The Interaction Between Caveolin-1and β-catenin In Osteoblastic Differentiation Of Bone Marrow Stromal Cells ST2

Objective:TO investigate the interaction between caveolin-1and β-catenin in bone marrow stromal cells ST2directed to differentiate into osteoblasts and its mechanism.Method and Results:1. During the directed differentiation into osteoblasts, caveolin-1protein expression (Western Blotting) of ST2was shown no significant differences.2. On the different growing day (3d,6d,9d,12d,15d), we used western blot to observe the level of β-catenin and caveolin-1protein, and the expression of caveolin-1mRNA and β-catenin mRNA via RT-PCR on ST2-induced osteoblasts.The results showed that caveolin-1protein in the1-9th day express higher,from the ninth day beginning to gradually decrease;the expression of β-catenin gradually increased during the3-12th day, but significantly reduced in the15th day. mRNA expression of caveolin-1showed the same changes, Nevertheless, the mRNA expression of β-catenin were significantly up-regulated in the sixth day, the9th day down,followed by expression of no significant change.3. We transfect the RNAi plasmid cav-13to down-regulate the level of caveolin-1protein on9th day. The protein expression of P-catenin decreased along with reduced caveolin-1, which were partial inhibited by GSK-3β inhibiter-LiCl (5,10mM). LiCl also increased β-catenin rather than caveolin-1protein expression on osteoblastic differentiation and mineralization stage.4. The differentiation and mineralization of induced osteoblasts was severally evaluated via ALP activity in cell level(PNPP) in medium after the6d,9d,12d,15d and mineralized nodule formation VON KOSSA staining in medium after the15th,18th day. compared with control group there was marked differences ALP activity in high concentration LiCl group and others there was no marked differences ALP activity. Mineralized nodule formation was substantial reduced when LiCl treated, and there were less nodule formation in10mM LiCl group than in5mM LiCl group. Conclusion:β-catenin can regulate the differentiation of ST2-induced osteoblasts through the wnt/β-catenin signaling pathway which promote osteoblast differentiation.Caveolin-1may negative modulate the mineralization of ST2-induced osteoblasts by Wnt/β-catenin pathway. It may be due to down-regulate the expression of caveolin-1protein to promote the degradation of β-catenin, which ultimately furtherance the mineralization of osteoblast.