ects of methotrexate on normal articular cartilage in vitro and in vivo

Objective—Methotrexate (MTX) has become the disease modifying drug of choice for the treatment of rheumatoid arthritis (RA). Direct eVects of MTX on articular cartilage in vivo and in vitro were studied to determine possible adverse eVects of the drug. Methods—For in vitro experiments, adult bovine articular cartilage explants were cultured in the presence of MTX (0 to 100 μM), and eVects on DNA and matrix metabolism were studied. For in vivo studies, 48 adult female rabbits were treated with MTX (30 mg/kg/week intramuscularly) or placebo, respectively, for up to 12 weeks, and eVects on the cartilage of the femoral condyles were assessed. Results—In vitro, MTX dose dependently increased the uptake of [H]-thymidine, and decreased incorporation of [H]-duridine into chondrocytes with a half maximal eVect at 0.03 μM, suggesting inhibition of thymidylate-synthetase activity by the drug. MTX also dose dependently reduced the proportion of chondrocytes in S-phase, as determined by flow cytometry. MTX did not aVect LDH release from chondrocytes or the proportion of viable cells, nor did it change the rate of protein synthesis, proteoglycan synthesis, proteoglycan breakdown, or the hydrodynamic size of newly synthesised proteoglycans. In vivo, MTX did not appreciably aVect proteoglycan synthesis of the chondrocytes, proteoglycan content of the cartilage matrix, density of the chondrocyte population, or histological integrity of the cartilage. Conclusions—The data suggest the absence of major adverse eVects by MTX on articular cartilage proteoglycan metabolism. Chondrocyte DNA metabolism seems to be changed by MTX only in concentrations and exposition periods clearly exceeding those found in synovial fluid of RA patients receiving the commonly prescribed doses of the drug. (Ann Rheum Dis 1998;57:414–421) Rheumatoid arthritis (RA) is a chronic inflammatory joint disease often leading to destruction of articular cartilage, periarticular bone, ligaments, and tendons. Treatment of RA has changed over recent years toward an earlier and more aggressive application of disease modifying anti-rheumatic drugs (DMARDs), and increased use of these drugs has been shown to positively influence the disability index of RA patients. Among DMARDs, methotrexate (MTX) is probably the one most widely used today, and seems to have in many clinics replaced injectable gold salts as the drug of choice after non-steroidal anti-inflammatory drugs (NSAIDs). Clinical studies demonstrate a relatively rapid onset of action of MTX in RA compared with other DMARDs, and double blind trials have proved the eYcacy of MTX in RA in both the short and the long term. 3 The mode of action of MTX in RA is not yet fully understood. High dose MTX seems to suppress cell replication in general and tumour growth in particular by inhibiting the activity of dihydrofolate reductase, an enzyme involved in DNA and purine biosynthesis. In contrast, weekly pulse therapy withMTX in low doses of 7.5 to 25 mg, as used to treat RA, probably does not significantly interfere with DNA metabolism but may rather exert an antiinflammatory eVect in RA and related disorders. While the mechanisms underlying this presumed anti-inflammatory eVect are still unclear, interference by MTX with leucocyte migration, expression of proteinases, and with the activity of cytokines may be involved. Widespread use of methotrexate for the treatment of RA has raised interest in possible direct eVects of MTX on articular cartilage. Few data, however, have as of yet been published on this topic. Initial degenerative cartilage changes have been described in patients receiving high doses of MTX in combination with other anti-cancer drugs for malignancy, and also in experimental animals treated with low doses of the drug. In contrast, articular cartilage from MTX treated RA patients undergoing total knee replacement contained less metalloproteinase activity than cartilage from a control group of RA patients who did not take MTX. Moreover, low dose MTX had limited therapeutic eVects in a rabbit model of osteoarthritis (OA). Finally, the rate of proteoglycan synthesis of cultured cartilage was found to be unaVected by MTX. While in RA patients, cartilage in inflamed joints presumably benefits from reduction of synovitis by MTX, negative MTX eVects on cartilage from joints unaVected by RA cannot be excluded. In this study, we therefore investigated the eVects of MTX on normal articular cartilage in vitro and in vivo.