FIGURE 5.

Involvement of the signaling molecules up- or down-stream of PDGFR-α in MMP-13 induction by mechanical strain. The adherent MC3T3-E1 cells were prepared for testing at 8% stretch for 3 or 30 min to examine PDGFR-α phosphorylation and MMP-13 gene expression. Immunoblot analysis was performed using anti-p-PDGFR-α, anti-PDGFR-α, or anti-GAPDH (as a control) antibody (A). Total RNAs from control and strained cells were amplified by RT-PCR using mRNAs of the MMP-13, and β-actin as templates. Representative mRNA levels of MMP-13 and β-actin genes (as an internal control) were shown (B). The inhibitors included in the assay were AG1296 (for PDGFR-α), LY294002 (for PI3K), GF109203X (for total PKC), Gö6976 (for calcium-dependent PKC), and rottlerin (for selective calcium-independent PKC-δ). Data are summarized and expressed as mean ± S.E. of at least three independent experiments (bar graph). *, p < 0.05; ^#, p < 0.01, as compared with the stretch alone.