An explorative study comparing levels of soluble mediators in control and osteoarthritic synovial fluid

Alleviating osteoarthritis-induced damage through extracellular vesicles derived from inflammatory chondrocytes

The role of extracellular vesicles (EVs) derived from inflammatory chondrocytes in EV-based therapy for osteoarthritis (OA) has received little attention. We examined the effects of EVs derived from both normal rat chondrocytes (nEVs) and IL-1β-treated rat chondrocytes (iEVs) on IL-1β-treated rat chondrocytes, macrophages, and osteoblasts, alongside mRNA-seq and miRNA-seq analyses of both them. Additionally, nEVs and iEVs were administered intra-articularly in the joints of rat models subjected to anterior cruciate ligament transection (ACLT), and the morphological alterations across the joints were assessed. These findings indicated that iEVs, compared with nEVs, significantly enhanced collagen II synthesis in IL-1β-treated chondrocytes, accompanied by marked increases in ER stress and autophagy. In comparison to nEVs, iEVs exhibited a greater effect on facilitating M2-type macrophage polarization while simultaneously diminishing M1-type polarization, a process likely mediated by the downregulation of chemotactic cytokines such as Cxcl10, Ccl5, Cxcl9, Cxcl1, and Cxcl11. iEVs exerted a more pronounced influence on the phenotypic characteristics of IL-1β-treated osteoblasts than nEVs. In the ACLT-rat model, iEVs, akin to nEVs, effectively mitigated articular cartilage degradation. However, there was no significant difference in OARSI Scores between the two groups, despite iEVs exerting a greater effect on increasing hyaline cartilage thickness and proteoglycan content. iEVs were superior to nEVs in attenuating synovium inflammation and promoting trabecula formation in the femur subchondral bone. Consequently, iEVs, akin to nEVs, significantly alleviated OA-induced damage. Moreover, iEVs outperformed nEVs in certain aspects, notably in augmenting hyaline cartilage, reducing synovium inflammation, and promoting trabecular formation in the subchondral bone during the early stage of OA.

The Effect of Intravascular Laser Irradiation of Blood on Serum Biomarkers and Clinical Outcome in Knee Osteoarthritis Patients: A Double-Blind Randomized Control Trial

Knee osteoarthritis (OA) is a prevalent degenerative joint disease globally, causing pain, stiffness, and disability. Intravascular laser irradiation of blood (ILIB) has been used for chronic pain and musculoskeletal disease. However, evidence on the clinical benefits and serum biomarkers post-ILIB therapy in knee OA is insufficient. We designed a double-blind randomized controlled trial to evaluate the clinical and biological outcomes of ILIB therapy for knee OA. Seventeen patients with knee OA were randomly assigned to the ILIB and control groups. The outcomes included the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Scale, visual analog scale, and biomarker analysis of interleukin (IL)-6, IL-13, IL-1β, epidermal growth factor, macrophage inflammatory protein-1β, and eotaxin. The measurements were performed at baseline and three days, one month, and three months post-intervention. The ILIB group showed a significant improvement in the WOMAC-pain score at one month of follow-up than the control group. IL-1β levels reduced significantly on day three, one month, and three months, and IL-13 levels reduced on day three and three months during follow-up in the ILIB group. ILIB therapy reduced knee OA pain for one month and significantly reduced serum IL-1β and IL-13 levels, suggesting potential for pain management.

Pararamosis, a Neglected Tropical Disease Induced by Premolis semirufa Caterpillar Toxins: Investigating Their Effects on Synovial Cell Inflammation

Pararamosis, also known as Pararama-associated phalangeal periarthritis, is a neglected tropical disease primarily affecting rubber tappers in the Amazon region. It is caused by contact with the urticating hairs of the Premolis semirufa moth caterpillar, which resides in rubber plantations. The condition is marked by the thickening of the articular synovial membrane and cartilage impairment, features associated with chronic synovitis. Given the significance of synovial inflammation in osteoarticular diseases, in this study, the role of synoviocytes and their interactions with macrophages and chondrocytes are examined when stimulated by Pararama toxins. Synoviocytes and macrophages treated with Pararama hair extract showed an increased production of cytokines IL-6, IL-1β, and TNF-α, indicating a direct effect on these cells. In cocultures, there was a significant rise in inflammation, with levels of IL-1β, IL-6, and chemokines CCL2, CCL5, and CXCL8 increasing up to seven times compared to monocultures. Additionally, matrix-degrading enzymes MMP-1 and MMP-3 were significantly elevated in cocultures. Chondrocytes exposed to the extract also produced IL-6, CCL2, and CCL5, and in cocultures with synoviocytes, there was a notable increase in IL-6, CCL5, and CXCL8, as well as a doubling of MMP-1 and MMP-3 levels. These findings underscore the critical role of cell crosstalk in the inflammatory and catabolic processes associated with pararamosis and demonstrate how Pararama hair extract can influence factors affecting cartilage health, providing valuable insights into this condition.

Cross-talk of inflammation and cellular senescence: a new insight into the occurrence and progression of osteoarthritis

Osteoarthritis (OA) poses a significant challenge in orthopedics. Inflammatory pathways are regarded as central mechanisms in the onset and progression of OA. Growing evidence suggests that senescence acts as a mediator in inflammation-induced OA. Given the lack of effective treatments for OA, there is an urgent need for a clearer understanding of its pathogenesis. In this review, we systematically summarize the cross-talk between cellular senescence and inflammation in OA. We begin by focusing on the mechanisms and hallmarks of cellular senescence, summarizing evidence that supports the relationship between cellular senescence and inflammation. We then discuss the mechanisms of interaction between cellular senescence and inflammation, including senescence-associated secretory phenotypes (SASP) and the effects of pro- and anti-inflammatory interventions on cellular senescence. Additionally, we focus on various types of cellular senescence in OA, including senescence in cartilage, subchondral bone, synovium, infrapatellar fat pad, stem cells, and immune cells, elucidating their mechanisms and impacts on OA. Finally, we highlight the potential of therapies targeting senescent cells in OA as a strategy for promoting cartilage regeneration.

Distinct patterns of cytokines, chemokines, and growth factors in synovial fluid after ACL injury in comparison to osteoarthritis

This study analyzed knee synovial fluid after anterior cruciate ligament (ACL) tear and in osteoarthritis (OA) to test the hypotheses that concentrations of cytokines, chemokines, and growth factors differ (a) by diagnosis and (b) after ACL tear by time from injury and presence/absence of concomitant meniscus tear. Synovial fluid samples were collected from two groups, ACL tears (with or without meniscus tear) (N = 13) and Kellgren-Lawrence grade 3 and 4 OA (N = 16), undergoing clinically indicated aspiration of the knee joint. Multiple cytokines, chemokines, and growth factors were assessed using a multiplexed 45-protein panel. Comparisons were made for the concentrations of all molecules between ACL tear and OA patients, isolated versus combined ACL and meniscus tears, and categorized by time from injury: acute or early subacute (<15 days, N = 8) versus late subacute or chronic (>15 days and <3 months, N = 5). ACL tear patients have higher levels of six molecules (IL-4, IL-5, IL-13, PlGF-1, bNGF, TNF-α) in knee synovial fluid compared to OA patients. Isolated ACL tears express higher levels of IL-4, IL-13 and IFN-γ and lower levels of IL-7 than ACL tears with a concomitant meniscus tear. SDF-1α, PlGF-1, IL-1RA, HGF, bNGF, and BDNF levels are elevated immediately after injury and drop off significantly in the late subacute phase (after 15 days). Synovial fluid from knees with ACL tears have elevated metabolic activity compared to knees with OA. The cytokine profiles after ACL tears are influenced by the time from injury and the presence of meniscus tears. These findings offer valuable insights into the levels of cytokines, chemokines, and growth factors in the knee after ACL injury, information which may have important implications for the diagnosis, prognosis and treatment of this common pathology.

Causal relationships between systemic inflammatory cytokines and adhesive capsulitis: a bidirectional Mendelian randomization study

Background

Mounting evidence suggests a connection between inflammatory cytokines and adhesive capsulitis (AC). However, the specific systemic inflammatory cytokines contributing to AC have not been clearly identified. This study employed Mendelian randomization (MR) to explore the causal relationships between 41 inflammatory cytokines and AC.

Methods

In this bidirectional, two-sample MR analysis, genetic variations associated with AC were derived from a comprehensive genome-wide association study (GWAS). The inflammatory cytokines data were sourced from a GWAS summary involving 8,293 healthy participants. The primary MR method employed was inverse variance weighting, supplemented by MR-Egger, weighted median, and MR-pleiotropy residual sum and outlier for sensitivity analysis. Heterogeneity was assessed using Cochran's Q test, and the MR results were validated using the leave-one-out method.

Results

Elevated levels of interferon gamma-induced protein 10 (IP-10) (odds ratio (OR) = 1.086, 95% confidence interval (CI) = 1.002-1.178) and regulated on activation, normal T cell expressed and secreted (RANTES) (OR = 1.107, 95% CI = 1.026-1.195) were linked to an increased risk of AC. Increased levels of stromal cell-derived factor-1 alpha (SDF-1α) (OR = 0.879, 95% CI = 0.793-0.974) and tumor necrosis factor-alpha (TNF-α) (OR = 0.911, 95% CI = 0.831-0.999) were associated with a reduced AC risk. Moreover, genetically predicted AC exhibited associations with elevated cutaneous T cell attracting (CTACK) levels (OR = 1.202, 95% CI = 1.007-1.435) and diminished levels of interleukin-17 (IL-17) (OR = 0.678, 95% CI = 0.518-0.888) and interleukin-5 (IL-5) (OR = 0.786, 95% CI = 0.654-0.944), as confirmed through inverse-variance weighted (IVW) methods.

Conclusion

The present study successfully establishes a causal association between genetically proxied circulating levels of IP-10, RANTES, SDF-1α, and TNF-α and the risk of AC. Additionally, AC contributes to an increase in CTACK and a decrease in IL-17 and IL-5. This significant finding not only enhances the understanding of the pathogenesis of AC but also holds promise for the development of effective clinical management strategies.

