Correlation of fractalkine concentrations in serum and synovial fluid with the radiographic severity of knee osteoarthritis

Synovial Fluid Biomarkers in Knee Osteoarthritis: A Systematic Review and Quantitative Evaluation Using BIPEDs Criteria

OBJECTIVE

The aim of this systematic review was to analyze the evidence about the efficacy of the several synovial fluid (SF) biomarkers proposed for knee osteoarthritis (OA), categorizing them by both molecular characteristics and clinical use according to the BIPEDs criteria, to provide a comprehensive and structured overview of the current literature.

DESIGN

A systematic review was performed in May 2020 on PubMed, Cochrane Library, and Embase databases about SF biomarkers in patients with knee OA. The search was limited to articles in the last 20 years on human studies, involving patients with knee OA, reporting SF biomarkers. The evidence for each selected SF biomarker was quantified according to the 6 categories of BIPEDs classification.

RESULTS

A total of 159 articles were included in the qualitative data synthesis and 201 different SF biomarkers were identified. Among these, several were investigated multiple times in different articles, for a total of 373 analyses. The studies included 13,557 patients with knee OA. The most promising SF biomarkers were C4S, IL-6, IL-8, Leptin, MMP-1/3, TIMP-1, TNF-α, and VEGF. The "burden of disease" and "diagnostic" categories were the most represented with 132 and 106 different biomarkers, respectively.

CONCLUSIONS

The systematic review identified numerous SF biomarkers. However, despite the high number of studies on the plethora of identified molecules, the evidence about the efficacy of each biomarker is supported by limited and often conflicting findings. Further research efforts are needed to improve the understanding of SF biomarkers for a better management of patients with knee OA.

Soluble biological markers in osteoarthritis

In recent years, markers research has focused on the structural components of cartilage matrix. Specifically, a second generation of degradation markers has been developed against type II collagen neoepitopes generated by specific enzymes. A particular effort has been made to measure the degradation of minor collagens III and X of the cartilage matrix. However, because clinical data, including longitudinal controlled studies, are very scarce, it remains unclear whether they will be useful as an alternative to or in combination with current more established collagen biological markers to assess patients with osteoarthritis (OA). In addition, new approaches using high-throughput technologies allowed to detect new types of markers and improve the knowledge about the metabolic changes linked to OA. The relative advances coming from phenotype research are a first attempt to classify the heterogeneity of OA, and several markers could improve the phenotype characterization. These phenotypes could improve the selection of patients in clinical trials limiting the size of the studies by selecting patients with OA characteristics corresponding to the metabolic pathway targeted by the molecules evaluated. In addition, the inclusion of rapid progressors only in clinical trials would facilitate the demonstration of efficacy of the investigative drug to reduce joint degradation. The combination of selective biochemical markers appears as a promising and cost-effective approach to fulfill this unmet clinical need. Among the various potential roles of biomarkers in OA, their ability to monitor drug efficacy is probably one of the most important, in association with clinical and imaging parameters. Biochemical markers have the unique property to detect changes in joint tissue metabolism within a few weeks.

Elevated inflammatory proteins in cerebrospinal fluid from patients with painful knee osteoarthritis are associated with reduced symptom severity

Neuroinflammation and periphery-to-CNS neuroimmune cross-talk in patients with painful knee osteoarthritis (OA) are poorly understood. We utilized proximity extension assay to measure the level of 91 inflammatory proteins in CSF and serum from OA patients and controls. The patients had elevated levels of 48 proteins in CSF indicating neuroinflammation. Ten proteins were correlated between CSF and serum and potentially involved in periphery-to-CNS neuroimmune cross-talk. Seven CSF proteins, all with previously reported neuroprotective effects, were associated with lower pain intensity and milder knee-related symptoms. Our findings indicate that neuroinflammation in OA could be protective and associated with less severe symptoms.

Comparative Analysis of the Occurrence and Role of CX3CL1 (Fractalkine) and Its Receptor CX3CR1 in Hemophilic Arthropathy and Osteoarthritis

Objective

Hemophilic arthropathy is characterized by recurrent bleeding episodes in patients with hemophilia leading to irreversible joint degeneration. The involvement of CX3CL1 (fractalkine) and its receptor CX3CR1 was observed in the pathogenesis of numerous arthritis-associated diseases. Taking this into account, we have presented a study investigating the role of the CX3CL1/CX3XR1 axis in the course of hemophilic arthropathy, including the CX3CL1-dependent expression of CD56⁺, CD68⁺, and CD31⁺ cells along with evaluation of articular cartilage and synovial membrane morphology.

