Differential Effects of IL-17A and TNF-α on Osteoblastic Differentiation of Isolated Synoviocytes and on Bone Explants from Arthritis Patients

Investigation of the effect of Myricetin on Cisplatin-induced liver hepatotoxicity

OBJECTIVE

Cisplatin, a widely used anticancer agent, induces hepatotoxicity alongside organ damage. Understanding Cisplatin's toxicity mechanism and developing preventive measures are crucial. Our study explores Myricetin, a flavonoid, for its protective effects against Cisplatin-induced hepatotoxicity.

METHODS

In our study, a total of 32 Wistar albino male rats were utilized, which were categorized into four distinct groups: Control, Myricetin, Cisplatin, and Myricetin+Cisplatin. For the histological assessment of hepatic tissues, hematoxylin-eosin and periodic acid Schiff staining were employed, alongside immunohistochemical measurements of TNF-α, interleukin-17, and interleukin-6 immunoreactivity. Additionally, aspartate transaminase and alanine transaminase values were examined by biochemical analysis.

RESULTS

In the histological evaluation of the tissues, a normal healthy cell structure and a strong periodic acid Schiff (+) reaction were observed in the hepatocyte cells in the tissues of the Control and Myricetin groups, while intense eosinophilia, minimal vacuolization, congestion, and sinusoidal expansions were observed in the hematoxylin-eosin stainings, and a decrease in the positive reaction in the periodic acid Schiff staining was observed in the Cisplatin group. Consistent with these histological findings, an increase in TNF-α, interleukin-17, and interleukin-6 expressions (p<0.0001) and a concomitant increase in aspartate transaminase and alanine transaminase values were observed in the Cisplatin group. In the group protected by Myricetin, a significant improvement was observed in all these histological and biochemical values.

CONCLUSION

Cisplatin induces notable histopathological alterations in the liver. In this context, Myricetin exhibits the potential to alleviate Cisplatin-induced damage by modulating histological parameters and biochemical processes.

[IL-17A and IL-17F: from discovery to target of biologics - an illustrative example of translational research]

Interleukin (IL)-17A and then IL-17F have been discovered through their roles in chronic inflammatory diseases. These cytokines share 50% of sequence homology and bind to the same receptor made of the IL-17RA et IL-17RC chains. While they have rather similar pro-inflammatory effects, slight differences exist depending on the cell type considered or whether there is TNF or not. Indeed, there is a synergistic effect of TNF and IL-17A or IL-17F on many cell types. In addition, the interactions between immune and stromal cells also modulate their effects which vary according to stromal cell subtype. The identification of IL-17A and IL-17F roles in inflammatory diseases, as psoriasis, has led to the development of inhibitors of those cytokines. Anti-IL-17A, then anti-IL-17A/F and now anti-IL-17RA have been approved for different diseases and are particularly efficient in psoriasis. Their use is expending to other diseases like psoriatic arthritis and spondyloarthritis. Last, the recent understanding of the importance of stromal cells during chronic inflammation explains the relative inefficacy of such inhibitors in some other diseases.

Fibrotic pathways and fibroblast-like synoviocyte phenotypes in osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis, characterized by osteophyte formation, cartilage degradation, and structural and cellular alterations of the synovial membrane. Activated fibroblast-like synoviocytes (FLS) of the synovial membrane have been identified as key drivers, secreting humoral mediators that maintain inflammatory processes, proteases that cause cartilage and bone destruction, and factors that drive fibrotic processes. In normal tissue repair, fibrotic processes are terminated after the damage has been repaired. In fibrosis, tissue remodeling and wound healing are exaggerated and prolonged. Various stressors, including aging, joint instability, and inflammation, lead to structural damage of the joint and micro lesions within the synovial tissue. One result is the reduced production of synovial fluid (lubricants), which reduces the lubricity of the cartilage areas, leading to cartilage damage. In the synovial tissue, a wound-healing cascade is initiated by activating macrophages, Th2 cells, and FLS. The latter can be divided into two major populations. The destructive thymocyte differentiation antigen (THY)1─ phenotype is restricted to the synovial lining layer. In contrast, the THY1+ phenotype of the sublining layer is classified as an invasive one with immune effector function driving synovitis. The exact mechanisms involved in the transition of fibroblasts into a myofibroblast-like phenotype that drives fibrosis remain unclear. The review provides an overview of the phenotypes and spatial distribution of FLS in the synovial membrane of OA, describes the mechanisms of fibroblast into myofibroblast activation, and the metabolic alterations of myofibroblast-like cells.

Structural cell heterogeneity underlies the differential contribution of IL-17A, IL-17F and IL-23 to joint versus skin chronic inflammation

The current therapeutic strategy used in immune-mediated inflammatory diseases (IMIDs) primarily targets immune cells or associated-pathways. However, recent evidence suggests that the microenvironment modulates immune cell development and responses. During inflammation, structural cells acquire a pathogenetic phenotype and the interactions with immune cells are often greatly modified. Understanding the importance of these tissue-specific interactions may allow to explain why some biologics are effective in some IMIDs but not in others. The differential effects of interleukin (IL)-17 A, IL-17F and IL-23 in joint versus skin inflammation depends on structural cell heterogeneity. In addition, the sometimes opposite effects of immune/structural cell interactions on the production of these cytokines illustrate the importance of these cells in chronic inflammation, using the examples of rheumatoid arthritis, psoriasis and spondyloarthritis. This review describes these concepts, shows their interests through clinical observations, and finally discusses strategies to optimize therapeutic strategies.

Regulation of the mesenchymal stem cell fate by interleukin-17: Implications in osteogenic differentiation

Bone regeneration is a tightly regulated process that ensures proper repair and functionality after injury. The delicate balance between bone formation and resorption is governed by cytokines and signaling molecules released during the inflammatory response. Interleukin (IL)-17A, produced in the early phase of inflammation, influences the fate of osteoprogenitors. Due to their inherent capacity to differentiate into osteoblasts, mesenchymal stem/stromal cells (MSCs) contribute to bone healing and regeneration. This review presents an overview of IL-17A signaling and the leading cellular and molecular mechanisms by which it regulates the osteogenic differentiation of MSCs. The main findings demonstrating IL-17A’s influence on osteoblastogenesis are described. To this end, divergent information exists about the capacity of IL-17A to regulate MSCs’ osteogenic fate, depending on the tissue context and target cell type, along with contradictory findings in the same cell types. Therefore, we summarize the data showing both the pro-osteogenic and anti-osteogenic roles of IL-17, which may help in the understanding of IL-17A function in bone repair and regeneration.