Olokizumab in patients with inflammatory phenotype of osteoarthritis, treatment experience

   Objective: to investigate the efficacy and safety of olokizumab (OKZ) in patients with knee osteoarthritis (OA) with synovitis, persistent pain and ineffectiveness of previous conservative therapy.

   Material and methods. The study included 15 patients with stage II–III knee OA who fulfilled the ACR criteria and had pain ≥50 mm on a visual analogue scale (VAS), synovitis and treatment failure. The age of patients ranged from 54 to 75 years; the duration of the disease was from 1 to 23 years. The duration of the study was 12 weeks, during which the patients received 3 subcutaneous injections of OKZ at a dose of 64 mg. The effectiveness of the treatment was assessed by the dynamics of pain intensity according to VAS, WOMAC and KOOS indices, the values of the DN4 questionnaire and the quality of life according to EQ-5D. In addition, the general assessment of the patient's health (GHA) according to VAS, the assessment of treatment efficacy by doctor and patient and the need for non-steroidal anti-inflammatory drugs (NSAIDs) were considered. All patients underwent laboratory testing.

   Results and discussion. During treatment, there was a significant decrease in pain intensity according to VAS, a statistically significant improvement in the KOOS and WOMAC indices (p<0.05), quality of life according to the EQ-5D questionnaire and GHA. Patients and doctors rated the treatment results very positively: an improvement or significant improvement was observed in 92.3% of cases. Adverse events were identified in 4 patients, which in 2 cases served as the reason for discontinuation of OKZ treatment and termination of participation in the study. During treatment with OKZ, a statistically significant decrease in CRP and ESR values, an increase in the concentration of interleukin 6 (p = 0.003), COMP (p = 0.03) and PIINP (p = 0.01) were observed.

   Conclusion. The results obtained suggest a significant symptomatic and anti-inflammatory effect of OKZ in patients with the inflammatory phenotype of OA.

The effect of plasma cytokines on the expression of adiponectin and its receptors in the synovial membrane of joints and the infrapatellar fat pad in patients with rheumatoid arthritis and osteoarthritis

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that leads to joint destruction. Numerous pro-inflammatory mediators, including adipokines, play an important role in the pathogenesis of RA.

OBJECTIVE

The aim of the study was to investigate the relationships between selected plasma cytokines and expression of adiponectin and its receptors in the synovium and the infrapatellar fat pad in patients with RA and osteoarthritis (OA).

METHODS

Blood, synovium and fat pad samples from 18 patients with RA and 18 with OA were collected during joint replacement surgery. Spearman rank correlations between plasma concentrations of selected cytokines (IL-1β, IL-2, IL-4, IL-6, IL-7, IL-8, IL-10, IL-12 p40, IL-13, IL-17, G-CSF and GM-CSF) and the expression of adiponectin and its receptors were determined. Plasma levels of cytokines were determined using a magnetic bead-based multiplex assay, mRNA expression of adiponectin and its receptors were determined by real-time PCR.

RESULTS

In OA patients, there were significant positive correlations between adiponectin expression in the synovial membrane and plasma levels of IL-1β, IL-4, G-CSF and GM-CSF, as well as a significant positive correlation between adiponectin expression in the fat pad and plasma levels of GM-CSF. In addition, OA patients showed significant negative correlations between AdipoR1 and AdipoR2 expression in the synovial membrane and plasma IL-6 levels, as well as between AdipoR2 expression in the synovial membrane and plasma MCP-1 and TNF-α levels. In patients with RA, there were no significant correlations between adiponectin expression in the synovial membrane and infrapatellar fat pad and plasma levels of the cytokines studied. In addition, RA patients showed a statistically significant negative correlation between AdipoR1 expression in the synovial membrane and plasma levels of TNF-α, IL-7, IL-12 and IL-13, and a significant negative correlation between AdipoR1 expression in the infrapatellar fat pad and plasma levels of IL-1β.

CONCLUSIONS

Adiponectin and its receptors showed the correlations with several plasma cytokines, however, a thorough understanding of the role of adiponectin in RA and OA requires further investigation.

Polymorphism of Genes Encoding Inflammatory Interleukins and the Risk of Anterior Cruciate Ligament Injury: A Systematic Review and Meta-Analysis

Sport injuries, including the anterior crucial ligament rupture (ACLR) seem to be related to complex genetic backgrounds, including the genes responsible for inflammatory response. This review and meta-analysis investigated the contribution of the polymorphisms of genes encoding inflammatory cytokines and their receptors to the risk of ACLR. The scientific databases Science Direct, EBSCO host, Scopus, PubMed, and Google Scholar were screened (completed on 14 June 2023) according to the established inclusion/exclusion criteria (only fully accessible, original, human case-control studies written in English concerning the effect of interleukin genes' polymorphisms on the occurrence of ACL injury were included) and statistical meta-analysis using R version 4.0.3 was performed. The PRISMA methodology was used to review articles. The review protocol was registered under the number CRD42024514316 in the Prospero database. Eighty-nine studies were identified and narrowed down to three original case-control studies used for the meta-analysis. The studies analyzed Polish, South African, and Swedish cohorts, altogether 1282 participants. The candidate polymorphisms indicated in the studies involved IL6 rs1800795, IL6R rs2228145 and IL1B rs16944. The systematic review showed the relationships between IL6 rs1800795 polymorphism and ACLR in the Polish subpopulation, and IL6R rs2228145 and IL1B rs16944 in the South African subpopulations. The meta-analysis revealed that the IL6 rs1800795 CG genotype was over-represented (OR = 1.30, 95% CI 1.02-1.66), while the CC genotype was under-represented (OR = 0.75, 95% CI 0.54-1.03) in ACLR subjects, but no significant impact of IL6R rs2228145 was shown. Additionally, a tendency of the IL1B rs16944 CT genotype to be protective (OR 0.89, 95% CI 0.70-1.14), while the TT to be a risk genotype (OR 1.19, 95% CI 0.84-1.68) was observed. Thus, the relationship between the interleukin receptor IL6R rs2228145 and ACLR risk was not confirmed. However, the impact of genes coding pleiotropic IL6 rs1800795 on the incidences of ACLR was clear and the effect of pro-inflammatory IL1B rs16944 was possible.

Enzymatic digestion does not compromise sliding-mediated cartilage lubrication

Articular cartilage's remarkable low-friction properties are essential to joint function. In osteoarthritis (OA), cartilage degeneration (e.g., proteoglycan loss and collagen damage) decreases tissue modulus and increases permeability. Although these changes impair lubrication in fully depressurized and slowly slid cartilage, new evidence suggests such relationships may not hold under biofidelic sliding conditions more representative of those encountered in vivo. Our recent studies using the convergent stationary contact area (cSCA) configuration demonstrate that articulation (i.e., sliding) generates interfacial hydrodynamic pressures capable of replenishing cartilage interstitial fluid/pressure lost to compressive loading through a mechanism termed tribological rehydration. This fluid recovery sustains in vivo-like kinetic friction coefficients (µk<0.02 in PBS and <0.005 in synovial fluid) with little sensitivity to mechanical properties in healthy tissue. However, the tribomechanical function of compromised cartilage under biofidelic sliding conditions remains unknown. Here, we investigated the effects of OA-like changes in cartilage mechanical properties, modeled via enzymatic digestion of mature bovine cartilage, on its tribomechanical function during cSCA sliding. We found no differences in sliding-driven tribological rehydration behaviors or µk between naïve and digested cSCA cartilage (in PBS or synovial fluid). This suggests that OA-like cartilage retains sufficient functional properties to support naïve-like fluid recovery and lubrication under biofidelic sliding conditions. However, OA-like cartilage accumulated greater total tissue strains due to elevated strain accrual during initial load application. Together, these results suggest that elevated total tissue strains-as opposed to activity-mediated strains or friction-driven wear-might be the key biomechanical mediator of OA pathology in cartilage. STATEMENT OF SIGNIFICANCE: Osteoarthritis (OA) decreases cartilage's modulus and increases its permeability. While these changes compromise frictional performance in benchtop testing under low fluid load support (FLS) conditions, whether such observations hold under sliding conditions that better represent the joints' dynamic FLS conditions in vivo is unclear. Here, we leveraged biofidelic benchtop sliding experiments-that is, those mimicking joints' native sliding environment-to examine how OA-like changes in mechanical properties effect cartilage's natural lubrication. We found no differences in sliding-mediated fluid recovery or kinetic friction behaviors between naïve and OA-like cartilage. However, OA-like cartilage experienced greater strain accumulation during load application, suggesting that elevated tissue strains (not friction-driven wear) may be the primary biomechanical mediator of OA pathology.

Knee Osteotomy Decreases Joint Inflammation Based on Synovial Histology and Synovial Fluid Analysis

PURPOSE

To examine the biological changes in the joints of patients with knee osteoarthritis (OA) before and after around-knee osteotomy (AKO), focusing on synovial fluid (SF) and synovial pathological changes.

METHODS

Patients who underwent AKO for medial compartment knee OA between 2019 and 2021 were examined. SF and synovium were obtained at the time of AKO and plate removal after bone union (mean, 16.8 months [range: 11-38 months] postoperatively). SF volume and interleukin (IL)-6 concentrations in SF were assayed using enzyme-linked immunosorbent assay. Synovitis was assessed histologically using a semiquantitative scoring system. Macrophage infiltration was assessed by immunohistochemistry using a semiquantitative score for F4/80 expression. The M1/M2 ratio was calculated using percentage of cells positive for CD80 and CD163. The expression of proinflammatory cytokines was assessed by the percentage of IL-1β- and IL-6-positive cells. The number of vascular endothelial growth factor-positive luminal structures was counted to assess angiogenesis. The change in each parameter was compared before and after AKO using the Wilcoxon matched-pairs signed-rank test.

