Elevated synovial fluid levels of interleukin-6 and tumor necrosis factor associated with early experimental canine osteoarthritis

Association of Serum Biochemical Biomarker Profiles of Joint Tissue Inflammation and Cartilage Metabolism With Posttraumatic Osteoarthritis-Related Symptoms at 12 Months After ACLR

BACKGROUND

Anterior cruciate ligament injury and anterior cruciate ligament reconstruction (ACLR) are risk factors for symptomatic posttraumatic osteoarthritis (PTOA). After ACLR, individuals demonstrate altered joint tissue metabolism indicative of increased inflammation and cartilage breakdown. Serum biomarker changes have been associated with tibiofemoral cartilage composition indicative of worse knee joint health but not with PTOA-related symptoms.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine associations between changes in serum biomarker profiles from the preoperative sample collection to 6 months after ACLR and clinically relevant knee PTOA symptoms at 12 months after ACLR. It was hypothesized that increases in biomarkers of inflammation, cartilage metabolism, and cartilage degradation would be associated with clinically relevant PTOA symptoms after ACLR.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Individuals undergoing primary ACLR were included (N = 30). Serum samples collected preoperatively and 6 months after ACLR were processed to measure markers indicative of changes in inflammation (ie, monocyte chemoattract protein 1 [MCP-1]) and cartilage breakdown (ie, cartilage oligomeric matrix protein [COMP], matrix metalloproteinase 3, ratio of type II collagen breakdown to type II collagen synthesis). Knee injury and Osteoarthritis Outcome Score surveys were completed at 12 months after ACLR and used to identify participants with and without clinically relevant PTOA-related symptoms. K-means cluster analyses were used to determine serum biomarker profiles. One-way analyses of variance and logistic regressions were used to assess differences in Knee injury and Osteoarthritis Outcome Score subscale scores and clinically relevant PTOA-related symptoms between biomarker profiles.

RESULTS

Two profiles were identified and characterized based on decreases (profile 1: 67% female; age, 21.4 ± 5.1 years; body mass index, 24.4 ± 2.4) and increases (profile 2: 33% female; age, 21.3 ± 3.2 years; body mass index, 23.4 ± 2.6) in sMCP-1 and sCOMP preoperatively to 6 months after ACLR. Participants with profile 2 did not demonstrate differences in knee pain, symptoms, activities of daily living, sports function, or quality of life at 12 months after ACLR compared to those with profile 1 (P = .56-.81; η2 = 0.002-0.012). No statistically significant associations were noted between biomarker profiles and clinically relevant PTOA-related symptoms (odds ratio, 1.30; 95% CI, 0.23-6.33).

CONCLUSION

Serum biomarker changes in MCP-1 and sCOMP within the first 6 months after ACLR were not associated with clinically relevant PTOA-related symptoms.

Effect of duloxetine in temporomandibular joint disorders: A comparison with arthrocentesis

Purpose

This study was conducted to compare the efficacy of temporomandibular joint (TMJ) arthrocentesis, duloxetine therapy alone, and duloxetine in combination with TMJ arthrocentesis in the treatment of painful TMJ.

Materials and Methods

Thirty patients with TMJ pain were included in the study who were divided into three groups with ten patients in each group. Group A included patients having only TMJ arthrocentesis; in Group B, only duloxetine therapy (30 mg) was given twice a day orally for 3 months; and in Group C, a combination of TMJ arthrocentesis with duloxetine therapy (30 mg) was given twice a day orally for 3 months. Patients were followed at regular interval of the 1^st day, 5^th day, 7^th day, 4^th week, 6^th week, and 12^th week and assessed in terms of pain, maximum mouth opening (mm), clicking, Hospital Anxiety and Depression Rating Scale and estimation of interleukin-6 (IL-6). The data collected were compiled and statistically analyzed.

Results

The pain was found to be significantly lower in Group C than other groups at weeks 4, 6, and 12. In Group C, mouth opening increased significantly than Groups A and B on subsequent follow-ups. On biochemical analysis of IL-6 levels in lavage fluid, a significant decrease was observed in levels of IL-6 in lavage fluid in Groups A and C postoperatively.

Conclusion

The present study states that pain was observed to be much less after arthrocentesis along with duloxetine therapy. This combination therapy leads to much better and faster outcome, but still, long-term follow-ups with larger number of patients are required.

Correlation between synovial fluid cytokine concentrations and limb function in normal dogs and in dogs with lameness from spontaneous osteoarthritis

OBJECTIVE

To determine the relationship between synovial biomarker concentrations and severity of lameness and to assess the ability to differentiate normal from osteoarthritic joints with synovial biomarker concentrations.

STUDY DESIGN

Prospective clinical study.

SAMPLE POPULATION

Twelve hounds with no evidence of osteoarthritis (OA) and 27 client-owned dogs with unilateral lameness and joint pain in a single joint from naturally occurring OA.

METHODS

Enrollment in the OA group required a history of lameness, radiographic evidence of OA on orthogonal joint radiographs, and ≥6% gait asymmetry between contralateral limbs. The concentrations of 14 synovial OA biomarkers in synovial samples obtained after gait analysis were measured with enzyme-linked immunosorbent assays and compared between normal and OA joints.

RESULTS

Concentrations of monocyte chemoattractant protein (MCP)-1, substance P, interleukin (IL)-6, IL-8, KC-like, matrix metalloproteinase (MMP)-1, and MMP-3 were greater (P ≤ .05) in OA than in normal joints. The concentrations of bradykinin and tissue inhibitors of metalloproteinase-4 were decreased in OA compared with normal joints. Monocyte chemoattractant protein 1 was identified as the most accurate marker to distinguish OA from normal joints. No correlation was detected between any OA biomarker concentration, individually or in combination, and severity of gait asymmetry at the walk.

CONCLUSION

Differences in proinflammatory and anti-inflammatory biomarkers were detected between OA and normal joints, but no relationship was identified between biomarker concentrations and gait asymmetry in dogs with OA.

CLINICAL IMPACT

This information will help guide future studies to elucidate how factors such as disease chronicity, severity, and etiology affect these relationships.

Inflammatory molecules produced by meniscus and synovium in early and end-stage osteoarthritis: a coculture study

The aim of this study was to identify the molecules and pathways involved in the cross-talk between meniscus and synovium that may play a critical role in osteoarthritis (OA) pathophysiology. Samples of synovium and meniscus were collected from patients with early and end-stage OA and cultured alone or cocultured. Cytokines, chemokines, metalloproteases, and their inhibitors were evaluated at the gene and protein levels. The extracellular matrix (ECM) changes were also investigated. In early OA cultures, higher levels of interleukin-6 (IL-6) and IL-8 messenger RNA were expressed by synovium and meniscus in coculture compared with meniscus cultured alone. RANTES release was significantly increased when the two tissues were cocultured compared with meniscus cultured alone. Increased levels of matrix metalloproteinase-3 (MMP-3) and MMP-10 proteins, as well as increased release of glycosaminoglycans and aggrecan CS846 epitope, were observed when synovium was cocultured with meniscus. In end-stage OA cultures, increased levels of IL-8 and monocyte chemoattractant protein-1 (MCP-1) proteins were released in cocultures compared with cultures of meniscus alone. Chemokine (C-C motif) ligand 21 (CCL21) protein release was higher in meniscus cultured alone and in coculture compared with synovium cultured alone. Increased levels of MMP-3 and 10 proteins were observed when tissues were cocultured compared with meniscus cultured alone. Aggrecan CS846 epitope release was increased in cocultures compared with cultures of either tissue cultured alone. Our study showed the production of inflammatory molecules by synovium and meniscus which could trigger inflammatory signals in early OA patients, and induce ECM loss in the progressive and final stages of OA pathology.

The Pathobiology of the Meniscus: A Comparison Between the Human and Dog

Serious knee pain and related disability have an annual prevalence of approximately 25% on those over the age of 55 years. As curative treatments for the common knee problems are not available to date, knee pathologies typically progress and often lead to osteoarthritis (OA). While the roles that the meniscus plays in knee biomechanics are well characterized, biological mechanisms underlying meniscus pathophysiology and roles in knee pain and OA progression are not fully clear. Experimental treatments for knee disorders that are successful in animal models often produce unsatisfactory results in humans due to species differences or the inability to fully replicate disease progression in experimental animals. The use of animals with spontaneous knee pathologies, such as dogs, can significantly help addressing this issue. As microscopic and macroscopic anatomy of the canine and human menisci are similar, spontaneous meniscal pathologies in canine patients are thought to be highly relevant for translational medicine. However, it is not clear whether the biomolecular mechanisms of pain, degradation of extracellular matrix, and inflammatory responses are species dependent. The aims of this review are (1) to provide an overview of the anatomy, physiology, and pathology of the human and canine meniscus, (2) to compare the known signaling pathways involved in spontaneous meniscus pathology between both species, and (3) to assess the relevance of dogs with spontaneous meniscal pathology as a translational model. Understanding these mechanisms in human and canine meniscus can help to advance diagnostic and therapeutic strategies for painful knee disorders and improve clinical decision making.