Inhibition of IL-17 prevents the progression of traumatic heterotopic ossification

Traumatic heterotopic ossification (HO) is the abnormal formation of bone in soft tissues as a consequence of injury. However, the pathological mechanisms leading to traumatic HO remain unknown. Here, we report that aberrant expression of IL-17 promotes traumatic HO formation by activating β-catenin signalling in mouse model. We found that elevated IL-17 and β-catenin levels are correlated with a high degree of HO formation in specimens from patients and HO animals. We also show that IL-17 initiates and promotes HO progression in mice. Local injection of an IL-17 neutralizing antibody attenuates ectopic bone formation in a traumatic mouse model. IL-17 enhances the osteoblastic differentiation of mesenchymal stem cells (MSCs) by activating β-catenin signalling. Moreover, inhibition of IL-17R or β-catenin signalling by neutralizing antibodies or drugs prevents the osteogenic differentiation of isolated MSCs and decreases HO formation in mouse models. Together, our study identifies a novel role for active IL-17 as the inducer and promoter of ectopic bone formation and suggests that IL-17 inhibition might be a potential therapeutic target in traumatic HO.

TNFα inhibitors reduce bone loss in rheumatoid arthritis independent of clinical response by reducing osteoclast precursors and IL-20

OBJECTIVES

About half of RA patients treated with TNFα inhibitors either do not respond or lose their initial therapeutic response over time. The clinical response is measured by reduction in DAS28, which primarily reflects inflammation. However, other effects of TNFα inhibitors, such as impact on bone erosion, are not assessed by DAS28. We aimed to examine the effect of TNFα inhibitors on bone density, bone biomarkers and cytokine production in responder and non-responder patients and assessed mechanisms of action.

METHODS

BMD in the lumbar spine and femur neck of 117 RA patients was measured by DEXA scan. Bone turnover biomarkers CTX, osteoprotegerin (OPG), osteocalcin and RANKL were measured by ELISA. Levels of 16 cytokines in plasma and in tissue culture supernatants of ex vivo T cells were measured by multiplex assays and ELISA. The effect of treatment with TNFα inhibitors on blood mononuclear cell (MNC) differentiation to osteoclast precursors (OCP) was measured flow cytometry and microscopy.

RESULTS

TNFα inhibitors improved lumbar spine BMD but had modest effects on blood bone biomarkers, irrespective of patients' clinical response. Blood OCP numbers and the ability of monocytes to differentiate to OCP in vitro declined after treatment. Treatment also reduced RANK expression and IL-20 production. BMD improvement correlated with reduced levels of IL-20 in responder patients.

CONCLUSION

This study reveals that TNFα inhibitors reduce lumbar spine bone loss in RA patients irrespective of changes in DAS28. The reduction in bone loss is associated with reduction in IL-20 levels in responder patients.

Chemokine Receptor 5 Antagonism Causes Reduction in Joint Inflammation in a Collagen-Induced Arthritis Mouse Model

Rheumatoid arthritis (RA) is a chronic inflammatory disease mainly affecting the synovial joints. A highly potent antagonist of C-C chemokine receptor 5 (CCR5), maraviroc (MVC), plays an essential role in treating several infectious diseases but has not yet been evaluated for its potential effects on RA development. This study focused on evaluating the therapeutic potential of MVC on collagen-induced arthritis (CIA) in DBA/1J mice. Following CIA induction, animals were treated intraperitoneally with MVC (50 mg/kg) daily from day 21 until day 35 and evaluated for clinical score and histopathological changes in arthritic inflammation. We further investigated the effect of MVC on Th9 (IL-9, IRF-4, and GATA3) and Th17 (IL-21R, IL-17A, and RORγT) cells, TNF-α, and RANTES in CD8+ T cells in the spleen using flow cytometry. We also assessed the effect of MVC on mRNA and protein levels of IL-9, IL-17A, RORγT, and GATA3 in knee tissues using RT-PCR and western blot analysis. MVC treatment in CIA mice attenuated the clinical and histological severity of inflammatory arthritis, and it substantially decreased IL-9, IRF4, IL-21R, IL-17A, RORγT, TNF-α, and RANTES production but increased GATA3 production in CD8+ T cells. We further observed that MVC treatment decreased IL-9, IL-17A, and RORγt mRNA and protein levels and increased those of GATA3. This study elucidates the capacity of MVC to ameliorate the clinical and histological signs of CIA by reducing pro-inflammatory responses, suggesting that MVC may have novel therapeutic uses in the treatment of RA.

Local and systemic effects of IL-17 in joint inflammation: a historical perspective from discovery to targeting

The role of IL-17 in many inflammatory and autoimmune diseases is now well established, with three currently registered anti-IL-17-targeted therapies. This story has taken place over a period of 20 years and led to the demonstration that a T cell product could regulate, and often amplify, the inflammatory response. The first results described the contribution of IL-17 to local features in arthritis. Then, understanding was extended to its systemic effects, with a focus on cardiovascular aspects. This review provides a historical perspective of these discoveries focused on arthritis, which started in 1995, followed 10 years later by the description of Th17 cells. Today, IL-17 inhibitors for three chronic inflammatory diseases have been registered. More options are now being tested in ongoing and future clinical trials. Inhibitors of IL-17 family members and Th17 cells ranging from antibodies to small molecules are under active development. The identification of patients with IL-17-driven disease is a key target for the improved selection of patients expected to have a strongly positive response.

Intestinal ulcers induced by intravesical bacillus Calmette-Guérin therapy

Intravesical bacillus Calmette-Guérin (iBCG) therapy, one of the established treatments for bladder carcinoma, is known for its association with adverse events, including rheumatic manifestations. We describe the case of a 72-year-old man with synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome who developed inflammatory bowel disease unclassified after iBCG therapy for bladder carcinoma. The critical role of the IL-23/IL-17 axis in the pathogenesis IBD and all the domains of SAPHO syndrome has been reported previously. In the present case, the activation of the IL-23/IL-17 axis, probably due to the disease, could have been exacerbated by iBCG therapy, as observed in mice that received BCG immunotherapy. We suggest that patients with rheumatic diseases on iBCG therapy should be observed carefully since iBCG could be a contributing factor for autoimmune pathology including IBD.

