Direct and indirect actions of fibroblast growth factor 2 on osteoclastic bone resorption in cultures.
Fibroblast growth factor 2 (FGF-2 or basic FGF) is known to show variable actions on bone formation and bone resorption. This study was undertaken to elucidate the mechanisms whereby FGF-2 affects bone metabolism, especially bone resorption, using three different culture systems. FGF-2 at 10(-9) M and higher concentrations induced osteoclastic cell formation in the coculture system of mouse osteoblastic cells and bone marrow cells, and this induction was abrogated by nonsteroidal anti-inflammatory drugs (NSAIDs). 45Ca release from prelabeled cultured mouse calvariae stimulated by FGF-2 (10(-8) M) was also inhibited by NSAIDs, and the inhibition was stronger by NSAIDs, which are more selective for inhibition of cyclooxygenase 2 (COX-2) than COX-1, suggesting the mediation of COX-2 induction. COX-2 was highly expressed and its messenger RNA (mRNA) level was stimulated by FGF-2 in osteoblastic cells whereas it was undetectable or not stimulated by FGF-2 in cells of osteoclast lineage. To further investigate the direct actions of FGF-2 on osteoclasts, resorbed pit formation was compared between cultures of purified osteoclasts and unfractionated bone cells from rabbit long bones. FGF-2 (> or = 10(-12) M) stimulated resorbed pit formation by purified osteoclasts with a maximum effect of 2.0-fold at 10(-11) M, and no further stimulation was observed at higher concentrations. However, FGF-2 at 10(-9) M - 10(-8) M stimulated resorbed pit formation by unfractionated bone cells up to 9.7-fold. NS-398, a specific COX-2 inhibitor, did not affect the FGF-2 stimulation on purified osteoclasts but inhibited that on unfractionated bone cells. We conclude that FGF-2 at low concentrations (> or =10(-12) M) acts directly on mature osteoclasts to resorb bone moderately, whereas at high concentrations (> or = 10(-9) M) it acts on osteoblastic cells to induce COX-2 and stimulates bone resorption potently.
Kawaguchi
H
H
Department of Orthopaedic Surgery, Faculty of Medicine, University of Tokyo, Japan.
Chikazu
D
D
Nakamura
K
K
Kumegawa
M
M
Hakeda
Y
Y
D000135:Acid Phosphatase / Q000032:analysis; D000818:Animals; D000831:Animals, Newborn; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D015415:Biomarkers; D001854:Bone Marrow Cells / Q000502:physiology; D001862:Bone Resorption / Q000378:metabolism / Q000473:pathology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured / Q000187:drug effects; D018920:Coculture Techniques; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D003804:Dentin / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D017308:Etodolac / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D005480:Flurbiprofen / Q000494:pharmacology; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D007527:Isoenzymes / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics; D008565:Membrane Proteins; D051379:Mice; D009578:Nitrobenzenes / Q000494:pharmacology; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism; D010010:Osteoclasts / Q000187:drug effects* / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis / Q000235:genetics; D011453:Prostaglandins / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D011817:Rabbits; D012886:Skull / Q000166:cytology; D013449:Sulfonamides / Q000494:pharmacology; D000071681:Tartrate-Resistant Acid Phosphatase
D000894:Anti-Inflammatory Agents, Non-Steroidal; D015415:Biomarkers; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D008565:Membrane Proteins; D009578:Nitrobenzenes; D011453:Prostaglandins; D012333:RNA, Messenger; D013449:Sulfonamides; D016222:Fibroblast Growth Factor 2; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D017308:Etodolac; D005480:Flurbiprofen; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; C496512:Ptgs1 protein, mouse; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase; D002118:Calcium; D007213:Indomethacin