Elevated angiogenin levels in synovial fluid from patients with inflammatory arthritis and secretion of angiogenin by cultured synovial fibroblasts

Angiogenesis is a key process in the pathogenesis of inflammatory arthritis. Angiogenin is one of the most potent inducers of neovascularization in experimental models in vivo. To look for evidence that angiogenin is involved in inflammatory joint disease, we examined plasma and synovial fluid (SF) samples from rheumatology patients and synovial fibroblast cell culture supernatants. Angiogenin levels were determined by radioimmunoassay and ELISA. Plasma angiogenin concentrations ranged from 96 to 478 ng/ml, with no significant difference between patients and normal controls. In SF, angiogenin concentrations were significantly higher in patients with acute or chronic synovitis (rheumatoid arthritis (RA): median, 104 ng/ml; range 13-748, n = 14; crystal-induced arthritis (CIA): median, 149 ng/ml; range, 37-616, n = 14, and other chronic inflammatory arthritis: median, 42 ng/ml; range, 15-205; n = 9) than in the 18 patients with osteoarthritis (OA) (median, 20 ng/ml; range 8-116) (P < 0.0001, anova). Angiogenin levels in SF from RA patients in remission with secondary OA were similar to those achieved in primary OA, and decreased in parallel with the resolution of acute gout. Angiogenin protein was released by cultured synovial fibroblasts from OA and RA patients, and reached 1.18 ng/106 cells/day. These data suggest that angiogenin may mediate local inflammation in arthritis via effects on angiogenesis and leucocyte regulation.     

Thioredoxin as a biomarker for oxidative stress in patients with rheumatoid arthritis

There is no doubt that oxidative stress occurs in patients with rheumatoid arthritis (RA) and play an important role in both inflammation and destruction of RA joints. Thioredoxin (TRX) is a ubiquitous redox-active protein and is known to be induced in several cells against oxidative stress and to be secreted extracellularly. To clarify whether plasma thioredoxin levels could be a marker for oxidative stress in patients with RA, we measured plasma TRX levels in patients with RA using a sensitive sandwich enzyme-linked immunosorbent assay (ELISA) and investigated its relationship to TRX concentrations in the inflammatory joints.We have found that the plasma TRX levels of RA patients were significantly higher than those of normal subjects (86.8 +/-54.1 ng/ml versus 38.6 +/-18.5 ng/ml, P<0.0001). The plasma levels were correlated with the disease activity of RA and also with serum C-reactive protein (CRP) values (P<0.01). The concentration of TRX in synovial fluid (SF) from RA was 353.3 +/- 220.1 ng/ml (mean +/- S.D.) which was significantly higher than that in SF from osteoarthritis patients (70.6 +/- 31.0 ng/ml, P<0.0001). The SF TRX concentration was significantly correlated with the number of leukocytes infiltrating in SF and with the serum CRP levels. The serum TRX levels were significantly positively correlated with the SF TRX concentrations in RA patients (P<0.05). By the histological examination for synovial tissue of RA patients, TRX was shown to be present on the surface of synovial lining layer as well as in the leukocytes.Moreover, urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative DNA damage by endogenously generated oxygen radicals, was significantly higher in RA patients than in healthy subjects (11.55 +/- 4.71 versus 7.76 +/- 2.26 ng/mg creatinine, P<0.0001). Plasma TRX levels were significantly correlated with urinary excretion of 8-OHdG (P<0.005). We concluded that plasma TRX level is a new biomarker for the disease activity of RA and may reflect higher levels of oxidative stress in RA patients.     

The levels of soluble granzyme A and B are elevated in plasma and synovial fluid of patients with rheumatoid arthritis (RA).

Cytotoxic cells possess specialized granules which contain perforin and a group of serine proteinases termed granzymes. Granzyme-positive cells have been identified in synovial fluid and tissue of patients with RA, where they may play an important role as mediators of granule-mediated apoptosis, extracellular proteolysis, and cytokine induction. The aim here was to define further the involvement of cytotoxic cells in RA. Plasma and synovial fluid samples from the knee joint were obtained from 31 RA patients. The disease controls included 20 osteoarthritis (OA) patients and 10 reactive arthritis (ReA) patients. A recently developed capture ELISA was used to detect soluble granzymes A and B in all patients. Compared with OA and ReA disease controls, markedly increased levels of soluble granzymes A and B were detected in both plasma and synovial fluid of RA patients (P < 0.00001). When values for soluble granzymes A and B in plasma and synovial fluid were used simultaneously as independent variables, logistic regression analysis indicated that a diagnosis of RA could be predicted correctly in 84% of the RA patients and a diagnosis of non-RA in 90% of the controls. The markedly elevated levels of soluble granzymes A and B in plasma and synovial fluid of RA patients strongly suggest that cytotoxic cells are active participants in the pathogenesis of RA. Moreover, the results suggest that measurement of granzymes may assist the laboratory evaluation of patients with arthritis. Larger studies in patients with early disease may clarify the role of this test system in differential diagnosis.     

