Mast cells, extracellular matrix components, TGFbeta isoforms and TGFbeta receptor expression in labial salivary glands in systemic sclerosis

Whole phenotype of patients with systemic sclerosis and sicca manifestations: Comparison with sicca manifestations from other causes

INTRODUCTION & OBJECTIVES

This study aimed to characterize the whole phenotype of Systemic sclerosis (SSc) patients with sicca symptoms, using major salivary glands Ultrasound (SGUS) parameters, minor salivary glands biopsies (mSGB) and clinical findings, and to compare these characteristics with those from patients with Sjogren's Disease (SjD), and patients with sicca manifestations from other causes.

METHODS

Sixty SSc patients fulfilling the 2013 ACR/EULAR classification criteria and with subjective self-declared sicca symptoms were consecutively recruited and had SGUS and mSGB. Fifteen SSc patients without subjective sicca symptoms and 65 patients with sicca symptoms from other causes (including 37 SjD with no SSc).

RESULTS

SSc patients with subjective sicca symptoms had frequent objective clinical (up to 83 %), histological (44 % of Focus score≥1/ mm2) and US anomalies (63 % of OMERACT ≥2). 53 % patients without subjective clinical complaint also had abnormal objective tests, suggesting the existence of a sub clinical involvement of salivary glands in SSc. SjD-SSc patients had more severe glandular involvement as compared to patients with isolated SjD and isolated Sicca-SSc patients (70%, 48,6 % and 38% of patients with OMERACT ≥2 respectively) suggesting additive impact of both diseases on glandular physiology and structure.

CONCLUSION

SjD-SSc overlap have more severe sicca features as compared to isolated sicca-SSc and isolated SjD, suggesting a specific impact of SSc on salivary gland physiology. Further translational studies are needed to identify the underlying pathways that could serve as therapeutic targets.

Specific localization of fibroblasts at the intercalated duct in the major salivary glands of rats

OBJECTIVES

Immunohistochemical methods were employed to investigate the morphological heterogeneity and localization of fibroblasts associated with the function of major salivary glands in rats.

METHODS

Histochemical and electron microscopic observations were made in rat parotid, submandibular, and sublingual glands and pancreas. Fibroblasts were immunostained using their specific marker, 47 kDa heat shock protein (Hsp47).

RESULTS

Hsp47-immunopositive fibroblasts within the intralobular connective tissue exhibited a notably smaller size compared with the interlobular connective tissue. They were loosely distributed throughout the connective tissue. However, fibroblasts with elongated long processes were explicitly identified at the intercalated ducts in parotid, sublingual, and submandibular glands. Fibroblastic bodies and processes were tightly approximated with the basement membrane of the duct. Electron microscopy confirmed these findings, revealing a thin layer consisting of collagen fibers was found between the fibroblasts and the basement membrane. Double staining of Hsp47 and α-smooth muscle actin (αSMA) in parotid glands indicating that Hsp47-positive fibroblasts enveloped both the duct and αSMA-positive myoepithelial cells. Additionally, They projected long and thin processes longitudinally at the straight portion or circularly at the bifurcated portion of the duct. The three-dimensional reconstruction showed a frame-like structure of fibroblasts surrounding the intercalated duct with longitudinal myoepithelial cells. However, such specific localization of fibroblasts was not detected in the exocrine pancreas lacking myoepithelium.

CONCLUSIONS

Small fibroblasts with long processes connecting or overwrapping each other and thin collagen layers surround the intercalated ducts in rat major salivary glands, presumably contributing to protecting the ducts from salivary flow and myoepithelial contraction.

Salivary Biomarkers in Systemic Sclerosis Disease

Scleroderma or systemic sclerosis (SSc) is frequently detected at an advanced stage due to diagnosis difficulties. Salivary biomarkers, if existing, could be used for predictive diagnosis of this disease. Human saliva contains a large number of proteins that can be used for diagnosis and are of great potential in clinical research. The use of proteomic analysis to characterize whole saliva (WS) in SSc has gained an increasing attention in the last years and the identification of salivary proteins specific for SSc could lead to early diagnosis or new therapeutic targets. This review will present an overview about the use of WS in SSc studies. The proteomic technologies currently used for global identification of salivary proteins in SSc, as well as the advantages and limitations for the use of WS as a diagnostic tool, will be presented.