Methods

The study was carried out using cases (n = 20) of end-stage hemophilic arthropathy with a severe type of hemophilia A and control cases (n = 20) diagnosed with osteoarthritis. The biofluids including blood serum and synovial fluid were obtained intraoperatively for the evaluation of CX3CL1 using the ELISA test. Tissue specimens including articular cartilage and synovial membrane were similarly collected during surgery and stained immunohistologically using selected antibodies including anti-CX3CR1, anti-CD56, anti-CD68, and anti-CD31. Additionally, the analysis included the assessment of articular cartilage, synovial membrane, and blood vessel morphology.

Results

In our study, we have documented increased average concentration of CX3CL1 in the blood serum of the study group (7.16 ± 0.53 ng/ml) compared to the control group (5.85 ± 0.70 ng/ml) without statistically significant difference in synovial fluid concentration at the same time. We have observed an increased macrophage presence with more marked proliferation and fibrosis of the synovial membrane in the study group. Remaining results such as expression of CX3CR1 presence of NK cells and larger surface area of blood vessels within the synovial membrane were noted also without statistical significance.

Conclusions

This study has demonstrated collective CX3CL1/CX3CR1 axis involvement in hemophilic arthropathy pathogenesis introducing new interesting diagnostics and a therapeutic target.

Rationale for and clinical development of anti-fractalkine antibody in rheumatic diseases

Introduction: Rheumatic diseases are inflammatory diseases that damage target organs via multiple subsets of immune cells. Fractalkine (FKN) acts as chemoattractant as well as adhesion molecule. It contributes to the pathogenesis of rheumatoid arthritis (RA) and other rheumatic diseases through multiple mechanisms: the migration of monocytes and cytotoxic effector T cells, the proliferation and activation of fibroblast-like synoviocytes, angiogenesis, and osteoclastogenesis. FKN has potential as a new therapeutic target, and clinical trials on anti-FKN monoclonal antibodies for RA are ongoing. FKN-targeted therapy has been developed and a humanized anti-FKN monoclonal antibody is currently being tested in phase 2 clinical trials. Areas covered: This review summarizes accumulated evidence on the involvement of FKN in RA and other rheumatic diseases, including systemic lupus erythematosus (SLE), systemic sclerosis, inflammatory myositis, Sjögren's syndrome (SS), osteoarthritis, and systemic vasculitis. Expert opinion: A phase 1/2a clinical trial on anti-FKN demonstrated its safety, tolerability, and clinical efficacy. Anti-FKN therapy has potential in the treatment of atherosclerosis and interstitial lung diseases associated with RA. Based on recent findings, other rheumatic diseases, including SLE, polymyositis/dermatomyositis, and SS, may also be treated using anti-FKN therapy.

Formononetin Antagonizes the Interleukin-1β-Induced Catabolic Effects Through Suppressing Inflammation in Primary Rat Chondrocytes

In the present study, we demonstrated the anti-catabolic effects of formononetin, a phytoestrogen derived from herbal plants, against interleukin-1β (IL-1β)-induced severe catabolic effects in primary rat chondrocytes and articular cartilage. Formononetin did not affect the viability of primary rat chondrocytes in both short- (24 h) and long-term (21 days) treatment periods. Furthermore, formononetin effectively antagonized the IL-1β-induced catabolic effects including the decrease in proteoglycan content, suppression of pericellular matrix formation, and loss of proteoglycan through the decreased expression of cartilage-degrading enzymes like matrix metalloproteinase (MMP)-13, MMP-1, and MMP-3 in primary rat chondrocytes. Moreover, catabolic oxidative stress mediators like nitric oxide, inducible nitric oxide synthase, cyclooxygenase-2, and prostaglandin E₂ were significantly downregulated by formononetin in primary rat chondrocytes treated with IL-1β. Sequentially, the upregulation of pro-inflammatory cytokines (like IL-1α, IL-1β, IL-6, and tumor necrosis factor α), chemokines (like fractalkine, monocyte chemoattractant protein-1, and macrophage inflammatory protein-3α), and vascular endothelial growth factor were significantly downregulated by formononetin in primary rat chondrocytes treated with IL-1β. These data suggest that formononetin may suppress IL-1β-induced severe catabolic effects and osteoarthritic condition. Furthermore, formononetin may be a promising candidate for the treatment and prevention of osteoarthritis.