Distribution of interleukin‐10 family cytokines in serum and synovial fluid of patients with inflammatory arthritis reveals different contribution to systemic and joint inflammation

Evidence exists that interleukin (IL)‐10 family cytokines may be involved in the pathogenesis of rheumatoid arthritis (RA). We sought to determine whether or not these cytokines are involved in psoriatic arthritis (PsA). We conducted a prospective study on patients with PsA, RA and osteoarthritis (OA); healthy controls (HC) were also included. We analysed IL‐20, IL‐24 and IL‐19 serum and synovial fluid (SF) levels and change of serum levels following treatment with biological agents. IL‐20 serum levels were increased in PsA and RA compared with OA patients and HC and with matched SF levels. IL‐24 serum levels in PsA, RA and OA patients were higher than those in HC and also with respect to matched SF in PsA. IL‐19 serum levels were higher in HC and OA compared with PsA and RA patients; IL‐19 SF levels were higher in PsA and RA compared with OA patients, and in PsA compared with RA patients. PsA and RA patients showed a reduction of IL‐19 serum levels after biological treatment. Therefore, IL‐19 seems to be involved mainly in the joint inflammation, whereas IL‐20 and IL‐24 appear to participate mainly in the systemic responses. These findings may further the comprehension of the contribution of these cytokines to the inflammatory response involved in chronic arthritis, as well as to the development of novel therapeutic strategies.     

Excitatory amino acids, TNF-alpha, and chemokine levels in synovial fluids of patients with active arthropathies

The aim of this study was to assess the synovial fluid (SF) neurotransmitter excitatory amino acid (EAA) levels, including glutamate (Glu) and aspartate (Asp), in the context of SF levels of other amino acids, TNF-alpha and chemokines from patients with active arthropathies. The SF was collected from patients with active rheumatoid arthritis (RA), gout, or osteoarthritis (OA). The SF samples were analysed for levels of neurotransmitters glutamate and aspartate, tumour necrosis factor-alpha (TNF-alpha), Regulated upon Activation Normally T-cell Expressed and Secreted (RANTES), macrophage inhibitory factor-1 alpha (MIP-1alpha) and interleukin 8 (IL-8). SF WBC counts were also determined. Correlations between SF EAA, TNF-alpha and chemokines were determined by the Pearson product-moment correlation. Primary cultures derived from SF from active RA and gout patients were incubated with added l-glutamate, to assess if exposure to Glu could increase TNF-alpha levels. There were significant elevations in SF EAA, SF TNF-alpha and SF RANTES in RA patients compared to gout or OA patients. Significant correlations between SF EAA and SF RANTES, MIP-1alpha and IL-8 levels were seen, and SF EAA and SF TNF-alpha or SF WBC levels approached significance. Addition of exogenous neurotransmitter glutamate significantly increased TNF-alpha levels in primary cell cultures derived from RA and gout patients. The SF neurotransmitter EAA levels significantly correlated to selected SF chemokine levels, in clinically active RA, gout and OA patients, independent of disease. Added Glu resulted in significantly increased TNF-alpha levels in primary synovial cell cultures. These data expand the relationship of SF neurotransmitter EAA levels to SF cytokines and chemokines in patients with clinically active arthritis, and suggest that neurotransmitters Glu and Asp contribute to peripheral inflammatory processes.     

