Therapeutic role of interferon-γ in experimental autoimmune encephalomyelitis is mediated through a tolerogenic subset of splenic CD11b+ myeloid cells.

Cumulative evidence has established that Interferon (IFN)-γ has both pathogenic and protective roles in Multiple Sclerosis and the animal model, Experimental Autoimmune Encephalomyelitis (EAE). However, the underlying mechanisms to the beneficial effects of IFN-γ are not well understood. In this study, we found that IFN-γ exerts therapeutic effects on chronic, relapsing-remitting, and chronic progressive EAE models. The frequency of regulatory T (Treg) cells in spinal cords from chronic EAE mice treated with IFN-γ was significantly increased with no effect on Th1 and Th17 cells. Consistently, depletion of FOXP3-expressing cells blocked the protective effects of IFN-γ, indicating that the therapeutic effect of IFN-γ depends on the presence of Treg cells. However, IFN-γ did not trigger direct in vitro differentiation of Treg cells. In vivo administration of blocking antibodies against either interleukin (IL)-10, transforming growth factor (TGF)-ß or program death (PD)-1, revealed that the protective effects of IFN-γ in EAE were also dependent on TGF-ß and PD-1, but not on IL-10, suggesting that IFN-γ might have an indirect role on Treg cells acting through antigen-presenting cells. Indeed, IFN-γ treatment increased the frequency of a subset of splenic CD11b+ myeloid cells expressing TGF-ß-Latency Associated Peptide (LAP) and program death ligand 1 (PD-L1) in a signal transducer and activator of transcription (STAT)-1-dependent manner. Furthermore, splenic CD11b+ cells from EAE mice preconditioned in vitro with IFN-γ and myelin oligodendrocyte glycoprotein (MOG) peptide exhibited a tolerogenic phenotype with the capability to induce conversion of naïve CD4+ T cells mediated by secretion of TGF-ß. Remarkably, adoptive transfer of splenic CD11b+ cells from IFN-γ-treated EAE mice into untreated recipient mice ameliorated clinical symptoms of EAE and limited central nervous system infiltration of mononuclear cells and effector helper T cells. These results reveal a novel cellular and molecular mechanism whereby IFN-γ promotes beneficial effects in EAE by endowing splenic CD11b+ myeloid cells with tolerogenic and therapeutic activities.

Performance of the 2019 American College of Rheumatology/European League Against Rheumatism Classification Criteria for IgG4-Related Disease in a Latin American Cohort.

BACKGROUND/OBJECTIVE: The 2019 American College of Rheumatology/European League Against Rheumatism Classification Criteria (2019 AECC) for IgG4-related disease (IgG4-RD) is considered a significant advancement in the study of this condition. Most studies evaluating their performance have focused on White and Asian patients, leaving a knowledge gap regarding Latin American populations. Therefore, this study aimed to assess the performance of the 2019 AECC for IgG4-RD in a cohort of Latin American patients. METHODS: A multicenter medical records review study was conducted, involving centers from Argentina, Chile, Mexico, Peru, and Uruguay. Data on IgG4-RD patients and mimicker conditions were collected through a standardized online form. The criterion standard for diagnosing IgG4-RD was based on the fulfillment of the Comprehensive Diagnostic Criteria for IgG4-RD and/or the Consensus Statement on Pathology. The 2019 AECC was retrospectively applied. RESULTS: We included 300 patients, with 180 (60%) having IgG4-RD and 120 (40%) having mimicker conditions. The 2019 AECC had a sensitivity of 66.7% and a specificity of 100%. Sensitivity increased to 73.3% when disease-specific autoantibody items were removed, without affecting specificity. The true-positive cases had more involved organs, a higher availability of biopsy results, and were more likely to belong to the Mikulicz/systemic and proliferative phenotypes. CONCLUSIONS: The use of the 2019 AECC for IgG4-RD in a Latin American population confirms its high specificity in excluding those without the disease. The presence of concomitant autoimmune diseases and clinically nonsignificant disease-specific autoantibodies excludes a significant number of patients from fulfilling the criteria.

Interferon-gamma ameliorates experimental autoimmune encephalomyelitis by inducing homeostatic adaptation of microglia.

