Statins in the Osteoblastic Differentiation of Mouse Periodontal Ligament Cells

Objectives: Recent studies demonstrated that hydroxyl methylglutaryl-CoA reductase inhibitor, so called statins (cholesterol lowering drugs), have a bone stimulatory effect. Few studies have been done concerning the effect of statins on periodontal ligament (PDL) cells. We investigated the osteoblastic differentiation of PDL cells and its mechanism by lovastatin and simvastatin.

Methods: Mouse PDL cells were cultured in DMEM with lovastatin or simvastatin. Metabolic cell activity after 24 hrs was measured using XTT assay. Expression of osteocalcin (OC), bone sialoprotein (BSP), bone morphogenetic protein(BMP)-2, and alkaline phosphatase (ALP) mRNA was evaluated by RT-PCR. Bone forming ability in cell cultures was characterized by examining ALP activity and alizarin red staining. Activity of osteocalcin gene (OG2) and osteoblast-specific cis-acting elements (OSE) in OG2 promotor by statins was also measured via transfection and luciferase assay. Activation of Erk1/2 MAP kinase was determined by western blot analysis of the cell lysates.

Results: Statin treatment did not inhibit cell activity at the concentration of 10^-6M. A significant increase in OC, BSP, BMP-2 and ALP mRNA expression was detected when mouse PDL cells were treated with lovastatin and simvastatin at different concentrations (10^-9 ~10^-6M). The increasing trends in ALP activity (2.3 fold, 2.0 fold) after 7 days, mineralized bone nodule formation after 21 days and OG2 promotor and OSE activity (1.93 fold, 2.15 fold) were observed in lovastatin and simvastatin treated cells. In western blot analysis, statin treated cells expressed Erk1/2 MAP kinase.

Conclusion: These results suggested that lovastatin and simvastatin exhibit positive effect on osteoblastic differentiation of mouse PDL cells by activation of Erk 1/2 pathway.

(This study was supported by second stage Brain Korea 21 project for school of dentistry.)