Cellular and molecular aspects of vascular dysfunction in systemic sclerosis

Serum adropin level and ENHO gene expression in systemic sclerosis

Adropin, a secreted protein, is encoded by the energy homeostasis associated (ENHO) gene. It has been implicated in the several physiological and pathological processes such as angiogenesis and apoptosis. Therefore, the aim of present study was to investigate serum adropin levels and ENHO gene expressions in systemic sclerosis (SSc) characterized by vasculopathy, inflammation, and progressive fibrosis of the skin and internal organs. The study includes 27 patients with SSc, 39 patients with Behçet's disease (BD), and 20 healthy controls (HC). Serum adropin levels and ENHO gene expressions by peripheral blood mononuclear cells were analyzed by ELISA method and by real-time PCR, respectively. The serum adropin levels were higher in the SSc and BD groups than in the HC group (p = 0.023 and p < 0.001, respectively). However, there were no significant differences among the groups in terms of ENHO gene expressions (p ANOVA = 0.149). There was no significant difference between the limited and diffuse cutaneous subtypes of SSc in terms of serum adropin level and ENHO gene expression. Moreover, serum adropin level and ENHO gene expression were not associated with the disease activity and severity indexes. ENHO gene expression was correlated with the triglyceride levels in the BD group (r = -0.426, p = 0.027). The augmented serum adropin levels may be expected in the chronic inflammatory disease and seem not to be characteristic of only SSc. However, further studies are needed to explain the precise role of adropin in SSc.

Current perspectives on the immunopathogenesis of systemic sclerosis

Systemic sclerosis (SSc or scleroderma) is a progressive and highly debilitating autoimmune disorder characterized by inflammation, vasculopathy, and extensive fibrosis. SSc is highly heterogeneous in its clinical presentation, extent and severity of skin and internal organ involvement, and clinical course and has the highest fatality rate among connective tissue diseases. While clinical outcomes have improved in recent years, no current therapy is able to reverse or slow the natural progression of SSc, a reflection of its complex pathogenesis. Although activation of the immune system has long been recognized, the mechanisms responsible for the initiation of autoimmunity and the role of immune effector pathways in the pathogenesis of SSc remain incompletely understood. This review summarizes recent progress in disease pathogenesis with particular focus on the immunopathogenetic mechanisms of SSc.

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.

Vascular Remodelling and Mesenchymal Transition in Systemic Sclerosis

Fibrosis of the skin and of internal organs, autoimmunity, and vascular inflammation are hallmarks of Systemic Sclerosis (SSc). The injury and activation of endothelial cells, with hyperplasia of the intima and eventual obliteration of the vascular lumen, are early features of SSc. Reduced capillary blood flow coupled with deficient angiogenesis leads to chronic hypoxia and tissue ischemia, enforcing a positive feed-forward loop sustaining vascular remodelling, further exacerbated by extracellular matrix accumulation due to fibrosis. Despite numerous developments and a growing number of controlled clinical trials no treatment has been shown so far to alter SSc natural history, outlining the need of further investigation in the molecular pathways involved in the pathogenesis of the disease. We review some processes potentially involved in SSc vasculopathy, with attention to the possible effect of sustained vascular inflammation on the plasticity of vascular cells. Specifically we focus on mesenchymal transition, a key phenomenon in the cardiac and vascular development as well as in the remodelling of injured vessels. Recent work supports the role of transforming growth factor-beta, Wnt, and Notch signaling in these processes. Importantly, endothelial-mesenchymal transition may be reversible, possibly offering novel cues for treatment.

Pericytes: A newly recognized player in wound healing

Pericytes have generally been considered in the context of stabilizing vessels, ensuring the blood barriers, and regulating the flow through capillaries. However, new reports suggest that pericytes may function at critical times to either drive healing with minimal scarring or, perversely, contribute to fibrosis and ongoing scar formation. Beneficially, pericytes probably drive much of the vascular involution that occurs during the transition from the regenerative to the resolution phases of healing. Pathologically, pericytes can assume a fibrotic phenotype and promote scarring. This perspective will discuss pericyte involvement in wound repair and the relationship pericytes form with the parenchymal cells of the skin. We will further evaluate the role pericytes may have in disease progression in relation to chronic wounds and fibrosis.

Skin fibrosis correlates with circulating thyrotropin levels in systemic sclerosis: translational association with Hashimoto's thyroiditis

Systemic sclerosis (SSc) is a connective tissue disease, characterized by cutaneous and multi-organ fibrosis, and vascular abnormalities. Skin thickening is a characteristic feature of SSc and resembles myxedematous skin. Our aim was to correlate the degree of skin involvement in SSc patients with serum TSH levels, since TSH receptors are widely expressed in human tissues, including the skin. In this cross-sectional study, we enrolled 70 SSc patients, all females with a mean age of 47 ± 11 year. Thirty-five age- and sex-matched HT patients were recruited, as controls. Subjects under L-thyroxine therapy and/or with positive anti-TSH receptor antibodies were excluded. In all subjects, we measured serum TSH, FT4, and free tri-iodothyronine (FT3) levels. Skin thickness was evaluated using the modified Rodnan total skin score (mRSS). mRSS averaged 14 ± 9 for SSc and 4 ± 6 for HT patients. TSH levels positively correlated with skin scores in both SSc and HT patients groups. In SSc patients, FT3 and FT4 showed an inverse correlation with mRSS, while in HT only FT4 levels showed this inverse significance. When divided by cutaneous extent, SSc patients with diffuse disease form had higher TSH serum levels compared to those with the limited form; additionally, the correlations between TSH, FT4, and mRSS reached statistical significance. Our preliminary data clearly indicate that serum TSH is higher in SSc patients with more severe skin disease, and significantly correlate with the mRSS. Therefore, TSH could play a role in the development of cutaneous changes in SSc patients.

