Transforming growth factor-beta 1 in polymyositis and dermatomyositis correlates with fibrosis but not with mononuclear cell infiltrate

Stromal vascular fraction in the treatment of myositis

Muscle regeneration is a physiological process that converts satellite cells into mature myotubes under the influence of an inflammatory environment progressively replaced by an anti-inflammatory environment, with precise crosstalk between immune and muscular cells. If the succession of these phases is disturbed, the immune system can sometimes become auto-reactive, leading to chronic muscular inflammatory diseases, such as myositis. The triggers of these autoimmune myopathies remain mostly unknown, but the main mechanisms of pathogenesis are partially understood. They involve chronic inflammation, which could be associated with an auto-reactive immune response, and gradually with a decrease in the regenerative capacities of the muscle, leading to its degeneration, fibrosis and vascular architecture deterioration. Immunosuppressive treatments can block the first part of the process, but sometimes muscle remains weakened, or even still deteriorates, due to the exhaustion of its capacities. For patients refractory to immunosuppressive therapies, mesenchymal stem cells have shown interesting effects but their use is limited by their availability. Stromal vascular fraction, which can easily be extracted from adipose tissue, has shown good tolerance and possible therapeutic benefits in several degenerative and autoimmune diseases. However, despite the increasing use of stromal vascular fraction, the therapeutically active components within this heterogeneous cellular product are ill-defined and the mechanisms by which this therapy might be active remain insufficiently understood. We review herein the current knowledge on the mechanisms of action of stromal vascular fraction and hypothesise on how it could potentially respond to some of the unmet treatment needs of refractory myositis.

Use of Platelet-Rich Plasma Plus Suramin, an Antifibrotic Agent, to Improve Muscle Healing After Injuries

BACKGROUND

The increasing use of platelet-rich plasma (PRP) to treat muscle injuries raises concerns because transforming growth factor-beta (TGF-β) in PRP may promote fibrosis in the injured muscle and thus impair muscle regeneration.

PURPOSE

To investigate whether suramin (a TGF-β inhibitor) can reduce muscle fibrosis to improve healing of the injured muscle after PRP treatment and identify the underlying molecular mechanism.

STUDY DESIGN

Controlled laboratory study.

METHODS

Myoblasts isolated from the gastrocnemius muscle of Sprague Dawley rats were treated with PRP or PRP plus suramin. MTT assays were performed to evaluate cell viability. The expression of fibrosis-associated proteins (such as type I collagen and fibronectin), Smad2, and phosphorylated Smad2 was determined using Western blot analysis and immunofluorescent staining. An anti-TGF-β antibody was employed to verify the role of TGF-β in fibronectin expression. Gastrocnemius muscles were injured through a partial transverse incision and then treated using PRP or PRP plus suramin. Hematoxylin and eosin staining was conducted to evaluate the healing process 7 days after the injury. Immunofluorescent staining was performed to evaluate fibronectin expression. Muscle contractile properties-fast-twitch and tetanic strength-were evaluated through electric stimulation.

RESULTS

PRP plus 25 μg/mL of suramin promoted myoblast proliferation. PRP induced fibronectin expression in myoblasts, but suramin reduced this upregulation. The anti-TGF-β antibody also reduced the upregulation of fibronectin expression in the presence of PRP. The upregulation of phosphorylated Smad2 by PRP was reduced by either the anti-TGF-β antibody or suramin. In the animal study, no significant difference was discovered in muscle healing between the PRP versus PRP plus suramin groups. However, the PRP plus suramin group had reduced fibronectin expression at the injury site. Fast-twitch strength and tetanic strength were significantly higher in the injured muscle treated using PRP or PRP plus suramin.

CONCLUSION

Simultaneous PRP and suramin use reduced fibrosis in the injured muscle and promoted healing without negatively affecting the muscle's contractile properties. The underlying molecular mechanism may be associated with the phosphorylated Smad2 pathway.

CLINICAL RELEVANCE

Simultaneous PRP and suramin use may reduce muscle fibrosis without compromising muscle contractile properties and thus improve muscle healing.

T-cell transcriptomics from peripheral blood highlights differences between polymyositis and dermatomyositis patients

BACKGROUND

Polymyositis (PM) and dermatomyositis (DM) are two distinct subgroups of idiopathic inflammatory myopathies, a chronic inflammatory disorder clinically characterized by muscle weakness and inflammatory cell infiltrates in muscle tissue. In PM, a major component of inflammatory cell infiltrates is CD8+ T cells, whereas in DM, CD4+ T cells, plasmacytoid dendritic cells, and B cells predominate. In this study, with the aim to differentiate involvement of CD4+ and CD8+ T-cell subpopulations in myositis subgroups, we investigated transcriptomic profiles of T cells from peripheral blood of patients with myositis.

METHODS

Total RNA was extracted from CD4+ T cells (PM = 8 and DM = 7) and CD8+ T cells (PM = 4 and DM = 5) that were isolated from peripheral blood mononuclear cells via positive selection using microbeads. Sequencing libraries were generated using the Illumina TruSeq Stranded Total RNA Kit and sequenced on an Illumina HiSeq 2500 platform, yielding about 50 million paired-end reads per sample. Differential gene expression analyses were conducted using DESeq2.

RESULTS

In CD4+ T cells, only two genes, ANKRD55 and S100B, were expressed significantly higher in patients with PM than in patients with DM (false discovery rate [FDR] < 0.05, model adjusted for age, sex, HLA-DRB1*03 status, and RNA integrity number [RIN]). On the contrary, in CD8+ T cells, 176 genes were differentially expressed in patients with PM compared with patients with DM. Of these, 44 genes were expressed significantly higher in CD8+ T cells from patients with PM, and 132 genes were expressed significantly higher in CD8+ T cells from patients with DM (FDR < 0.05, model adjusted for age, sex, and RIN). Gene Ontology analysis showed that genes differentially expressed in CD8+ T cells are involved in lymphocyte migration and regulation of T-cell differentiation.

CONCLUSIONS

Our data strongly suggest that CD8+ T cells represent a major divergence between PM and DM patients compared with CD4+ T cells. These alterations in the gene expression in T cells from PM and DM patients might advocate for distinct immune mechanisms in these subphenotypes of myositis.