Compelling evidence has shown that interferon (IFN)-γ has dual effects in multiple sclerosis and in its animal model of experimental autoimmune encephalomyelitis (EAE), with results supporting both a pathogenic and beneficial function. However, the mechanisms whereby IFN-γ may promote neuroprotection in EAE and its effects on central nervous system (CNS)-resident cells have remained an enigma for more than 30 years. In this study, the impact of IFN-γ at the peak of EAE, its effects on CNS infiltrating myeloid cells (MC) and microglia (MG), and the underlying cellular and molecular mechanisms were investigated. IFN-γ administration resulted in disease amelioration and attenuation of neuroinflammation associated with significantly lower frequencies of CNS CD11b+ myeloid cells and less infiltration of inflammatory cells and demyelination. A significant reduction in activated MG and enhanced resting MG was determined by flow cytometry and immunohistrochemistry. Primary MC/MG cultures obtained from the spinal cord of IFN-γ-treated EAE mice that were ex vivo re-stimulated with a low dose (1 ng/ml) of IFN-γ and neuroantigen, promoted a significantly higher induction of CD4+ regulatory T (Treg) cells associated with increased transforming growth factor (TGF)-ß secretion. Additionally, IFN-γ-treated primary MC/MG cultures produced significantly lower nitrite in response to LPS challenge than control MC/MG. IFN-γ-treated EAE mice had a significantly higher frequency of CX3CR1high MC/MG and expressed lower levels of program death ligand 1 (PD-L1) than PBS-treated mice. Most CX3CR1highPD-L1lowCD11b+Ly6G- cells expressed MG markers (Tmem119, Sall2, and P2ry12), indicating that they represented an enriched MG subset (CX3CR1highPD-L1low MG). Amelioration of clinical symptoms and induction of CX3CR1highPD-L1low MG by IFN-γ were dependent on STAT-1. RNA-seq analyses revealed that in vivo treatment with IFN-γ promoted the induction of homeostatic CX3CR1highPD-L1low MG, upregulating the expression of genes associated with tolerogenic and anti-inflammatory roles and down-regulating pro-inflammatory genes. These analyses highlight the master role that IFN-γ plays in regulating microglial activity and provide new insights into the cellular and molecular mechanisms involved in the therapeutic activity of IFN-γ in EAE.

Addressing health disparities as a function of ethnicity in systemic lupus erythematosus patients.

Systemic lupus erythematosus (SLE) is an autoimmune disorder with significant health disparities, as it disproportionately and more severely affects vulnerable and disadvantaged population groups in the United States and around the world, that is, women, ethnic minorities, individuals living in poverty, less educated, and lacking medical insurance. Both, genetic and non-genetic factors, contribute to these disparities. To overcome these health disparities and reduce poor outcomes among disadvantaged SLE populations, interventions on non-genetic amendable factors, especially on social health determinants, are necessary.

Reduced Immune Response to Inactivated Severe Acute Respiratory Syndrome Coronavirus 2 Vaccine in a Cohort of Immunocompromised Patients in Chile.

BACKGROUND: Inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines have been widely implemented in low- and middle-income countries. However, immunogenicity in immunocompromised patients has not been established. Herein, we aimed to evaluate immune response to CoronaVac vaccine in these patients. METHODS: This prospective cohort study included 193 participants with 5 different immunocompromising conditions and 67 controls, receiving 2 doses of CoronaVac 8-12 weeks before enrollment. The study was conducted between May and August 2021, at Red de Salud UC-CHRISTUS, Santiago, Chile. Neutralizing antibody (NAb) positivity, total anti-SARS-CoV-2 immunoglobulin G antibody (TAb) concentrations, and T-cell responses were determined. RESULTS: NAb positivity and median neutralizing activity were 83.1% and 51.2% for the control group versus 20.6% and 5.7% (both P < .001) in the solid organ transplant group, 41.5% and 19.2% (both P < .0001) in the autoimmune rheumatic diseases group, 43.3% (P < .001) and 21.4% (P<.01 or P = .001) in the cancer with solid tumors group, 45.5% and 28.7% (both P < .001) in the human immunodeficiency virus (HIV) infection group, 64.3% and 56.6% (both differences not significant) in the hematopoietic stem cell transplant group, respectively. TAb seropositivity was also lower for the solid organ transplant (20.6%; P < .0001), rheumatic diseases (61%; P < .001), and HIV groups (70.9%; P = .003), compared with the control group (92.3%). On the other hand, the number of interferon γ spot-forming T cells specific for SARS-CoV-2 tended to be lower in all immunocompromising conditions but did not differ significantly between groups. CONCLUSIONS: Diverse immunocompromising conditions markedly reduce the humoral response to CoronaVac vaccine. These findings suggest that a boosting vaccination strategy should be considered in these vulnerable patients. CLINICAL TRIALS REGISTRATION: NCT04888793.

