Association of the risk of osteoarthritis with high innate production of interleukin-1beta and low innate production of interleukin-10 ex vivo, upon lipopolysaccharide stimulation

Molecular biomarker approaches to prevention of post-traumatic osteoarthritis

Up to 50% of individuals develop post-traumatic osteoarthritis (PTOA) within 10 years following knee-joint injuries such as anterior cruciate ligament rupture or acute meniscal tear. Lower-extremity PTOA prevalence is estimated to account for ≥12% of all symptomatic osteoarthritis (OA), or approximately 5.6 million cases in the USA. With knowledge of the inciting event, it might be possible to 'catch PTOA in the act' with sensitive imaging and soluble biomarkers and thereby prevent OA sequelae by early intervention. Existing biomarker data in the joint-injury literature can provide insights into the pathogenesis and early risk trajectory related to PTOA and can help to elucidate a research agenda for preventing or slowing the onset of PTOA. Non-traumatic OA and PTOA have many clinical, radiological and genetic similarities, and efforts to understand early risk trajectories in PTOA might therefore contribute to the identification and classification of early non-traumatic OA, which is the most prevalent form of OA.

The Role of Genetics and Epigenetic Regulation in the Pathogenesis of Osteoarthritis

Osteoarthritis (OA) is progressive disease characterised by cartilage degradation, subchondral bone remodelling and inflammation of the synovium. The disease is associated with obesity, mechanical load and age. However, multiple pro-inflammatory immune mediators regulate the expression of metalloproteinases, which take part in cartilage degradation. Furthermore, genetic factors also contribute to OA susceptibility. Recent studies have highlighted that epigenetic mechanisms may regulate the expression of OA-associated genes. This review aims to present the mechanisms of OA pathogenesis and summarise current evidence regarding the role of genetics and epigenetics in this process.

Role of Platelets in Osteoarthritis-Updated Systematic Review and Meta-Analysis on the Role of Platelet-Rich Plasma in Osteoarthritis

Platelets are an essential component of hemostasis, with an increasing role in host inflammatory processes in injured tissues. The reaction between receptors and vascular endothelial cells results in the recruitment of platelets in the immune response pathway. The aim of the present review is to describe the role of platelets in osteoarthritis. Platelets induce secretion of biological substances, many of which are key players in the inflammatory response in osteoarthritis. Molecules involved in cartilage degeneration, or being markers of inflammation in osteoarthritis, are cytokines, such as tumor necrosis factor α (TNFα), interleukins (IL), type II collagen, aggrecan, and metalloproteinases. Surprisingly, platelets may also be used as a treatment modality for osteoarthritis. Multiple randomized controlled trials included in our systematic review and meta-analyses prove the effectiveness of platelet-rich plasma (PRP) as a minimally invasive method of pain alleviation in osteoarthritis treatment.

Evaluation of Serum Interleukin-38 Levels in Different Radiographic Grades of Idiopathic Knee Osteoarthritis

The aim of this study was to assess interleukin-1β (IL-1β), IL-1Ra, IL-36, and IL-38 levels together with hs-CRP levels in patients with different radiographic grades of knee osteoarthritis (OA) in comparison to healthy individuals. Consecutive patients aged over 50 years who were admitted to our Orthopaedics and Traumatology department between November 2018 and March 2019 and diagnosed as knee OA according to the American College of Rheumatology criteria were included in this prospective case-control study. Patients with knee OA were staged according to radiographic Kellgren-Lawrence (K-L) classification and 20 patients were assigned to each group. An age and gender matched control group consisted healthy volunteers with no clinical and radiographic sign of arthritis were conducted as the control group. Venous blood samples were collected and assessed for hs-CRP, IL-1β, IL-1Ra, IL-36, and IL-38 levels using the double-antibody sandwich ELISA method. The hs-CRP, IL-1β, IL-36 and IL-38 levels did not significantly differ among controls and independent radiographic stage groups except IL-1Ra levels which was significantly higher in K-L grade 4 knee OA groups compared to healthy controls (P = 0.045). When we compared all patients with knee OA and healthy controls, we detected that IL-1 and IL-1Ra were significantly lower and IL-38 levels were significantly higher in healthy control group compared to patients with knee OA (P = <0.001, <0.001, and 0.019, respectively). According to results obtained from our study, IL-1β, IL-1Ra, and IL-38 levels significantly differed between healthy individuals and patients with knee OA. However, we did not observe a significant difference and correlation between radiographic grade of knee OA and interleukin levels.

Bone marrow mononuclear cells for joint therapy: The role of macrophages in inflammation resolution and tissue repair

Osteoarthritis (OA) is the most prevalent joint disease causing major disability and medical expenditures. Synovitis is a central feature of OA and is primarily driven by macrophages. Synovial macrophages not only drive inflammation but also its resolution, through a coordinated, simultaneous expression of pro- and anti-inflammatory mechanisms that are essential to counteract damage and recover homeostasis. Current OA therapies are largely based on anti-inflammatory principles and therefore block pro-inflammatory mechanisms such as prostaglandin E₂ and Nuclear factor-kappa B signaling pathways. However, such mechanisms are also innately required for mounting a pro-resolving response, and their blockage often results in chronic low-grade inflammation. Following minor injury, macrophages shield the damaged area and drive tissue repair. If the damage is more extensive, macrophages incite inflammation recruiting more macrophages from the bone marrow to maximize tissue repair and ultimately resolve inflammation. However, sustained damage and inflammation often overwhelms pro-resolving mechanisms of synovial macrophages leading to the chronic inflammation and related tissue degeneration observed in OA. Recently, experimental and clinical studies have shown that joint injection with autologous bone marrow mononuclear cells replenishes inflamed joints with macrophage and hematopoietic progenitors, enhancing mechanisms of inflammation resolution, providing remarkable and long-lasting effects. Besides creating an ideal environment for resolution with high concentrations of interleukin-10 and anabolic growth factors, macrophage progenitors also have a direct role in tissue repair. Macrophages constitute a large part of the early granulation tissue, and further transdifferentiate from myeloid into a mesenchymal phenotype. These cells, characterized as fibrocytes, are essential for repairing osteochondral defects. Ongoing “omics” studies focused on identifying key drivers of macrophage-mediated resolution of joint inflammation and those required for efficient osteochondral repair, have the potential to uncover ways for developing engineered macrophages or off-the-shelf pro-resolving therapies that can benefit patients suffering from many types of arthropaties, not only OA.

Evaluation of circulating levels of Interleukin-10 and Interleukin-16 and dietary inflammatory index in Lebanese knee osteoarthritis patients

Objectives

To investigate plasma concentrations of Interleukin-16 (IL-16) and Interleukin-10 (IL-10) in Lebanese knee osteoarthritis (KOA) patients and to examine the association between the diet-associated inflammation and increased risk for KOA.

Methods

A total of 208 study participants were assigned to one of the 3 groups: Diagnosed Knee Osteoarthritis group (DKOA) (N = 78); Undiagnosed Knee Osteoarthritis group (UKOA) (N = 60) and controls matched on age, sex and sociodemographic characteristics (N = 70). UKOA represents KOA features before they are altered by therapeutic intervention and lifestyle modifications that follow the diagnosis. Energy-adjusted dietary inflammatory index (E-DII™) scores were calculated using 2-day 24-hour recalls. IL-10 and IL-16 were measured using commercially available sandwich enzyme-linked immunosorbent assay kits.