Dermatomyositis etiopathogenesis: a rebel soldier in the muscle

PURPOSE OF REVIEW

The purpose of this article is to review the etiopathogenesis of dermatomyositis, including the predisposing factors, triggers, inflammatory cells, pathways and target antigens associated with dermatomyositis.

RECENT FINDINGS

During the last few years, we have made considerable progress in unveiling the etiopathogenesis of dermatomyositis. In the first place, we have defined genes within the major histocompatibility complex locus as the greatest genetic risk factor for the disease. Second, we have demonstrated that certain environmental factors, as well as tumors, may trigger certain dermatomyositis subtypes. Moreover, we have established the importance of the interferon pathway in dermatomyositis pathogenesis compared with other myositis subtypes. But probably, the most remarkable advance has been the discovery of multiple autoantibodies that define groups of patients with characteristic clinical features, prognosis and response to treatment.

SUMMARY

Dermatomyositis cause and pathogenesis have proven to be a complex and fascinating task for the scientific community and the last decade has been full of new findings on how the disease starts and how it causes damage to different organ systems. However, we have still more questions than answers in this topic, answers that will be critical to understanding autoimmunity and finding effective therapies to dermatomyositis.

Itch in dermatomyositis: the role of increased skin interleukin-31

BACKGROUND

Interleukin (IL)-31 is implicated in pruritus associated with pruritic skin diseases like atopic dermatitis. Although pruritus is a prominent feature in dermatomyositis (DM), few studies have evaluated the pathogenesis of DM-associated itch.

OBJECTIVES

To establish the prevalence of itch in DM, and to investigate the role of IL-31 in DM-related itch.

METHODS

Pruritus and disease activity of DM were evaluated by a visual analogue scale (VAS) and the Cutaneous Disease and Activity Severity Index (CDASI), respectively. Expression of IL-31 and IL-31 receptor alpha (IL-31RA) in lesional DM, nonlesional DM and healthy control skin was evaluated by quantitative reverse-transcriptase polymerase chain reaction and immunofluorescence. Flow cytometry was performed on skin cells isolated from lesional DM skin to identify cellular sources of IL-31 in DM.

RESULTS

Among 191 patients with DM, 50·8% had moderate-to-severe itch, and itch was correlated with increased cutaneous severity (r = 0·34). In patients with itchy DM, gene expression of IL31 and IL31RA in lesional skin was upregulated compared with nonlesional skin and healthy control skin. IL31 mRNA expression positively correlated with VAS itch score (r = 0·67). On immunofluorescence, immunoreactivity for IL-31 and IL-31RA was stronger in lesional skin. Flow cytometry showed that lesional DM skin contained significantly more IL-31-producing cells, and CD4⁺ cells were the most common cell type. Lenabasum, an emerging treatment for DM, significantly downregulated IL-31 from CpG-stimulated peripheral blood mononuclear cells.

CONCLUSIONS

Increased skin IL-31 may play a role in DM-associated itch, and ongoing trials will evaluate the effects of systemic treatment on IL-31 and itch in DM.

Skeletal muscle cells actively shape (auto)immune responses

Histopathological analyses of muscle specimens from myositis patients indicate that skeletal muscle cells play an active role in the interaction with immune cells. Research over the last few decades has shown that skeletal muscle cells exhibit immunobiological properties that perfectly define them as non-professional antigen presenting cells. They are able to present antigens via major histocompatibility complex molecules, exhibit costimulatory molecules and secrete soluble molecules that actively shape the immune response in an either pro- or anti-inflammatory manner. Skeletal muscle cells regulate both innate and adaptive immune responses and are essentially involved in the pathophysiological processes of idiopathic inflammatory myopathies. Understanding the role of skeletal muscle cells might help to identify new therapeutic targets for these devastating diseases. This review summarizes the immunobiological features of skeletal muscle cells, especially in the context of idiopathic inflammatory myopathies, and discusses shortcomings and limitations in skeletal muscle related research providing potential perspectives to overcome them in the future.

Role of transforming growth factor-β in muscle damage and regeneration: focused on eccentric muscle contraction

High-intensity eccentric muscle contraction induces muscle damage. Damaged muscles recover through different processes, including degeneration, inflammation, regeneration, and fibrosis; some of these processes are mediated through the actions of cytokines. The transforming growth factor-beta (TGF-β) is one such cytokine involved in muscle recovery and repair. In this regard, TGF-β regulates the skeletal muscle inflammatory response, inhibits muscle regeneration, regulates extracellular matrix remodeling, and promotes fibrosis. Although some studies have suggested that inhibition of TGF-β after muscle damage promotes muscle regeneration and recovery, other studies have noted that TGF-β inhibition actually reduces muscle strength because it leads to incomplete muscle regeneration. Despite the importance of TGF-β in the repair of damaged muscles, most studies have focused on examining its role in muscle diseases such as chronic inflammatory diseases or Duchenne’s muscular dystrophy. Here, we have reviewed the existing literature for examining the role of TGF-β in muscle damage and regeneration after eccentric muscle contraction.

Dystrophic Cardiomyopathy: Complex Pathobiological Processes to Generate Clinical Phenotype

Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and X-linked dilated cardiomyopathy (XL-DCM) consist of a unique clinical entity, the dystrophinopathies, which are due to variable mutations in the dystrophin gene. Dilated cardiomyopathy (DCM) is a common complication of dystrophinopathies, but the onset, progression, and severity of heart disease differ among these subgroups. Extensive molecular genetic studies have been conducted to assess genotype-phenotype correlation in DMD, BMD, and XL-DCM to understand the underlying mechanisms of these diseases, but the results are not always conclusive, suggesting the involvement of complex multi-layers of pathological processes that generate the final clinical phenotype. Dystrophin protein is a part of dystrophin-glycoprotein complex (DGC) that is localized in skeletal muscles, myocardium, smooth muscles, and neuronal tissues. Diversity of cardiac phenotype in dystrophinopathies suggests multiple layers of pathogenetic mechanisms in forming dystrophic cardiomyopathy. In this review article, we review the complex molecular interactions involving the pathogenesis of dystrophic cardiomyopathy, including primary gene mutations and loss of structural integrity, secondary cellular responses, and certain epigenetic and other factors that modulate gene expressions. Involvement of epigenetic gene regulation appears to lead to specific cardiac phenotypes in dystrophic hearts.

Muscle Injuries and Repair: What's New on the Horizon!

