Effects Of Mechanical Strain On Expression Of BSP/OPN MRNA In Cementoblasts In Vitro

Background and objective: During orthodontic tooth movement ,The remodeling of alveolar bone is active, Meanwile ,cementum also undergoes both resorption and deposition. Cementoblast plays an important role in the progress of root resorption and repair. Cementoblast is located on the surface of root cementum to inhibit the attachment of the osteoclast and form the new cementum-like tissue in the lacuna on the resorpted root surface. The pathologic resorption is formed when the balance of resorption and repair is disturbed. Orthodontically induced root resorption is the most frequent unwanted side effect of orthodontic tooth movement that is unavoidable. Although many researchers focus on it ,the pathogenesis of root resorption is still not clear.It is not known how orthodontic force influences the function of cementoblast and what is the relationship between the function change of cementoblast with root resorption and repair.The aim of present research is to determine the effects of the mechanical strain on the express of the mineral associated gene BSP and OPN in cementoblast in vitro.Methods: Cementoblasts OCCM30 were cultured in DMEM with 10% FBS for 48. hours, then subjected to mechanical strain by four-point bending system with tension and compression stress at 2000μstrain and 4000μstrain at 0.5Hz frequency for3h, 6h, 12h, 24h. BSPand OPN mRNA were analysed with real time quantitive RT-PCR after mechanical loading. Statistical significance was determined for each comparison using the one-way ANOVA, and p<0.05 was statistically considered significant.Results:1. Cementoblasts are sensitive cells to mechanical strain.2. 2000/4000μstrain tension and compression both suppressed BSP mRNA expression of Cementoblasts. 4000μstrain suppressed stronger than 2000μstrain.3. OPN mRNA expression of Cementoblasts was increased in response to compression stress after 31k 6h mechanical loading,then suppressed after 12h,24h loading. while Tension stress almost suppressed OPN mRNA expression all times.Conclusion:1. Mechanical strain suppressed BSP mRNA expression of Cementoblasts and is believed inhibit the capability of cementoblast to synthesize cementum matrix.2. It is suggest that cementoblast regulates the function of osteoclast by the different expression of OPNmRNA after mechanical loading .