Increased knee joint loads during walking are present in subjects with knee osteoarthritis.

OBJECTIVE: This study tests the hypothesis that the peak external knee adduction moment during gait is increased in a group of ambulatory subjects with knee osteoarthritis (OA) of varying radiographic severity who are being managed with medical therapy. Tibiofemoral knee OA more commonly affects the medial compartment. The external knee adduction moment can be used to assess the load distribution between the medial and lateral compartments of the knee joint. Additionally, this study tests if changes in the knee angles, such as a reduced midstance knee flexion angle, or reduced sagittal plane moments previously identified by others as load reducing mechanisms are present in this OA group. DESIGN: Thirty-one subjects with radiographic evidence of knee OA and medial compartment cartilage damage were gait tested after a 2-week drug washout period. Thirty-one normal subjects (asymptomatic control subjects) with a comparable age, weight and height distribution were also tested. Significant differences in the sagittal plane knee motion and peak external moments between the normal and knee OA groups were identified using t tests. RESULTS: Subjects with knee OA walked with a greater than normal peak external knee adduction moment (P=0.003). The midstance knee flexion angle was not significantly different between the two groups (P=0.625) nor were the peak flexion and extension moments (P> 0.037). CONCLUSIONS: Load reducing mechanisms, such as a decreased midstance knee flexion angle, identified by others in subjects with endstage knee OA or reduced external flexion or extension moments were not present in this group of subjects with knee OA who were being managed by conservative treatment. The finding of a significantly greater than normal external knee adduction moment in the knee OA group lends support to the hypothesis that an increased knee adduction moment during gait is associated with knee OA.

The knee adduction moment during gait in subjects with knee osteoarthritis is more closely correlated with static alignment than radiographic disease severity, toe out angle and pain.

This study tested whether the peak external knee adduction moments during walking in subjects with knee osteoarthritis (OA) were correlated with the mechanical axis of the leg, radiographic measures of OA severity, toe out angle or clinical assessments of pain, stiffness or function. Gait analysis was performed on 62 subjects with knee OA and 49 asymptomatic control subjects (normal subjects). The subjects with OA walked with a greater than normal peak adduction moment during early stance (p = 0.027). In the OA group, the mechanical axis was the best single predictor of the peak adduction moment during both early and late stance (R = 0.74, p < 0.001). The radiographic measures of OA severity in the medial compartment were also predictive of both peak adduction moments (R = 0.43 to 0.48, p < 0.001) along with the sum of the WOMAC subscales (R = -0.33 to -0.31, p < 0.017). The toe out angle was predictive of the peak adduction moment only during late stance (R = -0.45, p < 0.001). Once mechanical axis was accounted for, other factors only increased the ability to predict the peak knee adduction moments by 10 18%. While the mechanical axis was indicative of the peak adduction moments, it only accounted for about 50% of its variation, emphasizing the need for a dynamic evaluation of the knee joint loading environment. Understanding which clinical measures of OA are most closely associated with the dynamic knee joint loads may ultimately result in a better understanding of the disease process and the development of therapeutic interventions.

Old and new drugs used in rheumatoid arthritis: a historical perspective. Part 2: the newer drugs and drug strategies.

After a 20-year hiatus, drug development for rheumatoid arthritis resumed in the early 1980s with cyclosporine, continuing in the 1990s with minocycline, leflunomide, and the tumor necrosis factor-alpha antagonists, infliximab and etanercept. Unlike the older disease-modifying antirheumatic drugs (apart from the cytotoxics), the newer drugs were designed with strict reference to proven pathophysiology in rheumatoid arthritis and, apart from minocycline, the intended action of these agents is highly likely the explanation for the observed efficacy. The evidence for the evolution of more rational drug development in rheumatoid arthritis has not altered the fact that efficacy versus toxicity still remains the major determinant in the practical use of these agents, as well as in the use of other, experimental agents briefly discussed. Action, efficacy, and toxicity also determine the rational chronologic use of these drugs alone and, in particular, in combination.

Old and new drugs used in rheumatoid arthritis: a historical perspective. Part 1: the older drugs.