Although we recognize the many advantages of improved musculoskeletal health, we also note that our ability to sustain this health and to maintain quality of life in an aging population is currently deficient. However, global efforts have produced numerous advances in tissue engineering and regenerative medicine that will collectively serve to fill this deficiency in the near future. The purpose of this review is to highlight our current knowledge, to outline our recent advances, and to discuss the evolving paradigms in skeletal muscle injury and repair.

Dysregulated innate immune function in the aetiopathogenesis of idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of systemic muscle conditions that are believed to be autoimmune in nature. They have distinct pathological features, but the aetiopathogenesis of each subtype remains largely unknown. Recently, there has been increased interest in the complex role the innate immune system plays in initiating and perpetuating these conditions, and how this may differ between subtypes. This article summarises the traditional paradigms of IIM pathogenesis and reviews the accumulating evidence for disturbances in innate immune processes in these rare, but debilitating chronic conditions.

Statistical insights into major human muscular diseases

Muscular diseases lead to muscle fiber degeneration, impairment of mobility, and in some cases premature death. Many of these muscular diseases are largely idiopathic. The goal of this study was to identify biomarkers based on their functional role and possible mechanisms of pathogenesis, specific to individual muscular disease. We analyzed the muscle transcriptome from five major muscular diseases: acute quadriplegic myopathy (AQM), amyotrophic lateral sclerosis (ALS), mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), dermatomyositis (DM) and polymyositis (PM) using pairwise statistical comparison to identify uniquely regulated genes in each muscular disease. The genome-wide information encoded in the transcriptome provided biomarkers and functional insights into dysregulation in each muscular disease. The analysis showed that the dysregulation of genes in forward membrane pathway, responsible for transmitting action potential from neural excitation, is unique to AQM, while the dysregulation of myofibril genes, determinant of the mechanical properties of muscle, is unique to ALS, dysregulation of ER protein processing, responsible for correct protein folding, is unique to DM, and upregulation of immune response genes is unique to PM. We have identified biomarkers specific to each muscular disease which can be used for diagnostic purposes.

Antiangiogenic VEGF isoform in inflammatory myopathies

Objective. To investigate expression of vascular endothelial growth factor (VEGF) antiangiogenic isoform A-_165b on human muscle in idiopathic inflammatory myopathies (IIM) and to compare distribution of angiogenic/antiangiogenic VEGFs, as isoforms shifts are described in other autoimmune disorders. Subjects and Methods. We analyzed VEGF-A_165b and VEGF-A by western blot and immunohistochemistry on skeletal muscle biopsies from 21 patients affected with IIM (polymyositis, dermatomyositis, and inclusion body myositis) and 6 control muscle samples. TGF-β, a prominent VEGF inductor, was analogously evaluated. Intergroup differences of western blot bands density were statistically examined. Endomysial vascularization, inflammatory score, and muscle regeneration, as pathological parameters of IIM, were quantitatively determined and their levels were confronted with VEGF expression. Results. VEGF-A_165b was significantly upregulated in IIM, as well as TGF-β. VEGF-A was diffusely expressed on unaffected myofibers, whereas regenerating/atrophic myofibres strongly reacted for both VEGF-A isoforms. Most inflammatory cells and endomysial vessels expressed both isoforms. VEGF-A_165b levels were in positive correlation to inflammatory score, endomysial vascularization, and TGF-β. Conclusions. Our findings indicate skeletal muscle expression of antiangiogenic VEGF-A_165b and preferential upregulation in IIM, suggesting that modulation of VEGF-A isoforms may occur in myositides.

Idiopathic inflammatory myopathies: pathogenic mechanisms of muscle weakness

Idiopathic inflammatory myopathies (IIMs) are a heterogenous group of complex muscle diseases of unknown etiology. These diseases are characterized by progressive muscle weakness and damage, together with involvement of other organ systems. It is generally believed that the autoimmune response (autoreactive lymphocytes and autoantibodies) to skeletal muscle-derived antigens is responsible for the muscle fiber damage and muscle weakness in this group of disorders. Therefore, most of the current therapeutic strategies are directed at either suppressing or modifying immune cell activity. Recent studies have indicated that the underlying mechanisms that mediate muscle damage and dysfunction are multiple and complex. Emerging evidence indicates that not only autoimmune responses but also innate immune and non-immune metabolic pathways contribute to disease pathogenesis. However, the relative contributions of each of these mechanisms to disease pathogenesis are currently unknown. Here we discuss some of these complex pathways, their inter-relationships and their relation to muscle damage in myositis. Understanding the relative contributions of each of these pathways to disease pathogenesis would help us to identify suitable drug targets to alleviate muscle damage and also improve muscle weakness and quality of life for patients suffering from these debilitating muscle diseases.

Phenotypes of Peripheral Blood Lymphocytes and Cytokine Expression in Polymyositis and Dermatomyositis before Treatment and after Clinical Remission

Objective

To investigate peripheral blood lymphocyte subpopulations, particularly helper T (Th) cells and cytokine expression before and after treatment in polymyositis (PM) and dermatomyositis (DM).

Patients and Methods

Ten patients with PM and 15 with DM were enrolled in this study. As a control we used 11 age-matched healthy subjects. We analyzed peripheral blood lymphocytes using flow cytometry. Serum cytokines were determined by enzyme-linked immunosorbent assay.

Results

Th2/Th1 and Th2/Th17 ratios were significantly higher in both PM and DM than in controls and this Th2-predominancy is marked in DM associated with interstitial pneumonia. IL-1β, IL-6 and TGF-β were significantly higher in both PM and DM and IL-4 showed a significant increase in DM when compared to controls. There was no significant correlation between either any lymphocyte subpopulations or serum cytokines and clinical severity markers such as the manual muscle strength test, serum creatine kinase, and the total CT score. Th2/Th17 in both PM and DM, as well as Th2/Th1 in the latter, significantly decreased after clinical remission compared with before treatment.

Conclusions

Th2-predominancy as shown by the increase in Th2/Th1 and Th2/Th17 ratios may suggest active disease in PM/DM but does not reflect clinical severity.

