transcriptome analysis (m-RNA sequencing) was performed on sorted T and B cell subsets. Unsupervised clustering analysis revealed significant differences in the frequencies of T and B cell subsets in patients. Correlation network analysis highlighted an overall dysregulated immune architecture coupled with domination of inflammatory senescent T cell modules in SSc patients. Transcriptome analysis of sorted immune cells revealed an activated phenotype of CD4 and mucosal associated invariant T (MAIT) cells in patients, accompanied by increased expression of inhibitory molecules, reminiscent of phenotype exhibited by functionally adapted, exhausted T cells in response to chronic stimulation. Overall, this study provides an in-depth analysis of the systemic immunome in SSc, highlighting the potential pathogenic role of inflammation and chronic stimulation-mediated “functional adaptation” of immune cells.

Interleukin (IL)-17F and IL-17E are related to fibrosis and vasculopathy in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease that causes fibrosis and vasculopathy of the skin and internal organs against a background of autoimmune abnormalities. In recent years, the importance of the interleukin (IL)-17 family for inflammatory diseases has received much attention, but autoimmune diseases have not yet been fully explored. As for SSc, there is also no unified perspective on the involvement of the IL-17 family in its development, and few studies have been conducted linking IL-17F and IL-17E particularly to the disease severity. In the present study, we examined the correlation between serum IL-17F and IL-17E levels and disease severity in SSc patients. Moreover, the expression of the receptors for these cytokines, IL-17RB and IL-17RC, in skin tissues obtained by skin biopsy was examined by immunohistochemistry. Both cytokines were significantly elevated in the sera of patients with diffuse cutaneous SSc patients compared with healthy controls. Serum IL-17F levels correlated with modified Rodnan total skin thickness score, a semiquantitative measure of skin sclerosis, percent predicted forced vital capacity, percent predicted carbon monoxide lung diffusion capacity and serum levels of Krebs von den Lungen-6 and surfactant protein-D, serological markers of interstitial lung disease. Serum IL-17E levels were significantly correlated with percent predicted forced vital capacity and serum Krebs von den Lungen-6 levels. Serum levels of IL-17F and IL-17E also correlated with the prevalence of digital ulcers, and serum IL-17F levels were associated with elevated right ventricle systolic pressure values. In addition, IL-17RC and IL-17RB expression was increased in the skin tissues of diffuse cutaneous SSc patients. These results suggested that IL-17F and IL-17E could be involved in fibrosis and vasculopathy in SSc through their respective receptors in the affected organ tissues.

Distinctive association of peripheral immune cell phenotypes with capillaroscopic microvascular patterns in systemic sclerosis

OBJECTIVE

The pathological changes in SSc include immune system dysregulation and microvascular damage. However, the association of immune cell phenotype heterogeneity and microvascular abnormalities is unclear. The aim of this study is to elucidate this association in SSc.

METHODS

Peripheral blood mononuclear cells obtained from 150 SSc patients were used for comprehensive flow cytometric analysis based on the Human Immunology Project. Hierarchical cluster analysis was used to classify SSc patients into subgroups and their association with microvascular abnormalities, as assessed by nailfold videocapillaroscopy (i.e. 'early', 'active' and 'late' patterns), was analysed.

RESULTS

The proportions of activated CD4+ T cells, T cells re-expressing CD45RA, activated Th1 and Th17 cells and IgD-CD27- B cells were higher in SSc patients than in healthy individuals. Hierarchical cluster analysis stratified SSc patients into three groups: patients with few immune abnormalities (fewer abnormalities group), patients with high proportions of activated T and Treg cells (Treg-dominant group) and patients with high proportions of Tfh and plasmablasts (Tfh-dominant group). Age and disease duration were comparable among the groups. On the other hand, microvascular abnormalities, especially the 'late' nailfold videocapillaroscopy pattern, correlated with internal organ involvement. Among the groups stratified according to immune cell phenotype, the progression to the 'late' nailfold videocapillaroscopy pattern was more frequent in the Tfh-dominant group.

CONCLUSION

Our study confirmed the presence of immunophenotypic abnormalities in SSc. Immunological abnormalities were not uniform but rather limited to subpopulations, particularly the Tfh-dominant group, where they were highly associated with microvascular abnormalities and organ involvement.