Rheumatoid arthritis is the paradigmatic immune-mediated inflammatory arthropathy and may be of comparatively recent, New World origin. Apart from the symptom-relieving nonsteroidal anti-inflammatory drugs, whose natural congeners have been in use since antiquity for musculoskeletal pain and inflammation, only a dozen drugs or drug classes--the disease-modifying antirheumatic drugs--are currently in common use in rheumatoid arthritis. Development of these drugs has been a notable achievement of the 20th century. Some were developed serendipitously (glucocorticoids, antimalarials), some were the product of faulty reasoning (gold, D-penicillamine), and others were applied for plausible reasons but whose mechanism remains unproven (sulfasalazine, methotrexate, minocycline). A minority were originally applied on the basis of actions that remain germane to the pathophysiology of rheumatoid arthritis as currently understood (azathioprine, cyclosporine, leflunomide, infliximab, etanercept). Among the latter are the more recently introduced and effective agents. The practical use of these drugs is determined by efficacy-toxicity considerations, which have also driven the recent development of the cyclooxygenase-2-selective nonsteroidal anti-inflammatory drugs.

In vivo cyclooxygenase expression in synovial tissues of patients with rheumatoid arthritis and osteoarthritis and rats with adjuvant and streptococcal cell wall arthritis.

Cyclooxygenase (COX), or prostaglandin (PG) H synthase, plays a role in inflammatory diseases, but very limited data exist on the regulation of COX in vivo. We, therefore, studied the in vivo expression of COX in synovia from patients with rheumatoid arthritis (RA) and osteoarthritis (OA), as well as joints of rats with streptococcal cell wall (SCW) and adjuvant arthritis. Extensive and intense intracellular COX immunostaining, which correlated with the extent and intensity of mononuclear cell infiltration, was observed in cells throughout RA synovia. Significantly less or equivocal staining was noted in OA and normal human synovia. Similarly, COX immunostaining was equivocal in the joints of normal and arthritis-resistant F344/N rats. In contrast, high level expression developed rapidly in euthymic female Lewis (LEW/N) rats throughout the hindlimb joints and overlying tissues including skin, preceding or paralleling clinically apparent experimental arthritis. COX was expressed in the joints of athymic LEW.rnu/rnu rats 2-4 d after injection of SCW or adjuvant but was not sustained. Physiological doses of antiinflammatory glucocorticoids, but not progesterone, suppressed both arthritis and COX expression in LEW/N rats. These observations suggest that, in vivo, (a) COX expression is upregulated in inflammatory joint diseases, (b) the level of expression is genetically controlled and is a biochemical correlate of disease severity, (c) sustained high level up-regulation is T cell dependent, and (d) expression is down-regulated by antiinflammatory glucocorticoids.

Endothelial cells and the pathogenesis of rheumatoid arthritis in humans and streptococcal cell wall arthritis in Lewis rats.

Endothelial cells play a fundamental role in the pathogenesis of chronic inflammatory arthritis in humans such as rheumatoid arthritis (RA), as well as experimental animal models such as streptococcal cell wall (SCW) arthritis in Lewis (LEW/N) rats. This review summarizes data in support of this concept. The earliest apparent abnormalities in synovial tissues of patients with RA and Lewis rats with SCW arthritis appear to reflect microvascular endothelial cell activation or injury. At the molecular level, the abnormalities include enhanced expression by endothelial cells of activation markers such as class II major histocompatibility complex antigens, phosphotyrosine, leukocyte adhesion molecules, oncoproteins such as c-Fos and c-Myc, and metalloproteinases such as collagenase and transin/stromelysin. The development of severe, chronic, destructive arthritis is dependent upon thymic-derived lymphocytes and is accompanied by tumorlike proliferation of cells in the synovial connective tissue stroma (blood vessels and fibroblastlike cells), which results in resorptive destruction of bone and cartilage. Multiple criteria support the analogy to a neoplastic process. Paracrine and autocrine factors such as interleukin-1 (IL-1), platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-beta), and heparin-binding fibroblast growth factors (HBGF, FGF) appear to play important roles in the generation of these lesions. Finally, in addition to the autocrine and paracrine regulatory factors, neuroendocrine factors, particularly the hypothalamic-pituitary-adrenal axis, appear to be involved in the counterregulation of the inflammatory process. The counterregulatory effects are mediated, in part, by inhibition of endothelial cell activation by corticosteroids.

Administration of IL-2-PE40 via osmotic pumps prevents adjuvant induced arthritis in rats. Improved therapeutic index of IL-2-PE40 administered by continuous infusion.

IL-2-PE40 is a chimeric cytotoxin composed of interleukin 2 (IL-2) fused to a truncated form of Pseudomonas exotoxin (PE) that lacks its binding domain. IL-2-PE40 has been shown to exhibit therapeutic potency in several models in vivo when administered i.p. twice a day. Here we show that the continuous administration of IL-2-PE40 by an osmotic pump specifically prevents the development of adjuvant induced arthritis in rats with an improved therapeutic efficacy as compared to daily repeated i.p. injections. Stabilization of IL-2-PE40 at 37 degrees C for the continuous administration by pumps was achieved by adding NAD, the substrate for the enzyme portion of the chimeric toxin.