RESULTS

Twenty-four knees of 21 patients were included. SF volume and IL-6 concentration significantly decreased postoperatively (12.6 ± 2.1 mL vs 4.2 ± 0.6 mL; P < .0001 and 50.5 ± 8.6 pg/mL vs 20.7 ± 3.8 pg/mL; P = .0001, respectively). A significant reduction in synovitis score (P = .0001), macrophage infiltration (P < .0003), M1/M2 ratio (P < .0007), angiogenesis (P < .0001), and the percentage of IL-1β- and IL-6-positive cells in the intima (P < .008 and P < .002, respectively) was found after AKO.

CONCLUSIONS

SF volume and IL-6 concentrations in the SF decreased and inflammatory synovium pathology improved after AKO. In addition to biomechanical changes, the biological environment of the joint can be improved after AKO.

LEVEL OF EVIDENCE

Level IV, retrospective therapeutic case series.

Evaluating the potential of Vitamin D and curcumin to alleviate inflammation and mitigate the progression of osteoarthritis through their effects on human chondrocytes: A proof-of-concept investigation

Osteoarthritis (OA) is a chronic degenerative joint disorder primarily affecting the elderly, characterized by a prominent inflammatory component. The long-term side effects associated with current therapeutic approaches necessitate the development of safer and more efficacious alternatives. Nutraceuticals, such as Vitamin D and curcumin, present promising therapeutic potentials due to their safety, efficacy, and cost-effectiveness. In this study, we utilized a proinflammatory human chondrocyte model of OA to assess the anti-inflammatory properties of Vitamin D and curcumin, with a particular focus on the Protease-Activated Receptor-2 (PAR-2) mediated inflammatory pathway. Employing a robust siRNA approach, we effectively modulated the expression of PAR-2 to understand its role in the inflammatory process. Our results reveal that both Vitamin D and curcumin attenuate the expression of PAR-2, leading to a reduction in the downstream proinflammatory cytokines, such as Tumor Necrosis Factor-alpha (TNF-α), Interleukin 6 (IL-6), and Interleukin 8 (IL-8), implicated in the OA pathogenesis. Concurrently, these compounds suppressed the expression of Receptor Activator of Nuclear Factor kappa-Β Ligand (RANKL) and its receptor RANK, which are associated with PAR-2 mediated TNF-α stimulation. Additionally, Vitamin D and curcumin downregulated the expression of Interferon gamma (IFN-γ), known to elevate RANKL levels, underscoring their potential therapeutic implications in OA. This study, for the first time, provides evidence of the mitigating effect of Vitamin D and curcumin on PAR-2 mediated inflammation, employing an siRNA approach in OA. Thus, our findings pave the way for future research and the development of novel, safer, and more effective therapeutic strategies for managing OA.

The Impact of 45S5-Bioactive Glass on Synovial Cells in Knee Osteoarthritis-An In Vitro Study

Synovial inflammation in osteoarthritis (OA) is characterized by the release of cartilage-degrading enzymes and inflammatory cytokines. 45S5-bioactive glass (45S5-BG) can modulate inflammation processes; however, its influence on OA-associated inflammation has hardly been investigated. In this study, the effects of 45S5-BG on the release of cartilage-degrading metalloproteinases and cytokines from synovial membrane cells (SM) isolated from patients with knee OA was assessed in vitro. SM were cultivated as SM monocultures in the presence or absence of 45S5-BG. On day 1 (d1) and d7 (d7), the concentrations of Matrix Metalloproteinases (MMPs) and cytokines were assessed. In 45S5-BG-treated SM cultures, MMP9 concentration was significantly reduced at d1 and d7, whilst MMP13 was significantly increased at d7. Concentrations of interleukin (IL)-1B and C-C motif chemokine ligand 2 (CCL2) in 45S5-BG-treated SM cultures were significantly increased at both time points, as were interferon gamma (IFNG) and IL-6 at d7. Our data show an effect of 45S5-BG on SM activity, which was not clearly protective, anti-inflammatory, or pro-inflammatory. The influence of 45S5-BG on MMP release was more suggestive of a cartilage protective effect, but 45S5-BG also increased the release of pro-inflammatory cytokines. Further studies are needed to analyze the effect of BGs on OA inflammation, including the anti-inflammatory modification of BG compositions.

Plasma-derived extracellular vesicle surface markers CD45, CD326 and CD56 correlate with the stage of osteoarthritis: a primary study of a novel and promising diagnostic tool of the disease

Recently, there is a growing interest in the research based on extracellular vesicles (EVs) which represent paracrine factors secreted by almost all cell types. Both, normal and pathological cells are able to release various types of EVs with different physiological properties, functions and compositions. EVs play an important role in intercellular communication, mechanism and tissue repair. Moreover, EVs could help not only in the treatment of diseases but also in their diagnostics. This work focused on the evaluation of the potential of EVs being used as biomarkers for the diagnosis of osteoarthritis (OA) based on a comparison of the composition of EVs separated from platelet-poor plasma (PPP) of healthy donors and OA patients at different stages of OA. OA is established as a complex syndrome with extensive impact on multiple tissues within the synovial joint. It is a chronic disease of musculoskeletal system that mainly affects the elderly. Depending on the use of the Kellgren-Lawrence classification system, there are four grades of OA which have a negative impact on patients' quality of life. It is very difficult to detect OA in its early stages, so it is necessary to find a new diagnostic method for its timely detection. PPP samples were prepared from whole blood. PPP-EVs were separated from 3 groups of donors-healthy control, early stage OA, end-stage OA, and their content was compared and correlated. EVs from PPP were separated by size exclusion chromatography and characterized in terms of their size, yield and purity by NTA, western blotting, ELISA and flow cytometry. Detection of surface markers expression in EVs was performed using MACSPlex approach. Inflammatory and growth factors in EVs were analysed using MAGPix technology. Our study confirmed significant differences between EVs surface markers of patients and healthy controls correlating with the age of donor (CD63, CD31 and ROR1) and stage of OA (CD45, CD326 and CD56), respectively. Circulating EVs have been under extensive investigation for their capability to predict OA pathology diagnosis as potential targets for biomarker discovery. Taken together, obtained results indicated that PPP-EVs surface markers could be used as potential biomarkers in the early diagnosis of OA.

Better post-operative outcomes at 1-year follow-up are associated with lower levels of pre-operative synovitis and higher levels of IL-6 and VEGFA in unicompartmental knee arthroplasty patients

PURPOSE

Osteoarthritis (OA) is associated with inflammation, and residual inflammation may influence outcomes following knee arthroplasty. This may be more relevant for patients undergoing unicompartmental knee arthroplasty (UKA) due to larger remaining areas of native tissue. This study aimed to: (1) characterise inflammatory profiles for medial UKA patients and (2) investigate whether inflammation markers are associated with post-operative outcomes.

METHODS

This prospective, observational study has national ethics approval. Bloods, synovial fluid, tibial plateaus and synovium were collected from medial UKA patients in between 1 January 2021 and 31 December 2021. Cytokine and chemokine concentrations in serum and synovial fluid (SF) were measured with multiplexed assays. Disease severity of cartilage and synovium was assessed using validated histological scores. Post-operative outcomes were measured with Oxford Knee Score (OKS), Forgotten Joint Score (FJS-12) and pain scores.

RESULTS

The study included 35 patients. SF VEGFA was negatively correlated with pre-operative pain at rest (r - 0.5, p = 0.007), and FJS-12 at six-week (r 0.44, p = 0.02), six-month (r 0.61, p < 0.01) and one-year follow-up (r 0.63, p = 0.03). Serum and SF IL-6 were positively correlated with OKS at early follow-up (serum 6 weeks, r 0.39, p = 0.03; 6 months, r 0.48, p < 0.01; SF 6 weeks, r 0.35, p = 0.04). At six weeks, increased synovitis was negatively correlated with improvements in pain at rest (r - 0.41, p = 0.03) and with mobilisation (r - 0.37, p = 0.047).

CONCLUSION

Lower levels of synovitis and higher levels of IL-6 and VEGFA were associated with better post-operative outcomes after UKA, which could be helpful for identifying UKA patients in clinical practice.

LEVEL OF EVIDENCE

Level IV case series.

The Effects of an Osteoarthritic Joint Environment on ACL Damage and Degeneration: A Yucatan Miniature Pig Model

Posttraumatic osteoarthritis (PTOA) arises secondary to joint injuries and is characteristically driven by inflammatory mediators. PTOA is often studied in the setting of ACL tears. However, a wide range of other injuries also lead to PTOA pathogenesis. The purpose of this study was to characterize the morphological changes in the uninjured ACL in a PTOA inflammatory environment. We retrospectively reviewed 14 ACLs from 13 Yucatan minipigs, 7 of which had undergone our modified intra-articular drilling (mIAD) procedure, which induced PTOA through inflammatory mediators. Seven ACLs were harvested from mIAD minipigs (PTOA) and seven ACLs from control minipigs with no cartilage degeneration (non-PTOA). ACL degeneration was evaluated using histological scoring systems. IL-1β, NF-κB, and TNF-α mRNA expression in the synovium was measured using qRT-PCR. PTOA minipigs demonstrated significant ACL degeneration, marked by a disorganized extracellular matrix, increased vascularity, and changes in cellular shape, density, and alignment. Furthermore, IL-1β, NF-κB, and TNF-α expression was elevated in the synovium of PTOA minipigs. These findings demonstrate the potential for ACL degeneration in a PTOA environment and emphasize the need for anti-inflammatory disease-modifying therapies following joint injury.

