Myofibroblasts from scleroderma skin synthesize elevated levels of collagen and tissue inhibitor of metalloproteinase (TIMP-1) with two forms of TIMP-1

Cellular Transdifferentiation: A Crucial Mechanism of Fibrosis in Systemic Sclerosis

Systemic Sclerosis (SSc) is a systemic autoimmune disease of unknown etiology with a highly complex pathogenesis that despite extensive investigation is not completely understood. The clinical and pathologic manifestations of the disease result from three distinct processes: 1) Severe and frequently progressive tissue fibrosis causing exaggerated and deleterious accumulation of interstitial collagens and other extracellular matrix molecules in the skin and various internal organs; 2) extensive fibroproliferative vascular lesions affecting small arteries and arterioles causing tissue ischemic alterations; and 3) cellular and humoral immunity abnormalities with the production of numerous autoantibodies, some with very high specificity for SSc. The fibrotic process in SSc is one of the main causes of disability and high mortality of the disease. Owing to its essentially universal presence and the severity of its clinical effects, the mechanisms involved in the development and progression of tissue fibrosis have been extensively investigated, however, despite intensive investigation, the precise molecular mechanisms have not been fully elucidated. Several recent studies have suggested that cellular transdifferentiation resulting in the phenotypic conversion of various cell types into activated myofibroblasts may be one important mechanism. Here, we review the potential role that cellular transdifferentiation may play in the development of severe and often progressive tissue fibrosis in SSc.

TANGO1 Dances to Export of Procollagen from the Endoplasmic Reticulum

The endoplasmic reticulum (ER) to Golgi secretory pathway is an elegantly complex process whereby protein cargoes are manufactured, folded, and distributed from the ER to the cisternal layers of the Golgi stack before they are delivered to their final destinations. The export of large bulky cargoes such as procollagen and its trafficking to the Golgi is a sophisticated mechanism requiring TANGO1 (Transport ANd Golgi Organization protein 1. It is also called MIA3 (Melanoma Inhibitory Activity protein 3). TANGO1 has two prominent isoforms, TANGO1-Long and TANGO1-Short, and each isoform has specific functions. On the luminal side, TANGO1-Long has an HSP47 recruitment domain and uses this protein to collect collagen. It can also tether its paralog isoforms cTAGE5 and TALI and along with these proteins enlarges the vesicle to accommodate procollagen. Recent studies show that TANGO1-Long combines retrograde membrane flow with anterograde cargo transport. This complex mechanism is highly activated in fibrosis and promotes the excessive deposition of collagen in the tissues. The therapeutic targeting of TANGO1 may prove successful in the control of fibrotic disorders. This review focuses on TANGO1 and its complex interaction with other procollagen export factors that modulate increased vesicle size to accommodate the export of procollagen.

Back to the future: targeting the extracellular matrix to treat systemic sclerosis

Fibrosis is the excessive deposition of a stable extracellular matrix (ECM); fibrotic tissue is composed principally of highly crosslinked type I collagen and highly contractile myofibroblasts. Systemic sclerosis (SSc) is a multisystem autoimmune connective tissue disease characterized by skin and organ fibrosis. The fibrotic process has been recognized in SSc for >40 years, but drugs with demonstrable efficacy against SSc fibrosis in ameliorating the lung involvement have only recently been identified. Unfortunately, these treatments are ineffective at improving the skin score in patients with SSc. Previous clinical trials in SSc have largely focused on the cross-purposing of anti-inflammatory drugs and the use of immunosuppressive drugs from the transplantation field, which address inflammatory and/or autoimmune processes. Limited examination has taken place of specific anti-fibrotic agents developed through their ability to directly target the ECM in SSc by, for example, alleviating the persistent matrix stiffness and mechanotransduction that might be required for both the initiation and maintenance of fibrosis, including in SSc. However, because of the importance of the ECM in the SSc phenotype, attempts have now been made to identify drugs that specifically target the ECM, including some drugs that are currently under consideration for the treatment of cancer.

Caspase 1 Enhances Transport and Golgi Organization Protein 1 Expression to Promote Procollagen Export From the Endoplasmic Reticulum in Systemic Sclerosis Contributing to Fibrosis

OBJECTIVE

Transport and Golgi Organization protein 1 (TANGO1) is a protein that regulates the export of procollagen from the endoplasmic reticulum and has a role in the organization of exit sites for general protein export. What regulates the expression of TANGO1 and the role of TANGO1 in fibrosis is poorly understood and has never been studied in the setting of systemic sclerosis (SSc). We undertook this study to determine the role of TANGO1 in SSc fibrosis.

METHODS

SSc (n = 15) and healthy (n = 12) primary fibroblast lung cell lines were investigated for the expression of TANGO1. Histologic analyses for TANGO1 were performed on lung biopsy samples (n = 12 SSc patient samples and n = 8 healthy control samples).

RESULTS

SSc fibroblasts showed increased expression of TANGO1 protein in cultured fibroblasts. TANGO1 colocalizes with α-smooth muscle actin (α-SMA)-positive cells in SSc lung tissue and is highly up-regulated in the neointima of SSc vessels. TANGO1 expression was dependent on the inflammasome activation of caspase 1. It was also dependent on signaling from the interleukin-1 (IL-1) and transforming growth factor β (TGFβ) receptors. The decrease in TANGO1 down-regulated export of larger cargos including collagen and laminin. Reduced TANGO1 protein had no effect on smaller molecular weight cargoes; however, the secretion of elastin was significantly reduced.

CONCLUSION

TANGO1 is markedly increased in SSc fibroblasts and was found to be elevated in lung tissue in association with α-SMA-positive cells. TANGO1 expression is driven by inflammasome-dependent caspase 1 activation and is mediated by IL-1 and TGFβ downstream signaling. These observations suggest that during fibrosis, caspase 1 promotes the up-regulation of TANGO1 and the organization of endoplasmic reticulum exits sites, ultimately contributing to procollagen export and fibrosis.

Connexin 37, 40, 43 and Pannexin 1 Expression in the Gastric Mucosa of Patients with Systemic Sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs. Although its pathogenesis is not fully understood, connexins (Cxs) and pannexins (Panx) could be involved in the process of fibrosis. We analyzed the protein expression of Cx37, Cx40, Cx43, and Panx1 in the gastric mucosa of patients with SSc and healthy volunteers, using immunofluorescence staining. Protein levels of Cx37 were slightly increased, while the levels of Cx40 were significantly decreased in the lamina propria of the gastric mucosa of SSc patients compared to the controls. The changes were proportional to SSc severity, with the most prominent changes found in patients with severe diffuse cutaneous SSc. No differences in Cx43 or Panx1 levels were found between the analyzed groups of samples. The lack of changes in Cx43 expression, which has been previously associated with fibrosis, could be due to the weak expression of Cx43 in the gastric mucosa in general. Further studies on full-thickness gastric biopsies containing muscle layers and animal SSc models are needed to fully elucidate the role of Cxs and Panxs in SSc-associated fibrosis.

VEGF-Encoding, Gene-Activated Collagen-Based Matrices Promote Blood Vessel Formation and Improved Wound Repair

Disruption in vascularization during wound repair can severely impair healing. Proangiogenic growth factor therapies have shown great healing potential; however, controlling growth factor activity and cellular behavior over desired healing time scales remains challenging. In this study, we evaluated collagen-mimetic peptide (CMP) tethers for their capacity to control growth factor gene transfer and growth factor activity using our recently developed gene-activated hyaluronic acid-collagen matrix (GAHCM). GAHCM was comprised of DNA/polyethyleneimine (PEI) polyplexes that were retained on hyaluronic acid (HA)-collagen hydrogels using CMPs. We hypothesized that using CMP-collagen tethers to control vascular endothelial growth factor-A (VEGF-A) gene delivery in fibroblasts would provide a powerful strategy to modulate the proangiogenic behaviors of endothelial cells (ECs) for blood vessel formation, resulting in enhanced wound repair. In co-culture experiments, we observed that CMP-modified GAHCM induced tunable gene delivery in fibroblasts as predicted, and correspondingly, VEGF-A produced by the fibroblasts led to increased growth and persistent migration of ECs for at least 7 days, as compared to non-CMP-modified GAHCM. Moreover, when ECs were exposed to fibroblast-containing VEGF-GAHCM with higher levels of CMP modification (50% CMP-PEI, or 50 CP), high CD31 expression was stimulated, resulting in the formation of an interconnected EC network with a significantly higher network volume and a larger diameter network structure than controls. Application of VEGF-GAHCM with 50 CP in murine splinted excisional wounds facilitated prolonged prohealing and proangiogenic responses resulting in increased blood vessel formation, improved granulation tissue formation, faster re-epithelialization, and overall enhanced repair. These findings suggest the benefits of CMP-collagen tethers as useful tools to control gene transfer and growth factor activity for improved treatment of wounds.