Immunoglobulin G and A antibody responses to Bacteroides forsythus and Prevotella intermedia in sera and synovial fluids of arthritis patients

The objective of the present study was to investigate immunoglobulin G (IgG) and IgA antibody immune responses to Porphyromonas gingivalis, Prevotella intermedia, Bacteroides forsythus, and Candida albicans in the sera of patients with rheumatoid arthritis (RA), the synovial fluid (SF) of patients with RA (RA-SF samples), and the SF of patients without RA (non-RA-SF samples). An enzyme-linked immunosorbent assay was used to determine IgG and IgA antibody levels in 116 serum samples from patients with RA, 52 RA-SF samples, and 43 non-RA-SF samples; and these were compared with those in SF samples from 9 patients with osteoarthritis (OA-SF samples) and the blood from 100 donors (the control [CTR] group). Higher levels of IgG antibodies against B. forsythus (P < 0.0001) and P. intermedia (P < 0.0001) were found in non-RA-SF samples than in OA-SF samples, and higher levels of IgG antibodies against B. forsythus (P = 0.003) and P. intermedia (P = 0.024) were found in RA-SF samples than in OA-SF samples. Significantly higher levels of IgA antibodies against B. forsythus were demonstrated in both RA-SF and non-RA-SF samples than in OA-SF samples. When corrected for total Ig levels, levels of IgG antibody against B. forsythus were elevated in RA-SF and non-RA-SF samples compared to those in OA-SF samples. Lower levels of Ig antibodies against B. forsythus were found in the sera of patients with RA than in the plasma of the CTR group for both IgG (P = 0.003) and IgA (P < 0.0001). When corrected for total Ig levels, the levels of IgG and IgA antibodies against B. forsythus were still found to be lower in the sera from patients with RA than in the plasma of the CTR group (P < 0.0001). The levels of antibodies against P. gingivalis and C. albicans in the sera and SF of RA and non-RA patients were comparable to those found in the respective controls. The levels of IgG and IgA antibodies against B. forsythus were elevated in SF from patients with RA and non-RA-SF samples compared to those in OA-SF samples. Significantly lower levels of IgG and IgA antibodies against B. forsythus were found in the sera of patients with RA than in the plasma of the CTR group. This indicates the presence of an active antibody response in synovial tissue and illustrates a potential connection between periodontal and joint diseases.     

Soluble CD4 in patients with rheumatoid arthritis and osteoarthritis

An ELISA was used to measure the soluble form of the leukocyte surface antigen CD4 (sCD4) in the sera and synovial fluids (SF) of patients with rheumatic diseases. Patients with rheumatoid arthritis (RA) had raised levels of sCD4 in both their sera and synovial fluid compared to age-matched healthy controls. In patients with osteoarthritis levels of sCD4 in SF and sera were lower than in RA but higher than in sera of healthy individuals. Mononuclear cells from the synovial fluid of RA patients were found to produce spontaneously high levels of sCD4, but autologous blood cells only produced comparable levels after in vitro stimulation with mitogenic lectin. In individual RA patients with active disease, serial sCD4 levels fell preceding clinical improvement. In three patients where serum sCD4 levels fell and clinical improvement occurred, subsequent small increases in serum sCD4 preceded increased clinical disease activity by up to 5 days. Synovial fluid levels of sCD4 correlated positively with soluble interleukin 2 receptor levels but no correlation was found with sCD8 levels. We conclude that the release of sCD4 reflects the involvement of T helper cells and macrophages in the pathogenesis of joint inflammation, especially in RA.     

Levels of the soluble forms of CD80, CD86, and CD83 are elevated in the synovial fluid of rheumatoid arthritis patients

The release of soluble forms of CD80 (sCD80), CD86 (sCD86), and CD83 (sCD83) provide a potentially powerful immunoregulatory mechanism. We therefore investigated the potential presence and relative levels of these molecules in the synovial fluid (SF) and serum of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Serum and SF levels were measured by enzyme-linked immunosorbent assay. Serum levels of sCD80, sCD86, and sCD83 in RA and OA patients were similar to those present in normal donor serum (NDS) and the SF of OA patients. In contrast, when compared with NDS and OA SF levels, almost all RA SF samples had elevated sCD83 levels (32/35, >0.63 ng/ml) and a substantial proportion had elevated sCD80 (13/29, >0.22 ng/ml) or sCD86 (16/33, >2.31 ng/ml) levels. Analysis of matched pairs of serum and SF from RA patients demonstrated that the SF/serum ratio for sCD80 (95% CI = 1.7-3), sCD86 (95% CI = 1.5-3.1), and sCD83 (95% CI = 3.6-7.8) levels was >1 in almost all patients. In conclusion, this study shows that the SF from almost all RA patients contain elevated levels of sCD83 and the majority of these samples also contain elevated levels of sCD80 and/or sCD86. These molecules may play a role in modulating immune responses within the rheumatoid joint.     