Editor’s Pick: Systemic Sclerosis: The Role of YAP/TAZ in Disease Pathogenesis

Systemic sclerosis (SSc) is a systemic autoimmune condition of unknown cause. Yes-Associated Protein/Tafazzin (YAP/TAZ) are transcriptional coactivators previously demonstrated to be involved in cellular stretch biology, and form the principal effector molecules of the Hippo signalling pathway. The association between YAP/TAZ and stretch is contingent upon their cytoplasmic localisation (with nuclear translocation, the cell adopts a relaxed state). The author weighs the evidence for a central role for YAP/TAZ signalling in scleroderma spanning the major clinical features of the condition. Several of the features unique to SSc are mediated by cytoplasmic localisation of YAP/TAZ, including the stretch phenotype (through binding to NF-2), arterial lumenal obliteration (through their binding to angiomotin), the promotion of hypergammaglobulinaemia (via feedback to the upstream Hippo signalling molecule Mammalian Ste20-like Kinase 1), and the induction of B-Lymphocyte-Induced Maturation Protein-1 leading to the adoption of Th2 lineage, prominent in SSc. One observes that the induction of the fibrotic phenotype of scleroderma is mediated through GLI1/GLI2 (the effector molecules of the Hedgehog pathway). GLI1/GLI2 are induced to reciprocally enter the nucleus when YAP/TAZ is intracytoplasmic. The latter explains the characteristically increased connective tissue growth factor 2 and endothelin-1 expression. In this article, the author references some examples of the role of YAP/TAZ in the biophysically similar condition nephrogenic systemic fibrosis and suggests a role of YAP/TAZ cytoplasmic sequestration in programmed cell death protein 1-ligand antagonist-induced scleroderma.

Rituximab therapy is more effective than cyclophosphamide therapy for Japanese patients with anti-topoisomerase I-positive systemic sclerosis-associated interstitial lung disease

Systemic sclerosis-associated interstitial lung disease (SSc-ILD) is the most frequent cause of death for SSc but there is still no sufficient treatment available. Although cyclophosphamide (CYC) therapy is a common treatment which has shown statistical efficacy against SSc-ILD to date, its effects are temporary and not enough. Rituximab (RTX), the anti-CD20 monoclonal antibody, has recently shown efficacy in many autoimmune diseases. In SSc-ILD, RTX is also considered to be one of the novel treatment candidates. However, studies of SSc-ILD in Japanese treated with RTX have only a few case reports. Therefore, in this study, we retrospectively compared nine patients treated with RTX and 30 patients treated with CYC to investigate the efficacy of RTX treatment for Japanese anti-topoisomerase I-positive SSc-ILD patients. At the 24-month evaluation, the improvement rates of percent predicted of forced vital capacity and percent predicted of diffusing capacity of the lung carbon monoxide in the RTX-treated group were significantly higher than those in the CYC-treated group (20.6 ± 8.8% vs 1.1 ± 3.9%; P < 0.05 and 34.0 ± 6.0% vs -1.5 ± 2.8%; P < 0.01, respectively). In addition, skin thickness scores also showed a marked improvement from 13.5 points before the start of treatment to 5.8 points after 24 months by RTX therapy (P < 0.05). These results suggest that RTX treatment is more effective for Japanese SSc-ILD patients than CYC treatment. In the future, it is expected that large-scale clinical trials will show the usefulness of RTX treatment for SSc-ILD.

Skin thickness score as a surrogate marker of organ involvements in systemic sclerosis: a retrospective observational study

Background

Previous studies have shown the relationship between higher skin thickness score and the existence of organ involvements in systemic sclerosis (SSc). Here, we firstly investigated the correlation between skin thickness score and quantitative measurements of each organ involvement in Japanese patients with SSc.

Methods

All Japanese SSc patients hospitalized to our clinic for initial evaluation of SSc were selected. Skin thickness was evaluated by modified Rodnan total skin thickness score (mRSS). Relationship between mRSS and prevalence or incidence of organ involvements was examined by logistic analyses. Correlation between mRSS and quantitative measurements of organ involvements was examined by correlation analyses and regression analyses.