Role of Inflammasomes in Keloids and Hypertrophic Scars-Lessons Learned from Chronic Diabetic Wounds and Skin Fibrosis

Keloids and hypertrophic scars are pathological cutaneous scars. They arise from excessive wound healing, which induces chronic dermal inflammation and results in overwhelming fibroblast production of extracellular matrix. Their etiology is unclear. Inflammasomes are multiprotein complexes that are important in proinflammatory innate-immune system responses. We asked whether inflammasomes participate in pathological scarring by examining the literature on scarring, diabetic wounds (also characterized by chronic inflammation), and systemic sclerosis (also marked by fibrosis). Pathological scars are predominantly populated by anti-inflammatory M2 macrophages and recent literature hints that this could be driven by non-canonical inflammasome signaling. Diabetic-wound healing associates with inflammasome activation in immune (macrophages) and non-immune (keratinocytes) cells. Fibrotic conditions associate with inflammasome activation and inflammasome-induced transition of epithelial cells/endothelial cells/macrophages into myofibroblasts that deposit excessive extracellular matrix. Studies suggest that mechanical stimuli activate inflammasomes via the cytoskeleton and that mechanotransduction-inflammasome crosstalk is involved in fibrosis. Further research should examine (i) the roles that various inflammasome types in macrophages, (myo)fibroblasts, and other cell types play in keloid development and (ii) how mechanical stimuli interact with inflammasomes and thereby drive scar growth. Such research is likely to significantly advance our understanding of pathological scarring and aid the development of new therapeutic strategies.

Therapeutic potential of mesenchymal stem cells for scleroderma induced in mouse model

OBJECTIVE

To examine the potential therapeutic effect of mesenchymal stem cells (MSCs) for experimental scleroderma.

MATERIALS AND METHODS

Fifty-four mice six-week-old (30-35 g) were studied. Hypochlorous acid (HOCl) induced scleroderma was considered. Mice were divided into 3 groups: (I) Control: Six mice did not receive any treatment and were sacrificed at the end of the experiment; (II) HOCl mice (induced scleroderma as a positive control): (III) MSCs-treated HOCl mice: Thirty six HOCl-induced mice were injected with MSCs (7.5 × 105) intravenous every week for 3 weeks. Skin pieces were taken from the backs of mice and lung tissue pieces. a smooth muscle actin (α-SMA) and transforming growth factor-β (TGF-β1) were analysed or fixed in 10 % formalin for skin and lung tissue histopathological analysis. Plasma nitric oxide (NO) was also assayed.

RESULTS

There was a significant rise in the NO level and of the cutaneous and lung tissue α-SMA and TGF-β1 in untreated scleroderma-induced mice. The values significantly normalized after MSC therapy over the 7 weeks duration of the study. The altered histopathology of the skin and lung tissues in the scleroderma-induced mice showed a remarkable tendency to normalization of the skin and lung parenchyma and vasculature.

CONCLUSION

There was a significant rise in the level of NO and skin and lung tissue α-SMA and TGF-β1 in untreated scleroderma-induced mice and values were significantly normalized after MSC therapy over the 7 weeks duration of the study. Altered histopathology of the skin and lung appeared nearly normal after MSC therapy.

[Updates in systemic sclerosis pathogenesis: Toward new therapeutic opportunities]

Systemic sclerosis is a rare connective tissue disease characterized by skin and several internal organ fibrosis, systemic vasculopathy and immune abnormalities. Even if fibroblasts and endothelial cells dysfunction, as well as lymphocytes and other immune cells implication are now well described, the exact origin and chronology of the disease pathogenesis remain unclear. Oxidative stress, influenced by genetic and environmental factors, seems to play a key role. Indeed, it seems to be implicated in the early phases of fibrosis development, vasculopathy and in immune tolerance abnormalities shared by all patients, although disease expression is heterogeneous. To date, no curative treatment is available. Even if immunosuppressive treatment or drugs acting on vascular system are proposed for some patients, overall, treatment efficiency remains modest. Only autologous hematopoietic stem cells transplantation, reserved for patients with severe or rapidly progressive fibrosis, has recently demonstrated efficiency, with lasting regression of fibrosis. Nevertheless, this treatment can expose to important, life-threatening toxicity. In the last decade, new mechanisms implicated in the pathogenesis of systemic sclerosis have been unraveled, bringing new therapeutic opportunities. In this review, we offer to focus on recent insights in the knowledge of systemic sclerosis pathogenesis and its implication in current and future medical care.

The impact of high-dose narrowband ultraviolet A1 on dermal thickness, collagen and matrix-metalloproteinases in animal model of scleroderma

OBJECTIVE

The main purpose of the present study was to define the impact of high-dose of 365±5nm ultraviolet A1 (UVA1) on dermal fibrosis in the pre-established, bleomycin-induced mouse model of scleroderma.

METHODS

DBA/2 strain mice with the pre-established, bleomycin-induced scleroderma were irradiated with cumulative UVA1 dose of 1200J/cm² and in parallel were challenged with prolonged administration of bleomycin. Non-treated groups served as the control. Light source emitting a narrow band UVA1 light of 365±5nm and 21mW/cm² power density was used in the study. Histological analysis was performed for the evaluation of dermal thickness. The expressions of matrix-metalloproteinase-1 (MMP-1), matrix-metalloproteinase-3 (MMP-3), collagen types I and III were evaluated by immunohistochemical analyses. The Mann - Whitney U test was used for statistical analysis.

RESULTS

Dermal thickness in mice injected with bleomycin during all the experiment (8weeks) and irradiated with UVA1 for the last 5weeks was significantly lower than that in mice challenged only with bleomycin for 8weeks (253.96±31.83μm and 497.43±57.83μm, respectively; P=0.002). The dermal thickness after phototherapy was lower as compared with the pre-existing fibrotic changes observed after 3weeks of bleomycin injections (253.96±31.83μm and 443.87±41.76μm, respectively; P=0.002). High-dose of UVA1 induced the 5.8- and 5.2-fold increase in MMP-1 and MMP-3 expressions, respectively, and the 1.2- and 1.4-fold decrease in collagen type I and collagen type III expressions in the pre-established, bleomycin-induced scleroderma model as compared to that in the control non-irradiated mice (P=0.002).

CONCLUSIONS

Our study has demonstrated that a cumulative 365±5nm UVA1 radiation dosage of 1200J/cm² not only prevents the progression of dermal fibrosis, but also induces a regression of pre-existing fibrotic changes.

Mir-155 is overexpressed in systemic sclerosis fibroblasts and is required for NLRP3 inflammasome-mediated collagen synthesis during fibrosis

BACKGROUND

Despite the important role that microRNAs (miRNAs) play in immunity and inflammation, their involvement in systemic sclerosis (SSc) remains poorly characterized. miRNA-155 (miR-155) plays a role in pulmonary fibrosis and its expression can be induced with interleukin (IL)-1β. SSc fibroblasts have activated inflammasomes that are integrally involved in mediating the myofibroblast phenotype. In light of this, we investigated whether miR-155 played a role in SSc and if its expression was dependent on inflammasome activation.

