Study On The Effect Of Endothelial Progenitor Cell Derived Microvesicles With MiR-126 Overexpression On Accelerating Treatment Of Osteoporotic Fracture

[Objective]Macrovesicles(MV)can modulate the function of recipient cells by transferring their contents.Previous evidence indicates that endothelial progenitor cells(EPCs)-derived MVs promote bone healing through stimulating NE angiogenesis.In this study,we evaluated whether EPC-MVs could promote bone regeneration by directly regulating osteoblast.We evaluated whether EPC-MVs and EPC-MVs-mi126 can promote osteoporosis-induced fracture healing in vivo,and to study possible mechanism.[Methods](1)The proliferation,migration,apoptosis and differentiation abilities of pre-osteoblast cells MC3T3-E1 were analyzed in the presence or absence of EPC-MVs.Western blot was used for analyzing the protein of Erk1/2,Bcl-2 and PARP.Erk1/2 inhibitor was used for pathway verification.The role of mi R126-containing MVs in mediating these effects was also explored.(2)The ovariectomized rat with osteoporosis-induced fracture model was established.The EPC-MVs and EPC-MVs-mi126 were transplanted respectively into the marrow cavity of the fracture thighbone of the rats.BMD was measured by dual-energy X-ray digital bone density meter.Micro-CT was used to detect microarchitecture of the femur.The right femurs were collected for determining the biomechanical quality of the diaphysis using 858 Mini Bionix Ⅱ material testing machine.Peri Cam PSI was used for hemodynamic studies.The serum PINP,OC,BALP were detected by ELISA.[Results]Results showed :(1)EPC-MVs were able to promote MC3T3-E1 cell proliferation and migration,while inhibit apoptosis.(2)EPC-MVs have no influence on MC3T3-E1 cell osteogenic differentiation.(3)The effects were accompanied with the up-regulation of p-Erk1/2,Bcl-2 and its down-regulation of PARP,which were abolished by Erk1/2 inhibtor.(4)Mi R126-containing MVs can promote the effects of EPC-MVs.(5)The effect of MVs on ECs was accompanied by the up-regulation of PI3 K and p-Akt,which could be partially eliminated by PI3 K inhibitors.(6)Ovariectomy can reduce bone mineral density in rats.(7)EPC-MVs could change the bone microstructure parameters,increase the BV/TV,Tb.N,Tb.Th,BMC,BMD,decrease the Tb.Sp,SMI.The effect of EPC-MVs-mi126 is the same trend,and its effect is more obvious.(8)EPCMVs could change the biomechanical indexes of femur in rats.The parameters of structural mechanics and material mechanics were increased.The effect of EPC-MVs-mi126 was more obvious.(9)EPC-MVs can increase the blood flow and increase the recovery rate of blood perfusion in fracture of rats.EPC-MVs-mi126 can play a better role.(10)EPC-MVs could increase the PINP,OC and BALP in rats.The effect of EPC-MVs-mi126 was more obvious.[Conclusion](1)Our data indicate that EPC-MVs promote proliferation and migration of MC3T3-E1 cell while reduced apoptosis via Erk1/2-Bcl-2 pathway.Meanwhile,mi R126 overexpression exhibited a more significant enhancement effect.(2)The ovariectomized rat with osteoporosis-induced fracture model was established.Treatment of fracture with EPC-MVs and EPC-MVs-mi126 could change the index of bone regeneration.Bone quality and biomechanical properties were improved.The blood flow and the recovery rate of blood perfusion in fracture of rats were increased.Fracture repair was strengthened.