The spectrum of orofacial manifestations in systemic sclerosis: a challenging management

Systemic sclerosis (SSc) is a rare multisystem connective tissue disorder characterized by the triad fibrosis, vasculopathy and immune dysregulation. This chronic disease has a significant impact on the orofacial region that is involved in more than two-thirds of the cases. SSc patients can show a wide array of oral manifestations, which are usually associated with a severe impairment of the quality of life. They often present a decreased the salivary flow and a reduced mouth opening that contribute substantially to the worsening of the oral health status. Therefore, SSc patients require specific and multidisciplinary interventions that should be initiated as early as possible. The identification of specific radiological and clinical signs at the early stage will improve the management of such patients. This study reviews the wide spectrum of orofacial manifestations associated with SSc and suggests clues for the oral management that remains challenging.

The role of type 1 interferon in systemic sclerosis

Systemic Sclerosis (Scleroderma, SSc) is an autoimmune disease characterized by vasculopathy, inflammation, and fibrosis that can lead to loss of organ function. Type I interferons (IFNs) are family of cytokines that mitigate the deleterious effects of viral and bacterial infections in the innate immunity system. Past several years, research efforts have been focused on the role of type I IFN and IFN-inducible genes in the pathogenesis of SSc. Polymorphisms in the Interferon regulatory factor (IRF)-5, IRF7, and IRF8 are associated with SSc, Similarly, polymorphism of Signal Transducer and Activator of Transcription (STAT)-4, has been established as a genetic risk factor of SSc. IRFs and STAT4 proteins are key activators of type I IFN signaling pathways. An IFN signature (increased expression and activation of IFN-regulated genes) has been observed in the peripheral blood and skin biopsy samples of patients with SSc. Furthermore, a plasma IFN-inducible chemokine score correlated with markers of disease severity and autoantibody subtypes in SSc. In this review, we summarize our current knowledge of the role of type I IFNs and IFN-inducible genes in the pathogenesis of SSc and their potential role as biomarkers and therapeutic targets.

The development of myocardial fibrosis in transgenic mice with targeted overexpression of tumor necrosis factor requires mast cell-fibroblast interactions

BACKGROUND

Transgenic mice with cardiac-restricted overexpression of tumor necrosis factor (MHCsTNF mice) develop progressive myocardial fibrosis, diastolic dysfunction, and adverse cardiac remodeling. Insofar as tumor necrosis factor (TNF) does not directly stimulate fibroblast collagen synthesis, we asked whether TNF-induced fibrosis was mediated indirectly through interactions between mast cells and cardiac fibroblasts.

METHODS AND RESULTS

Cardiac mast cell number increased 2 to 3 fold (P<0.001) in MHCsTNF mice compared with littermate controls. Outcrossing MHCsTNF mice with mast cell-deficient (c-kit(-/-)) mice showed that the 11-fold increase (P<0.001) in collagen volume fraction in MHCsTNF/c-kit(+/-) mice was abrogated in MHCsTNF/c-kit(-/-) mice, and that the leftward shifted left ventricular pressure-volume curve in the MHCsTNF/c-kit(+/-) mice was normalized in the MHCsTNF/c-kit(-/-) hearts. Furthermore, the increase in transforming growth factor β1 and type I transforming growth factor β receptor messenger RNA levels was significantly (P=0.03, P=0.01, respectively) attenuated in MHCsTNF/c-kit(-/-) when compared with MHCsTNF/c-kit(+/-) mice. Coculture of fibroblasts with mast cells resulted in enhanced α-smooth muscle actin expression, increased proliferation and collagen messenger RNA expression, and increased contraction of 3-dimensional collagen gels in MHCsTNF fibroblasts compared with littermate fibroblasts. The effects of mast cells were abrogated by type I transforming growth factor β receptor antagonist NP-40208.

CONCLUSIONS

These results suggest that increased mast cell density with resultant mast cell-cardiac fibroblast cross-talk is required for the development of myocardial fibrosis in inflammatory cardiomyopathy. Cardiac fibroblasts exposed to sustained inflammatory signaling exhibit an increased repertoire of profibrotic phenotypic responses in response to mast cell mediators.