MMP-2 as an early synovial biomarker for cranial cruciate ligament disease in dogs

Objectives: To measure the activity of matrix metalloproteinases (MMP)-2 and -9 in synovial fluid from the stifle joints of dogs with cranial cruciate ligament (CrCL) rupture and to compare that to values from contralateral stifle joints and dogs with clinically normal stifle joints. Additionally, the C-reactive protein (CRP) levels were also measured.

Methods: Fourteen large breed dogs with unilateral CrCL rupture and 11 large breed normal dogs were included in this prospective clinical study. Synovial fluid was collected from CrCL-ruptured stifle joints, contralateral clinically normal stifle joints of the same dogs, and stifle joints of normal dogs. Serum was also collected. Synovial fluid activities of MMP-2 and MMP-9 and serum CRP level were measured.

Results: The MMP-2 activity in synovial fluid was significantly higher in CrCL-ruptured joints compared to contralateral joints and to stifles from normal dogs. There was no significant difference in activity of MMP-2 in contralateral joints of CrCL-ruptured dogs compared to normal dogs. Both serum CRP level and MMP-9 activity did not differ significantly between the studied conditions.

Clinical significance: It was confirmed that MMP-2 activity is significantly related to CrCL rupture, but there was a failure to demonstrate any significant increase in the contralateral joints compared to the stifle joints of normal dogs. The MMP-2 involvement in progressing CrCL disease still has to be defined.

Targeting the D Series Resolvin Receptor System for the Treatment of Osteoarthritis Pain

Objective

Pain is a major symptom of osteoarthritis (OA); currently available analgesics either do not provide adequate pain relief or are associated with serious side effects. The aim of this study was to investigate the therapeutic potential of targeting the resolvin receptor system to modify OA pain and pathology.

Methods

Gene expression of 2 resolvin receptors (ALX and ChemR23) was quantified in synovium and medial tibial plateau specimens obtained from patients with OA at the time of joint replacement surgery. Two models of OA joint pain were used for the mechanistic studies. Gene expression in the joint and central nervous system was quantified. The effects of exogenous administration of the D series resolvin precursor 17(R)‐hydroxy‐docosahexaenoic acid (17[R]‐HDoHE) on pain behavior, joint pathology, spinal microglia, and astroglyosis were quantified. Plasma levels of relevant lipids, resolvin D2, 17(R)‐HDoHE, and arachidonic acid, were determined in rats, using liquid chromatography tandem mass spectrometry.

Results

There was a positive correlation between resolvin receptor and interleukin‐6 (IL‐6) expression in human OA synovial and medial tibial plateau tissue. In rats, synovial expression of ALX was positively correlated with expression of IL‐1β, tumor necrosis factor, and cyclooxygenase 2. Treatment with 17(R)‐HDoHE reversed established pain behavior (but not joint pathology) in 2 models of OA pain. This was associated with a significant elevation in the plasma levels of resolvin D2 and a significant reduction in astrogliosis in the spinal cord in the monosodium iodoacetate–induced OA rat model.

Conclusion

Our preclinical data demonstrate the robust analgesic effects of activation of the D series resolvin pathways in 2 different animal models of OA. Our data support a predominant central mechanism of action in clinically relevant models of OA pain.

The effect of intra-articular botulinum toxin A on substance P, prostaglandin E2, and tumor necrosis factor alpha in the canine osteoarthritic joint

Background

Recently, intra-articular botulinum toxin A (IA BoNT A) has been shown to reduce joint pain in osteoarthritic dogs. Similar results have been reported in human patients with arthritis. However, the mechanism of the antinociceptive action of IA BoNT A is currently not known. The aim of this study was to explore this mechanism of action by investigating the effect of IA BoNT A on synovial fluid (SF) and serum substance P (SP), prostaglandin E₂ (PGE₂), and tumor necrosis factor alpha (TNF-α) in osteoarthritic dogs. Additionally, the aim was to compare SF SP and PGE₂ between osteoarthritic and non-osteoarthritic joints, and investigate associations between SP, PGE₂, osteoarthritic pain, and the signalment of dogs. Thirty-five dogs with chronic naturally occurring osteoarthritis and 13 non-osteoarthritic control dogs were included in the study. Osteoarthritic dogs received either IA BoNT A (n = 19) or IA placebo (n = 16). Serum and SF samples were collected and osteoarthritic pain was evaluated before (baseline) and 2 and 8 weeks after treatment. Osteoarthritic pain was assessed with force platform, Helsinki Chronic Pain Index, and joint palpation. Synovial fluid samples were obtained from control dogs after euthanasia. The change from baseline in SP and PGE₂ concentration was compared between the IA BoNT A and placebo groups. The synovial fluid SP and PGE₂ concentration was compared between osteoarthritic and control joints. Associations between SP, PGE₂, osteoarthritic pain, and the signalment of dogs were evaluated.

Results

There was no significant change from baseline in SP or PGE₂ after IA BoNT A. Synovial fluid PGE₂ was significantly higher in osteoarthritic compared to control joints. Synovial fluid PGE₂ correlated with osteoarthritic pain. No associations were found between SP or PGE₂ and the signalment of dogs. The concentration of TNF-α remained under the detection limit of the assay in all samples.

Conclusions

The results suggest that the antinociceptive effect of IA BoNT A in the joint might not be related to the inhibition of SP nor PGE₂. Synovial fluid PGE₂, but not SP, could be a marker for chronic osteoarthritis and pain in dogs.

Differences in levels of inflammatory mediators in meniscal and synovial tissue of patients with meniscal lesions

BACKGROUND

Meniscal injuries are a risk factor for osteoarthritis (OA). While a mechanical pathway between meniscal injury and OA has been described, the biological effects of inflammation on this pathway have yet to be clarified. The aim of our study was to compare levels of specific inflammatory mediators, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and nerve growth factor (NGF), in injured and uninjured meniscal tissue and related knee joint synovium.

METHODS

Tissue samples were obtained from 19 patients, 31.1 ± 13.6 years old, who underwent arthroscopic partial meniscectomy. For analysis, tissue samples were categorized into the following groups: injured meniscal site (IM), non-injured meniscal site (NIM), synovium 'nearest' the lesion (NS), and synovium from the opposite knee compartment, 'farthest' synovium (FS). Levels of inflammatory mediators were determined using enzyme-linked immunosorbent assay and between-group differences (IM and NIM; NS and FS) were evaluated using the Wilcoxon signed-rank test. The association between pre-operative pain score and the level of each inflammatory mediator was evaluated using Spearman's correlation.

RESULTS

Higher levels of TNF-α and IL-6 were identified in the IM tissue, compared to NIM (p <0.05). IL-6 levels were also higher in the NS compared to the FS (p <0.05). There was no correlation between pre-operative pain score and level of each inflammatory mediator.

CONCLUSIONS

Our outcomes confirm a local increase in inflammatory mediator levels, in both meniscal and synovial tissue, which could contribute to development of OA. Management of these biological effects of meniscal injury might be warranted.

Ketamine attenuates osteoarthritis of the knee via modulation of inflammatory responses in a rabbit model

The aim of the present study was to investigate the efficacy of ketamine in attenuating osteoarthritis (OA) and modulating the expression of inflammatory mediators. A rabbit OA model was established by knee immobilization using plaster bandages. After six weeks, rabbits were randomly allocated into four groups (n=6/group): Normal saline, Ket₆₀, Ket₁₀₀, and Ket₂₀₀ and twice a week for four weeks the rabbits received an intra-articular injection of saline, or 60, 100 or 200 µmol/l ketamine, respectively. One week after the final injection, samples of synovial membrane, synovial fluid and articular cartilage were isolated. The pathological changes were assessed by general observation, hematoxylin and eosin staining and Alcian blue/periodic-acid Schiff staining. Cartilage pathology was assessed using Mankin's scoring system. Tumor necrosis factor (TNF)-α and interleukin (IL)-10 levels in the synovial fluid were measured by enzyme-linked immunosorbent assays. The nuclear factor (NF)-κB p65 subunit expression level in cartilage samples was determined by immunohistochemistry. OA was characterized by morphological changes in the articular surface, cartilage lesions, infiltration of inflammatory cells and a significantly increased Mankin's score. Elevated TNF-α and reduced IL-10 levels in the synovial fluid, along with increased p65 expression levels in the cartilage were observed in OA rabbits. Intra-articular injection of ketamine ameliorated the pathological characteristics of OA, reduced the Mankin's score, decreased TNF-α and NF-κB p65 expression levels, and increased the level of IL-10 expression in a dose-dependent manner. Thus is was demonstrated that Ketamine suppresses the inflammatory response in OA by modulating inflammatory mediator expression levels in a rabbit model of OA.

Interleukin-6 and tumor necrosis factor alpha in synovial fluid are associated with progression of radiographic knee osteoarthritis in subjects with previous meniscectomy

OBJECTIVE

To explore potential associations between proinflammatory cytokines in synovial fluid and progression of osteoarthritis (OA) in meniscectomized subjects.