METHODS

miR-155 expression was confirmed in SSc dermal and lung fibroblasts by quantitative polymerase chain reaction (PCR). Wild-type and NLRP3-deficient murine fibroblasts were utilized to explore the regulation of miR-155 during inflammasome activation. miR-155-deficient fibroblasts and retroviral transductions with a miR-155 expression or control vectors were used to understand the contribution of miR-155 in fibrosis.

RESULTS

miR-155 was significantly increased and the highest expressing miRNA in SSc lung fibroblasts. Its expression was dependent on inflammasome activation as miR-155 expression could be blocked when inflammasome signaling was inhibited. In the absence of miR-155, inflammasome-mediated collagen synthesis could not be induced but was restored when miR-155 was expressed in miR-155-deficient fibroblasts.

CONCLUSIONS

miR-155 is upregulated in SSc. These results suggest that the inflammasome promotes the expression of miR-155 and that miR-155 is a critical miRNA that drives fibrosis.

Human Fibrotic Diseases: Current Challenges in Fibrosis Research

Human fibrotic diseases constitute a major health problem worldwide owing to the large number of affected individuals, the incomplete knowledge of the fibrotic process pathogenesis, the marked heterogeneity in their etiology and clinical manifestations, the absence of appropriate and fully validated biomarkers, and, most importantly, the current void of effective disease-modifying therapeutic agents. The fibrotic disorders encompass a wide spectrum of clinical entities including systemic fibrotic diseases such as systemic sclerosis (SSc), sclerodermatous graft vs. host disease, and nephrogenic systemic fibrosis, as well as numerous organ-specific disorders including radiation-induced fibrosis and cardiac, pulmonary, liver, and kidney fibrosis. Although their causative mechanisms are quite diverse and in several instances have remained elusive, these diseases share the common feature of an uncontrolled and progressive accumulation of fibrotic tissue in affected organs causing their dysfunction and ultimate failure. Despite the remarkable heterogeneity in the etiologic mechanisms responsible for the development of fibrotic diseases and in their clinical manifestations, numerous studies have identified activated myofibroblasts as the common cellular element ultimately responsible for the replacement of normal tissues with nonfunctional fibrotic tissue. Critical signaling cascades, initiated primarily by transforming growth factor-β (TGF-β), but also involving numerous cytokines and signaling molecules which stimulate profibrotic reactions in myofibroblasts, offer potential therapeutic targets. Here, we briefly review the current knowledge of the molecular mechanisms involved in the development of tissue fibrosis and point out some of the most important challenges to research in the fibrotic diseases and to the development of effective therapeutic approaches for this often fatal group of disorders. Efforts to further clarify the complex pathogenetic mechanisms of the fibrotic process should be encouraged to attain the elusive goal of developing effective therapies for these serious, untreatable, and often fatal disorders.

Enhanced neointimal fibroblast, myofibroblast content and altered extracellular matrix composition: Implications in the progression of human peripheral artery restenosis

BACKGROUND AND AIMS

Neointimal cellular proliferation of fibroblasts and myofibroblasts is documented in coronary artery restenosis, however, their role in peripheral arterial disease (PAD) restenosis remains unclear. Our aim was to investigate the role of fibroblasts, myofibroblasts, and collagens in restenotic PAD.

METHODS

Nineteen PAD restenotic plaques were compared with 13 de novo plaques. Stellate cells (H&E), fibroblasts (FSP-1), myofibroblasts (α-actin/vimentin/FSP-1), cellular proliferation (Ki-67), and apoptosis (caspase-3 with poly ADP-ribose polymerase) were evaluated by immunofluorescence. Collagens were evaluated by picro-sirius red stain with polarization microscopy. Smooth muscle myosin heavy chain (SMMHC), IL-6 and TGF-β cytokines were analyzed by immunohistochemistry.

RESULTS

Restenotic plaques demonstrated increased stellate cells (2.7 ± 0.15 vs.1.3 ± 0.15) fibroblasts (2282.2 ± 85.9 vs. 906.4 ± 134.5) and myofibroblasts (18.5 ± 1.2 vs.10.6 ± 1.0) p = 0.0001 for all comparisons. In addition, fibroblast proliferation (18.4% ± 1.2 vs.10.4% ± 1.1; p = 0.04) and apoptosis (14.6% ± 1.3 vs.11.2% ± 0.6; p = 0.03) were increased in restenotic plaques. Finally, SMMHC (2.6 ± 0.12 vs.1.4 ± 0.15; p = 0.0001), type III collagen density (0.33 ± 0.06 vs. 0.17 ± 0.07; p = 0.0001), IL-6 (2.08 ± 1.7 vs.1.03 ± 2.0; p = 0.01), and TGF-β (1.80 ± 0.27 vs. 1.11 ± 0.18; p = 0.05) were increased in restenotic plaques.

CONCLUSIONS

Our study suggests proliferation and apoptosis of fibroblast and myofibroblast with associated increase in type III collagen may play a role in restenotic plaque progression. Understanding pathways involved in proliferation and apoptosis in neointimal cells, may contribute to future therapeutic interventions for the prevention of restenosis in PAD.

Endothelial to Mesenchymal Transition (EndoMT) in the Pathogenesis of Human Fibrotic Diseases

Fibrotic diseases encompass a wide spectrum of clinical entities including systemic fibrotic diseases such as systemic sclerosis, sclerodermatous graft versus host disease, nephrogenic systemic fibrosis, and IgG₄-associated sclerosing disease, as well as numerous organ-specific disorders including radiation-induced fibrosis, and cardiac, pulmonary, liver, and kidney fibrosis. Although their causative mechanisms are quite diverse, these diseases share the common feature of an uncontrolled and progressive accumulation of fibrous tissue macromolecules in affected organs leading to their dysfunction and ultimate failure. The pathogenesis of fibrotic diseases is complex and despite extensive investigation has remained elusive. Numerous studies have identified myofibroblasts as the cells responsible for the establishment and progression of the fibrotic process. Tissue myofibroblasts in fibrotic diseases originate from several sources including quiescent tissue fibroblasts, circulating CD34+ fibrocytes, and the phenotypic conversion of various cell types including epithelial and endothelial cells into activated myofibroblasts. However, the role of the phenotypic transition of endothelial cells into mesenchymal cells (Endothelial to Mesenchymal Transition or EndoMT) in the pathogenesis of fibrotic disorders has not been fully elucidated. Here, we review the evidence supporting EndoMT's contribution to human fibrotic disease pathogenesis.

Intrinsic Deregulation of Vascular Smooth Muscle and Myofibroblast Differentiation in Mesenchymal Stromal Cells from Patients with Systemic Sclerosis

Introduction

Obliterative vasculopathy and fibrosis are hallmarks of systemic sclerosis (SSc), a severe systemic autoimmune disease. Bone marrow-derived mesenchymal stromal cells (MSCs) from SSc patients may harbor disease-specific abnormalities. We hypothesized disturbed vascular smooth muscle cell (VSMC) differentiation with increased propensity towards myofibroblast differentiation in response to SSc-microenvironment defining growth factors and determined responsible mechanisms.

Methods

We studied responses of multipotent MSCs from SSc-patients (SSc-MSCs) and healthy controls (H-MSCs) to long-term exposure to CTGF, b-FGF, PDGF-BB or TGF-β1. Differentiation towards VSMC and myofibroblast lineages was analyzed on phenotypic, biochemical, and functional levels. Intracellular signaling studies included analysis of TGF-β receptor regulation, SMAD, AKT, ERK1/2 and autocrine loops.

Results

VSMC differentiation towards both, contractile and synthetic VSMC phenotypes in response to CTGF and b-FGF was disturbed in SSc-MSCs. H-MSCs and SSc-MSCs responded equally to PDGF-BB with prototypic fibroblastic differentiation. TGF-β1 initiated myofibroblast differentiation in both cell types, yet with striking phenotypic and functional differences: In relation to H-MSC-derived myofibroblasts induced by TGF-β1, those obtained from SSc-MSCs expressed more contractile proteins, migrated towards TGF-β1, had low proliferative capacity, and secreted higher amounts of collagen paralleled by reduced MMP expression. Higher levels of TGF-β receptor 1 and enhanced canonical and noncanonical TGF-β signaling in SSc-MSCs accompanied aberrant differentiation response of SSc-MSCs in comparison to H-MSCs.