Biological approaches to improve skeletal muscle healing after injury and disease

Skeletal muscle injury and repair are complex processes, including well-coordinated steps of degeneration, inflammation, regeneration, and fibrosis. We have reviewed the recent literature including studies by our group that describe how to modulate the processes of skeletal muscle repair and regeneration. Antiinflammatory drugs that target cyclooxygenase-2 were found to hamper the skeletal muscle repair process. Muscle regeneration phase can be aided by growth factors, including insulin-like growth factor-1 and nerve growth factor, but these factors are typically short-lived, and thus more effective methods of delivery are needed. Skeletal muscle damage caused by traumatic injury or genetic diseases can benefit from cell therapy; however, the majority of transplanted muscle cells (myoblasts) are unable to survive the immune response and hypoxic conditions. Our group has isolated neonatal skeletal muscle derived stem cells (MDSCs) that appear to repair muscle tissue in a more effective manner than myoblasts, most likely due to their better resistance to oxidative stress. Enhancing antioxidant levels of MDSCs led to improved regenerative potential. It is becoming increasingly clear that stem cells tissue repair by direct differentiation and paracrine effects leading to neovascularization of injured site and chemoattraction of host cells. The factors invoked in paracrine action are still under investigation. Our group has found that angiotensin II receptor blocker (losartan) significantly reduces fibrotic tissue formation and improves repair of murine injured muscle. Based on these data, we have conducted a case study on two hamstring injury patients and found that losartan treatment was well tolerated and possibly improved recovery time. We believe this medication holds great promise to optimize muscle repair in humans.

Characterization of regulatory T cells in patients with dermatomyositis

The purpose of this study was to characterize regulatory T cells (T(reg)) in skin lesions and peripheral blood from patients with dermatomyositis (DM) and to determine the serum levels of regulatory cytokines in the disease. In skin biopsy specimens from patients with DM, immunohistochemistry was performed for CD4(+), CD25(+), forkhead/winged helix transcription factor (FoxP3)(+), transforming growth factor (TGF)-β(+) and interleukin (IL)-10(+) cells. Additionally, we defined the number of T(reg) subpopulations in peripheral blood by flow cytometry using monoclonal antibodies against CD4, CD25, FoxP3, CD45RO, CD95, CCR4 and CLA. The levels of TGF-β and IL-10 were also determined in serum samples from patients with DM by enzyme-linked immunosorbent assays. Controls included patients with cutaneous lupus erythematosus, psoriasis and atopic dermatitis (AD) as well as healthy donors. The frequency of FoxP3(+) cells was significantly reduced in skin lesions from patients with DM (p < 0.001) compared to psoriasis and AD. Moreover, the number of cells positive for TGF-β was lower in DM than in psoriasis and AD, while IL-10(+) cells were significantly reduced only compared to psoriasis. The number of CD4(+)CD25(++)FoxP3(+) T(reg) in the peripheral blood of patients with DM was significantly reduced compared to healthy controls (p < 0.05), whereas other cell populations showed no significant differences. Finally, TGF-β and IL-10 serum levels were significantly lower in patients with DM compared to healthy controls (p < 0.05). These data suggest that the depletion of T(reg) and their main effector cytokines in the skin and the serum of patients with DM may be an important factor in the pathogenesis of the disease.

Cytokines in idiopathic inflammatory myopathies

Recent findings suggest cytokines as important key molecules in the pathogenic mechanisms of idiopathic inflammatory myopathies, myositis. In this review, we focus on cytokines with a potential role in disease mechanisms in myositis and present some general information on individual cytokines and an updated summary from the literature concerning cytokines in these disorders. The idiopathic inflammatory myopathies is a heterogeneous group of disorders clinically characterized by symmetric proximal muscle weakness and by certain defined histolopathological findings, including inflammatory infiltrates in muscle tissue. Other prominent findings in the target tissue of these patients are defined molecular changes of blood vessels and muscle fibers, including reformation to high endothelial venule (HEV)-like blood vessels and intensive MHC class I expression in muscle fibers. The predominant clinical symptoms of muscle weakness and decreased muscle endurance are shared by all subsets of inflammatory myopathies and indicate that some pathogenic mechanisms related to muscle function may be shared by the different disease groups. Studies on cytokine gene, RNA and protein expression in muscle tissue from patients with various forms of the disease also indicate similar profiles, despite different phenotypes of the inflammatory cells present in muscle tissue from the different subsets of myositis. There is a pronounced expression of various cytokines in muscle tissue, among which the proinflammatory cytokines TNF-alpha and IL-1 are most widely explored in the inflammatory myopathies, which has made them into potential therapeutic targets. The use of targeted cytokine therapy has been successful in several other chronic inflammatory diseases and although the exact role of cytokines in chronic idiopathic inflammatory myopathies remains to be delineated their potential role as targets for new therapies in this disorder will be discussed in this review.

Interrelation of inflammation and APP in sIBM: IL-1 beta induces accumulation of beta-amyloid in skeletal muscle

Distinct interrelationships between inflammation and beta-amyloid-associated degeneration, the two major hallmarks of the skeletal muscle pathology in sporadic inclusion body myositis (sIBM), have remained elusive. Expression of markers relevant for these pathomechanisms were analysed in biopsies of sIBM, polymyositis (PM), dermatomyositis (DM), dystrophic and non-myopathic muscle as controls, and cultured human myotubes. By quantitative PCR, a higher upregulation was noted for the mRNA-expression of CXCL-9, CCL-3, CCL-4, IFN-gamma, TNF-alpha and IL-1 beta in sIBM muscle compared to PM, DM and controls. All inflammatory myopathies displayed overexpression of degeneration-associated markers, yet only in sIBM, expression of the mRNA of amyloid precursor protein (APP) significantly and consistently correlated with inflammation in the muscle and mRNA-levels of chemokines and IFN-gamma. Only in sIBM, immunohistochemical analysis revealed that inflammatory mediators including IL-1 beta co-localized to beta-amyloid depositions within myofibres. In human myotubes, exposure to IL-1 beta caused upregulation of APP with subsequent intracellular aggregation of beta-amyloid. Our data suggest that, in sIBM muscle, production of high amounts of pro-inflammatory mediators specifically induces beta-amyloid-associated degeneration. The observations may help to design targeted treatment strategies for chronic inflammatory disorders of the skeletal muscle.

Multiplex immunoassay analysis of cytokines in idiopathic inflammatory myopathy

CONTEXT

Idiopathic inflammatory myopathies (IIMs), including dermatomyositis, polymyositis, and inclusion-body myositis, can be difficult to diagnose.

OBJECTIVE

To determine if a multiplex immunoassay for markers of inflammation in muscle homogenates correlates with a diagnosis of IIM.