Impact of COVID-19 pandemic on patients with rheumatic diseases in Latin America.

The objective of our study was to describe knowledge, attitudes and practices of Latin-American rheumatology patients regarding management and follow-up of their disease during COVID-19 pandemic. A cross-sectional observational study was conducted using a digital anonymous survey. Rheumatic patients ≥ 18 years from non-English-speaking PANLAR countries were included. Our survey included 3502 rheumatic patients living in more than 19 Latin-American countries. Median age of patients was 45.8(36-55) years and the majority (88.9%) was female. Most frequently self-reported disease was rheumatoid arthritis (48.4%). At least one anti-rheumatic treatment was suspended by 23.4% of patients. Fear of contracting SARS-Cov2 (27.7%) and economic issues (25%) were the most common reasons for drug discontinuation. Self-rated disease activity increased from 30 (7-50) to 45 (10-70) points during the pandemic. Communication with their rheumatologist during the pandemic was required by 55.6% of patients, mainly by telephone calls (50.2%) and social network messages (47.8%). An adequate knowledge about COVID-19 was observed in 43% of patients. Patients with rheumatic diseases in Latin America were negatively affected by the COVID-19 pandemic. An increase in self-rated disease activity, a reduction in medication adherence, and hurdles for medical follow-up were reported. Teleconsultation was perceived as a valid alternative to in-person visits during the pandemic.

Cellular and molecular regulation of the programmed death-1/programmed death ligand system and its role in multiple sclerosis and other autoimmune diseases.

Programmed Cell Death 1 (PD-1) receptor and its ligands (PD-Ls) are essential to maintain peripheral immune tolerance and to avoid tissue damage. Consequently, altered gene or protein expression of this system of co-inhibitory molecules has been involved in the development of cancer and autoimmunity. Substantial progress has been achieved in the study of the PD-1/PD-Ls system in terms of regulatory mechanisms and therapy. However, the role of the PD-1/PD-Ls pathway in neuroinflammation has been less explored despite being a potential target of treatment for neurodegenerative diseases. Multiple Sclerosis (MS) is the most prevalent, chronic, inflammatory, and autoimmune disease of the central nervous system that leads to demyelination and axonal damage in young adults. Recent studies have highlighted the key role of the PD-1/PD-Ls pathway in inducing a neuroprotective response and restraining T cell activation and neurodegeneration in MS. In this review, we outline the molecular and cellular mechanisms regulating gene expression, protein synthesis and traffic of PD-1/PD-Ls as well as relevant processes that control PD-1/PD-Ls engagement in the immunological synapse between antigen-presenting cells and T cells. Also, we highlight the most recent findings regarding the role of the PD-1/PD-Ls pathway in MS and its murine model, experimental autoimmune encephalomyelitis (EAE), including the contribution of PD-1 expressing follicular helper T (TFH) cells in the pathogenesis of these diseases. In addition, we compare and contrast results found in MS and EAE with evidence reported in other autoimmune diseases and their experimental models, and review PD-1/PD-Ls-targeting therapeutic approaches.

Current status of the rheumatologists' workforce in Latin America: a PANLAR collaborative study.

INTRODUCTION: Studies conducted by various scientific societies have shown that the demand for specialized rheumatology care is greater than the projected growth of the workforce. Our research aims to assess the current status of the rheumatology workforce in Latin America. METHOD: This is a descriptive, cross-sectional study. A survey was created on the RedCap platform. Data were analyzed with STATA 15® Software. We present descriptive analyses. The rate of inhabitants per rheumatologist was calculated using the number of rheumatologists practicing in each country and the inhabitants for year 2020. RESULTS: Our sample was composed by 19 PANLAR member countries in Latin America. Latin America has one rheumatologist per 106,838 inhabitants. The highest rate of rheumatologist per inhabitants was found in Uruguay (1 per 27,426 inhabitants), and the lowest was found in Nicaragua (1 per 640,648 inhabitants). Mean age was 51.59 (SD12.70), ranging between 28 and 96 years of age. Mean monthly compensation was USD $2382.6 (SD$1462.5). The country with lowest salary was Venezuela ($197), whereas the highest was Costa Rica ($4500). CONCLUSIONS: There is a high variability in rheumatologists' workforce characteristics in Latin America. These results could lead to policies aiming to increase the availability and income of rheumatologists, in order to increase opportunity and quality of care of patients living with rheumatic diseases. Key Points • The rheumatologists' workforce varies significantly among Latin American countries. • The supply of rheumatologists is insufficient for meeting the increasing need for specialists in this field.

