Prolonged administration of low-dose MTX in rats causes significant osteopenia via suppression of osteoblast activity and stimulation of osteoclast recruitment, which results in increased bone resorption.

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Objective. We have recently shown that administration of long-term, lowdose methotrexate (MTX) causes severe osteopenia in female rats. This osteopenia is characterized both by decreased osteoblast function without a decrease in osteoblast numbers, and by increased bone resorption that is believed to represent a physiologic remodeling response by osteoclasts. The present study investigates the effects of varying doses of MTX on mouse bone cells in culture.Methods. Cells were obtained by sequential digestion of neonatal mouse calvariae, and cultured with fetal calf serum (10% for osteoblast-like cells and 2% for osteoclast-like cells). After 1 week, MTX was added to each culture in concentrations of 0.6 pM, 0.4 pM, 0.2 jdf, 0.1 jdf, 1 IN, and 0.5 nM. All experiments were done on 24 wells for each MTX concentration and for the controls. The effect on osteoblastic cells was assessed, at 7 days, by cell counts and by measurement of lysate alkaline phosphatase and supernatant osteocalcin levels, and, at 21 days, by analysis of the calcified matrix production, which was cultured with ascorbic acid and Fglycerophosphate. For osteoclastic cells, cell count and lysate acid phosphatase levels were determined.Resuks. Levels of osteoblastic cells and lysate alkaline phosphatase were not changed by any of the concentrations of MTX. Matrix calcification and supernatant osteocalcin levels were diminished by MTX in a dose-responsive manner. Osteoclast-like cell numbers and acid phosphatase levels were not significantly affected by MTX. Conclusion.These results suggest that diminished mouse osteoblastic cell function Occurs with very low mean concentrations of MTX, in a dose-responsive manner. The mechanism seems to be inability of the cell to synthesize and calcify matrix, possibly through defective osteocalcin production. Thus, low-dose MTX may have an important impact on bone density by slowing osteoblastic matrix production.Methotrexate (MTX) is a folate antagonist that is commonly used in the treatment of rheumatoid arthritis (RA) and other inflammatory diseases. It is known that administration of MTX in high doses to treat childhood leukemias and breast cancer has been associated with the development of bone pain, severe osteopenia, and fractures (14). The inhibition of conversion of folic acid to tetrahydrofolic acid by competitive inhibition of the enzyme, dihydrofolate reductase, and the subsequent inhibition of DNA synthesis, accounts for the antiproliferative effects of MTX on cancer cells, and may account for the osteopenia observed in these patients (1). Limited human data on high-dose regimens ( 2 4 , however, point to stimulation of bone resorption, rather than decrease in bone formation, as the etiologic mechanism of osteopenia in these patients. Our previous studies investigated the skeletal effects of long-term, low-dose MTX in rats, using a regimen similar to that used for inflammatory disease states. In those studies, we demonstrated significant osteopenia, which was characterized by diminished osteoblast fu...

Objective. Familial associations of the antiphospholipid antibody syndrome (APS) offer the opportunity to study genetic mechanisms of autoantibody production and disease, but are unusual. We identified a family, including identical twins and their mother, in which all members had systemic lupus erythematosus (SLE) and presented with different manifestations of the APS.Methods. Review of case histories and clinical laboratory results, antiphospholipid antibody (aPL) studies, complement C4 protein and gene analysis, and HLA typing of family members were performed.Results. Each of the 3 family members presented with a different clinical association of the APS. These ~~~-~~~~The opinions and assertions contained herein are those of the authors and do not necessarily represent those of the United