Gene expression profiling offers insights into the role of innate immune signaling in SSc

Skin Gene Expression Profiles in Systemic Sclerosis: From Clinical Stratification to Precision Medicine

Systemic sclerosis, also known as scleroderma or SSc, is a condition characterized by significant heterogeneity in clinical presentation, disease progression, and response to treatment. Consequently, the design of clinical trials to successfully identify effective therapeutic interventions poses a major challenge. Recent advancements in skin molecular profiling technologies and stratification techniques have enabled the identification of patient subgroups that may be relevant for personalized treatment approaches. This narrative review aims at providing an overview of the current status of skin gene expression analysis using computational biology approaches and highlights the benefits of stratifying patients upon their skin gene signatures. Such stratification has the potential to lead toward a precision medicine approach in the management of SSc.

Mucosal and systemic lymphoid immune responses against Clostridium perfringens strains with variable virulence in the production of necrotic enteritis in broiler chickens

Necrotic enteritis (NE), caused by Clostridium perfringens, is an economically important disease of chickens. Although NE pathogenesis is moderately well studied, the host immune responses against C. perfringens are poorly understood. The present study used an experimental NE model to characterize lymphoid immune responses in the caecal tonsils (CT), bursa of Fabricius, Harderian gland (HG) and spleen tissues of broiler chickens infected with four netB+ C. perfringens strains (CP1, CP5, CP18, and CP26), of which CP18 and CP26 strains also carried the tpeL gene. The gross and histopathological lesions in chickens revealed CP5 to be avirulent, while CP1, CP18, and CP26 strains were virulent with CP26 being "very virulent". Gene expression analysis showed that, while the virulent strains induced a significantly upregulated expression of pro-inflammatory IL-1β gene in CT, the CP26-infected birds had significantly higher CT transcription of IFNγ and IL-6 pro-inflammatory genes compared to CP5-infected or uninfected chickens. Furthermore, CP26 infection also led to significantly increased bursal and HG expression of the anti-inflammatory/regulatory genes, IL-10 or TGFβ, compared to control, CP5 and CP1 groups. Additionally, the splenic pro- and anti-inflammatory transcriptional changes were observed only in the CP26-infected chickens. An antibody-mediated response, as characterized by increased IL-4 and/or IL-13 transcription and elevated IgM levels in birds infected with virulent strains, particularly in the CP26-infected group compared to uninfected controls, was also evident. Collectively, our findings suggest that lymphoid immune responses during NE in chickens are spatially regulated such that the inflammatory responses against C. perfringens depend on the virulence of the strain.

Clinical and laboratory characterization of patients with localized scleroderma and response to UVA-1 phototherapy: In vivo and in vitro skin models

BACKGROUND/PURPOSE

Localized scleroderma (LS) is a rare disease leading to progressive hardening and induration of the skin and subcutaneous tissues. LS is responsive to UVA-1 phototherapy, though its exact mechanism of action dermal fibrosis is yet to be fully elucidated. We aimed to investigate the molecular changes induced by UVA-1 rays in human primary fibroblasts cultures.

METHODS

A total of 16 LS patients were treated with medium-dose UVA-1 phototherapy. At baseline, during and after therapy, Localized Scleroderma Assessment Tool, Dermatology Life Quality Index and lesions' staging and mapping were performed along with high-frequency ultrasound (HFUS) examination for dermal thickness assessment. Gene expression analysis for 23 mRNA transcripts, in vitro UVA-1 irradiation and viability tests were realized on lesional fibroblasts' primary cultures, before and 3 months after therapy.

RESULTS

The dermal thickness, the LoSCAT and the DLQI progressively decreased starting from the last phototherapy session up to the 6 and 9 month follow-ups (-57% and -60%, respectively). Molecular gene analysis (rt-PCR) revealed that UVA-1 phototherapy exerts multiple effects: the activation of specific anti-fibrotic pathways (e.g., overexpression of CTHRC1 and metalloproteases 1, 2, 7, 8, 9, 12, suppression of TIMP-1), the downregulation of peculiar pro-fibrotic pathways (e.g., downregulation of TGF-ß, TGF-ßrII, Grb2, SMAD 2/3, TNRSF12A, CTGF) through a significant overexpression of IL-1ß; the stabilization of collagen synthesis acting on genes COL1A1, COL3A1, COL8A1, COL10A1, COL12A1.