Results

The UKOA group and controls did not show any significant difference in plasma IL-16 levels (p = 0.28), whereas significantly higher levels of IL-10 were observed in the UKOA group compared to controls (21 ± 41 vs 7.5 ± 12 pg/mL; p = 0.01). The UKOA group had significantly higher IL-16 levels compared to the DKOA group (177 ± 215 vs 80 ± 57 pg/ml; p = 0.001) and significantly higher IL-10 levels compared to the DKOA group (21 ± 41 vs 8 ± 14 pg/mL; p = 0.02). Significantly higher levels of IL-16 were observed in the control group compared to the DKOA group (140 ± 161 vs 80 ± 57 pg/ml; p = 0.009) whereas the DKOA group and controls did not show any significant difference in plasma IL-10 levels (p = 0.82). Additionally, we found significantly higher E-DII scores in the UKOA group compared to controls (0.53 ± 1.028 vs 0.04 ± 1.580; p = 0.04) and in the UKOA group compared to the DKOA group (0.53 ± 1.028 vs -0.37 ± 1.899; p = 0.001). However, there was significant difference in E-DII scores between the DKOA group and controls (p = 0.16).

Conclusions

Our findings indicate an association between circulating levels of IL-10 and KOA in Lebanese population, and a potential role of pro-inflammatory diet in KOA pathology. We did not find an association between circulating levels of IL-16 and KOA.

MK801 regulates the expression of key osteoarthritis factors in osteoarthritis synovial fibroblasts through complement C5

BACKGROUND

Osteoarthritis is currently one of the most common chronic diseases. As life expectancy increases, its prevalence and incidence are expected to rise. At present, more and more evidences prove the correlation between the complement system and osteoarthritis (OA). This study aims to investigate complement C5's influence on the effect of MK801 on osteoarthritis synovial fibroblasts (OA-SFs).

METHODS

We used IL-1b to induce OA-SFs derived from mice to obtain OA-SFs. And we performed RT-PCR and Western Blot assays to evaluate the expression levels of associated mRNA and protein. The alteration of MAC expression on OA-SFs cell membrane was evaluated by immunofluorescence assay. The expression of related inflammatory factors of OA-SFs was evaluated by ELISA experiment.

RESULTS

MK801 could significantly inhibit the expression of osteoarthritis (OA) marker factors, such as: membrane attack complex (MAC), tumor necrosis factor-α (TNF-α) and matrix metalloproteinase-13 (MMP13). Meanwhile, MK801 can significantly inhibit the expression of complement C5 (C5) in OA-SFs. Immunofluorescence assay showed that MAC expression on OA-SFs cell membrane was significantly inhibited by MK801. The nucleo-plasmic separation experiment demonstrated that MK801 could significantly inhibit the activation of Nuclear factor-κB (NF-κB) signaling pathway in OA-SFs. Futhermore, koncking down the expression of C5 reversed the inhibition MK801 on the expression of OA-SFs inflammatory factors.

CONCLUSIONS

These results illustrated two points: first, MK801 inhibited the generation of MAC and the release of inflammation factors in OA-SFs through C5; second: MK801 inhibited the activation of NF-κB signaling pathway in OA-SFs.

Macrophage Activation in the Synovium of Healthy and Osteoarthritic Equine Joints

Synovitis is a major component of osteoarthritis and is driven primarily by macrophages. Synovial macrophages are crucial for joint homeostasis (M2-like phenotype), but induce inflammation (M1-like) when regulatory functions become overwhelmed. Macrophage phenotypes in synovium from osteoarthritic and healthy joints are poorly characterized; however, comparative knowledge of their phenotypes during health and disease is paramount for developing targeted treatments. This study compared patterns of macrophage activation in healthy and osteoarthritic equine synovium and correlated histology with cytokine/chemokine profiles in synovial fluid. Synovial histology and immunohistochemistry for M1-like (CD86), M2-like (CD206, IL-10), and pan macrophage (CD14) markers were performed on biopsies from 29 healthy and 26 osteoarthritic equine joints. Synovial fluid cytokines (MCP-1, IL-10, PGE2, IL-1β, IL-6, TNF-α, IL-1ra) and growth factors (GM-CSF, SDF-1α+β, IGF-1, and FGF-2) were quantified. Macrophage phenotypes were not as clearly defined in vivo as they are in vitro. All macrophage markers were expressed with minimal differences between OA and normal joints. Expression for all markers increased proportionate to synovial inflammation, especially CD86. Synovial fluid MCP-1 was higher in osteoarthritic joints while SDF-1 and IL-10 were lower, and PGE2 concentrations did not differ between groups. Increased CD14/CD86/CD206/IL-10 expression was associated with synovial hyperplasia, consistent with macrophage recruitment and activation in response to injury. Lower synovial fluid IL-10 could suggest that homeostatic mechanisms from synovial macrophages became overwhelmed preventing inflammation resolution, resulting in chronic inflammation and OA. Further investigations into mechanisms of arthritis resolution are warranted. Developing pro-resolving therapies may provide superior results in the treatment of OA.

Addition of Platelet-Rich Plasma to Silk Fibroin Hydrogel Bioprinting for Cartilage Regeneration

The recent advent of 3D bioprinting of biopolymers provides a novel method for fabrication of tissue-engineered scaffolds and also offers a potentially promising avenue in cartilage regeneration. Silk fibroin (SF) is one of the most popular biopolymers used for 3D bioprinting, but further application of SF is hindered by its limited biological activities. Incorporation of growth factors (GFs) has been identified as a solution to improve biological function. Platelet-rich plasma (PRP) is an autologous resource of GFs, which has been widely used in clinic. In this study, we have developed SF-based bioinks incorporated with different concentrations of PRP (12.5%, 25%, and 50%; vol/vol). Release kinetic studies show that SF-PRP bioinks could achieve controlled release of GFs. Subsequently, SF-PRP bioinks were successfully fabricated into scaffolds by bioprinting. Our results revealed that SF-PRP scaffolds possessed proper internal pore structure, good biomechanical properties, and a suitable degradation rate for cartilage regeneration. Live/dead staining showed that 3D, printed SF-PRP scaffolds were biocompatible. Moreover, in vitro studies revealed that tissue-engineered cartilage from the SF-PRP group exhibited improved qualities compared with the pure SF controls, according to histological and immunohistochemical findings. Biochemical evaluations confirmed that SF-PRP (50% PRP, v/v) scaffolds allowed the largest increases in collagen and glycosaminoglycan concentrations, when compared with the pure SF group. These findings suggest that 3D, printed SF-PRP scaffolds could be potential candidates for cartilage tissue engineering. Impact statement Three-dimensional bioprinting of silk fibroin (SF) hydrogel as bioinks is a promising strategy for cartilage tissue engineering, but it lacks biological activities, which favors proliferation of seeded cells and secretion of the extracellular matrix. In this study, we have successfully added platelet-rich plasma (PRP) into SF-based bioinks as an autologous source of growth factors. The 3D, printed SF-PRP scaffold showed an enhanced biological property, thus aiding in potential future development of novel cartilage tissue engineering applications.

Inflamed synovial fluid induces a homeostatic response in bone marrow mononuclear cells in vitro: Implications for joint therapy

Synovial inflammation is a central feature of osteoarthritis (OA), elicited when local regulatory macrophages (M2-like) become overwhelmed, activating an inflammatory response (M1-like). Bone marrow mononuclear cells (BMNC) are a source of naïve macrophages capable of reducing joint inflammation and producing molecules essential for cartilage metabolism. This study investigated the response of BMNC to normal (SF) and inflamed synovial fluid (ISF). Equine BMNC cultured in autologous SF or ISF (n = 8 horses) developed into macrophage-rich cultures with phenotypes similar to cells native to normal SF and became more confluent in ISF (~100%) than SF (~25%). BMNC cultured in SF or ISF were neither M1- nor M2-like, but exhibited aspects of both phenotypes and a regulatory immune response, characterized by increasing counts of IL-10⁺ macrophages, decreasing IL-1β concentrations and progressively increasing IL-10 and IGF-1 concentrations. Changes were more marked in ISF and suggest that homeostatic mechanisms were preserved over time and were potentially favored by progressive cell proliferation. Collectively, our data suggest that intra-articular BMNC could increase synovial macrophage counts, potentiating the macrophage- and IL-10-associated mechanisms of joint homeostasis lost during the progression of OA, preserving the production of cytokines involved in tissue repair (PGE₂ , IL-10) generally impaired by frequently used corticosteroids.