Soluble Forms of P-Selectin and Intercellular Adhesion Molecule-3 in Synovial Fluids

A number of adhesion molecules have been identified in synovial tissues of patients with rheumatoid arthritis (RA). Some of them are upregulated and may play an important role in the inflammatory processes of the diseased joint. In addition to synovial tissue cell surface expression, synovial fluids contain soluble forms of many adhesion molecules, such as intercellular adhesion molecule-1, E-selectin (sE-selectin), and L-selectin. In this study, we investigated the expression of soluble P-selectin (sP-selectin) and intercellular adhesion molecule-3 (sICAM-3) in synovial fluids from patients with RA, osteoarthritis (OA), and other forms of arthritis. sP-selectin and sICAM-3 levels in RA synovial fluids were significantly increased compared to those in OA. The levels of sP-selectin in synovial fluids correlated with sICAM-3 and sE-selectin in synovial fluids. The levels of sICAM-3 in synovial fluids correlated with synovial fluid leukocyte counts and erythrocyte sedimentation rate.In vitro,synovial fluid mononuclear cells produced sICAM-3 spontaneously. Elevated levels of sP-selectin and sICAM-3 in RA synovial fluids compared to OA may indicate inflammatory interactions between endothelial cells, leukocytes, and other synovial cells in the diseased joint.     

Telomerase activity in the synovial tissues of chronic inflammatory and non-inflammatory rheumatic diseases.

Telomerase is a ribonucleoprotein complex which can compensate for telomeric loss originating from each cell division, and its activation plays a critical role in cellular immortality. We previously found that telomerase is activated not only in immortal cancer cells but also in activated lymphocytes. To assess the diagnostic significance of telomerase activity in RA synovial tissues, we quantitatively examined telomerase activity in synovial tissue samples obtained from 47 patients with RA, 31 with osteoarthritis (OA), and 23 with other joint diseases. Telomerase activity in synovial tissues was detected in 28 of 47 (59.6%) patients with RA, including monoarticular-type RA, but in none of those with other joint diseases except one case each of synovial chondromatosis and OA. Thus, the specificity of telomerase activity in synovial tissues for RA among joint diseases was 96.3% (52/54). In RA samples, the telomerase activity was detected in 14 of 27 (51. 9%) patients with total joint replacement, 7 of 12 (58.3%) open synovectomy cases, and 7 of 8 (87.5%) arthroscopic synovectomy cases. Detection of telomerase activity in synovial tissues is considered to be useful for diagnosis of RA, including monoarticular-type RA, or active inflammation with lymphocyte infiltration, and arthroscopy can be applied for this purpose.     

The clinical significance of cytoplasmic inclusions(CPI) in synovial fluid examination.

The clinical significance of cytoplasmic inclusions(CPI) in synovial fluid(SF) examination was evaluated. We examined SF specimens collected from major rheumatology clinics in the Philadelphia area during the period of January to December 1995. Among 759 patients in the initial study group, 419 cases with established diagnoses and full synovial analyses were included. Their diagnoses and SF analysis results including leukocyte counts, differential counts and wet preparations were collected and analysed. Ninety seven of the 419 SF specimens were found to have CPI. CPI were found in SF from almost all rheumatic diseases. They were most likely to be found in inflammatory arthropathy including rheumatoid arthritis(RA, 46%), juvenile rheumatoid arthritis(JRA, 78%) and psoriatic arthritis(55%). On the contrary, CPI were least common in crystal-induced arthropathy among the inflammatory arthropathy. CPI were found 8 out of 98 gout cases(8%) and 2 among 53 calcium pyrophosphate dihydrate(CPPD) deposition disease(4%). In noninflammatory arthropathy, CPI were found in only 6 cases(6%) out of the 103 osteoarthritis(OA). In RA cases with non-inflammatory SF, 4 of the 20 SF(20%) had CPI while only 6% of OA SF had CPI. OA SF with CPI were all noninflammatory SF. In summary, CPI were a common finding on SF examination. CPI were more likely to be found in inflammatory arthropathy than noninflammatory. Among inflammatory arthropathy, CPI can favor non-crystal arthropathy than crystal arthropathy. Awareness of the presence of CPI is suggested as an addendum to routine SF analysis. Renewed investigation of the several types of CPI may add further to the understanding of joint disease.     