CONCLUSION

UVA-1 phototherapy adds significant benefits in local tissue remodeling, rebalancing the alteration between pro-fibrotic and anti-fibrotic pathways; these changes can be well monitored by HFUS.

Taraxacum mongolicum extract inhibited malignant phenotype of triple-negative breast cancer cells in tumor-associated macrophages microenvironment through suppressing IL-10 / STAT3 / PD-L1 signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Triple-negative breast cancer (TNBC) is the most aggressive and the worst prognosis breast cancer with limited treatment options. Taraxacum mongolicum (also called dandelion) is a traditional Chinese medicine has been used to treat mastitis, breast abscess, and hyperplasia of mammary glands since ancient times. In modern pharmacological research, dandelion has been proven with anti-breast cancer activities. We previously reported that dandelion extract could induce apoptosis in TNBC cells. However, its anti-tumor effects and mechanisms in the tumor microenvironment have not yet been elucidated.

AIM OF THE STUDY

Tumor-associated macrophages (TAMs) play an important role in regulating the interaction between tumor cells and the immune system. The present study aimed to investigate the effects and mechanisms of dandelion extract on TNBC cells under the microenvironment of TAMs, as well as its influence on the polarization of M2 macrophages.

MATERIALS AND METHODS

M2 macrophages were induced by phorbol-12-myristate 13-acetate (PMA) and interleukin 4 (IL-4), and verified by flow cytometry, quantitative RT-PCR (qRT-PCR), Western blotting, and ELISA. MDA-MB-231 and MDA-MB-468 TNBC cells were co-cultured with the supernatant of M2 macrophage which providing the TAMs microenvironment. The antitumor activity of dandelion extract in TNBC cells was evaluated by MTT assay. The invasive and migratory capacity of TNBC cells was measured by transwell assays. The expression of protein and gene was assessed by Western blotting and qRT-PCR, respectively.

RESULTS

TAMs microenvironment promoted the proliferation, migration, and invasion of TNBC cells. However, dandelion extract inhibited the malignant property of MDA-MB-231 and MDA-MB-468 cells induced by TAMs. Both of TAMs and IL-10 caused STAT3 activation and PD-L1 higher expression, the immunosuppressive molecules in TNBC cells, and this effect can be attenuated by IL-10 neutralizing antibody. Dandelion extract exerted inhibition on STAT3 and PD-L1 in TNBC cells under TAMs microenvironment. Furthermore, in M2 macrophages, dandelion extract remarkably promoted the expression of M1-like marker TNF-α, IL-8, and iNOS, but reduced M2-like marker IL-10, CD206, Arginase-1, and TGF-β.

CONCLUSION

Dandelion extract inhibited the proliferation, migration and invasion of TNBC cells in TAMs microenvironment through suppressing IL-10/STAT3/PD-L1 immunosuppressive signaling pathway. Furthermore, dandelion extract promoted the polarization of macrophages from M2 to M1 phenotype. Thus, our results indicated that dandelion may serve as a promising therapeutic strategy for TNBC by modulating tumor immune microenvironment.

Systemic Sclerosis and Pulmonary Disease

Systemic sclerosis is a complex, often progressive, multisystem autoimmune disease. It is commonly categorized into limited cutaneous or diffuse cutaneous systemic sclerosis. There is near universal involvement of skin fibrosis and gastrointestinal dysfunction, but lung disease is not only common but also a most serious complication. Severe lung disease is the top cause of mortality, displacing scleroderma renal crisis as the leading cause of death. Whether there is limited cutaneous or diffuse cutaneous manifestations can be predictive of what type of lung disease that can present in the patient. Limited cutaneous systemic sclerosis patients tend to have pulmonary hypertension whereas diffuse cutaneous systemic sclerosis patients tend to have interstitial lung disease. There are more rare phenotypes associated with antibodies Th/To and U3RNP that can have both pulmonary hypertension and interstitial lung disease concomitantly. There are inherent challenges in the management for both pulmonary hypertension and interstitial lung disease but with the focus on early diagnosis for each of these lung complications, treatment may have a higher chance of efficacy.