Autologous bone marrow mononuclear cells modulate joint homeostasis in an equine in vivo model of synovitis

Osteoarthritis (OA) is characterized by macrophage-driven synovitis. Macrophages promote synovial health but become inflammatory when their regulatory functions are overwhelmed. Bone marrow mononuclear cells (BMNCs) are a rich source of macrophage progenitors used for treating chronic inflammation and produce essential molecules for cartilage metabolism. This study investigated the response to autologous BMNC injection in normal and inflamed joints. Synovitis was induced in both radiocarpal joints of 6 horses. After 8 h, 1 inflamed radiocarpal and 1 normal tarsocrural joint received BMNC injection. Contralateral joints were injected with saline. Synovial fluid was collected at 24, 96, and 144 h for cytology, cytokine quantification, and flow cytometry. At 144 h, horses were euthanatized, joints were evaluated, and synovium was harvested for histology and immunohistochemistry. Four days after BMNC treatment, inflamed joints had 24% higher macrophage counts with 10% more IL-10⁺ cells than saline-treated controls. BMNC-treated joints showed gross and analytical improvements in synovial fluid and synovial membrane, with increasing regulatory macrophages and synovial fluid IL-10 concentrations compared with saline-treated controls. BMNC-treated joints were comparable to healthy joints histologically, which remained abnormal in saline-treated controls. Autologous BMNCs are readily available, regulate synovitis through macrophage-associated effects, and can benefit thousands of patients with OA.-Menarim, B. C., Gillis, K. H., Oliver, A., Mason, C., Ngo, Y., Werre, S. R., Barrett, S. H., Luo, X., Byron, C. R., Dahlgren, L. A. Autologous bone marrow mononuclear cells modulate joint homeostasis in an equine in vivo model of synovitis.

A predominant Th1 polarization is present in synovial fluid of end-stage osteoarthritic knee joints: analysis of peripheral blood, synovial fluid and synovial membrane

Thorough understanding of the complex pathophysiology of osteoarthritis (OA) is necessary in order to open new avenues for treatment. The aim of this study was to characterize the CD4⁺ T cell population and evaluate their activation and polarization status in OA joints. Fifty-five patients with end-stage knee OA (Kellgren-Lawrence grades III-IV) who underwent surgery for total knee arthroplasty (TKA) were enrolled into this study. Matched samples of synovial membrane (SM), synovial fluid (SF) and peripheral blood (PB) were analysed for CD3⁺ CD4⁺ CD8^- T cell subsets [T helper type 1 (Th1), Th2, Th17, regulatory T cells] and activation status (CD25, CD69, CD45RO, CD45RA, CD62L) by flow cytometry. Subset-specific cytokines were analysed by cytometric bead array (CBA). SM and SF samples showed a distinct infiltration pattern of CD4⁺ T cells. In comparison to PB, a higher amount of joint-derived T cells was polarized into CD3⁺ CD4⁺ CD8^- T cell subsets, with the most significant increase for proinflammatory Th1 cells in SF. CBA analysis revealed significantly increased immunomodulating cytokines [interferon (IFN)-γ, interleukin (IL)-2 and IL-10] in SF compared to PB. Whereas in PB only a small proportion of CD4⁺ T cells were activated, the majority of joint-derived CD4⁺ T cells can be characterized as activated effector memory cells (CD69⁺ CD45RO⁺ CD62L^- ). End-stage OA knees are characterized by an increased CD4⁺ T cell polarization towards activated Th1 cells and cytokine secretion compared to PB. This local inflammation may contribute to disease aggravation and eventually perpetuate the disease process.

Osteoarthritis and the Complement Cascade

Accumulating evidence demonstrates that complement activation is involved in the pathogenesis of osteoarthritis (OA). However, the intimate complement regulation and cross talk with other signaling pathways in joint-associated tissues remain incompletely understood. Recent insights are summarized and discussed here, to put together a more comprehensive picture of complement involvement in OA pathogenesis. Complement is regulated by several catabolic and inflammatory mediators playing a key role in OA. It seems to be involved in many processes observed during OA development and progression, such as extracellular cartilage matrix (ECM) degradation, chondrocyte and synoviocyte inflammatory responses, cell lysis, synovitis, disbalanced bone remodeling, osteophyte formation, and stem cell recruitment, as well as cartilage angiogenesis. In reverse, complement can be activated by various ECM components and their cleavage products, which are released during OA-associated cartilage degradation. There are, however, some other cartilage ECM components that can inhibit complement, underlining the diverse effects of ECM on the complement activation. It is hypothesized that complement might also be directly activated by mechanical stress, thereby contributing to OA. The question arises whether keeping the complement activation in balance could represent a future therapeutic strategy in OA treatment and in the prevention of its progression.

Revisiting the Role of Interleukin-1 Pathway in Osteoarthritis: Interleukin-1α and -1β, and NLRP3 Inflammasome Are Not Involved in the Pathological Features of the Murine Menisectomy Model of Osteoarthritis

Background: Innate immune response components such as toll-like receptors (TLRs) and NLRP3-inflammasome act in concert to increase IL-1α/β secretion by synovial macrophages. Previous results suggest that IL-1α/β could be an important mediator involved in the pathogenesis of osteoarthritis (OA). Objectives: The aim of our study was to evaluate the role of NLRP3, IL-1β, and IL-1α in the menisectomy (MNX) model of murine OA. Methods: Murine chondrocytes (CHs) and bone marrow-derived machrophages (BMDM) were stimulated with hydroxyapatite (HA) crystals, a form of calcium-containing crystal found in human OA, and IL-1β and IL-6 secretion assayed by ELISA.Conversely, the ability of IL-1β and IL-6 to induce CHs calcification was assessed in vitro by Alizarin red staining. Knees from 8 to 10 weeks old C57Bl/6J wild-type (WT) (n = 7), NLRP3^-/- (n = 9), IL-1α^-/- (n = 5), and IL-1β^-/- (n = 5) mice were menisectomized, using the sham-operated contralateral knee as control. 8 weeks later, knee cartilage degradation and synovial inflammation were evaluated by histology. In addition, apoptotic chondrocytes, metalloproteases activity, and collagen-type 2 expression were evaluated in all mice. Joint calcification and subchondral bone parameters were quantified by CT-scan in WT and IL-1β^-/- menisectomized knees. Results:In vitro, HA crystals induced significant increased IL-6 secretion by CHs, while IL-1β remained undetectable.Conversely, both IL-6 and IL-1β were able to increase chondrocytes mineralization. In vivo, operated knees exhibited OA features compared to sham-operated knees as evidenced by increased cartilage degradation and synovial inflammation. In menisectomized KO mice, severity and extent of cartilage lesions were similar (IL-1α^-/- mice) or exacerbated (IL-1β^-/- and NLRP3^-/- mice) compared to that of menisectomized WT mice. Metalloproteases activity, collagen-type 2 expression, chondrocytes apoptosis, and synovial inflammation were similar between KO and WT mice menisectomized knees. Moreover, the extent of joint calcification in osteoarthritic knees was comparable between IL-1β^-/- and WT mice. Conclusions: MNX knees recapitulated features of OA, i.e, cartilage destruction, synovial inflammation, cell death, and joint calcification. Deficiency of IL-1α did not impact on the severity of these features, whereas deficiency of IL-1β or of NLRP3 led to increased cartilage erosion. Our results suggest that IL-1α and IL-1β are not key mediators in this murine OA model and may explain the inefficiency of IL-1 targeted therapies in OA.

