Biochemical Mechanisms of Articular Destruction

Experimental transmission of AA amyloidosis by injecting the AA amyloid protein into interleukin-1 receptor antagonist knockout (IL-1raKO) mice

The incidence of AA amyloidosis is high in humans with rheumatoid arthritis and several animal species, including cats and cattle with prolonged inflammation. AA amyloidosis can be experimentally induced in mice using severe inflammatory stimuli and a coinjection of AA amyloid; however, difficulties have been associated with transmitting AA amyloidosis to a different animal species, and this has been attributed to the "species barrier." The interleukin-1 receptor antagonist knockout (IL-1raKO) mouse, a rodent model of human rheumatoid arthritis, has been used in the transmission of AA amyloid. When IL-1raKO and BALB/c mice were intraperitoneally injected with mouse AA amyloid together with a subcutaneous pretreatment of 2% AgNO3, all mice from both strains that were injected with crude or purified murine AA amyloid developed AA amyloidosis. However, the amyloid index, which was determined by the intensity of AA amyloid deposition, was significantly higher in IL-1raKO mice than in BALB/c mice. When IL-1raKO and BALB/c mice were injected with crude or purified bovine AA amyloid together with the pretreatment, 83% (5/6 cases) and 38% (3/8 cases) of IL-1raKO mice and 17% (1/6 cases) and 0% (0/6 cases) of BALB/c mice, respectively, developed AA amyloidosis. Similarly, when IL-1raKO and BALB/c mice were injected with crude or purified feline AA amyloid, 33% (2/6 cases) and 88% (7/8 cases) of IL-1raKO mice and 0% (0/6 cases) and 29% (2/6 cases) of BALB/c mice, respectively, developed AA amyloidosis. These results indicated that IL-1raKO mice are a useful animal model for investigating AA amyloidogenesis.

Cathepsin B and cystatin C play an inflammatory role in gouty arthritis of the knee

BACKGROUND

To relate the expression of the matrix degrading proteinase cathepsin B and its endogenous inhibitor cystatin C in the synovial fluid (SF) to the clinical and laboratory variables of joint inflammation in gouty arthritis of the knee.

METHODS

Thirty-nine SF samples were obtained from inflamed knees of patients with acute gout. The levels of cathepsin B, cystatin C, urokinase-type plasminogen activator (uPA), soluble uPA receptor (suPAR) and PA inhibitor type-1 (PAI-1), activities of matrix metalloproteinase-2 (MMP-2) and MMP-9, and cell counts as well as local arthritis activity scores (LAS) were examined.

RESULTS

The increases of cathepsin B levels correlated with increased leukocyte and neutrophil counts, latent MMP-9 (pro-MMP-9) activities, uPA, suPAR and PAI-1 levels, and uPA/PAI-1 ratios. Increased cystatin C levels corresponded closely with increased LAS, leukocyte and neutrophil counts, pro-MMP-9 activities, uPA, suPAR and PAI-1 levels, and uPA/PAI-1 ratios. Moreover, there was a correlation between cathepsin B and cystatin C levels.

CONCLUSIONS

These results show a high correlation between the cathepsin B/cystatin C system and markers of joint inflammation in acute gout of the knee, demonstrating the pathologic role of cathepsin B and cystatin C in inflammation.

Pelvic organ prolapse in fibulin-5 knockout mice: pregnancy-induced changes in elastic fiber homeostasis in mouse vagina

Pelvic organ prolapse is strongly associated with a history of vaginal delivery. The mechanisms by which pregnancy and parturition lead to failure of pelvic organ support, however, are not known. Recently, it was reported that mice with null mutations in lysyl oxidase-like 1 (LOXL1) develop pelvic organ prolapse. Elastin is a substrate for lysyl oxidase (LOX) and LOXL1, and LOXL1 interacts with fibulin-5 (FBLN5). Therefore, to clarify the potential role of elastic fiber assembly in the pathogenesis of pelvic organ prolapse, pelvic organ support was characterized in Fbln5-/- mice, and changes in elastic fiber homeostasis in the mouse vagina during pregnancy and parturition were determined. Pelvic organ prolapse in Fbln5-/- mice was remarkably similar to that in primates. The temporal relationship between LOX mRNA and protein, processing of LOXL1 protein, FBLN5 and tropoelastin protein, and desmosine content in the vagina suggest that a burst of elastic fiber assembly and cross linking occurs in the vaginal wall postpartum. Together with the phenotype of Fbln5-/- mice, the results suggest that synthesis and assembly of elastic fibers are crucial for recovery of pelvic organ support after vaginal delivery and that disordered elastic fiber homeostasis is a primary event in the pathogenesis of pelvic organ prolapse in mice.