Tenascin-C in chronic sclerosing sialadenitis

Tenascin-C is an extracellular matrix glycoprotein that has been implicated in the development of fibrosis in certain chronic inflammatory/sclerosing conditions. This study was undertaken to expand our understanding of the processes involved in fibrosis that occurs in chronic sclerosing sialadenitis (CSS) by investigating the distribution of tenascin-C. Fifteen specimens of CSS with varying degrees of fibrosis and five normal submandibular glands were retrospectively examined immunohistochemically for the distribution of TNC. Linear deposition of TNC was found around collecting ducts in normal glands and around collecting ducts without surrounding fibrotic tissue in CSS; percentage incidences were not statistically different. In contrast, broader, band-like deposition of TNC was found in the fibrous tissue around collecting ducts in CSS with widespread degree of fibrosis compared to little or no fibrosis; the percentage incidence was statistically different. In addition, deposition of TNC was found around duct-like structures and extremely atrophic acini but, interestingly, however, was not found in fibrotic interlobular septa. The results of this investigation suggest that TNC is likely involved in the fibrosis that occurs around collecting ducts in CSS.

Platelet-derived growth factor (PDGF) isoform and PDGF receptor expression in drug-induced gingival overgrowth and hereditary gingival fibrosis

OBJECTIVE

To investigate possible associations between platelet-derived growth factor (PDGF), PDGF receptor expression and macrophages in drug-induced and hereditary gingival overgrowth.

MATERIALS AND METHODS

Tissues from patients with drug-induced gingival overgrowth (DIGO) (n = 10) and hereditary gingival fibrosis (n = 10) were studied and compared with 'control' gingiva (n = 10). Expression of PDGF and its alpha and beta receptors was investigated immunohistochemically and by RT-PCR. Macrophages were identified by immunostaining for CD68.

RESULTS

PDGF isoforms and receptors were detected in most cells within all specimens. There were no differences in the numbers of macrophages, or fibroblasts expressing PDGF or receptors, between groups. The level of PDGF expression by fibroblasts, determined by absorbance measurements, was similar between groups for PDGF A. Significantly lower levels of total PDGF and the receptors were detected in drug-induced overgrowth compared to those in hereditary fibrosis (P < 0.004) and control specimens (P < 0.034). All specimens expressed mRNA for PDGF A, PDGF B and alpha and beta receptors.

CONCLUSIONS

These data do not support a pivotal role for macrophage-derived PDGF B in the pathogenesis of DIGO. They suggest that fibroblasts in drug-induced lesions have a lowered capacity to produce, and respond to, PDGF, a property not shared by fibroblasts associated with hereditary fibrosis.

Mast cell accumulation and cytokine expression in the tight skin mouse model of scleroderma

The tight skin (Tsk) mouse develops many pathological changes seen in human scleroderma, such as increased collagen content and mast cell density. Although associations between mast cell expansion and skin fibrosis have been reported, the mechanisms underlying mast cell accumulation remain unclear. In this study, we have measured the density of skin mast cells in Tsk mice and their normal littermates (pa/pa) of 4-36 weeks of age, and in the skin heterografted between Tsk and pa/pa mice. Cytokines related to mast cell differentiation, proliferation and migration were examined by using RNase protection assays. Skin mast cell density in Tsk mice was significantly increased from 12 weeks of age, compared to that in pa/pa mice. The expression of transforming growth factor-beta1 (TGF-beta1), and to a lesser extent, stem cell factor (SCF) and interleukin-15 (IL-15) mRNA was higher in Tsk mice, compared to that in control mice. Mast cell density was unchanged in Tsk skin grafted onto pa/pa hosts, but dramatically increased in pa/pa skin grafted onto Tsk hosts. This latter mast cell hyperplasia was associated with the increases in mRNA levels of TGF-beta1, SCF and IL-15, whereas little change in cytokine levels was seen in heterografted Tsk skin. These results suggest that locally produced cytokines in Tsk skin influence mast cell accumulation in this animal model of human scleroderma.

Expression and regulation of intracellular SMAD signaling in scleroderma skin fibroblasts

OBJECTIVE

Scleroderma is characterized by excessive synthesis and accumulation of matrix proteins in lesional tissues. Transforming growth factor beta (TGFbeta) plays a central role in the pathogenesis of fibrosis by inducing and sustaining activation of fibroblasts; however, the underlying mechanisms are poorly understood. We undertook this study to examine the expression and function of SMADs, recently characterized intracellular effectors of TGFbeta signaling, in scleroderma fibroblasts.