类风湿关节炎患者血清和关节液细胞因子水平的变化及临床意义

目的探讨幼年类风湿关节炎(JRA)及类风湿关节炎(RA)患者IL-6、IL-8、sIL-2R和TNF-α等细胞因子(CK)水平的变化,及其与风湿活动的传统指标血沉(ESR)和C-反应蛋白(CRP)的相关性。方法采用夹心ELISA法,对30例JRA和34例RA患者的血清中,4例JRA、7例RA、6例骨性关节炎(OA)和9例半月板损伤(MT)患者的关节液中IL-6、IL-8、sIL-2R和TNF-α的水平进行检测。结果①30例JRA、34例RA患者血清IL-6和sIL-2R的水平与对照组相差非常显著(P〈0.01);30例JRA患者血清IL-8水平与对照组比较相差显著(P〈0.05)。②JRA全身型、少关节型患者血清IL-8、sIL-2R的水平和JRA多关节型患者血清IL-6的水平与对照组相差非常显著(P〈0.01)。③4例JRA及7例RA患者关节液sIL-2R的水平和RA患者关节液的IL-6水平与对照组相差显著(P〈0.05)。④JRA患者血清IL-6和sIL-2R的水平与ESR和CRP的变化呈明显的相关关系(r值分别为0.532和0.621)。结论①IL-6、sIL-2R的水平与JRA、RA病的活动性有关,是类风湿活动性的主要指标。②sIL-2R不仅参与JRA和RA的全身病理损伤,而且是引起关节局部损伤的主要CK,IL-6也参与JRA关节局部的病理损伤,在RA关节局部损伤似乎更为重要。③IL-8主要参与JRA的全身病理损伤,对关节局部病理损伤似乎并不重要。     

Synovial fluid macrophages are capable of osteoclast formation and resorption

To determine whether synovial fluid (SF) macrophages isolated from the SF of osteoarthritis (OA), rheumatoid arthritis (RA) and pyrophosphate arthropathy (PPA) joints are capable of osteoclast formation, and to investigate the cellular and humoral factors required for this to occur, SF macrophages (CD14+) were isolated from the knee joint SF from patients with OA, RA and PPA and cultured for up to 14 days with macrophage-colony stimulating factor (M-CSF) and soluble receptor activator for nuclear factor-kappaB ligand (RANKL) or tumour-necrosis factor-alpha (TNFalpha) and interleukin-1alpha (IL-1alpha). Osteoclast differentiation was assessed by expression of tartrate-resistant acid phosphatase (TRAP) and vitronectin receptor (VNR), F-actin ring formation and lacunar resorption. Osteoclast formation and lacunar resorption was seen in RANKL-treated cultures of SF macrophages isolated from OA, RA and PPA joints with the largest amount of resorption noted in RA and PPA SF macrophage cultures. In TNFalpha/IL-1alpha-treated RA and PPA SF macrophage cultures, osteoclasts capable of lacunar resorption were also formed. Lacunar resorption was more extensive in RANKL than TNFalpha/IL-1alpha-treated cultures. These findings indicate that SF macrophages are capable of differentiating into mature osteoclasts capable of lacunar resorption. M-CSF in combination with RANKL or TNFalpha/IL-1alpha was required for osteoclast formation. As inflammatory synovial fluids contain an increase in the number of macrophages and an increase in the amounts of RANKL, TNFalpha and IL-1alpha, these findings suggest that one means whereby bone erosions may form in rheumatoid or crystal arthritis is by differentiation of synovial fluid macrophages into osteoclasts.     