Suppression of the inflammatory response by disease-inducible interleukin-10 gene therapy in a three-dimensional micromass model of the human synovial membrane

Background

Gene therapy has the potential to provide long-term production of therapeutic proteins in the joints of osteoarthritis (OA) patients. The objective of this study was to analyse the therapeutic potential of disease-inducible expression of anti-inflammatory interleukin-10 (IL-10) in the three-dimensional micromass model of the human synovial membrane.

Methods

Synovial tissue samples from OA patients were digested and the cells were mixed with Matrigel to obtain 3D micromasses. The CXCL10 promoter combined with the firefly luciferase reporter in a lentiviral vector was used to determine the response of the CXCL10 promoter to tumour necrosis factor alpha (TNF-α), interleukin-1β (IL-1β) and lipopolysaccharide (LPS). The effects of recombinant IL-10 on gene expression were determined by quantitative PCR. The production of IL-10 from the CXCL10p-IL10 vector and the effects on pro-inflammatory cytokine production were assessed by multiplex ELISA.

Results

Micromasses made from whole synovial membrane cell suspensions form a distinct surface composition containing macrophage and fibroblast-like synoviocytes thus mimicking the synovial lining. This lining can be transduced by lentiviruses and allow CXCL-10 promoter-regulated transgene expression. Adequate amounts of IL-10 transgene were produced after stimulation with pro-inflammatory factors able to reduce the production of synovial IL-1β and IL-6.

Conclusions

Synovial micromasses are a suitable model to test disease-regulated gene therapy approaches and the CXCL10p-IL10 vector might be a good candidate to decrease the inflammatory response implicated in the pathogenesis of OA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1083-1) contains supplementary material, which is available to authorized users.

Interleukin 10 protects primary melanocyte by activation of Stat-3 and PI3K/Akt/NF-κB signaling pathways

Vitiligo is a common melanocytopenic disorder of the skin, with acquired focal depigmentation. Normal human skin relies on melanocytes to provide photoprotection and thermoregulation by producing melanin. Interleukin 10 (IL-10) is a pleiotropic immunoregulatory cytokine drawing more and more researchers' attention. The present study was conducted to investigate the effects of IL-10 on melanocytes and elucidate the underlying mechanisms. We proved that IL-10 play no role in regulating melanogenesis of normal human foreskin-derived epidermal melanocytes (NHEM). IL-10 stimulation activated the JAK/Stat-3 and PI3K/Akt signaling pathways. Moreover, IL-10 treatment increased translocation of p65 NF-κB into the nuclear compartment, and up-regulated expression of the pro-survival proteins Bcl-2 and Bcl-xL. IL-10 restored anti-apoptotic proteins expression and suppressed cytochrome c release in H2O2-induced apoptosis. In conclusion, IL-10 may provide pro-survival cues to melanocytes and be applied in the treatment of vitiligo and other depigmenting disorders.

Inflammatory biomarkers in osteoarthritis

Osteoarthritis (OA) is highly prevalent and a leading cause of disability worldwide. Despite the global burden of OA, diagnostic tests and treatments for the molecular or early subclinical stages are still not available for clinical use. In recent years, there has been a large shift in the understanding of OA as a "wear and tear" disease to an inflammatory disease. This has been demonstrated through various studies using MRI, ultrasound, histochemistry, and biomarkers. It would of great value to be able to readily identify subclinical and/or sub-acute inflammation, particularly in such a way as to be appropriate for a clinical setting. Here we review several types of biomarkers associated with OA in human studies that point to a role of inflammation in OA.

LPS-Stimulated Whole Blood Cytokine Production Is Not Related to Disease Behavior in Patients with Quiescent Crohn's Disease

Introduction

Crohn’s disease (CD) is a chronic inflammatory disease in which cytokines play a pivotal role in the induction and maintenance of inflammation. Innate cytokine production is genetically determined and varies largely between individuals; this might impact the severity of inflammation. We aimed to assess whether ex-vivo endotoxin-stimulated levels of cytokines could be associated with disease phenotype.

Methods

Patients with quiescent CD (Harvey-Bradshaw Index ≤ 4 and negative inflammation markers) who were not using immunomodulating drugs or biologicals were eligible. Historical disease characteristics (localization, behavior, number of bowel resections, drug history, extra-intestinal symptoms) were extracted from medical records. We measured cytokine levels (tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and IL-10) in supernatants of lipopolysaccharide (LPS) -stimulated whole blood cultures and correlated these with disease characteristics and age- and sex-matched healthy controls. In addition, we analyzed whether single nucleotide polymorphisms (SNPs) in the promoter region of the TNF-α gene were related to TNF-α levels.

Results

We included 75 patients with CD and 24 healthy controls. Six patients were excluded because of increased inflammation markers resulting in a total of 69 patients. The mean age (SD) of patients with CD was 51.2 (12.3) years with a mean (SD) disease duration of 24.1 (11.5) years. Disease localization, peri-anal involvement and behavior were not related to LPS-stimulated TNF-α, IL-1β, IL-6 or IL-10 levels. In addition, combination of localization with behavior to differentiate mild from severe disease type showed no significant differences. TNF-α levels were higher in patients with CD (428 pg/ml IQR [267-468]) compared to healthy controls (459 pg/ml IQR [364-570], p=0.02). We found no associations between SNPs in the promoter region and TNF-α levels.

Conclusion

In this study, innate cytokine production of TNF-α, IL-1β, IL-6 and IL-10 was not related to historical disease characteristics or disease severity in patients with quiescent CD. These findings suggest that genetically determined levels of these cytokines obtained from LPS-stimulated whole blood cultures are not linked with disease behavior or severity.

Effects of insomnia disorder and knee osteoarthritis on resting and pain-evoked inflammatory markers

Osteoarthritis is the most prevalent arthritic condition. Systemic inflammatory cytokines appear to have an important role in the onset and maintenance of the disease. Sleep disturbances are prevalent in osteoarthritis and associated with alterations in systemic inflammatory cytokines, suggesting a common pathophysiology across these conditions. A comparative investigation of the effects of insomnia disorder and osteoarthritis on pain-evoked cytokine responses has yet to be undertaken. We examined the influence of symptomatic knee osteoarthritis and insomnia disorder on resting C-reactive protein (CRP), interleukin (IL)-6, and IL-10 levels, and pain-evoked IL-6 and IL-10 responses. Participants were N=117 older adults (mean age=59.7years; 61.8% women) rigorously evaluated for knee osteoarthritis and insomnia disorder using established diagnostic guidelines. Results revealed no association of osteoarthritis or insomnia disorder with CRP. Resting IL-6 was greater in osteoarthritis participants versus those without osteoarthritis, although this association was largely attributable to BMI. IL-10 was highest among participants with osteoarthritis or insomnia disorder. Growth curve modeling revealed that participants with insomnia disorder had greater pain-evoked IL-6 responses than participants without insomnia disorder or osteoarthritis. These findings highlight the utility of laboratory pain testing methods for understanding individual differences in inflammatory cytokines. Moreover, our findings provide evidence for amplified pain-evoked pro-inflammatory cytokine reactivity among older adults with clinically diagnosed insomnia disorder, even after controlling for individual differences in BMI and age. Additional research will be required determine whether an amplified pain-related cytokine response contributes to OA, and possibly other age-related disease, associated with insomnia disorder.