DESIGN

We studied 132 subjects on average 18 years after meniscectomy, with a second examination 4-10 years later. We measured concentrations of interleukin (IL)-6, -8 and tumor necrosis factor (TNF)-α by multiplex immunoassay, graded radiographic features of tibiofemoral and patellofemoral OA according to the Osteoarthritis Research Society International (OARSI) atlas, scored patient-reported outcomes using the Knee Injury and Osteoarthritis Outcome Score (KOOS), and used logistic regression (adjusted for age, gender, body mass index, and time between examinations) for assessment of associations.

RESULTS

Higher first examination concentrations of IL-6 and TNF-α were associated with increased risk for subsequent osteophyte progression (odds ratios (OR); 95% confidence intervals 1.05; 1.00-1.09 and 1.35; 1.03-1.75). Higher second examination concentrations of TNF-α were associated with having progressed in loss of joint space (OR 1.70; 1.15-2.52) or having worsened in the activity of daily living subscale of KOOS (OR 1.50; 1.07-2.09) in the preceding years. Subjects with increasing concentrations of IL-6 or TNF-α between examinations were five times more likely to have progressed in joint space narrowing between the same examinations, as compared to those with stable or decreasing concentrations (OR 5.17; 1.54-17.32 and 5.01; 1.32-18.92).

CONCLUSIONS

In subjects with previous meniscectomy, higher or over time increasing synovial fluid levels of IL-6 and TNF-α seems to be associated with increased risk for progression of radiographic OA.

Tumor necrosis factor-alpha levels in the synovial fluid of patients with temporomandibular joint internal derangement

PURPOSE

The purpose of this study was to investigate the level of tumor necrosis factor-alpha (TNF-α) in the synovial fluid (SF) of patients with temporomandibular joint (TMJ) internal derangement and to show the relationship between the level of TNF-α and the severity of the disease.

MATERIALS AND METHODS

Arthrocentesis was performed on 32 female and five male patients (aged between 17 and 45) referred to our clinic with the complaint of TMJ pain and discomfort. TNF-α levels were determined in the SF samples obtained during arthrocentesis. As a measure of pain, visual analog scale (VAS) scores were also evaluated.

RESULTS

There were statistically significant differences in VAS scores between the stages. VAS scores were found to be elevated as the stage of disease progressed. Increased levels of TNF-α were found in progressive stages of internal derangement.

CONCLUSION

In our study, both SF TNF-α levels and pain levels (VAS scores) were found to be increased in patients with internal derangement as the stage of the disease progresses. TNF-α might contribute to the pathogenesis of synovitis and the degeneration of the TMJ cartilage and bone.

The anti-inflammatory and matrix restorative mechanisms of platelet-rich plasma in osteoarthritis

BACKGROUND

Intra-articular (IA) treatment with platelet-rich plasma (PRP) for osteoarthritis (OA) results in improved patient-reported pain and function scores.

PURPOSE

To measure the effects of PRP and high molecular weight hyaluronan (HA) on the expression of anabolic and catabolic genes and on the secretion of nociceptive and inflammatory mediators from OA cartilage and synoviocytes.

STUDY DESIGN

Controlled laboratory study.

METHODS

Synovium and cartilage harvested from patients undergoing total knee arthroplasty were co-cultured with media of PRP or HA. Tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-1β were measured in the media by enzyme-linked immunosorbent assay. Hyaluronan synthase-2 (HAS-2), matrix metalloproteinase-1 (MMP-1), MMP-13, and TNF-α genes were measured in synoviocytes by reverse transcription polymerase chain reaction (RT-PCR). Collagen type I α1 (COL1A1), COL2A1, aggrecan (ACAN), and MMP-13 gene expression were measured in cartilage by quantitative RT-PCR.

RESULTS

Media TNF-α concentration was decreased in PRP and HA compared with control cultures (PRP = 6.94 pg/mL, HA = 6.39 pg/mL, control = 9.70 pg/mL; P ≤ .05). Media IL-6 concentration was decreased in HA compared with PRP and control (HA = 5027 pg/mL, PRP = 5899 pg/mL, control = 5613 pg/mL; P ≤ .05). Media IL-1β was below detectable concentrations (<0.1 pg/mL) in all samples. Synoviocyte MMP-13 expression was decreased in PRP compared with HA and control (PRP = 10.1, HA = 12.8, control = 13.5; P ≤ .05). Synoviocyte HAS-2 expression was increased in PRP compared with HA and control (PRP = 12.1, HA = 9.8, control = 8.7; P ≤ .05). Cartilage ACAN expression was increased in PRP compared with HA, but neither was different from control (PRP = 8.8, HA = 7.7, control = 7.6; P ≤ .05); COL1A1 expression was increased in HA compared with PRP, but neither was different from control (PRP = 14.9, HA = 13.5, control = 12.9; P ≤ .05). Neither platelet nor leukocyte concentration had a significant effect on outcome measurements (gene or protein expression data) in cartilage or synoviocytes (P > .05).

CONCLUSION

Both PRP and HA treatments of OA joint tissues result in decreased catabolism, but PRP treatment also resulted in a significant reduction of MMP-13, an increase in HAS-2 expression in synoviocytes, and an increase in cartilage synthetic activity compared with HA. These results indicate that PRP acts to stimulate endogenous HA production and decrease cartilage catabolism. Platelet-rich plasma showed similar effects as HA in the suppression of inflammatory mediator concentration and expression of their genes in synoviocytes and cartilage.

CLINICAL RELEVANCE

The antinociceptive and anti-inflammatory activities of PRP support its use in OA joints to reduce pain and modulate the disease process. This study supports further clinical investigations of IA PRP for the treatment of OA.

CCN4 induces IL-6 production through αvβ5 receptor, PI3K, Akt, and NF-κB singling pathway in human synovial fibroblasts

Introduction

Osteoarthritis (OA) is the most common degenerative joint disease that is involved in the degradation of articular cartilage. The exact etiology of OA is not completely understood. CCN4 is related to up-regulation in the cartilage of patients with osteoarthritis. Previous studies have shown that CCN4 might be associated with the pathogenesis of OA, but the exact signaling pathways in CCN4-mediated IL-6 expression in synovial fibroblasts (SF) are largely unknown. Therefore, we explored the intracellular signaling pathway involved in CCN4-induced IL-6 production in human synovial fibroblast cells.

Methods

CCN4-induced IL-6 production was assessed with quantitative real-time qPCR and ELISA. The mechanisms of action of CCN4 in different signaling pathways were studied by using Western blotting. Neutralizing antibodies of integrin were used to block the integrin signaling pathway. Luciferase assays were used to study IL-6 and NF-κB promoter activity. Immunocytochemistry was used to examine the translocation activity of p65.

Results

Osteoarthritis synovial fibroblasts (OASFs) showed significant expression of CCN4 and the expression was higher than in normal SFs. OASF stimulation with CCN4 induced concentration- and time-dependent increases in IL-6 production. Pretreatment of OASFs with αvβ5 but not α5β1 and αvβ3 integrin antibodies reduced CCN4-induced IL-6 production. CCN4-mediated IL-6 production was attenuated by PI3K inhibitor (LY294002 and Wortmannin), Akt inhibitor (Akti), and NF-κB inhibitor (PDTC and TPCK). Stimulation of cells with CCN4 also increased PI3K, Akt, and NF-κB activation.

Conclusions

Our results suggest that CCN4 activates αvβ5 integrin, PI3K, Akt, and NF-κB pathways, leading to up-regulation of IL-6 production. According to our results, CCN4 may be an appropriate target for drug intervention in OA in the future.

Oxidative stress in secondary osteoarthritis: from cartilage destruction to clinical presentation?

Due to an increasing life expectance, osteoarthritis (OA) is one of the most common chronic diseases. Although strong efforts have been made to regenerate degenerated joint cartilage, OA is a progressive and irreversible disease up to date. Among other factors the dysbalance between free radical burden and cellular scavenging mechanisms defined as oxidative stress is a relevant part of OA pathogenesis. Here, only little data are available about the mediation and interaction between different joint compartments. The article provides a review of the current literature regarding the influence of oxidative stress on cellular aging, senescence and apoptosis in different joint compartments (cartilage, synovial tissue and subchondral bone). Free radical exposure is known to promote cellular senescence and apoptosis. Radical oxygen species (ROS) involvement in inflammation, fibrosis control and pain nociception has been proven. The data from literature indicates a link between free radical burden and OA pathogenesis mediating local tissue reactions between the joint compartments. Hence, oxidative stress is likely not only to promote cartilage destruction but also to be involved in inflammative transformation, promoting the transition from clinically silent cartilage destruction to apparent OA. ROS induced by exogenous factors such as overload, trauma, local intraarticular lesion and consecutive synovial inflammation cause cartilage degradation. In the affected joint, free radicals mediate disease progression. The interrelationship between oxidative stress and OA etiology might provide a novel approach to the comprehension and therefore modification of disease progression and symptom control.