Medermycin Inhibits TNFα-Promoted Inflammatory Reaction in Human Synovial Fibroblasts

Synovial inflammation plays a crucial role in the destruction of joints and the experience of pain in osteoarthritis (OA). Emerging evidence suggests that certain antibiotic agents and their derivatives possess anti-inflammatory properties. Medermycin (MED) has been identified as a potent antibiotic, specifically active against Gram-positive bacteria. In this study, we aimed to investigate the impact of MED on TNFα-induced inflammatory reactions in a synovial cell line, SW-982, as well as primary human synovial fibroblasts (HSF) using RNA sequencing, rtRT-PCR, ELISA, and western blotting. Through the analysis of differentially expressed genes (DEGs), we identified a total of 1478 significantly upregulated genes in SW-982 cells stimulated with TNFα compared to the vehicle control. Among these upregulated genes, MED treatment led to a reduction in 1167 genes, including those encoding proinflammatory cytokines such as IL1B, IL6, and IL8. Pathway analysis revealed the enrichment of DEGs in the TNF and NFκB signaling pathway, further supporting the involvement of MED in modulating inflammatory responses. Subsequent experiments demonstrated that MED inhibited the expression of IL6 and IL8 at both the mRNA and protein levels in both SW982 cells and HSF. Additionally, MED treatment resulted in a reduction in p65 phosphorylation in both cell types, indicating its inhibitory effect on NFκB activation. Interestingly, MED also inhibited Akt phosphorylation in SW982 cells, but not in HSF. Overall, our findings suggest that MED suppresses TNFα-mediated inflammatory cytokine production and p65 phosphorylation. These results highlight the potential therapeutic value of MED in managing inflammatory conditions in OA. Further investigations utilizing articular chondrocytes and animal models of OA may provide valuable insights into the therapeutic potential of MED for this disease.

Concentration-dependent effects of leptin on osteoarthritis-associated changes in phenotype of human chondrocytes

Metabolic syndrome is a risk factor for osteoarthritis. Elevated leptin levels have been implicated as a potential cause of this association. Previous studies have shown that supra-physiological leptin concentrations can induce osteoarthritis-like changes in chondrocyte phenotype. Here, we tested the effects of leptin in the concentration range found in synovial fluid on chondrocyte phenotype. Chondrocytes isolated from macroscopically normal regions of cartilage within osteoarthritic joints from patients undergoing knee arthroplasty, all with body mass index >30 kg/m2 were treated with 2-40 ng/ml leptin for 24 h. Chondrocyte phenotype marker expression was measured by RT-qPCR and western blot. The role of HES1 in mediating the effects of leptin was determined by gene knockdown using RNAi and over-expression using adenoviral-mediated gene delivery. Treatment of chondrocytes with 20 or 40 ng/ml leptin resulted in decreased SOX9 levels and decreased levels of the SOX9-target genes COL2A1 and ACAN. Levels of HES1 were lower and ADAMTS5 higher in chondrocytes treated with 20 or 40 ng/ml leptin. HES1 knockdown resulted in increased ADAMTS5 expression whereas over-expression of HES1 prevented the leptin-induced increase in ADAMTS5. An increase in MMP13 expression was only evident in chondrocytes treated with 40 ng/ml leptin and was not mediated by HES1 activity. High concentrations of leptin can cause changes in chondrocyte phenotype consistent with those seen in osteoarthritis. Synovial fluid leptin concentrations of this level are typically observed in patients with metabolic syndrome and/or women, suggesting elevated leptin levels may form part of the multifactorial network that leads to osteoarthritis development in these patients.

Two Amnion-Derived Mesenchymal Stem-Cells Injections to Osteoarthritic Elbows in Dogs-Pilot Study

The aim of the study was to investigate the potential of cell-based regenerative therapy for elbow joints affected by osteoarthritis. Interest was focused on two intra-articular applications of amnion-derived mesenchymal stem cells (A-MSCs) to a group of different breeds of dogs with elbow osteoarthritis (13 joints). Two injections were performed 14 days apart. We evaluated synovial fluid biomarkers, such as IFN-γ, IL-6, IL-15, IL-10, MCP-1, TNF-α, and GM-CSF, by multiplex fluorescent micro-bead immunoassay in the treated group of elbows (n = 13) (day 0, day 14, and day 28) and in the control group of elbows (n = 9). Kinematic gait analysis determined the joint range of motion (ROM) before and after each A-MSCs application. Kinematic gait analysis was performed on day 0, day 14, and day 28. Kinematic gait analysis pointed out improvement in the average range of motion of elbow joints from day 0 (38.45 ± 5.74°), day 14 (41.7 ± 6.04°), and day 28 (44.78 ± 4.69°) with statistical significance (p < 0.05) in nine elbows. Correlation analyses proved statistical significance (p < 0.05) in associations between ROM (day 0, day 14, and day 28) and IFN-γ, IL-6, IL-15, MCP-1, TNF-α, and GM-CSF concentrations (day 0, day 14, and day 28). IFN-γ, IL-6, IL-15, MCP-1, GM-CSF, and TNF- α showed negative correlation with ROM at day 0, day 14, and day 28, while IL-10 demonstrated positive correlation with ROM. As a consequence of A-MSC application to the elbow joint, we detected a statistically significant (p < 0.05) decrease in concentration levels between day 0 and day 28 for IFN-γ, IL-6, and TNF-α and statistically significant increase for IL-10. Statistical significance (p < 0.05) was detected in TNF-α, IFN-γ, and GM-CSF concentrations between day 14 and the control group as well as at day 28 and the control group. IL-6 concentrations showed statistical significance (p < 0.05) between day 14 and the control group.

Recent targets of osteoarthritis research

Osteoarthritis is one of the most common diseases and poses a significant medical burden worldwide. Currently, the diagnosis and treatment of osteoarthritis primarily rely on clinical symptoms and changes observed in radiographs or other image modalities. However, identification based on reliable biomarkers would greatly improve early diagnosis, help with precise monitoring of disease progression, and provide aid for accurate treatment. In recent years, several biomarkers for osteoarthritis have been identified, including image modalities and biochemical biomarkers such as collagen degradation products, pro- or anti-inflammatory cytokines, micro RNAs, long non-coding RNAs, and circular RNAs. These biomarkers offer new insights in the pathogenesis of osteoarthritis and provide potential targets for further research. This article reviews the evolution of osteoarthritis biomarkers from the perspective of pathogenesis and emphasizes the importance of continued research to improve the diagnosis, treatment, and management of osteoarthritis.

System pharmacology analysis to decipher the effect and mechanism of active ingredients combination from Duhuo Jisheng decoction on osteoarthritis in rats

ETHNOPHARMACOLOGY RELEVANCE

Duhuo Jisheng decoction is a traditional Chinese formula that has been widely used in clinical practice to treat osteoarthritis, which has the effects of removing invaded cold and dampness, relieving joint pain. However, it is difficult to determine the effective substances and mechanisms due to assorted herbs and components, and further research is needed.

AIM OF THE STUDY

This study was designed to explore and verify the mechanism and targets of DHJSD in the treatment of OA via network analysis and experiments.

METHOD

In this study, the active ingredients of DHJSD were qualitatively analyzed by UPLC-QDA. Network analysis was used to identify common targets and pathways. Next, we explored the therapeutic mechanism of DHJSD through a rat model of knee osteoarthritis. HE staining was used to judge the establishment of the animal model. ELISA and Western blotting were used to verify the expression of key pathway proteins.

CONCLUSION

In this study, seventeen chemical constituents in DHJSD were identified. According to the network analysis, we obtained the potential associated pathways of action. Then, molecular docking and SPR experiments showed that the sixteen identified components had high binding energies to IL-6. HE staining showed that the high-dose group of DHJSD had an obvious therapeutic effect on model rats. Compared with the model group, the levels of IL-1β, TNF-α, IL-6, MMP3, MMP13, ADAMTS4 and ADAMTS5 in serum and the expression of STAT3 and p-STAT3 protein in administration groups were significantly decreased. This result indicated that the IL-6/STAT3 signaling pathway was one of the important pathways regulated by DHJSD to improve OA.

Therapeutic Perspectives for Inflammation and Senescence in Osteoarthritis Using Mesenchymal Stem Cells, Mesenchymal Stem Cell-Derived Extracellular Vesicles and Senolytic Agents

Osteoarthritis (OA) is the most common cause of disability worldwide among the elderly. Alarmingly, the incidence of OA in individuals less than 40 years of age is rising, likely due to the increase in obesity and post-traumatic osteoarthritis (PTOA). In recent years, due to a better understanding of the underlying pathophysiology of OA, several potential therapeutic approaches targeting specific molecular pathways have been identified. In particular, the role of inflammation and the immune system has been increasingly recognized as important in a variety of musculoskeletal diseases, including OA. Similarly, higher levels of host cellular senescence, characterized by cessation of cell division and the secretion of a senescence-associated secretory phenotype (SASP) within the local tissue microenvironments, have also been linked to OA and its progression. New advances in the field, including stem cell therapies and senolytics, are emerging with the goal of slowing disease progression. Mesenchymal stem/stromal cells (MSCs) are a subset of multipotent adult stem cells that have demonstrated the potential to modulate unchecked inflammation, reverse fibrosis, attenuate pain, and potentially treat patients with OA. Numerous studies have demonstrated the potential of MSC extracellular vesicles (EVs) as cell-free treatments that comply with FDA regulations. EVs, including exosomes and microvesicles, are released by numerous cell types and are increasingly recognized as playing a critical role in cell-cell communication in age-related diseases, including OA. Treatment strategies for OA are being developed that target senescent cells and the paracrine and autocrine secretions of SASP. This article highlights the encouraging potential for MSC or MSC-derived products alone or in combination with senolytics to control patient symptoms and potentially mitigate the progression of OA. We will also explore the application of genomic principles to the study of OA and the potential for the discovery of OA phenotypes that can motivate more precise patient-driven treatments.