METHODS

Primary dermal fibroblasts obtained from 14 patients with scleroderma and from 4 healthy adult volunteers were studied. Northern analysis was used to determine the expression of endogenous SMAD messenger RNA (mRNA), and Western analysis was used to determine SMAD protein expression. Intracellular compartmentalization of cellular SMAD proteins in the presence and absence of TGFbeta was studied by antibody-mediated immunofluorescence confocal microscopy. The effect of TGFbeta blockade on SMAD subcellular distribution was determined using anti-TGFbeta antibodies as well as a dominant-negative TGFbeta receptor type II (TGFbetaRII) vector to disrupt TGFbeta responses. SMAD-regulated luciferase reporter expression was examined to investigate the potential functional significance of activation and nuclear accumulation of endogenous SMADs in scleroderma fibroblasts.

RESULTS

Protein and mRNA levels of SMAD3, but not of SMAD4 or SMAD7, were variably elevated in scleroderma fibroblasts compared with those from healthy controls. In sharp contrast to control fibroblasts, which displayed predominantly cytoplasmic localization of SMAD3/4 in the absence of exogenous TGFbeta, in scleroderma fibroblasts SMAD3 and SMAD4 consistently showed elevated nuclear localization. Furthermore, phosphorylated SMAD2/3 levels were elevated and nuclear localization of phosphorylated SMAD2/3 was increased, suggesting activation of the SMAD pathway in scleroderma fibroblasts. Blockade of autocrine TGFbeta signaling with antibodies or by expression of dominant-negative TGFbetaRII failed to normalize SMAD subcellular distribution, suggesting that elevated nuclear SMAD import was due to alterations downstream of the TGFbeta receptors. The activity of a SMAD-responsive minimal promoter-reporter construct was enhanced in transiently transfected scleroderma fibroblasts.

CONCLUSION

This study is the first to demonstrate apparently ligand-independent constitutive activation of the intracellular TGFbeta/SMAD signaling axis in scleroderma fibroblasts. SMAD signaling may be a mechanism contributing to the characteristic phenotype of scleroderma fibroblasts and playing a role in the pathogenesis of fibrosis.

Fibrosis in scleroderma

The pathogenesis of fibrosis in scleroderma involves a complex set of interactions between the fibroblast and its surroundings. Multiple fibrotic pathways are activated for reasons that are not completely clear, but involve immune activation, microvascular damage, and fibroblast transformation into the myofibroblast. Differential proliferation and apoptosis preserve the myofibroblast phenotype rather that leading to a selective depletion of activated fibroblasts after an acute injury has healed. Disproportionate fibroblast activity could result from a combination of possible cellular and matrix defects that include fibrillin protein abnormalities, autoantibody formation, type II immune response, excessive endothelial reaction to injury, and excessive fibroblast response to TGF-beta. Development of therapies that are targeted to correcting these abnormalities will eventually lead to effective treatment for the fibrotic complications of scleroderma.

Salivary gland expression of transforming growth factor beta isoforms in Sjogren's syndrome and benign lymphoepithelial lesions

AIM

Transforming growth factor beta (TGF-beta) is involved in the control of autoimmune reactions, cell proliferation, and the accumulation of lymphocytes within organs. The aim of this study was to determine the expression of TGF-beta in salivary glands from patients with primary Sjogren's syndrome (SS) and benign lymphoepithelial lesions (BLEL) with emphasis on ductal epithelium.

METHODS

Immunoperoxidase staining for TGF-beta isoforms and Ki67 antigen was performed on formalin fixed sections of labial glands from patients with primary SS (n = 15) and controls (n = 5) and parotid glands reported as BLEL (n = 5) or normal (n = 5). Ductal expression of TGF-beta was quantified by absorbance measurements using image analysis. The specificity of staining was confirmed by peptide blocking studies.

