Deficiency and altered phenotype of mucosal-associated invariant T cells in systemic sclerosis.

Objective: Systemic sclerosis is an autoimmune disease characterized by fibrosis of the skin and internal organs including the lung. Mucosal-associated invariant T cells are innate-like T lymphocytes able to produce various cytokines and cytotoxic mediators such as granzyme B. A large body of evidence supports a role of mucosal-associated invariant T cells in autoimmune disease but more recent reports suggest also a potential role in fibrotic conditions. Therefore, we herein addressed the question as whether mucosal-associated invariant T cells may have an altered profile in systemic sclerosis. Methods: Mucosal-associated invariant T cell frequency was analyzed by flow cytometry, using fresh peripheral blood from 74 consecutive systemic sclerosis patients who were compared to 44 healthy donors. In addition, in-depth mucosal-associated invariant T cell phenotype and function were analyzed in unselected 29 women with systemic sclerosis who were compared to 23 healthy women donors. Results: Proportion of circulating mucosal-associated invariant T cells was significantly reduced by 68% in systemic sclerosis compared to healthy donors (0.78% in systemic sclerosis vs 2.5%, p < 0.0001). Within systemic sclerosis subsets, mucosal-associated invariant T cells were reduced in patients with interstitial lung disease (systemic sclerosis-interstitial lung disease) (0.56% vs 0.96% in patients without interstitial lung disease, p = 0.04). Moreover, in systemic sclerosis patients, mucosal-associated invariant T cells displayed an activated phenotype indicated by markedly increased CD69+ mucosal-associated invariant T cell frequency (20% mucosal-associated invariant T cell CD69+ compared to 9.4% in healthy donors, p = 0.0014). Interestingly, mucosal-associated invariant T cells from systemic sclerosis-interstitial lung disease patients had a more pronounced altered phenotype compared to systemic sclerosis without interstitial lung disease with a correlation between mucosal-associated invariant T cells expressing CCR6+ and mucosal-associated invariant T cell frequency (r = 0.8, p = 0.006). Conclusion: Circulating mucosal-associated invariant T cells were reduced and exhibited an activated phenotype in systemic sclerosis patients. This peripheral mucosal-associated invariant T cell deficiency may be related to enhanced apoptosis and/or homing in inflamed tissue, particularly in systemic sclerosis-interstitial lung disease patients.

Risk stratification using anti-citrullinated peptide antibodies (ACPA) in polyarticular subtypes of juvenile idiopathic arthritis in adulthood.

OBJECTIVES: Polyarticular juvenile idiopathic arthritis (pJIA) is a subset of juvenile idiopathic arthritis (JIA), divided into two subtypes according to the presence of rheumatoid factor: pJIA without rheumatoid factor (pJIA RF-) and pJIA with positive rheumatoid factor (pJIA RF+), this latter is characterised with more structural damage. Anti-citrullinated peptide antibodies (ACPA) are often associated with RF. The respective performance of ACPA versus RF in structural outcome in pJIA, and in particular in adulthood pJIA remains unknown. Therefore, the aim of this study was to determine whether ACPA could be of value to assess structural damage in pJIA persisting in adulthood. METHODS: Patients with pJIA and available data for ACPA, RF and X-ray were included retrospectively. Structural damage was assessed by two independent blinded investigators using Sharp Van Der Heijde scores. RESULTS: 56 pJIA adult patients were included: 62% (35/56) had pJIA RF+ and 38% (21/56) pJIA RF-. ACPA positivity in pJIA was significantly associated with presence of RF (96% vs 26%, P<0.001). RF positivity was significantly associated with higher Sharp van Der Heijde erosion and total scores (respectively P<0.01 and P<0.05). There were higher Sharp Van Der Heijde erosion, joint space narrowing and total scores in the pJIA ACPA+ subgroup than in the pJIA ACPA- subgroup, although there was no statistical significance. However, when adjusted on disease duration, pJIA ACPA+ patients had significantly higher erosion and total scores than pJIA ACPA- patients (P<0.05), and pJIA ACPA+ patients required more bDMARDs than pJIA ACPA- patients (P<0.05). Moreover, pJIA patients with high Sharp van Der Heijde joint space narrowing and total scores had significantly higher ACPA levels (P<0.01). A correlation was identified between ACPA levels and Sharp van Der Heijde total score (r=0.54, P<0.05). In the pJIA RF+ subgroup the presence of ACPA was associated with additional structural damage compared to no ACPA: sharp Van Der Heijde erosion, joint space narrowing and total scores were higher in the pJIA RF+ ACPA+ subgroup than in the pJIA RF+ ACPA- subgroup although these results did not reach significance. CONCLUSION: Our results suggest that pJIA RF+ ACPA+ adult patients may have a more severe articular phenotype than pJIA RF+ ACPA- patients. ACPA could bring an additional value to RF for pJIA patients regarding structural damage. Altogether our results show that RF and ACPA are associated with structural damage measured by Sharp Van Der Heijde score in pJIA persisting in adulthood.