Production of platelet derived growth factor B chain (PDGF-B/c-sis) mRNA and immunoreactive PDGF B-like polypeptide by rheumatoid synovium: coexpression with heparin binding acidic fibroblast growth factor-1.

We present evidence supporting the hypothesis that locally produced platelet derived growth factor (PDGF) B-like polypeptides, as well as heparin binding growth factor-1 (HBGF-1), are involved in stimulating the pronounced hyperplasia of rheumatoid synovial stromal fibroblastlike cells. Explanted rheumatoid synovial tissues in vitro spontaneously secreted, in a time dependent manner, mitogenic activity for rheumatoid synoviocytes that was neutralizable by anti-PDGF antibody. PDGF B/c-sis mRNA transcripts were detected in synovium from patients with rheumatoid arthritis (RA) (n = 5). Spontaneous PDGF B-like synthesis was detected by immunoprecipitation of radiolabeled PDGF B-like polypeptides secreted by explanted tissues. Furthermore, rheumatoid synovial tissues, particularly macrophage-like cells, immunostained specifically with anti-PDGF B chain. The extent and intensity of staining and mononuclear cell infiltration were highly correlated. Immunostaining of osteoarthritic and normal synovial tissues was significantly less than RA synovium. PDGF-B immunostaining of synovial specimens previously characterized for expression of HBGF-1, the precursor of acidic fibroblast growth factor (aFGF), revealed that the extent and intensity of expression of HBGF-1 and PDGF-B were highly correlated.

IL-1 regulation of transin/stromelysin transcription in rheumatoid synovial fibroblasts appears to involve two antagonistic transduction pathways, an inhibitory, prostaglandin-dependent pathway mediated by cAMP, and a stimulatory, protein kinase C-dependent pathway.

IL-1, like other agents that have been shown a capacity to induce protein kinase C, is a potent transcriptional activator of the metalloproteinase, stromelysin, in synovial and other fibroblasts. cAMP has been shown to inhibit stromelysin transcription in fibroblasts of nonsynovial origin, and is regarded as an important second messenger for IL-1. In addition to stimulating metalloproteinase transcription, IL-1 also induces PGE2 production in synoviocytes. We determined that rIL-1 alpha led to the time-dependent accumulation of intracellular cAMP in serum-starved rheumatoid synovial fibroblasts, and that the effect was blocked by indomethacin. The cAMP agonists forskolin, 3-isobutyl-1-methylxanthine, and PGE2 suppressed the IL-1 induction of stromelysin; conversely, indomethacin superinduced IL-1-elicited stromelysin mRNA. These results were recapitulated on the transcriptional level in cells transfected with the rat transin/stromelysin promoter in a reporter (CAT) construct. 2',5'-Dideoxyadenosine, an inhibitor of adenylate cyclase, also augmented the IL-1 induction of stromeylsin mRNA, as did H-8, a specific inhibitor of the cAMP-dependent protein kinase A. Staurosporine and H-7, inhibitors of protein kinase C, blocked the IL-1 induction of stromelysin mRNA. We conclude that IL-1 appears to stimulate at least two transduction pathways in synovial fibroblasts from patients with rheumatoid arthritis, and that these have antagonistic effects on the regulation of stromelysin transcription.

Detection of high levels of heparin binding growth factor-1 (acidic fibroblast growth factor) in inflammatory arthritic joints.

The synovium from patients with rheumatoid arthritis (RA) and LEW/N rats with streptococcal cell wall (SCW) arthritis, an experimental model resembling RA, is characterized by massive proliferation of synovial connective tissues and invasive destruction of periarticular bone and cartilage. Since heparin binding growth factor (HBGF)-1, the precursor of acidic fibroblast growth factor (FGF), is a potent angiogenic polypeptide and mitogen for mesenchymal cells, we sought evidence that it was involved in the synovial pathology of RA and SCW arthritis. HBGF-1 mRNA was detected in RA synovium using the polymerase chain reaction technique, and its product was immunolocalized intracellularly in both RA and osteoarthritis (OA) synovium. HBGF-1 staining was more extensive and intense in synovium of RA patients than OA and correlated with the extent and intensity of synovial mononuclear cell infiltration. HBGF-1 staining also correlated with c-Fos protein staining. In SCW arthritis, HBGF-1 immunostaining was noted in bone marrow, bone, cartilage, synovium, ligamentous and tendinous structures, as well as various dermal structures and developed early in both T-cell competent and incompetent rats. Persistent high level immunostaining of HBGF-1 was only noted in T-cell competent rats like the disease process in general. These observations implicate HBGF-1 in a multitude of biological functions in inflammatory joint diseases.