Physiology and pathophysiology of nitrosative and oxidative stress in osteoarthritic joint destruction

Osteoarthritis (OA) is one of the most common chronic diseases, with increasing importance due to increased life expectancy. On a cellular level, the pathophysiology of joint function impairment and ultimate destruction associated with OA remains poorly understood. Free radicals are highly reactive molecules involved in both normal intracellular signal transduction and degenerative cellular processes. An imbalance between the free radical burden and cellular scavenging mechanisms, defined as oxidative stress, has been identified as a relevant factor in OA pathogenesis. This literature review elucidates the involvement of nitrosative and oxidative stress in cellular ageing in joints, cell senescence, and apoptosis. Free radical exposure is known to promote cellular senescence and apoptosis, and the involvement of radical oxygen species (ROS) in inflammation, fibrosis control, and pain nociception has been proven. A relatively novel approach to OA pathophysiology considers the joint to be a dynamic system consisting of 3, continuously interacting compartments, cartilage, synovial tissue, and subchondral bone. Current knowledge concerning free radical involvement in paracrine signalling in OA is reviewed. The interrelationship between oxidative imbalances and OA pathophysiology may provide a novel approach to the comprehension, and therefore modification, of OA disease progression and symptom control.

Associations between proinflammatory cytokines in the synovial fluid and radiographic grading and pain-related scores in 47 consecutive patients with osteoarthritis of the knee

BACKGROUND

One of the sources of knee pain in osteoarthritis (OA) is believed to be related to local chronic inflammation of the knee joints, which involves the production of inflammatory cytokines such as tumor necrosis factor alpha (TNFα), interleukin (IL)-6, and nerve growth factor (NGF) in the synovial membrane, and these cytokines are believed to promote pathological OA. In the present study, correlations between proinflammatory cytokines in knee synovial fluid and radiographic changes and functional scores and pain scores among OA patients were examined.

METHODS

Synovial fluid was harvested from the knees of 47 consecutive OA patients, and the levels of TNFα, IL-6, and NGF were measured using enzyme-linked immunosorbent assays. Osteoarthritic knees were classified using Kellgren-Lawrence (KL) grading (1-4). The Western Ontario and McMaster University Osteoarthritis Index (WOMAC) was used to assess self-reported physical function, pain, and stiffness.

RESULTS

TNFα and IL-6 were detectable in knee synovial, whereas NGF was not. TNFα was not correlated with the KL grade, whereas IL-6 had a significantly negative correlation. We observed differences in the correlations between TNFα and IL-6 with WOMAC scores and their subscales (pain, stiffness, and physical function). TNFα exhibited a significant correlation with the total score and its 3 subscales, whereas IL-6 exhibited a moderately significant negative correlation only with the subscale of stiffness.

CONCLUSIONS

The present study demonstrated that the concentrations of proinflammatory cytokines are correlated with KL grades and WOMAC scores in patients with knee OA. Although TNFα did not have a significant correlation with the radiographic grading, it was significantly associated with the WOMAC score. IL-6 had a significant negative correlation with the KL grading, whereas it had only a weakly significant correlation with the subscore of stiffness. The results suggest that these cytokines play a role in the pathogenesis of synovitis in osteoarthritic knees in different ways: TNFα is correlated with pain, whereas IL-6 is correlated with joint function.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Cytokine mRNA expression in synovial fluid of affected and contralateral stifle joints and the left shoulder joint in dogs with unilateral disease of the stifle joint

OBJECTIVE

To examine mRNA expression of cytokines in synovial fluid (SF) cells from dogs with cranial cruciate ligament (CrCL) rupture and medial patellar luxation (MPL) and determine mRNA expression for 3 joints (affected stifle, unaffected contralateral stifle, and left shoulder joints) in dogs with unilateral CrCL rupture.

SAMPLE POPULATION

29 stifle joints with CrCL rupture (29 dogs), 8 stifle joints with MPL (7 dogs), and 24 normal stifle joints (16 clinically normal dogs).

PROCEDURES

Immediately before reconstructive surgery, SF was aspirated from the cruciate-deficient stifle joint or stifle joint with MPL. Fourteen of 29 dogs had unilateral CrCL rupture; SF was also aspirated from the unaffected contralateral stifle joint and left shoulder joint. Those 14 dogs were examined 6 and 12 months after reconstructive surgery. Total RNA was extracted from SF cells and reverse transcription-PCR assay was performed to obtain cDNA. Canine-specific cytokine mRNA expression was determined by use of a real-time PCR assay.

RESULTS

Interleukin (IL)-8 and -10 and interferon-gamma expression differed significantly between dogs with arthropathies and dogs with normal stifle joints. For the 14 dogs with unilateral CrCL rupture, a significant difference was found for IL-8 expression. Before reconstructive surgery, IL-8 expression differed significantly between the affected stifle joint and left shoulder joint or contralateral stifle joint. Six months after surgery, IL-8 expression was significantly increased in the unaffected contralateral stifle joint, compared with the shoulder joint.

CONCLUSIONS AND CLINICAL RELEVANCE

No conclusions can be made regarding the role of the examined cytokines in initiation of CrCL disease.

MRI CHARACTERISTICS AND HISTOLOGY OF BONE MARROW LESIONS IN DOGS WITH EXPERIMENTALLY INDUCED OSTEOARTHRITIS

Signal changes within the bone marrow adjacent to osteoarthritic joints are commonly seen on magnetic resonance (MR) images in humans and in dogs. The histological nature of these lesions is poorly known. In this study, we describe the MR imaging of bone marrow lesions adjacent to the stifle joints of dogs with experimental osteoarthritis over 13 months. Histology of the proximal tibia at the end of the study was compared with the last MR imaging findings. In five adult dogs, the left cranial cruciate ligament was transected. Post-operatively, MR imaging was performed at 1, 2, 3, 4, 6, 8, and 13 months. Dogs were euthanised after 13 months and histological specimen of the proximal tibia were evaluated. Bone marrow edema like MR imaging signal changes were seen in every MR examination of all dogs in one or more locations of the proximal tibia and the distal femur. Lesions varied in size and location throughout the whole study with the exception of constantly seen lesions in the epiphyseal and metaphyseal region at the level of the tibial eminence. On histology, hematopoiesis and myxomatous transformation of the bone marrow and/or intertrabecular fibrosis without signs of bone marrow edema were consistent findings in the areas corresponding to the MR imaging signal changes. We conclude that within the bone marrow, zones of increased signal intensity on fat suppressed MR images do not necessarily represent edema but can be due to cellular infiltration. Contrary to humans, hematopoiesis is seen in bone marrow edema-like lesions in this canine model of osteoarthritis.

Proinflammatory Cytokine Activities, Matrix Metalloproteinase-3 Activity, and Sulfated Glycosaminoglycan Content in Synovial Fluid of Dogs with Naturally Acquired Cranial Cruciate Ligament Rupture

OBJECTIVE

To measure and compare activities of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and matrix metalloproteinase-3 (MMP-3); as well as sulfated glycosaminoglycan (S-GAG) content in synovial fluid from dogs with cranial cruciate ligament rupture (CCLR) and dogs with clinically normal stifles. To determine whether correlations exist between demographic and disease-related variables and these synovial markers.

STUDY DESIGN

Prospective clinical study.

ANIMALS

Dogs with CCLR (n=23) and Beagles with normal stifle joints (n=21).

METHODS

Synovial fluid activities of proinflammatory cytokines (IL-1beta, IL-6, and TNF-alpha) were determined by bioassay. MMP-3 activity was measured using fluorogenic substrate. S-GAG contents were determined by dimethylmethylene blue dye-binding assay. Mann-Whitney U-test was used to compare results from CCLR joints with normal controls. Spearman's rank correlation test was used to evaluate associations between demographic and disease-related markers and synovial markers.

RESULTS

Mean values for synovial markers were significantly higher in CCLR joints compared with controls. IL-1beta and MMP-3 were positively correlated with lameness duration.

CONCLUSIONS

Activities of proinflammatory cytokines, MMP-3 activity and S-GAG contents were significantly elevated in synovial fluid from canine stifle joints with naturally acquired CCLR. These results indicate that there is joint inflammation and increased release of GAGs into synovial fluid, suggesting that these inflammatory changes are associated with depletion of proteoglycan from articular cartilage.

CLINICAL RELEVANCE

Medical and surgical treatments designed to decrease joint inflammation and breakdown of proteoglycans may be of value in the management of CCLR in the dog.

Direct and indirect markers of cartilage metabolism in synovial fluid obtained from dogs with hip dysplasia and correlation with clinical and radiographic variables

OBJECTIVE

To compare activities of interleukin (IL)-1beta, IL-6, tumor necrosis factor (TNF)-alpha, and matrix metalloproteinase (MMP)-3 and contents of sulfated glycosaminoglycan (S-GAG) in joint fluid obtained from dogs with hip dysplasia (HD) and clinically normal dogs, evaluate correlations among these markers in joint fluid obtained from dogs with HD, and evaluate correlations between each marker and clinical and radiographic variables. Animals-26 dogs with HD (clinical group) and 43 clinically normal Beagles (control group).

