The Effect Of IGF1R On The Rat Chondrocytes Proliferation And Matrix Synthesis Under Periodic Mechanical Stress

Objective:To investigate the effects of insulin-like growth factor receptor?IGF1R?on proliferation and extracellular matrix synthesis in rat chondrocytes under periodic mechanical stress.Methods:The rat chondrocytes were isolated and cultured in vitro.They were randomly divided into four groups:0h stress group,0.5h stress group,1h stress group,and 2h stress group,each experimental group were treated by cyclic mechanical stretch stress treated for 0h,0.5h,1h and 2 h respectively;Western Blot analysis was performed for IGF1R and phospho-IGF1R levels and chose an array of non-pressure cells as control of each group.The Gel-Pro Analyzer software was used for semi-quantitative analysis of gray value to compare the differences of phospho-IGF1R/total IGF1Rbetween non-pressure and pressure groups in each time periods.The blank group and cyclic mechanical stretch treated cells were separately divided into control group and IGF1R-suppressor group which treated with Linsitinib(C₂₆H₂₃N₅O,OSI-906)or IGF1R shRNA.The expression of ERK1/2 and phospho-ERK1/2 were determined by Western blot 1h later.After 8h,collagen?and aggrecan levels were analyzed by qPCR.Three days later,cell counting or CCK-8 assays were performed to examine the cell proliferation of each group.SPSS18.0 software was used for statistical analysis,and student t test was used to compare the differences between the two groups.Results:In 0h stress groups,the phospho-IGF1R levels had no differences?t=0.255,P=0.811?.The levels of phospho-IGF1R were significantly increased in the cyclic mechanical stretch treated groups?t values were-5.881,-6.172 and-10.518respectively,P value<0.05?.The inhibitors of IGF1R obviously decreased the phospho-ERK1/2 expression?OSI-906 suppressor group t=3.074,,IGF1R shRNA suppressor group t=3.990,P values<0.05?.The mRNA levels of collagen??OSI-906 suppressor group t=3.243,,IGF1R shRNA suppressor group t=3.621,P values<0.05?and aggrecan?OSI-906 suppressor group t=3.128,,IGF1R shRNA suppressor group t=3.608,P values<0.05?significantly reduced thus extracellular matrix synthesis was blocked because of IGF1R suppressors.The IGF1R inhibitors significantly contributed to the attenuation of cyclic mechanical stretch treated cells proliferation?Cell counting method:OSI-906 suppressor group t=6.096?IGF1R shRNA suppressor group t=6.668,CCK-8 assays:OSI-906 suppressor group t=2.835?IGF1R shRNA suppressor group t=3.467,all the P values<0.05?.Conclusion:cyclic mechanical stretch converts mechanical signals into biochemical signals through the pressure receptor IGF1R and activates the ERK1/2 signaling pathway to promote chondrocyte proliferation and extracellular matrix synthesis.