Role of MAPKs in TGF-β1-induced maturation and mineralization in human osteoblast-like cells

Objectives: Our study aimed to clarify the role of mitogen-activated protein kinases (MAPKs) in transforming growth factor (TGF)-beta 1-stimulated mineralization in the human osteoblast-like MG63 cells. Methods: The viability of MG63 cells under TGF-beta 1 stimulation was assessed by MTS assay. Western blotting determined TGF-beta 1-mediated activation of extracellular signal -related protein kinase (ERK), p38, and c -Jun amino -terminal kinase (JNK). Mineralization -related gene expression was examined by quantitative real-time PCR, and mineral deposition levels were evaluated by alizarin red S staining. Results: TGF-beta 1 had no effect on MG63 cell proliferation. Activation of p38 was observed at 3 h post TGF-beta 1 stimulation. Moreover, JNK phosphorylation was upregulated by TGF-beta 1 from 1 to 6 h post stimulation, but had no activation on ERK phosphorylation throughout the experimental period. Treatment with JNK inhibitor diminished the alizarin red S -stained area in a dose -dependent manner. Mineral deposition was unaffected by MEK inhibitor, whereas p38 inhibitor increased the red -stained area. Gene expression levels of ALP and BSP were significantly decreased under treatment with JNK inhibitor and p38 inhibitor. The MEK inhibitor had no effect on the TGF-beta 1-mediated upregulation of ALP and BSP. Although all three inhibitors suppressed expression of COL I, none were found to stimulate expression of OCN. Conclusions: Human osteoblast-like MG63 cells maturation and mineralization are induced through JNK activation of MAPK signaling in response to TGF-beta 1.