Conclusions

Deregulated VSMC differentiation with a shift towards myofibroblast differentiation expands the concept of disturbed endogenous regenerative capacity of MSCs from SSc patients. Disease related intrinsic hyperresponsiveness to TGF-β1 with increased collagen production may represent one responsible mechanism. Better understanding of repair barriers and harnessing beneficial differentiation processes in MSCs could widen options of autologous MSC application in SSc patients.

Endothelial to mesenchymal transition (EndoMT) in the pathogenesis of Systemic Sclerosis-associated pulmonary fibrosis and pulmonary arterial hypertension. Myth or reality?

Systemic Sclerosis (SSc) is a systemic autoimmune disease characterized by progressive fibrosis of skin and multiple internal organs and severe functional and structural microvascular alterations. SSc is considered to be the prototypic systemic fibrotic disorder. Despite currently available therapeutic approaches SSc has a high mortality rate owing to the development of SSc-associated interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH), complications that have emerged as the most frequent causes of disability and mortality in SSc. The pathogenesis of the fibrotic process in SSc is complex and despite extensive investigation the exact mechanisms have remained elusive. Myofibroblasts are the cells ultimately responsible for tissue fibrosis and fibroproliferative vasculopathy in SSc. Tissue myofibroblasts in SSc originate from several sources including expansion of quiescent tissue fibroblasts and tissue accumulation of CD34+ fibrocytes. Besides these sources, myofibroblasts in SSc may result from the phenotypic conversion of endothelial cells into activated myofibroblasts, a process known as endothelial to mesenchymal transition (EndoMT). Recently, it has been postulated that EndoMT may play a role in the development of SSc-associated ILD and PAH. However, although several studies have described the occurrence of EndoMT in experimentally induced cardiac, renal, and pulmonary fibrosis and in several human disorders, the contribution of EndoMT to SSc-associated ILD and PAH has not been generally accepted. Here, the experimental evidence supporting the concept that EndoMT plays a role in the pathogenesis of SSc-associated ILD and PAH will be reviewed.

Lipoic acid plays a role in scleroderma: insights obtained from scleroderma dermal fibroblasts

Introduction

Systemic sclerosis (SSc) is a connective tissue disease characterized by fibrosis of the skin and organs. Increase in oxidative stress and platelet-derived growth factor receptor (PDGFR) activation promote type I collagen (Col I) production, leading to fibrosis in SSc. Lipoic acid (LA) and its active metabolite dihydrolipoic acid (DHLA) are naturally occurring thiols that act as cofactors and antioxidants and are produced by lipoic acid synthetase (LIAS). Our goals in this study were to examine whether LA and LIAS were deficient in SSc patients and to determine the effect of DHLA on the phenotype of SSc dermal fibroblasts. N-acetylcysteine (NAC), a commonly used thiol antioxidant, was included as a comparison.

Methods

Dermal fibroblasts were isolated from healthy subjects and patients with diffuse cutaneous SSc. Matrix metalloproteinase (MMPs), tissue inhibitors of MMPs (TIMP), plasminogen activator inhibitor 1 (PAI-1) and LIAS were measured by enzyme-linked immunosorbent assay. The expression of Col I was measured by immunofluorescence, hydroxyproline assay and quantitative PCR. PDGFR phosphorylation and α-smooth muscle actin (αSMA) were measured by Western blotting. Student’s t-tests were performed for statistical analysis, and P-values less than 0.05 with two-tailed analysis were considered statistically significant.

Results

The expression of LA and LIAS in SSc dermal fibroblasts was lower than normal fibroblasts; however, LIAS was significantly higher in SSc plasma and appeared to be released from monocytes. DHLA lowered cellular oxidative stress and decreased PDGFR phosphorylation, Col I, PAI-1 and αSMA expression in SSc dermal fibroblasts. It also restored the activities of phosphatases that inactivated the PDGFR. SSc fibroblasts produced lower levels of MMP-1 and MMP-3, and DHLA increased them. In contrast, TIMP-1 levels were higher in SSc, but DHLA had a minimal effect. Both DHLA and NAC increased MMP-1 activity when SSc cells were stimulated with PDGF. In general, DHLA showed better efficacy than NAC in most cases.

Conclusions

DHLA acts not only as an antioxidant but also as an antifibrotic because it has the ability to reverse the profibrotic phenotype of SSc dermal fibroblasts. Our study suggests that thiol antioxidants, including NAC, LA, or DHLA, could be beneficial for patients with SSc.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-014-0411-6) contains supplementary material, which is available to authorized users.

Matrix remodeling in systemic sclerosis

Systemic sclerosis (SSc, scleroderma) is an often-fatal disease characterized by connective tissue fibrosis of skin and internal organs. In scleroderma, there is an excessive production and accumulation of extracellular matrix (ECM) components resulting from an increase in collagen synthesis and matrix stability. Understanding how this how excessive ECM is produced and remodeled may represent a novel therapeutic approach. In this review, the transcription factors and collagen-modifying enzymes underlying collagen overexpression and enhancing stability in SSc are discussed. Moreover, the role of matrix stiffness in promoting fibrosis via a feed-forward mechanism is discussed. Indeed, the emerging evidence is that enhanced ECM remodeling resulting in increased ECM stiffness may be sufficient in itself to sustain persistence fibrosis in SSc.

Pathogenesis of Systemic Sclerosis

Systemic scleroderma (SSc) is one of the most complex systemic autoimmune diseases. It targets the vasculature, connective tissue-producing cells (namely fibroblasts/myofibroblasts), and components of the innate and adaptive immune systems. Clinical and pathologic manifestations of SSc are the result of: (1) innate/adaptive immune system abnormalities leading to production of autoantibodies and cell-mediated autoimmunity, (2) microvascular endothelial cell/small vessel fibroproliferative vasculopathy, and (3) fibroblast dysfunction generating excessive accumulation of collagen and other matrix components in skin and internal organs. All three of these processes interact and affect each other. The disease is heterogeneous in its clinical presentation that likely reflects different genetic or triggering factor (i.e., infection or environmental toxin) influences on the immune system, vasculature, and connective tissue cells. The roles played by other ubiquitous molecular entities (such as lysophospholipids, endocannabinoids, and their diverse receptors and vitamin D) in influencing the immune system, vasculature, and connective tissue cells are just beginning to be realized and studied and may provide insights into new therapeutic approaches to treat SSc.

The significance of macrophage polarization subtypes for animal models of tissue fibrosis and human fibrotic diseases

The systemic and organ-specific human fibrotic disorders collectively represent one of the most serious health problems world-wide causing a large proportion of the total world population mortality. The molecular pathways involved in their pathogenesis are complex and despite intensive investigations have not been fully elucidated. Whereas chronic inflammatory cell infiltration is universally present in fibrotic lesions, the central role of monocytes and macrophages as regulators of inflammation and fibrosis has only recently become apparent. However, the precise mechanisms involved in the contribution of monocytes/macrophages to the initiation, establishment, or progression of the fibrotic process remain largely unknown. Several monocyte and macrophage subpopulations have been identified, with certain phenotypes promoting inflammation whereas others display profibrotic effects. Given the unmet need for effective treatments for fibroproliferative diseases and the crucial regulatory role of monocyte/macrophage subpopulations in fibrogenesis, the development of therapeutic strategies that target specific monocyte/macrophage subpopulations has become increasingly attractive. We will provide here an overview of the current understanding of the role of monocyte/macrophage phenotype subpopulations in animal models of tissue fibrosis and in various systemic and organ-specific human fibrotic diseases. Furthermore, we will discuss recent approaches to the design of effective anti-fibrotic therapeutic interventions by targeting the phenotypic differences identified between the various monocyte and macrophage subpopulations.