Analysis of gene expression profiles and protein-protein interaction networks in multiple tissues of systemic sclerosis

Background

Systemic sclerosis (SSc), a multi-organ disorder, is characterized by vascular abnormalities, dysregulation of the immune system, and fibrosis. The mechanisms underlying tissue pathology in SSc have not been entirely understood. This study intended to investigate the common and tissue-specific pathways involved in different tissues of SSc patients.

Methods

An integrative gene expression analysis of ten independent microarray datasets of three tissues was conducted to identify differentially expressed genes (DEGs). DEGs were mapped to the search tool for retrieval of interacting genes (STRING) to acquire protein–protein interaction (PPI) networks. Then, functional clusters in PPI networks were determined. Enrichr, a gene list enrichment analysis tool, was utilized for the functional enrichment of clusters.

Results

A total of 12, 2, and 4 functional clusters from 619, 52, and 119 DEGs were determined in the lung, peripheral blood mononuclear cell (PBMC), and skin tissues, respectively. Analysis revealed that the tumor necrosis factor (TNF) signaling pathway was enriched significantly in the three investigated tissues as a common pathway. In addition, clusters associated with inflammation and immunity were common in the three investigated tissues. However, clusters related to the fibrosis process were common in lung and skin tissues.

Conclusions

Analysis indicated that there were common pathological clusters that contributed to the pathogenesis of SSc in different tissues. Moreover, it seems that the common pathways in distinct tissues stem from a diverse set of genes.

Macrophages in Systemic Sclerosis: Novel Insights and Therapeutic Implications

PURPOSE OF REVIEW

Macrophages play key roles in tissue homeostasis and immune surveillance, mobilizing immune activation in response to microbial invasion and promoting wound healing to repair damaged tissue. However, failure to resolve macrophage activation can lead to chronic inflammation and fibrosis, and ultimately to pathology. Activated macrophages have been implicated in the pathogenesis of systemic sclerosis (SSc), although the triggers that induce immune activation in SSc and the signaling pathways that underlie aberrant macrophage activation remain unknown.

RECENT FINDINGS

Macrophages are implicated in fibrotic activation in SSc. Targeted therapeutic interventions directed against SSc macrophages may ameliorate inflammation and fibrosis. While current studies have begun to elucidate the role of macrophages in disease initiation and progression, further work is needed to address macrophage subset heterogeneity within and among SSc end-target tissues to determine the disparate functions mediated by these subsets and to identify additional targets for therapeutic intervention.

Human leukocyte antigen (HLA)-DRB1 allele polymorphisms and systemic sclerosis

Objectives: Human leukocyteantigen (HLA) is the most important gene for immune system regulation. Although studies have evaluated the association between HLA-DRB1 allele polymorphisms and systemic sclerosis (SSc), their results are still controversial. We performed a meta-analysis to assess the association of HLA-DRB1 alleles with risk of SSc.Methods: Electronic database were systematically searched for articles, a total of 11 case-control studies including 3268 cases and 5548 controls were analyzed. Odds ratio (ORs) and 95% confidence intervals were used to assess the association of HLA-DRB1 alleles with SSc. The relationship between SSc-related autoantibodies and DRB1 alleles was also analyzed.Results: In the overall analysis, four alleles (DRB1*04:03, DRB1*08, DRB1*11, and DRB1*11:04) increased the risk of SSc; however, five alleles (DRB1*07, DRB1*11:01, DRB1*13, DRB1*13:01, and DRB1*14) had the opposite effect. Analysis of subgroups by ethnicity indicate that DRB1*11:01 and DRB1*13:01 confer a protective effect in Caucasians, while DRB1*11:04 was associated with a higher risk of SSc. For Asian, DRB1*13:02 was found to be a protective factor. In addition, the frequency of DRB1*11:04 alleles was significantly increased in ATA⁺ SSc patients compared with ATA^- SSc patients.Conclusion: DRB1*04:03, DRB1*08, DRB1*11, and DRB1*11:04 were associated with the risk of SSc. Additionally, DRB1*11 and DRB1*11:04 were association with ATAs.