Interleukin-6 neutralization and regulatory T cells are additive in chondroprotection from IL-1β-induced inflammation

Anti-inflammatory Regulatory T cells (Tregs) are enriched in the joints of patients with osteoarthritis (OA) compared to healthy joints. Tregs maintain homeostasis through secretion of anti-inflammatory cytokines and cell-to-cell interactions including immune checkpoint signaling. Interleukin-6 (IL-6) is a pleiotropic cytokine secreted by inflamed synoviocytes and chondrocytes that can inhibit or alter Treg function. This study tested the hypothesis that neutralization of IL-6 would enable Treg anti-inflammatory function to resolve inflammation and catabolism elicited by IL-1β in an equine chondrocyte/synoviocyte/Treg tri-culture OA model. Synoviocyte/chondrocyte co-cultures were stimulated with IL-1β, and treated with αIL-6 neutralizing antibody. Activated Tregs secreting IL-10 were added in direct contact with synoviocytes to create a tri-culture. Neutralization of IL-6 partially restored Treg anti-inflammatory functions and, in combination, reduced IL-1β-stimulated synoviocyte MMP13 expression to control levels and restored Acan expression in chondrocytes. IL-6 neutralization alone decreased Il6 expression in chondrocytes and synoviocytes, mitigating IL-6 positive feedback loop. Although Tregs were the primary producers of anti-inflammatory IL-10 and IL-4, they also produced pro-inflammatory IL-17A, as detected by ELIA, which may have been responsible for incomplete rescue of synoviocyte/chondrocyte homeostasis following IL-1β stimulation. Treg secretion of IL-10, IL-4, and IL-17A was not altered by tri-culture conditions or presence of αIL-6, therefore, it was unlikely that Treg phenotype instability occurred. The significant effect of chondrocyte/synoviocyte donor, but not Treg donor, on gene expression and IL-6 concentration in conditioned media, indicated that personalized therapy considering the patient's OA status might be needed for successful implementation of immunotherapy in the context of OA.

Genetically predicted circulating levels of cytokines and the risk of osteoarthritis: A mendelian randomization study

Background: The association between inflammatory cytokines and osteoarthritis (OA) has been reported in several observational studies, but the causal relationship between these two remains unknown. Hence, we performed this two-sample Mendelian randomization (MR) to confirm the causal relationship between circulating levels of inflammatory factors and osteoarthritis risk.

Method: We used genetic variants associated with cytokine circulation levels from a meta-analysis of genome-wide association studies (GWASs) in 8,293 Finns as instrumental variables and obtained OA data from the United Kingdom Biobank, including a total of 345,169 subjects of European ancestry (66,031 diagnosed OA cases and 279,138 controls). Inverse variance weighting (IVW), MR-Egger, Wald Ratio, weighted median, and MR multiplicity residual sums with outliers (MR-PRESSO) were used.

Result: We found a causal relationship between circulating levels of macrophage inflammatory protein-1beta (MIP-1β) and risk of OA (OR = 0.998, 95% CI = 0.996–0.999p = 9.61 × 10−5); tumour necrosis factor beta (TNF-β) was also causally associated with risk of OA (OR = 0.996,95%CI = 0.994–0.999, p = 0.002); finally we found a suggestive association between C-C motif chemokine ligand 5(CCL5, also called Rantes) and OA risk (OR = 1.013, 95%CI = 1.002–1.024,p = 0.016).

Conclusion: Our findings offer promising leads for the development of new therapeutic targets in the treatment of osteoarthritis. By identifying the role of inflammatory cytokines in this debilitating condition through a genetic epidemiological approach, our study contributes to a better understanding of the underlying disease mechanisms. These insights may ultimately pave the way for more effective treatments that improve patient outcomes.

A review of the pleiotropic actions of the IFN-inducible CXC chemokine receptor 3 ligands in the synovial microenvironment

Chemokines are pivotal players in instigation and perpetuation of synovitis through leukocytes egress from the blood circulation into the inflamed articulation. Multitudinous literature addressing the involvement of the dual-function interferon (IFN)-inducible chemokines CXCL9, CXCL10 and CXCL11 in diseases characterized by chronic inflammatory arthritis emphasizes the need for detangling their etiopathological relevance. Through interaction with their mutual receptor CXC chemokine receptor 3 (CXCR3), the chemokines CXCL9, CXCL10 and CXCL11 exert their hallmark function of coordinating directional trafficking of CD4+ TH1 cells, CD8+ T cells, NK cells and NKT cells towards inflammatory niches. Among other (patho)physiological processes including infection, cancer, and angiostasis, IFN-inducible CXCR3 ligands have been implicated in autoinflammatory and autoimmune diseases. This review presents a comprehensive overview of the abundant presence of IFN-induced CXCR3 ligands in bodily fluids of patients with inflammatory arthritis, the outcomes of their selective depletion in rodent models, and the attempts at developing candidate drugs targeting the CXCR3 chemokine system. We further propose that the involvement of the CXCR3 binding chemokines in synovitis and joint remodeling encompasses more than solely the directional ingress of CXCR3-expressing leukocytes. The pleotropic actions of the IFN-inducible CXCR3 ligands in the synovial niche reiteratively illustrate the extensive complexity of the CXCR3 chemokine network, which is based on the intercommunion of IFN-inducible CXCR3 ligands with distinct CXCR3 isoforms, enzymes, cytokines, and infiltrated and resident cells present in the inflamed joints.

Association between an Increased Serum CCL5 Level and Pathophysiology of Degenerative Joint Disease in the Temporomandibular Joint in Females

Degenerative joint disease of the temporomandibular joints (DJD-TMJ) clinically manifests with symptoms such as orofacial pain, joint sounds and limited jaw movements. Our research group previously reported the functional necessity of a chemokine-chemokine receptor axis of CCL5-CCR5 in osteoclasts. Accumulated studies reported that this axis was involved in the pathogenesis of bone and joint destructive diseases, suggesting CCL5 as a potent biomarker. This study investigated whether or not the serum level of CCL5 can be a biomarker of DJD-TMJ and concomitantly analyzed changes in the serum and urine levels of bone markers to see whether or not changes in the rate of bone metabolism were predisposing. We enrolled 17 female subjects with diagnosed DJD-TMJ and sexually and age-matched 17 controls. The serum CCL5 level in DJD-TMJ subjects was significantly higher than that in the control subjects. Multivariate analyses indicated an association between an augmented CCL5 level and the rate of bone metabolism, especially in relatively young DJD-TMJ subjects without other systemic symptoms. A principal component analysis of serum markers and our pharmacological experiment using a postmenopausal model of ovariectomized rats suggested that an augmented serum CCL5 level specifically reflected DJD-TMJ and that covert changes in the rate of bone metabolism predisposed individuals to DJD-TMJ.

Soluble and EV-Associated Diagnostic and Prognostic Biomarkers in Knee Osteoarthritis Pathology and Detection

Osteoarthritis (OA) is the most common degenerative disease of the connective tissue of the human musculoskeletal system. Despite its widespread prevalence, there are many limitations in its diagnosis and treatment. OA diagnosis currently relies on the presence of clinical symptoms, sometimes accompanied by changes in joint X-rays or MRIs. Biomarkers help not only to diagnose early disease progression but also to understand the process of OA in many ways. In this article, we briefly summarize information on articular joints and joint tissues, the pathogenesis of OA and review the literature about biomarkers in the field of OA, specifically inflammatory cytokines/chemokines, proteins, miRNA, and metabolic biomarkers found in the blood, synovial fluid and in extracellular vesicles.

Synovial Fluid Derived from Human Knee Osteoarthritis Increases the Viability of Human Adipose-Derived Stem Cells through Upregulation of FOSL1

Knee osteoarthritis (Knee OA) is an irreversible condition that causes bone deformity and degeneration of the articular cartilage that comprises the joints, resulting in chronic pain and movement disorders. The administration of cultured adipose-derived stem cells (ADSCs) into the knee joint cavity improves the clinical symptoms of Knee OA; however, the effect of synovial fluid (SF) filling the joint cavity on the injected ADSCs remains unclear. In this study, we investigated the effect of adding SF from Knee OA patients to cultured ADSCs prepared for therapeutic use in an environment that mimics the joint cavity. An increase in the viability of ADSCs was observed following the addition of SF. Gene expression profiling of SF-treated ADSCs using DNA microarrays revealed changes in several genes involved in cell survival. Of these genes, we focused on FOSL1, which is involved in the therapeutic effect of ADSCs and the survival and proliferation of cancer stem cells. We confirmed the upregulation of FOSL1 mRNA and protein expression using RT-PCR and western blot analysis, respectively. Next, we knocked down FOSL1 in ADSCs using siRNA and observed a decrease in cell viability, indicating the involvement of FOSL1 in the survival of ADSCs. Interestingly, in the knockdown cells, ADSC viability was also decreased by SF exposure. These results suggest that SF enhances cell viability by upregulating FOSL1 expression in ADSCs. For therapy using cultured ADSCs, the therapeutic effect of ADSCs may be further enhanced if an environment more conducive to the upregulation of FOSL1 expression in ADSCs can be established.

Truncated lubricin glycans in osteoarthritis stimulate the synoviocyte secretion of VEGFA, IL-8, and MIP-1α: Interplay between O-linked glycosylation and inflammatory cytokines

The primary aim of the study was to identify inflammatory markers relevant for osteoarthritis (OA)-related systemic (plasma) and local (synovial fluid, SF) inflammation. From this, we looked for inflammatory markers that coincided with the increased amount of O-linked Tn antigen (GalNAcα1-Ser/Thr) glycan on SF lubricin. Inflammatory markers in plasma and SF in OA patients and controls were measured using a 44-multiplex immunoassay. We found consistently 29 markers detected in both plasma and SF. The difference in their concentration and the low correlation when comparing SF and plasma suggests an independent inflammatory environment in the two biofluids. Only plasma MCP-4 and TARC increased in our patient cohort compared to control plasma. To address the second task, we concluded that plasma markers were irrelevant for a direct connection with SF glycosylation. Hence, we correlated the SF-inflammatory marker concentrations with the level of altered glycosylation of SF-lubricin. We found that the level of SF-IL-8 and SF-MIP-1α and SF-VEGFA in OA patients displayed a positive correlation with the altered lubricin glycosylation. Furthermore, when exposing fibroblast-like synoviocytes from both controls and OA patients to glycovariants of recombinant lubricin, the secretion of IL-8 and MIP-1α and VEGFA were elevated using lubricin with Tn antigens, while lubricin with sialylated and nonsialylated T antigens had less or no measurable effect. These data suggest that truncated glycans of lubricin, as found in OA, promote synovial proinflammatory cytokine production and exacerbate local synovial inflammation.