Efficient therapy of ischaemic lesions with VEGF121-fibrin in an animal model of systemic sclerosis

Background

In systemic sclerosis (SSc), chronic and uncontrolled overexpression of vascular endothelial growth factor (VEGF) results in chaotic vessels, and intractable fingertip ulcers. Vice versa, VEGF is a potent mediator of angiogenesis if temporally and spatially controlled. We have addressed this therapeutic dilemma in SSc by a novel approach using a VEGF₁₂₁ variant that covalently binds to fibrin and gets released on demand by cellular enzymatic activity. Using University of California at Davis (UCD)-206 chickens, we tested the hypothesis that cell-demanded release of fibrin-bound VEGF₁₂₁ leads to the formation of stable blood vessels, and clinical improvement of ischaemic lesions.

Methods

Ninety-one early and late ischaemic comb and neck skin lesions of UCD-206 chickens were treated locally with VEGF₁₂₁-fibrin, fibrin alone, or left untreated. After 1 week of treatment the clinical outcome was assessed. Angiogenesis was studied by immunofluorescence staining of vascular markers quantitatively analysed using TissueQuest.

Results

Overall, 79.3% of the lesions treated with VEGF₁₂₁-fibrin showed clinical improvement, whereas 71.0% of fibrin treated controls, and 93.1% of untreated lesions deteriorated. This was accompanied by significantly increased growth of stable microvessels, upregulation of the proangiogenic VEGFR-2 and its regulator TAL-1, and increase of endogenous endothelial VEGF expression.

Conclusions

Our findings in the avian model of SSc suggest that cell-demanded release of VEGF₁₂₁ from fibrin matrix induces controlled angiogenesis by differential regulation of VEGFR-1 and VEGFR-2 expression, shifting the balance towards the proangiogenic VEGFR-2. The study shows the potential of covalently conjugated VEGF-fibrin matrices for the therapy of ischaemic lesions such as fingertip ulcers.

The Endothelial-mesenchymal Transition in Systemic Sclerosis Is Induced by Endothelin-1 and Transforming Growth Factor-β and May Be Blocked by Macitentan, a Dual Endothelin-1 Receptor Antagonist

OBJECTIVE

High endothelin-1 (ET-1) and transforming growth factor-β (TGF-β) levels may induce in healthy endothelial cells (EC) an endothelial-to-mesenchymal transition (EndMT). The same cytokines are associated with fibrosis development in systemic sclerosis (SSc). Although EndMT has not been definitively shown in SSc, this process, potentially induced by a stimulatory loop involving these 2 cytokines, overexpressed in this disease might contribute to fibroblast accumulation in affected tissues. Macitentan (MAC), an ET-1 receptor antagonist interfering with this loop, might prevent EndMT and fibroblast accumulation.

METHODS

EC, isolated from healthy controls (HC) and patients with SSc, were treated with ET-1 and TGF-β and successively analyzed for gene and protein expressions of endothelial and mesenchymal markers, and for Sma- and Mad-related (SMAD) phosphorylation. Further, in the supernatants, we evaluated ET-1 and TGF-β production by ELISA assay. In each assay we evaluated the ability of MAC to inhibit both the TGF-β and ET-1 effects.

RESULTS

We showed that both TGF-β and ET-1 treatments induced an activation of the EndMT process in SSc-EC as reported in HC cells. The ELISA assays showed a mutual TGF-β and ET-1 induction in both SSc-EC and HC-EC. A statistically significant increase of SMAD phosphorylation after treatment was observed in SSc-EC. In each assay, MAC inhibited both TGF-β and ET-1 effects.

CONCLUSION

Our work is the first demonstration in literature that SSc-EC, under the synergistic effect of TGF-β and ET-1, may transdifferentiate toward myofibroblasts, thus contributing to fibroblast accumulation. MAC, interfering with this process in vitro, may offer a new potential therapeutic strategy against fibrosis.

From pathogenesis to therapy--Perspective on treatment strategies in fibrotic diseases

Although fibrosis is becoming increasingly recognized as a major cause of morbidity and mortality in modern societies, there are very few treatment strategies available that specifically target the pathogenesis of fibrosis. Early in disease, inflammation and vascular changes and an increase in reactive oxygen species play pivotal roles. After inflammation has subsided, fibrosis and scarring are predominant in later phases. Fibrosis is driven by a complex, not-yet fully understood interplay between inflammatory cells on one hand and endothelium and fibroblasts on the other hand. The latter are regarded as the key players due to their extensive synthesis of extracellular matrix components which results in skin and organ fibrosis. Various cytokines orchestrate altered functions of the mentioned cell types. There are promising targets with therapeutic potential that have been extensively characterized in recent years connected with the hope to translate these preclinical results into clinical practice.

Microangiopathy triggers, and inducible nitric oxide synthase exacerbates dextran sulfate sodium-induced colitis

Ulcerative colitis (UC) is a representative clinical manifestation of inflammatory bowel disease that causes chronic gastrointestinal tract inflammation. Dextran sulfate sodium (DSS)-induced colitis mice have been used to investigate UC pathogenesis, and in this UC model, disturbance and impairment of the mucosal epithelium have been reported to cause colitis. However, how DSS sporadically breaks down the epithelium remains unclear. In this study, we focused on the colonic microcirculation and myenteric neurons of DSS-induced colitis. Moreover, we examined the potential of myenteric neurons as a target to prevent exacerbation of colitis. Fluorescent angiographic and histopathological studies revealed that DSS administration elicited blood vessel disruption before epithelial disorders appeared. Ischemic conditions in the lamina propria induced inducible nitric oxide synthase (iNOS) expression in myenteric neurons as colitis aggravated. When neuronal activity was inhibited with butylscopolamine, neuronal iNOS expression decreased, and the exacerbation of colitis was prevented. These results suggested that DSS-induced colitis was triggered by microcirculatory disturbance in the mucosa, and that excessive neuronal excitation aggravated colitis. During remission periods of human UC, endoscopic inspection of the colonic microcirculation may enable the early detection of disease recurrence, and inhibition of neuronal iNOS expression may prevent the disease from worsening.

