Objective—To determine the effects of matrix metalloproteinase (MMP)-13, compared with interleukin (IL)-1α, 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-1α (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-1α had increased media GAG concentration at 48 and 96 hours. Aggrecan and COL2A1 mRNA expression were increased by application of MMP-13 or IL-1α. Gene expression of the catabolic mediator, MMP-3, in cartilage and synoviocytes was increased in cultures treated with MMP-13 or IL-1α. Expression of MMP-13 mRNA in cartilage was increased by IL-1α, 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.
Objective—To evaluate the effects of interleukin (IL)-1β 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-1β (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-1β–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-1β in cocultures, compared with cartilage- and synoviocyteonly cultures. Histochemical findings supported the molecular and biochemical results and revealed maintenance of matrix metachromasia in cocultured cartilage treated with IL-1β.
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-1β. Further studies involving proteomic and microarray approaches in similar coculture systems may elucidate novel therapeutic targets for the treatment of osteoarthritis.