Unicompartmental and bicompartmental knee osteoarthritis show different patterns of mononuclear cell infiltration and cytokine release in the affected joints

It is still controversial which cell types are responsible for synovial inflammation in osteoarthritic (OA) joints. The aim of this study was to quantify the mononuclear cell populations and their cytokines in patients with different knee OA subtypes. Synovial membrane (SM), synovial fluid (SF) and peripheral blood (PB) were harvested from patients with unicompartmental (UC) and bicompartmental (BC) knee OA. Frequencies of mononuclear cells were assessed by flow cytometry in PB and SM. Naive SF samples were analysed for a broad variety of cytokines by multiplex analysis. SM of both groups displayed a distinct mononuclear cell infiltration, with CD14(+) macrophages being the major cell population, followed by CD4(+) T cells and only small numbers of CD8(+) T, CD19(+) B and CD16(+) CD56(+) natural killer (NK) cells. Between the two groups, SM of BC OA showed significantly higher amounts of mononuclear cells (135·7 ± 180 versus 805 ± 675 cells/mg, P = 0·0009) and higher CD4(+) T cell presence (3·4 ± 4·6 versus 9·1 ± 7·5%, P = 0·0267). SF of BC OA displayed significantly higher concentrations for a number of proinflammatory cytokines [CXCL1, eotaxin, interferon (IFN)-γ, interleukin (IL)-7, IL-8, IL-9, IL-12]. UC and BC OA show significant differences in their synovial inflammatory pattern. Whereas in UC OA CD14(+) macrophages are the predominant cell population, BC OA has a higher inflammatory profile and seems to be driven by CD14(+) macrophages and CD4(+) T cells. Inclusion of clinical information into the analysis of cellular and molecular results is pivotal in understanding the pathophysiology of OA.

Cytokines as biochemical markers for knee osteoarthritis

Osteoarthritis (OA) is a debilitating degenerative joint disease particularly affecting weightbearing joints within the body, principally the hips and knees. Current radiographic techniques are insufficient to show biochemical changes within joint tissue which can occur many years before symptoms become apparent. The need for better diagnostic and prognostic tools is heightened with the prevalence of OA set to increase in aging and obese populations. As inflammation is increasingly being considered an important part of OAs pathophysiology, cytokines are being assessed as possible candidates for biochemical markers. Cytokines, both pro- and anti-inflammatory, as well as angiogenic and chemotactic, have in recent years been studied for relevant characteristics. Biochemical markers show promise in determination of the severity of disease in addition to monitoring of the efficacy and safety of disease-modifying OA drugs, with the potential to act as diagnostic and prognostic tools. Currently, the diagnostic power of interleukin (IL)-6 and the relationship to disease burden of IL-1β, IL-15, tumor necrosis factor-α, and vascular endothelial growth factor make these the best candidates for assessment. Grouping appropriate cytokine markers together and assessing them collectively alongside other bone and cartilage degradation products will yield a more statistically powerful tool in research and clinical applications, and additionally aid in distinguishing between OA and a number of other diseases in which cytokines are known to have an involvement. Further large scale studies are needed to assess the validity and efficacy of current biomarkers, and to discover other potential biomarker candidates.

The therapeutic potential of interleukin-10 in neuroimmune diseases

Neuroimmune diseases have diverse symptoms and etiologies but all involve pathological inflammation that affects normal central nervous system signaling. Critically, many neuroimmune diseases also involve insufficient signaling/bioavailability of interleukin-10 (IL-10). IL-10 is a potent anti-inflammatory cytokine released by immune cells and glia, which drives the regulation of a variety of anti-inflammatory processes. This review will focus on the signaling pathways and function of IL-10, the current evidence for insufficiencies in IL-10 signaling/bioavailability in neuroimmune diseases, as well as the implications for IL-10-based therapies to treating such problems. We will review in detail four pathologies as examples of the common etiologies of such disease states, namely neuropathic pain (nerve trauma), osteoarthritis (peripheral inflammation), Parkinson's disease (neurodegeneration), and multiple sclerosis (autoimmune). A number of methods to increase IL-10 have been developed (e.g. protein administration, viral vectors, naked plasmid DNA, plasmid DNA packaged in polymers to enhance their uptake into target cells, and adenosine 2A agonists), which will also be discussed. In general, IL-10-based therapies have been effective at treating both the symptoms and pathology associated with various neuroimmune diseases, with more sophisticated gene therapy-based methods producing sustained therapeutic effects lasting for several months following a single injection. These exciting results have resulted in IL-10-targeted therapeutics being positioned for upcoming clinical trials for treating neuroimmune diseases, including neuropathic pain. Although further research is necessary to determine the full range of effects associated with IL-10-based therapy, evidence suggests IL-10 may be an invaluable target for the treatment of neuroimmune disease. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.

Wojdasiewicz P, Poniatowski LA, Szukiewicz D. The role of inflammatory and anti-inflammatory cytokines in the pathogenesis of osteoarthritis: review article. Mediators of Inflammation. USA: Hindawi Publishing Corporation 2014; 1-20. [PMID: 24876674 PMCID: PMC4021678 DOI: 10.1155/2014/561459]

Osteoarthritis (OA) is the most common chronic disease of human joints. The basis of pathologic changes involves all the tissues forming the joint; already, at an early stage, it has the nature of inflammation with varying degrees of severity. An analysis of the complex relationships indicates that the processes taking place inside the joint are not merely a set that (seemingly) only includes catabolic effects. Apart from them, anti-inflammatory anabolic processes also occur continually. These phenomena are driven by various mediators, of which the key role is attributed to the interactions within the cytokine network. The most important group controlling the disease seems to be inflammatory cytokines, including IL-1β, TNFα, IL-6, IL-15, IL-17, and IL-18. The second group with antagonistic effect is formed by cytokines known as anti-inflammatory cytokines such as IL-4, IL-10, and IL-13. The role of inflammatory and anti-inflammatory cytokines in the pathogenesis of OA with respect to inter- and intracellular signaling pathways is still under investigation. This paper summarizes the current state of knowledge. The cytokine network in OA is put in the context of cells involved in this degenerative joint disease. The possibilities for further implementation of new therapeutic strategies in OA are also pointed.

Role of interleukin-10 in endochondral bone formation in mice: anabolic effect via the bone morphogenetic protein/Smad pathway

OBJECTIVE

Interleukin-10 (IL-10) is a pleiotropic immunoregulatory cytokine with a chondroprotective effect that is elevated in cartilage and synovium in patients with osteoarthritis. However, the role of IL-10 during endochondral bone formation and its mechanism of action have not been elucidated.

METHODS

IL-10(-/-) mice and IL-10-treated tibial organ cultures were used to study loss and gain of IL-10 functions, respectively, during endochondral bone formation. Primary chondrocytes from the long bones of mouse embryos were cultured with and without IL-10. To assess the role of IL-10 in chondrogenic differentiation, we conducted mesenchymal cell micromass cultures.

RESULTS

The lengths of whole skeletons from IL-10(-/-) mice were similar to those of their wild-type littermates, although their skull diameters were smaller. The tibial growth plates of IL-10(-/-) mice showed shortening of the proliferating zone. Treatment with IL-10 significantly increased tibial lengths in organ culture. IL-10 also induced chondrocyte proliferation and hypertrophic differentiation in primary chondrocytes in vitro. Mechanistically, IL-10 activated STAT-3 and the Smad1/5/8 and ERK-1/2 MAP kinase pathways and induced the expression of bone morphogenetic protein 2 (BMP-2) and BMP-6 in primary chondrocytes. Furthermore, the blocking of BMP signaling attenuated the IL-10-mediated induction of cyclin D1 and RUNX-2 in primary chondrocytes and suppressed Alcian blue and alkaline phosphatase staining in mesenchymal cell micromass cultures.

CONCLUSION

These results indicate that IL-10 acts as a stimulator of chondrocyte proliferation and chondrogenic or hypertrophic differentiation via activation of the BMP signaling pathway.

Role of hormones in cartilage and joint metabolism: understanding an unhealthy metabolic phenotype in osteoarthritis

OBJECTIVE

Joint health is affected by local and systemic hormones. It is well accepted that systemic factors regulate the metabolism of joint tissues, and that substantial cross-talk between tissues actively contributes to homeostasis. In the current review, we try to define a subtype of osteoarthritis (OA), metabolic OA, which is dependent on an unhealthy phenotype.

