Background/Purpose: Osteoarthritis (OA) is a complex joint disease characterized by a progressive loss of articular cartilage (AC) and synovial inflammation. The latest theories of OA pathogenesis implicate the interplay between mechanical damage and chronic inflammation that has been associated to the activation of the innate immune system, intricately involved in the development of this low-grade inflammation. During the course of OA, Toll-like receptor (TLR) activation has been related to the release of cytokines and inflammatory mediators, which further aggravates synovitis and AC damage. In this scenario, hyaline chondrocytes seem to acquire a hypertrophic-like phenotype associated to AC degradation. 6-shogaol (6S), an effective anti-inflammatory Ginger derivative, is able to inhibit TLR4-mediated innate immune responses. Our aim was to study the therapeutic benefit of 6-shogaol treatment in an OA mice model and its effect in the modulation of hypertrophic markers in chondrocyte cultures.

Methods: C57BL/6 male mice were randomly assigned to two groups: control (n=7) and OA (n=17). OA was induced by transection of the medial menisco-tibial ligament. Nine OA mice started receiving 6S (15mg/kg/day; OA+6S) since surgery. After 8 weeks, animals were euthanized and joints were collected. Chondrogenic differentiation was induced in vitro in the pre-chondrogenic cell line ATDC5 by ITS (insulin-transferrin-selenium) in presence or absence of 5×10^-6M 6S. Gene expression of hypertrophic markers as well as mineralization and proteoglycan synthesis were determined.

Results: Both synovial inflammation and AC damage were more severe in OA animals (Control: 0.1±0.1; OA: 3.0±0; p<0.05, and Control: 0.5±0.2, OA: 5.4±0.6; p<0.05, respectively) with a significant reduction in OA+6S animals (2.4±0.2; p<0.05 and 2.6±0.5 p<0.05 vs. OA, respectively). Type X Collagen X (Col X) and MMP13 immunohistochemistry showed an increase in the AC of OA and OA-6S mice vs control animals (ColX: Control: 0.13±0.03, OA: 0.93±0.10; OA-6S: 0.43±0.10; p<0.05 vs Control and MMP13: Control: 0.35±0.10, OA: 0.68±0.10, OA-6S: 0.28±0.07, p<0.05 vs Control), while a significant reduction was found in 6S-treated mice (p<0.05 vs OA). Similar results were found in the synovium and meniscus for MMP13 and in meniscus for Col X. In addition, 6S was able to significantly inhibit the expression of Collagen X, Ihh and MMP13 in ITS-stimulated cells after 14 and 21 days of culture. Furthermore, 6S prevented the increase in mineralization and proteoglycan synthesis in ITS-stimulated ATDC5 cells after 14 days of culture (p<0.05 ITS vs basal, and p<0.05 ITS-stimulated vs ITS), assessed by Alizarin red and Alcian blue staining, respectively.

Conclusion: Our results showed that 6S significantly prevented cartilage degradation and synovial inflammation, in parallel to a reduction of the presence of hypertrophic markers in the cartilage of OA mice. In vitro, 6S inhibited the chondrogenic differentiation of ATDC5 cells. These results suggest that 6S could work as a good treatment in OA both inhibiting hypertrophic differentiation markers and reducing the severity of joint damage in an OA murine model.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-tlr-4-inhibitor-6-shogaol-as-a-treatment-in-osteoarthritis-trough-the-modulation-of-chondrocyte-hypertrophy-and-matrix-calcification/