Cytokines and growth regulation of synoviocytes from patients with rheumatoid arthritis and rats with streptococcal cell wall arthritis.

Paracrine growth factors probably stimulate the pathologic proliferation of synovial fibroblast-like cells (synoviocytes) in rheumatoid arthritis (RA), but the relative importance of various factors is highly controversial. To address this problem, we compared the effects of highly purified or recombinant cytokines, in serum-free medium, on the in vitro long-term growth of synoviocytes from patients with RA and rats with streptococcal cell wall (SCW) arthritis. Of the factors tested (PDGF, aFGF, bFGF, EGF, TGF-beta, IL-1-alpha, TNF-alpha and IFN-gamma), PDGF, was clearly the most potent stimulant of long-term growth of both rat and human synoviocytes. The strong mitogenic activity of rheumatoid synovial fluids was significantly inhibited by neutralizing anti-PDGF antibody, thus confirming the importance of PDGF. EGF, TGF-beta, IL-1-alpha, TNF-alpha, and IFN-gamma had minimal effects. Similar to the effects on anchorage-independent growth, TGF-beta 1 and 2, inhibited serum- or PDGF-stimulated anchorage-dependent growth. Considered in the context of other reports, these data support the view that cytokines such as PDGF, and possibly aFGF and bFGF, play major roles in stimulating synoviocyte hyperplasia in RA and SCW arthritis, whereas TGF-beta may inhibit synoviocyte growth.

Transin/stromelysin expression in rheumatoid synovium. A transformation-associated metalloproteinase secreted by phenotypically invasive synoviocytes.

Transin is a neutral metalloproteinase whose mRNA was first isolated from rat fibroblasts that had undergone malignant transformation. The protein is highly expressed in malignant rather than benign animal tumors. Its human analog is stromelysin, a 51-kd metalloproteinase initially isolated from cultured human synoviocytes. Northern blot analysis demonstrated that rheumatoid arthritis synovial tissue contained significantly higher levels of stromelysin mRNA than did osteoarthritis synovial tissue. Cultured synoviocytes were also shown to express stromelysin mRNA, and an affinity-purified anti-peptide antiserum to stromelysin specifically immunoprecipitated the stromelysin protein from the conditioned medium of cultured explant rheumatoid synoviocytes. Immunohistochemical staining of rheumatoid synovium demonstrated specific cytoplasmic staining of cells of the synovial lining layer, stromal fibroblasts, and endothelial cells. Osteoarthritic synovia showed significantly less stromelysin staining. Similarly, rheumatoid synovia demonstrated marked nuclear staining for the proliferation- and transformation-associated Myc oncoprotein. In contrast, osteoarthritic synovia showed negligible staining. These results support the belief that the proliferative, invasive behavior of rheumatoid synoviocytes reflects the expression of biochemical features generally associated with phenotypically transformed, malignant tumors. Clearly not a malignancy, the rheumatoid synovium appears to be paracrine driven by mediators generated in local inflammatory milieu.

Transin/stromelysin expression in the synovium of rats with experimental erosive arthritis. In situ localization and kinetics of expression of the transformation-associated metalloproteinase in euthymic and athymic Lewis rats.

Transin is a neutral metalloproteinase initially isolated from malignantly transformed rat fibroblasts and subsequently shown to be homologous to human stromelysin. We performed Northern blot analysis on synovial tissue specimens from Lewis rats with proliferative and invasive streptococcal cell wall (SCW) arthritis. Transin mRNA was present in abundance, as was the mRNA of the c-myc oncogene, which is associated with cellular proliferation. Immunohistochemical staining of synovia from rats with chronic SCW arthritis showed high-level transin expression in the cells of the lining layer and underlying stroma, as well as in chondrocytes and osteoclasts in subchondral bone. Intense nuclear staining for the Myc oncoprotein was also detected with a cross-reactive antibody to v-Myc. Transin stained similarly in the early, rapid-onset, thymus-independent, acute phase of SCW arthritis. In the T cell-dependent adjuvant arthritis, transin expression was noted by day 4, 6 d before the influx of mononuclear cells and the onset of clinical disease. Athymic rats did not express transin. We concluded that transin is a marker of proliferative, invasive arthritis in rats and appears early in the course of disease development, but requires a competent immune system to sustain its expression in these model arthropathies.

Mechanisms of bone and cartilage destruction in rheumatoid arthritis: lessons from the streptococcal cell wall arthritis model in LEW/N rats.