Recent advances in the management of the child who has hemophilia

This article discusses recent advances in the management of the child who has hemophilia.

Arthroscopic synovectomy for hemophilic joint disease in a pediatric population

Children with hemophilia can develop progressive arthropathy. Arthroscopic synovectomy has been used to reduce hemarthroses, but few long-term results have been published. In this article the authors review their first 12 years of experience. Data are reported on 44 pediatric patients (69 joints: 39 ankles, 21 elbows, 7 knees, 2 shoulders). The median age at surgery was 10 years Median follow-up was 79 months. Joints with sufficient follow-up data showed a median bleeding frequency decline of 84% (P < 0.001). Median arc of motion was stable or improved in the year after surgery in ankles, elbows, and shoulders. Complications were rare. Radiographic scores worsened slightly. In this largest analysis of arthroscopic synovectomy for children with hemophilia, rehabilitation was not problematic.

Arthroscopic synovectomy for hemophilic joint disease in a pediatric population

Children with hemophilia can develop progressive arthropathy. Arthroscopic synovectomy has been used to reduce hemarthroses, but few long-term results have been published. In this article the authors review their first 12 years of experience. Data are reported on 44 pediatric patients (69 joints: 39 ankles, 21 elbows, 7 knees, 2 shoulders). The median age at surgery was 10 years Median follow-up was 79 months. Joints with sufficient follow-up data showed a median bleeding frequency decline of 84% (P < 0.001). Median arc of motion was stable or improved in the year after surgery in ankles, elbows, and shoulders. Complications were rare. Radiographic scores worsened slightly. In this largest analysis of arthroscopic synovectomy for children with hemophilia, rehabilitation was not problematic.

Blood Monocyte Migration to Acute Lung Inflammation Involves Both CD11/CD18 and Very Late Activation Antigen-4-Dependent and Independent Pathways

In acute lung inflammation, blood neutrophils and monocytes migrate into the lung parenchyma and bronchoalveolar space. The infiltration of the inflamed lung by monocytes is poorly understood because of difficulties in quantifying these cells in the presence of resident macrophages. Radiolabeled monocytes were used to study monocyte migration into the inflamed rat lung. Monocytes and neutrophils were purified from blood, labeled with 51Cr and 111In, respectively, and injected i.v. into rats given an intratracheal injection of LPS. The accumulation of 51Cr-labeled monocytes increased &gt;10-fold in the lung parenchyma and 170-fold in the bronchoalveolar lavage (BAL) 18 h after LPS. 111In-labeled neutrophils increased &gt;30-fold in the lung tissue and 500-fold in the BAL. Treatment of rats with a blocking anti-CD18 mAb inhibited monocyte accumulation in the lung and BAL by about 30%, whereas blocking very late activation Ag-4 (VLA-4) had no effect. Combined blockade of VLA-4 and CD18 inhibited approximately 30% of the migration to the lung parenchyma, but decreased the BAL by 80%. Monocyte migration to cutaneous inflammation was completely abolished by the combined mAb treatment. Neutrophil accumulation in the lung and BAL was not decreased by blocking either CD18 or VLA-4 and was only partially reduced by blocking CD18 plus VLA-4. Thus, monocyte migration to the LPS inflamed lung is substantially CD11/CD18 and VLA-4 independent, but accumulation in BAL is mediated by CD18 and VLA-4. Monocytes as well as neutrophils may use a previously unrecognized endothelial adhesion and migration pathway in the lung.

Levels of circulating collagenase, stromelysin-1, and tissue inhibitor of matrix metalloproteinases 1 in patients with rheumatoid arthritis. Relationship to serum levels of antigenic keratan sulfate and systemic parameters of inflammation

OBJECTIVE

To measure serum levels of matrix metalloproteinase-1 (MMP-1), matrix metalloproteinase-3 (MMP-3), and tissue inhibitor of MMP-1 (TIMP-1) in patients with rheumatoid arthritis (RA) and in age-matched control subjects, and to determine how these correlate with serum levels of antigenic keratan sulfate (KS) and other biochemical and clinical indicators of disease activity.