RESULTS

All TGF-beta isoforms were detected within the cytoplasm of most lymphocytes, endothelial cells, and ducts in all specimens. Acinar expression was variable and weaker than that seen in ducts. Absorbance measurements revealed that the expression of all isoforms was greater in ducts within primary SS glands than in control glands. Ductal expression in control parotid glands was greater than that seen in BLEL glands, irrespective of the presence of adjacent lymphoid infiltrates. Comparisons between control specimens showed that ductal expression of all isoforms was highest in parotid glands, whereas no differences were detected between primary SS and BLEL glands. Ki67 positive lymphocytes and duct cells were mainly restricted to pathological specimens, with BLEL glands containing larger populations of positive cells than primary SS glands.

CONCLUSION

These results demonstrate complex and variable changes in ductal expression of TGF-beta in primary SS and BLEL, which may be important in the control of lymphoid infiltration and the proliferation of lymphocytes and ductal epithelium.

Serotonin mechanisms in heart valve disease I: serotonin-induced up-regulation of transforming growth factor-beta1 via G-protein signal transduction in aortic valve interstitial cells

Clinical disorders associated with increased serotonin [5-hydroxytryptamine (5-HT)] levels, such as carcinoid syndrome, and the use of serotonin agonists, such as fenfluoramine have been associated with a valvulopathy characterized by hyperplastic valvular and endocardial lesions with increased extracellular matrix. Furthermore, 5-HT has been demonstrated to up-regulate transforming growth factor (TGF)-beta in mesangial cells via G-protein signal transduction. We investigated the hypothesis that increased exposure of heart valve interstitial cells to 5-HT may result in increased TGF-beta1 expression and activity because of serotonin receptor-mediated signal transduction with activation of Galphaq, and subsequently up-regulation of phospholipase C. Thus, in the present study we performed a clinical-pathological investigation of retrieved carcinoid and normal valve cusps using immunohistochemical techniques to detect the presence of TGF-beta1 and other proteins associated with TGF-beta expression, including TGF-beta receptors I and II, latent TGF-beta-associated peptide (LAP), and alpha-smooth muscle actin. Carcinoid valve cusps demonstrated the unusual finding of widespread smooth muscle actin involving the interstitial cells in the periphery of carcinoid nodules; these same cells were also positive for LAP. Normal valve cusps were only focally positive for smooth muscle actin and LAP. In sheep aortic valve interstitial cell cultures 5-HT induced TGF-beta1 mRNA production and increased TGF-beta1 activity. 5-HT also increased collagen biosynthesis at the dosages studied. Furthermore, TGF-beta1 added to SAVIC cultures increased the production of sulfated glycan and hyaluronic acid. In addition, overexpression of Galphaq using an adenoviral expression vector for a constitutively active Galphaq mutant (Q209L-Galphaq) resulted in increased phospholipase C activity as well as up-regulation of TGF-beta expression and activity. These results strongly support the view that G-protein-related signal transduction is involved in 5-HT up-regulation of TGF-beta1. In conclusion, 5-HT-associated valve disease may be, in part, because of TGF-beta1 mechanisms.

Deficient Smad7 expression: a putative molecular defect in scleroderma

Scleroderma is a chronic systemic disease that leads to fibrosis of affected organs. Transforming growth factor (TGF) beta has been implicated in the pathogenesis of scleroderma. Smad proteins are signaling transducers downstream from TGF-beta receptors. Three families of Smads have been identified: (i) receptor-regulated Smad2 and -3 (R-Smads); (ii) common partner Smad4 (Co-Smad); and (iii) inhibitory Smad6 and -7 (I-Smads, part of a negative feedback loop). We have investigated the signaling components for the TGF-beta pathway and TGF-beta activity in scleroderma lesions in vivo and in scleroderma fibroblasts in vitro. Basal level and TGF-beta-inducible expression of Smad7 are selectively decreased, whereas Smad3 expression is increased both in scleroderma skin and in explanted scleroderma fibroblasts in culture. TGF-beta signaling events, including phosphorylation of Smad2 and -3, and transcription of the PAI-1 gene are increased in scleroderma fibroblasts, relative to normal fibroblasts. In vitro adenoviral gene transfer with Smad7 restores normal TGF-beta signaling in scleroderma fibroblasts. These results suggest that alterations in the Smad pathway, including marked Smad7 deficiency and Smad3 up-regulation, may be responsible for TGF-beta hyperresponsiveness observed in scleroderma.