IL-22在类风湿关节炎中的表达及临床意义

目的：探讨RA患者IL-22的表达水平并分析其临床意义。方法：流式细胞术检测RA患者（50例）、OA患者（15例）、健康对照组（15例）外周血及RA关节滑液Th22细胞所占比例,ELISA法检测血清及RA关节滑液中IL-22水平。检测RA患者疾病活动性、临床指标、骨破坏情况,分析其与IL-22水平相关性。两组间比较用t检验,相关性分析采用Pearson直线相关分析法,多组样本比较用Kruskal-Wallis H检验。结果：RA患者外周血中Th22细胞比例高于OA组（t=2.290,P=0.021）及健康对照组（t=2.524,P=0.015）;RA患者血清IL-22水平高于OA患者（t=2.560,P=0.014）及健康对照组（t=2.768,P=0.009）。RF阳性RA血清IL-22水平高于RF阴性RA（t=2.322,P=0.035）。抗CCP抗体阳性RA血清IL-22水平高于抗CCP抗体阴性RA（t=2.504,P=0.015）。RA血清IL-22水平与ESR、RF、DAS28评分呈正相关关系（r分别为0.312、0.314、0.332,P<0.05）。RA患者血清IL-22水平随骨侵蚀的加重呈递增趋势,X线不同分期之间差异有统计学意义（H=9.14, χ²_0.05（3）=7.81,H>χ²_0.05(3),P<0.05)。有关节积液RA患者血清IL-22水平高于无关节积液RA患者（t=2.587,P=0.012）,关节滑液IL-22水平高于血清（t=2.668,P=0.011）,与关节滑液Th22细胞比例无相关性（r=0.287,P=0.065）。结论：RA患者血清及关节滑液IL-22水平增高,与疾病活动性及骨破坏相关,可成为病情评估与骨破坏的指标。IL-22可能为RA治疗的新靶点。     

CCL25 and CCR9 is a unique pathway that potentiates pannus formation by remodeling RA macrophages into mature osteoclasts

This study elucidates the mechanism of CCL25 and CCR9 in rheumatoid arthritis (RA). RA synovial fluid (SF) expresses elevated levels of CCL25 compared to OA SF and plasma from RA and normal. CCL25 was released into RA SF by fibroblasts (FLS) and macrophages (MΦs) stimulated with IL-1β and IL-6. CCR9 is also presented on IL-1β and IL-6 activated RA FLS and differentiated MΦs. Conversely, in RA PBMCs neither CCL25 nor CCR9 are impacted by 3-month longitudinal TNF inhibitor therapy. CCL25 amplifies RA FLS and monocyte infiltration via p38 and ERK phosphorylation. CCL25-stimulated RA FLS secrete potentiated levels of IL-8 which is disrupted by p38 and ERK inhibitors. CCL25 polarizes RA monocytes into nontraditional M1 MΦs that produce IL-8 and CCL2. Activation of p38 and ERK cascades are also responsible for the CCL25-induced M1 MΦ development. Unexpectedly, CCL25 was unable to polarize RA PBMCs into effector Th1/Th17 cells. Consistently, lymphokine like RANKL was uninvolved in CCL25-induced osteoclastogenesis; however, this manifestation was regulated by osteoclastic factors such as RANK, cathepsin K (CTSK), and TNF-α. In short, we reveal that CCL25/CCR9 manipulates RA FLS and MΦ migration and inflammatory phenotype in addition to osteoclast formation via p38 and ERK activation.     

Iron(III)-mediated intra-articular crystal deposition in arthritis: a therapeutic role for iron chelators.

Crystal deposition in arthritic diseases has attracted much interest. Many reports have established the presence of calcium pyrophosphate (CPPD), hydroxyapatite (HAP) and urate crystals throughout the range of arthritic diseases. In particular, HAP crystals have been detected in 30-60% of synovial fluid (SF) samples from patients suffering from osteoarthritis (OA) and 33% of those suffering from rheumatoid arthritis (RA). In OA, crystal deposition has been linked to greater joint deterioration. The mechanism of intra-articular calcification is unknown. Nucleation is required to transform a 'metastable' phosphate- and calcium-rich biofluid into one that generates crystals. Ferric ions have been demonstrated to induce crystallization of these stable supersaturated solutions via the process of nucleation.The inflamed arthritic joint is prone to iron loading. Microbleeding from compromised vasculature contributes to intra-articular iron loading in arthritic conditions. Low-molecular-mass redox-active iron complexes have been detected in SF in inflammatory joint diseases. These species are credited with mediating oxidative stress via interaction with peroxides and superoxide. In addition, adventitious low-molecular-mass iron complexes can cause nucleation leading to crystal growth within the joint.Decorporating agents capable of removing this misplaced iron from the arthritic joint would have the joint benefit of relieving oxidative stress and preventing crystal nucleation. Systemic side effects could be overcome by the targeting suitable chelators using bioreductive delivery systems that are activated in hypoxic inflamed synovial tissue.