DESIGN

Frozen archived muscle biopsy specimens from 30 patients with IIM and 34 patients without IIM were homogenized and analyzed for cytokine content with a multiplex microbead-based immunoassay system. Analyte concentrations were normalized to total lysate protein concentration prior to comparison.

RESULTS

Two cytokines, interleukin 1ra and monocyte chemoattractant protein 1, and 1 soluble adhesion molecule, intracellular adhesion molecule 1, were found at significantly greater concentrations in muscle samples from patients with IIM. Intracellular adhesion molecule 1 levels alone were 83% sensitive and 91% specific for IIM at a cutoff of 1240 pg/mg muscle protein.

CONCLUSIONS

Immunoassays for selected inflammatory markers can serve in conjunction with histopathologic analysis as sensitive and specific tools for the diagnosis of IIM.

Transforming growth factor-beta following skeletal muscle strain injury in rats

Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine implicated in inflammatory processes, wound healing, and fibrosis. In muscle diseases (i.e., dystrophy and inflammatory myopathy) and in animal models of muscle injury (i.e., produced by cardiotoxin, laceration, and eccentric contractions), increased TGF-beta was associated with muscle fibrosis and healing. Although TGF-beta transcript abundance was increased following injury, many studies presume that TGF-beta protein was also active as evident by increases in collagen transcript abundance. The purpose was to determine whether TGF-beta protein is present and active 48 h following injury. Using female rats, muscle strains were produced by stretching (50 stretches) the plantar flexor muscles. Forty-eight hours following injury, the medial gastrocnemius was removed and compartmentalized into five equal segments. Damaged myofibers with intracellular concanavalin A staining were counted. The percentage of damaged myofibers was significantly greater in the distal-most segment. TGF-beta was assessed by using immunohistochemistry, RT-PCR, and immunoblot analysis. Immunohistochemistry revealed the presence of TGF-beta1 in areas of myofiber injury, whereas TGF-beta2 was not detected. Increases in TGF-beta1 and TGF-beta2 transcript abundance following strain injury were documented by RT-PCR analysis. Increases in TGF-beta1 and TGF-beta2 precursor abundance were observed following strain injury by using immunoblot analysis but there was no change in active TGF-beta abundance. Although there was no correlation between the amount of cellular injury and TGF-beta transcript and protein abundance, elevated levels of TGF-beta1 and TGF-beta2 precursor proteins were present in strain-injured skeletal muscles 48 h after injury.

Diagnostic protein expression in human muscle biopsies

Using immunohistochemistry in diagnosing neuromuscular diseases is meant to enhance the diagnostic yield in two ways. The first application aims at visualizing molecules which are developmentally, neurally, and/or immunologically regulated and not expressed by normal muscle. They are upregulated in pathological conditions and may help assign a given muscular biopsy to one of the main diagnostic entities (muscular dystrophies, inflammatory myopathy, neurogenic atrophy). In the past, muscle-specific molecules with a defined expression pattern during fetal myogenesis served as antigens, with the rationale that the developmental program was switched on in new fibers. Recently, myofibers in diseased muscle are thought of as targets of stimuli which are released by macrophages in muscular dystrophy, by lymphocytes in inflammatory myopathies, or by a lesioned peripheral nerve in neurogenic atrophies. This has somewhat blurred the borders between the diagnostic groups, for certain molecules, e.g. cytokines, may be upregulated after experimental necrotization, denervation, and also in inflammatory myopathies. In the second part of this review we summarise the experiences of a Centre in the North of England that specialises in the diagnosis and clinical support of patients with muscular dystrophy. Emphasis is placed on the use of protein expression to guide mutation analysis, particularly in the limb-girdle muscular dystrophies (a group of diseases that are very difficult to differentiate on clinical grounds alone). We confirm that genetic analysis is essential to corroborate the results of protein analysis in certain conditions (particularly in calpainopathy). However, we conclude that analysing biopsies for abnormal protein expression is very useful in aiding the decision between alternative diagnoses.

Transforming growth factor-beta enhances connective tissue growth factor expression in L6 rat skeletal myotubes

Transforming growth factor (TGF)-beta plays an important role in fibrosis of various organs and tissues. TGF-beta1 stimulates fibroblastic cells to form extracellular matrix (ECM), and regulates all critical events in wound healing. Connective tissue growth factor (CTGF), a TGF-beta-inducible molecule, has recently been reported to promote fibroblast proliferation, migration, adhesion and extracellular matrix formation, both in vivo and in vitro. In this study, we demonstrated that TGF-beta1 enhances CTGF mRNA and protein levels in L6 rat skeletal muscle myotubes. TGF-beta might, therefore, play a role in fibrosis of skeletal muscle by stimulating CTGF expression in the muscle tissue itself.

Muscle regeneration, inflammation, and connective tissue expansion in canine inflammatory myopathy

Inflammatory myopathies (IMs) are relatively common in dogs, and canine IMs have many similarities to human IMs. The aim of this work was to analyze aspects of the pathogenesis of canine IM with an ultimate goal of establishing canine IM as a model for human IM. Muscle biopsies from 16 dogs with a histological diagnosis of IM were analyzed to determine degree of muscle regeneration, presence of eosinophils, expression of selected cytokines and chemokines, and extent of fibrosis. Regeneration, as shown by staining for developmental myosin heavy chain, was more extensive than evidenced with hematoxylin-eosin staining in most cases of canine IM. Expression of mRNA encoding transforming growth factor-beta (TGF-beta) and eotaxin 3 was upregulated in all cases evaluated. Eosinophils were abundant in most cases, and the connective tissue was variably expanded, as demonstrated by the distribution of the ubiquitous extracellular matrix proteins collagen VI and fibrillin. The extensive regeneration demonstrates that muscle may survive this adverse environment if inflammation and fibrosis can be stopped or reduced.

The use of suramin, an antifibrotic agent, to improve muscle recovery after strain injury

BACKGROUND

Muscle strain injuries are extremely common in sports medicine. Muscle healing often is hindered by scar tissue formation after injury.

HYPOTHESIS

Suramin can prevent scar tissue formation and improve muscle healing after injury because of its ability to antagonize transforming growth factor-beta1, a fibrotic cytokine.

STUDY DESIGN

Controlled laboratory study.

