The effects of fibroblast growth factor-2 on human neonatal calvaria osteoblastic cells are differentiation stage specific.
Fibroblast growth factors (FGFs) appear to play an important role in human cranial osteogenesis. We therefore investigated the effects of recombinant human FGF-2 (rhFGF-2) on human calvaria (HC) osteoblastic cells. Immunocytochemical analysis showed that confluent HC cells express both FGF receptors -1 and -2. In short-term culture, rhFGF-2 (0.1-100 ng/ml, 2-5 days) increased HC cell growth and decreased alkaline phosphatase (ALP) activity and type I collagen (ColI) synthesis, as evaluated by P1CP levels. When HC cells were induced to differentiate in long-term culture in the presence of 50 microg/ml ascorbic acid and 3 mM phosphate, HC cells initially proliferated, then ALP activity and ColI synthesis decreased and calcium content in the extracellular matrix increased. Continuous treatment with rhFGF-2 (50 ng/ml) for 1-28 days, or a transient rhFGF-2 treatment for 1-7 days, slightly increased DNA synthesis at 7 days, whereas a late treatment for 8-28 days had no effect on cell growth. The continuous and transient treatments with rhFGF-2 decreased ALP activity, ColI synthesis, and matrix mineralization. This was associated with a transient fall in osteocalcin (OC) production at 7 days. In contrast, the late rhFGF-2 treatment for 8-28 days only slightly inhibited ALP activity and increased matrix mineralization. In addition, both continuous and late treatments with rhFGF-2 increased OC production in more mature cells at 3-4 weeks of culture. We also found that the early and late treatments with rhFGF-2 had opposite effects on transforming growth factor beta2 production in proliferating cells and more mature cells. The results show that rhFGF-2 slightly stimulates cell growth and reduces the expression of osteoblast markers in less mature cells, whereas it induces OC production and matrix mineralization in more mature cells, indicating that the effects of FGF-2 are differentiation stage specific and that FGF-2 may modulate HC osteogenesis by acting at distinct stages of cell maturation.
Debiais
F
F
INSERM Unit 349, Cell and Molecular Biology of Bone and Cartilage, and Department of Radioimmunology, Lariboisière Hospital, Paris, France.
Hott
M
M
Graulet
A M
AM
Marie
P J
PJ
D000469:Alkaline Phosphatase / Q000378:metabolism; D001846:Bone Development / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis; D005109:Extracellular Matrix / Q000187:drug effects; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D006801:Humans; D007223:Infant; D010006:Osteoblasts / Q000187:drug effects*; D015675:Osteocalcin / Q000096:biosynthesis; D010012:Osteogenesis / Q000187:drug effects; D010446:Peptide Fragments / Q000378:metabolism; D011347:Procollagen / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis; D051496:Receptor, Fibroblast Growth Factor, Type 1; D051497:Receptor, Fibroblast Growth Factor, Type 2; D017468:Receptors, Fibroblast Growth Factor / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology; D012886:Skull / Q000166:cytology / Q000187:drug effects; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000096:biosynthesis
D010446:Peptide Fragments; D011347:Procollagen; D017468:Receptors, Fibroblast Growth Factor; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C042813:procollagen type I carboxy terminal peptide; D016222:Fibroblast Growth Factor 2; D015675:Osteocalcin; D003094:Collagen; C496348:FGFR1 protein, human; C496353:FGFR2 protein, human; D020794:Receptor Protein-Tyrosine Kinases; D051496:Receptor, Fibroblast Growth Factor, Type 1; D051497:Receptor, Fibroblast Growth Factor, Type 2; D000469:Alkaline Phosphatase; D002118:Calcium