METHODS

Peer-reviewed research articles and reviews were reviewed and summarized. Only literature readily available online, either by download or by purchase order, was included.

RESULTS

OA is the most common joint disease and is more common in women after menopause. OA is a disease that affects the whole joint, including cartilage, subchondral bone, synovium, tendons, and muscles. The clinical endpoints of OA are pain and joint space narrowing, which is characterized by cartilage erosion and subchondral sclerosis, suggesting that cartilage is a central tissue of joint health. Thus, the joint, more specifically the cartilage, may be considered a target of endocrine function in addition to the well-described traditional risk factors of disease initiation and progression such as long-term loading of the joint due to obesity. Metabolic syndrome affects a range of tissues and may in part be molecularly described as a dysregulation of cytokines, adipokines, and hormones (e.g., estrogen and thyroid hormone). Consequently, metabolic imbalance may both directly and indirectly influence joint health and cartilage turnover, altering the progression of diseases such as OA.

CONCLUSIONS

There is substantial evidence for a connection between metabolic health and development of OA. We propose that more focus be directed to understanding this connection to improve the management of menopausal health and associated comorbidities.

Matrix-embedded cytokines to simulate osteoarthritis-like cartilage microenvironments

In vivo, cytokines noncovalently bind to the extracellular matrix (ECM), to facilitate intimate interactions with cellular receptors and potentiate biological activity. Development of a biomaterial that simulates this type of physiological binding and function is an exciting proposition for designing controlled advanced delivery systems for simulating in vivo conditions in vitro. We have decorated silk protein with sulfonated moieties through diazonium coupling reactions to noncovalently immobilize pro-inflammatory cytokines interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in such a biomimetic manner. After adsorption of the cytokines to the diazonium-modified silk matrix, constant release of cytokines up to at least 3 days was demonstrated, as an initial step to simulate an osteoarthritic (OA) microenvironment in vitro. Matrix-embedded cytokines induced the formation of multiple elongated processes in chondrocytes in vitro, akin to what is seen in OA cartilage in vivo. Gene expression profiles with this in vitro tissue model of OA showed significant similarities to profiles from explanted OA cartilage tissues collected from patients who underwent total knee replacement surgery. The common markers of OA, including COL, MMP, TIMP, ADAMTS, and metallothioneins, were upregulated at least 35-fold in the in vitro model when compared to the control-non-OA in vitro generated tissue-engineered cartilage. The microarray data were validated by reverse transcriptase-polymerase chain reaction. Mechanistically, protein interaction studies indicated that TNF-α and IL-1β synergistically controlled the equilibrium between MMPs and their inhibitors, TIMPs, resulting in ECM degradation through the MAPK pathway. This study offers a promising initial step toward establishing a relevant in vitro OA disease model, which can be further modified to assess signaling mechanisms, responses to cell or drug treatments and patient-specific features.

Comparing different physical factors on serum TNF-α levels, chondrocyte apoptosis, caspase-3 and caspase-8 expression in osteoarthritis of the knee in rabbits

OBJECTIVE

To study the therapeutic effects that different physical factors may have on rabbits with osteoarthritis of the knee.

METHODS

A total of 64 rabbits were randomised and organised into eight groups, eight of which were each assigned a different physical factor, in which the rabbits received one type of physical therapy: millimetre waves for 20 min, pulsed electromagnetic fields, millimetre waves for 40 min, ultrasound, low-level laser therapy or ultrashort wave diathermy. The two remaining groups, the normal group and the model group, served as controls. The efficacy of the different treatments were determined by observing the configuration and structure of the cartilaginous tissue by haematoxylin and Eosin staining, measuring the serum tumour necrosis factor-α levels by enzyme immunoassay, evaluating the expression levels of caspases-3 and -8 by immunohistochemistry, and calculating the ratio of chondrocytes apoptosis by TdT-mediated dUTP nick end labelling. The values obtained for each assessment of the eight groups were analysed by a One-way ANOVA.

RESULTS

By applying upmentioned physical treatments, the organisational configuration and structure of cartilage cells from the knees of rabbits with osteoarthritis increased. These treatments also decreased serum tumour necrosis factor-α levels, reduced the expression of caspase-3 and caspase-8 and reduced chondrocyte apoptosis, resulting in an overall delay in osteoarthritis development.

CONCLUSION

The application of pulsed electromagnetic fields, millimetre waves for 40 min, ultrasound, or low-level laser therapy had significant effects in improving osteoarthritis; in particular, treatment with pulsed electromagnetic fields or ultrasound yielded the greatest therapeutic effect.

Circulating levels of IL-6 and TNF-α are associated with knee radiographic osteoarthritis and knee cartilage loss in older adults

OBJECTIVE

The role of inflammation in osteoarthritis (OA) pathogenesis is unclear, and the associations between inflammatory cytokines and cartilage loss have not been reported. We determined the associations between serum levels of interleukin (IL)-6 and tumor necrosis factor-α (TNF-α), knee radiographic OA (ROA) and cartilage loss over 2.9 years in older adults.

METHODS

A total of 172 randomly selected subjects (mean 63 years, range 52-78, 47% female) were studied at baseline and approximately 3 (range 2.6-3.3) years later. IL-6 and TNF-α were assessed by radioimmunoassay. T1-weighted fat-suppressed magnetic resonance imaging of the right knee was performed at baseline and follow-up to determine knee cartilage volume. Knee ROA of both knees was assessed at baseline.

RESULTS

At baseline, quartiles of IL-6 and TNF-α were associated with increased prevalence of medial tibiofemoral joint space narrowing (OARSI grade ≥ 1) in multivariate analyses [odds ratio (OR): 1.42 and 1.47 per quartile, respectively, both P<0.05]. Longitudinally, baseline IL-6 predicted loss of both medial and lateral tibial cartilage volume (β: -1.19% and -1.35% per annum per quartile, P<0.05 and P<0.01, respectively), independently of TNF-α. Change in IL-6 was associated with increased loss of medial and lateral tibial cartilage volume (β: -1.18% and -1.06% per annum per quartile, both P<0.05) and change in TNF-α was also negatively associated with change in medial cartilage volume (β: -1.27% per annum per quartile, P<0.05).

CONCLUSIONS

Serum levels of IL-6 and TNF-α are associated with knee cartilage loss in older people suggesting low level inflammation plays a role in the pathogenesis of knee OA.

Treatment with TNF-α inhibitor infliximab might reduce hand osteoarthritis in patients with rheumatoid arthritis

OBJECTIVES

To investigate the association between systemic and local inflammation and incident and progressive radiographic secondary osteoarthritis (OA) in interphalangeal joints (IPJs) over 3 years in rheumatoid arthritis (RA) patients and the effect of tumor necrosis factor alpha (TNF-α) inhibitor infliximab on secondary OA in IPJs.

METHODS

In the present observational longitudinal study baseline and 3-year hand X-rays of 416 recent-onset RA patients were scored for osteophytes and erosions in IPJs, blinded for time, using Osteoarthritis Research Society International atlas and Sharp-van der Heijde score. The associations between inflammatory factors and incident and progressive secondary OA in distal IPJs (DIPJs) and proximal IPJs (PIPJs) and the effect of infliximab compared to disease-modifying anti-rheumatic drug treatment on secondary OA were analyzed by multivariable regression and generalised estimating equations analyses.

RESULTS

Sixty-seven percent of the patients were female with, at baseline, a mean age of 54 years and OA present in DIPJs and PIPJs in 37% and 13%. Three years later, new secondary OA in DIPJs and PIPJs was seen in 11% and 10%, and progressive secondary OA in 36% and 35%. High erythrocyte sedimentation rate over 3 years and progressive erosive damage were risk factors for incident secondary OA in DIPJs, but not in PIPJs. At joint level, progression of erosions was associated with both incident and progressive secondary OA, only in DIPJs. Infliximab treatment was associated with lower incident secondary OA in PIPJs [relative risk 0.5 (95% confidence interval 0.2, 1.0)], independent of decrease in inflammation.