MATERIALS AND METHODS

In vitro, muscle-derived fibroblasts (a potential cell source of muscle fibrosis) were incubated with suramin and/or transforming growth factor-beta1; a cell growth curve was obtained. In vivo, mouse gastrocnemius muscles were strain injured. Suramin or sham/control intramuscular injections were performed after injury at various time points. Mice were sacrificed at various time points after injury, and skeletal muscle tissue was evaluated by using histological and physiological tests. Statistical analysis was performed by using analysis of variance and Fisher tests.

RESULTS

Suramin decreased the stimulating effect of transforming growth factor-beta1 on the growth of muscle-derived fibroblasts in vitro. Significantly less fibrous scar formation was observed in suramin-treated muscles than in sham-injected muscles. The fast-twitch and tetanus strength of suramin-treated muscles was also significantly greater relative to that of control muscles.

CONCLUSIONS

Suramin blocked the stimulatory effect of transforming growth factor-beta1 on muscle-derived fibroblasts in vitro. Suramin also reduced fibrous scar formation in muscle and enhanced muscle strength in strain-injured skeletal muscle.

CLINICAL RELEVANCE

These results may facilitate the development of strategies to enhance muscle healing after injury.

Cytokines in the rheumatic diseases

Extensive data has accumulated over the last 10 to 15 years to implicate various cytokines in pathways of pathophysiology in rheumatic diseases. Abnormalities in cytokine production are not the cause of these diseases, but reflect continual production by immune and inflammatory cells. Cytokines are heterogeneous and function in an overlapping and redundant network. An important principle to emerge is that the net biologic response in a diseased organ or tissue reflects a balance between the local levels of proinflammatory and anti-inflammatory cytokines and factors. Thus, a chronic disease may result from the excess production of proinflammatory cytokines or the inadequate production of anti-inflammatory cytokines. This article summarizes the role of cytokines in rheumatic diseases by focusing on each disease and the involved pathways of pathophysiology.

Cytokines, chemokines, and cell adhesion molecules in inflammatory myopathies

The inflammatory myopathies include dermatomyositis (DM), polymyositis (PM), and sporadic inclusion-body myositis (s-IBM). In DM, the main immune effector response appears to be humoral and directed against the microvasculature, whereas in both PM and s-IBM, cytotoxic CD8+ T cells and macrophages invade and eventually destroy nonnecrotic muscle fibers expressing major histocompatibility complex class I. The need for more specific and safer therapies in inflammatory myopathies has prompted researchers to better decipher the molecular events associated with inflammation and muscle fiber loss in these diseases. The complex specific migration of leukocyte subsets to target tissues requires a coordinated series of events, namely activation of leukocytes, adhesion to the vascular endothelium, and migration. Cell adhesion molecules (CAM) and chemokines play a major role in this multistep process. In addition, cytokines by stimulating CAM expression and orchestrating T-cell differentiation also influence the immune response. This review focuses on recent advances in defining the molecular events involved in leukocyte trafficking in inflammatory myopathies. Specific topics include a concise summary of clinical features, pathological findings and immunopathology observed in inflammatory myopathies, background information about cytokines, chemokines and cell adhesion molecules, and the expression of these molecules in inflammatory myopathies.

Cytokines in juvenile dermatomyositis pathophysiology: potential and challenge

PURPOSE OF REVIEW

Cytokines are criticalmediators of the immune response. This review focuses on cytokine-specific information from children with juvenile dermatomyositis, and includes pertinent data from adults with polymyositis and dermatomyositis.

RECENT FINDINGS

Much of the new data concern the role of possible antigens and the definition of genetic control of the immune response in juvenile dermatomyositis. Gene expression profile data of DQA1*0501 (present in 85% of patients) compared with age-matched control subjects show that the initial immune response is an interferon-alpha/beta-induced cascade with secondary stimulation of interferon-gamma. Specific epitopes of group A beta-hemolytic streptococcal M protein, with sequence homology for myosin, elicit both cell-mediated cytotoxicity and tumor necrosis factor-alpha production when incubated with mononuclear cells from children with active juvenile dermatomyositis. Tumor necrosis factor-alpha synthesis is increased in juvenile dermatomyositis patients with the tumor necrosis factor-alpha-308A allele, and is associated with increased thrombospondin-1 (an antiangiogenic agent) production and small vessel occlusion in untreated juvenile dermatomyositis. Studies in adults with polymyositis and dermatomyositis implicate interleukin-1alpha, transforming growth factor-beta, and endothelial cell perturbation early in the disease course. Cultured myoblasts were found to produce interleukin-15, which impacts local T-cell activation and proliferation.

SUMMARY

The limited data suggest that a possible viral/microbial antigen may elicit an interferon-alpha/beta-induced response, and that antigenic epitopes may be shared. Increased synthesis of tumor necrosis factor-alpha, more common in juvenile dermatomyositis with the tumor necrosis factor-alpha-308A polymorphism, may augment this response and is associated with a wide range of pathologic consequences, as well as disease chronicity and calcifications. The muscle fibers themselves can regulate local inflammation by production of tumor necrosis factor-alpha, interleukin-15 and interleukin-1alpha, and transforming growth factor-beta.

Antifibrotic effects of suramin in injured skeletal muscle after laceration

Muscle injuries are very common in traumatology and sports medicine. Although muscle tissue can regenerate postinjury, the healing process is slow and often incomplete; complete recovery after skeletal muscle injury is hindered by fibrosis. Our studies have shown that decreased fibrosis could improve muscle healing. Suramin has been found to inhibit transforming growth factor (TGF)-beta1 expression by competitively binding to the growth factor receptor. We conducted a series of tests to determine the antifibrotic effects of suramin on muscle laceration injuries. Our results demonstrate that suramin (50 microg/ml) can effectively decrease fibroblast proliferation and fibrotic-protein expression (alpha-smooth muscle actin) in vitro. In vivo, direct injection of suramin (2.5 mg) into injured murine muscle resulted in effective inhibition of muscle fibrosis and enhanced muscle regeneration, which led to efficient functional muscle recovery. These results support our hypothesis that prevention of fibrosis could enhance muscle regeneration, thereby facilitating more efficient muscle healing. This study could significantly contribute to the development of strategies to promote efficient muscle healing and functional recovery.