Overexpression of fractalkine and its histopathological characteristics in primary pterygium

PURPOSE

This study aimed to evaluate the differences in the expressions of fractalkine in normal bulbar conjunctiva and primary pterygium tissues.

METHODS

The study included 48 patients who had been operated on for primary pterygium. Histopathologically, the presence of epithelial atypia, epithelial hyperplasia, goblet cell hyperplasia, epithelial lymphocytic exocytosis, stromal inflammation, mast cell count, and stromal vascularity were evaluated in the primary pterygium tissues. An immunohistochemical fractalkine stain was applied to the primary pterygium tissue samples and normal bulbar conjunctival tissue samples.

RESULTS

Primary pterygium and normal bulbar conjunctival tissue samples were histopathologically analyzed. Epithelial atypia, epithelial hyperplasia, epithelial lymphocytic exocytosis, stromal inflammation, stromal vascularity, and mast cell count were found to be significantly higher in the primary pterygium (p = 0.001, p = 0.002, p = 0.024, p = 0.007, p = 0.024, and p = 0.013, respectively). When evaluated in terms of fractalkine expression, the epithelial, vascular endothelial, and inflammatory cells were significantly higher in the primary pterygium (p ≤ 0.001, p = 0.002, p = 0.001, respectively). Moreover, compared to the normal bulbar conjunctiva, Ki-67 expression was significantly higher in the primary pterygium tissue samples.

CONCLUSION

Fractalkine might play a key role in the etiopathogenesis of pterygium. Fractalkine may be important in developing new treatment approaches.

Synovial fluid monocyte/macrophage subsets and their correlation to patient-reported outcomes in osteoarthritic patients: a cohort study

BACKGROUND

Chronic, low-grade inflammation of the synovium (synovitis) is a hallmark of osteoarthritis (OA), thus understanding of OA immunobiology, mediated by immune effectors, is of importance. Specifically, monocytes/macrophages (MΦs) are known to be abundantly present in OA joints and involved in OA progression. However, different subsets of OA MΦs have not been investigated in detail, especially in terms of their relationship with patient-reported outcome measures (PROMs). We hypothesized that levels of synovial fluid (SF) MΦ subsets are indicative of joint function and quality of life in patients with OA, and can therefore serve as biomarkers and therapeutic targets for OA.

METHODS

In this cohort study, synovial fluid leukocytes (SFLs, N = 86) and peripheral blood mononuclear cells (n = 53) from patients with knee OA were characterized. Soluble MΦ receptors and chemokine (sCD14, sCD163, CCL2, CX3CL1) levels were detected in SF using immunoassays. Linear models, adjusted for sex, age and body mass index, were used to determine associations between SF MΦs and soluble factors with PROMs (N = 83). Pearson correlation was calculated to determine correlation between MΦ subsets, T cells and soluble factors.

RESULTS

SF MΦs were the most abundant SFLs. Within these, the double-positive CD14+CD16+-MΦ subset is enriched in knee OA SF compared to the circulation. Importantly, MΦ subset ratios correlated with PROMs, specially stiffness, function and quality of life. Interestingly, the SF CD14+CD16+-MΦ subset ratio correlated with SF chemokine (C-C motif) ligand 2 (CCL2) levels but not with levels of sCD163 or sCD14; we found no association between PROMs and either SF CCL2, sCD163, sCD14 or CX3CL1 (which was below detection levels). All SF MΦs displayed high levels of HLA-DR, suggesting an activated phenotype. Correlation between OA SF MΦ subsets and activated CD4+ T cell subsets suggests modulation of CD4+ T cell activation by MΦs.

CONCLUSION

SF MΦ subsets are associated with knee OA PROMs and display an activated phenotype, which may lead to modulation of CD4+ T cell activation. Knee OA SF MΦ subsets could serve as knee OA function biomarkers and as targets of novel therapeutics.