Evaluation of Patients With Rheumatoid Arthritis in Teleconsultation During the First Wave of the COVID-19 Pandemic.

OBJECTIVE: To describe which variables were collected by rheumatologists to monitor patients with rheumatoid arthritis (RA) during teleconsultation and identify which ones have more impact on clinician intervention. METHODS: Retrospective monocentric, routine care cross-sectional study including patients with RA seen in teleconsultation between March and September 2020. Available variables assessing disease status were collected in teleconsultation files. Clinician intervention was defined by treatment escalation and/or the need for a rapid face-to-face consultation or day hospitalization. RESULTS: One hundred forty-three patients with RA were included (116 females, mean age of 58 [SD 16] yrs, mean disease duration of 14 [SD 11] yrs). The presence or absence of patient self-reported RA flares was mentioned in all medical files, followed by the presence and/or the number of tender joints (76%), the duration of morning stiffness (66%), the number of pain-related nocturnal awakenings (66%) and the C-reactive protein (CRP) value (54%). Teleconsultation led to a clinician intervention in 22/143 patients (15%), representing 51% of patients with self-reported flares (22/43 patients). Therapeutic escalation was necessary in 13 patients and/or face-to-face consultation or day hospitalization were organized for 10 patients. Multivariate analysis identified RA flares (odds ratio [OR] 15.6, 95% CI 3.37-68.28) and CRP values > 10 mg/L (OR 3.32, 95% CI % 1.12-13.27) as the variables independently associated with clinician intervention. CONCLUSION: Our study identified patient-reported RA flares and increased CRP values as 2 red flags in teleconsultation, independently associated with therapeutic modification and/or the need for a rapid face-to-face consultation. These indicators may help clinicians' decision making in teleconsultation.

Driving Role of Interleukin-2-Related Regulatory CD4+ T Cell Deficiency in the Development of Lung Fibrosis and Vascular Remodeling in a Mouse Model of Systemic Sclerosis.

OBJECTIVE: Systemic sclerosis (SSc) is a debilitating autoimmune disease characterized by severe lung outcomes resulting in reduced life expectancy. Fra-2-transgenic mice offer the opportunity to decipher the relationships between the immune system and lung fibrosis. This study was undertaken to investigate whether the Fra-2-transgenic mouse lung phenotype may result from an imbalance between the effector and regulatory arms in the CD4+ T cell compartment. METHODS: We first used multicolor flow cytometry to extensively characterize homeostasis and the phenotype of peripheral CD4+ T cells from Fra-2-transgenic mice and control mice. We then tested different treatments for their effectiveness in restoring CD4+ Treg cell homeostasis, including adoptive transfer of Treg cells and treatment with low-dose interleukin-2 (IL-2). RESULTS: Fra-2-transgenic mice demonstrated a marked decrease in the proportion and absolute number of peripheral Treg cells that preceded accumulation of activated, T helper cell type 2-polarized, CD4+ T cells. This defect in Treg cell homeostasis was derived from a combination of mechanisms including impaired generation of these cells in both the thymus and the periphery. The impaired ability of peripheral conventional CD4+ T cells to produce IL-2 may greatly contribute to Treg cell deficiency in Fra-2-transgenic mice. Notably, adoptive transfer of Treg cells, low-dose IL-2 therapy, or combination therapy changed the phenotype of Fra-2-transgenic mice, resulting in a significant reduction in pulmonary parenchymal fibrosis and vascular remodeling in the lungs. CONCLUSION: Immunotherapies for restoring Treg cell homeostasis could be relevant in SSc. An intervention based on low-dose IL-2 injections, as is already proposed in other autoimmune diseases, could be the most suitable treatment modality for restoring Treg cell homeostasis for future research.