Roles of Cartilage-Resident Stem/Progenitor Cells in Cartilage Physiology, Development, Repair and Osteoarthritis

Osteoarthritis (OA) is a degenerative disease that causes irreversible destruction of articular cartilage for which there is no effective treatment at present. Although articular cartilage lacks intrinsic reparative capacity, numerous studies have confirmed the existence of cartilage-resident stem/progenitor cells (CSPCs) in the superficial zone (SFZ) of articular cartilage. CSPCs are characterized by the expression of mesenchymal stromal cell (MSC)-related surface markers, multilineage differentiation ability, colony formation ability, and migration ability in response to injury. In contrast to MSCs and chondrocytes, CSPCs exhibit extensive proliferative and chondrogenic potential with no signs of hypertrophic differentiation, highlighting them as suitable cell sources for cartilage repair. In this review, we focus on the organizational distribution, markers, cytological features and roles of CSPCs in cartilage development, homeostasis and repair, and the application potential of CSPCs in cartilage repair and OA therapies.

The Added Value of the “Co” in Co-Culture Systems in Research on Osteoarthritis Pathology and Treatment Development

Osteoarthritis (OA) is a highly prevalent disease and a major health burden. Its development and progression are influenced by factors such as age, obesity or joint overuse. As a whole organ disease OA affects not only cartilage, bone and synovium but also ligaments, fatty or nervous tissue surrounding the joint. These joint tissues interact with each other and understanding this interaction is important in developing novel treatments. To incorporate and study these interactions in OA research, several co-culture models have evolved. They combine two or more cell types or tissues and investigate the influence of amongst others inflammatory or degenerative stimuli seen in OA. This review focuses on co-cultures and the differential processes occurring in a given tissue or cell as a consequence of being combined with another joint cell type or tissue, and/or the extent to which a co-culture mimics the in vivo processes. Most co-culture models depart from synovial lining and cartilage culture, but also fat pad and bone have been included. Not all of the models appear to reflect the postulated in vivo OA pathophysiology, although some of the discrepancies may indicate current assumptions on this process are not entirely valid. Systematic analysis of the mutual influence the separate compartments in a given model exert on each other and validation against in vivo or ex vivo observation is still largely lacking and would increase their added value as in vitro OA models.

Interleukin 6 Concentration in Synovial Fluid of Patients with Inflammatory and Degenerative Arthritis

AIM

The present study aims to compare interleukin 6 (IL-6) concentration in synovial fluid in patients with known types of arthritis.

BACKGROUND

Persistent synovitis without known markers such as Rheumatoid Factor (RF), Anti-Citrullinated Protein Antibodies (ACPA), and genetic markers as HLA-B27 is not uncommon. It is valuable to determine the presence of chronic inflammation and put it in correlation with age-related changes, which are especially relevant for middle-aged patients with mono- or oligoarthritis, when the dilemma to start disease-modifying drugs for inflammatory disease often is present. INTERLEUKIN 6 (IL-6) plays a significant role in chronic inflammation.

OBJECTIVES

IL-6 concentration in synovial fluid reflects the presence and activity of joint inflammation.

METHODS

Synovial fluid was obtained from 101 patients with chronic synovitis. IL-6 concentration was determined by the immunochemical luminescence method.

RESULTS

The median IL-6 concentration in synovial fluid in patients with osteoarthritis (OA) was 138.0 pg/ml (interquartile range [IQR] 43.4 to 296.0); in patients with rheumatoid arthritis was 2516.5 pg/ml, (IQR 1136.0 to 25058.0); in reactive arthritis 2281.0 pg/ml (IQR 1392.0 to 8652.0); psoriatic arthritis 1964.0 pg/ml (IQR 754.0 to 7300.0); ankylosing spondylitis 2776.0 pg/ml (IQR 514.7, 3944.0); in a group with negative RF, ACPA and HLA-B27 inflammatory arthritis 2163.0 pg/ml (IQR 822.0 to 7875.0). There is statistically significant difference of IL-6 concentration comparing OA and each inflammatory arthritis group, p<0.0001.

CONCLUSION

IL-6 detection in the synovial fluid is helpful in arthritis evaluation. The results show that an IL-6 level over 1000 pg/ml suggests the diagnosis of inflammatory arthritis.

A tool for evaluating novel osteoarthritis therapies using multivariate analyses of human cartilage-synovium explant co-culture

OBJECTIVE

There is a need to incorporate multiple tissues into in vitro OA models to evaluate novel therapeutics. This approach is limited by inherent donor variability. We present an optimized research tool: a human OA cartilage-synovium explant co-culture model (OA-EXM) that employs donor-matched lower and upper limit response controls combined with statistical approaches to address variability. Multiple rapid read-outs allow for evaluation of therapeutics while cataloguing cartilage-synovium interactions.

DESIGN

48-h human explant cultures were sourced from OA knee arthroplasties. An OA-like cartilage-synovium co-culture baseline was established relative to donor-matched upper limit supraphysiological pro-inflammatory cytokine and lower limit OA cartilage or synovium alone controls. 100 nM dexamethasone treatment validated possible "rescue effects" within the OA-EXM dual tissue environment. Gene expression, proteoglycan loss, MMP activity, and soluble protein concentrations were analyzed using blocking and clustering methods.

RESULTS

The OA-EXM demonstrates the value of the co-culture approach as the addition of OA synovium increases OA cartilage proteoglycan loss and expression of MMP1, MMP3, MMP13, CXCL8, CCL2, IL6, and PTGS2, but not to the extent of supraphysiological stimulation. Conversely, OA cartilage does not affect gene expression or MMP activity of OA synovium. Dexamethasone shows dual treatment effects on synovium (pro-resolving macrophage upregulation, protease downregulation) and cartilage (pro-inflammatory, catabolic, and anabolic downregulation), and decreases soluble CCL2 levels in co-culture, thereby validating OA-EXM utility.

CONCLUSIONS

The OA-EXM is representative of late-stage OA pathology, captures dual interactions between cartilage and synovium, and combined with statistical strategies provides a rapid, sensitive research tool for evaluating OA therapeutics.

A Preliminary Study of Combined Detection of COMP, TIMP-1, and MMP-3 in Synovial Fluid: Potential Indicators of Osteoarthritis Progression

OBJECTIVE

Osteoarthritis (OA) commonly affects weight-bearing joints and is characterized by articular cartilage breakdown combined with osteophyte formation at the joint margins and chronic nonspecific inflammation of synovium. Understanding the profile of inflammation in a patient population is an essential starting point to predict or prevent OA progression. The aim of this study was to identify the profile of selected biomolecules in synovial fluid (SF) and investigate the correlation according to gender, age, and severity of the disease within patients from among the general knee OA population.

DESIGN

In our study SF samples were aspirated from the knees of 65 OA patients (46 patients with early knee OA and 19 patients with end-stage knee OA according to the Kellgren-Lawrence grading scale). The concentration of interleukins (IL-6, IL-8), matrix metalloproteinases (MMP-1, MMP-3, MMP-13), MMPs inhibitors (TIMP-1, TIMP-2), cartilage oligomeric matrix protein (COMP), and adiponectin was analyzed using a multiplex ELISA-based approach.

CONCLUSIONS

Our results indicate significant linear correlation of MMP-13 and COMP concentration with age (P < 0.05), but not with OA severity. In fact, 3 of the examined biomolecules, MMP-3 (P < 0.01), TIMP-1 (P < 0.01), and COMP (P < 0.05) significantly correlate with the grade of knee OA and might be associated with OA severity.

Macrophage phenotypes and monocyte subsets after destabilization of the medial meniscus in mice

Macrophages play an important role in the development and progression of osteoarthritis (OA). The aim of this study was to identify macrophage phenotypes in synovium and monocyte subsets in peripheral blood in C57BL/6 mice by destabilizing the medial meniscus (DMM), and the association of macrophage subsets with OA features. DMM, sham, and non-operated knees were histologically assessed between 1 and 56 days for macrophage polarization states by immunohistochemistry (IHC), cartilage damage, synovial thickening, and osteophytes (n = 9 per timepoint). Naive knees (n = 6) were used as controls. Monocyte and polarized synovial macrophage subsets were evaluated by flow cytometry. CD64 and CD206 levels on IHC were higher at early timepoints in DMM and sham knees compared to naive knees. iNOS labeling intensity was higher in DMM and sham knees than in naive knees from d3 onwards. CD163 expression was unaltered at all timepoints. Even though macrophage polarization profiles were similar in DMM and sham knees, only in DMM knees the presence of iNOS and CD206 associated with synovial thickness, and CD163 staining inversely correlated with osteophyte presence. At day 14, monocyte subset distribution was different in peripheral blood of DMM mice compared with sham mice. In conclusion, monocyte subsets in blood and synovial macrophage phenotypes vary after joint surgery. High levels of iNOS⁺ , CD163⁺ , and CD206⁺ cells are found in both destabilized and sham-operated knees, and coexistence with joint instability may be a requirement to initiate and exacerbate OA progression.

Cytokines and Chemokines Involved in Osteoarthritis Pathogenesis

Osteoarthritis is a common cause of disability worldwide. Although commonly referred to as a disease of the joint cartilage, osteoarthritis affects all joint tissues equally. The pathogenesis of this degenerative process is not completely understood; however, a low-grade inflammation leading to an imbalance between anabolic and katabolic processes is a well-established factor. The complex network of cytokines regulating these processes and cell communication has a central role in the development and progression of osteoarthritis. Concentrations of both proinflammatory and anti-inflammatory cytokines were found to be altered depending on the osteoarthritis stage and activity. In this review, we analyzed individual cytokines involved in the immune processes with an emphasis on their function in osteoarthritis.

