Mechanisms of fibroblast growth factor-2 modulation of vascular endothelial growth factor expression by osteoblastic cells.
Normal bone growth and repair is dependent on angiogenesis. Fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor (VEGF), and transforming growth factor-beta (TGFbeta) have all been implicated in the related processes of angiogenesis, growth, development, and repair. The purpose of this study was to investigate the relationships between FGF-2 and both VEGF and TGFbeta in nonimmortalized and clonal osteoblastic cells. Northern blot analysis revealed 6-fold peak increases in VEGF mRNA at 6 h in fetal rat calvarial cells and MC3T3-E1 osteoblastic cells after stimulation with FGF-2. Actinomycin D inhibited these increases in VEGF mRNA, whereas cycloheximide did not. The stability ofVEGF mRNA was not increased after FGF-2 treatment. Furthermore, FGF-2 induced dose-dependent increases in VEGF protein levels (P < 0.01). Although in MC3T3-E1 cells, TGFbeta1 stimulates a 6-fold peak increase in VEGF mRNA after 3 h of stimulation, we found that both TGFbeta2 and TGFbeta3 yielded 2- to 3-fold peak increases in VEGF mRNA levels noted after 6 h of stimulation. Similarly, both TGFbeta2 and TGFbeta3 dose dependently increased VEGF protein production. To determine whether FGF-2-induced increases in VEGF mRNA may have occurred independently of TGFbeta, we disrupted TGFbeta signal transduction (using adenovirus encoding a truncated form of TGFbeta receptor II), which attenuated TGFbeta1 induction of VEGF mRNA, but did not impede FGF-2 induction ofVEGF mRNA. In summary, FGF-2-induced VEGF expression by osteoblastic cells is a dose-dependent event that may be independent of concomitant FGF-2-induced modulation of TGFbeta activity.
Saadeh
P B
PB
Department of Surgery, University of Connecticut, Farmington 06032, USA.
Mehrara
B J
BJ
Steinbrech
D S
DS
Spector
J A
JA
Greenwald
J A
JA
Chin
G S
GS
Ueno
H
H
Gittes
G K
GK
Longaker
M T
MT
D000818:Animals; D015152:Blotting, Northern; D001842:Bone and Bones / Q000196:embryology; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D016228:Endothelial Growth Factors / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D008222:Lymphokines / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010006:Osteoblasts / Q000378:metabolism*; D011247:Pregnancy; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D008222:Lymphokines; D019384:Nucleic Acid Synthesis Inhibitors; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D016222:Fibroblast Growth Factor 2; D003609:Dactinomycin; D003513:Cycloheximide