Does loading influence the severity of cartilage degeneration in the canine Groove‐model of OA?

Many animal models are used to study osteoarthritis (OA). In these models the role of joint loading in the development of OA is not fully understood. We studied the effect of loading on the development of OA in the canine Groove‐model. In ten female beagle dogs OA was induced in one knee according to the Groove‐model. The animals were divided in groups with and without forced‐loading. Forced‐loading was achieved by fixing the contra‐lateral limb to the trunk 3 times a week for 4 hours. After 20 weeks joint tissues of all dogs were evaluated. Subjective evaluation revealed less movement with more loading in the forced‐loading‐group compared to the group without forced‐loading. In both groups induction of OA resulted in macroscopical and microscopical OA changes as well as alterations in cartilage metabolism characteristics for OA. Although differences were small, for some parameters they were statistically significant for the forced‐loading‐group. There were no differences between the contra‐lateral healthy joints of both groups. The present study demonstrates that in the Groove‐model intensified loading is not a prerequisite for the development of OA, although it adds to some extent to the severity of the OA. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1332–1338, 2009     

Blockade of the interleukin‐7 receptor inhibits collagen‐induced arthritis and is associated with reduction of T cell activity and proinflammatory mediators

Objective

To study the effects of interleukin‐7 receptor α‐chain (IL‐7Rα) blockade on collagen‐induced arthritis (CIA) and to investigate the effects on T cell numbers, T cell activity, and levels of proinflammatory mediators.

Methods

We studied the effect of anti–IL‐7Rα antibody treatment on inflammation and joint destruction in CIA in mice. Numbers of thymocytes, splenocytes, T cell subsets, B cells, macrophages, and dendritic cells were assessed. Cytokines indicative of Th1, Th2, and Th17 activity and several proinflammatory mediators were assessed by multianalyte profiling in paw lysates. In addition, T cell–associated cytokines were measured in supernatants of lymph node cell cultures.

Results

Anti–IL‐7Rα treatment significantly reduced clinical arthritis severity in association with reduced radiographic joint damage. Both thymic and splenic cellularity were reduced after treatment with anti–IL‐7Rα. IL‐7Rα blockade specifically reduced the total number of cells as well as numbers of naive, memory, CD4+, and CD8+ T cells from the spleen and significantly reduced T cell–associated cytokines (interferon‐γ, IL‐5, and IL‐17). IL‐7Rα blockade also decreased local levels of proinflammatory cytokines and factors associated with tissue destruction, including tumor necrosis factor α, IL‐1β, IL‐6, matrix metalloproteinase 9, and RANKL. IL‐7Rα blockade did not significantly affect B cells, macrophages, and dendritic cells. B cell activity, indicated by serum anticollagen IgG antibodies, was not significantly altered.

Conclusion

Blockade of IL‐7Rα potently inhibited joint inflammation and destruction in association with specific reductions of T cell numbers, T cell–associated cytokines, and numerous mediators that induce inflammation and tissue destruction. This study demonstrates an important role of IL‐7R–driven immunity in experimental arthritis and indicates the therapeutic potential of IL‐7Rα blockade in human arthritic conditions.

     

Exposure of human cartilage tissue to low concentrations of blood for a short period of time leads to prolonged cartilage damage: an in vitro study

OBJECTIVE: Joint bleeding, or hemarthrosis, leads in time to severe joint damage. This study was carried out to test the in vitro thresholds of exposure time and concentration that lead to irreversible joint damage, to add to the discussion on the usefulness of aspiration of the joint after a hemorrhage. METHODS: Explants of healthy human articular cartilage tissue were cultured in the presence or absence of 50% (volume/volume) blood for 1, 2, 3, or 4 days or in the presence of 0%, 5%, 10%, 20%, 30%, or 50% (v/v) blood for 4 days, followed by a 12-day period of recovery after withdrawal of blood. The effect of blood exposure on cartilage was determined by measuring the rate of proteoglycan synthesis as well as the release and content of cartilage matrix proteoglycans and the activity of matrix metalloproteinases. RESULTS: Exposure of cartilage to 50% (v/v) blood led to adverse changes that were largely independent of the exposure time. The adverse effects persisted after an initial exposure of up to or exceeding 2 days. Exposure of cartilage to increasing concentrations of blood for 4 days led to concentration-dependent adverse changes. These effects persisted when the concentration equaled or exceeded 10% (v/v) blood. Moreover, after 2 days of exposure to a blood load of 10% (v/v), the adverse effects on cartilage were not reversible. CONCLUSION: A 2-day exposure of cartilage in vitro to 10% (v/v) blood leads to prolonged impairment of joint cartilage. This suggests that aspiration of blood from the joint within 2 days after hemarthrosis should be considered to prevent blood-induced joint damage in the long term.     