Macro- and microvascular disease in systemic sclerosis

Vasculopathy is common in patients with connective tissue disease and can be directly implicated in the pathogenesis of the disease. Systemic sclerosis is an auto-immune multiorgan connective tissue disorder characterized by fibrosis of the skin and visceral organs and vascular disease. Micro- and macro-vessels are a direct target of the disease. In this review, we present the various clinical manifestations of the vasculopathy that can be present in SSc patients, and then discuss the various aspects of the pathophysiology of the vascular disorders.

Systemic sclerosis

Systemic sclerosis is a complex autoimmune disease characterized by a chronic and frequently progressive course and by extensive patient-to-patient variability. Like other autoimmune diseases, systemic sclerosis occurs more frequently in women, with a peak of onset in the fifth decade of life. The exact cause of systemic sclerosis remains elusive but is likely to involve environmental factors in a genetically primed individual. Pathogenesis is dominated by vascular changes; evidence of autoimmunity with distinct autoantibodies and activation of both innate and adaptive immunity; and fibrosis of the skin and visceral organs that results in irreversible scarring and organ failure. Intractable progression of vascular and fibrotic organ damage accounts for the chronic morbidity and high mortality. Early and accurate diagnosis and classification might improve patient outcomes. Screening strategies facilitate timely recognition of life-threatening complications and initiation of targeted therapies to halt their progression. Effective treatments of organ-based complications are now within reach. Discovery of biomarkers - including autoantibodies that identify patient subsets at high risk for particular disease complications or rapid progression - is a research priority. Understanding the key pathogenetic pathways, cell types and mediators underlying disease manifestations opens the door for the development of targeted therapies with true disease-modifying potential. For an illustrated summary of this Primer, visit: http://go.nature.com/lchkcA.

Lipid rafts: integrated platforms for vascular organization offering therapeutic opportunities

Research on the nanoscale membrane structures known as lipid rafts is relevant to the fields of cancer biology, inflammation and ischaemia. Lipid rafts recruit molecules critical to signalling and regulation of the invasion process in malignant cells, the leukocytes that provide immunity in inflammation and the endothelial cells that build blood and lymphatic vessels, as well as the patterning of neural networks. As angiogenesis is a common denominator, regulation of receptors and signalling molecules critical to angiogenesis is central to the design of new approaches aimed at reducing, promoting or normalizing the angiogenic process. The goal of this review is to highlight some of the key issues that indicate the involvement of endothelial cell lipid rafts at each step of so-called 'sprouting angiogenesis', from stimulation of the vascular endothelial growth factor to the choice of tip cells, activation of migratory and invasion pathways, recruitment of molecules that guide axons in vascular patterning and maturation of blood vessels. Finally, the review addresses opportunities for future studies to define how these lipid domains (and their constituents) may be manipulated to stimulate the so-called 'normalization' of vascular networks within tumors, and be identified as the main target, enabling the development of more efficient chemotherapeutics and cancer immunotherapies.

Novel non-calcemic secosteroids that are produced by human epidermal keratinocytes protect against solar radiation

CYP11A1 hydroxylates the side chain of vitamin D3 (D3) in a sequential fashion [D3→20S(OH)D3→20,23(OH)2D3→17,20,23(OH)3D3], in an alternative to the classical pathway of activation [D3→25(OH)D3→1,25(OH)2D3]. The products/intermediates of the pathway can be further modified by the action of CYP27B1. The CYP11A1-derived products are biologically active with functions determined by the lineage of the target cells. This pathway can operate in epidermal keratinocytes. To further define the role of these novel secosteroids we tested them for protective effects against UVB-induced damage in human epidermal keratinocytes, melanocytes and HaCaT keratinocytes, cultured in vitro. The secosteroids attenuated ROS, H2O2 and NO production by UVB-irradiated keratinocytes and melanocytes, with an efficacy similar to 1,25(OH)2D3, while 25(OH)D3 had lower efficacy. These attenuations were also seen to some extent for the 20(OH)D3 precursor, 20S-hydroxy-7-dehydrocholesterol. These effects were accompanied by upregulation of genes encoding enzymes responsible for defense against oxidative stress. Using immunofluorescent staining we observed that the secosteroids reduced the generation cyclobutane pyrimidine dimers in response to UVB and enhanced expression of p53 phosphorylated at Ser-15, but not at Ser-46. Additional evidence for protection against DNA damage in cells exposed to UVB and treated with secosteroids was provided by the Comet assay where DNA fragmentation was markedly reduced by 20(OH)D3 and 20,23(OH)2D3. In conclusion, novel secosteroids that can be produced by the action of CYP11A1 in epidermal keratinocytes have protective effects against UVB radiation. This article is part of a special issue entitled '17th Vitamin D Workshop'.

Cellular interactions in the pathogenesis of interstitial lung diseases

Interstitial lung disease (ILD) encompasses a large and diverse group of pathological conditions that share similar clinical, radiological and pathological manifestations, despite potentially having quite different aetiologies and comorbidities. Idiopathic pulmonary fibrosis (IPF) represents probably the most aggressive form of ILD and systemic sclerosis is a multiorgan fibrotic disease frequently associated with ILD. Although the aetiology of these disorders remains unknown, in this review we analyse the pathogenic mechanisms by cell of interest (fibroblast, fibrocyte, myofibroblast, endothelial and alveolar epithelial cells and immune competent cells). New insights into the complex cellular contributions and interactions will be provided, comparing the role of cell subsets in the pathogenesis of IPF and systemic sclerosis.