Placental fractalkine immunoreactivity in preeclampsia and its correlation with histopathological changes in the placenta and adverse pregnancy outcomes. J Matern Fetal Neonatal Med 2018;33:806-815. [PMID: 30049235 DOI: 10.1080/14767058.2018.1505854]

Introduction: Preeclampsia is a systemic inflammatory disorder and a major cause of maternal and fetal mortality. Fractalkine (CX3CL1) is a member of the chemokine family with multiple functions in the organization of the immune system. It is up-regulated in inflammatory disorders. During inflammation, fractalkine enhances tissue destruction and inflammatory cell invasion. We aimed to investigate the alteration of fractalkine in the placental tissues of pregnant women with preeclampsia and the correlation of this alteration with clinicopathological variables.Materials and methods: Alteration of fractalkine in placental tissue specimens was determined immunohistochemically in 84 pregnant women: 33 women with mild preeclampsia, 19 women with severe preeclampsia, and 30 women with normal pregnancy. Preeclampsia was diagnosed using current guidelines of the American College of Obstetricians and Gynecologists.Results: Pregnant women with mild and severe preeclampsia revealed significantly higher fractalkine expression in syncytiotrophoblast cells than in the normotensive group (p = .0051 and .0001, respectively). The expression of fractalkine in preeclampsia was positively correlated with clinical parameters including the presence of intrauterine growth restriction, systolic and diastolic blood pressure, and 24-h urine protein, whereas it was negatively correlated with plasma albumin levels and placental weight. Additionally, the pathological changes in the placenta-including the presence of syncytiotrophoblast basement membrane thickening, increased number of syncytial knots, and vascularization of terminal villi were significantly correlated with fractalkine expression in pregnant women with preeclampsia.Conclusions: Overexpression of fractalkine in pregnant women with preeclampsia, as well as the correlation between fractalkine expression and poor pregnancy outcomes and placental histopathological changes may be associated with the underlying mechanisms of preeclampsia.

CX3CL1 promotes MMP-3 production via the CX3CR1, c-Raf, MEK, ERK, and NF-κB signaling pathway in osteoarthritis synovial fibroblasts

Background

Osteoarthritis (OA) is a degenerative joint disease that affects the cartilage, synovium, and subchondral bone and is the leading cause of disability in older populations. Specific diagnostic biomarkers are lacking; hence, treatment options for OA are limited. Synovial inflammation is very common in OA joints and has been associated with both OA’s symptoms and pathogenesis. Confirming the role of the synovium in OA pathogenesis is a promising strategy for mitigating the symptoms and progression of OA. CX3CL1 is the only member of the CX3C class of chemokines that combines the properties of chemoattractants and adhesion molecules. CX3CL1 levels in the synovium and serum were both discovered to be positively associated with OA pathogenesis. CX3CL1 and its receptor CX3CR1 belong to a family of G protein-coupled receptors. Matrix metalloproteinases (MMPs), which are responsible for matrix degradation, play a crucial role in OA progression. The relationship between CX3CL1 and MMPs in the pathophysiology of OA is still unclear.

Methods

CX3CL1-induced MMP-3 production was assessed with quantitative real-time PCR and ELISA. The mechanisms of action of CX3CL1 in different signaling pathways were studied using western blot analysis, quantitative real-time PCR and ELISA. Neutralization antibodies of integrin were achieved to block the CX3CR1 signaling pathway. Luciferase assays were used to study NF-κB promoter activity.

Results

We investigated the signaling pathway involved in CX3CL1-induced MMP-3 production in osteoarthritis synovial fibroblasts (OASFs). CX3CL1 was found to induce MMP-3 production in a concentration-dependent and time-dependent manner. Using pharmacological inhibitors and CX3CR1 small interfering RNA to block CX3CR1 revealed that the CX3CR1 receptor was involved in the CX3CL1-mediated upregulation of MMP-3. CX3CL1-mediated MMP-3 production was attenuated by c-Raf inhibitors (GW5074) and MEK/ERK inhibitors (PD98059 and U0126). The OASFs were stimulated using CX3CL1-activated p65 phosphorylation.

Conclusions

Our results demonstrate that CX3CL1 activates c-Raf, MEK, ERK, and NF-κB on the MMP-3 promoter through CX3CR1, thus contributing to cartilage destruction during OA.