PROCEDURE

Joint fluid was aseptically collected from the hip joints of all dogs. For each dog in the clinical group, age, duration of lameness, radiographic osteoarthritis (OA) score, and Norberg angle in each affected joint were recorded. Activities of IL-1beta, IL-6, TNF-alpha, and MMP-3 and S-GAG contents were measured. Values were compared between groups by use of Mann-Whitney U tests, and the Spearman rank correlation test was used to evaluate correlations among markers and between each marker and clinical or radiographic variables.

RESULTS

Values of all markers were significantly higher for the clinical group, compared with values for the control group. There was a moderate positive correlation between lameness duration and IL-6 activity and a strong negative correlation between the Norberg angle and IL-1beta activity.

CONCLUSIONS AND CLINICAL RELEVANCE

Analysis of our results indicated that there was a significant increase in markers of OA in dogs with HD. Activities of IL-1beta and IL-6 in joint fluid of dogs with HD may be influenced by the severity of laxity in the hip joint and lameness duration, respectively.

Persistence of inflammatory cytokines cause a spectrum of chronic progressive diseases: implications for therapy

Chronic progressive disease (CPD) are the Western world's major cause of mortality (National Center for Health Statistics. Vol. 52. National vital 176 statistics reports. Deaths: final data for 2001; 2003, p. 3). Most chronic diseases present with symptoms and signs specific for the dysfunctional organ. Nonetheless, substantial commonalities are identifiable at the tissue and cellular level. These include a striking increase in inflammatory cytokines in both the tissue and the serum, accompanied by tissue destruction, apoptosis and tissue fibrosis. Individual inflammatory cytokines possess the capacity to induce these tissue effects in vitro and in vivo. Further, an elevation in systemic levels of cytokines and CRP predict an increase risk at all stages of these diseases. Therapies that inhibit the stimuli, the mediators or the responses to persistent inflammation appear to have an inhibitory effect on progression of specific diseases. We hypothesize that a unifying paradigm for CPD can be constructed based on these observations. Destabilizing stimuli activate the normal protective homeostatic inflammatory response in tissue. As the stimulus is eliminated and tissue heals, the inflammatory response recedes, re-establishing homeostasis. If inflammatory cytokines persist, however, both cell apoptosis and tissue fibrosis can be induced. Two aspects of evolution provide a potential mechanistic basis for this hypothesis. We may speculate that Darwinian selection favored early development of a system that channeled a broad spectrum of external and internal challenges through a generic response system. Thus, the mediators that respond to noxious stimuli became universal throughout organisms and species. Because these genetic responses were part of the DNA programming of all cells prior to differentiation, the tissue response to inflammation is also both uniform in nature, and narrow in scope. Subsequent cell differentiation resulted in vast differences in tissue function, so that organ dysfunction appears with the myriad symptoms and signs we recognize as individual diseases. Interference with inflammatory cytokines, e.g., with HMG Coa reductase inhibitors, inhibits a spectrum of chronic progressive diseases, independent of any LDL lowering effect.

Pharmaceutical and nutraceutical management of canine osteoarthritis: present and future perspectives

Osteoarthritis (OA) is one of the most common chronic musculoskeletal diseases and causes of lameness in the dogs. The osteoarthritic disease process involves the entire synovial joint, encompassing the synovium, cartilage and underlying bone. Joint failure results from an abnormal mechanical strain causing damage to normal tissue or failure of pathologically impaired articular cartilage and bone under the influence of normal physiological strain or a combination of both. In both cases, the end point is cartilage loss and joint impairment. Osteoarthritic chondrocytes show an altered phenotype characterised by an excess production of catabolic factors, including metalloproteinases and reactive oxygen species. These factors constitute potential therapeutic targets and some new drugs and nutraceuticals have been proposed to promote the return to homeostasis. Until now, the therapeutic management of OA in dogs has been dominated by nonsteroidal anti-inflammatory drugs, but some new compounds, including diacerhein, with potential structure-modifying effects, are already used to treat OA in humans and could be helpful to manage OA in the dog. In addition, novel nutraceuticals, such as avocado/soybean unsaponifiable substances, have shown symptomatic effects in knee OA in humans, and could offer an alternative to prevent OA progression. This paper provides an overview of recent discoveries in the pathophysiology and in the therapeutic management of osteoarthritis in dogs.

Detection of synovial macrophages in the joint capsule of dogs with naturally occurring rupture of the cranial cruciate ligament

OBJECTIVE

To test the hypotheses that the densities of macrophages in the synovial membranes and capsules of stifle joints in dogs with ruptured cranial cruciate ligaments are greater than those of normal joints and that those densities in affected joints are positively correlated with the chronicity and severity of the disease.

ANIMALS

17 dogs with naturally occurring rupture of the cranial cruciate ligament and 5 healthy control dogs.

PROCEDURE

All dogs underwent orthopedic and radiographic evaluations. In affected dogs, duration of clinical signs was used as an indicator of disease chronicity and the severity of osteoarthritis in the stifle joint was determined radiographically. Joint capsule specimens were evaluated histologically; macrophages, interleukin-6, and tumor necrosis factor-alpha were identified by use of immunocytochemical techniques.

RESULTS

Compared with unaffected joints, macrophage density was increased in all affected joints. Duration of disease was significantly associated with radiographic severity of osteoarthritis and synovial macrophage density. Synovial macrophage density was significantly associated with severity of osteoarthritis and with the presence of interleukin-6 and tumor necrosis factor-a.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that synovial macrophages may be involved in the development of pathologic changes (including osteophyte formation) in the stifle joints of dogs with osteoarthritis secondary to rupture of the cranial cruciate ligament. Determination of the importance of synovial macrophages in the development of changes in osteoarthritic joints may result in new treatment strategies that involve elimination of the deleterious effects of those cells.

Male IL-6 gene knock out mice developed more advanced osteoarthritis upon aging

OBJECTIVE

Interleukin-6 (IL-6) is expressed in osteoarthritic joints but its function in osteoarthritis (OA) is unknown. To study this, spontaneous and experimental OA were evaluated in IL-6 deficient (IL-6(-/-)) mice.

DESIGN

Histology of knees of 18-23-month-old wild type (wt) and IL-6(-/-) mice was compared for signs of OA. Cartilage proteoglycan (PG) density was measured by image analysis on safranin-O stained whole knee sections. Chondrocyte PG synthesis was measured ex vivo by (35)S-sulfate incorporation. Knee bone mineral density (BMD) was measured by dual energy x-ray absorptiometry. In young mice (3 months), OA was induced by intra-articular injection of collagenase.

RESULTS

The incidence of extensive cartilage loss at both lateral and medial sides was markedly higher in old IL-6(-/-) males, but not in females, as compared to their wt controls. Compared to age-matched wt mice, reduced ex vivo PG synthesis was found during aging in IL-6(-/-) males, without affecting their cartilage PG density. IL-6(-/-) males showed more extensive extracellular matrix deposition in the collateral ligaments and subchondral bone sclerosis, predominantly at the medial side. Total knee BMD decreased more in IL-6(-/-) (-23%) than in wt (-10%) males during aging. Collagenase-induced OA showed a similar degree of joint pathology in both strains, implying that OA susceptibility was not different at younger age.

CONCLUSIONS

Upon aging, IL-6(-/-) male mice developed more severe spontaneous OA. Reduced PG synthesis and BMD values might be indicative for an impaired repair response in IL-6(-/-) mice. This suggests a protective role for IL-6 in age-related OA in male mice.

Effects of calcitonin on subchondral trabecular bone changes and on osteoarthritic cartilage lesions after acute anterior cruciate ligament deficiency

Because SBM may contribute to cartilage breakdown in OA, experimental OA was induced in dogs by transecting the anterior cruciate ligament of the knee and treating with either CT or a placebo. CT significantly reduced both SBM and cartilage lesions. This study supports the use of CT in the treatment of canine experimental OA.

INTRODUCTION

Because subchondral bone remodeling (SBM) may contribute to cartilage breakdown in osteoarthritis (OA), we evaluated to what extend calcitonin (CT) might affect cartilage and bone changes in the early stages of canine experimental OA.

MATERIALS AND METHODS

Twelve dogs underwent transection of the anterior cruciate ligament (ACLT) of the right knee. After ACLT, each animal received a daily nasal spray delivering either 400 U of CT (CT-treated group; n = 6) or a placebo (PL-treated group; n = 6). At day 84 after surgery, animals were killed, and cartilage changes were graded. BMD and volume fraction (BVF) were assessed by pQCT in different regions of interest (ROIs) of the subchondral cancellous bone of tibial plateaus (TPs). Statistics included a 2 x 2 factorial analysis with +/-CT as one factor and +/-ACLT as the other.

RESULTS AND CONCLUSIONS

Nonoperated (N-OP) knees were normal in both groups. In the PL-treated group, ACLT knees all exhibited OA changes, which predominated in the medial knee compartment. Furthermore, compared with N-OP knees, the BMD and BVF of ACLT joints were both markedly reduced in medial TP but not in lateral TP. In contrast, in the CT-treated group, cartilage OA lesions of ACLT knees were significantly reduced, and there was no difference in BMD and BFV between N-OP and ACLT knees. These findings suggest that the loss of subchondral trabeculae contributes to cartilage breakdown, possibly by enhancing cartilage deformation on joint loading. By counteracting bone loss, CT reduced cartilage OA lesions, and thus, might be useful in the treatment of OA in cruciate-deficient dogs.