Novel immune cell phenotypes in spondyloarthritis pathogenesis

Spondyloarthritis (SpA) is a heterogeneous group of chronic inflammatory diseases of unknown etiology. Over time, the plethora of cellular elements involved in its pathogenesis has progressively enriched together with the definition of specific cytokine pathways. Recent evidence suggests the involvement of new cellular mediators of inflammation in the pathogenesis of SpA or new subgroups of known cellular mediators. The research in this sense is ongoing, and it is clear that this challenge aimed at identifying new cellular actors involved in the perpetuation of the inflammatory process in AxSpA is not a mere academic exercise but rather aims to define a clear cellular hierarchy. Such a definition could pave the way for new targeted therapies, which could interfere with the inflammatory process and specific pathways that trigger immune system dysregulation and stromal cell activity, ultimately leading to significant control of the inflammation and new bone formation in a significant number of patients. In this review, we will describe the recent advances in terms of new cellular actors involved in the pathogenesis of SpA, focusing our attention on stromal cells and innate and adaptive immunity cells.

Ex vivo Bone Models and Their Potential in Preclinical Evaluation

PURPOSE OF REVIEW

Novel therapies for damaged and diseased bone are being developed in a preclinical testing process consisting of in vitro cell experiments followed by in vivo animal studies. The in vitro results are often not representative of the results observed in vivo. This could be caused by the complexity of the natural bone environment that is missing in vitro. Ex vivo bone explant cultures provide a model in which cells are preserved in their native three-dimensional environment. Herein, it is aimed to review the current status of bone explant culture models in relation to their potential in complementing the preclinical evaluation process with specific attention paid to the incorporation of mechanical loading within ex vivo culture systems.

RECENT FINDINGS

Bone explant cultures are often performed with physiologically less relevant bone, immature bone, and explants derived from rodents, which complicates translatability into clinical practice. Mature bone explants encounter difficulties with maintaining viability, especially in static culture. The integration of mechanical stimuli was able to extend the lifespan of explants and to induce new bone formation. Bone explant cultures provide unique platforms for bone research and mechanical loading was demonstrated to be an important component in achieving osteogenesis ex vivo. However, more research is needed to establish a representative, reliable, and reproducible bone explant culture system that includes both components of bone remodeling, i.e., formation and resorption, in order to bridge the gap between in vitro and in vivo research in preclinical testing.

Impact of chitosan membrane culture on the expression of pro- and anti-inflammatory cytokines in mesenchymal stem cells

Osteoarthritis (OA) is a chronic inflammatory joint condition caused by various inflammatory cytokines. The pro-inflammatory cytokines controlling OA include interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6 and IL-18. The anti-inflammatory cytokines include IL-4, IL-10, IL-13, leukemia inhibitory factor (LIF), glycoprotein 130 (IL6ST), TNF-α-stimulated gene 6 and transforming growth factor (TGF)-β1. Mesenchymal stem cells (MSCs) serve an anti-inflammatory role in the treatment of OA by secreting various cytokines. Previous studies demonstrated that the anti-inflammatory ability of MSCs decreased rapidly in a traditional plate culture. Maintaining the anti-inflammatory properties of MSCs in vitro remains challenging. Therefore, it is necessary to develop a more stable and efficient method to culture MSCs in vitro. Chitosan is a deacetylated derivative of chitin and is the second most abundant natural polysaccharide worldwide. The present study demonstrated that that MSCs cultured on chitosan membranes (CM) spontaneously formed multicellular spheroids. Compared with the control group without CM, the formation of multicellular spheres in the CM enhanced the anti-inflammatory properties of MSCs. Expression levels of pro- and anti-inflammatory genes mRNA and their proteins in MSCs were detected by reverse transcription-quantitative PCR, western blot analysis and immunofluorescence assay. Protein and mRNA expression levels of pro-inflammatory cytokines IL-1β, TNF-α, IL-6 and IL-18 were significantly decreased in CM-cultured MSCs compared with the control group (P<0.05). Furthermore, mRNA and protein expression levels of anti-inflammatory cytokines TGF-β1 in CM-cultured MSCs were significantly increased compared with the control group (P<0.01). These results indicated that the formation of multicellular spheroids by CM-cultured MSCs aided in maintaining anti-inflammatory effects.

Synergistic Interaction Between High Bioactive IL-17A and Joint Destruction for the Occurrence of Cardiovascular Events in Rheumatoid Arthritis

Rheumatoid arthritis (RA) remains a cause of morbidity and mortality in many patients while new treatments have changed the face of the disease. Despite the emergence of these new drugs, cardiovascular (CV) diseases remain more frequent in RA patients compared with the general population. However, predictive biomarkers of RA severity and precise guidelines to manage the CV risk in these patients are still lacking. Pro-inflammatory cytokines contribute both to RA and CV pathogenesis. Focusing on IL-17A, high levels of bioactive IL-17A were associated with destruction in RA but also during myocardial infarction. The study aimed to assess the relationship between bioactive IL-17A, destruction and the occurrence of CV events (CVE) in RA patients with a very long follow-up. Thirty-six RA patients were followed between 1970 and 2012 in Lyon, France. They were tested for bioactive IL-17A and clinical and biological characteristics were recorded at baseline. Then, the occurrence of CVE was registered during the follow-up. To study the bioactive fraction of IL-17A, the bioassay used the ability of human umbilical vein endothelial cells to produce IL-8 in presence of RA plasma samples with or without an anti-IL-17A antibody. Bioactive IL-17A level at baseline was higher in RA patients who later experienced a CVE compared to those without (0.77 vs 0.21 ng/ml, p-value = 0.0095, Mann-Whitney test) and synergized with joint destruction (p-value = 0.020, Kruskal-Wallis test). Through its effects on vessels and thrombosis, high levels of bioactive IL-17A could represent a long-term marker of CV risk.