CONCLUSION

Incident and progressive secondary OA in DIPJs over 3 years was associated with high inflammatory activity in RA. Infliximab treatment reduced incident secondary OA in PIPJs independent of decrease in inflammation, suggesting that anti-TNF-α therapy might be effective against secondary hand OA via other pathways than suppression of inflammation. Further studies in populations of primary hand OA are necessary to determine the role of anti-TNF-α in treatment of primary hand OA.

Low innate production of interleukin-1beta and interleukin-6 is associated with the absence of osteoarthritis in old age

OBJECTIVE

We investigated whether innate differences in cytokine response were associated with the absence of osteoarthritis (OA) in old age.

DESIGN

In 82 participants from a cross-sectional birth cohort, radiographs of hands, hips and knees were taken at the age of 90 years. OA was defined as a Kellgren-Lawrence score of at least two. "Free from OA" was defined at patient level as absence of hip and knee OA, and presence of OA in maximally two hand joints. The innate cytokine response was determined in whole-blood samples upon stimulation with lipopolysaccharide. Logistic regression analyses were used to investigate associations between absence of OA in relation to tertiles of interleukin (IL)-1beta, IL-6, tumor necrosis factor (TNF)-alpha, IL-1 receptor antagonist (RA) and IL-10. Adjustments were made for gender and body mass index.

RESULTS

Sixteen percent of the participants were "free from OA". Subjects in the lowest tertile of Il-1beta production had a 11-fold increased chance to be free of OA [odds ratio (OR) 11.3, confidence intervals (CI) 95% 1.1-115.9], subjects in the lowest tertile of IL-6 production had an almost 7-fold increased chance to be free of OA (OR 6.7, 95% CI 1.1-41.2). Absence of hand OA was associated with low innate production of IL-6 and IL-1RA, absence of hip OA was associated with low innate IL-1beta production. No associations were found for TNF-alpha and IL-10.

CONCLUSIONS

Low innate capacity to produce the pro-inflammatory cytokines IL-1beta and IL-6 is associated with the absence of OA in old age.

Interleukin-1 gene cluster variants with innate cytokine production profiles and osteoarthritis in subjects from the Genetics, Osteoarthritis and Progression Study

OBJECTIVE

To assess whether genetic variation in the interleukin-1 (IL-1) gene cluster contributes to familial osteoarthritis (OA) by influencing innate ex vivo production of IL-1beta or IL-1 receptor antagonist (IL-1Ra).

METHODS

Innate ex vivo IL-1beta and IL-1Ra production upon lipopolysaccharide (LPS) stimulation of whole blood cells was measured in subjects from the Genetics, Osteoarthritis and Progression (GARP) Study, which includes sibling pairs in which at least one sibling has symptomatic OA at multiple sites. Radiographic OA (ROA) was assessed by Kellgren/Lawrence score. Subjects from the GARP Study and controls from the Rotterdam Study were genotyped for 7 single-nucleotide polymorphisms (SNPs) encompassing the IL-1 gene cluster on chromosome 2q13. Linkage disequilibrium analysis and genotype and haplotype association analysis were performed to assess the relationship between the IL-1 gene cluster SNPs, innate ex vivo cytokine production, and OA.

RESULTS

Among subjects in the GARP Study, the haplotype variable-number tandem repeat in intron 2/T+8006C/T+11100C 2/2/1 of the IL1RN gene was significantly associated with reduced innate ex vivo bioavailability of IL-1beta upon LPS stimulation (P = 0.026) and with ROA at the highest number of joint locations.

CONCLUSION

These results show that genetic variation at the IL-1 gene cluster is associated with lower IL-1beta bioavailability and with OA at a large number of joint locations. The data further indicate that, among subjects with OA affecting the highest number of joints, the innate immune system may be activated, thereby obscuring possible underlying mechanisms.

A genome-wide linkage scan reveals CD53 as an important regulator of innate TNF-alpha levels

Cytokines are major immune system regulators. Previously, innate cytokine profiles determined by lipopolysaccharide stimulation were shown to be highly heritable. To identify regulating genes in innate immunity, we analyzed data from a genome-wide linkage scan using microsatellites in osteoarthritis (OA) patients (The GARP study) and their innate cytokine data on interleukin (IL)-1beta, IL-1Ra, IL-10 and tumor necrosis factor (TNF)alpha. A confirmation cohort consisted of the Leiden 85-Plus study. In this study, a linkage analysis was followed by manual selection of candidate genes in linkage regions showing LOD scores over 2.5. An single-nucleotide polymorphism (SNP) gene tagging method was applied to select SNPs on the basis of the highest level of gene tagging and possible functional effects. QTDT was used to identify the SNPs associated with innate cytokine production. Initial association signals were modeled by a linear mixed model. Through these analyses, we identified 10 putative genes involved in the regulation of TNFalpha. SNP rs6679497 in gene CD53 showed significant association with TNFalpha levels (P=0.001). No association of this SNP was observed with OA. A novel gene involved in the innate immune response of TNFalpha is identified. Genetic variation in this gene may have a role in diseases and disorders in which TNFalpha is closely involved.

Allelic variants of IL1R1 gene associate with severe hand osteoarthritis

Background

In search for genes predisposing to osteoarthritis (OA), several genome wide scans have provided evidence for linkage on 2q. In this study we targeted a 470 kb region on 2q11.2 presenting the locus with most evidence for linkage to severe OA of distal interphalangeal joints (DIP) in our genome wide scan families.

Methods

We genotyped 32 single nucleotide polymorphisms (SNPs) in this 470 kb region comprising six genes belonging to the interleukin 1 superfamily and monitored for association with individual SNPs and SNP haplotypes among severe familial hand OA cases (material extended from our previous linkage study; n = 134), unrelated end-stage bilateral primary knee OA cases (n = 113), and population based controls (n = 436).

Results

Four SNPs in the IL1R1 gene, mapping to a 125 kb LD block, provided evidence for association with hand OA in family-based and case-control analysis, the strongest association being with SNP rs2287047 (p-value = 0.0009).

Conclusions

This study demonstrates an association between severe hand OA and IL1R1 gene. This gene represents a highly relevant biological candidate since it encodes protein that is a known modulator of inflammatory processes associated with joint destruction and resides within a locus providing consistent evidence for linkage to hand OA. As the observed association did not fully explain the linkage obtained in the previous study, it is plausible that also other variants in this genome region predispose to hand OA.

Interleukin-1 region meta-analysis with osteoarthritis phenotypes

OBJECTIVE

Several research groups have examined osteoarthritis (OA) association with Interleukin-1 (IL-1) region markers and haplotypes. The results have been suggestive for hand OA, negative for knee OA, and conflicting for hip OA.

DESIGN

Our aim was to address conflicts employing meta-analytical methods on data from 1238 European-descent cases with various OA phenotypes and 1269 European-descent controls from four study centers. We imputed some missing genotype data and reconstructed IL-1 region extended haplotypes. A previously reported 7-marker IL1A-IL1B-IL1RN extended risk haplotype was tested for association with each specific index phenotype.