Results

We recruited 198 patients into our study. The mean disease duration was 7.3 years with the mean follow-up duration of 3.2 years. Multivariate logistic regression analyses revealed that higher mRSS is related to higher prevalence of interstitial lung disease (P < 0.05), restrictive impairment (P < 0.01), and diffusion impairment (P < 0.05) of the lung. Correlation analyses revealed mRSS negatively correlates with forced vital capacity (P < 0.001) and diffusing capacity (P < 0.001) of the lung. Correlation between longitudinal change of mRSS and that of forced vital capacity (P < 0.05) or diffusing capacity (P < 0.001) of the lung was also demonstrated.

Conclusions

Skin thickness score significantly correlates with quantitative measurements of lung involvement in Japanese patients with SSc.

Efficacy of BAFF in Monitoring Treatment Response in Early Vietnamese Systemic Sclerosis Patients

BACKGROUND:

B-cell activating factor (BAFF) is considered to have a role in the pathogenesis of systemic sclerosis (SSc).

AIM:

We conducted a longitudinal study on early SSc patients to determine the change in BAFF serum level after treatment and its association with organ involvements.

METHODS:

A total of 46 patients (32 diffuse, 14 limited) were recruited, among which 35 patients (24 diffuse, 11 limited) completed 12-month follow-up.

RESULTS:

Higher pretreatment BAFF levels were observed in patients with positive anti-topoisomerase antibody (ATA) (2252.1 ± 899.7 pg/ml versus 1475.5 ± 697.6 pg/ml in ATA-negative patients; p = 0.01) and muscular involvement (2741.9 ± 1039.9 pg/ml versus 1897.2 ± 762.9 pg/ml in patients without muscular involvement; p = 0.005). Lower levels were observed in patients with interstitial lung disease (ILD) (1926.7 ± 757.9 pg/ml versus 2721.6 ± 1131.4 pg/ml in non-ILD patients; p = 0.01). After treatment, BAFF level reduced significantly in diffuse SSc patients (1652.2 ± 892.7 pg/ml versus 2147.6 ± 945.5 pg/ml before treatment; p = 0.03).

CONCLUSION:

Patients with worsening outcome had the highest pretreatment BAFF level and was associated with increased BAFF level after treatment. BAFF can be used to predict and monitor patients’ response to therapy.

Cutaneous Manifestations of Scleroderma and Scleroderma-Like Disorders: a Comprehensive Review

Scleroderma refers to an autoimmune connective tissue fibrosing disease, including three different subsets: localized scleroderma, limited cutaneous systemic sclerosis, and diffuse cutaneous systemic sclerosis with divergent patterns of organ involvement, autoantibody profiles, management, and prognostic implications. Although systemic sclerosis is considered the disease prototype that causes cutaneous sclerosis, there are many other conditions that can mimic and be confused with SSc. They can be classified into immune-mediated/inflammatory, immune-mediated/inflammatory with abnormal deposit (mucinoses), genetic, drug-induced and toxic, metabolic, panniculitis/vascular, and (para)neoplastic disorders according to clinico-pathological and pathogenetic correlations. This article reviews the clinical presentation with emphasis on cutaneous disease, etiopathogenesis, diagnosis, and treatment options available for the different forms of scleroderma firstly and for scleroderma-like disorders, including scleromyxedema, scleredema, nephrogenic systemic fibrosis, eosinophilic fasciitis, chronic graft-versus-host disease, porphyria cutanea tarda, diabetic stiff-hand syndrome (diabetic cheiroartropathy), and other minor forms. This latter group of conditions, termed also scleroderma mimics, sclerodermiform diseases, or pseudosclerodermas, shares the common thread of skin thickening but presents with distinct cutaneous manifestations, skin histology, and systemic implications or disease associations, differentiating each entity from the others and from scleroderma. The lack of Raynaud's phenomenon, capillaroscopic abnormalities, or scleroderma-specific autoantibodies is also important diagnostic clues. As cutaneous involvement is the earliest, most frequent and characteristic manifestation of scleroderma and sclerodermoid disorders, dermatologists are often the first-line doctors who must be able to promptly recognize skin symptoms to provide the affected patient a correct diagnosis and appropriate management.

