Fibroblast growth factor-2 is an immediate-early gene induced by mechanical stress in osteogenic cells

Chai-Fei Li, Millie Hughes-Fulford

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

Fifteen minutes of physiological MS induces FGF-2 in osteogenic cells. Here, we show that MS induced proliferation in both MC3T3-E1 and BMOp cells isolated from Fgf2+/+ mice; FgC2-/- BMOp cells required exogenous FGF-2 for a normal proliferation response. The induction of fgf-2 is mediated by PKA and EMK pathways. Introduction: Mechanical stress (MS) induces gene expression and proliferation of osteogenic MC3T3-E1 cells. We have previously shown that physiological levels of MS in MC3T3-E1 cells causes extracellular signal-regulated kinase (ERK)1/2 phosphorylation. Here we evaluate the induction and importance of fibroblast growth factor-2 (FGF-2) for MS-induced proliferation. Materials and Methods: We characterized the MS induction of fgf-2 using a 15-minute pulse of 120 μstrain and studied the stability of fgf-2 message using actinomycin D. Bone marrow stromal cells (BMOp) isolated from Fgf2-/- and Fgf2+/+ mice were used to study the importance of FGF-2 in MS-induced proliferation. Results: We found that the induction of fgf-2 by MS is dependent on both protein kinase A (PKA) and ERK pathways. MS transiently induces fgf-2 within 30 minutes. FGF-2 receptor (FGFR2) was also significantly increased within 1 h. All three isoforms of FGF-2 (24,22, and 18 kDa) were significantly increased by MS. The MS-mediated increase of fgf-2 mRNA was caused by new synthesis and not stabilization. Pretreatment of MC3T3-E1 cells with cycloheximide showed that the induction of fgf-2 did not require new protein synthesis. Pretreating MC3T3-E1 cells with the mitogen-activated protein kinase (MAPK)TERK kinase 1/2 (MEK1/2) inhibitor, U0126, or H-89, a PKA inhibitor, significantly inhibited the induction of fgf-2, showing that mechanical induction of fgf-2 is dependent on ERK and PKA signaling pathways. The downstream consequence of a single 15-minute stress pulse was a 3.5-fold increase in cell number in MC3T3-E1 compared with growth in nonstressed control cells. In studies using bone marrow osteoprogenitor cells (BMOp) isolated from Fgf2+/+ and Fgf2-/- mice, we found that FGF-2 was necessary for a full proliferative response to MS. Conclusions: These studies show that FGF-2 is an immediate-early gene induced by MS, and its expression is mediated by both the PKA and MAPK signal transduction pathways. FGF-2 was required for a full proliferative response.

Original languageEnglish (US)
Pages (from-to)946-955
Number of pages10
JournalJournal of Bone and Mineral Research
Volume21
Issue number6
DOIs
StatePublished - Jun 1 2006
Externally publishedYes

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Keywords

  • Cox-2
  • Growth factors
  • Mechanical stress
  • Osteoblast
  • Signal transduction

ASJC Scopus subject areas

  • Surgery

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