Distinct cell populations contribute to the complex pathogenesis of IPF and systemic sclerosis-associated ILDhttp://ow.ly/AjFaz

Molecular control of capillary morphogenesis and maturation by recognition and remodeling of the extracellular matrix: functional roles of endothelial cells and pericytes in health and disease

This review addresses fundamental mechanisms underlying how capillaries form in three-dimensional extracellular matrices and how endothelial cells (ECs) and pericytes co-assemble to form capillary networks. In addition to playing a critical role in supplying oxygen and nutrients to tissues, recent work suggests that blood vessels supply important signals to facilitate tissue development. Here, we hypothesize that another major function of capillaries is to supply signals to suppress major disease mechanisms including inflammation, infection, thrombosis, hemorrhage, edema, ischemic injury, fibrosis, autoimmune disease and tumor growth/progression. Capillary dysfunction plays a key pathogenic role in many human diseases, and thus, this suppressing function may be attenuated and central toward the initiation and progression of disease. We describe how capillaries form through creation of EC-lined tube networks and vascular guidance tunnels in 3D extracellular matrices. Pericytes recruit to the abluminal EC tube surface within these tunnel spaces, and work together to assemble the vascular basement membrane matrix. These processes occur under serum-free conditions in 3D collagen or fibrin matrices and in response to five key growth factors which are stem cell factor, interleukin-3, stromal-derived factor-1α, fibroblast growth factor-2 and insulin. In addition, we identified a key role for EC-derived platelet-derived growth factor-BB and heparin-binding epidermal growth factor in pericyte recruitment and proliferation to promote EC-pericyte tube co-assembly and vascular basement membrane matrix deposition. A molecular understanding of capillary morphogenesis and maturation should lead to novel therapeutic strategies to repair capillary dysfunction in major human disease contexts including cancer and diabetes.

A vascular mechanistic approach to understanding Raynaud phenomenon

During exposure to cold, our bodies attempt to maintain normal core temperature by restricting heat loss through cutaneous vasoconstriction, and by increasing heat production through shivering and nonshivering thermogenesis. In selected areas of human skin (including on the fingers and toes), the vascular system has specialized structural and functional features that enable it to contribute to thermoregulation. These features include arteriovenous anastomoses, which directly connect the arterial and venous systems and bypass the nutritional capillaries supplying blood to the skin tissue. Of note, Raynaud phenomenon predominantly affects the arterial territories supplying these specialized areas of skin. Indeed, Raynaud phenomenon can be considered a disorder of vascular thermoregulatory control. This Review presents an understanding of Raynaud phenomenon in the context of vascular and thermoregulatory control mechanisms, including the role of unique thermosensitive vascular structural and functional specialization, and describes the potential role of thermogenesis in this disorder. This new approach provides remarkable insight into the disease process and builds a framework to critically appraise the existing knowledge base. This paradigm also explains the deficiencies in some current therapeutic approaches, and highlights new areas of potential relevance to the pathogenesis and treatment of Raynaud phenomenon that should be expanded and explored.

Systemic sclerosis induces pronounced peripheral vascular dysfunction characterized by blunted peripheral vasoreactivity and endothelial dysfunction

Systemic sclerosis (SSc) vasculopathy can result in a digital ulcer (DU) and/or pulmonary arterial hypertension (PAH). We hypothesized that bedside brachial artery flow-mediated dilation (FMD) testing with duplex ultrasound could be used in SSc patients to identify features of patients at risk for DU or PAH. Thirty-eight SSc patients were compared to 52 age-matched healthy controls from the VAMC Utah Vascular Research Laboratory. Peripheral hemodynamics, arterial structure, and endothelial function were assessed by duplex ultrasound. A blood pressure cuff was applied to the forearm and 5-min ischemia was induced. Post-occlusion, brachial artery vascular reactivity (peak hyperemia/area under the curve [AUC]), shear rate, and endothelial function (FMD) were measured. SSc patients had smaller brachial artery diameters (p < 0.001) and less reactive hyperemia (p < 0.001), peak shear rate (p = 0.03), and brachial artery FMD (p < 0.001) compared with healthy controls. Brachial artery FMD was lower (p < 0.05) in SSc patients with DU. Tertile analysis suggested the 2 lower FMD tertiles (<5.40 %) had a 40-50 % chance of presenting with DU while the SSc patients with highest FMD tertile (>5.40 %) had less than 15 % chance of DU. All brachial artery FMD measurements were similar between SSc patients with and without PAH (all p > 0.05). Compared to healthy controls, SSc patients had significantly smaller brachial artery diameter and blunted peripheral vascular reactivity and endothelial function. SSc patients with DU have even greater impairments in endothelial function compared to those without DU. FMD testing has clinical utility to identify SSc patients at risk for DU.

MMP-12 deficiency attenuates angiotensin II-induced vascular injury, M2 macrophage accumulation, and skin and heart fibrosis

MMP-12, a macrophage-secreted elastase, is elevated in fibrotic diseases, including systemic sclerosis (SSc) and correlates with vasculopathy and fibrosis. The goal of this study was to investigate the role of MMP-12 in cardiac and cutaneous fibrosis induced by angiotensin II infusion. Ang II-induced heart and skin fibrosis was accompanied by a marked increase of vascular injury markers, including vWF, Thrombospondin-1 (TSP-1) and MMP-12, as well as increased number of PDGFRβ⁺ cells. Furthermore Ang II infusion led to an accumulation of macrophages (Mac3⁺) in the skin and in the perivascular and interstitial fibrotic regions of the heart. However, alternatively activated (Arg 1⁺) macrophages were mainly present in the Ang II infused mice and were localized to the perivascular heart regions and to the skin, but were not detected in the interstitial heart regions. Elevated expression of MMP-12 was primarily found in macrophages and endothelial cells (CD31⁺) cells, but MMP-12 was not expressed in the collagen producing cells. MMP-12 deficient mice (MMP12KO) showed markedly reduced expression of vWF, TSP1, and PDGFRβ around vessels and attenuation of dermal fibrosis, as well as the perivascular fibrosis in the heart. However, MMP-12 deficiency did not affect interstitial heart fibrosis, suggesting a heterogeneous nature of the fibrotic response in the heart. Furthermore, MMP-12 deficiency almost completely prevented accumulation of Arg 1⁺ cells, whereas the number of Mac3⁺ cells was partially reduced. Moreover production of profibrotic mediators such as PDGFBB, TGFβ1 and pSMAD2 in the skin and perivascular regions of the heart was also inhibited. Together, the results of this study show a close correlation between vascular injury markers, Arg 1⁺ macrophage accumulation and fibrosis and suggest an important role of MMP-12 in regulating these processes.