Risk of liver fibrosis induced by methotrexate and other rheumatoid arthritis medications according to the Fibrosis-4 Index.

OBJECTIVES: We aimed to estimate the amount of scarring in the liver with the fibrosis-4 (FIB-4) index in patients with rheumatoid arthritis (RA) with special interest in methotrexate (MTX) influence. METHODS: This was a cross-sectional monocentric study including successive RA patients recruited for a 12-month period. Data on liver function, disease activity, hepatotoxic and cardiovascular risk factors were systematically collected. The FIB-4 index was calculated according the following formula: (age(years)× AST(U/L)/platelet (PLT) (109/L)×√ALT(U/L)). RESULTS: We included 170 patients with established RA: 141 (83%) were women with a mean age of 59±12 years and mean disease duration of 15±11 years. The FIB-4 was low and not significantly different between patients receiving MTX (n=102), patients previously treated with MTX (n=39) and patients never treated with MTX (n=29). No correlation was observed between FIB-4 values and cumulative MTX dose (r=0.09, p=0.271). No relationship was observed between FIB-4 and MTX treatment duration. The FIB-4 index was found significantly increased in patients receiving leflunomide (n=24), (median (range) 1.58 (0.46-3.16) vs. 1.18 (0.54-3.40), p=0.019) and tocilizumab (n=14), (median (range) 1.82 (0.75-3.73) vs. 1.18 (0.54-3.40), p=0.005) compared to patients not receiving DMARDs (n=29). Multivariate logistic regression analyses revealed an independent association between increased FIB-4 (>1.45) and male gender, low disease activity, and treatment with leflunomide and tocilizumab. CONCLUSIONS: RA patients with long-term maintenance MTX therapy have low FIB-4 values suggesting that MTX is not associated with an increased risk of advanced liver fibrosis. Increased FIB-4 values have been detected in leflunomide- and tocilizumab-treated patients, which will deserve dedicated further investigations.

Systematic assessment of the humoral response against SARS-CoV-2 in a French cohort of 283 patients with rheumatic diseases.

OBJECTIVES: To estimate the seroprevalence of SARS-CoV-2 infection in patients with rheumatic diseases and to specify the proportion of asymptomatic and symptomatic forms of COVID-19. METHODS: We screened for SARS-CoV-2 infection among spondyloarthritis (SpA, n=143) or rheumatoid arthritis (RA, n=140) patients in our outpatient clinic at Cochin Hospital in Paris between June and August 2020. We performed a qualitative SARS-CoV-2 serological test which detects IgG directed against the N nucleocapsid protein (anti-N) and, for some patients, against the Spike protein (anti-S). Descriptive analyses were managed. RESULTS: During June-August 2020, the SARS-CoV-2 seroprevalence rate in our population was 2.83% (8/283 patients) without significant difference between RA and SpA patients (2.14% and 3.5%, respectively). We report 11 out of 283 patients (3.8%) with a diagnosis of SARS-CoV-2 infection. Among these 11 patients, 1 patient was asymptomatic (9%) with a confirmed diagnosis of COVID-19 by anti-S serology. Of the 283 patients, 85% were under bDMARDs, mainly on rituximab (RTX) (n=44) and infliximab (IFX) (n=136). CONCLUSIONS: The seroprevalence of SARS-CoV-2 in patients with rheumatic diseases, mainly under bDMARDs treatments, was 2.83%. Among infected patients, 9% were asymptomatic. Detecting SARS-CoV-2 infections could be based on the strategy using patients' interview and anti-N serology.

Outcomes of limited cutaneous systemic sclerosis patients: Results on more than 12,000 patients from the EUSTAR database.