Recruitment of CD34(+) fibroblasts in tumor-associated reactive stroma: the reactive microvasculature hypothesis

Reactive stroma co-evolves with cancer, exhibiting tumor-promoting properties. It is also evident at sites of wound repair and fibrosis, playing a key role in tissue homeostasis. The specific cell types of origin and the spatial/temporal patterns of reactive stroma initiation are poorly understood. In this study, we evaluated human tumor tissue arrays by using multiple labeled, quantitative, spectral deconvolution microscopy. We report here a novel CD34/vimentin dual-positive reactive fibroblast that is observed in the cancer microenvironment of human breast, colon, lung, pancreas, thyroid, prostate, and astrocytoma. Recruitment of these cells occurred in xenograft tumors and Matrigel plugs in vivo and was also observed in stromal nodules associated with human benign prostatic hyperplasia. Because spatial and temporal data suggested the microvasculature as a common site of origin for these cells, we analyzed microvasculature fragments in organ culture. Interestingly, fibroblasts with identical phenotypic properties and markers expanded radially from microvasculature explants. We propose the concept of reactive microvasculature for the evolution of reactive stroma at sites of epithelial disruption common in both benign and malignant disorders. Data suggest that the reactive stroma response is conserved among tissues, in normal repair, and in different human cancers. A more clear understanding of the nature and origin of reactive stroma is needed to identify novel therapeutic targets in cancer and fibrosis.

B lymphocytes and B-cell activating factor promote collagen and profibrotic markers expression by dermal fibroblasts in systemic sclerosis

Introduction

B lymphocytes might play a pathogenic role in dermal fibrosis in systemic sclerosis (SSc). B-cell activating factor (BAFF), a key cytokine for B-cell activation, is increased in the serum and the skin of patients with SSc. However, the ability of B cells directly to stimulate dermal fibroblasts and the role of BAFF are not fully understood. We therefore investigated the involvement of B cells and BAFF in the expression of collagen and profibrotic markers by dermal fibroblasts.

Methods

Cocultures of blood B cells from healthy blood donors and normal or SSc dermal fibroblasts stimulated with anti-IgM and BAFF were performed. Alpha-SMA, TIMP1, MMP9, COL1A1, COL1A2, and COL3A1 mRNA expression were determined by quantitative RT-PCR. Soluble collagen, BAFF, IL-6, IL-1β, TGF-β1, and CCL2 protein secretion were assessed.

Results

Coculture of blood B cells and dermal fibroblasts isolated from SSc patients induced IL-6, TGF-β1, CCL2, and collagen secretion, as well as Alpha-SMA, TIMP1, and MMP9 expression in dermal fibroblasts. Transwell assays demonstrated that this induction was dependent on cell-cell contact. Addition of anti-IgM and BAFF to the coculture increased IL-6, CCL2, TGF-β1, and collagen secretion. B cell- and BAFF-induced collagen secretion was highly reduced by anti-TGF-β1 antibodies.

Conclusions

Our results showed for the first time a direct role of B cells on the production of collagen by dermal fibroblasts, which is further enhanced by BAFF. Thus, these results demonstrate a new pathogenic role of B cells and BAFF in fibrosis and systemic sclerosis.

Lentivirus-mediated ERK2 siRNA reduces joint capsule fibrosis in a rat model of post-traumatic joint contracture

Extracellular signal-regulated kinase (ERK)-2 is presumed to play an important role in the development of post-traumatic joint contractures. Using a rat injury model, we investigated whether treatment with ERK2 small interfering RNA (siRNA) could reduce the extent of joint capsule fibrosis after an induced injury. Rats were separated into three groups (n = 32 each): non-operated control group, operated contracture group and contracture-treatment group. Stable post-traumatic joint contracture was created through surgical intra-articular joint injury followed by eight weeks of immobilization. In the contracture-treatment group, the rats were treated with lentivirus (LV)-mediated ERK2 siRNA at days 3 and 7 post-surgery. The posterior joint capsule was assessed by western blotting, immunohistochemistry and biochemical analysis for changes in ERK2, phosphorylated (p)-ERK2, myofibroblast, total collagen and relative collagen Type III expression level. Biomechanical testing was used to assess the development of flexion contractures. Statistical analysis was performed using an analysis of variance. In the operated contracture group, rats that developed flexion contractures also showed elevated phosphorylated p-ERK2 expression. In the contracture-treatment group, ERK2 siRNA significantly reduced p-ERK2 expression levels, as well as the severity of flexion contracture development (p < 0.01). Myofibroblast numbers and measurements of total collagen content were also significantly reduced following ERK2 siRNA (p < 0.01). Relative collagen type III expression as a proportion of total of Types I and III collagen, however, was significantly increased in response to ERK2 siRNA (p < 0.01). Our findings demonstrate a role for ERK2 in the induction of joint capsule fibrosis after injury. Furthermore, we show that development of flexion contractures and the resultant increase of joint capsule fibrosis can be reduced by LV-mediated ERK2 siRNA treatment.

Role of endothelial to mesenchymal transition in the pathogenesis of the vascular alterations in systemic sclerosis

The pathogenesis of Systemic Sclerosis (SSc) is extremely complex, and despite extensive studies, the exact mechanisms involved are not well understood. Numerous recent studies of early events in SSc pathogenesis have suggested that unknown etiologic factors in a genetically receptive host trigger structural and functional microvascular endothelial cell abnormalities. These alterations result in the attraction, transmigration, and accumulation of immune and inflammatory cells in the perivascular tissues, which in turn induce the phenotypic conversion of endothelial cells and quiescent fibroblasts into activated myofibroblasts, a process known as endothelial to mesenchymal transition or EndoMT. The activated myofibroblasts are the effector cells responsible for the severe and frequently progressive fibrotic process and the fibroproliferative vasculopathy that are the hallmarks of SSc. Thus, according to this hypothesis the endothelial and vascular alterations, which include the phenotypic conversion of endothelial cells into activated myofibroblasts, play a crucial role in the development of the progressive fibrotic process affecting skin and multiple internal organs. The role of endothelial cell and vascular alterations, the potential contribution of endothelial to mesenchymal cell transition in the pathogenesis of the tissue fibrosis, and fibroproliferative vasculopathy in SSc will be reviewed here.

The inflammasome activating caspase 1 mediates fibrosis and myofibroblast differentiation in systemic sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is a chronic idiopathic disease of unknown etiology that is characterized by fibrosis of the skin and visceral organs mediated by activated myofibroblasts. The recently identified inflammasomes are cytosolic receptors that tightly regulate the activity of caspase 1 and downstream signaling molecules such as interleukin-1β (IL-1β) and IL-18. The nucleotide-binding oligomerization domain (NOD)-like receptor 3 (NLRP3) inflammasome has been implicated in the development of idiopathic pulmonary fibrosis. This study was undertaken to assess the role of the inflammasome in SSc-related dermal or pulmonary fibrosis.

METHODS

Inflammasome gene transcripts were assayed in fibroblasts obtained from patients with SSc. Caspase 1 activation in SSc primary dermal and lung fibroblasts was inhibited, and the levels of hydroxyproline, COL1A1, COL3A1, IL-1β, IL-18, and α-smooth muscle actin (α-SMA) were measured. The role of the inflammasome in dermal fibrosis was investigated in NLRP3(-/-) and ASC(-/-) mice.

RESULTS

We identified increased expression of 40 genes associated with the inflammasome or downstream signaling molecules in SSc fibroblasts. Inhibition of caspase 1 in SSc dermal and lung fibroblasts abrogated the secretion of collagens, IL-1β, and IL-18. In addition, we observed decreased expression of the myofibroblast protein α-SMA in SSc dermal fibroblasts treated with a caspase 1 inhibitor. Furthermore, NLRP3(-/-) mice and ASC(-/-) mice were resistant to bleomycin-induced skin fibrosis, which suggests a key role for the inflammasome in in vivo fibrosis.

CONCLUSION

Innate immune signaling contributes to SSc fibrosis via activation of the inflammasome and caspase 1. These results suggest that inflammasome activation may play an important role in the pathogenesis of SSc.

