A short pulse of mechanical force induces gene expression and growth in MC3T3-E1 osteoblasts via an ERK 1/2 pathway

Jason P. Hatton, Milad Pooran, Chai-Fei Li, Chris Luzzio, Millie Hughes-Fulford

Research output: Contribution to journalArticle

96 Scopus citations


Physiological mechanical loading is crucial for maintenance of bone integrity and architecture. We have calculated the strain caused by gravity stress on osteoblasts and found that 4-30g corresponds to physiological levels of 40-300 μstrain. Short-term gravity loading (15 minutes) induced a 15-fold increase in expression of growth-related immediate early gene c-fos, a 5-fold increase in egr-1, and a 3-fold increase in autocrine bFGF. The non-growth-related genes EP-1, TGF-β, and 18s were unaffected by gravity loading. Short-term physiological loading induced extracellular signal-regulated kinase (ERK 1/2) phosphorylation in a dose-dependent manner with maximum phosphorylation saturating at mechanical loading levels of 12g (p < 0.001) with no effect on total ERK. The phosphorylation of focal adhesion kinase (FAK) was unaffected by mechanical force. g-Loading did not activate P38 MAPK or c-jun N-terminal kinase (JNK). Additionally, a gravity pulse resulted in the localization of phosphorylated ERK 1/2 to the nucleus; this did not occur in unloaded cells. The induction of c-fos was inhibited 74% by the MEK1/2 inhibitor U0126 (p < 0.001) but was not affected by MEK1 or p38 MAPK-specific inhibitors. The long-term consequence of a single 15-minute gravity pulse was a 64% increase in cell growth (p < 0.001). U0126 significantly inhibited gravity-induced growth by 50% (p < 0.001). These studies suggest that short periods of physiological mechanical stress induce immediate early gene expression and growth in MC3T3-E1 osteoblasts primarily through an ERK 1/2-mediated pathway.

Original languageEnglish (US)
Pages (from-to)58-66
Number of pages9
JournalJournal of Bone and Mineral Research
Issue number1
StatePublished - Jan 1 2003
Externally publishedYes


  • Gravity
  • MAP kinase
  • Mechanical stress
  • Mechanotransduction
  • Signal transduction

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Orthopedics and Sports Medicine

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