Cytokines as therapeutic targets for osteoarthritis

Osteoarthritis (OA) is a debilitating, progressive disease of diarthrodial joints associated with the aging process. With the exception of anti-inflammatory corticosteroids and nonsteroidal anti-inflammatory drugs which inhibit cyclo-oxygenase-2, the enzyme responsible for prostaglandin biosynthesis in inflammation, no specific therapy based on fundamental intracellular pathways of chondrocytes and synoviocytes exists for the medical management of OA. At the molecular level, OA is characterized by an imbalance between chondrocyte anabolism and catabolism. Disruption of chondrocyte homeostasis primarily affects the cartilage extracellular matrix (ECM), which is responsible for the biomechanical properties of the tissue. Recent evidence has implicated cytokines, among which interleukin (IL)-1, tumor necrosis factor-alpha, IL-6, and IL-17 seem most involved in the OA process of cartilage destruction. The primary role of these cytokines is to modulate the expression of matrix metalloproteinases and cartilage ECM proteins. Cartilage repair that could restore the functional integrity of the joint is also impaired because chondrocytes in OA cartilage appear unable to respond to insulin-like growth factor-1 or respond abnormally to transforming growth factor-beta. As these growth factors also modulate cytokine expression, they may prove useful in designing strategies for suppressing 'chondrocyte activation'. Although cytokines and growth factors provide a potential therapeutic target for OA, it will be necessary to elucidate the fundamental mechanisms that cytokines employ to cause chondrocyte and synoviocyte dysfunction before 'anti-cytokine' therapy can be employed in the medical management of the disease.

Pleiotrophin, an embryonic differentiation and growth factor, is expressed in osteoarthritis

OBJECTIVE

Pleiotrophin (PTN) is a 15.3 kDa heparin-binding peptide, which is expressed in mesodermal and neuroectodermal cells during development, but rarely in adult tissues. In fetal or juvenile cartilage, PTN is an abundant protein and appears to be involved in chondrocyte differentiation. Since developmentally regulated factors often re-appear in the disease state, we examined PTN expression in cartilage and synovial fluid of patients with osteoarthritis (OA).

METHODS

PTN mRNA and protein expression was assayed by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot, the protein was localized by immunohistochemistry and quantified by enzyme-linked immunoassay (ELISA).

RESULTS

PTN was undetectable in normal adult cartilage, but PTN mRNA and protein were found in OA. In cartilage from the tibial plateaus of OA patients, PTN could be immunostained in clusters of superficial chondrocytes. In the synovial fluids of OA patients, PTN concentrations were elevated in earlier OA stages, but rarely in late OA stages. Chondrosarcomas were PTN-immunonegative.

CONCLUSIONS

In addition to certain types of cancer, the embryonic growth and differentiation factor PTN is found also in adults in inflammatory diseases. In OA, PTN is especially expressed in early stages, and PTN concentrations in the synovial fluid could serve as a marker for the progress of the disease. PTN might be involved in cartilage repair in OA, in particular, in earlier stages.

Effects of anti-arthritic drugs on proteoglycan synthesis by equine cartilage

The concentration-effect relationships of phenylbutazone, indomethacin, betamethasone, pentosan polysulphate (PPS) and polysulphated glycosaminoglycan (PSGAG), on proteoglycan synthesis by equine cultured chondrocytes grown in monolayers, and articular cartilage explants were measured. The effect of PSGAG on interleukin-1beta induced suppression of proteogycan synthesis was also investigated. Proteoglycan synthesis was measured by scintillation assay of radiolabelled sulphate (35SO4) incorporation. Polysulphated glycosaminoglycan and PPS stimulated proteoglycan synthesis in chondrocyte monolayers in a concentration-related manner with maximal effects being achieved at a concentration of 10 microg/mL. Polysulphated glycosaminoglycan reversed the concentration-related suppression of proteoglycan synthesis induced by interleukin-1beta. Neither PSGAG nor PPS exerted significant effects on radiolabel incorporation in cartilage explants. Betamethasone suppressed proteoglycan synthesis by both chondrocytes and explants at high concentrations (0.1-100 microg/mL), but the effect was not concentration-related. At low concentrations (0.001-0.05 microg/mL) betamethasone neither increased nor decreased proteoglycan synthesis. Phenylbutazone and indomethacin increased radiolabel incorporation in chondrocyte cultures but not in cartilage explants at low (0.1, 1 and 10 microg/mL), but not at high (20 and 100 microg/mL) concentrations. These findings may be relevant to the clinical use of these drugs in the treatment of equine disease.

Cartilage-derived biomarkers of osteoarthritis in synovial fluid of dogs with naturally acquired rupture of the cranial cruciate ligament

OBJECTIVE

To compare synovial fluid biomarkers of cartilage metabolism in joints with naturally acquired or experimentally induced cranial cruciate ligament (CCL) rupture and determine correlations with stage and severity of disease in dogs.

ANIMALS

95 dogs with ruptured CCL, 8 dogs with experimentally ruptured CCL, and 24 healthy dogs.

PROCEDURES

Synovial fluid was assayed for chondroitin sulfate neo-epitopes 3B3(-) and 7D4 and glycosaminoglycan (GAG) concentration. Results were correlated with demographic data, duration of lameness, radiographic osteoarthritis score, and intra-articular lesions.

RESULTS

The 7D4 concentrations and 7D4:GAG in synovial fluid from joints with naturally acquired CCL rupture and experimental CCL transection were similar and significantly greater than values for healthy control joints. The 3B3(-) concentrations in the CCL-deficient groups were not significantly different, although only values in the naturally acquired CCL rupture group were significantly greater than those in the healthy control group. Within the naturally acquired CCL rupture group there was a significant correlation between 3B3(-) and 7D4 concentrations. However, there were no significant correlations between biomarker concentrations and continuous demographic or disease-related variables or differences in biomarker concentrations with different categories of disease.

CONCLUSIONS AND CLINICAL RELEVANCE

Synovial fluid biomarker concentrations were significantly increased in joints with secondary osteoarthritis associated with naturally acquired or experimental CCL rupture; however, lack of apparently simple relationships with demographic variables or stage or severity of disease limits their clinical usefulness.

Effects of carprofen (R and S enantiomers and racemate) on the production of IL-1, IL-6 and TNF-alpha by equine chondrocytes and synoviocytes

Chondrocytes and synoviocytes harvested from the joints of healthy horses were maintained in tissue culture. Production of the cytokines interleukin-1 (IL-1), interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha) in response to lipopolysaccharide (LPS), and the effects of addition of carprofen (racemate and R and S enantiomers) were determined. Lipopolysaccharide failed to stimulate TNF-alpha activity in both cell types but concentrations of IL-1 and IL-6 were both increased in a concentration and time-related manner. Both carprofen enantiomers and the racemic mixture attenuated the increase in IL-6 induced by LPS in synoviocytes, and S carprofen exerted a similar effect on chondrocytes. Neither enantiomer nor the racemate of carprofen suppressed the increase in IL-1 release produced by LPS in chondrocytes and synoviocytes. An action of carprofen to suppress IL-6 release might contribute to the actions which occur in vivo.

Effect of IL-1beta-induced macromolecular depletion on residual quadrupolar interaction in articular cartilage

PURPOSE

Sodium multiple-quantum filtered (MQF) NMR spectroscopy may potentially be used to measure proteoglycan (PG) depletion in cartilage caused by osteoarthritis (OA). The purpose of this work was to quantify the effect of interleukin-1 (IL-1beta)-induced macromolecule depletion on the residual quadrupolar interaction (RQI) of sodium in bovine cartilage plugs.

MATERIALS AND METHODS

Fifteen 8-mm-diameter cartilage plug specimens were cored from the articular surface of fresh bovine patellae. All plugs were kept in culture media and nine of the plugs were subjected to interleukin-1 (IL-1beta)-induced degeneration of cartilage for 4, 6, and 7 days. Sodium NMR spectra were obtained from each sample with a 1-cm-diameter solenoid coil in a 2T whole-body magnet interfaced to a custom-built spectrometer. We employed a previously described theoretical model to analyze triple-quantum filtered (TQF) and double-quantum filtered magic angle (DQFMA) spectra obtained from normal cartilage and cartilage treated with IL-1beta. The model assumes a static Gaussian distribution of the RQI frequency, omega(Q), in the sample. TQF and DQFMA spectra from each sample were fitted with the appropriate signal expressions to determine sigma (the root mean square (RMS) omegaQ), T2f, and T2s. An inversion-recovery sequence was used to determine T1 of each plug. A spectrophotometric assay was used to determine the amount of PG depleted from each plug. Histology was performed to visualize the PG loss in cartilage plugs. We defined sigma as the measure of changes in macroscopic order in the tissue.