Endoplasmic reticulum stress and endothelial dysfunction

Prolonged perturbation of the endoplasmic reticulum (ER) leads to ER stress and unfolded protein response (UPR) and contributes to the pathogenesis of various chronic disorders. This review focuses on the role of ER stress and UPR in endothelial cells and the relevance of these processes to vascular diseases. Chronic activation of ER stress and UPR pathways in endothelial cells leads to increased oxidative stress and inflammation and often results in cell death. Because endothelial cells play a pivotal role in maintaining vascular homeostasis, various pathological conditions interfering with this homeostasis including homocysteinemia, hyperlipidemia, high glucose, insulin resistance, disturbed blood flow, and oxidative stress can lead to endothelial dysfunction in part through the activation of ER stress. We discuss recently discovered aspects of the role of ER stress/UPR in those pathological conditions. We also summarize recent findings implicating ER stress and UPR in systemic hypertension as well as pulmonary arterial hypertension. Finally, this review will highlight a novel role of UPR mediators in the process of angiogenesis.

Abnormal amplitude and kinetics of digital postocclusive reactive hyperemia in systemic sclerosis

OBJECTIVES

Postocclusive reactive hyperemia is mediated by two major mediators: sensory nerves and endothelium-derived hyperpolarizing factors. We hypothesized that the skin microvascular response to 5 min ischemia would differ depending upon the hand location in patients with systemic sclerosis (SSc), primary Raynaud's phenomenon (PRP) and healthy controls.

METHODS

Fifteen patients with SSc, 15 sex- and age-matched patients with PRP and healthy controls were enrolled. Their right hands were subjected to 5 min ischemia followed by a postocclusive hyperemia test, with local microcirculation monitoring by laser speckle contrast imaging on the dorsal face of the hand.

RESULTS

Postocclusive reactive hyperemia was abnormal in terms of peak and area under the curve (AUC) on all fingers except the thumb in patients with SSc and PRP compared with controls. In contrast, the kinetics of the response was longer only in SSc patients, with mean (SD) time to peak on the index, middle and ring finger were respectively 72 (58), 73 (51) and 67 (47) s for SSc; 40 (20), 40 (20) and 36 (19) s for PRP; and 34 (30), 34 (30) and 29 (24) s for controls (P=0.009 for interaction).

CONCLUSIONS

We observed decreased distal digital microvascular perfusion following 5 min of ischemia in patients presenting with PRP or SSc, while the kinetics was prolonged only in SSc. A dynamic assessment of digital skin blood flow using laser speckle contrast imaging following 5 min ischemia could be used as a tool to assess microvascular abnormalities in patients with Raynaud's phenomenon secondary to SSc.

Arecoline is cytotoxic for human endothelial cells

BACKGROUND

Oral submucous fibrosis is a pre-malignant fibrotic condition caused by areca nut use and involves reduced mucosal vascularity. Arecoline is the principal areca nut alkaloid and is cytotoxic for epithelium and fibroblasts. Endothelial cell cycle arrest is reported on exposure to arecoline, as is cytotoxicity for endothelial-lung carcinoma hybrid cells. We here describe cytotoxicity for primary human endothelial cultures from seven separate donors.

MATERIALS AND METHODS

Human umbilical vein endothelial cells were exposed to increasing concentrations of arecoline and examined by: phase-contrast microscopy, haemocytometer counts, transmission electron microscopy, lactate dehydrogenase release and the methyl-thiazol-tetrazolium assay.

RESULTS

Vacuolation and detachment of endothelium were observed at and above arecoline concentrations of 333 μg/ml or more. Ultrastructural features of cellular stress were seen after 24-h treatment with 111 μg/ml arecoline and included reduced ribosomal studding of endoplasmic reticulum, increased autophagolysosomal structures, increased vacuolation and reduced mitochondrial cristae with slight swelling. Similar changes were seen at 4 h with arecoline at 333 μg/ml or above, but with more severe mitochondrial changes including increased electron density of mitochondrial matrix and greater cristal swelling, while by 24 h, these cells were frankly necrotic. Haemocytometer counts were paralleled by both lactate dehydrogenase release and the methyl-thiazol-tetrazolium assays.

CONCLUSIONS

Arecoline is cytotoxic via necrosis for endothelium, while biochemical assays indicate no appreciable cellular leakage before death and detachment, as well as no clear effect on mitochondrial function in viable cells. Arecoline toxicity may thus contribute to reduced vascularity in oral submucous fibrosis.