Effects of hydrogen peroxide on wound healing in mice in relation to oxidative damage

It has been established that low concentrations of hydrogen peroxide (H₂O₂) are produced in wounds and is required for optimal healing. Yet at the same time, there is evidence that excessive oxidative damage is correlated with poor-healing wounds. In this paper, we seek to determine whether topical application of H₂O₂ can modulate wound healing and if its effects are related to oxidative damage. Using a C57BL/6 mice excision wound model, H₂O₂ was found to enhance angiogenesis and wound closure at 10 mM but retarded wound closure at 166 mM. The delay in closure was also associated with decreased connective tissue formation, increased MMP-8 and persistent neutrophil infiltration. Wounding was found to increase oxidative lipid damage, as measured by F₂-isoprostanes, and nitrative protein damage, as measured by 3-nitrotyrosine. However H₂O₂ treatment did not significantly increase oxidative and nitrative damage even at concentrations that delay wound healing. Hence the detrimental effects of H₂O₂ may not involve oxidative damage to the target molecules studied.

Association of TIMP-1 +372 SNP with digital ulcer manifestation in female systemic sclerosis patients

A candidate gene for TIMP-1 gene located on the X-chromosome (rs4898) was selected for a control case study to investigate a possible association of this SNP with the susceptibility to systemic sclerosis and its digit ulcer manifestation. A total of 461 individuals of Italian Caucasian origin (228 SSc patients and 233 healthy control subjects) were genotyped for TIMP-1 +372 T/C single nucleotide polymorphism rs4898. Subgroups were analyzed according to the presence or absence of digital ulcers. The CC genotype and C allele frequencies were significantly lower in female SSc patients than in controls (OR 0.53, CI 0.29-0.96, p=0.03 and OR 0.72, CI 0.53-0.98 p=0.04, respectively). CC genotypes frequency was lower also in female patients with ulcers than those without ulcers (OR 0.37, CI 0.14-1.00, p=0.03). Furthermore, CC genotype and C allele frequencies were lower also in female patients with ulcers in comparison to female healthy control subjects (OR 0.27, CI 0.10-0.70, p=0.004; OR 0.60, CI 0.40-0.89, p=0.01, respectively). The TIMP-1 rs4898 polymorphism may play a protective role in the susceptibility to SSC in females, and in particular to digital ulcer formation.

Recent developments in myofibroblast biology: paradigms for connective tissue remodeling

The discovery of the myofibroblast has opened new perspectives for the comprehension of the biological mechanisms involved in wound healing and fibrotic diseases. In recent years, many advances have been made in understanding important aspects of myofibroblast basic biological characteristics. This review summarizes such advances in several fields, such as the following: i) force production by the myofibroblast and mechanisms of connective tissue remodeling; ii) factors controlling the expression of α-smooth muscle actin, the most used marker of myofibroblastic phenotype and, more important, involved in force generation by the myofibroblast; and iii) factors affecting genesis of the myofibroblast and its differentiation from precursor cells, in particular epigenetic factors, such as DNA methylation, microRNAs, and histone modification. We also review the origin and the specific features of the myofibroblast in diverse fibrotic lesions, such as systemic sclerosis; kidney, liver, and lung fibrosis; and the stromal reaction to certain epithelial tumors. Finally, we summarize the emerging strategies for influencing myofibroblast behavior in vitro and in vivo, with the ultimate goal of an effective therapeutic approach for myofibroblast-dependent diseases.

Sunitinib inhibits the phosphorylation of platelet-derived growth factor receptor β in the skin of mice with scleroderma-like features and prevents the development of the disease

OBJECTIVE

Systemic sclerosis (SSc) is characterized by fibrosis of the skin and visceral organs, vascular dysfunction, and immunologic dysregulation. Platelet-derived growth factors (PDGFs) have been implicated in the development of fibrosis and dysregulation of vascular function. We investigated the effects of sunitinib and sorafenib, two tyrosine kinase inhibitors that interfere with PDGF signaling, in a mouse model of diffuse SSc.

METHODS

SSc was induced in BALB/c mice by subcutaneous injections of HOCl daily for 6 weeks. Mice were randomized to treatment with sunitinib, sorafenib, or vehicle. The levels of native and phosphorylated PDGF receptor β (PDGFRβ) and vascular endothelial growth factor receptor (VEGFR) in the skin were assessed by Western blot and immunohistochemical analyses. Skin and lung fibrosis were evaluated by histologic and biochemical methods. Autoantibodies were detected by enzyme-linked immunosorbent assay, and spleen cell populations were analyzed by flow cytometry.

RESULTS

Phosphorylation of PDGFRβ and VEGFR was higher in fibrotic skin from HOCl-injected mice with SSc than from PBS-injected mice. Injections of HOCl induced cutaneous and lung fibrosis, increased the proliferation rate of fibroblasts in areas of fibrotic skin, increased splenic B cell and T cell counts, and increased anti-DNA topoisomerase I autoantibody levels in BALB/c mice. All of these features were reduced by sunitinib but not by sorafenib. Sunitinib significantly reduced the phosphorylation of both PDGF and VEGF receptors.

CONCLUSION

Inhibition of the hyperactivated PDGF and VEGF pathways by sunitinib prevented the development of fibrosis in HOCl-induced murine SSc and may represent a new SSc treatment for testing in clinical trials.

The mast cell stabilizer ketotifen reduces joint capsule fibrosis in a rabbit model of post-traumatic joint contractures

OBJECTIVES

Using a rabbit model of post-traumatic joint contractures, we investigated whether treatment with a mast cell stabilizer after joint injury would lessen the molecular manifestations of joint capsule fibrosis.

METHODS

Surgical joint injury was used to create stable post-traumatic contractures of the knee in skeletally mature New Zealand white rabbits. Four groups of animals were studied: a non-operated control group (n = 8), an operated contracture group (n = 13) and two operated groups treated with the mast cell stabilizer, ketotifen, at doses of 0.5 mg/kg (n = 9) and 1.0 mg/kg (n = 9) twice daily. Joint capsule fibrosis was assessed by quantifying the mRNA and protein levels of α-SMA, tryptase, TGF-β1, collagen I and collagen III. Significance was tested using an ANOVA analysis of variance.

RESULTS

The protein and mRNA levels of α-SMA, TGF-β1, tryptase and collagen I and III were significantly elevated in the operated contracture group compared to control (p < 0.01). In both ketotifen-treated groups, protein and mRNA levels of α-SMA, TGF-β1 and collagen I were significantly reduced compared to the operated contracture group (p < 0.01).

CONCLUSIONS

These data suggest an inflammatory pathway mediated by mast cell activation is involved in joint capsule fibrosis after traumatic injury.

Blockade of interleukin-6 receptor alleviates disease in mouse model of scleroderma

Activation of fibroblasts by interleukin-6 (IL-6) is implicated in the pathogenesis of scleroderma, suggesting that the inhibition of fibroblast activation may be a promising scleroderma treatment. In this study, we used an IL-6 blocking antibody (Ab) and Il-6 knockout (Il-6KO) mice to examine the role of IL-6 in the bleomycin (BLM)-induced mouse model of scleroderma. BLM was administered to C57BL/6 and Il-6KO mice to induce dermal sclerosis. BLM-treated and control phosphate-buffered saline-treated mice were treated with anti-mouse IL-6 receptor monoclonal Ab (MR16-1). Disease severity was evaluated by measuring dermal thickness and skin hardness, by counting the numbers of α-smooth muscle actin-positive cells and mast cells, and by examining the cutaneous draining lymph nodes. C57BL/6 mice with BLM induced scleroderma had elevated serum IL-6 levels and more severe dermal sclerosis than Il-6KO mice. Weekly administration of MR16-1, but not control Ab, prevented and improved dermal sclerosis, and also attenuated swelling of the draining lymph nodes. MR16-1 suppressed α-smooth muscle actin induction in IL-6-stimulated Il-6KO fibroblasts. Our results indicate that IL-6 contributes to BLM induced dermal sclerosis and that IL-6 receptor-specific monoclonal Ab may improve the symptoms of scleroderma by suppressing fibroblast activation.