Gene therapy and tissue engineering for sports medicine

Sports injuries usually involve tissues that display a limited capacity for healing. The treatment of sports injuries has improved over the past 10 to 20 years through sophisticated rehabilitation programs, novel operative techniques, and advances in the field of biomechanical research. Despite this considerable progress, no optimal solution has been found for treatment of various sports-related injuries, including muscle injuries, ligament and tendon ruptures, central meniscal tears, cartilage lesions, and delayed bone fracture healing. New biological approaches focus on the treatment of these injuries with growth factors to stimulate and hasten the healing process. Gene therapy using the transfer of defined genes encoding therapeutic proteins represents a promising way to efficiently deliver suitable growth factors into the injured tissue. Tissue engineering, which may eventually be combined with gene therapy, may potentially result in the creation of tissues or scaffolds for regeneration of tissue defects following trauma. In this article we will discuss why gene therapy and tissue engineering are becoming increasingly important in modern orthopaedic sports medicine practice. We then will review recent research achievements in the area of gene therapy and tissue engineering for sports-related injuries, and highlight the potential clinical applications of this technology in the treatment of patients with musculoskeletal problems following sports-related injuries.

TGF-beta 1 and IL-10 modulate IL-1 beta-induced membrane and soluble ICAM-1 in human myoblasts

We have previously shown that interleukin (IL)-1 beta and other inflammatory cytokines are able to induce the expression of membrane and soluble intercellular adhesion molecule (ICAM)-1 on human myoblasts. In this paper we found that IL-10 and transforming growth factor (TGF)-beta 1 are able to prevent IL-1 beta-induced membrane and soluble ICAM-1 protein expression on human myoblasts, with different time courses. The effect of both cytokines is associated to a reduction in ICAM-1 mRNA. Our findings suggest that IL-10 and TGF-beta 1 are able to influence the inflammatory process in muscle tissue at least in part by means of control of membrane and soluble ICAM-1.

Possible pathogenic mechanisms in inflammatory myopathies

The limitations associated with the different approaches into the pathogenesis of the IIM have resulted in incomplete knowledge of disease mechanisms in myositis. In most research, in which muscle tissue was used to study the different aspects of disease, biopsies with inflammatory infiltrates have been selected. Although inflammatory cell infiltrates are a characteristic feature of myositis, selecting patients with inflammatory cell infiltrates for investigations naturally introduces a selection bias. Only a few studies have been published on patients without inflammatory infiltrates but with muscle weakness, and few studies have included follow-up biopsies after different therapies. The heterogeneity of the population of patients with myositis is another limitation of the studies of pathogenic mechanisms. Although most studies classify patients according to the Bohan and Peter criteria [118, 119], some studies used histopathologic criteria [6], and only a few studies included characterization with myositis-specific autoantibodies. Because myositis-specific autoantibodies are often associated with certain clinical profiles, classification according to autoantibody profiles could be important to define differences in the pathogenesis of different phenotypes [3]. From available data on pathogenic mechanisms it is evident that cellular and humoral immune responses are involved in disease mechanisms of myositis, but whether there is a muscle-specific immune response cannot be answered by current studies. It is likely that other mechanisms are important for development of muscle weakness, including metabolic disturbances, and muscle weakness could be caused by different mechanisms in different IIM subsets or in patients in different phases of the disease. There could be early changes, which reversibly affect the metabolism, and later, irreversible changes, that could be dependent on muscle fiber damage and replacement of muscle tissue by connective tissue and fat. Current findings suggest that cytokines, which are produced in muscle tissue from different cell sources including inflammatory cells, endothelial cells, and muscle fibers, could affect muscle function. Careful follow-up studies, including the effect of therapies targeting different molecules on molecular expression in muscle tissue, are likely to increase our knowledge on disease mechanisms. A better understanding of which molecules and mechanisms affect muscle function is likely to lead to improved, less toxic therapies in patients with myositis. Many possible target molecules for blocking therapies, especially the proinflammatory cytokines IL-1 and TNF-alpha, have been identified and should be studied in appropriate clinical settings given the currently poor outcomes of many patients with IIM.

Differentiation of muscle-derived cells into myofibroblasts in injured skeletal muscle

Injured muscle can initiate regeneration promptly by activating myogenic cells that proliferate and differentiate into myotubes and myofibers. However, the recovery of the injured skeletal muscle often is hindered by the development of fibrosis. We hypothesized that the early-appearing myogenic cells in the injured area differentiate into myofibroblasts and eventually contribute to the development of fibrosis. To investigate this, we transplanted a genetically engineered clonal population of muscle-derived stem cells (MC13 cells) into the skeletal muscle of immunodeficient SCID mice, which were lacerated 4 weeks after transplantation. The MC13 cells regenerated numerous myofibers in the nonlacerated muscle and these myogenic cells were gradually replaced by myofibroblastic cells in the injured muscle. Our results suggest that the release of local environmental stimuli after muscle injury triggers the differentiation of myogenic cells (including MC13 cells) into fibrotic cells. These results demonstrate the potential of muscle-derived stem cells to differentiate into different lineages and illustrate the importance of controlling the local environment within the injured tissue to optimize tissue regeneration via the transplantation of stem cells.

The pathogenesis of inflammatory muscle diseases: on the cutting edge among the environment, the genetic background, the immune response and the dysregulation of apoptosis

Inflammatory muscle diseases (IMD), including dermatomyositis (DM) and polymyositis (PM), affect skeletal muscle, leading to profound tissue modification. The etiology of IMD is unknown, but multiple steps of the disease pathogenesis have been identified. The main alterations involve the immune response. Cellular infiltrates found in the muscle provide strong evidence for the involvement of a preferential immune mechanism of muscle damage. The pathologic differences found between PM and DM indicate a different role played by cell-mediated and humoral immune alterations. It is well accepted that in the pathogenetic pathway both host genes and environmental factors are involved. Apoptosis, or programmed cell death, is a complex process that plays a key role in many physiological events. It regulates the turnover of immune cells and is one of the mechanisms involved in ensuring a competent, non-autoreactive repertoire of lymphocytes. Apoptosis as a mechanism of muscle fibre death has been described in several neuromuscular disorders and muscular dystrophies, and evidence of a lack of apoptosis in IMD suggests a failure of apoptotic clearance of inflammatory cells playing a role in the maintenance of chronic cytotoxic muscle fibre damage. Most likely, the failure of apoptosis seems to be the main hallmark of the pathogenesis of IMD.