Fractalkine (CX3CL1): a biomarker reflecting symptomatic severity in patients with knee osteoarthritis

BACKGROUND

Elevated serum and synovial fluid (SF) fractalkine (CX3CL1) levels have been detected in patients with knee osteoarthritis (OA). The current study was carried out to investigate the association between serum and SF fractalkine levels with symptomatic severity in patients with knee OA.

METHOD

One hundred ninety-three patients with OA and 182 healthy controls were enrolled in this study. The symptomatic severity was assessed by the Western Ontario McMaster University Osteoarthritis scores.

RESULTS

Fractalkine levels in SF and serum were both positively associated with self-reported greater pain and physical disability.

CONCLUSIONS

Fractalkine in SF and serum may serve as a biomarker for reflecting symptomatic severity. Therapeutic interventions that target fractalkine signaling pathways to delay OA-related symptoms deserve further study.

Plasma and Synovial Fluid CXCL12 Levels Are Correlated With Disease Severity in Patients With Knee Osteoarthritis

BACKGROUND

The aim is to determine whether CXC chemokine ligand-12 (CXCL12) levels in plasma and synovial fluid (SF) of patients with knee osteoarthritis (OA) are correlated with the disease severity. In addition, we set out to investigate whether a peripheral blood test can avoid aspirating patients to determine CXCL12 levels.

METHODS

This study consisted of 244 patients with knee OA and 244 age- and gender-matched healthy controls. Osteoarthritis progression was classified based on Kellgren-Lawrence (KL) by evaluating radiographic changes observed in anteroposterior knee radiography. The CXCL12 levels in the plasma and SF were measured by a quantitative sandwich enzyme-linked immunosorbent assay.

RESULTS

Plasma CXCL12 levels were higher in OA patients as compared with controls (P < .0001). There was a positive correlation between levels of CXCL12 and grade (P < .0001). Base on the receiver operating characteristic curve, the optimal cutoff value of plasma CXCL12 levels as an indicator for screening of OA was estimated to be 5.5 ng/mL, which yielded a sensitivity of 78.4% and a specificity of 80.2%, with the area under the curve at 0.850 (95% confidence interval [CI], 0.816-0.889; P < .0001). In multivariate analysis, there was an increased risk of active OA associated with plasma CXCL12 levels ≥10.5 ng/mL (odds ratio, 6.76; 95% CI, 3.88-12.53; P < .0001) after adjusting for possible confounders. Similarly, there was an increased risk of active OA associated with SF CXCL12 levels ≥15.0 ng/mL (odds ratio, 8.45; 95% CI, 3.23-18.22; P < .0001) after adjusting for possible confounders.

CONCLUSION

The CXCL12 levels in the plasma and SF may serve as effective biomarkers for the severity of OA.

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.

The chemokine CX3CL1 (fractalkine) and its receptor CX3CR1: occurrence and potential role in osteoarthritis

Chemokines are molecules able to induce chemotaxis of monocytes, neutrophils, eosinophils, lymphocytes and fibroblasts. The complex chemokine acts in many physiological and pathological phenomena, including those occurring in the articular cartilage. To date, chemokine CX3CL1 (fractalkine) is the only member of the CX3C class of chemokines with well-documented roles in endothelial cells. CX3CL1 is a unique chemokine that combines properties of chemoattractant and adhesion molecule. The main roles of CX3CL1 include promotion of leukocyte binding and adhesion as well as activation of the target cells. The soluble chemokine domain of CX3CL1 is chemotactic for T cells and monocytes. CX3CL1 acts via its receptor, CX3CR1, which belongs to a family of G protein-coupled receptors. Stimulation of CX3CR1 activates both CX3CL1-dependent and integrin-dependent migrations of cells with synergistically augmented adhesion. Genetic polymorphisms of CX3CR1 may significantly modify the biological roles of CX3CL1, especially in pathologic conditions. Osteoarthritis (OA) is the most common joint disease, affecting approximately 7–8 % of the general population. Development of OA is largely driven by low-grade local background inflammation involving chemokines. The importance of CX3CL1/CX3CR1 signalling in the pathophysiology of OA is still under investigation. This paper, based on a review of the literature, updates and summarises the current knowledge about CX3CL1/CX3CR1 in OA and indicates possible interactions with a potential for therapeutic targeting.