Innate Immunity in Systemic Sclerosis Fibrosis: Recent Advances

Systemic sclerosis (SSc) is a heterogeneous autoimmune disease characterized by three interconnected hallmarks (i) vasculopathy, (ii) aberrant immune activation, and (iii) fibroblast dysfunction leading to extracellular matrix deposition and fibrosis. Blocking or reversing the fibrotic process associated with this devastating disease is still an unmet clinical need. Although various components of innate immunity, including macrophages and type I interferon, have long been implicated in SSc, the precise mechanisms that regulate the global innate immune contribution to SSc pathogenesis remain poorly understood. Recent studies have identified new innate immune players, such as pathogen-recognition receptors, platelet-derived danger-associated molecular patterns, innate lymphoid cells, and plasmacytoid dendritic cells in the pathophysiology of SSc, including vasculopathy and fibrosis. In this review, we describe the evidence demonstrating the importance of innate immune processes during SSc development with particular emphasis on their role in the initiation of pathology. We also discuss potential therapeutic options to modulate innate immune cells or signaling in SSc that are emerging from these recent advances.

Characterization of inflammatory cell infiltrate of scleroderma skin: B cells and skin score progression

BACKGROUND

The purpose of this study was to investigate the frequency and the distribution of inflammatory cell infiltrate in two sets of cutaneous biopsies derived from clinically affected and unaffected skin in patients with systemic sclerosis (SSc) and to test correlation between the cell infiltrate and the progression of skin involvement.

METHODS

Skin was immunohistochemically assessed to identify CD68, CD3, CD20 and CD138-positive (+) cells in clinically affected and unaffected skin in 28 patients with SSc. Patients were followed for 6 months and the characteristics of the infiltrate were analyzed according to disease duration, clinical features and skin involvement progression.

RESULTS

In all SSc cutaneous specimens, cellular infiltrates were found in a perivascular location predominantly in the mid and deeper portions of the dermis. All the analyzed biopsies showed a CD3⁺ and CD68⁺ cell infiltrate and the mean number of CD3⁺ and of CD68⁺ cells was higher in clinically involved skin (CD3⁺, 71.7 ± 34.6 and CD68⁺, 26.3 ± 8.4, respectively) than in clinically uninvolved skin (CD3⁺, 45.7 ± 36.0 and CD68⁺, 13.6 ± 6.1, respectively) (p < 0.001 for both comparisons). CD20⁺ cells were found in 17 (60.7%) patients and in these patients the mean number of CD20⁺ cells was higher in clinically involved (4.7 ± 5.9) than in uninvolved skin (1.9 ± 2.9), (p = 0.04). There was a greater number of CD20⁺ cells in patients with early SSc compared with patients with long-standing disease. CD138⁺ cells were found in 100% of biopsies of clinically involved skin and in 89.3% of biopsies of uninvolved skin. The mean number of CD138⁺ cells was higher in clinically involved skin (3.6 ± 2.3) than in clinically uninvolved skin (1.9 ± 1.7), (p < 0.001). Seven patients experienced more than 20% worsening in the skin score after 6 months of follow up; all of them had a CD20⁺ skin infiltrate on biopsy of clinically involved skin.

CONCLUSIONS

Our results confirm that mononuclear cells are present in the skin of all patients with SSc, underlining the role of inflammatory cell infiltrates in skin involvement in SSc. B cells in the skin seem to characterize patients with early diffuse skin disease and to correlate with skin progression.

Mycophenolate Mofetil Treatment of Systemic Sclerosis Reduces Myeloid Cell Numbers and Attenuates the Inflammatory Gene Signature in Skin

Fewer than half of patients with systemic sclerosis demonstrate modified Rodnan skin score improvement during mycophenolate mofetil (MMF) treatment. To understand the molecular basis for this observation, we extended our prior studies and characterized molecular and cellular changes in skin biopsies from subjects with systemic sclerosis treated with MMF. Eleven subjects completed ≥24 months of MMF therapy. Two distinct skin gene expression trajectories were observed across six of these subjects. Three of the six subjects showed attenuation of the inflammatory signature by 24 months, paralleling reductions in CCL2 mRNA expression in skin and reduced numbers of macrophages and myeloid dendritic cells in skin biopsies. MMF cessation at 24 months resulted in an increased inflammatory score, increased CCL2 mRNA and protein levels, modified Rodnan skin score rebound, and increased numbers of skin myeloid cells in these subjects. In contrast, three other subjects remained on MMF >24 months and showed a persistent decrease in inflammatory score, decreasing or stable modified Rodnan skin score, CCL2 mRNA reductions, sera CCL2 protein levels trending downward, reduction in monocyte migration, and no increase in skin myeloid cell numbers. These data summarize molecular changes during MMF therapy that suggest reduction of innate immune cell numbers, possibly by attenuating expression of chemokines, including CCL2.