Interleukin (IL)-17F and IL-17E are related to fibrosis and vasculopathy in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease that causes fibrosis and vasculopathy of the skin and internal organs against a background of autoimmune abnormalities. In recent years, the importance of the interleukin (IL)-17 family for inflammatory diseases has received much attention, but autoimmune diseases have not yet been fully explored. As for SSc, there is also no unified perspective on the involvement of the IL-17 family in its development, and few studies have been conducted linking IL-17F and IL-17E particularly to the disease severity. In the present study, we examined the correlation between serum IL-17F and IL-17E levels and disease severity in SSc patients. Moreover, the expression of the receptors for these cytokines, IL-17RB and IL-17RC, in skin tissues obtained by skin biopsy was examined by immunohistochemistry. Both cytokines were significantly elevated in the sera of patients with diffuse cutaneous SSc patients compared with healthy controls. Serum IL-17F levels correlated with modified Rodnan total skin thickness score, a semiquantitative measure of skin sclerosis, percent predicted forced vital capacity, percent predicted carbon monoxide lung diffusion capacity and serum levels of Krebs von den Lungen-6 and surfactant protein-D, serological markers of interstitial lung disease. Serum IL-17E levels were significantly correlated with percent predicted forced vital capacity and serum Krebs von den Lungen-6 levels. Serum levels of IL-17F and IL-17E also correlated with the prevalence of digital ulcers, and serum IL-17F levels were associated with elevated right ventricle systolic pressure values. In addition, IL-17RC and IL-17RB expression was increased in the skin tissues of diffuse cutaneous SSc patients. These results suggested that IL-17F and IL-17E could be involved in fibrosis and vasculopathy in SSc through their respective receptors in the affected organ tissues.

Targeting interleukin-17 in chronic inflammatory disease: A clinical perspective

Although many chronic inflammatory diseases share the feature of elevated IL-17 production, therapeutic targeting of IL-17 has vastly different clinical outcomes. Here the authors summarize the recent progress in understanding the protective and pathogenic role of the IL-23/IL-17 axis in preclinical models and human inflammatory diseases.

Chronic inflammatory diseases like psoriasis, Crohn’s disease (CD), multiple sclerosis (MS), rheumatoid arthritis (RA), and others are increasingly recognized as disease entities, where dysregulated cytokines contribute substantially to tissue-specific inflammation. A dysregulation in the IL-23/IL-17 axis can lead to inflammation of barrier tissues, whereas its role in internal organ inflammation remains less clear. Here we discuss the most recent developments in targeting IL-17 for the treatment of chronic inflammation in preclinical models and in patients afflicted with chronic inflammatory diseases.

Selective targeting of PI3Kδ suppresses human IL-17-producing T cells and innate-like lymphocytes and may be therapeutic for IL-17-mediated diseases

The delta isoform of phosphoinositide 3-kinase (PI3Kδ) regulates various lymphocyte functions. Considering the key pro-inflammatory role of IL-17A and IL-17F cytokines in psoriasis and spondyloarthritis (SpA), we investigated the potential of PI3Kδ blockade to suppress IL-17A, IL-17F and associated pro-inflammatory cytokines that could synergize with IL-17A and IL-17F. Using in vitro studies with primary human cells and ex vivo studies with inflamed target tissues, we assessed if seletalisib, a selective PI3Kδ inhibitor, suppresses cytokine production by T cells and innate-like lymphocytes, and if seletalisib modulates the inflammatory responses in stromal cell populations in psoriasis (human dermal fibroblasts (HDF)) and SpA (fibroblast-like synoviocytes (FLS)). In vitro, seletalisib inhibited the production of pro-inflammatory cytokines, including IL-17A and IL-17F, from peripheral blood mononuclear cells (PBMCs), T helper 17 (Th17) cells as well as γδ-T cells and mucosal-associated invariant T cells. This inhibition resulted in decreased inflammatory activation of HDF in co-culture systems. Seletalisib was also efficacious in inhibiting SpA PBMCs and synovial fluid mononuclear cells (SFMCs) from producing pro-inflammatory cytokines. Furthermore, supernatant derived from cultured seletalisib-treated Th17 cells showed reduced potency for activating inflammatory responses from cultured SpA FLS and decreased their osteogenic differentiation capacity. Finally, analysis of inflamed SpA synovial tissue biopsies revealed activation of the PI3K-Akt-mTOR pathway. We observed that ex vivo seletalisib treatment of inflamed synovial tissue reduced IL-17A and IL-17F expression. Collectively, inhibition of PI3Kδ reduces the production of pro-inflammatory cytokines from IL-17-producing adaptive and innate-like lymphocytes and thereby inhibits downstream inflammatory and tissue remodeling responses. PI3Kδ-targeting may therefore represent a novel therapeutic avenue for the treatment of IL-17-mediated chronic inflammatory diseases such as psoriasis and SpA.

Biological Factors, Metals, and Biomaterials Regulating Osteogenesis through Autophagy

Bone loss raises great concern in numerous situations, such as ageing and many diseases and in both orthopedic and dentistry fields of application, with an extensive impact on health care. Therefore, it is crucial to understand the mechanisms and the determinants that can regulate osteogenesis and ensure bone balance. Autophagy is a well conserved lysosomal degradation pathway, which is known to be highly active during differentiation and development. This review provides a revision of the literature on all the exogen factors that can modulate osteogenesis through autophagy regulation. Metal ion exposition, mechanical stimuli, and biological factors, including hormones, nutrients, and metabolic conditions, were taken into consideration for their ability to tune osteogenic differentiation through autophagy. In addition, an exhaustive overview of biomaterials, both for orthopedic and dentistry applications, enhancing osteogenesis by modulation of the autophagic process is provided as well. Already investigated conditions regulating bone regeneration via autophagy need to be better understood for finely tailoring innovative therapeutic treatments and designing novel biomaterials.

mTOR Blockade by Rapamycin in Spondyloarthritis: Impact on Inflammation and New Bone Formation in vitro and in vivo

Introduction: Spondyloarthritis (SpA) is characterized by inflammation, articular bone erosions and pathologic new bone formation. Targeting TNFα or IL-17A with current available therapies reduces inflammation in SpA, however, treatment of the bone pathology in SpA remains an unmet clinical need. Activation of the mammalian target Of rapamycin (mTOR) promotes IL-17A expression and osteogenesis. Therefore, the inhibition of mTOR (with rapamycin) could be a promising therapeutic avenue in SpA.

Objectives: To investigate the effect of blocking mTOR on inflammation, bone erosions and new bone formation in SpA.

