Strontium ranelate promotes osteogenic differentiation of rat bone mesenchymal stem cells through TGF-β1/Smad signaling pathway

ABSTRACT] AIM: To study the roles of transforming growth factor β1 (TGF-β1)/Smad signaling pathway in strontium ranelate (Sr)-induced osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs). METHODS: In the process of osteogenic differentiation of rat BMSCs, the expression of phosphorylated Smad2 (p-Smad2) and Runx2 was detected by Western blotting after the cells were treated with Sr. BMSCs were pretreated with SB431542, a selective inhibitor of TGF-β1, or Smad2 small interfering RNA (Smad2-siRNA), followed by Sr treatment, and then the expression of p-Smad2 and Runx2 was observed. At the same time, the activity of alkaline phosphatase (ALP) and the level of calcium nodules were detected to determine the osteogenic differentiation of BMSCs. RESULTS: The expression levels of p-Smad2 and Runx2 were enhanced under the action of Sr in the process of osteogenic differentiation of rat BMSCs. The expression of p-Smad2 reached to maximum when BMSCs were treated with Sr at concentration of 1 mmol/L for 1 h. The expression of Runx2 reached to maximum when BMSCs were treated with Sr at concentration of 1 mmol/L for 5 d. The pretreatment with SB431542 or Smad2-siRNA inhibited not only the expression of p-Smad2 and Runx2, but also the activity of ALP and the level of calcium nodules. CONCLUSION: Sr promotes the osteogenic differentiation of rat BMSCs through the TGF-β1/Smad signaling pathway.