Black, White, and Gray: Macrophages in Skin Repair and Disease

PURPOSE OF REVIEW

Macrophages alter their responses during the temporal stages of wound healing. During the inflammatory phase macrophages perform phagocytosis. During neovascularization macrophages activate angiogenesis. In the proliferation phase of wound healing, macrophages deposit extracellular matrix and during wound resolution macrophages phagocytize excessive cellular components. This review addresses how these changing phenotypes affect skin repair and disease.

RECENT FINDINGS

Macrophages can determine the outcome of repair and can shift the normal wound healing response into fibrosis or chronic wounds. Emerging single cell technologies for the first time provide us with tools to uncover macrophage origin, heterogeneity and function.

SUMMARY

Macrophages may exist as one population where all cells alter their phenotype in response to signals from the microenvironment. Alternatively, macrophages may exist as distinct subsets that can control wound outcomes. A clarified understanding will strengthen our knowledge of skin biology and aid in the development of wound healing therapies.

Systemic sclerosis

Systemic sclerosis, also called scleroderma, is an immune-mediated rheumatic disease that is characterised by fibrosis of the skin and internal organs and vasculopathy. Although systemic sclerosis is uncommon, it has a high morbidity and mortality. Improved understanding of systemic sclerosis has allowed better management of the disease, including improved classification and more systematic assessment and follow-up. Additionally, treatments for specific complications have emerged and a growing evidence base supports the use of immune suppression for the treatment of skin and lung fibrosis. Some manifestations of the disease, such as scleroderma renal crisis, pulmonary arterial hypertension, digital ulceration, and gastro-oesophageal reflux, are now treatable. However, the burden of non-lethal complications associated with systemic sclerosis is substantial and is likely to become more of a challenge. Here, we review the clinical features of systemic sclerosis and describe the best practice approaches for its management. Furthermore, we identify future areas for development.

FOXP3, ICOS and ICOSL gene polymorphisms in systemic sclerosis: FOXP3 rs2294020 is associated with disease progression in a female Italian population

Systemic sclerosis (SSc), an autoimmune disorder, is characterized by vasculopathy, inflammation, progressive perivascular and interstitial fibrosis. Its pathogenesis is largely unknown, however strong evidences suggest that genetic predisposition may contribute to SSc development. Several gene polymorphisms involved in regulatory T cell function have been identified in many autoimmune diseases, including SSc. Moreover, dysregulation of co-stimulatory and/or co-inhibitory signals, including ICOS signalling, can lead to autoimmunity. The aim of the present study was to investigate the association of the FOXP3 rs2294020, ICOS rs6726035 and ICOSL rs378299 SNPs with both the susceptibility and the progression to SSc in an Italian case-series of patients. SNP genotyping results were successfully obtained from a total of 350 subjects including 166 individuals with SSc and 184 healthy controls. Although analysis tests did not show any significant associations between the SNPs under study and susceptibility to SSc, the occurrence of FOXP3 rs2294020 in female patients was associated with decreased time to progression from early to definite SSc (allelic model: HR=1.43; CI=1.03-1.99; p=0.03; dominant model: HR=1.54; CI=1.04-2.28; p=0.03). The inclusion of presence of ACA autoantibodies in the model did not significantly change the estimates. No conclusions can be drawn for the susceptibility to the disease or the time to progression in men due to the low statistical power. This study provides evidence of the association of rs2294020 with SSc evolution in female patients, modulating the time of progression from the diagnosis of early SSc to the diagnosis of definite SSc, while no effect on SSc susceptibility per se was found. rs2294020 may be considered a disease-modifying gene-variant rather than a disease-susceptibility SNP in SSc.