Fibrosis--a lethal component of systemic sclerosis

Fibrosis is a pathological process characterized by excessive accumulation of connective tissue components in an organ or tissue. Fibrosis is produced by deregulated wound healing in response to chronic tissue injury or chronic inflammation, the hallmarks of rheumatic diseases. Progressive fibrosis, which distorts tissue architecture and results in progressive loss of organ function, is now recognized to be one of the major causes of morbidity and mortality in individuals with one of the most lethal rheumatic disease, systemic sclerosis (SSc). In this Review, we discuss the pathological role of fibrosis in SSc. We discuss the involvement of endothelium and pericyte activation, aberrant immune responses, endoplasmic reticulum stress and chronic tissue injury in the initiation of fibrosis in SSc. We then discuss fibroblast activation and myofibroblast differentiation that occurs in response to these initiating processes and is responsible for excessive accumulation of extracellular matrix. Finally, we discuss the chemical and mechanical signals that drive fibroblast activation and myofibroblast differentiation, which could serve as targets for new therapies for fibrosis in SSc.

Angiotensin receptor type 1 and endothelin receptor type A on immune cells mediate migration and the expression of IL-8 and CCL18 when stimulated by autoantibodies from systemic sclerosis patients

INTRODUCTION

Agonistic autoantibodies (Aabs) against the angiotensin II receptor type 1 (AT1R) and the endothelin receptor type A (ETAR) have been identified in patients with systemic sclerosis (SSc). In our present study, we examined the expression of the AT1R and the ETAR in human immune cells and the pathological effects mediated through these receptors by their corresponding Aabs.

METHODS

Protein expression of AT1R and ETAR on peripheral blood mononuclear cells (PBMCs) from healthy individuals and SSc patients was analyzed using flow cytometry, and mRNA expression of both receptors in PBMCs from healthy donors was examined by real-time PCR. In addition, PBMCs from healthy donors were stimulated in vitro with affinity-purified immunoglobulin G (IgG) fractions from SSc patients positive for AT1R and ETAR Aabs, as well as with IgG from healthy donors serving as controls. Alterations in cell surface marker expression, cytokine secretion and chemotactic motility were analyzed using flow cytometry, enzyme-linked immunosorbent assays and chemotaxis assays, respectively. The results were correlated with the characteristics and clinical findings of the IgG donors.

RESULTS

Both AT1R and ETAR were expressed on PBMCs in humans. Protein expression of both receptors was decreased in SSc patients compared with that of healthy donors and declined during the course of disease. IgG fractions of SSc patients positive for AT1R and ETAR Aabs induced T-cell migration in an Aab level-dependent manner. Moreover, IgG of SSc patients stimulated PBMCs to produce more interleukin 8 (IL-8) and chemokine (C-C motif) ligand 18 (CCL18) than did the IgG of healthy donors. All effects were significantly reduced by selective AT1R and ETAR antagonists. Statistical analysis revealed an association of SSc-IgG induced high IL-8 concentrations with an early disease stage and of high CCL18 concentrations with lung fibrosis onset and vascular complications in the respective IgG donors.

CONCLUSION

In our present study, we could demonstrate the expression of both AT1R and ETAR on human peripheral T cells, B cells and monocytes. The decreased receptor expression in SSc patients, the inflammatory and profibrotic effects upon Aab stimulation of PBMCs in vitro and the associations with clinical findings suggest a role for Aab-induced activation of immune cells mediated by the AT1R and the ETAR in the pathogenesis or even the onset of the disease.

Oxidative stress elicits platelet/leukocyte inflammatory interactions via HMGB1: a candidate for microvessel injury in sytemic sclerosis

AIMS

An abnormal generation of reactive oxygen species (ROS) is thought to contribute to systemic sclerosis (SSc), fostering autoimmunity, fibrosis, and vascular inflammation. The function of the prototypic damage-associated molecular pattern, high mobility group box 1 (HMGB1), depends on its redox status. Here we investigate whether oxidative stress regulates the cross-talk between leukocytes and platelets via HMGB1, thus contributing to vessel inflammation in SSc.

RESULTS

The oxidation of HMGB1 amplified its ability to activate neutrophils, as detected assessing the redistribution of primary granule molecules and the transactivation of the β2 integrin chain CD18. Activated platelets are a source of bioactive HMGB1 and via P-selectin stimulated neutrophils to generate ROS. Oxidized extracellular HMGB1, soluble or associated to platelet membrane or to platelet-derived microparticles (PDμPs), further increased leukocyte activation. Leukocyte activation abated in the presence of inhibitors of HMGB1 or of catalase, which catalyzes the dismutation of hydrogen peroxide into water and molecular oxygen. The redistribution of the content of primary granules and the transactivation of β2 integrins characterized blood leukocytes of SSc patients and membrane HMGB1 was significantly higher in patients with pulmonary hypertension or with diffuse SSc. HMGB1(+) microparticles (μPs) purified from SSc patients, but not HMGB1(-) μPs purified from control subjects, activated in vitro healthy neutrophils, and HMGB1 inhibitors reversed the effects of μPs.

INNOVATION AND CONCLUSION

ROS dramatically increase the ability of extracellular HMGB1 to activate blood leukocytes. This event might contribute to maintain the microvascular injury of patients with SSc.

The profibrotic role of endothelin-1: is the door still open for the treatment of fibrotic diseases?

The endothelin (ET) system consists of two G-protein-coupled receptors (ETA and ETB), three peptide ligands (ET-1, ET-2 and ET-3), and two activating peptidases (endothelin-converting enzyme-, ECE-1 and ECE-2). While initially described as a vasoregulatory factor, shown to influence several cardiovascular diseases, from hypertension to heart failure, ET-1, the predominant form in most cells and tissues, has expanded its pathophysiological relevance by recent evidences implicating this factor in the regulation of fibrosis. In this article, we review the current knowledge of the role of ET-1 in the development of fibrosis, with particular focus on the regulation of its biosynthesis and the molecular mechanisms involved in its profibrotic actions. We summarize also the contribution of ET-1 to fibrotic disorders in several organs and tissues. The development and availability of specific ET receptor antagonists have greatly stimulated a number of clinical trials in these pathologies that unfortunately have so far given negative or inconclusive results. This review finally discusses the circumstances underlying these disappointing results, as well as provides basic and clinical researchers with arguments to keep exploring the complex physiology of ET-1 and its therapeutic potential in the process of fibrosis.