METHODS

Immunoassays were used to measure levels of MMP-1, MMP-3, TIMP-1, and antigenic KS. Radiologic and functional joint scores were based upon Steinbrocker's criteria. Erythrocyte sedimentation rates (ESR) and levels of C-reactive proteins (CRP) were measured.

RESULTS

In RA patients, levels of MMP-3 and TIMP-1 were significantly increased, and strongly correlated with the ESR and CRP levels but not with radiologic or functional joint scores. Levels of antigenic KS were significantly lower in RA patients and correlated negatively with systemic parameters of inflammation and serum levels of TIMP-1.

CONCLUSIONS

The increase in serum levels of MMP-3 and TIMP-1 appears to reflect systemic inflammation in RA. The inverse correlation between serum levels of TIMP-1 and antigenic KS suggests that an upregulation of TIMP-1 synthesis might be responsible for the apparent suppression of cartilage aggrecan catabolism in patients with severe inflammatory changes.

The role of tumour necrosis factor-alpha and IL-1 in polymorphonuclear leucocyte and T lymphocyte recruitment to joint inflammation in adjuvant arthritis

The mediators involved in leucocyte recruitment to joints during arthritis are not fully defined, but two important proinflammatory cytokines, IL-1 and tumour necrosis factor-alpha (TNF-alpha), are produced in joints in rheumatoid arthritis (RA). We investigated in the rat adjuvant arthritis model whether endogenous IL-1 and TNF-alpha contribute to joint inflammation and polymorphonuclear leucocyte (PMNL) and T lymphocyte infiltration. The migration of 51Cr-labelled rat blood PMNL and 111In-labelled T lymphocytes to the joints of rats with adjuvant arthritis was measured along with plasma protein extravasation, which was quantified using 125I-labelled human albumin. Rats with active arthritis of 5 days' duration received i.p. non-immune serum, polyclonal neutralizing anti-serum to rat TNF-alpha, antiserum to IL-1 alpha and IL-1 beta, or both anti-TNF plus anti-IL-1 for 5 days. Treatment with anti-IL-1 alpha and IL-1 beta did not affect plasma protein extravasation, or PMNL or T lymphocyte accumulation in the joints (i.e. talar joint, hind paws, and tail) despite the fact that this treatment inhibited 80-90% of the PMNL migration into dermal sites injected with IL-1 alpha or IL-1 beta. In contrast, anti-TNF-alpha treatment significantly improved clinical scores, decreased plasma protein extravasation by 60-80%, inhibited PMNL accumulation by 40-50% and decreased T lymphocyte accumulation by 30-50%. Treatment with anti-IL-1, together with anti-TNF-alpha, significantly potentiated the inhibition of T lymphocyte accumulation observed with anti-TNF-alpha alone. These results indicate that endogenous TNF-alpha production may play an important role in the inflammatory changes and leucocyte recruitment in this experimental model of human arthritis, while IL-1 may have a less important role in leucocyte recruitment to these joints.

Toxicity of complement for chondrocytes. A possible source of cartilage degradation in inflammatory arthritis

Cartilage from patients with rheumatoid arthritis and from animals with antigen-induced arthritis is frequently contaminated with complement-containing immune complexes. A possible role for complement activation in cartilage degradation was modeled in vitro by exposing cultured bovine chondrocytes to homologous serum, and determining cytotoxicity by monitoring the release of intracellular 51Cr. Complement activation was found to be cytotoxic, having maximal effect at 20-30% serum by 18 h. Serum toxicity was ablated by heat (50 degrees C, 20 min) or methylamine treatment but not by EGTA, suggesting that in these experiments activation occurred by the alternate route. The implications of the results are discussed in relation to ultrastructural evidence for the involvement of complement in the pathogenesis of cartilage degradation in inflammatory arthritis.

Detection of Stromelysin and Collagenase in Synovial Fluid From Patients with Rheumatoid Arthritis and Posttraumatic Knee Injury

OBJECTIVE

To quantify stromelysin and collagenase in synovial fluid (SF) from patients with rheumatoid arthritis (RA) or traumatic knee injury.