Manifestaciones clínicas y anticuerpos asociados y específicos de miositis en 15 pacientes chilenos con dermatomiositis: serie clínica en un centro universitario / Clinical manifestations and antibody profile in 15 patients with dermatomyositis

Background: Certain associated and specific myositis antibodies are related to certain clinical phenotypes of dermatomyositis (DM), disease severity and the presence of cancer. Aim: To describe the clinical profile of Chilean patients with DM and their associated and specific myositis antibodies. Material and Methods: Review of medical records of 15 patients with DM aged 31 to 72 years. Their clinical characteristics, laboratory tests and complementary tests were reviewed. In serum samples from each patient the presence of 16 specific antibodies was analyzed by immunoblot technique (Myositis Profile Euroline Blot test kit). Results: Fourteen (93.3%) patients had skin manifestations, five (33.3%) had pulmonary involvement, two (13.3%) had an associated cancer and nine (60%) had specific antibodies associated with myositis. Conclusions: These patients with DM had a clinical profile similar to what has been described elsewhere. The profile of myositis specific antibodies was different from reports in other populations.

The Prevalence of Rheumatoid Arthritis in Chile: A Nationwide Study Performed as Part of the National Health Survey.

OBJECTIVE: Genetic and environmental backgrounds influence the development of rheumatoid arthritis (RA). In Latin America, epidemiologic data are scarce. We aimed to determine the prevalence of RA in Chile in a population-based study. METHODS: The National Health Survey was a cross-sectional household survey with a stratified multistage probability sample of 6233 participants performed between August 2016 and March 2017. A screening instrument for RA was applied to a random sample of 3847 subjects > 30 years old. Positive screening was defined by at least 1 of the following: 2 swollen joints for at least 4 consecutive weeks (past/present), and/or a diagnosis of arthritis in the past. Individuals with positive screening had rheumatoid factor, anticitrullinated protein antibodies, and C-reactive protein measured, as well as clinical examination performed by a rheumatologist. Self-report of doctor-diagnosed RA was also performed. RESULTS: The screening questionnaire was applied to 2998 subjects. A positive screening was found for 783 (22.1%). Among subjects with positive screening, 493 (66%) had a clinical evaluation performed by a rheumatologist. Using the American College of Rheumatology/European League Against Rheumatism 2010 classification criteria, prevalence was 0.6% (95% CI 0.3-1.2). Prevalence was higher in women, and 3.3% of subjects self-reported having RA. CONCLUSION: According to this national population-based study, RA prevalence in Chile is 0.6% (0.3-1.2), a value similar to what has been found in developed countries and slightly lower than some Latin American countries. Self-reporting leads to overestimating RA.

Understanding the Cryoglobulinemias.

PURPOSE OF THE REVIEW: Cryoglobulins are immunoglobulins with the ability to precipitate at temperatures <37 °C. They are related to hematological disorders, infections [especially hepatitis C virus (HCV)], and autoimmune diseases. In this article, the state of the art on Cryoglobulinemic Vasculitis (CV), in a helpful and schematic way, with a special focus on HCV related Mixed Cryoglobulinemia treatment are reviewed. RECENT FINDINGS: Direct - acting antivirals (DAA) against HCV have emerged as an important key in HCV treatment to related Cryoglobulinemic Vasculitis, and should be kept in mind as the initial treatment in non-severe manifestations. On the other hand, a recent consensus panel has published their recommendations for treatment in severe and life threatening manifestations of Mixed Cryoglobulinemias. HCV-Cryoglobulinemic vasculitis is the most frequent form of CV. There are new treatment options in HCV-CV with DAA, with an important number of patients achieving complete response and sustained virologic response (SVR). In cases of severe forms of CV, treatment with Rituximab and PLEX are options. The lack of data on maintenance therapy could impulse future studies in this setting.