Rheumatoid arthritis is a proliferative and erosive disease which has been described as tumor-like. Streptococcal cell wall-induced arthritis in the LEW/N rat is also tumor-like and closely simulates the features of joint destruction that develop in rheumatoid arthritis. This article discusses the mechanisms of bone and cartilage destruction in streptococcal cell wall arthritis with particular emphasis on the tumor-like behavior of synovial connective tissue cells and the role of cytokines, such as platelet-derived growth factor, transforming growth factor beta and interleukin 1, in regulating this abnormal behavior.

Platelet-derived growth factor and IL-1 interactions in rheumatoid arthritis. Regulation of synoviocyte proliferation, prostaglandin production, and collagenase transcription.

We show that platelet-derived growth factor (PDGF) and IL-1 interact in both a synergistic and antagonistic manner to regulate synovial fibroblast-like cells (synoviocytes) derived from patients with rheumatoid arthritis. PDGF and IL-1 operated synergistically in vitro to stimulate synoviocyte proliferation in the presence of indomethacin. However, when these same cells were treated with PDGF and IL-1 in the absence of indomethacin, IL-1 inhibited PDGF-stimulated synoviocyte proliferation. Moreover, exogenous PGE2, a PG known to be produced in response to IL-1, dramatically inhibited synoviocyte proliferation induced by PDGF. PDGF also acted synergistically to markedly increase production of PGE2 stimulated by IL-1. This is in contrast to the antagonistic effect PDGF had on IL-1-stimulated collagenase transcription. IL-1 stimulated collagenase transcription, but PDGF did not. It in fact inhibited IL-1 stimulation of collagenase gene expression. These data differ somewhat from those reported for dermal fibroblasts. Our data further indicate that the effects of cytokines vary from one cell type to another, even amongst "fibroblasts," and illustrate the complexity of cytokine regulation of rheumatoid synoviocyte function.

Transforming growth factor-beta production by synovial tissues from rheumatoid patients and streptococcal cell wall arthritic rats. Studies on secretion by synovial fibroblast-like cells and immunohistologic localization.

The growth of synovial fibroblast-like cells from patients with rheumatoid arthritis and rats with streptococcal cell wall (SCW)-induced arthritis in vitro under anchorage-independent conditions is inhibited by transforming growth factor-beta (TGF-beta). Because this growth factor is present in rheumatoid synovial fluids, we studied whether this cytokine might be secreted by cells in rheumatoid synovial tissue. We show that synovial tissues from patients with rheumatoid arthritis and osteoarthritis, and rats with SCW-induced arthritis, contain TGF-beta-1 mRNA. TGF-beta, predominantly type 1, was spontaneously secreted in vitro by synovial tissue explants and synovial fibroblast-like cells. In addition, TGF-beta could be detected immunohistochemically in cells throughout rheumatoid and SCW-induced arthritic rat synovial tissues. Finally, exogenous TGF-beta induced collagen and inhibited collagenase mRNA levels by cultured synoviocytes. These data support an autocrine role for TGF-beta in the regulation of synoviocytes in rheumatoid arthritis and, in light of its demonstrated effects on the immune system, suggest that TGF-beta might also have important paracrine effects on infiltrating inflammatory cells.

Chimeric cytotoxin IL2-PE40 delays and mitigates adjuvant-induced arthritis in rats.

Adjuvant arthritis in rats is a T-cell dependent "autoimmune" disease with close similarities to several forms of human arthritis. Injection of mycobacterial adjuvant leads to T-cell activation and proliferation, processes in which the de novo expression of the interleukin 2 (IL-2) receptor plays a pivotal role. The subsequent massive mononuclear cell infiltration of the joints ultimately results in complete joint destruction. Because activation of the helper/inducer subset of T lymphocytes is critical to the establishment of disease, we reasoned that IL2-PE40, a cytotoxic IL-2-Pseudomonas exotoxin fusion protein that targets the membrane-penetration and ADP-ribosylation domains of the toxin to cells bearing the IL-2 receptor, would be an effective and specific therapy. Adjuvant-injected rats were randomized to treatment with IL2-PE40, phosphate-buffered saline, or either of two control proteins related to IL2-PE40 but lacking either the receptor-binding moiety or an enzymatically active toxin domain and previously demonstrated to lack cytotoxicity in vitro. Intraperitoneal IL2-PE40 given before the establishment of overt clinical disease proved an effective and specific modifier of adjuvant arthritis by clinical, histological, and radiographic criteria. Our data suggest that IL2-PE40 may be effective in those diseases in which activated T-cells play an important role.