The Effects Of Strontium On The Expression Of VEGF And Notch Signaling Pathway In Osteogenic Differentiation Of Adipose-derived Stem Cells

Objective:The development of bone tissue engineering technology has provided a new way for clinical repair of bone defects.Adipose-derived stem cells(ADSCs)have attracted the attention of scholars gradually for their advantages of being easily obtained,rapid proliferation and multiple differentiation potential.However,it is not ideal to use tissue-engineered bone to repair bone defect in clinic.Studies have shown that the insufficient blood supply is one of the reason for local osteonecrosis.Vascular endothelial growth factor(VEGF)is not only an important growth factor for regulating proliferation and angiogenesis of endothelial cells,but also affects the development and repair of bone tissue.Studies have shown that strontium(Sr)can increase the expression level of VEGF in osteogenic induced ADSCs,and promote angiogenesis during bone repair process.In this study,we further studied the rising expression level of VEGF in osteogenic differentiation of strontium stimulated ADSCs.We used strontium chloride,Notch signaling pathway inhibitor :γ-secretase inhibitors(DAPT)and both of them to treat osteongenic induced ADSCs..By comparing the expression level of Notch signaling related protein:Notch intracellular domain(NICD)and VEGF protein among each group,we investigated the relationship between VEGF and Notch signaling pathway in the course of ADSCs’ osteogenic differentiation with strontium stimulating.Methods: 1、Extraction,cultivation and identification ADSCs in vitro.2、Culture P3 ADSCs in osteogenic induction cultural medium for osteogenic differentiation.3、Set a control group and extract intracellular protein with the intervention of strontium chloride、Notch signaling inhibitor DAPT and both of them respectively for 6 days.4、The protein expression of Notch signaling protein NICD and VEGF in pretreated ADSCs of each group was detected by Western Blot method.Results: 1.Compared with the expression level of NICD(0.6715±0.0505)in control group,the expression level of NICD increased significantly(P<0.01)in Sr group(1.1877±0.0892)and decreased significantly(P < 0.01)in DAPT group(0.3483±0.0262).With the treatment of Sr and DAPT,the expression level of NICD (0.3867±0.0291)decreased significantly(P<0.001)than the expression level in Sr group.2.Compared with the expression level of VEGF(0.6889±0.0394)in control group,the expression level of VEGF increased significantly(P<0.001)in Sr group(1.3200±0.0755)and decreased significantly(P < 0.01)in DAPT group(0.4656±0.0266).With the treatment of Sr and DAPT,the expression level of VEGF(1.0575±0.0605)decreased significantly(P<0.01)than the expression level in Sr group.Conclusion: Strontium can upregulate the expression level of VEGF in osteogenic induced ADSCs.Notch signaling pathway was activated during the strontium induced osteogenic differentiation of ADSCs,and plays a positive role in regulating VEGF expression.