METHODS

Stromelysin and collagenase were measured in the SF of 33 patients with RA or posttraumatic knee injury, using specific double-antibody sandwich enzyme-linked immunosorbent assays. Stromelysin was fractionated from representative SF, and the molecular form was identified by immunoblot analysis.

RESULTS

The stromelysin concentration was approximately 20-fold higher than the collagenase concentration in the fluids from patients with RA and approximately 8-fold higher in the fluids from patients with traumatic injury. For both metalloproteinases, there was a higher enzyme concentration in RA SF than in the SF from patients with trauma (stromelysin 40.1 +/- 26 micrograms/ml [mean +/- SD] in RA SF, 8.5 +/- 15 micrograms/ml in trauma SF; collagenase 2.2 +/- 3.3 micrograms/ml in RA SF, 1.1 +/- 2.3 micrograms/ml in trauma SF). The majority of the stromelysin within the SF bound to reactive red-agarose and was identified as prostromelysin based on electrophoretic mobility and immunoblotting with monospecific antibodies.

CONCLUSION

The finding of high levels of stromelysin in SF from patients with RA supports the proposal that this enzyme may play a role in the connective tissue degradation observed in this disease.

T lymphocyte migration to arthritic joints and dermal inflammation in the rat: differing migration patterns and the involvement of VLA-4

The migration of T lymphocytes into arthritic joints of rats with adjuvant arthritis was examined and compared to the accumulation of the same cells in cutaneous inflammation, since previous studies had shown that only a subpopulation of T lymphocytes, found enriched in peritoneal exudates (sPEL), migrated efficiently to cutaneous inflammatory sites. Surprisingly, lymphocyte migration to the inflamed joint included T cells from most of the recirculating lymphocyte pool, including sPEL, spleen, peripheral lymph node (PLN), and Peyer's patches, and was much more rapid than migration through either cutaneous sites or PLNs. Treatment of sPEL with antibody to VLA-4 inhibited sPEL accumulation in the joints, while anti-VLA-4 treatment did not affect the accumulation of PLN T cells. It is concluded that the arthritic joint not only attracts inflammation-seeking lymphocytes (sPEL), through at least a partially VLA-4 dependent interaction, but also large numbers of lymphocytes which normally migrate to PLNs through a VLA-4-independent mechanism.

Gingival crevicular fluid elastase-inhibitor complex: correlation with clinical indices and subgingival flora

This investigation analyzed, in a cross-sectional study, the possible relationship between gingival crevicular fluid (GCF) elastase-like protease (ELP) levels and the periodontal clinical parameters or the presence of specific bacteria in subgingival plaque. A total of 388 periodontal sites from 8 adult periodontitis patients were examined for plaque index (PII), gingival index (GI), pocket depth (PD) and alveolar bone loss (ABL). GCF ELP levels were determined as ELP alpha-1 protease inhibitor (ELP-alpha 1-PI) complex levels with a commercially available ELISA. Subgingival plaque samples were tested for the presence of Bacteroides gingivalis, B. intermedius and Actinobacillus actinomycetemcomitans by indirect immunofluorescence (IF) microscopy. GCF ELP-alpha 1-PI levels were then correlated with clinical periodontal indices and proportions of IF-positive bacteria per site. Statistically significant positive correlations were found between GCF ELP-alpha 1-PI concentrations and subgingival Bacteroides proportions. When the sites examined were analyzed depending on the level of each clinical parameter, the levels of these correlations changed. A. actinomycetemcomitans correlated highly (r = 0.716) with ABL for sites with low GI score. The correlations between GCF ELP-alpha 1-PI and B. gingivalis (r = 0.642) or B. intermedius (r = 0.774) were the highest for ABL less than or equal to 20% and PD less than or equal to 3 mm, respectively. The strong association between GCF ELP-alpha 1-PI concentrations and subgingival bacteria previously associated with advancing periodontitis indicates that measurement of GCF ELP-alpha 1-PI concentrations may be useful in the evaluation of periodontal sites, especially those with very little or no tissue destruction.