Breast cancer in systemic sclerosis: results of a cross-linkage of an Italian Rheumatologic Center and a population-based Cancer Registry and review of the literature

OBJECTIVE

Increased frequency of few types of cancer in systemic sclerosis (SSc) has been reported in the literature; in particular, breast carcinoma has been proposed as one of the most frequent malignancy in SSc patients, even though data are not univocal. The aim of the present study was to retrospectively evaluate the prevalence of breast cancer in our SSc series, compared with sex-/age-matched general population of the same geographical area, and the possible correlations with SSc features, including X-ray exposure for clinical investigations. A review of the world literature about this topic was also done.

METHODS

Clinical records of 318 consecutive SSc patients, 31 M and 287 F, age 51.5±14.5 SD years, disease duration 10±6.5 SD years, referred to our Rheumatology Unit between January 2002 and December 2012 were evaluated.

RESULTS

Twelve (3.8%) cases of breast cancer were recorded, including 11/287 females (3.8%) and 1/31 (3.2%) male patients. Considering the subgroup of 202 SSc patients resident in the Province of Modena compared with data of the local Tumor Registry, the incidence of breast cancer observed in our SSc series is significantly higher than expected (SIR 2.1; 95% interval of confidence: 1.13-3.90; p<0.01). On the whole, the comparison between SSc patients with cancer and those without did not show any significant differences with regard to SSc clinical features, including the X-ray exposure. Of note is the relatively shorter disease duration at the time of breast cancer detection (median 2.5years, range 1-21; disease duration of mean 10±6.5 SD years in the entire cohort). The review of the literature revealed that the observed incidence of breast cancer in our case series is comparable to the few studies reporting the highest percentages of this malignancy.

CONCLUSIONS

A significant increase of breast cancer incidence compared to sex-age-matched general population from the same geographic area was observed. Moreover, a close temporal relationship between SSc and breast cancer onset was found, independently from clinical, serological, and instrumental features of SSc. The possible pathogenetic link between this systemic autoimmune disease and complicating breast cancer, as well as the results of previous studies, are discussed.

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.

Interferon-γ promotes vascular remodeling in human microvascular endothelial cells by upregulating endothelin (ET)-1 and transforming growth factor (TGF) β2

Systemic sclerosis (SSc) is a complex disease characterized by vascular alterations, activation of the immune system and tissue fibrosis. Previous studies have implicated activation of the interferon pathways in the pathogenesis of SSc. The goal of this study was to determine whether interferon type I and/or type II could play a pathogenic role in SSc vasculopathy. Human dermal microvascular endothelial cells (HDMVECs) and fibroblasts were obtained from foreskins of healthy newborns. The RT Profiler PCR Array System was utilized to screen for EndoMT genes. Treatment with IFN-α or IFN-γ downregulated Fli1 and VE-cadherin. In contrast, IFN-α and IFN-γ exerted opposite effects on the expression of α-SMA, CTGF, ET-1, and TGFβ2, with IFN-α downregulating and IFN-γ upregulating this set of genes. Blockade of TGFβ signaling normalized IFN-γ-mediated changes in Fli1, VE-cadherin, CTGF, and ET-1 levels, whereas upregulation of α-SMA and TGFβ2 was not affected. Bosentan treatment was more effective than TGFβ blockade in reversing the actions of IFN-γ, including downregulation of α-SMA and TGFβ2, suggesting that activation of the ET-1 pathway plays a main role in the IFN-γ responses in HDMECs. IFN-γ induced expression of selected genes related to endothelial-to-mesenchymal transition (EndoMT), including Snail1, FN1, PAI1, TWIST1, STAT3, RGS2, and components of the WNT pathway. The effect of IFN-γ on EndoMT was mediated via TGFβ2 and ET-1 signaling pathways. This study demonstrates distinct effects of IFN-α and IFN-γ on the biology of vascular endothelial cells. IFN-γ may contribute to abnormal vascular remodeling and fibrogenesis in SSc, partially via induction of EndoMT.

Acute retinal artery occlusion in systemic sclerosis: a rare manifestation of systemic sclerosis fibroproliferative vasculopathy

OBJECTIVES

To describe three patients with systemic sclerosis (SSc) who developed acute unilateral blindness in the absence of any common etiologic factor for blindness. In one patient, the affected eye required enucleation and was examined histopathologically.

METHODS

Following identification of the first patient with retinal artery occlusion at the Scleroderma Center of Thomas Jefferson University, every patient evaluated at the Center from May 2001 to December 2010 was prospectively assessed for the development of acute unilateral blindness. Two additional cases were identified. Here, we describe the clinical features, laboratory and ancillary examinations of the three patients with SSc who developed acute unilateral blindness and present the histopathological examination of one eye enucleated from one of the patients.

RESULTS

Clinical and angiographic studies were consistent with acute retinal artery occlusion. The histopathological studies showed severe retinal ischemic atrophy and concentric narrowing and fibrosis of small retinal vessels.

CONCLUSIONS

These findings suggest that acute retinal artery occlusion in these patients is a manifestation of the fibroproliferative vasculopathy characteristic of SSc.

Angiotensin II induces skin fibrosis: a novel mouse model of dermal fibrosis

Introduction

Systemic sclerosis (SSc) is an autoimmune inflammatory disorder of unknown etiology characterized by fibrosis of the skin and internal organs. Ang II (angiotensin II), a vasoconstrictive peptide, is a well-known inducer of kidney, heart, and liver fibrosis. The goal of this study was to investigate the profibrotic potential of Ang II in the mouse skin.

