Title: Combination of simvastatin and bone morphogenetic protein-2 enhances the differentiation of osteoblasts by regulating the expression of phospho-Smad1/5/8
Abstract: Statins inhibit 3-hydroxy-3-methylglutaryl-coenzyme A reductase, which catalyzes the conversion of 3-hydroxy-3-methylglutaryl-coenzyme A to mevalonate, a rate-limiting step in cholesterol synthesis. A number of studies have demonstrated bone-promoting effects when simvastatin is applied locally with different carriers in various animal models. In the prsent study, the dose-dependent impact of simvastatin and bone morphogenetic protein-2 (BMP-2) on the cellular proliferation and differentiation of osteoprecursor cells was evaluated. The alkaline phosphatase activity (ALP) test was performed to assess differentiation, and protein expression related to bone formation, including that of phospho-Smad1/5/8 (pSmad1/5/8), was measured using western blot analysis to evaluate the underlying mechanism(s). Cultures grown in the presence of 0.1 µM simvastatin with 60 ng/ml BMP-2 exhibited the highest value for ALP activity. The results of the western blot analysis indicated that the addition of simvastatin upregulated pSmad1/5/8 expression and the combination of 0.1 µM simvastatin and 60 ng/ml BMP-2 produced a significant increase in protein expression. Based on these findings, it was concluded that the combination of simvastatin and BMP-2 produced positive effects on the differentiation of osteoprecursor cells. The results also suggest that the combination of simvastatin and BMP-2 has synergistic effects that are achieved through the BMP pathway by enhancing the expression of pSmad1/5/8 expression.