OBJECTIVES: Limited cutaneous systemic sclerosis (LcSSc) is the most common subset of SSc but it has been overlooked in the past years. At a time at which clinical trials focus on diffuse cutaneous SSc (DcSSc) we aimed at clarifying the outcomes of LcSSc and at evaluating whether potential drug positioned in DcSSc may also be used in LcSSc. METHODS: The EUSTAR database was used to investigate skin, lung and peripheral vasculopathy outcomes in LcSSc. Worsening of skin fibrosis, ILD and peripheral vasculopathy were defined by an increase in modified Rodnan skin score (mRSS) > 3.5 points, a decrease of FVC > 10% in patients with ILD at baseline, and by the development of new digital ulcers (DU) in patients without DU at baseline. RESULTS: 8013 LcSSc and 4786 DcSSc patients were included. In contrast to DcSSc, skin disease was remarkably stable in the majority of LcSSc patients with >80% having a change lower than ±4 units of mRSS at 12, 24 and 36 months follow-up. Conversely, FVC changes over time were very similar between LcSSc and DcSSc. Regarding DU, numbers of patients with new DU over time seemed to be almost similar between the two subsets. CONCLUSIONS: LcSSc patients have a low mRSS at baseline with marginal changes with time. Conversely, SSc-ILD can be as progressive as in DcSSc supporting the inclusion of LcSSc patients in SSc-ILD trials and suggesting potential benefit of any anti-ILD drugs. Similarly, although slightly less common, DU should receive the same attention in the two subsets.

Acute anterior uveitis in spondyloarthritis: a monocentric study of 301 patients.

OBJECTIVES: To assess the cumulative incidence of uveitis in spondyloarthritis (SpA) and its associated factors and to evaluate the effect of DMARD treatment on uveitis in a real-life setting. METHODS: A cross-sectional monocentric observational study (COSPA) was conducted. Patients with definite SpA underwent a face-to-face interview. General data and specific data concerning uveitis were collected. Cumulative incidence of uveitis flares was estimated by Kaplan-Meier survival curves. Factors associated with uveitis were determined by Cox analysis. Treatment effectiveness was evaluated by comparing the number of uveitis flares before/after treatment using Wilcoxon test. RESULTS: In total, 301 patients were included, 186 (61.8%) were men, with mean age and disease duration of 44.8 (±13.6) and 16.8 (±11.9) years, respectively. Among them, 82 (27.2%) had at least one uveitis flare. Prevalence of uveitis at the time of SpA diagnosis was 11.5 % (±1.9%) and increased over time to reach 39.3% (±4.1%) 20 years after diagnosis. HLA B27 positivity and heel pain were independently associated with uveitis (HR [IC 95%] = 4.5 [1.3-15.2] and 1.8 [1.1-2.9], respectively). A significant reduction in the number of uveitis before/after treatment was observed in patients treated with anti TNF monoclonal antibodies (n=27), (1.83 (±4.03) vs. 0.41 (±1.22), p=0.002), whereas it was not with etanercept (n=19), (0.44 (±0.70) and 0.79 (±1.36), p=NS). CONCLUSIONS: Prevalence of uveitis in SpA seems to increase with disease duration and seems more likely to appear with HLA B27 positivity and heel pain. Anti-TNF monoclonal antibodies seemed to be more effective in the reduction of uveitis flares.

Regulatory T Cells in Systemic Sclerosis.

In recent years, accumulating evidence suggest that regulatory T cells (Tregs) are of paramount importance for the maintenance of immunological self-tolerance and immune homeostasis, even though they represent only about 5-10% of the peripheral CD4+ T cells in humans. Their key role is indeed supported by the spontaneous development of autoimmune diseases after Tregs depletion in mice. Moreover, there is also a growing literature that investigates possible contribution of Tregs numbers and activity in various autoimmune diseases. The contribution of Tregs in autoimmune disease has opened up a new therapeutic avenue based on restoring a healthy balance between Tregs and effector T-cells, such as Treg-based cellular transfer or low-dose IL-2 modulation. These therapies hold the promise of modulating the immune system without immunosuppression, while several issues regarding efficacy and safety need to be addressed. Systemic sclerosis (SSc) is an orphan connective tissue disease characterized by extensive immune abnormalities but also microvascular injury and fibrosis. Recently, data about the presence and function of Tregs in the pathogenesis of SSc have emerged although they remain scarce so far. First, there is a general agreement in the medical literature with regard to the decreased functional ability of circulating Tregs in SSc. Second the quantification of Tregs in patients have led to contradictory results; although the majority of the studies report reduced frequencies, there are conversely some indications suggesting that in case of disease activity circulating Tregs may increase. This paradoxical situation could be the result of a compensatory, but inefficient, amplification of Tregs in the context of inflammation. Nevertheless, these results must be tempered with regards to the heterogeneity of the studies for the phenotyping of the patients and of the most importance for Tregs definition and activity markers. Therefore, taking into account the appealing developments of Tregs roles in autoimmune diseases, together with preliminary data published in SSc, there is growing interest in deciphering Tregs in SSc, both in humans and mice models, to clarify whether the promises obtained in other autoimmune diseases may also apply to SSc.