RESULTS

Simulated spectra from the theoretical model were in excellent agreement with the experimental data. We were able to determine the relaxation times as well as sigma of each specimen from their corresponding fits. T2f ranged between 2.26-3.50 msec, decreasing with increased PG loss. Over the range of PG depletion investigated, T2s increased from 12.3 msec to 14.9 msec, and T1 increased from 16 msec to 21 msec, while sigma decreased from 180 Hz to 120 Hz. The order of macromolecules in the cartilage tissue decreased substantially with PG loss. Histology sections clearly showed qualitative visualization of the PG loss in cartilage following treatment with IL-1beta.

CONCLUSION

We demonstrated that IL-beta-induced macromolecule depletion in cartilage not only changes the relaxation characteristics of sodium but also changes RQI of the tissue. Using MQF sodium spectroscopy we quantified the changes in sigma and showed that loss of macromolecules reduces the degree of order in the tissue.

Echinococcus granulosus: regulation of leukocyte growth by living protoscoleces from horses, sheep, and cattle

To determine whether living hydatid tissue can, like hydatid fluid, regulate leukocyte growth, T-cell, B-cell, and macrophage lines were cocultured with protoscoleces of Echinococcus granulosus and their growth was compared with that of control cultures by thymidine uptake estimates and chemiluminescent assays of cell number. Protoscoleces supported mitosis of IL-1-deprived D10 T cells, but did not increase D10 count. The action of protoscoleces was affected by the species and organ of their origin and the length of time in culture. Unusually marked mitotic reaction, unaffected by parasite age and origin, was recorded in the B-cell line, BSM, also without commensurate count increase, indicating that induced mitosis resulted in cell loss. It is concluded that protoscoleces can induce mitosis in B and T cells of particular lineages and that this is a potential means of producing the pathological proliferation and depletion of B- and T-cell areas which characterize local reaction to hydatids.

Synovial fluid cytokines and eicosanoids as markers of joint disease in horses

OBJECTIVE

To evaluate the value of various synovial fluid cytokines and eicosanoids to diagnose joint disease or categories of joint disease.

STUDY DESIGN

Prospective acquisition of clinicopathologic data.

ANIMALS OR SAMPLE POPULATION

Client-owned or donated horses: 50 joints with no evidence of disease; 28 joints with acute disease; 32 joints with chronic disease; 9 joints with cartilage damage and no other signs of joint disease.

METHODS

Concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), prostaglandin E(2) (PGE(2)), thromboxane B(2) (TXB(2)), prostaglandin F1-alpha (PGF(1)-alpha), and leukotriene B(4) (LTB(4)), were measured in equine synovial fluid by immunoassay and categorized according to duration and degree of joint disease. Any test value for a given category that was different from normal was further analyzed for sensitivity (S), specificity (Sp), and operating point (most valid test cutoff value). Likelihood ratios and predictive values were calculated at the operating point. Mediator concentrations were correlated to synovial fluid white blood cell count. Tests were reported as poor, fair, good, or excellent based on predictive values of <.25,.25-.5,.5-.75, or >.75, respectively.

RESULTS

TNF synovial fluid concentration as a predictor of joint disease was good, and the value of TNF (maximum S and Sp) indicating joint disease was >36 pg/mL. IL-1beta as a predictor of joint disease was good, and the value of IL-1beta indicating joint disease was >4.5 pg/mL. IL-6 concentration was an excellent predictor of joint disease. Any IL-6 in synovial fluid indicated joint disease and correlated highly with synovial fluid white blood cell count (P <.0001). PGE(2) was a good-excellent predictor of disease (positive predictive value [PPV] = 0.75), and the concentration indicating joint disease was >22.5 pg/mL. The diagnostic PGF(1)-alpha concentration indicating severe chronic joint disease was identified to be >16.5 pg/mL with very high sensitivity (S = 1) and specificity (Sp =.89). PGF(1)-alpha concentrations > 9.5 pg/mL had a good PPV (.69) and NPV (.6) for any joint disease. TBX(2) concentrations below 31.5 pg/mL (S =.57; Sp =.61) were a very good predictor of joint disease (PPV =.72). LTB(4) concentration appeared to be greater in severe acute joint disease than normal joints; this was not significant (P =.15) and correlated highly with synovial fluid white blood cell count (P =.0001).

CONCLUSIONS

The ability of a single value from a joint in an adult horse predicting the presence of joint disease was often good (.5-.75), and was excellent (> or =.75) for IL-6 and PGE(2). TNF-alpha and IL-1beta were no more effective than white blood cell count in screening for joint disease. IL-6 was the most sensitive and specific for joint disease and could be an excellent screening test for the presence of joint disease when lameness is difficult to identify or is intermittent. PGE(2) would be a functional screening test for the presence of any joint disease and offers a differentiating feature because values were not influenced by white blood cell count. PGF(1)-alpha values > 16.5 pg/mL identified chronic severe joint disease and may be clinically useful when there are minimal radiographic changes but substantial articular cartilage degradation.

Potential biologic agents for treating rheumatoid arthritis

The encouraging clinical results observed in trials using anti-TNF therapy clearly warrant further studies to determine whether TNF inhibitors are capable of modifying the destructive component of this disease in long-term follow-up studies as well as to assess the safety of long-term use (see the article by Keystone in this issue). It is also reasonable to propose that interfering with the cytokine cascade earlier in the course of disease may be of even greater therapeutic benefit. As the pathogenetic mechanisms in RA are more clearly defined, especially in early disease and in those individuals destined to develop severe disease, the potential of other biologic agents to specifically inhibit these critical pathways may provide better treatments for our patients. Many potential targets in the immune-mediated process of RA are currently being rigorously evaluated in clinical trials. Use of combinations of biologic therapies, perhaps in human patients with RA, should be of considerable interest in future trials.

Concentrations of chondroitin sulfate epitopes 3B3 and 7D4 in synovial fluid after intra-articular and extracapsular reconstruction of the cranial cruciate ligament in dogs

OBJECTIVE

To evaluate effects of intra-articular and extracapsular reconstruction of the cranial cruciate ligament (CCL) on metabolism of articular cartilage as reflected by concentrations of chondroitin sulfate epitopes 3B3 and 7D4 in synovial fluid.

ANIMALS

13 adult dogs.

PROCEDURE

Each dog underwent unilateral CCL transection (CCLT). One month after CCLT, sham CCL reconstruction (3 dogs), intra-articular CCL reconstruction (5), or extracapsular CCL reconstruction (5) was performed. Synovial fluid was collected by direct arthrocentesis from CCLT and contralateral stifle joints immediately before (time 0) and 1, 3, and 5 months after CCLT. Fluid was examined for concentrations of 3B3 and 7D4 epitopes and total sulfated glycosaminoglycan (GAG) content.

RESULTS

Concentrations of 3B3, 7D4, and GAG, 3B3:GAG, or 7D4:GAG in CCLT joints did not differ significantly among treatment groups nor in the ratios of these variables in CCLT joints to contralateral joints at 3 months. In a longitudinal analysis, concentrations of 3B3 and 7D4, 3B3:GAG, and 7D4:GAG in CCLT joints in all groups changed significantly with time, but we did not detect time X group interactions.

CONCLUSIONS AND CLINICAL RELEVANCE

Transection of CCL resulted in significant perturbation in articular cartilage metabolism as reflected by alterations in concentrations of 3B3 and 7D4 in synovial fluid. These changes over time were not significantly influenced by method of CCL reconstruction. We did not find evidence that surgical stabilization of CCL-deficient joints by intra-articular or extracapsular techniques had any effect on preventing alterations in composition of synovial fluid that have been associated with secondary osteoarthritis.

Elevated interleukin-12 in pseudosynovial fluid in patients with aseptic loosening of hip prosthesis

Loosening of a prosthesis is a major problem in total joint arthroplasty. To assess levels of cytokines in patients with such loosening, we measured the pseudosynovial fluid concentration of the following cytokines; tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-1beta, IL-4, IL-6, IL-10, IL-12, matrix metalloproteinase (MMP)-1, and MMP-3. We examined the pseudosynovial fluid in patients with a loose hip prosthesis (group A; n = 8) and the synovial fluid in patients with osteoarthritis (OA) of the hip (group B; n = 18) using enzyme-linked immunosorbent assays. The mean concentration of IL-12 was significantly higher in group A than in group B (P < 0.01). Also, we found a significant (P < 0.05) correlation between the concentration of IL-12 and the concentration of MMP-1 in the patients with prosthesis loosening. The concentrations of TNF-alpha, IL-1beta, IL-4, IL-6, IL-10, IFN-gamma, MMP-1, and MMP-3 appeared to be similar in the two groups, although the small number of samples available precluded us from determining that there was no significant difference. The present study is the first to report elevated IL-12 levels in the pseudosynovial fluid of patients with a loose prosthesis. The immunoregulatory effect of IL-12 against wear particles could play an important role in causing loosening of the prosthesis.

Decline after immobilisation and recovery after remobilisation of synovial fluid IL1, TIMP, and chondroitin sulphate levels in young beagle dogs

OBJECTIVE

To monitor the concentration of markers of cartilage and synovium metabolism in the knee (stifle) joint synovial fluid of young beagles subjected to immobilisation and subsequent remobilisation.

