Fluid stress with multiple mechanisms to enhance the cell cycle progression of osteoblastic cells from G1 to S phase / 中国矫形外科杂志

ABSTRACT

[Objective] To investigate into the cellular mechanism of growth promotion due to shear stress by studying G1-phase events responsible for the suppression of cell transition from the G1 to S phase of the cell cycle,and to establish the most suitable physiological stress to stimulate bone formation.[Methods]The osteoblasts derived from Kunming murine's calvaria were exposed to Fliud shear stress(FSS12 dyn/cm2)for 0,0.25,0.5,1,2,4 h,respectively.In the flow chamber,its impact on cell proliferation,differentiation and the effection of cell cycle's G1/S checkpoint were recorded.The cell proliferation was studied by MTT assay.The cell differentiation was assessed through alkaline phosphatase(ALP)activity assay.Flow-cytometry,immunofluorescence and RT-PCR techniques were used to evaluate the proportion of S phase in cell cycle,the activity of CDK2,CDK4 and the expression of E2F-1,p27mRNA,which demonstrate how FSS underlying multiple mechanisms to enhance the cell cycle progression from G1 to S phase.[Results]FSS increased proliferation and advanced the time in cell growth curve,but after 1,2,4 h,the proliferation was inhibited.The FSS also increased the ALP activity,which were significantly stimulated at 0.25 and 0.5 h after shear stress(128% and 158 % of control);but the FSS decreased ALP activity at 1,2,and 4 hs.The proportion of S phase in cell cycle raised within the early period.The S phase rate significantly increased at 0.5 h(P