The role of cytokines, chemokines, and adhesion molecules in the pathogenesis of idiopathic inflammatory myopathies

Cytokines, chemokines, and adhesion molecules are important mediators in chronic inflammation and in immune regulation. In idiopathic inflammatory myopathies (IIM), increased expression of proinflammatory cytokines particularly interleukin (IL)-1alpha and IL-1beta, tumor necrosis factor (TNF)-alpha and macrophage inflammatory proteins (MIP)-1alpha, as well as of the inhibitory cytokines transforming growth factor (TGF)-beta was observed in muscle. There was no difference in cytokine and chemokine pattern between polymyositis, dermatomyositis, and inclusion body myositis, which could indicate that similar pathogenetic mechanisms are involved in these subsets of myositis. A prominent finding of IL-1alpha expression in endothelial cells, both in patients with active inflammation and in patients with chronic persisting muscle weakness without inflammation, makes this an interesting molecule in understanding the mechanisms for the pathogenesis of muscle weakness. Involvement of the blood vessels in the pathogenesis of myositis was further supported by increased expression of adhesion molecules and by a phenotypical expression of endothelial cells, resembling high endothelium venules in all three subsets of IIM. The molecular studies to date indicate a role of the microvessels in the pathogenesis of IIM not only in DM, as was previously suggested, but also in PM and IBM. The studies also indicate that IL-1alpha could be a target molecule for new therapeutical interventions.

Downregulation of TGF-beta1 mRNA and protein in the muscles of patients with inflammatory myopathies after treatment with high-dose intravenous immunoglobulin

We used reverse transcription-polymerase chain reaction to study the level of TGF-beta1 mRNA expression and immunocytochemistry to examine the immunoreactive TGF-beta1 in muscle biopsy specimens from five patients with dermatomyositis (DM) and five patients with inclusion body myositis (IBM) obtained before and after 3 months treatment with intravenous immunoglobulin (IVIg). At baseline, the mRNA expression of TGF-beta1 was increased up to fivefold in the muscles of DM patients compared to that of IBM patients. After IVIg, TGF-beta1 was downregulated and the TGF-beta1 mRNA decreased twofold in the muscles of patients with DM who had successfully responded to therapy, but remained unchanged in the muscles of patients with IBM who did not respond. The downregulation of TGF-beta1 in DM was associated with improvement of the muscle cytoarchitecture and reduction of the endomysial inflammation and connective tissue, suggesting that in DM the excess of TGF-beta1 may be involved in the pathogenesis of chronic inflammation, fibrosis, and accumulation of extracellular matrix proteins.

Increased expression of beta-chemokines in muscle of patients with inflammatory myopathies

Idiopathic inflammatory myopathies (IIM) are muscle diseases of autoimmune pathogenesis characterized by mononuclear cell infiltration within muscle tissue. Since immune cell homing and accumulation at the site of antigenic challenge is usually mediated by chemokines, we evaluated the expression of 2 beta-chemokines--monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1alpha (MIP-1alpha)--by immunohistochemistry and polymerase chain reaction in muscles of polymyositis, inclusion body myositis, and dermatomyositis patients, and related their expression to immunopathological alterations in muscle. MCP-1 and MIP-1alpha transcripts were detected by PCR in all IIM muscles, but not in controls. By immunohistochemistry, the chemokines were found in all IIM muscle sections located in infiltrating inflammatory cells and also in neighboring extracellular matrix. The extent to which extracellular matrix was filled by each chemokine differed in each disease. In view of the known ability of chemokines to bind extracellular matrix and their possible synthesis by extracellular matrix components, we suggest that chemokine storage in the extracellular matrix can act as a microenvironmental factor amplifying lymphocyte activation and migration, thereby maintaining the autoimmune attack against unknown muscle antigens.

TGF-beta and fibrosis

Transforming growth factor-beta (TGF-beta) isoforms are multifunctional cytokines that play a central role in wound healing and in tissue repair. TGF-beta is found in all tissues, but is particularly abundant in bone, lung, kidney and placental tissue. TGF-beta is produced by many but not all parenchymal cell types, and is also produced or released by infiltrating cells such as lymphocytes, monocytes/macrophages, and platelets. Following wounding or inflammation, all these cells are potential sources of TGF-beta. In general, the release and activation of TGF-beta stimulates the production of various extracellular matrix proteins and inhibits the degradation of these matrix proteins, although exceptions to these principles abound. These actions of TGF-beta contribute to tissue repair, which under ideal circumstances leads to the restoration of normal tissue architecture and may involve a component of tissue fibrosis. In many diseases, excessive TGF-beta contributes to a pathologic excess of tissue fibrosis that compromises normal organ function, a topic that has been the subject of numerous reviews [1-3]. In the following chapter, we will discuss the role of TGF-beta in tissue fibrosis, with particular emphasis on renal fibrosis.

Transforming growth factor-beta1 and fibrosis in congenital muscular dystrophies

We evaluated transforming growth factor-beta1 (TGF-beta1) expression in the muscle of four laminin alpha2-negative, four laminin alpha2-positive and seven partial laminin alpha2-deficient congenital muscular dystrophy (CMD) patients, and compared it to Duchenne muscular dystrophy (DMD) patients and controls. TGF-beta1 mRNA levels in skeletal muscle from laminin alpha2-negative and laminin alpha2-positive CMD patients were significantly greater than in controls (P < 0.05 and P < 0.005, respectively), while in partial laminin alpha2-deficient muscular dystrophy patients the amount was not significantly higher than in controls (P > 0.1). The TGF-beta1 values were lower than those found in DMD, although the extent of fibrosis was greater in CMD than in DMD and controls. Our findings suggest that TGF-beta1 is involved in CMD muscle fibrosis, but differently from what we observed in DMD muscles as it seems not to be the major player in connective tissue proliferation.

Effect of transforming growth factor-beta1 on interleukin-6 secretion in human myoblasts

Transforming growth factor-beta (TGF-beta) is involved in several autoimmune neurological diseases. It is still unclear whether its local action can be pro-inflammatory or anti-inflammatory in the muscle tissue, because of the few reports on this subject. We have previously shown that human myoblasts secrete interleukin-6 (IL-6) when stimulated with inflammatory cytokine such as interleukin-1beta (IL-1beta) or tumor necrosis factor alpha. In the present report, we show that TGF-beta1 can induce IL-6 production; moreover, costimulation or short term pre-incubation with TGF-beta1 increases IL-1beta effect, while a longer incubation inhibits its action.