Synoviocytes are more sensitive than cartilage to the effects of minocycline and doxycycline on IL-1alpha and MMP-13-induced catabolic gene responses.

The objective of this study was to determine the primary articular tissue target of doxycycline and minocycline. Synoviocytes-cartilage cocultures (n = 4) were treated with MMP-13 (25 ng/mL medium) or IL-1 (1.0 ng/mL medium) for 24 h. Doxycycline (4.3, 0.43, 0.043 microM) or minocycline (10, 1.0 or 0.1 microM) were then added and cultures were continued for 96 h. Cartilage and media were analyzed for GAG content. Quantitative PCR was used to measure cartilage MMP-3, MMP-13, aggrecan, COL2A1, ADAMTS-4, and ADAMTS-5 expression, and synoviocyte MMP-3, MMP-13, ADAMTS-4, and ADMATS-5 expression. Total and active MMP-3, MMP-13, and ADAMTS 4/5 enzymes were measured in culture medium. All concentrations of doxycycline and minocycline diminished GAG accumulation in the media. All concentrations of minocycline, but only the highest concentration of doxycycline decreased MMP-3 and MMP-13 expression in synoviocytes but not cartilage, and basal ADAMTS-5 mRNA levels in both synoviocytes and cartilage. Only minocycline decreased active MMP-13 protein in synoviocytes. In summary, the protective effects of tetracycline compounds are more pronounced in synoviocytes than cartilage, and following minocycline compared to doxycycline. Studies to determine the molecular mechanism of action of the tetracyclines in synoviocytes might lead to the design of targeted therapeutics for the treatment of OA or RA.

Hsp90 mediates insulin-like growth factor 1 and interleukin-1beta signaling in an age-dependent manner in equine articular chondrocytes.

OBJECTIVE: Many metabolic processes in chondrocytes thought to contribute to age-related changes in the extracellular matrix are influenced by known roles of Hsp90. Age-related decreases in the level of Hsp90 have been documented in numerous cell types and could contribute to cartilage degeneration. The aim of this study was to investigate the roles of age and Hsp90 in insulin-like growth factor 1 (IGF-1) and interleukin-1beta (IL-1beta) signaling in chondrocytes. METHODS: Levels of Hsp90 messenger RNA (mRNA) and protein, with respect to age, were determined by quantitative real-time polymerase chain reaction (PCR) and Western blot analysis, respectively. The Hsp90 inhibitor geldanamycin (50 nM, 100 nM, or 500 nM) was used to assess age-related responses to Hsp90 with concurrent IGF-1 or IL-1beta stimulation of chondrocytes. Quantitative real-time PCR was used to measure COL2A1 and matrix metalloproteinase 13 (MMP13) gene expression; Western blot analysis was performed to determine the phosphorylation status of p42/44 and Akt/protein kinase B. RESULTS: The effects of Hsp90 inhibition with geldanamycin were concentration dependent. Inhibition of Hsp90 with 100 nM or 500 nM geldanamycin blocked IGF-1-induced cell proliferation, Akt and p42/44 activation, and COL2A1 expression. Basal and IL-1beta-induced up-regulation of MMP13 mRNA was blocked by all concentrations of geldanamycin tested. Gain-of-function assays with Hsp90 resulted in increased expression of MMP13 mRNA. CONCLUSION: These results suggest that Hsp90 is involved in opposing signaling pathways of cartilage homeostasis, and that catabolic responses are more sensitive to Hsp90 inhibition than are anabolic responses. Further studies are needed to determine the role of Hsp90 inhibition in osteoarthritis in order to assess its potential as a therapeutic target.

Assessment of cartilage degradation effects of matrix metalloproteinase-13 in equine cartilage cocultured with synoviocytes.

OBJECTIVE: To determine the effects of matrix metalloproteinase (MMP)-13, compared with interleukin (IL)-1alpha, on cartilage matrix molecule gene expression in a coculture system of equine cartilage explants and synoviocytes. SAMPLE POPULATION: Articular cartilage and synovium specimens harvested from femoropatellar joints of 4 horses, aged 3 to 5 years. PROCEDURES: Synoviocytes were isolated and cocultured with cartilage explants. Cultures were treated with human recombinant MMP-13 (1, 25, or 100 ng/mL) or IL-1alpha (0.01, 0.1, 1.0, or 10 ng/mL) for 96 hours, with medium exchange at 48 hours. Cartilage extracts and media were analyzed for glycosaminoglycan (GAG) content, and results were adjusted to cartilage DNA content. Quantitative PCR was performed on mRNA from cartilage (MMP-3, MMP-13, aggrecan, and collagen type IIB [COL2A1]) and synoviocytes (MMP-3 and MMP-13), and results were adjusted to 18S ribosomal subunit mRNA expression. Treatments were performed in triplicate, and the experiment was repeated 4 times. RESULTS: Cultures treated with MMP-13 or IL-1alpha had increased media GAG concentration at 48 and 96 hours. Aggrecan and COL2A1 mRNA expression were increased by application of MMP-13 or IL-1alpha. Gene expression of the catabolic mediator, MMP-3, in cartilage and synoviocytes was increased in cultures treated with MMP-13 or IL-1alpha. Expression of MMP-13 mRNA in cartilage was increased by IL-1alpha, but decreased in synoviocytes by MMP-13 treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Results support the use of recombinant MMP-13 in a coculture system of synoviocytes and cartilage explants for the study of osteoarthritis.

Assessment of the catabolic effects of interleukin-1beta on proteoglycan metabolism in equine cartilage cocultured with synoviocytes.

OBJECTIVE: To evaluate the effects of interleukin (IL)-1beta on proteoglycan metabolism in equine cartilage explants when cultured in the presence of synoviocytes. SAMPLE POPULATION: Samples of cartilage and synovium collected from the femoropatellar joints of three 2- to 3-year-old horses. PROCEDURES: 3 experimental groups were established: cartilage explants only, synoviocytes only, and cartilage explants-synoviocytes in coculture. In each group, samples were cultured with or without IL-1beta (10 ng/mL) for 96 hours. Glycosaminoglycan (GAG) content of cartilage and medium samples was measured by use of a spectrophotometric assay; RNA was isolated from synoviocytes and cartilage and analyzed for expression of matrix metalloproteinases (MMP)-3 and -13 (cartilage and synoviocytes), aggrecan (cartilage), collagen type IIB (cartilage), and 18S as a control (cartilage and synoviocytes) by use of quantitative PCR assays. Cartilage matrix metachromasia was assessed histochemically. RESULTS: IL-1beta-induced GAG loss from cartilage was significantly less in cocultures than in cartilage-only cultures. Cartilage aggrecan gene expression was also significantly less downregulated and synoviocyte MMP-3 expression was less upregulated by IL-1beta in cocultures, compared with cartilage- and synoviocyte only cultures. Histochemical findings supported the molecular and biochemical results and revealed maintenance of matrix metachromasia in cocultured cartilage treated with IL-1beta. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that synoviocytes secrete 1 or more mediators that preferentially protect matrix GAG metabolism from the degradative effects of IL-1beta. Further studies involving proteomic and microarray approaches in similar coculture systems may elucidate novel therapeutic targets for the treatment of osteoarthritis.