Methods: Peripheral blood mononuclear cells (PBMCs) from patients with SpA were stimulated with anti-CD3/CD28 in the presence or absence of rapamycin and the resulting cytokine expression was assessed. Fibroblast-like synoviocytes (FLS) from SpA patients were assessed for osteogenic differentiation potential in conditions with TNFα, IL-17A, or TNFα plus IL-17A, in the presence or absence of rapamycin. HLA-B27/Huβ2m transgenic rats were immunized with low dose heat-inactivated Mycobacterium tuberculosis (M. tub), treated with 1.5 mg/kg rapamycin prophylactically or therapeutically and monitored for arthritis and spondylitis. Histology and mRNA analysis were performed after 5 weeks of treatment to assess inflammation and bone pathology.

Results:In vitro TNFα and IL-17A protein production by SpA PBMCs was inhibited in the presence of rapamycin. Rapamycin also inhibited osteogenic differentiation of human SpA FLS. Ex vivo analysis of SpA synovial biopsies indicated activation of the mTOR pathway in the synovial tissue of SpA patients. In vivo, prophylactic treatment of HLA-B27/Huβ2m transgenic rats with rapamycin significantly inhibited the development and severity of inflammation in peripheral joints and spine (arthritis and spondylitis), with histological evidence of reduced bone erosions and new bone formation around peripheral joints. In addition, therapeutic treatment with rapamycin significantly decreased severity of arthritis and spondylitis, with peripheral joint histology showing reduced inflammation, bone erosions and new bone formation. IL-17A mRNA expression was decreased in the metacarpophalangeal joints after rapamycin treatment.

Conclusion: mTOR blockade inhibits IL-17A and TNFα production by PBMCs, and osteogenic differentiation of FLS from patients with SpA in vitro. In the HLA-B27 transgenic rat model of SpA, rapamycin inhibits arthritis and spondylitis development and severity, reduces articular bone erosions, decreases pathologic new bone formation and suppresses IL-17A expression. These results may support efforts to evaluate the efficacy of targeting the mTOR pathway in SpA patients.

Monocyte chemoattractant protein‑1 promotes the proliferation, migration and differentiation potential of fibroblast‑like synoviocytes via the PI3K/P38 cellular signaling pathway

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation of the joints and joint destruction. Monocyte chemoattractant protein 1 (MCP‑1) is highly expressed in the joints of patients suffering from RA. The present study aimed to evaluate the effects of MCP‑1 on the phenotype of fibroblast‑like synoviocytes (FLSs) and their differentiation potential towards vascular endothelial cells. The expression of MCP‑1 in collagen‑induced arthritis (CIA) rats was investigated by PCR, ELISA and immunohistology. Cell proliferation induced by MCP‑1 was measured using a Cell Counting Kit‑8 (CCK‑8) and 5‑Bromo‑2‑deoxyuridine ELISA assay. In addition, the effects of MCP‑1 on the migration of FLSs was examined using a Transwell assay. Activation of PI3K and P38 were investigated by western blotting following MCP‑1 treatment. The vascular endothelial cell markers, tumor necrosis factor alpha (TNF‑α) and interleukin‑1 beta (IL‑β), were also examined by western blotting. LY294002 [PI3K inhibitor, (LY)] and SB203580 [P38 inhibitor, (SB)] were used to examine the proliferative and pro‑differentiation effect of PI3K and P38. The present findings showed that the expression level of MCP‑1 in the synovium of CIA rats was significantly higher compared with controls. The present in vitro study suggested that MCP‑1 increased the FLSs cell numbers with a maximal effect at 200 ng/ml, and induced the maximal phosphorylation of PI3K at 15 min and P38 at 30 min. In addition, MCP‑1 stimulation significantly increased the migration of FLSs. Furthermore, MCP‑1‑induced the expression of vascular endothelial growth factor and CD31 in FLSs. Suppression of PI3K and P38 was found to reduce MCP‑1 induced FLSs proliferation and migration, and decreased the expression levels of angiogenesis markers increased following MCP‑1 treatment. MCP‑1 was also found to increase the expression levels of both TNF‑α and IL‑β. Therefore, MCP‑1 could promote the proliferation and migration of FLSs, and was found to increase the expression levels of various angiogenesis markers via PI3K/P38, suggesting a role for this pathway in synovium hyperplasia in RA.

γδ T cells in rheumatic diseases: from fundamental mechanisms to autoimmunity

The innate and adaptive arms of the immune system tightly regulate immune responses in order to maintain homeostasis and host defense. The interaction between those two systems is critical in the activation and suppression of immune responses which if unchecked may lead to chronic inflammation and autoimmunity. γδ T cells are non-conventional lymphocytes, which express T cell receptor (TCR) γδ chains on their surface and straddle between innate and adaptive immunity. Recent advances in of γδ T cell biology have allowed us to expand our understanding of γδ T cell in the dysregulation of immune responses and the development of autoimmune diseases. In this review, we summarize current knowledge on γδ T cells and their roles in skin and joint inflammation as commonly observed in rheumatic diseases.

Wnt signaling: a promising target for osteoarthritis therapy

Osteoarthritis (OA) is the most common joint disease worldwide and a leading cause of disability. Characterized by degradation of articular cartilage, synovial inflammation, and changes in periarticular and subchondral bone, OA can negatively impact an individual's physical and mental well-being. Recent studies have reported several critical signaling pathways as key regulators and activators of cellular and molecular processes during OA development. Wnt signaling is one such pathway whose signaling molecules and regulators were shown to be abnormally activated or suppressed. As such, agonists and antagonists of those molecules are potential candidates for OA treatment. Notably, a recent phase I clinical trial (NCT02095548) demonstrated the potential of SM04690, a small-molecule inhibitor of the Wnt signaling pathway, as a disease-modifying oseoarthritis drug (DMOAD). This review summarizes the role and mechanism of Wnt signaling and related molecules in regulating OA progression, with a view to accelerating the translation of such evidence into the development of strategies for OA treatment, particularly with respect to potential applications of molecules targeting the Wnt signaling pathway.

Additive or Synergistic Interactions Between IL-17A or IL-17F and TNF or IL-1β Depend on the Cell Type

Background: IL-17A has effects on several cell types and is a therapeutic target in several inflammatory diseases. IL-17F shares 50% homology and biological activities with IL-17A. It is now of interest to target both cytokines. The objective was to compare the IL-17A and IL-17F effect on cytokine production by RA synoviocytes, and to extend to other cells.