Collagenase production at the border of granulation tissue in a healing wound: macrophage and mesenchymal collagenase production in vivo

We demonstrated the cells producing collagenase and the time course of collagenase-production at early stages of wound healing, using histology and two immunohistochemical procedures on cross sections of rat skin harvested 0, 3, 5, 7 and 12 days after full-thickness incisions. A monospecific rabbit polyclonal antibody to neutral collagenase purified from rat myometrial cells was used to demonstrate collagenase production. Specificity of this reaction was confirmed by blocking the reaction with excess homogeneously purified antigen. Macrophages were simultaneously labelled using a mouse anti-rat monoclonal antibody recognizing exclusively mature macrophages. Intracellular collagenase was not reliably detectable at day 0, but was prominent at days 3 and 5 and thereafter declined. Double labeling technique showed occasional macrophages producing collagenase in the developing granulation tissue, but most cells labeled as macrophages were negative for collagenase. Most activity was found in fibroblasts adjacent to granulation tissue elements. Since the granulation tissue parallels revascularization in a dendritic pattern, a cross section at three days typically shows an annulus of collagenase-positive cells surrounding a branch of the active granulation tissue. At days 5, 7 and 12 after wounding the pattern of collagenase expression became indistinct as more tissue was involved in the granulation process. However, double-labelling for macrophages and collagenase showed the dichotomy between collagenase expression and presence of macrophages to persist. The finding that collagenase is produced in connective tissue adjacent to granulation tissue suggests an inductive process, possibly due to diffusion of cytokines produced by granulation tissue elements.

Type XI collagen-degrading activity in human osteoarthritic cartilage

Homogenates of 6 samples of human osteoarthritic cartilage were shown to degrade exogenous type XI collagen. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the cleavage products generated by each homogenate were similar, and they were identical to those obtained by cleavage of the substrate with purified gelatinase. Enzyme activity, which was inhibited by EDTA, was greater in extracts of fibrillated osteoarthritic cartilage than in extracts of grossly normal cartilage from the same joint or in extracts of cartilage from joints with osteonecrosis. Activation with APMA enhanced digestion, but breakdown was apparent in extracts of fibrillated osteoarthritic cartilage even without APMA. Enzymatic degradation of type XI collagen could play a significant role in the turnover of articular cartilage in health and disease states.

Mononuclear cells enhance prostaglandin E2 production of polymorphonuclear leukocytes via tumor necrosis factor alpha

To clarify the interactions between mononuclear cells and polymorphonuclear leukocytes, and to identify the cytokine(s) that mediate the interaction, the effects of a culture supernatant of LPS-stimulated mononuclear cells on production of arachidonic acid metabolites of polymorphonuclear cells were studied. The culture supernatant of LPS-stimulated mononuclear cells increased production of prostaglandin E2 of polymorphonuclear cells. TNF alpha, but not IL-1, IL-2, IL-6, or IFN gamma, enhanced the prostaglandin E2 production when added in vitro. Additionally, an anti-rTNF alpha monoclonal antibody inhibited the stimulating activity of the culture supernatants. TNF alpha, produced by mononuclear cells, appears to play an important role in the development of inflammation, such as rheumatoid arthritis, by enhancing the arachidonic acid metabolism of the polymorphonuclear cells.

Inflammatory synovial fluid and absorbable suture strength

The effect of inflammatory synovial fluid upon several absorbable sutures commonly used for meniscus repair was studied by implanting lengths of these sutures into unstable, arthritic rabbit knees and, after varying lengths of time (1-6 weeks), testing their breaking strength. Both polyglactin-910 (Vicryl) and polyglycolic-acid (Dexon) sutures retained only minimal breaking strength 3 weeks after implantation. Chromic gut sutures demonstrated a steady reduction in breaking strength until they retained only 6% of their original strength at 5 weeks and none at 6 weeks. Polydioxanone (PDS) sutures began to lose breaking strength at 2 weeks and retained only 40% of their original strength 5 weeks after implantation. The rate of loss in polydioxanone breaking strength was faster in inflammatory synovial fluid than previously reported in the normal synovial joint. Braided polyester sutures (Mersiline) showed no loss of breaking strength over the duration of this test. While the choice of suture is only one variable influencing the outcome of a meniscus repair, this study demonstrates that only polydioxanone and green braided polyester sutures retain any strength 6 weeks after implantation (the time of immobilization commonly recommended for meniscal repairs). Complete meniscal healing can require several months. In the absence of compelling evidence to the contrary, the use of nonabsorbable suture materials for meniscal repair seems the most appropriate choice.