Innate Immune Cells' Contribution to Systemic Lupus Erythematosus.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the presence of autoantibodies against nuclear antigens, immune complex deposition, and tissue damage in the kidneys, skin, heart and lung. Because of the pathogenic role of antinuclear antibodies and autoreactive T cells in SLE, extensive efforts have been made to demonstrate how B cells act as antibody-producing or as antigen-presenting cells that can prime autoreactive T cell activation. With the discovery of new innate immune cells and inflammatory mediators, innate immunity is emerging as a key player in disease pathologies. Recent work over the last decade has highlighted the importance of innate immune cells and molecules in promoting and potentiating SLE. In this review, we discuss recent evidence of the involvement of different innate immune cells and pathways in the pathogenesis of SLE. We also discuss new therapeutics targets directed against innate immune components as potential novel therapies in SLE.

Smoking promotes exacerbated inflammatory features in dendritic cells of Chilean rheumatoid arthritis patients.

BACKGROUND: The dual potential to promote tolerance or inflammation when facing self-antigens makes dendritic cells (DCs) fundamental players in autoimmunity. There is an association between smoking and DCs maturation in patients with rheumatoid arthritis (RA). However, ethnicity is a key factor in autoimmune disorders. AIM: To evaluate phenotypic and functional alterations of DCs obtained from Chilean patients with RA as compared to healthy controls (HC). In second term, to compare the inflammatory behaviour of DCs between smoker and non-smoker patients. MATERIAL AND METHODS: Monocyte-derived DCs and T-cells were obtained from blood samples isolated from 30 HC and 32 RA-patients, 14 of which were currently smokers and 18 non-smokers. Several maturation surface markers were evaluated in DCs, including HLA-DR, CD40, CD80, CD83 and CD86. Furthermore, autologous co-cultures of DCs and T-cells were carried out and then T-cell proliferation, and expansion of Th1, Th17 and Tregs were analysed. RESULTS: Compared with HC, RA-patients displayed increased HLA-DR expression in DCs, which was manifested mainly in patients with moderate-to- high disease activity scores (DAS28). Furthermore, RA-patients presented a stronger Th17-expansion and a correlation between DAS28 and Th1-expansion. Both effects were mainly observed in patients in remission or with a low DAS28. Moreover, smoker RA-patients displayed enhanced HLA-DR and CD83 expression in DCs as well as an exacerbated Th17-expansion and a correlation between DAS28 and Th1-expansion. CONCLUSIONS: These findings suggest that smoking enhances the inflammatory behaviour of DCs and the consequent Th1 and Th17-mediated response in patients with RA.

Smoking promotes exacerbated inflammatory features in dendritic cells of Chilean rheumatoid arthritis patients / El tabaco exacerba características inflamatorias en células dendríticas de pacientes chilenos con artritis reumatoide

ABSTRACT Background: The dual potential to promote tolerance or inflammation when facing self-antigens makes dendritic cells (DCs) fundamental players in autoimmunity. There is an association between smoking and DCs maturation in patients with rheumatoid arthritis (RA). However, ethnicity is a key factor in autoimmune disorders. Aim: To evaluate phenotypic and functional alterations of DCs obtained from Chilean patients with RA as compared to healthy controls (HC). In second term, to compare the inflammatory behaviour of DCs between smoker and non-smoker patients. Material and Methods: Monocyte-derived DCs and T-cells were obtained from blood samples isolated from 30 HC and 32 RA-patients, 14 of which were currently smokers and 18 non-smokers. Several maturation surface markers were evaluated in DCs, including HLA-DR, CD40, CD80, CD83 and CD86. Furthermore, autologous co-cultures of DCs and T-cells were carried out and then T-cell proliferation, and expansion of Th1, Th17 and Tregs were analysed. Results: Compared with HC, RA-patients displayed increased HLA-DR expression in DCs, which was manifested mainly in patients with moderate-to- high disease activity scores (DAS28). Furthermore, RA-patients presented a stronger Th17-expansion and a correlation between DAS28 and Th1-expansion. Both effects were mainly observed in patients in remission or with a low DAS28. Moreover, smoker RA-patients displayed enhanced HLA-DR and CD83 expression in DCs as well as an exacerbated Th17-expansion and a correlation between DAS28 and Th1-expansion. Conclusions: These findings suggest that smoking enhances the inflammatory behaviour of DCs and the consequent Th1 and Th17-mediated response in patients with RA

