Objective: To investigate the effects of Osterix (Osx) overexpression on the osteogenic differentiation of human periodontal ligament cells in response to mechanical force.
Methods: Human periodontal ligament cells were isolated and cultured in vitro with explant method. Cells were transfected with either an Osx expression vector pcDNA3.1 flag-Osx or the mock control vector pcDNA3.1 flag. Then, cells were centrifuged for 6 h. After transfection and centrification, the expression of Osx mRNA and protein in untransfected cells, mock-transfected cells and Osx-transfected cells were measured by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot respectively. Furthermore, the changes of mRNA expressions of core-binding factor cal (Cbfal), alkaline phosphatase (ALP), osteopontin (OPN), osteocalcin (OC), bone sialoprotein(BSP) and collagen protein al (Col I ) genes were measured to assess the differentiation of human periodontal ligament cells.
Results: At 24 h after transfection, Osx mRNA and protein level increased significantly in Osx-transfected cells (P < 0.01), while there were no significant difference in Osx mRNA and protein levels between mock-transfected cells and untransfected cells(P > 0.05). Simultaneously, the upregulated mRNA expressions of all the five osteogenic genes were observed (P < 0.05, P < 0.01). After 6 h of mechanical stimulation, a significant increase in Osx expression was shown in all three groups. However, compared to mock-transfected and untransfected cells, Osx-transfected cells further showed the highest Osx mRNA and protein expression level. Furthermore, the mRNA expressions of all five osteogenic markers in Osx-transfected cells also exhibited the greater increase and showed the highest levels.
Conclusion: The overexpression of Osx promotes the mechanical stress-induced osteogenic differentiation of human periodontal ligament cells. Osx may be essential for mechanical stress-induced differentiation of human periodontal ligament cells to osteoblas tic-like cells and be involved in orthodontic osteogenic remodeling.