Methods

Ang II was administered by subcutaneous osmotic mini pumps to C57BL/6 male mice. Collagen-content measurements were performed with Gomori Trichrome staining and hydroxyproline assay. The mRNA expression level of collagens, TGF-β1, TGF-β2, TGF-β3, CTGF, αSMA, CD3, Emr1, CD45/B220, MCP1, and FSP1 were quantified with real-time polymerase chain reaction (PCR). Immunostaining was performed for markers of inflammation and fibrosis, including, phospho-Smad2, αSMA, CD3, Mac3, CD45/B220, and CD163B. Fibrocytes were identified by double staining with CD45/FSP1 and CD45/PH4. Endothelial cells undergoing endothelial-to-mesenchymal transition (EndoMT) were identified by double staining with VE-cadherin/FSP1.

Results

Ang II-infused mice develop prominent dermal fibrosis in the area proximal to the pump, as shown by increased collagen and CTGF mRNA levels, increased hydroxyproline content, and more tightly packed collagen fibers. In addition, elevated mRNA levels of TGF-β2 and TGF-β3 along with increased expression of pSmad2 were observed in the skin of Ang II-treated mice. Dermal fibrosis was accompanied by an increased number of infiltrating fibrocytes, and an increased number of αSMA-positive cells, as well as CD163B⁺ macrophages in the upper dermis. This correlated with significantly increased mRNA levels of αSMA, Emr1, and MCP1. Infiltration of CD3-, CD45/B220-, and Mac3-positive cells was observed mainly in the hypodermis. Furthermore, an increased number of double-positive VE-cadherin/FSP1 cells were detected in the hypodermis only.

Conclusions

This work demonstrates that Ang II induces both inflammation and fibrosis in the skin via MCP1 upregulation and accumulation of activated fibroblasts. Additionally, our data suggest that populations of these fibroblasts originate from circulating blood cells. Ang II infusion via osmotic minipumps could serve as a useful mouse model of skin fibrosis to gain new insights into pathogenic mechanisms and to test new antifibrotic therapies.

The pathogenesis, diagnosis and treatment of Raynaud phenomenon

The past 10 years have seen the publication of results from several multicentre clinical trials in primary and systemic sclerosis (SSc)-related Raynaud phenomenon. The publication of these studies has occurred as a result of new insights into the pathogenesis of Raynaud phenomenon, which are directing new treatment approaches, and increased international collaboration between clinicians and scientists. Although the pathogenesis of Raynaud phenomenon is complex, abnormalities of the blood vessel wall, of neural control mechanisms and of intravascular (circulating) factors are known to interact and contribute. Key players relevant in drug development include nitric oxide, endothelin-1, alpha adrenergic receptor activation, abnormal signal transduction in vascular smooth muscle, oxidative stress and platelet activation. The main advances in diagnosis have been a clearer understanding of autoantibodies and of abnormal nailfold capillary patterns as independent predictors of SSc, and widespread use and increased availability of capillaroscopy. The ultimate aim is to translate the advances made in the pathophysiology and early diagnosis into development of treatments to prevent and reverse digital vascular dysfunction and injury. This Review provides an update of the pathogenesis, diagnosis and treatment of Raynaud phenomenon. Current and future treatment approaches are discussed, and some key unanswered questions are highlighted.

Role of endoglin in fibrosis and scleroderma

Fibrosis plays a role in many pathological conditions, among which is the autoimmune disease systemic sclerosis (SSc). SSc is characterized by fibrosis in the skin and internal organs, but the etiology remains to be elucidated. Transforming growth factor-β (TGF-β) is a key player in the fibrotic process, also in SSc. TGF-β induces the production of several components of the extracellular matrix and induces differentiation of fibroblasts to myofibroblasts, which further worsens fibrosis. Although TGF-β has been extensively investigated in fibrosis, the roles of several components of its signaling pathway are still unknown. Endoglin is a coreceptor for TGF-β and is known to modulate TGF-β signaling. Therefore, endoglin could enhance the effects of TGF-β in fibrosis or act as an inhibitor. Multiple studies have been conducted that support either hypothesis. Elucidating the exact role of endoglin in TGF-β signaling during fibrosis is important in understanding the process of fibrosis and could lead to the development of better treatments.

Vascular involvement in systemic sclerosis (scleroderma)

Systemic sclerosis (SSc) is an acquired multiorgan connective tissue disease with variable mortality and morbidity dictated by clinical subset type. The etiology of the basic disease and pathogenesis of the systemic autoimmunity, fibrosis, and fibroproliferative vasculopathy are unknown and debated. In this review, the spectrum of vascular abnormalities and the options currently available to treat the vascular manifestations of SSc are discussed. Also discussed is how the hallmark pathologies (ie, how autoimmunity, vasculopathy, and fibrosis of the disease) might be effected and interconnected with modulatory input from lysophospholipids, sphingosine 1-phosphate, and lysophosphatidic acid.

Intravenous immunoglobulin therapy in rheumatic diseases

Prepared from the collective plasma of several thousand people, therapeutic intravenous immunoglobulin (IVIg) consists mostly of human polyspecific IgG. In addition to its use in primary and secondary immune deficiencies, IVIg is used in the treatment of several rheumatic conditions, including Kawasaki disease, dermatomyositis and antineutrophil cytoplasmic antibody (ANCA)-positive vasculitis. In these diseases, IVIg therapy generally involves the use of 2 g/kg administered over either 2 or 5 consecutive days. However, dosage regimens have not been thoroughly explored, and indications for IVIg in most rheumatic diseases, such as systemic lupus erythematosus, polymyositis and catastrophic antiphospholipid syndrome, derive from its off-label usage. Randomized clinical trials are warranted to support the evidence-based use of IVIg, and to identify the ideal administration protocols to maximize the benefits of what is a limited resource. Further research to improve the therapeutic application of IVIg relies essentially on the conception of next-generation immunoglobulin preparations and optimization of combined therapies with immunomodulatory drugs and biologic agents.