Decreased CD22 expression and intracellular signaling aberrations in B cells of patients with systemic sclerosis

The objective of the study was to explore the phenotype and intracellular signaling events of B cells in patients with systemic sclerosis (SSc). Peripheral blood B cell surface markers CD19 and CD22 were evaluated by flow cytometry in 23 patients with SSc and seven healthy individuals. Levels of intracellular kinases Lyn, Syk and P-Y 348 Syk along with phosphatase SHP-1 were examined with Western immunoblotting in selected patients. P-Y 822 CD22 was subsequently evaluated flow cytometrically in antigen receptor stimulated B cells. A statistically significant decrease in CD22 B cell surface expression was found in the diffuse subset of patients (median CD22 MFI ± SD was 5.90 ± 2.35 vs 10.20 ± 1.88 for patients vs healthy controls respectively; p = 0.021), while no statistically significant change was found regarding CD19. CD22 underexpression was more pronounced when interstitial lung disease (ILD) was present (median CD22 MFI ± SD was 5.90 ± 2.25 vs 10.20 ± 1.88 for patients with ILD vs healthy controls respectively; p = 0.011). CD22 phosphorylation following B cell receptor (BCR) stimulation was also found to be impaired in patients with diffuse SSc (median change in MFI ± SD was 0.28 ± 0.09 vs 0.38 ± 0.08 for patients vs healthy controls respectively; p = 0.034). Low CD22 expression was arithmetically correlated with kinase Lyn underexpression (Pearson coefficient 0.926; p = ns) in B cells from a small sample of patients. These results suggest that CD22 underexpression and impaired phosphorylation along with implications for Lyn kinase aberrations could contribute to the activated B cell phenotype in SSc.

Polymorphisms in miRNA genes and their involvement in autoimmune diseases susceptibility

MicroRNAs (miRNAs) are small non-coding RNA molecules that negatively regulate the expression of multiple protein-encoding genes at the post-transcriptional level. MicroRNAs are involved in different pathways, such as cellular proliferation and differentiation, signal transduction and inflammation, and play crucial roles in the development of several diseases, such as cancer, diabetes, and cardiovascular diseases. They have recently been recognized to play a role also in the pathogenesis of autoimmune diseases. Although the majority of studies are focused on miRNA expression profiles investigation, a growing number of studies have been investigating the role of polymorphisms in miRNA genes in the autoimmune diseases development. Indeed, polymorphisms affecting the miRNA genes can modify the set of targets they regulate or the maturation efficiency. This review is aimed to give an overview about the available studies that have investigated the association of miRNA gene polymorphisms with the susceptibility to various autoimmune diseases and to their clinical phenotypes.

Pathogenic roles of B lymphocytes in systemic sclerosis

Systemic sclerosis (SSc) is a collagen disease characterized by autoimmunity and excessive extracellular matrix deposition in the skin and visceral organs. Although the pathogenic relationship between systemic autoimmunity and the clinical manifestations of SSc remains unknown, SSc patients show a variety of abnormal immune activation including the production of disease-specific autoantibodies and cytokine production. Many recent studies have demonstrated that immune cells, including T cells, B cells, and macrophages, have a variety of immunological abnormalities in SSc. So far, several groups and our group reported that B cells play a critical role in systemic autoimmunity and disease expression through various functions, such as cytokine production, lymphoid organogenesis, and induction of other immune cell activation in addition to autoantibody production. Recent studies show that B cells from SSc patients demonstrate an up-regulated CD19 expression, a crucial regulator of B cell activation, which induces chronic hyper-reactivity of memory B cells and SSc-specific autoantibody production and also causes fibrosis of several organs. Furthermore, in SSc-model mice, such as tight-skin mice, bleomycin-induced SSc model mice, and DNA topoisomerase I and complete Freund's adjuvant-induced SSc model mice, have abnormal B cell activation which associates with skin and lung fibrosis. Indeed, B cell depletion therapy using anti-CD20 Ab, Rituximab, is considered to one potential beneficial treatment for patients with SSc. However, there is no direct evidence which can explain how B cells, especially autoantigen-reactive B cells, progress or regulate disease manifestations of SSc. Collectively, B cell abnormalities in SSc is most likely participating in fibrosis and tissue damage of SSc. If the relationship between SSc-specific tissue damage and B cell abnormalities is revealed, these findings lead to novel effective therapy for SSc.