Methods: Cells (RA synoviocytes, psoriasis skin fibroblasts, endothelial cells, myoblasts, and hepatocytes) were cultured in the presence or not of: IL-17A, IL-17F, TNF, IL-1β alone or their combinations, IL-17A/TNF, IL-17A/IL-1β, IL-17A/TNF/IL-1β, IL-17F/TNF, IL-17F/IL-1β, and IL-17F/TNF/IL-1β. All experiments were performed in parallel to reduce variability. After 48 h, supernatants were recovered and IL-6 and IL-8 levels were measured by ELISA.

Results: IL-17A and IL-17F alone increased significantly IL-6 and IL-8 productions by synoviocytes, with a stronger effect for IL-17A. For IL-6 production, TNF or IL-1β alone had the largest effect on myoblasts (5-fold increase), while for IL-8 production, it was on skin fibroblasts (5-fold increase). The IL-17A/TNF synergistic increase was observed on all cells for IL-6; and for IL-8, except for endothelial cells. For IL-17F/TNF, except with endothelial cells, a synergistic effect was also observed, but less powerful than with IL-17A/TNF. IL-17A/IL-1β or IL-17F/IL-1β effect was cell-type dependent, with an additive effect for synoviocytes (1.6 and 2-fold increase, respectively for IL-6, and 1.8 and 2-fold increase, respectively for IL-8) and a synergistic effect for hepatocytes (3.8 and 4.2-fold increase, respectively for IL-6, and 6 and 2-fold increase, respectively for IL-8). The three-cytokine combination induced an additive effect for synoviocytes and a synergistic effect for skin fibroblasts.

Conclusion: IL-17A and IL-17F acted similarly by inducing pro-inflammatory cytokine secretion, with a stronger response intensity with IL-17A. Their activities were potentiated by the combination with TNF and IL-1β, with an effect dependent on the cell type.

Activation of the Peroxisome Proliferator-Activated Receptor γ Coactivator 1β/NFATc1 Pathway in Circulating Osteoclast Precursors Associated With Bone Destruction in Rheumatoid Arthritis

Objective

Activation of osteoclastogenesis at the bone site in rheumatoid arthritis (RA) is well established. The mechanisms by which circulating osteoclast precursors contribute are still unclear. Peroxisome proliferator–activated receptor γ coactivator 1β (PGC‐1β) is implicated in transcriptional regulation of osteoclastogenesis in mouse models. This study was undertaken to investigate the contribution of PGC‐1β to circulating osteoclast precursors and its link to bone destruction in RA.

Methods

PGC‐1β expression in RA peripheral blood CD14+ monocytes was increased and showed correlation with joint destruction shown on radiographs. Cells from RA patients or healthy controls were transfected with a lentivirus vector for PGC‐1β gene silencing or overexpression and cultured with macrophage colony‐stimulating factor and RANKL. Bone resorption activity, bone‐degrading enzymes, and signaling molecules were measured in these mature osteoclasts.

Results

Increased nuclear accumulation of PGC‐1β was observed in RA peripheral blood CD14+ monocytes, and these cells had stronger osteoclastogenesis than in healthy controls. PGC‐1β protein expression was positively correlated with radiographic joint destruction (r = 0.396–0.413; all P < 0.05). PGC‐1β knockdown suppressed (51–82% reduction) the expression of cathepsin K, tartrate‐resistant acid phosphatase (TRAP), and matrix metalloproteinase 9 (MMP‐9), as well as osteoclast differentiation and bone resorption activity. Conversely, PGC‐1β overexpression increased these markers (by 1.5–1.8‐fold) and osteoclastogenesis. VIVIT, an inhibitor of NFATc1 activation, inhibited the effect of overexpressed PGC‐1β by reducing cathepsin K, TRAP, and MMP‐9 expression. Chromatin immunoprecipitation assay and dual‐luciferase reporter gene assay showed PGC‐1β bound to NFATc1 promoter, leading to transcriptional activation.

Conclusion

Activation of the PGC‐1β/NFATc1 pathway in circulating osteoclast precursors was associated with bone destruction in RA. This may represent a new treatment target.

IL-17 in Rheumatoid Arthritis and Precision Medicine: From Synovitis Expression to Circulating Bioactive Levels

Interleukin (IL)-17A has a direct contribution in early induction and late chronic stages of various inflammatory diseases. In vitro and in vivo experiments have first characterized its local effects on different cell types and then its systemic effects. For instance, IL-17 axis is now identified as a key driver of psoriasis through its effects on keratinocytes. Similar observations apply for rheumatoid arthritis (RA) where IL-17A triggers changes in the synovium that lead to synovitis and maintain local inflammation. These results have prompted the development of biologics to target this cytokine. However, while convincing studies are reported on the efficacy of IL-17 inhibitors in psoriasis, there are conflicting results in RA. Patient heterogeneity but also the involvement of mediators that regulate IL-17 function may explain these results. Therefore, new tools and concepts are required to identify patients that could benefit from these IL-17 targeted therapies in RA and the development of predictive biomarkers of response has started with the emergence of various bioassays. Current strategies are also focusing on synovial biopsies that may be used to stratify patients. From local to systemic levels, new approaches are developing and move the field of RA management into the era of precision medicine.

IL-17 and IL-17-producing cells and liver diseases, with focus on autoimmune liver diseases

The pro-inflammatory cytokine interleukin(IL)-17 and IL-17-producing cells are important players in the pathogenesis of many autoimmune / inflammatory diseases. More recently, they have been associated with liver diseases. This review first describes the general knowledge on IL-17 and IL-17 producing cells. The second part describes the in vitro and in vivo effects of IL-17 on liver cells and the contribution of IL-17 producing cells to liver diseases. IL-17 induces immune cell infiltration and liver damage driving to hepatic inflammation and fibrosis and contributes to autoimmune liver diseases. The circulating levels of IL-17 and the frequency of IL-17-producing cells are elevated in a variety of acute and chronic liver diseases. The last part focuses on the effects of IL-17 deletion or neutralization in various murine models. Some of these observed beneficial effects suggest that targeting the IL-17 axis could be a new therapeutic strategy to prevent chronicity and progression of various liver diseases.