Introducción: El potencial dual que poseen para promover tolerancia o inflamación ante antígenos propios, hace de las células dendríticas (CDs) actores fundamentales en el desarrollo de autoinmunidad. Existe una asociación entre fumar y la maduración de las CDs en pacientes con artritis reumatoide (AR). No obstante, la etnicidad es un factor clave a considerar en desórdenes autoinmunes. Objetivos: Comparar las alteraciones fenotípicas y funcionales de las CDs obtenidas desde pacientes Chilenos con AR y controles sanos (CS). Además, analizamos las diferencias en el comportamiento inflamatorio que existe entre las CDs obtenidas de pacientes fumadores y CS. Materiales y Métodos: Se obtuvieron CDs derivadas de monocitos y células T desde muestras de sangre aisladas de 30 CS y 32 pacientes con AR, 14 de los cuales eran fumadores y 18 no fumadores. Se evaluaron marcadores de maduración en la superficie de las CDs: HLA-DR, CD40, CD80, CD83 y CD86. Además, se realizaron co-cultivos autólogos de células T y CDs, analizando la proliferación de células T, y la expansión de células Th1, Th17 y Tregs. Resultados: En comparación con los CS, los pacientes AR mostraron un aumento de la expresión de HLA-DR en las CDs, principalmente en los individuos con DAS28 moderado-alto. Los pacientes con AR presentaron una mayor expansión de células Th17 y una correlación entre el DAS28 y la expansión de células Th1, ambos efectos manifestados principalmente en los individuos con un DAS28 bajo o en remisión. Además, los pacientes con AR fumadores mostraron un aumento en la expresión de HLA-DR y CD83 en las CDs y una expansión de células Th17 exacerbada así como una correlación entre el DAS28 y la expansión de células Th1. Conclusiones: Nuestros resultados sugieren que fumar favorece el comportamiento inflamatorio de las CDs y en consecuencia la inducción de respuestas mediadas por células Th1 y Th17 en los pacientes Chilenos con AR.

Treat to target in systemic lupus erythematosus: a commentary.

Treat to target (T2T) strategies have proved to be useful in several chronic disorders, including Rheumatoid Arthritis. In systemic lupus erythematosus (SLE), T2T strategy has been proposed in order to control disease activity, improve health-related quality of life, and reduce morbidity and mortality. Remission would be the main target, but a low disease activity state (LDAS) could be an acceptable alternative. However, due to SLE protean manifestations, the operational definitions of both remission and LDAS are still in progress. The definitions of these targets, remission and LDAS, should include a validated disease activity index, the treatments allowed, and the minimum length of time the target should be maintained. Furthermore, achieving these targets should result in better disease outcomes such as reducing damage accrual. This review addresses the current state regarding these possible targets in SLE and the impact of achieving them in intermediate and long-term outcomes of this disease.

Inhibition of angiogenesis by platelets in systemic sclerosis patients.

INTRODUCTION: Systemic sclerosis (SSc) is a chronic autoimmune disease characterized by microvascular damage, inflammation, and fibrosis. It has become increasingly evident that platelets, beyond regulating hemostasis, are important in inflammation and innate immunity. Platelets may be an important source of proinflammatory and profibrotic cytokines in the vascular microenvironment. In this study, we sought to assess the contribution of platelet-derived factors in patients with SSc to the angiogenesis of human dermal microvascular endothelial cells (DMVECs) in a tubule formation assay and to characterize the secretion of profibrotic and proinflammatory cytokines in these platelets. METHODS: We analyzed platelets obtained from 30 patients with SSc and 12 healthy control subjects. Angiogenesis was evaluated in vitro with a DMVEC tubule formation assay on Matrigel and platelet-derived angiogenic factors such as vascular endothelial growth factor (VEGF), 165b isoform (VEGF165b), and cytokine secretion was evaluated. Platelet serotonin content was also determined. RESULTS: When DMVECs were incubated with SSc platelet releasates, tubule formation was significantly inhibited (p < 0.01, t test), and higher expression of endothelin-1 in these cells was observed compared with control subjects (p < 0.05, Mann-Whitney U test). In SSc platelet releasates, VEGF165b was significantly higher (p < 0.05, t test), and the VEGF165b/VEGF ratio was increased compared with that of control subjects. Higher secretion of transforming growth factor ß (p < 0.01, t test) and CD40L (p < 0.01, t test) was observed compared with control subjects. Also, intraplatelet serotonin levels were lower in platelets obtained from patients with diffuse SSc compared with patients with limited SSc and control subjects (p < 0.05, t test). CONCLUSIONS: Our findings suggest that antiangiogenic factors such as VEGF165b, together with proinflammatory and profibrotic factors secreted by platelets, can contribute to the progression of peripheral microvascular damage, defective vascular repair, and fibrosis in patients with SSc.