Transforming growth factor-β signaling in systemic sclerosis

Systemic sclerosis (SSc) is a complex, multiorgan autoimmune disease of unknown etiology. Manifestation of the disease results from an interaction of three key pathologic features including irregularities of the antigen-specific immune system and the non-specific immune system, resulting in autoantibody production, vascular endothelial activation of small blood vessels, and tissue fibrosis as a result of fibroblast dysfunction. Given the heterogeneity of clinical presentation of the disease, a lack of universal models has impeded adequate testing of potential therapies for SSc. Regardless, recent research has elucidated the roles of various ubiquitous molecular mechanisms that contribute to the clinical manifestation of the disease. Transforming growth factor β (TGF-β) has been identified as a regulator of pathological fibrogenesis in SSc. Various processes, including cell growth, apoptosis, cell differentiation, and extracellular matrix synthesis are regulated by TGF-β, a type of cytokine secreted by macrophages and many other cell types. Understanding the essential role TGF-β pathways play in the pathology of systemic sclerosis could provide a potential outlet for treatment and a better understanding of this severe disease.

Analysis of complement biomarkers in systemic sclerosis indicates a distinct pattern in scleroderma renal crisis

BACKGROUND

The complement system has been implicated in pathogenesis of systemic sclerosis (SSc). The goal of the present study was to evaluate improved complement biomarkers in SSc.

METHODS

The presence of C4d, reflecting activation of the classical/lectin pathways, C3bBbP corresponding to activation of the alternative pathway, and soluble terminal complement complexes (all complement pathways), was measured in plasma samples by enzyme-linked immunosorbent assay and correlated to clinical parameters. The study included 81 patients with limited cutaneous SSc and 41 with diffuse cutaneous SSc, as well as 47 matched healthy controls and 81 patients with rheumatoid arthritis, 22 with psoriatic arthritis and 20 with ankylosing spondylitis. Skin and kidney biopsies of selected patients were stained to detect deposited C3b as a marker of local complement activation.

RESULTS

Biomarkers of activation of all complement pathways were increased in SSc compared with healthy controls and were similar to those in other rheumatic diseases. When patients with SSc were divided into subgroups, a distinct pattern of complement markers was observed in individuals with scleroderma renal crisis (SRC). By functional assay, we confirmed a significant decrease in complement haemolytic activity in SRC vs. non-SRC patients, indicating complement consumption. Further, we detected glomerular deposits of C3b in some patients with SRC.

CONCLUSIONS

The data indicate that complement activation is an important feature of SRC.

B-cells in systemic sclerosis: emerging evidence from genetics to phenotypes

PURPOSE OF REVIEW

This review aims to summarize current evidence for a role of B-cells in the pathogenesis of systemic sclerosis (SSc) from genetics to phenotypes, with an emphasis on recent insights.

RECENT FINDINGS

Multiple genomic analyses have associated several B-cell signalling genes with SSc. Moreover, interesting B-cell subset alterations and activation/memory marker changes have also been documented in SSc. Co-cultures of blood B-cells with dermal fibroblasts isolated from SSc patients demonstrated the induction of collagen, interleukin (IL)-6, transforming growth factor (TGF)-β1, IL-1β and chemokine (c-c motif) ligand 2 (CCL2) in the fibroblasts, following potential B-cell cues delivered to the fibroblasts. Plasma cell gene signatures were elevated in SSc patients' blood, and highly correlated with collagen gene expression. Finally, anti-CD20 B-cell depletion therapy not only improved skin disease but also preserved interstitial lung disease in early diffuse cutaneous disease.

SUMMARY

Thus, there is resounding evidence that B-cells play a pivotal role in pathogenesis of SSc. However, the molecular pathways through which B-cells may direct fibroblast function, SSc disease development and progression remain unclear, and warrant further study.