Toll-Like Receptor-4 Signaling Drives Persistent Fibroblast Activation and Prevents Fibrosis Resolution in Scleroderma

Significance: This review provides current overview of the emerging role of innate immunity in driving fibrosis, and preventing its resolution, in scleroderma (systemic sclerosis, SSc). Understanding the mechanisms of dysregulated innate immunity in fibrosis and SSc will provide opportunities for therapeutic interventions using novel agents and repurposed existing drugs. Recent Advances: New insights from genomic and genetic studies implicate components of innate immune signaling such as pattern recognition receptors (PRRs), downstream signaling intermediates, and endogenous inhibitors, in fibrosis in SSc. Recent studies distinguish innate immune signaling in tissue-resident myofibroblasts and bone marrow-derived immune cells and define their roles in the development and persistence of tissue fibrosis. Critical Issues: Activation of toll-like receptors (TLRs) and other PRR mechanisms occurs in resident nonimmune cells within injured tissue microenvironments. These cells respond to damage-associated molecular patterns (DAMPs), such as tenascin-C that are recognized as danger signals, and elicit matrix production, cytokine secretion, and myofibroblast transformation and survival. When these responses persist due to constitutive TLR activation or impaired termination by endogenous inhibitors, they interfere with fibrosis resolution. The genetic basis and molecular mechanisms of these phenomena in the context of fibrosis are under current investigation. Future Directions: Precise delineation of the pathogenic DAMPs, their interaction with TLRs and other PRRs, the downstream signaling pathways and transcriptional events, and the fibroblast-specific regulation and function of endogenous inhibitors of innate immunity, will form the foundation for innovative targeted therapies to block fibrosis by reestablishing balanced innate immune signaling in fibroblasts.

Pathophysiological Mechanisms in Sclerosing Skin Diseases

Sclerosing skin diseases represent a large number of distinct disease entities, which include systemic sclerosis, localized scleroderma, and scleredema adultorum. These pathologies have a common clinical appearance and share histological features. However, the specific interplay between cytokines and growth factors, which activate different mesenchymal cell populations and production of different extracellular matrix components, determines the biomechanical properties of the skin and the clinical features of each disease. A better understanding of the mechanisms underlying these events is prerequisite for developing novel targeted therapeutic approaches.

The Microbiome in Connective Tissue Diseases and Vasculitides: An Updated Narrative Review

Objective

To provide a narrative review of the most recent data concerning the involvement of the microbiome in the pathogenesis of connective tissue diseases (CTDs) and vasculitides.

Methods

The PubMed database was searched for articles using combinations of words or terms that included systemic lupus erythematosus, systemic sclerosis, autoimmune myositis, Sjögren's syndrome, undifferentiated and mixed CTD, vasculitis, microbiota, microbiome, and dysbiosis. Papers from the reference lists of the articles and book chapters were reviewed, and relevant publications were identified. Abstracts and articles written in languages other than English were excluded.

Results

We found some evidence that dysbiosis participates in the pathogenesis of systemic lupus erythematosus, systemic sclerosis, Sjögren's syndrome, and Behçet's disease, but there are still few data concerning the role of dysbiosis in other CTDs or vasculitides.

Conclusions

Numerous studies suggest that alterations in human microbiota may be involved in the pathogenesis of inflammatory arthritides as a result of the aberrant activation of the innate and adaptive immune responses. Only a few studies have explored the involvement of dysbiosis in other CTDs or vasculitides, and further research is needed.

Identification of Optimal Mouse Models of Systemic Sclerosis by Interspecies Comparative Genomics

OBJECTIVE

Understanding the pathogenesis of systemic sclerosis (SSc) is confounded by considerable disease heterogeneity. Animal models of SSc that recapitulate distinct subsets of disease at the molecular level have not been delineated. We applied interspecies comparative analysis of genomic data from multiple mouse models of SSc and patients with SSc to determine which animal models best reflect the SSc intrinsic molecular subsets.

METHODS

Gene expression measured in skin from mice with sclerodermatous graft-versus-host disease (GVHD), bleomycin-induced fibrosis, Tsk1/+ or Tsk2/+ mice was mapped to human orthologs and compared to SSc skin biopsy-derived gene expression. Transforming growth factor β (TGFβ) activation was assessed using a responsive signature in mice, and tumor necrosis factor receptor superfamily member 12A (TNFRSF12A) expression was measured in SSc patient and mouse skin.