Unsulfated biotechnological chondroitin by itself as well as in combination with high molecular weight hyaluronan improves the inflammation profile in osteoarthritis in vitro model

Several studies suggest that inflammation has a pivotal role during the progression of osteoarthritis (OA) and cytokines have been identified as the main process mediators. This study aimed to explore the ability to modulate the main OA pro-inflammatory biomarkers of novel gels (H-HA/BC) based on high molecular weight hyaluronan (H-HA) and unsulfated biotechnological chondroitin (BC). For the first time, BC was tested also in combination with H-HA on human primary cells isolated from pathological knee joints. Specifically, the experiments were performed using an OA in vitro model based on human chondrocytes and synoviocytes. To evaluate the anti-inflammatory effects of H-HA/BC in comparison with H-HA and BC single gels, NF-kB, COMP-2, MyD88, MMP-13 and a wide range of cytokines, known to be specific biomarkers in OA (e.g., IL-6, IL-8, and TNF-α), were evaluated. In addition, cell morphology and proliferation occurring in the presence of either H-HA/BC or single components were assessed using time-lapse video microscopy. It was shown that synovial fluids and cells isolated from OA suffering patients, presented a cytokine pattern respondent to an ongoing inflammation status. H-HA and BC significantly reduced the levels of 23 biomarkers associated with cartilage damage. However, H-HA/BC decreased significantly 24 biological mediators and downregulated 19 of them more efficiently than the single components. In synoviocytes cultures, cytokine analyses proved that H-HA/BC gels re-established an extracellular environment more similar to a healthy condition reducing considerably the concentration of 11 analytes. Instead, H-HA and BC significantly modulated 7 (5 only with a longer treatment) and 8 biological cytokines, respectively. Our results suggest that H-HA/BC beyond the viscosupplementation effect typical for HA-based gels, can improve the inflammation status in joints and thus could be introduced as a valid protective and anti-inflammatory intraarticular device in the field of Class III medical devices for OA treatments.

Extensive cytokine analysis in synovial fluid of osteoarthritis patients

OBJECTIVE

Osteoarthritis (OA) is a joint disease characterized by articular cartilage loss and afflicts many people worldwide. However, diagnostic methods and treatment options remain limited and are often characterized by low sensitivity and low efficacy. The focus of the present study was to identify proteomic biomarkers in synovial fluid to improve diagnosis and therapy of OA patients.

METHODS

Antibody array technology was utilized for protein expression profiling of synovial fluid from 24 OA patients and 24 healthy persons.

RESULTS

Compared with healthy persons, twenty proteins showed lower expression levels in OA patients, while thirty proteins had higher levels. Among these differential proteins, GITRL, CEACAM-1, FSH, EG-VEGF, FGF-4, PIGF, Cystatin EM and NT-4 were found for the first time to be differentially expressed in OA. Bioinformatics analysis showed that most of these differential proteins were involved leukocytes events, and some differentially expressed proteins including IL-18, CXCL1, CTLA4, MIP-3b, CD40, MMP-1, THBS1, CCL11, PAI-1, BAFF, aggrecan, angiogenin and follistatin were located in central positions of the protein-protein interaction (PPI) network.

CONCLUSION

We speculate that leukocyte proliferation and migration to the joint may be an important pathogenesis of OA, which needs a further validation. The central proteins of the PPI network may play a more pivotal role in OA. The newly identified differentially expressed proteins may be novel biomarkers for OA diagnosis and targets for OA therapy.

An Evidence-Based Systematic Review of Human Knee Post-Traumatic Osteoarthritis (PTOA): Timeline of Clinical Presentation and Disease Markers, Comparison of Knee Joint PTOA Models and Early Disease Implications

Understanding the causality of the post-traumatic osteoarthritis (PTOA) disease process of the knee joint is important for diagnosing early disease and developing new and effective preventions or treatments. The aim of this review was to provide detailed clinical data on inflammatory and other biomarkers obtained from patients after acute knee trauma in order to (i) present a timeline of events that occur in the acute, subacute, and chronic post-traumatic phases and in PTOA, and (ii) to identify key factors present in the synovial fluid, serum/plasma and urine, leading to PTOA of the knee in 23-50% of individuals who had acute knee trauma. In this context, we additionally discuss methods of simulating knee trauma and inflammation in in vivo, ex vivo articular cartilage explant and in vitro chondrocyte models, and answer whether these models are representative of the clinical inflammatory stages following knee trauma. Moreover, we compare the pro-inflammatory cytokine concentrations used in such models and demonstrate that, compared to concentrations in the synovial fluid after knee trauma, they are exceedingly high. We then used the Bradford Hill Framework to present evidence that TNF-α and IL-6 cytokines are causal factors, while IL-1β and IL-17 are credible factors in inducing knee PTOA disease progresssion. Lastly, we discuss beneficial infrastructure for future studies to dissect the role of local vs. systemic inflammation in PTOA progression with an emphasis on early disease.

A roadmap to target interleukin-6 in osteoarthritis

Joint inflammation is present in the majority of OA patients and pro-inflammatory mediators, such as IL-6, are actively involved in disease progression. Increased levels of IL-6 in serum or synovial fluid from OA patients correlate with disease incidence and severity, with IL-6 playing a pivotal role in the development of cartilage pathology, e.g. via induction of matrix-degrading enzymes. However, IL-6 also increases expression of anti-catabolic factors, suggesting a protective role. Until now, this dual role of IL-6 is incompletely understood and may be caused by differential effects of IL-6 classic vs trans-signalling. Here, we review current evidence regarding the role of IL-6 classic- and trans-signalling in local joint pathology of cartilage, synovium and bone. Furthermore, we discuss targeting of IL-6 in experimental OA models and provide future perspective for OA treatment by evaluating currently available IL-6 targeting strategies.

Proinflammatory T cell polarization is already present in patients with early knee osteoarthritis

Background

Investigating the pathophysiological mechanisms of early osteoarthritis (OA) is of utmost interest since this stage holds the strongest promise for therapeutic interventions. The aims of this study were to analyze if synovial inflammation is already present in early OA and to characterize the involved cell populations, by investigating synovial fluid (SF) and synovial membrane (SM) of early OA patients for the presence and polarization status of CD4 T cells.

Methods

A quantitative analysis of CD4⁺ T cell infiltration in SF and SM compared to peripheral blood (PB) was performed in patients with early stages of OA. We further investigated intracellular staining (ICS), surface marker, and chemokine receptor expression profiles of CD4⁺ T cells in SF, SM, and PB, as well as cytokine expression in native SF and PB. Matched samples of SF, SM, and PB were harvested from 40 patients with early OA at the time of surgery. Early OA was confirmed by independent surgeons intraoperatively. Samples were analyzed by flow cytometry for surface markers and cytokines, which are preferentially expressed by distinct T cell subsets (Th1, Th2, Th17, regulatory T cells). Furthermore, we analyzed native SF and PB supernatants using MACSPlex for multiple cytokine expression profiles.

Results

SF and SM showed a distinct infiltration of CD4⁺ T lymphocytes, with significantly increased expression of chemokine receptors CXCR3/CCR5, cytokine IFN-γ (preferentially expressed by Th1 cells), and CD161 (preferentially expressed by IL-17 producing Th17 cells) compared to PB. Furthermore, the percentage of CD4⁺ T cells polarized to Treg was significantly increased in SM compared to SF and PB. No significant differences were observed for CCR3 and CCR4 (preferentially expressed by Th2 cells), although IL-4 values were significantly higher in SM and SF compared to PB. Cytokine analysis showed comparable results between PB and SF, with only IL-6 being significantly increased in SF.

Conclusions

Early OA joints show already significant inflammation through CD4⁺ T cell infiltration, with predominant Th1 cell polarization. Inflammation seems to be driven by direct proinflammatory cell interaction. Cytokine signaling seems to be negligible at the site of inflammation in early OA, with only IL-6 being significantly increased in SF compared to PB.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-020-02410-w.

CCL22 induces pro-inflammatory changes in fibroblast-like synoviocytes

Synovitis is common in patients with osteoarthritis (OA) and is associated with pain and disease progression. We have previously demonstrated that the chemokine C-C motif chemokine 22 (CCL22) induces chondrocyte apoptosis in vitro; however, the effects of CCL22 on the synovium remain unknown. Therefore, our goal was to investigate the effect of CCL22 on fibroblast-like synoviocytes (FLS). CCL22 treatment suppressed expression of IL-4 and IL-10 and promoted expression of S100A12 in FLS. The response of FLS to CCL22 was not dependent on the disease state of the joint (e.g., normal versus OA), but was instead correlated with the individuals' synovial fluid level of CCL22. CCL22 induction of S100A12 in FLS was attenuated after knockdown of CCR3, yet ligands of CCR3 (CCL7, CCL11) did not induce S100A12 expression. In the presence of CCL22, CCR3-positive FLS upregulate CCL22 and S100A12 driving a potential feedforward pro-inflammatory mechanism distinct from canonical CCL22 and CCR3 pathways.

Impact of Isolation Procedures on the Development of a Preclinical Synovial Fibroblasts/Macrophages in an In Vitro Model of Osteoarthritis

Simple Summary

In vitro models able to represent osteoarthritis (OA) synovial tissue (ST) inflammation are lacking. Therefore, we aimed to characterize OA ST and to compare mechanical and enzymatic digestion procedures to find the one that better preserve the heterogeneity of the main OA synovial cell populations: fibroblasts and macrophages. We demonstrated that typical macrophage phenotypical markers, like CD68, CD80 and CD163, were higher expressed on cells isolated with mechanical than enzymatic procedure. Moreover, we found that typical cytokines of inflammatory macrophages (i.e., TNFα) and anti-inflammatory macrophages (i.e., IL10) were also higher on mechanically isolated cells. Synovial fibroblasts were well conserved in both procedures. The definition of an OA ST model in vitro that better preserve the heterogeneity of specific cell populations represents a prerequisite for defining the real effects of new cell therapies or drugs for OA treatment, and could contribute to the reduction or avoidance of animal models.