B cell abnormalities and therapeutic strategies in systemic sclerosis

One of the major roles of B cells is to generate antibodies to specific antigens. Secreted antibodies are the principal molecules involved in humoral immunity, with the capacity not only to neutralize pathogens, but also to enhance their elimination by activating phagocytosis or complement proteins. Recently, it has been highlighted that B cells exert important regulatory roles independent of their antibody producing function. These roles include efficiently presenting antigens to the T cells, secreting cytokines, and inducing immune cell differentiation. Thus, B cells have emerged as cells that play crucial roles in immune systems in addition to producing antibodies. Systemic sclerosis (SSc) is characterized by autoimmunity and tissue fibrosis of several organs. Although the pathogenic relationship between systemic autoimmunity and the clinical manifestations of SSc remains unknown, SSc patients display a variety of abnormal immune activation including the production of disease-specific autoantibodies. Previous studies have demonstrated that immune cells, mainly including B cells, play a critical role in systemic autoimmunity and disease expression, though the role of autoimmunity in generating the clinical and pathologic phenotype in SSc remains uncertain. SSc patients have B cell abnormalities characterized by chronic hyper-reactivity of memory B cells. Although distinct subsets of autoantibodies do not have a proven pathogenic role, they are selectively associated with unique disease manifestations. To date, the treatment of SSc has largely relied on cytotoxic immunosuppressants and corticosteroids. Although this has resulted in improved disease survival, these patients may still suffer severe adverse events and refractory disease to conventional immunosuppressive therapies. Recently, clinical trials involving the chimeric monoclonal antibody rituximab have raised high expectations. B cell depleting therapy with rituximab offers a promising treatment for the rheumatic autoimmune diseases including SSc. This article reviews the current knowledge of B cell biology and pathogenesis in SSc as well as the therapeutic approaches focusing on the targeting of B cell specific surface molecules and on the blocking of B cell activation and survival.

Genetic factors and systemic sclerosis

Systemic sclerosis (SSc) is a rare connective tissue disease of unknown etiology characterized by chronic inflammation and fibrosis of the skin, vascular abnormalities, and variable involvement of organs including kidneys, gastrointestinal tract, heart, and lungs. SSc shows a complex etiology in which both environmental and genetic factors seem to influence the onset and outcome of the disease. We provide an extensive overview of the genetic factors and epigenetic modifications and what their knowledge has revealed in terms of etiopathogenesis of SSc.

Role of B cells in the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is an orphan disease characterized by progressive fibrosis of the skin and internal organs. Aside from vasculopathy and fibrotic processes, its pathogenesis involves an aberrant activation of immune cells, among which B cells seem to play a significant role. Indeed, B cell homeostasis is disturbed during SSc: the memory subset is activated and displays an increased susceptibility to apoptosis, which is responsible for their decreased number. This chronic loss of B cells enhances bone marrow production of the naïve subset that accounts for their increased number in peripheral blood. This permanent activation state can be explained mainly by two mechanisms: a dysregulation of B cell receptor (BCR) signaling, and an overproduction of B cell survival signals, B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL). These disturbances of B cell homeostasis induce several functional anomalies that participate in the inflammatory and fibrotic events observed during SSc: autoantibody production (some being directly pathogenic); secretion of pro-inflammatory and pro-fibrotic cytokines (interleukin-6); direct cooperation with other SSc-involved cells [fibroblasts, through transforming growth factor-β (TGF-β) signaling, and T cells]. These data justify the evaluation of anti-B cell strategies as therapeutic options for SSc, such as B cell depletion or blockage of B cell survival signaling.

Anterior segment parameters and eyelids in systemic sclerosis

To evaluate main numerical parameters of anterior segment and the effects of eyelid skin changes on these parameters in patients with systemic sclerosis (SSc). Thirty-four patients with SSc and 34 healthy individuals were enrolled. Besides full eye examination, anterior segment measurements including anterior chamber depth (ACD), anterior chamber volume, anterior chamber angle width, central corneal thickness, pupil size, corneal volume and keratometry were obtained using a Sirius Scheimpflug/Placido photography-based topography system. Eyelid thickness was evaluated using the scala of the modified Rodnan skin score and the patients were subgrouped with respect to these scores to evaluate the effect of eyelid thickening on the anterior segment parameters. Age and sex distributions of the groups were similar (p > 0.05). SSc patients had steeper and thinner corneas, smaller corneal volumes, narrower, shallower and smaller anterior segments but only the mean ACD value of right eyes was found significantly less than those of the controls (p = 0.047). The mean ACD values of SSc subgroup patients with moderate to severe eyelid thickening (50 %) had lower ACD measurements compared to those of control group. (p = 0.043 for the right eyes, p = 0.070 for the left eyes). However, SSc subgroup patients with none to mild eyelid thickening (50 %) had similar anterior segment parameters with control subjects (p > 0.05). Anterior chamber parameters of the SSc patients could show significant differences. These differences occur parallel to the eyelid changes but not secondary to it.