METHODS

The right hind limb of 17 dogs was immobilised in flexion for 11 weeks. Simultaneously, the contralateral left knee was exposed to increased weight bearing. The remobilisation period lasted 50 weeks. Litter mates served as controls. The concentration in joint lavage fluid of interleukin 1alpha (IL1alpha) was measured by immunoassay, the activity of phospholipase A(2) (PLA(2)) was determined by an extraction method, chondroitin sulphate (CS) concentration by precipitation with Alcian blue, hyaluronan (HA) by an ELISA-like assay using biotinylated HA-binding complexes, matrix metalloproteinase 3 (MMP-3), and tissue inhibitor of metalloproteinases 1 (TIMP-1) by sandwich ELISA, and synovitis was scored by light microscopy.

RESULTS

Synovitis or effusion was absent in all experimental and control groups. Immobilisation decreased the joint lavage fluid levels of IL1alpha (p<0.05), TIMP (p< 0.05), and the concentration of CS down to 38% (p<0.05) in comparison with untreated litter mates with normal weight bearing. Immobilisation did not affect the activity of PLA(2), or the concentration of MMP-3 or HA in synovial fluid. Joint remobilisation restored the decreased concentrations of markers to control levels. Increased weight bearing did not change the concentrations of markers in comparison with the control joints with normal weight bearing.

CONCLUSIONS

11 weeks' joint immobilisation decreased the concentration of markers of cartilage and synovium metabolism in the synovial fluid, and remobilisation restored the concentrations to control levels. The changes in joint metabolism induced by immobilisation, as reflected by the markers, are thus different from those found in osteoarthritis, where increased levels of these markers are associated with enhanced degradation and synthesis. These findings suggest that the change induced in joint metabolism by immobilisation is reversible in its early stages.

Growth kinetics of leukocyte cell lines cultured with hydatid fluid of Echinococcus granulosus equinus

Oxidation of 3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and tritiated thymidine uptake were used to measure, respectively, the viable cell count and the S-phase activity of D10, B9, A20 and p388d leukocytic cell lines cultured in the presence of varying concentrations of fluid from fertile and infertile hydatid cysts of Echinococcus granulosus equinus. Exposure to hydatid fluid raised or lowered the entry of D10 cells into S-phase depending on the concentration of the fluid and of the supporting cytokines. Enlargement of the S-phase population was unaccompanied by increase in viable count indicating that the mitotic cycles induced by hydatid products were not completed. A similar conclusion was reached in respect of the p388d monocytic line, and both changes appear consistent with those occurring in histopathology in vivo. By contrast, the main effect on B9 and A20 B cells was inhibition of entry into S-phase.

Echinococcus granulosus: assays for hydatid immunoregulatory factors using established lymphoid cell lines

Mitosis, mitochondrial metabolic rate and proliferation were measured in established lymphoid cell lines exposed to chromatographic fractions of equine Echinococcus granulosus hydatid fluid. In several cell lines, one or more of the three parameters were modified by the exposure. As an assay for potential immunoregulatory activity, the method was simple and repeatable. The following novel observations were made: (1) Mitotic reaction was found among lines of T-cell, B-cell and macrophage origin; (2) mitosis was accompanied by proliferation in the B-cell lines, B9 and A20, and in the macrophage lines, HL-60 and P388d. With mitotically responsive T-cells, proliferation was slight in CTLL-2 and absent in D10, implying cell-cycle modification; (3) mitotic responsiveness tended to occur in cell lines with mature characteristics; (4) among cytokine-dependent cell lines, hydatid fluid FPLC fraction 1 mimicked IL-1 and several fractions mimicked IL-2 and IL-6 in the maintenance of mitosis; and (5) there was significant statistical interaction between the influences of mammalian cytokines and hydatid fluid fractions, implying that the propensity of antigenically unprimed lymphoid cells to be regulated by E. granulosus is conditioned by cytokine activity.

Immunological and inflammatory characterisation of three canine cell lines: K1, K6 and DH82

Three canine cell lines, K1, K6 and DH82, derived from canine malignant neoplasms, were characterised. They were examined for expression of surface antigens, cytokines, neuropeptide receptors, matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). The growth characteristics of the cell lines were established and bioassays used to detect production of TNF-alpha, IL-1 and IL-6. In the DH82 cell line, production of TNF-alpha and IL-6 was readily detected. Neither K1 or K6 cell lines produced any measurable amounts of TNF-alpha, IL-1 or IL-6. At a molecular level, using reverse transcription-polymerase chain reaction (RT-PCR) to detect specific mRNA, the DH82 cell line expressed TNF-alpha, IL-1 and IL-6, whereas the K1 and K6 cell lines expressed TNF-alpha. Canine IL-5, IL-8 and IL-10 mRNA were detected in the DH82 cell line but only IL-5 and IL-8 mRNA were detected in the K1 and K6 cell lines. Gelatin zymography was used for the detection of MMP-2 and MMP-9 and all three cell lines produced MMP-2 but only the DH82 cell line produced MMP-9. Reverse zymography was used to detect TIMP-1 and TIMP-2 and all three cell lines produced both proteins. The presence of these MMPs and TIMPs was confirmed at a molecular level using RT-PCR. Canine MMP-14 mRNA was detected in all three cell lines. For this investigation several genes for canine inflammatory molecules were cloned and sequenced for molecular detection; these included IL-1, IL-6, IL-8, TNF-alpha, MMP-9, MMP-14, TIMP-1, TIMP-2 and beta-actin. Of all the cell surface antigens tested, only CD14 was expressed on the DH82 cell line although CD5 and CD45 was partially expressed. The K1 and K6 cell lines were negative for all of the CD markers tested. K1 and K6 were negative for Neurokinin 1 receptor (NK1-R) but positive for Calcitonin gene related peptide receptor type 1 (CGRP-1R) and Calcitonin gene related peptide receptor component protein (CGRP-RCP). The DH82 cell line expressed neither NK1-R or CGRP-1R; however, it did express CGRP-RCP. Generally the DH82 cell line exhibited considerable similarity to canine monocytes, but all three cell lines will be useful as standards and for the purification of various immunological and inflammatory mediators in the dog.

The role of cytokines as inflammatory mediators in osteoarthritis: lessons from animal models

Studies in animal models of osteoarthritis (OA) have been used extensively to gain insight into the pathogenesis of OA, but early studies largely ignored inflammation except as a secondary phenomenon. Synovitis has often been noted as a feature in experimental OA, and more recent work has established a central role for inflammatory cytokines as biochemical signals which stimulate chondrocytes to release cartilage-degrading proteinases. Thus, proteinase inhibitors, cytokine antagonists and receptor blocking antibodies, and growth/differentiation factors have been considered as potential therapeutic agents and targets for gene therapy. Although there is some disagreement, it is generally accepted that IL-1 is the pivotal cytokine at early and late stages, while TNF-alpha is involved primarily in the onset of arthritis. Other cytokines released during the inflammatory process in the OA joint may be regulatory (IL-6, IL-8) or inhibitory (IL-4, IL-10, IL-13, IFN-gamma). Furthermore, studies in animal models have illustrated the potentially beneficial effects of anticytokine therapy with monoclonal antibodies or receptor antagonists, although local rather than systemic delivery would be necessary for the largely localized OA in humans. Transgenic or knockout mice have also provided insights into general mechanisms of cytokine-induced cartilage degradation but have not directly addressed OA pathogenesis. Similarly, animals with spontaneous or transgenic modifications in cartilage matrix components, growth/differentiation factors, or developmentally regulated transcription factors have provided information about potential gene defects that predispose to OA without addressing the role of inflammatory mediators in cartilage destruction. Although the multiple etiologies of human OA indicate that it is more complex than any animal model, the use of appropriate, well-defined animal models will establish the feasibility of novel forms of therapy.

Canine rheumatoid arthritis and inflammatory cytokines

Bioassays were developed to detect canine pro-inflammatory cytokines. These enabled characterisation of these cytokines and their isoforms and provided means for their assay in the joints of dogs with different naturally occurring arthropathies. Canine IL-1 was detected by its induction of proliferation of D10(N4)M cell line, whilst IL-6 had a proliferative effect on B9 cell line. TNFalpha had a cytotoxic effect on WEHI 164 (13) cells. Partial purification of the cytokines was achieved by FPLC ion-exchange chromatography and two isoforms of IL-1 were shown, possibly corresponding to IL-1alpha and IL-1beta. TNFalpha only appeared as one isoform whereas IL-6 showed at least five isoforms, possibly corresponding to the other molecules in the IL-6 family, such as IL-11 and oncostatin M. Analysis of synovial fluids from dogs with osteoarthritis (OA) and rheumatoid arthritis (RA) showed that IL-1 and TNFalpha bioactivity was not readily detectable at increased levels in diseased joints but that IL-6 was significantly increased in both diseases. It is now important to determine the role of IL-6 in OA and RA in the dog, particularly in the induction of proteolytic enzymes which lead to cartilage loss.