Inflammation in bone physiology and pathology

PURPOSE OF REVIEW

Bone is constantly being remodeled throughout adult life through constant anabolic and catabolic actions that maintain tissue homeostasis. A number of hormones, cytokines growth factors, and the proximity of various cells to bone surfaces influence this process. Inflammatory changes at the bone microenvironment result in alterations leading to both excessive bone loss and bone formation. Detailed understanding of the physiological and pathological mechanisms that dictate these changes will allow us to harness inflammatory signals in bone regeneration.

RECENT FINDINGS

Recent reports have suggested that inflammatory signals are able to stimulate transcription factors that regulate osteoblast differentiation from their precursors.

SUMMARY

In this review, we summarized current understanding of the roles of inflammation in bone resorption and bone formation, which give rise to different disorders and discuss the huge potential of harnessing these inflammatory signals to achieve bone regeneration.

Synergistic effect of interleukin-17 and tumour necrosis factor-α on inflammatory response in hepatocytes through interleukin-6-dependent and independent pathways

The proinflammatory cytokines interleukin (IL)-17 and tumour necrosis factor (TNF)-α are targets for treatment in many chronic inflammatory diseases. Here, we examined their role in liver inflammatory response compared to that of IL-6. Human hepatoma cells (HepaRG, Huh7.5 and HepG2 cells) and primary human hepatocytes (PHH) were cultured with IL-6, IL-17 and/or TNF-α. To determine the contribution of the IL-6 pathway in the IL-17/TNF-α-mediated effect, an anti-IL-6 receptor antibody was used. IL-17 and TNF-α increased in synergy IL-6 secretion by HepaRG cells and PHH but not by Huh7.5 and HepG2 cells. This IL-17/TNF-α synergistic cooperation enhanced the levels of C-reactive protein (CRP) and aspartate aminotransferase (ASAT) in HepaRG cell and PHH cultures through the induction of IL-6. IL-17/TNF-α also up-regulated IL-8, monocyte chemoattractant protein (MCP)-1 and chemokine (C-C motif) ligand 20 (CCL20) chemokines in synergy through an IL-6-independent pathway. Interestingly, first exposure to IL-17, but not to TNF-α, was crucial for the initiation of the IL-17/TNF-α synergistic effect on IL-6 and IL-8 production. In HepaRG cells, IL-17 enhanced IL-6 mRNA stability resulting in increased IL-6 protein levels. The IL-17A/TNF-α synergistic effect on IL-6 and IL-8 induction was mediated through the activation of extracellular signal-regulated kinase (ERK)-mitogen-activated protein kinase, nuclear factor-κB and/or protein kinase B (Akt)-phosphatidylinositol 3-kinase signalling pathways. Therefore, the IL-17/TNF-α synergistic interaction mediates systemic inflammation and cell damage in hepatocytes mainly through IL-6 for CRP and ASAT induction. Independently of IL-6, the IL-17A/TNF-α combination may also induce immune cell recruitment by chemokine up-regulation. IL-17 and/or TNF-α neutralization can be a promising therapeutic strategy to control both systemic inflammation and liver cell attraction.

Novel Ex Vivo Human Osteochondral Explant Model of Knee and Spine Osteoarthritis Enables Assessment of Inflammatory and Drug Treatment Responses

Osteoarthritis of the knee and spine is highly prevalent in modern society, yet a disease-modifying pharmacological treatment remains an unmet clinical need. A major challenge for drug development includes selection of appropriate preclinical models that accurately reflect clinical phenotypes of human disease. The aim of this study was to establish an ex vivo explant model of human knee and spine osteoarthritis that enables assessment of osteochondral tissue responses to inflammation and drug treatment. Equal-sized osteochondral fragments from knee and facet joints (both n = 6) were subjected to explant culture for 7 days in the presence of a toll-like receptor 4 (TLR4) agonist and an inhibitor of transforming growth factor-beta (TGF-β) receptor type I signaling. Markers of inflammation, interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1), but not bone metabolism (pro-collagen-I) were significantly increased by treatment with TLR4 agonist. Targeting of TGF-β signaling resulted in a strong reduction of pro-collagen-I and significantly decreased IL-6 levels. MCP-1 secretion was increased, revealing a regulatory feedback mechanism between TGF-β and MCP-1 in joint tissues. These findings demonstrate proof-of-concept and feasibility of explant culture of human osteochondral specimens as a preclinical disease model, which might aid in definition and validation of disease-modifying drug targets.

[Research progress on protease-activated receptor 2 in pathogenesis of osteoarthritis]

Objective

To review the research progress on protease-activated receptor 2 (PAR-2) in the pathogenesis of osteoarthritis (OA).

Methods

The relevant literature about the mechanism of PAR-2 in the occurrence and development of OA in recent years was extensively reviewed and comprehensively analyzed.

Results

Abnormal activation of PAR-2 plays an important role in responses to occurrence and development of OA. Through regulating production and releasing of a variety of cytokines (such as inflammatory factors, metabolic factors, pain factors, etc.), the PAR-2 can involve in pathophysiological progression of OA articular cartilage, subchondral bone, and synovial membrane, as well as occurrence and transmission of pain.

Conclusion

PAR-2 participation in the development of OA has been confirmed. However, since PAR-2 is complicated and widespread, it is necessary to study the specific role of PAR-2 and the interaction between various signal pathways in the progression of OA, and to elucidate the potential pathophysiological mechanisms of PAR-2 participating in the process of OA, in the hope of exploring the new targets for the effective control of OA.

Wnt5a induces catabolic signaling and matrix metalloproteinase production in human articular chondrocytes

OBJECTIVE

Aberrant Wnt signaling may contribute to osteoarthritis (OA) but the Wnt family members involved have not been fully identified. The purpose of this study was to investigate the role of Wnt5a as a potential mediator of cartilage destruction in OA.

DESIGN

Immunohistochemistry to detect Wnt5a was performed using normal and OA human articular cartilage. Cultured normal human chondrocytes were treated with fibronectin fragments (FN-f) as a catabolic stimulus or recombinant Wnt5a protein with or without pretreatment using a panel of signaling inhibitors. Expression of Wnt5a, anabolic genes and catabolic genes were determined by quantitative real-time PCR. Production of Wnt5a protein and matrix metalloproteinases (MMPs) as well as activation of signaling proteins were analyzed by immunoblotting.