Abstract

There is a lack ofin vitromodels able to properly represent osteoarthritis (OA) synovial tissue (ST). We aimed to characterize OA ST and to investigate whether a mechanical or enzymatic digestion procedures influence synovial cell functional heterogeneity in vitro. Procedures using mechanical nondigested fragments (NDF), synovial digested fragments (SDF), and filtrated synovial digested cells (SDC) were compared. An immunophenotypic profile was performed to distinguish synovial fibroblasts (CD55, CD73, CD90, CD106), macrophages (CD14, CD68), M1-like (CD80, CD86), and M2-like (CD163, CD206) synovial macrophages. Pro-inflammatory (interleukin 6 IL6), tumor necrosis factor alpha (TNFα), chemokine C-C motif ligand 3 (CCL3/MIP1α), C-X- motif chemokine ligand 10 (CXCL10/IP10) and anti-inflammatory (interleukin 10 (IL10)), transforming growth factor beta 1 (TGFβ1), C-C motif chemokine ligand 18 (CCL18) cytokines were evaluated. CD68 and CD163 markers were higher in NDF and SDF compared to the SDC procedure, while CD80, CD86, and CD206 were higher only in NDF compared to the SDC procedure. Synovial fibroblast markers showed similar percentages. TNFα, CCL3/MIP1α, CXCL10/IP10, and CCL18 were higher in NDF compared to SDC, but not compared to SDF. IL10 and TGFβ1 were higher in NDF than SDC at the molecular level, while IL6 did not show differences among procedures. We demonstrated that NDF isolation procedures better preserved the heterogeneity of specific OA synovial populations (fibroblasts, macrophages), fostering their use for testing new cell therapies or drugs for OA, reducing or avoiding the use of animal models.

Osteoarthritis: Prognosis and emerging therapeutic approach for disease management

Osteoarthritis (OA), a disorder of joints, is prevalent in older age. The contemporary cure for OA is aimed to confer symptomatic relief, consisting of temporary pain and swelling relief. In this paper, we discuss various modalities responsible for the onset of OA and associated with its severity. Inhibition of chondrocytes receptors such as DDR2, SDF-1, Asporin, and CXCR4 by specific pharmacological inhibitors attenuates OA, a critical step for finding potential disease modifying drugs. We critically analyzed recent OA studies with an emphasis on intermediate target molecules for OA intervention. We also explored some novel and safe treatments for OA by considering disease prognosis crosstalk with cellular signaling pathways.

Hepatocyte growth factor and matrix metalloprotease 2 levels in synovial fluid of the knee joint are correlated with clinical outcome of meniscal repair

BACKGROUND

The reoperation rate after primary meniscal repair is about 20%. Thus far, it has remained unclear whether there are distinct individual preconditions that may be associated with a better or worse outcome of this procedure. We therefore analysed typical biochemical mediators in the synovial fluid (SF) of patients with meniscus tear before arthroscopic meniscal refixation and correlated their concentrations to the occurrence of re-rupture after meniscus repair.

METHODS

In this study, 48 patients with meniscus ruptures were included. SF samples were taken intraoperatively prior to arthroscopy. Multiplex enzyme-linked immunosorbent assay (ELISA)-based methods were used to measure hepatocyte growth factor (HGF), interleukin-18 (IL-18), matrix metalloproteinases (MMP) MMP-1, MMP-2, MMP-9 and MMP-13 in the SF. At follow-up, the patients were classified into two groups: surgical success and surgical failure.

RESULTS

Ten out of 48 patients (20.8%) had to undergo revision surgery after meniscal repair (surgical failure). The median HGF in the surgical failure group was 2.4-times higher than in the surgical success group (P = .006), and the median MMP-2 was 1.8 times higher (P = .017). Concentration levels of the other tested proteins were not correlated with the success or failure of the meniscus surgery. There was weak evidence that both markers are indicators of an unsatisfactory healing process for meniscal refixation.

CONCLUSION

These results suggest that HGF and MMP-2 could serve as molecular markers to estimate the chances of healing success of meniscus repair and possibly to individualise therapy in meniscal surgery.

Infrapatellar Fat Pad/Synovium Complex in Early-Stage Knee Osteoarthritis: Potential New Target and Source of Therapeutic Mesenchymal Stem/Stromal Cells

The infrapatellar fat pad (IFP) has until recently been viewed as a densely vascular and innervated intracapsular/extrasynovial tissue with biomechanical roles in the anterior compartment of the knee. Over the last decade, secondary to the proposition that the IFP and synovium function as a single unit, its recognized tight molecular crosstalk with emerging roles in the pathophysiology of joint disease, and the characterization of immune-related resident cells with varying phenotypes (e.g., pro and anti-inflammatory macrophages), this structural complex has gained increasing attention as a potential therapeutic target in patients with various knee pathologies including osteoarthritis (KOA). Furthermore, the description of the presence of mesenchymal stem/stromal cells (MSC) as perivascular cells within the IFP (IFP-MSC), exhibiting immunomodulatory, anti-fibrotic and neutralizing activities over key local mediators, has promoted the IFP as an alternative source of MSC for cell-based therapy protocols. These complementary concepts have supported the growing notion of immune and inflammatory events participating in the pathogenesis of KOA, with the IFP/synovium complex engaging not only in amplifying local pathological responses, but also as a reservoir of potential therapeutic cell-based products. Consequently, the aim of this review is to outline the latest discoveries related with the IFP/synovium complex as both an active participant during KOA initiation and progression thus emerging as a potential target, and a source of therapeutic IFP-MSCs. Finally, we discuss how these notions may help the design of novel treatments for KOA through modulation of local cellular and molecular cascades that ultimately lead to joint destruction.

Increased chemokine RANTES in synovial fluid and its role in early-stage degenerative temporomandibular joint disease

BACKGROUND

Degenerative joint disease (DJD) of the temporomandibular joints (TMJs) in adolescents and young adults is closely associated with disc displacement without reduction (DDw/oR).

OBJECTIVE

This study aimed to determine the pathogenesis of early-stage TMJ DJD induced by DDw/oR.

METHODS

31 female subjects aged 12-30 years were enrolled, comprising 12 patients with DDw/oR without DJD, 13 with DDw/oR and early-stage DJD, and 6 healthy volunteers. The synovial fluid samples of the subjects were screened for 27 inflammatory-related cytokines using multiple cytokine array. Significantly increased cytokines and a key regulator of osteoclastogenesis "receptor activator of nuclear factor-κB ligand" (RANKL) were further determined by sandwich immunoassay. These factors were also assessed for the possible pathophysiologic actions on RAW264.7 cell proliferation, migration, osteoclastogenesis and bone-resorbing activity using Cell Counting Kit-8, Transwell system, tartrate-resistant acid phosphatase staining and osteo assay plates.

RESULTS

Macrophage-derived inflammatory protein-1 beta (MIP-1β) and regulated upon activation normal T cell expressed and secreted (RANTES) were found to vary significantly in relation to the controls. In contrast to an unchanged concentration of RANKL, a strong increase in the level of RANTES was detected in subjects with DDw/oR and early-stage DJD. MIP-1β concentrations were only elevated in subjects with DDw/oR without DJD. Functionally, both MIP-1β and RANTES could enhance macrophage migration in a concentration-dependent manner, while only RANTES exhibited a promoting effect on osteoclast formation and bone-resorbing activity.

CONCLUSIONS

Chemokine RANTES was significantly upregulated and might be a key regulator of osteoclastogenesis contributing to DDw/oR-induced early-stage TMJ DJD.

An update on the association between metabolic syndrome and osteoarthritis and on the potential role of leptin in osteoarthritis

Metabolic syndrome (MetS) has been associated with osteoarthritis (OA). Leptin, which is one of the markers of MetS, has been associated with OA pathophysiology. This study aimed to provide an update on the association between MetS and OA and on the potential role of leptin in OA. In this review, we summarized the current knowledge of the association between MetS and OA and updated the evidence on the potential role of leptin in OA. Clinical studies have investigated the epidemiologic association between MetS or its components and OA. Results suggested strong epidemiologic associations between MetS and OA, especially in the Asian population. Animal studies also indicated that metabolic dysregulation may lead to OA pathogenesis. The systemic role of MetS in OA pathophysiology is associated with obesity-related inflammation, the beneficial role of n-3 polyunsaturated fatty acids and deleterious role of cholesterol, physical inactivity, hypertension-induced subchondral ischemia, dyslipidemia-induced ectopic lipid deposition in chondrocytes, hyperglycemia-induced local effects of oxidative stress and advanced glycation end-products, low-grade systemic inflammation, and obesity-related adipokines by inducing the expression of proinflammtory factors. Leptin levels in serum/plasma and synovial fluid were associated with joint pain, radiographic progression, bone formation biomarkers, cartilage volume, knee OA incidence, and total joint arthroplasty in OA patients. Elevated leptin expression and increased effect of leptin on infrapatellar fat pad, synovium, articular cartilage, and bone were also involved in the pathogenesis of OA. Current knowledge indicates a convincing epidemiologic association between MetS and OA, especially in the Asian population. Animal studies have also shown that metabolic dysregulation may lead to OA pathogenesis. Accumulating evidence suggests that leptin may play a potential role in OA pathogenesis. Therefore, leptin and its receptor may be an emerging target for intervention in metabolic-associated OA.

Identifying effector molecules, cells, and cytokines of innate immunity in OA

Inflammatory changes are observed in affected joints of osteoarthritis (OA) patients and are thought to be involved in the pathology that develops along OA progression. This narrative review provides an overview of the various cell types that are present in the joint during OA and which alarmins, cytokines, chemokines, growth factors, and other mediators they produce. Moreover, the involvement of more systemic processes like inflammaging and its associated cellular senescence in the context of OA are discussed.