RESULTS

Gene expression in skin from mice with sclerodermatous GVHD and bleomycin-induced fibrosis corresponded to that in SSc patients in the inflammatory molecular subset. In contrast, Tsk2/+ mice showed gene expression corresponding to the fibroproliferative SSc subset. Enrichment of a TGFβ-responsive signature was observed in both Tsk2/+ mice and mice with bleomycin-induced skin fibrosis. Expression of TNFRSF12A (the TWEAK receptor/fibroblast growth factor-inducible 14) was elevated in skin from patients with fibroproliferative SSc and the skin of Tsk2/+ mice.

CONCLUSION

This study reveals similarities in cutaneous gene expression between distinct mouse models of SSc and specific molecular subsets of the disease. Different pathways underlie the intrinsic subsets including TGFβ, interleukin-13 (IL-13), and IL-4. We identify a novel target, Tnfrsf12a, with elevated expression in skin from patients with fibroproliferative SSc and Tsk2/+ mice. These findings will inform mechanistic and translational preclinical studies in SSc.

Animal models of scleroderma: recent progress

PURPOSE OF REVIEW

We discuss recent advances in evaluating and optimizing animal models of systemic sclerosis (SSc). Such models could be of value for illuminating etiopathogenesis using hypothesis-testing experimental approaches, for developing effective disease-modifying therapies, and for uncovering clinically relevant biomarkers.

RECENT FINDINGS

We describe recent advances in previously reported and novel animal models of SSc. The limitations of each animal model and their ability to recapitulate the pathophysiology of recognized molecular subsets of SSc are discussed. We highlight attrition of dermal white adipose tissue as a consistent pathological feature of dermal fibrosis in mouse models, and its relevance to SSc-associated cutaneous fibrosis.

SUMMARY

Several animal models potentially useful for studying SSc pathogenesis have been described. Recent studies highlight particular strengths and weaknesses of selected models in recapitulating distinct features of the human disease. When used in the appropriate experimental setting, and in combination, these models singly and together provide a powerful set of in-vivo tools to define underlying mechanisms of disease and to develop and evaluate effective antifibrotic therapies.

A novel multi-network approach reveals tissue-specific cellular modulators of fibrosis in systemic sclerosis

Background

Systemic sclerosis (SSc) is a multi-organ autoimmune disease characterized by skin fibrosis. Internal organ involvement is heterogeneous. It is unknown whether disease mechanisms are common across all involved affected tissues or if each manifestation has a distinct underlying pathology.

Methods

We used consensus clustering to compare gene expression profiles of biopsies from four SSc-affected tissues (skin, lung, esophagus, and peripheral blood) from patients with SSc, and the related conditions pulmonary fibrosis (PF) and pulmonary arterial hypertension, and derived a consensus disease-associate signature across all tissues. We used this signature to query tissue-specific functional genomic networks. We performed novel network analyses to contrast the skin and lung microenvironments and to assess the functional role of the inflammatory and fibrotic genes in each organ. Lastly, we tested the expression of macrophage activation state-associated gene sets for enrichment in skin and lung using a Wilcoxon rank sum test.

Results

We identified a common pathogenic gene expression signature—an immune–fibrotic axis—indicative of pro-fibrotic macrophages (MØs) in multiple tissues (skin, lung, esophagus, and peripheral blood mononuclear cells) affected by SSc. While the co-expression of these genes is common to all tissues, the functional consequences of this upregulation differ by organ. We used this disease-associated signature to query tissue-specific functional genomic networks to identify common and tissue-specific pathologies of SSc and related conditions. In contrast to skin, in the lung-specific functional network we identify a distinct lung-resident MØ signature associated with lipid stimulation and alternative activation. In keeping with our network results, we find distinct MØ alternative activation transcriptional programs in SSc-associated PF lung and in the skin of patients with an “inflammatory” SSc gene expression signature.

Conclusions

Our results suggest that the innate immune system is central to SSc disease processes but that subtle distinctions exist between tissues. Our approach provides a framework for examining molecular signatures of disease in fibrosis and autoimmune diseases and for leveraging publicly available data to understand common and tissue-specific disease processes in complex human diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-017-0417-1) contains supplementary material, which is available to authorized users.