Proinflammatory mediator-induced reversal of CD4+,CD25+ regulatory T cell-mediated suppression in rheumatoid arthritis

OBJECTIVE: We previously demonstrated that CD4+,CD25+ regulatory T (Treg) cells are present in increased numbers in the synovial fluid (SF) of rheumatoid arthritis (RA) patients and display enhanced suppressive activity as compared with their peripheral blood (PB) counterparts. Despite the presence of these immunoregulatory cells in RA, chronic inflammation persists. The purpose of the present study was to investigate whether particular proinflammatory mediators that are associated with RA could abrogate CD4+,CD25+ Treg-mediated suppression. METHODS: Monocyte phenotype was determined by flow cytometry and cytokine levels by enzyme-linked immunosorbent assay. Magnetically sorted CD4+,CD25- and CD4+,CD25+ T cells derived from the PB and SF obtained from RA patients were stimulated alone or in coculture with anti-CD3 monoclonal antibody (mAb) and autologous antigen-presenting cells, in the absence or presence of anti-CD28 mAb or the proinflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor alpha (TNFalpha), or IL-7. RESULTS: Monocytes from the SF of RA patients displayed increased expression of HLA class II molecules, CD80, CD86, and CD40 as compared with PB-derived monocytes, indicating their activated status. Mimicking this increased costimulatory potential, addition of anti-CD28 mAb to cocultures of CD4+,CD25- and CD4+,CD25+ T cells resulted in reduced CD4+,CD25+ Treg-mediated suppression in both PB and SF. Furthermore, IL-7 and, to a limited extent, TNFalpha, both of which are produced by activated monocytes and were detected in SF, abrogated the CD4+,CD25+ Treg-mediated suppression. In contrast, IL-6 did not influence Treg-mediated suppression. CONCLUSION: Our findings suggest that the interaction of CD4+,CD25+ Treg cells with activated monocytes in the joint might lead to diminished suppressive activity of CD4+,CD25+ Treg cells in vivo, thus contributing to the chronic inflammation in RA.     

Factor V is activated and cleaved by platelet calpain: comparison with thrombin proteolysis

Platelets are known to process human factor V during secretion and/or membrane binding. We studied the functional and structural changes produced in human factor V by purified human platelet calpain (calcium- activated thiol protease) and compared the alterations with those induced by thrombin. A maximum increase in coagulant activity of 2.5- fold was observed when factor V (1 U/mL, 33 nmol/L) was incubated with calpain (0.03 U/mL, 2.7 nmol/L) in comparison with a 8.8-fold increment for alpha-thrombin (0.7 U/mL, 8 nmol/L) at 25 degrees C. Thrombin additions to reactions initiated by calpain resulted in further activation comparable to that of thrombin alone, whereas the subsequent addition of calpain had no effect on the extent or pattern of the activation of factor V by thrombin. The cleavage pattern of factor V produced by these two enzymes are distinctly different. Although thrombin activation eventually results in four final components designated C1 (150 kd), D (105 kd), E (71 kd), and F1F2 (71 to 74 kd), calpain yields initial components of 200 kd and 160 kd within one minute. Further digestion of the 200 kd species by calpain gives rise first to a polypeptide of 160 kd that is converted to a 140 kd and a 120 kd species by two minutes with an increase in coagulant activity. Immunoblotting of these fragments with the monoclonal antibody (MoAb) B10 directed to factor V and the thrombin-generated C1 fragment yields results demonstrating a common epitope in these calpain-generated components of 200, 160, 140 and 120 kd. The degradation of the initial 160 kd polypeptide gives rise to polypeptides of 100 and 65 kd, both undetectable on immunoblotting with MoAb B10. The 130, 87, 58, and 48 kd components are of less certain origin. Thus, platelet calpain generates a complex but reproducible cleavage pattern different from thrombin that may explain the partial activation observed. Nevertheless, calpain processing may play a role in early hemostatic reactions involving platelets before the appearance of the first thrombin molecule.