RESULTS

Wnt5a was present in human articular cartilage with OA changes and its expression and secretion were increased in FN-f stimulated chondrocytes. FN-f stimulated Wnt5a production through the c-Jun N-terminal kinase (JNK) and extracellular signal-related kinase (ERK) pathways. Wnt5a reduced aggrecan gene expression after 48 h of treatment. Wnt5a seemed to promote MMP1, -3, and -13 expression as well as MMP1 and MMP13 protein production in normal human chondrocytes. Wnt5a inhibitor peptides did not affect FN-f induced MMP production. Wnt5a activated β-catenin independent signaling including calmodulin-dependent protein kinase II (CaMKII), JNK, p38, ERK1/2, p65 and Akt. Inhibition of JNK, p38, ERK, PI-3 kinase and CaMKII by specific signaling inhibitors suppressed Wnt5a mediated MMP1 and MMP13 production.

CONCLUSIONS

Wnt5a is present in human OA cartilage and can promote chondrocyte catabolic activity through non-canonical Wnt signaling, which suggests a potential role in OA.

IL-17A Inhibits Osteogenic Differentiation of Bone Mesenchymal Stem Cells via Wnt Signaling Pathway

Background

Interleukin-17A (IL-17A) is not only an important modulator of inflammatory reactions, but also affects bone metabolism, which is involved in osteogenic differentiation of stem cells. However, the role and mechanism of IL-17A in osteogenic differentiation of bone mesenchymal stem cells (BMSCs) are not fully understood. In this study, we investigated the role and mechanism of IL-17A in osteogenic differentiation of BMSCs.

Material/Methods

The osteogenic differentiation of BMSCs was induced by osteoblast-induction medium with IL-17A or without IL-17A. The osteogenic differentiation of BMSCs was confirmed by the alkaline phosphatase and alizarin red staining. The lentiviral plasmid was used to construct the sFRP1-shRNA expression vector. The associated osteogenic differentiation marks (RUNX2, ALP, OPN), Wnt signaling pathway inhibitor (sFRP1), and modulators of Wnt signaling pathway (Wnt3, Wnt6) were detected by qRT-PCR and Western blot method.

Results

The results showed that the addition of IL-17A inhibited osteogenic differentiation of BMSCs. IL-17A induced up-regulated expression of sFRP1 and down-regulated expression of Wnt3 and Wnt6 in BMSCs. In addition, sFRP1-shRNA abolished the inhibition effect of IL-17A in osteogenic differentiation of BMSCs and induced up-regulated expression of Wnt3 and Wnt6 in the Wnt signaling pathway in BMSCs.

Conclusions

Our findings show that IL-17A inhibits osteogenic differentiation of bone mesenchymal stem cells via the Wnt signaling pathway.

Increased sensitivity of rheumatoid synoviocytes to Schnurri-3 expression in TNF-α and IL-17A induced osteoblastic differentiation

OBJECTIVE

To compare the effects of TNF-α and IL-17A on osteogenic differentiation of isolated fibroblast-like synoviocytes (FLS) from healthy donors, osteoarthritis (OA) and rheumatoid arthritis (RA) patients.

METHODS

FLS were cultured in osteogenic medium, with and without TNF-α and/or IL-17A. Extracellular matrix mineralization was evaluated by alizarin red staining and alkaline phosphatase activity (ALP) measurement. mRNA expression was analyzed by qRT-PCR for Wnt5a, BMP2 and Runx2, genes associated with osteogenesis, for DKK1 and RANKL, genes associated with osteogenesis inhibition and Schnurri-3, a new critical gene in the cross talk with osteoclasts. IL-6 and IL-8 production was measured by ELISA.

RESULTS

In osteogenic medium, matrix mineralization and increased ALP activity indicated that FLS can undergo osteogenic differentiation, which was increased with TNF-α and IL-17A. The expression of osteogenesis activators (BMP2 and Wnt5a) was increased with cytokines and that of the osteogenesis inhibitor DKK1 was decreased. There was no difference between all three cell types. In contrast, RA FLS were particularly sensitive to the synergistic increase of Shn3 with TNF-α and IL-17A. Levels of IL-6 and IL-8 were also higher for RA-FLS, compared to healthy and OA FLS.

CONCLUSION

IL-17A and/or TNF-α treatment favor an osteogenesis induction in isolated FLS, independent of their origin. RA-FLS were more sensitive to the synergistic increase of Schnurri-3 expression. Combined with the higher levels of inflammation, this may in turn activate osteoclastogenesis, leading to increased bone destruction seen in destructive arthritis.

Evaluation of the anti-inflammatory effects of two platelet-rich gel supernatants in an in vitro system of cartilage inflammation

OBJECTIVES

To study, in normal cartilage explants (CEs) challenged with lipopolysaccharide (LPS), the temporal effects (at 48 and 96h) of leukocyte- and platelet-rich gel (L-PRG) and pure platelet-rich gel (P-PRG) supernatants on the production and degradation of platelet-associated growth factors (GFs) (platelet-derived GF isoform BB [PDGF-BB] and transforming growth factor beta-1 [TGF-β1]), pro-inflammatory (tumour necrosis factor alpha [TNF-α]) and anti-inflammatory cytokines (interleukin 4 [IL-4] and IL-1 receptor antagonist [IL-1ra]).

METHODS

CEs from six horses were challenged with LPS and cultured for 96h with L-PRG and P-PRG supernatants at concentrations of 25% and 50%, respectively. The CE culture medium was changed every 48h and used for determination, by ELISA, of PDGF-BB, TGF-β1, TNF-α, IL-4 and IL-1ra.

RESULTS

Both the 25% and 50% PRG supernatants produced a different molecular profile in the culture media, unlike that of the CE challenged with LPS only. 50% L-PRG produced the most sustained release of growth factors and anti-inflammatory cytokines, although it produced the highest TNF-α release. PDGF-BB was significantly correlated with IL-1ra and TNF-α concentrations, whereas TNF-α was correlated with IL-4.

CONCLUSIONS

50% L-PRG supernatant produced a more sustained concentration of growth factors and anti-inflammatory cytokines than the other hemoderivatives evaluated. This substance could be evaluated in animal models of arthritis or in patients with arthropathies.