Inhibition of phosphodiesterase 4 (PDE4) reduces dermal fibrosis by interfering with the release of interleukin-6 from M2 macrophages

OBJECTIVES

To investigate the disease-modifying effects of phosphodiesterase 4 (PDE4) inhibition in preclinical models of systemic sclerosis (SSc).

METHODS

We studied the effects of PDE4 inhibition in a prevention and a treatment model of bleomycin-induced skin fibrosis, in the topoisomerase mouse model as well as in a model of sclerodermatous chronic graft-versus-host disease. To better understand the mode of action of PDE4 blockade in preclinical models of SSc, we investigated fibrosis-relevant mediators in fibroblasts and macrophages from healthy individuals and patients suffering from diffuse-cutaneous SSc on blockade of PDE4.

RESULTS

Specific inhibition of PDE4 by rolipram and apremilast had potent antifibrotic effects in bleomycin-induced skin fibrosis models, in the topoisomerase I mouse model and in murine sclerodermatous chronic graft-versus-host disease. Fibroblasts were not the direct targets of the antifibrotic effects of PDE4 blockade. Reduced leucocyte infiltration in lesional skin on PDE4 blockade suggested an immune-mediated mechanism. Further analysis revealed that PDE4 inhibition decreased the differentiation of M2 macrophages and the release of several profibrotic cytokines, resulting in reduced fibroblast activation and collagen release. Within these profibrotic mediators, interleukin-6 appeared to play a central role.

CONCLUSIONS

PDE4 inhibition reduces inflammatory cell activity and the release of profibrotic cytokines from M2 macrophages, leading to decreased fibroblast activation and collagen release. Importantly, apremilast is already approved for the treatment of psoriasis and psoriatic arthritis. Therefore, PDE4 inhibitors might be further developed as potential antifibrotic therapies for patients with SSc. Our findings suggest that particularly patients with inflammation-driven fibrosis might benefit from PDE4 blockade.

Molecular stratification and precision medicine in systemic sclerosis from genomic and proteomic data

PURPOSE OF REVIEW

The goal of this review is to summarize recent advances into the pathogenesis and treatment of systemic sclerosis (SSc) from genomic and proteomic studies.

RECENT FINDINGS

Intrinsic gene expression-driven molecular subtypes of SSc are reproducible across three independent datasets. These subsets are a consistent feature of SSc and are found in multiple end-target tissues, such as skin and esophagus. Intrinsic subsets as well as baseline levels of molecular target pathways are potentially predictive of clinical response to specific therapeutics, based on three recent clinical trials. A gene expression-based biomarker of modified Rodnan skin score, a measure of SSc skin severity, can be used as a surrogate outcome metric and has been validated in a recent trial. Proteome analyses have identified novel biomarkers of SSc that correlate with SSc clinical phenotypes.

SUMMARY

Integrating intrinsic gene expression subset data, baseline molecular pathway information, and serum biomarkers along with surrogate measures of modified Rodnan skin score provides molecular context in SSc clinical trials. With validation, these approaches could be used to match patients with the therapies from which they are most likely to benefit and thus increase the likelihood of clinical improvement.

Tenascin-C drives persistence of organ fibrosis

The factors responsible for maintaining persistent organ fibrosis in systemic sclerosis (SSc) are not known but emerging evidence implicates toll-like receptors (TLRs) in the pathogenesis of SSc. Here we show the expression, mechanism of action and pathogenic role of endogenous TLR activators in skin from patients with SSc, skin fibroblasts, and in mouse models of organ fibrosis. Levels of tenascin-C are elevated in SSc skin biopsy samples, and serum and SSc fibroblasts, and in fibrotic skin tissues from mice. Exogenous tenascin-C stimulates collagen gene expression and myofibroblast transformation via TLR4 signalling. Mice lacking tenascin-C show attenuation of skin and lung fibrosis, and accelerated fibrosis resolution. These results identify tenascin-C as an endogenous danger signal that is upregulated in SSc and drives TLR4-dependent fibroblast activation, and by its persistence impedes fibrosis resolution. Disrupting this fibrosis amplification loop might be a viable strategy for the treatment of SSc.