The Effects Of IRS-1 On The Proliferation, Differentiation And Expressions Of OPG/RANKL And MMPs In MC3T3-E1 Cells

PART ONEThe Effect of Estradial on the Expression Profile of IRS-1 during MC3T3-E1 Cells DifferentiationObjective: To observe the effect of estradial on the expression profile of IRS-1 during murine preosteoblastic MC3T3-E1 cells differentiation.Methods: Alkaline phosphatase (ALP) activity was determined by pnitrophenyl phosphate assay, osteocalcin (OC) was measured by RIA. The expression levels of Collagen I (COL I ), osteopontin(OPN), bone sialoprotein(BSP) and IRS-1 mRNA in MC3T3-E1 cells were examined using semi-quantitive RT-PCR. IRS-1 protein level was evaluated by Western Blot. The mineralization of MC3T3-E1 cells were stained using Alizarin Red-S method.Results: Collagen I was expressed at an early stage, reached a maximum level on the 6th day. The ALP activity was rapidly increased and achieved a maximal level on the 12th through 18th day, then gradually decreased. Osteocalcin, osteopontin and bone sialoprotein gradually increased with the time. By Alizarin Red-S staining, murine preosteoblastic MC3T3-E1 cells displayed cell accumulation on the 18th day and formed the typical mineralization nodules on the 30th day. IRS-1 mRNA and protein levels gradually increased during differentiation of...