Soluble CD163 as a Potential Biomarker in Systemic Sclerosis.

OBJECTIVE: To evaluate the performance of serum and urinary sCD163 concentrations as possible biomarker in systemic sclerosis (SSc). METHODS: Urine and serum samples were obtained from SSc patients and age- and sex-matched controls. Serum and urinary sCD163 concentrations were measured by commercially available ELISA kit. SSc patients were assessed following international guidelines. Cross-sectional analyses were performed. RESULTS: Two hundred and three SSc patients were included. The control group consisted of 47 age- and sex-matched patients having noninflammatory diseases, mainly osteoporosis. Serum sCD163 levels were significantly higher in SSc patients compared with controls (mean ± SD: 529 ± 251 versus 385 ± 153 ng/mL; p < 0.001). Urinary sCD163 concentrations were higher in SSc patients than controls, but this did not reach significance (236 ± 498 versus 176 ± 173 ng/mg uCr; p = 0.580). The sCD163 concentrations were not associated with clinical, laboratory, and instrumental characteristics of SSc patients. CONCLUSION: To our knowledge, this is the first evaluation of both serum and urinary sCD163 levels in SSc. Our results show a significant difference for sera values that should be prioritized for further studies as compared to urinary measurements. Our results further support that the M2 macrophages/CD163 signaling system may play a role in the pathogenesis of SSc, although we could not identify a subset of SSc patients with higher concentrations.

Impaired quality of life in systemic sclerosis and patient perception of the disease: A large international survey.

OBJECTIVES: The purpose of this study was to assess health-related quality of life (HRQoL) and disease perception in a large, international group of patients with systemic sclerosis (SSc). METHODS: We placed a standardized questionnaire on a website for patient access. Socio-demographic information, disease characteristics, and self-assessment questionnaires-the Short Form 36 (SF-36) and the Revised Illness Perception Questionnaire (IPQ-R)-were collected. RESULTS: A total of 1902 patients from 60 countries were included. HRQoL appeared to be impaired in SSc, particularly for physical health (PCS, mean ± SD = 43.4 ± 23.4). SSc patients also had strong perceptions about the chronic nature and negative consequence of the disease, and experienced negative emotions due to SSc. Patients with diffuse cutaneous SSc had a poorer HRQoL than those with limited cutaneous SSc, for both physical (PCS, mean ± SD = 46.6 ± 23.7 vs. 39.8 ± 22.3; p < 0.0001) and mental components (MCS, mean ± SD = 53.8 ± 23.0 vs. 50.3 ± 23.2; p = 0.003). Late-stage SSc patients were more likely to perceive their disease chronic (p < 0.0001), less controllable (p = 0.03) and with more consequences (p = 0.008), but they had a better understanding of their disease and experienced fewer negative emotions. Raynaud's phenomenon and gastrointestinal complications were the organ involvements with the greatest impact on QoL, they were the two variables associated with the most negative perception of illness severity. CONCLUSION: This study, performed on the largest group ever set up for this purpose, confirms the major impact on QoL and the negative perceptions of their disease expressed by SSc patients. However, the perception of this illness tended to improve with disease duration, suggesting that patients find effective coping strategies.

Pan PPAR agonist IVA337 is effective in prevention and treatment of experimental skin fibrosis.

BACKGROUND: The pathogenesis of systemic sclerosis (SSc) involves a distinctive triad of autoimmune, vascular and inflammatory alterations resulting in fibrosis. Evidence suggests that peroxisome proliferator-activated receptors (PPARs) play an important role in SSc-related fibrosis and their agonists may become effective therapeutic targets. OBJECTIVE: To determine the expression of PPARs in human fibrotic skin and investigate the effects of IVA337, a pan PPAR agonist, in in vitro and in vivo models of fibrosis. METHODS: The antifibrotic effects of IVA337 were studied using a bleomycin-induced mouse model of dermal fibrosis. The in vivo effect of IVA337 on wound closure and inflammation were studied using an excisional model of wound healing. RESULTS: Low levels of PPARα and PPARγ were detected in the skin of patients with SSc compared with controls. In mice, IVA337 was associated with decreased extracellular matrix (ECM) deposition and reduced expression of phosphorylated SMAD2/3-intracellular effector of transforming growth factor (TGF)-ß1. Although the antifibrotic effect of pan PPAR was similar to that of PPARγ agonist alone, a significant downregulation of several markers of inflammation was associated with IVA337. Despite its anti-inflammatory and antifibrotic properties, IVA337 did not interfere with wound closure. In vitro effects of IVA337 included attenuation of transcription of ECM genes and alteration of canonical and non-canonical TGF-ß signalling pathways. CONCLUSIONS: These findings indicate that simultaneous activation of all three PPAR isoforms exerts a dampening effect on inflammation and fibrosis, making IVA337 a potentially effective therapeutic candidate in the treatment of fibrotic diseases including SSc.