RESULTS

For hip OA, data from three centers showed heterogeneity of extended-risk-haplotype effect, two panels showing trend toward risk and another showing protection, with overall odds ratio (OR) 1.24 (95% Confidence interval (CI) 0.45-3.41, P 0.67). The heterogeneity fell partly along control ascertainment lines, chiefly between controls ascertained as spouses of arthroplasty patients and controls identified through population radiographic survey. For knee OA, the results showed no heterogeneity and no significant extended-risk-haplotype effect. For hand OA, the results showed little heterogeneity and a modest trend toward positive association (summary OR 1.34, 95% CI 0.83-2.17 P 0.23). Using a Bayesian partition modeling approach, the 7-marker extended haplotypes showed no significant effect on any OA phenotype examined. A 3-single-nucleotide polymorphism (SNP) IL1B-IL1RN haplotype rs1143627-rs16944-rs419598 showed a trend toward hand OA association (posterior probability of association 0.72) with the most prominent feature being protection from a specific haplotype representing a partial mirror image of the extended risk haplotype (OR estimated at 0.46).

CONCLUSIONS

The meta-analysis data do not confirm but only suggest that some hand and hip OA risk could be associated with the IL-1 region, particularly centered in IL1B and possibly also IL1RN.

Association Between Interleukin 1 Gene Cluster Polymorphisms and Bilateral Distal Interphalangeal Osteoarthritis

Objective.

To examine the association of the interleukin 1 gene (IL1) cluster polymorphisms and their haplotypes with bilateral distal interphalangeal joint osteoarthritis (DIP OA).

Methods.

Radiographs of both hands of 295 dentists and 248 teachers were examined and classified for the presence of OA using reference images. Bilateral DIP OA was defined by the presence of radiographic findings of grade 2 or more in at least 1 symmetrical pair of the DIP joints. We genotyped 10 single-nucleotide polymorphisms (SNP) in theIL1R1, IL1RL2, IL1A, IL1B,andIL1RNgenes using polymerase chain reaction-based methods. Haplotypes were statistically reconstructed using the PHASE program. The association between the genotypes/diplotypes and bilateral DIP OA was examined with logistic regression analysis.

Results.

TwoIL1BSNP (rs1143634 and rs1143633) were associated with bilateral DIP OA. The carriers of theIL1Brs1143634 minor allele had an increased OA risk [odds ratio (OR) 1.6; 95% confidence interval (CI) 1.08–2.26] compared to the noncarriers. The association was stronger in the dentists. The distribution of theIL1Brs1143633 genotype fit a recessive mode of inheritance (OR 3.03, 95% CI 1.35–6.83, p = 0.006). TwoIL1B-IL1RNextended haplotype alleles (211-1 and 121-1) were associated with bilateral DIP OA. An interaction between theIL1Brs1143634 and theIL1R1-IL1RL2andIL1B-IL1RNextended haplotypes and occupation (increased risk of OA among dentists only) was observed.

Conclusion.

Our results provide further evidence for the role ofIL1gene cluster polymorphisms in the etiology of OA and suggest that some of these may predispose DIP joints to the effects of mechanical overload.

The role of plasma cytokine levels, CRP and Selenoprotein S gene variation in OA

OBJECTIVE

Investigating the association between plasma levels of cytokines and chemokines, Selenoprotein S (SELS) gene variation and osteoarthritis (OA) subtypes.

METHODS

The genetics of osteoarthritis and progression (GARP) study consists of 191 sibling pairs with symptomatic OA at multiple joint sites. We have measured plasma levels of 17 cytokines and chemokines and genetic variation at the SELS gene.

RESULTS

Nine out of 17 serum markers could be assessed quantitatively, whereas eight markers were assessed qualitatively. Principal component analysis (PCA) on the quantitatively assessed markers and serum high sensitive C-reactive protein (S-HsCRP) revealed that three components underlie 61% of the total plasma variation. Three single nucleotide polymorphisms (SNPs) in the SELS gene revealed four common haplotypes, one of which, GAG (frequency 3.5%) showed significant association to an anti-inflammatory (P=0.019) and acute phase related (P=0.036) component. OA subtype analysis showed that one component (mainly representing chemokine variation) was significantly associated to hand OA and disc degeneration (P=0.029 and P=0.010 respectively) as well as a physical component score (PCS) (P=0.042). The CRP related component also showed a strong association to the PCS (P=0.007). SELS haplotypes showed no association to OA subtypes in the GARP study.

CONCLUSION

Genetic variation in the SELS gene associates to components representing inflammatory signaling. Another component, representing chemokine variation, showed association to hand OA and disc degeneration in the GARP study indicating chemokines may contribute to OA pathogenesis.

Risk factors in familial osteoarthritis: the GARP sibling study

PURPOSE

To investigate the association between systemic and local risk factors and familial osteoarthritis (OA) at multiple sites.

METHODS

Patients and their siblings had primary OA at multiple sites at middle age. OA diagnosis followed the American College of Rheumatology criteria. We recruited 345 controls (mean age 57 years (range 40-76), 64% women) by random sampling from the population by telephone and collected all data by questionnaires. Odds ratios (ORs) were adjusted for sex, age and body mass index (BMI) (kg/m(2)), 95% confidence intervals (CIs95) were computed using robust standard errors with the intra-family effect taken into account.

RESULTS

Three hundred and eighty-two patients (mean age 60 years [range 43-79]), 82% women had OA in the spine (80%), hands (72%), knees (34%) and hips (24%). In women, an association of familial OA with a young age at natural menopause (<45 years), OR=2.6 (CI95 1.5-4.5) was found. Physically demanding jobs led to an increased risk of familial OA in men: OR=2.6 (CI95 1.3-5.3). Familial OA was more prevalent in individuals with a BMI>30, OR=2.0 (CI95 1.3-3.2) compared to a BMI of <25. Taller persons had a lower risk of familial OA, OR=0.33 (0.1-0.8) in the height category >180 cm relative to a height of <160 cm. A history of meniscectomy, increased the risk of familial OA at multiple sites with knee involvement, OR=6.2 (CI95 3.0-12.7).

CONCLUSIONS

Systemic and local risk factors play a role in the etiology of familial OA at multiple sites.

Potential influence of IL1B haplotype and IL1A-IL1B-IL1RN extended haplotype on hand osteoarthritis risk

OBJECTIVE

To assess osteoarthritis (OA) association with the human interleukin-1 (IL-1) region.

DESIGN

Sixty-four European-descent cases with radiographic hand OA and 48 European-descent controls were genotyped at nine single nucleotide polymorphism (SNP), one variable-number-of-tandem-repeat (VNTR), and one microsatellite marker extending across loci for IL-1alpha (IL1A), IL-1beta (IL1B), and IL-1 receptor antagonist (IL1RN). The genotype data were used to reconstruct individual locus haplotypes, and then locus haplotypes were used as superalleles for extended haplotype reconstruction.

RESULTS

Nine different extended IL1A-IL1B-IL1RN haplotypes occurred at a frequency 0.05 or greater in either cases or controls. Only two IL1A-IL1B-IL1RN extended haplotypes were consistent with previously described extended risk haplotypes and totaled n=9 in cases and n=3 in controls [odds ratio (OR) 2.1, Haldane's chi(2) 1.67, one-sided P 0.1]. Our prior report showed hand OA association with homozygous IL1B rs1143633 minor allele genotype. All except one extended risk haplotype copy also had the IL1B rs1143633 minor allele. The rs1143633 genotype association was explained by one common six-SNP IL1B haplotype bearing rs1143633 minor allele and also risk alleles at rs1143634, rs1143627, and rs16944, component markers of the previously described extended risk haplotypes. The IL1B haplotype bearing all three risk alleles was found in 16 haplotype-homozygous hand OA cases and in four haplotype-homozygous controls and conferred OR 3.4 among homozygotes (nominal P value 0.006).

CONCLUSION

Our evidence broadly supports the genetic association of OA phenotypes with an IL-1 region extended risk haplotype and specifically IL1B genotype. The extended risk haplotype previously associated with hip OA appears to be less frequent and has weaker genetic effect in hand OA. Hand OA risk is conferred by homozygous state for the IL1B haplotype characteristic of the extended risk haplotype.