Alteration of fibroblast phenotype by asbestos-induced autoantibodies

Pulmonary fibrosis is a relentlessly progressive disease for which the etiology can be idiopathic or associated with environmental or occupational exposures. There is not a clear explanation for the chronic and progressive nature of the disease, leaving treatment and prevention options limited. However, there is increasing evidence of an autoimmune component, since fibrotic diseases are often accompanied by production of autoantibodies. Because exposure to silicates such as silica and asbestos can lead to both autoantibodies and pulmonary/pleural fibrosis, these exposures provide an excellent tool for examining the relationship between these outcomes. This study explored the possibility that autoantibodies induced by asbestos exposure in mice would affect fibroblast phenotype. L929 fibroblasts and primary lung fibroblasts were treated with serum IgG from asbestos- or saline-treated mice, and tested for binding using cell-based ELISA, and for phenotypic changes using immunofluorescence, laser scanning cytometry and Sirius Red collagen assay. Autoantibodies in the serum of C57Bl/6 mice exposed to asbestos (but not sera from untreated mice) bound to mouse fibroblasts. The autoantibodies induced differentiation to a myofibroblast phenotype, as demonstrated by increased expression of smooth muscle α-actin (SMA), which was lost when the serum was cleared of IgG. Cells treated with purified IgG of exposed mice produced excess collagen. Using ELISA, we tested serum antibody binding to DNA topoisomerase (Topo) I, vimentin, TGFβ-R, and PDGF-Rα. Antibodies to DNA Topo I and to PDGF-Rα were detected, both of which have been shown by others to be able to affect fibroblast phenotype. The anti-fibroblast antibodies (AFA) also induced STAT-1 activation, implicating the PDGF-R pathway as part of the response to AFA binding. These data support the hypothesis that asbestos induces AFA that modify fibroblast phenotype, and suggest a mechanism whereby autoantibodies may mediate some of the fibrotic manifestations of asbestos exposure.

Anti-interleukin-6 receptor antibody, tocilizumab, for the treatment of autoimmune diseases

Interleukin (IL)-6 is a cytokine with multiple biological activities. It contributes to host defense against pathogens, whereas accelerated production of IL-6 plays a significant pathological role in various diseases. Clinical trials have demonstrated the efficacy of tocilizumab, a humanized anti-IL-6 receptor antibody, for patients with rheumatoid arthritis, Castleman's disease or juvenile idiopathic arthritis, leading to approval of this innovative drug for the treatment of these diseases. Since IL-6 has been demonstrated to play a significant role in the development of various other autoimmune and inflammatory diseases, tocilizumab can be expected to become a novel drug for such diseases as well.

Targeting ADAM-17/notch signaling abrogates the development of systemic sclerosis in a murine model

OBJECTIVE

Systemic sclerosis (SSc) is characterized by the fibrosis of various organs, vascular hyperreactivity, and immunologic dysregulation. Since Notch signaling is known to affect fibroblast homeostasis, angiogenesis, and lymphocyte development, we undertook this study to investigate the role of the Notch pathway in human and murine SSc.

METHODS

SSc was induced in BALB/c mice by subcutaneous injections of HOCl every day for 6 weeks. Notch activation was analyzed in tissues from mice with SSc and from patients with scleroderma. Mice with SSc were either treated or not treated with the γ-secretase inhibitor DAPT, a specific inhibitor of the Notch pathway, and the severity of the disease was evaluated.

RESULTS

As previously described, mice exposed to HOCl developed a diffuse cutaneous SSc with pulmonary fibrosis and anti-DNA topoisomerase I antibodies. The Notch pathway was hyperactivated in the skin, lung, fibroblasts, and splenocytes of diseased mice and in skin biopsy samples from patients with scleroderma. ADAM-17, a proteinase involved in Notch activation, was overexpressed in the skin of mice and patients in response to the local production of reactive oxygen species. In HOCl-injected mice, DAPT significantly reduced the development of skin and lung fibrosis, decreased skin fibroblast proliferation and ex vivo serum-induced endothelial H(2)O(2) production, and abrogated the production of anti-DNA topoisomerase I antibodies.

CONCLUSION

Our results show the pivotal role of the ADAM-17/Notch pathway in SSc following activation by reactive oxygen species. The inhibition of this pathway may represent a new treatment of this life-threatening disease.

The imbalanced expression of matrix metalloproteinases in nephrogenic systemic fibrosis

BACKGROUND

Nephrogenic systemic fibrosis (NSF) occurs in patients with renal dysfunction and gadolinium exposure. Although little is known about the pathogenesis of this disease, increased expression of transforming growth factor-beta has been recently demonstrated. Other fibrosing conditions have been shown to express an imbalance in matrix metalloproteinase (MMP) expression and their corresponding inhibitors. Myofibroblast differentiation, in which cells often express alpha-smooth muscle actin and achieve the ability to contract, is also a hallmark of fibrosis.

OBJECTIVE

We theorized that NSF may overexpress tissue inhibitor of metalloproteinase-1 (TIMP-1), while simultaneously showing decreased expression of MMP-1. As a secondary aim, we sought to evaluate the presence of smooth muscle actin in our samples.

METHODS

We applied immunohistochemistry to 16 skin biopsies from 10 patients with NSF using antibodies to TIMP-1, MMP-1, MMP-2, MMP-9, and alpha-smooth muscle actin. Samples from normal skin, scar, keloid and scleroderma were stained for comparison.

RESULTS

TIMP-1 was strongly expressed in all NSF specimens compared to normal skin. MMP-1 expression was nearly absent in all tested samples. In all 16 NSF cases, the dermal spindle cells did not stain for alpha-smooth muscle actin. MMP-2 and MMP-9 expression was variable but was increased compared to normal skin.

LIMITATIONS

The expression is semiquantitative and based on immunohistochemistry and unconfirmed by other techniques.

CONCLUSIONS

In NSF, TIMP-1 is strongly expressed and MMP-1 is nearly absent, characteristic of the MMP imbalances seen in other fibrosing processes. Using smooth muscle actin immunohistochemistry, there was no evidence of myofibroblast differentiation.

Proteomic analysis identification of a pattern of shared alterations in the secretome of dermal fibroblasts from systemic sclerosis and nephrogenic systemic fibrosis

A proteomic analysis of the secretome of cultured dermal fibroblasts from patients with systemic sclerosis (SSc) and nephrogenic systemic fibrosis (NSF) was performed to identify proteins that reflect the fibrotic process. Confluent culture supernatants from three cell strains each of normal, SSc, and NSF dermal fibroblasts were pooled separately, and each pool was labeled with a specific fluorochrome. The three pools were electrophoresed together on two-dimension SDS gels, and protein differential expression was evaluated by quantitative fluorescence analysis. The secretome analysis identified 1694 spots per sample, among which 890 spots (52%) were differentially increased or decreased (more than twofold) in SSc fibroblasts, and 985 spots (58%) were differentially increased or decreased in NSF fibroblasts compared with normal fibroblasts. Mass spectrometry analysis was then used to identify the proteins that had increased by the greatest extent in both NSF and SSc secretomes. Three reticulocalbin family members were among the 10 most up-regulated proteins. Confocal microscopy results validated the differential increase of reticulocalbin-1 in affected SSc and NSF skin, and Western blot findings demonstrated its presence in SSc sera. The secretomes of both SSc and NSF fibroblasts display a pattern of shared changes compared with the normal fibroblast secretome. The differentially increased proteins reflect an activated fibroblast phenotype and may represent a specific "fibrosis signature" that can be used as a biomarker for fibrotic diseases.

Lysophosphatidic acid-activated Cl- current activity in human systemic sclerosis skin fibroblasts

OBJECTIVES

SSc (scleroderma) is an often fatal disease characterized by widespread tissue fibrosis. Fibroblasts play a key role in SSc-associated fibrosis. This study was designed to determine: (i) whether fibroblasts isolated from skin of patients with SSc have increased lysophosphatidic acid-activated Cl- current (IClLPA) activity vs healthy controls; (ii) whether myofibroblast differentiation is involved in SSc skin fibrosis; and (iii) whether SSc fibroblasts have different proliferation rates vs controls.

