RESUMO
OBJECTIVE: To investigate the impact of systemic inhibition of interleukin 6 (IL-6) or signal transducer and activator of transcription (Stat3) in an experimental model of osteoarthritis (OA). METHODS: Expression of major catabolic and anabolic factors of cartilage was determined in IL-6-treated mouse chondrocytes and cartilage explants. The anti-IL-6-receptor neutralising antibody MR16-1 was used in the destabilisation of the medial meniscus (DMM) mouse model of OA. Stat3 blockade was investigated by the small molecule Stattic ex vivo and in the DMM model. RESULTS: In chondrocytes and cartilage explants, IL-6 treatment reduced proteoglycan content with increased production of matrix metalloproteinase (MMP-3 and MMP-13) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS-4 and ADAMTS-5). IL-6 induced Stat3 and extracellular signal-regulated kinase (ERK) 1/2 signalling but not p38, c-Jun N-terminal kinase or Akt. In the DMM model, Stat3 was activated in cartilage, but neither in the synovium nor in the subchondral bone. Systemic blockade of IL-6 by MR16-1 alleviated DMM-induced OA cartilage lesions, impaired the osteophyte formation and the extent of synovitis. In the same model, Stattic had similar beneficial effects on cartilage and osteophyte formation. Stattic, but not an ERK1/2 inhibitor, significantly counteracted the catabolic effects of IL-6 on cartilage explants and suppressed the IL-6-induced chondrocytes apoptosis. CONCLUSION: IL-6 induces chondrocyte catabolism mainly via Stat3 signalling, a pathway activated in cartilage from joint subjected to DMM. Systemic blockade of IL-6 or STAT-3 can alleviate DMM-induced OA in mice.
Assuntos
Cartilagem/metabolismo , Interleucina-6/antagonistas & inibidores , Interleucina-6/metabolismo , Osteoartrite/metabolismo , Fator de Transcrição STAT3/antagonistas & inibidores , Fator de Transcrição STAT3/metabolismo , Proteína ADAMTS4/metabolismo , Proteína ADAMTS5/metabolismo , Animais , Anticorpos/farmacologia , Apoptose/efeitos dos fármacos , Células Cultivadas , Condrócitos , Óxidos S-Cíclicos/farmacologia , Modelos Animais de Doenças , Interleucina-6/farmacologia , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Masculino , Metaloproteinase 13 da Matriz/metabolismo , Metaloproteinase 3 da Matriz/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Osteoartrite/prevenção & controle , Osteófito/prevenção & controle , Proteoglicanas/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptores de Interleucina-6/imunologia , Sinovite/prevenção & controle , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Sclerostin, mainly produced by osteocytes, is now considered a major regulator of bone formation. Identified from patients with a low bone mass, sclerostin inhibits the Wnt pathway by binding to LRP5/6 and subsequently increases bone formation. Sclerostin may also play a role in the mediation of systemic and local factors such as calcitriol, PTH, glucocorticoids and tumor necrosis factor-alpha. Circulating sclerostin levels increase with age and with the decline of kidney function. However, they are surprisingly higher in patients with a high bone mineral density, suggesting that sclerostin may be a relevant marker of the pool of mature osteocytes. The anti-anabolic properties lead to the development of anti-sclerostin biotherapies that are under current evaluation. The results of these clinical trials will open new promising opportunities for the treatment of osteoporosis and bone fragility fractures.
Assuntos
Envelhecimento/genética , Proteínas Morfogenéticas Ósseas/genética , Marcadores Genéticos/genética , Osteogênese/genética , Osteoporose/genética , Proteínas Adaptadoras de Transdução de Sinal , Proteínas Morfogenéticas Ósseas/fisiologia , Osso e Ossos/metabolismo , Fraturas Espontâneas/genética , Fraturas Espontâneas/fisiopatologia , Marcadores Genéticos/fisiologia , Humanos , Osteoporose/tratamento farmacológico , Via de Sinalização Wnt/genética , Via de Sinalização Wnt/fisiologiaRESUMO
OBJECTIVE: Wnt signaling is a master regulator of joint homeostasis, but its role in osteoarthritis (OA) remains unclear. This study was undertaken to characterize the activation of Wnt/ß-catenin in knee joints of mice with OA and to assess how inhibiting this pathway in bone could affect cartilage. METHODS: OA was induced by partial meniscectomy in Topgal mice and in transgenic mice overexpressing Dkk-1 under the control of the 2.3-kb Col1a1 promoter (Col1a1-Dkk-1-Tg mice). Wnt/ß-catenin activation was assessed by X-Gal staining at baseline and at weeks 4, 6, and 9. Cartilage and bone damage was analyzed in Col1a1-Dkk-1-Tg mice with OA at week 6. Primary chondrocytes and cartilage explants were used to assess the effect of Dkk-1 on cartilage catabolism. RESULTS: In meniscectomized Topgal mice, Wnt was mainly activated in osteocytes from the subchondral bone at week 6 after OA induction, as well as in osteophytes and synovium at week 4. Chondrocytes from damaged zones expressed X-Gal from week 4. Dkk-1 expression was high in chondrocytes in control mouse knees (mean ± SEM 84.2 ± 3.1%) but decreased greatly in knees of meniscectomized mice from week 4 (mean ± SEM 14.4 ± 3.8%). The OA score was lower in meniscectomized Col1a1-Dkk-1-Tg mice at week 6 compared with wild-type mice (5.1 ± 0.6 versus 8.4 ± 0.6; P = 0.002). Subchondral bone fraction and osteophyte volume were decreased. However, cartilage explants from Col1a1-Dkk-1-Tg mice showed proteoglycan loss and increased NITEGE expression. Expression of vascular endothelial growth factor (VEGF) was reduced in osteoblasts from Col1a1-Dkk-1-Tg mice, thereby decreasing expression of messenger RNA for matrix metalloproteinases in chondrocytes. CONCLUSION: Wnt activation in OA affects the whole joint, particularly bone. Selective inhibition of this pathway in bone by Dkk-1 decreased OA severity through VEGF inhibition.