The effect of methotrexate on mouse bone cells in culture.
OBJECTIVE
We have recently shown that administration of long-term, low-dose 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 microM, 0.4 microM, 0.2 microM, 0.1 microM, 1 nM, 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 beta-glycerophosphate. For osteoclastic cells, cell count and lysate acid phosphatase levels were determined.


RESULTS
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.


CONCLUSIONS
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.
May
K P
KP
RAF Lakenheath General Hospital, UK.
Mercill
D
D
McDermott
M T
MT
West
S G
SG
D000135:Acid Phosphatase / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001851:Bone Diseases, Metabolic / Q000503:physiopathology; D002118:Calcium / Q000378:metabolism; D002452:Cell Count; D002478:Cells, Cultured / Q000187:drug effects / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D005260:Female; D008727:Methotrexate / Q000494:pharmacology*; D051379:Mice; D008813:Mice, Inbred ICR; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D011247:Pregnancy; D012886:Skull / Q000166:cytology
D000469:Alkaline Phosphatase; D000135:Acid Phosphatase; D002118:Calcium; D008727:Methotrexate