METHODS

Skin biopsies were taken from involved and uninvolved skin of SSc patients and controls. Whole-cell perforated patch-clamping was used to measure IClLPA activity in fibroblasts isolated and cultured from these biopsies. Western blotting was used to measure α-smooth muscle actin (α-SMA). Proliferation was measured using a colorimetric assay.

RESULTS

Fibroblasts cultured from SSc skin show significantly increased IClLPA activity following LPA exposure compared with control skin fibroblasts. α-SMA protein was significantly increased in cultured SSc skin fibroblasts vs controls. No significant differences in proliferation rates were found.

CONCLUSIONS

Elevated IClLPA activity is a hallmark of SSc skin fibroblasts. Blocking IClLPA activation may be a new therapeutic approach for treating SSc-associated fibrosis.

New insights into the mechanism of fibroblast to myofibroblast transformation and associated pathologies

Myofibroblasts are a differentiated cell type essential for wound healing, participating in tissue remodeling following insult. Myofibroblasts are typically activated fibroblasts, although they can also be derived from other cell types, including epithelial cells, endothelial cells, and mononuclear cells. In most organ systems, cell signals initiated following tissue-specific insult or during the metastatic process lead to differentiation of fibroblasts or other precursor cells to the myofibroblast phenotype. In addition to their beneficial and necessary role in wound healing, myofibroblasts also contribute to a number of pathologies, primarily fibrotic processes and tumor invasiveness. This review explores both traditional and nontraditional concepts of myofibroblast differentiation in the cornea, skin, heart, and other tissues, as well as some of the pathologies associated with myofibroblast activities.

Pharmacotherapy of systemic sclerosis

IMPORTANCE OF THE FIELD

Systemic sclerosis (SSc) is an uncommon autoimmune disease with variable degrees of fibroproliferation in blood vessels and certain organs of the body. There is currently no cure. The purpose of this article is to review the current literature regarding pathogenesis and treatment of complications of SSc.

AREAS COVERED IN THIS REVIEW

All available articles regarding research related to SSc pathogenesis and treatment listed in the PubMed database were searched; relevant articles were then reviewed and used as sources of information for this review.

WHAT THE READER WILL GAIN

This review attempts to highlight for the reader some current thought regarding mechanisms of SSc pathogenesis and how autoimmunity relates to vascular changes and fibrogenesis of the disease, as well as providing a review of results of completed clinical trials and current ongoing clinical trials that address organ-specific or global therapies for this disease. This can aid physicians who provide medical care for patients with SSc.

TAKE HOME MESSAGE

SSc is a complex autoimmune disease, the pathogenesis of which, although not completely understood, is under active study; new insights into pathogenesis are continually being discovered. Although there is no effective disease-modifying treatment for patients with SSc, quality of life, morbidity and mortality can be improved by using targeted therapy directed at affecting the consequences of damage to lungs, blood vessels, kidneys and the gastrointestinal tract. Innovative approaches to treating SSc are under intense investigation.

The mast cell stabilizer ketotifen fumarate lessens contracture severity and myofibroblast hyperplasia: a study of a rabbit model of posttraumatic joint contractures

BACKGROUND

The propensity of joints to become stiff after trauma is widely appreciated, and the joint capsule is commonly recognized as the major motion-limiting anatomical structure. Affected joint capsules become fibrotic, characterized by myofibroblast and collagen hyperplasia. Mast cell hyperplasia is common within fibrotic tissue, and mast cells are known to synthesize many profibrotic mediators. We hypothesized that mast cell inhibition after skeletal injury would lessen contracture severity and reduce myofibroblast hyperplasia within the joint capsule.

METHODS

Posttraumatic contractures of the knee were created with use of a combination of intra-articular injury and internal immobilization in skeletally mature New Zealand White rabbits. Four groups of animals were studied: a nonoperative control group, a group with the operatively created contracture and no pharmacological treatment (the operative contracture group), and two groups with the operatively created contracture that were treated with a mast cell stabilizer, ketotifen fumarate, at a dose of either 0.5 or 1.0 mg/kg twice daily (the 0.5-mg/kg and 1.0-mg/kg ketotifen groups). After eight weeks of immobilization, flexion contractures were measured and the posterior aspect of the joint capsule was harvested for quantification of myofibroblast and mast cell numbers.

RESULTS

Flexion contractures developed in the operative contracture group (mean and standard deviation, 58 degrees +/- 14 degrees ), and the severity of the contractures was reduced in both the group treated with 0.5 mg/kg of ketotifen (42 degrees +/- 17 degrees ) and the group treated with 1.0 mg/kg of ketotifen (45 degrees +/- 10 degrees ) (p < 0.02). The joint capsule myofibroblast and mast cell numbers in the operative contracture group were significantly increased compared with the values in the control group (p < 0.001), and the myofibroblast and mast cell numbers in both ketotifen groups were significantly reduced compared with the values in the operative contracture group (p < 0.001).

CONCLUSIONS

The use of a mast cell stabilizer, ketotifen, was effective in reducing the biomechanical and cellular manifestations of joint capsule fibrosis in a rabbit model of posttraumatic joint contracture. This finding suggests that an inflammatory pathway, mediated by mast cell activation, is involved in the induction of joint capsule fibrosis after traumatic injury.

Matrix metalloproteinases and tissue inhibitors of metalloproteinases in gingival crevicular fluid during orthodontic tooth movement

Orthodontic tooth movement requires extensive re-modelling of the periodontium. Matrix metalloproteinases (MMPs) degrade the extracellular matrix during re-modelling, while their activity is regulated by the tissue inhibitors of metalloproteinases (TIMPs). The aim of this study was to investigate differences in MMP and TIMP levels in the gingival crevicular fluid (GCF) at the resorption and apposition sides of orthodontically moved teeth, and to compare these with control teeth. GCF samples were collected from eight orthodontic patients wearing fixed appliances with superelastic nickel-titanium coil springs. The samples were analysed by gelatin zymography, which allows detection of both active and latent MMPs, and reverse zymography for analysis of TIMPs. Western blotting was performed to confirm the identity of MMPs. The data were analysed using either the one-way analysis of variance or the Kruskal-Wallis test. In general, higher levels of MMPs and TIMPs were found at both the resorption and apposition sides compared with the control teeth. Remarkably, partially active MMP-1 was found in GCF from both the resorption and the apposition side but was barely present at the control teeth. TIMP-1 was strongly increased at the apposition side. Gelatinases were mainly present at the resorption side, while gelatinolytic fragments were exclusively detected at the apposition side. MMP-9, which is known to be involved in bone degradation, and a 48 kDa gelatinase were increased at the resorption side. The small increase in TIMP-1 at the resorption side might stimulate bone resorption, whereas the large increase at the apposition side reduces bone resorption. The analysis of MMPs and TIMPs may contribute to the improvement of orthodontic treatment regimens.

Akt blockade downregulates collagen and upregulates MMP1 in human dermal fibroblasts

Acutely transforming retrovirus AKT8 in rodent T-cell lymphoma (Akt) is a serine/threonine kinase that plays important roles in survival, cell-cycle progression, and cell proliferation, and has recently been implicated in collagen regulation. The aim of this study was to determine the role of Akt in collagen deposition by normal dermal fibroblasts, and to determine the sensitivity of cultured systemic sclerosis (SSc) fibroblasts to Akt inhibition. We show that blockade of Akt using pharmacological inhibitors, small interfering RNA (siRNA), and a dominant-negative Akt mutant led to inhibition of the basal type I collagen production. Furthermore, inhibition of Akt upregulated basal matrix metalloproteinase 1 (MMP1) production and reversed the inhibitory effect of transforming growth factor-beta (TGF-beta) on MMP1 gene expression. In addition, SSc fibroblasts were more sensitive to Akt inhibition, with respect to collagen and MMP1 production. These findings suggest that in human dermal fibroblasts, Akt has dual profibrotic effects, increasing collagen synthesis and decreasing its degradation via downregulation of MMP1. Akt could directly contribute to elevated collagen in SSc fibroblasts and it may represent an attractive target for therapy of SSc fibrosis.