Treatment with abatacept prevents experimental dermal fibrosis and induces regression of established inflammation-driven fibrosis.

OBJECTIVE: Activated T cells are the main component of the inflammatory skin infiltrates that characterise systemic sclerosis (SSc). Our aim was to investigate the efficacy of abatacept, which tempers T-cell activation, in reducing skin fibrosis in complementary mouse models of SSc. METHODS: The antifibrotic properties of abatacept were evaluated in the mouse models of bleomycin-induced dermal fibrosis and sclerodermatous chronic graft-versus-host disease, reflecting early and inflammatory stages of SSc. Thereafter, we studied the efficacy of abatacept in tight skin (Tsk-1) mice, an inflammation-independent mouse model of skin fibrosis. RESULTS: Abatacept efficiently prevented bleomycin-induced skin fibrosis and was also effective in the treatment of established fibrosis. In this model, abatacept decreased total and activated T-cell, B-cell and monocyte infiltration in the lesional skin. Abatacept did not protect CB17-SCID mice from the development of bleomycin-induced dermal fibrosis, which supports that T cells are necessary to drive the antifibrotic effects of abatacept. Upon bleomycin injections, skin interleukin (IL) 6 and IL-10 levels were significantly reduced upon abatacept treatment. Moreover, treatment with abatacept ameliorated fibrosis in the chronic graft-versus-host disease model, but demonstrated no efficacy in Tsk-1 mice. The tolerance of abatacept was excellent in the three mouse models. CONCLUSIONS: Using complementary models, we demonstrate that inhibition of T-cell activation by abatacept can prevent and induce the regression of inflammation-driven dermal fibrosis. Translation to human disease is now required, and targeting early and inflammatory stages of SSc sounds the most appropriate for positioning abatacept in SSc.

Combined effect of genetic background and gender in a mouse model of bleomycin-induced skin fibrosis.

INTRODUCTION: Systemic sclerosis (SSc) is a connective tissue disorder characterised by the development of skin fibrosis. Our current understanding of the disease pathogenesis is incomplete and the study of SSc is hindered, at least partially, by a lack of animal models that fully replicate the complex state of human disease. Murine model of bleomycin-induced dermal fibrosis encapsulates important events that take place early in the disease course. METHODS: To characterise the optimum in vivo parameters required for the successful induction of dermal fibrosis we subjected three commonly used mouse strains to repeated subcutaneous bleomycin injections. We aimed to identify the effects of genetic background and gender on the severity of skin fibrosis. We used male and female Balb/C, C57BL/6, and DBA/2 strains and assessed their susceptibility to bleomycin-induced fibrosis by measuring dermal thickness, hydroxyproline/collagen content and number of resident myofibroblasts, all of which are important indicators of the severity of skin fibrosis. All data are expressed as mean values ± SEM. The Mann-Whitney U test was used for statistical analysis with GraphPad Prism 6.04 software. RESULTS: Dermal fibrosis was most severe in Balb/C mice compared to C57BL/6 and DBA/2 suggesting that Balb/C mice are more susceptible to bleomycin-induced fibrosis. Analysis of the effect of gender on the severity of fibrosis showed that male Balb/C, C57BL/6, DBA/2 mice had a tendency to develop more pronounced fibrosis phenotype than female mice. Of potential importance, male Balb/C mice developed the most severe fibrosis phenotype compared to male C57BL/6 and male DBA/2 as indicated by significantly increased number of dermal myofibroblasts. CONCLUSION: Our study highlights the importance of genetic background and gender in the induction of murine dermal fibrosis. Robust and reproducible animal models of fibrosis are important research tools used in pharmacological studies which may lead to better understanding of the pathogenesis of fibrotic diseases and assist in identification of new drugs.