Nano-hydroxyapatite Particles Participate In The Mechanism Of Bone Regeneration By Affecting The Function Of Endothelial Cells

Background&Objective:Due to its biocompatibility and bone regeneration ability,HAP has been applied to the fields of biomedical regeneration.However,the poor mechanical strength and low biological degradation rate of HAP greatly limited its clinical application.Compared with the large size of HAP particles,the mechanical and biological properties of nano-HAP have been improved significantly,is a more promising bone regeneration material.The regeneration of bone defects is a complex process,which also includes the reconstruction of blood vessels.The effect of bone implant on vascularization is an important factor in determining the effect of bone repair.Endothelial cells(ECs)are essential structures for all types of blood vessels.Therefore,exploring the effect of nano-HAP on the biological behavior of ECs will help us to understand the mechanism of bone regeneration in a deeper way.We chose endothelial cells as the objects of the study,revealing the effect of nano-HAP on the endothelial cells,and explored the mechanism of its possible involvement in bone regeneration by affecting vascular remodeling.Methods:Three different sizes of HAP particles(20nm,80nm,and 12μm)were selected to interact with human umbilical vein endothelial cells(HUVECs)in vivo.The materials were observed by transmission electron microscopy,laser confocal scanning microscopy,x-ray diffractometer and Fourier transform infrared spectroscopy.The effects of HAP on endothelial cell viability,migration,vascular function,and ability of creating NO and VEGF were observed by co-culture of HAP and human umbilical vein endothelial cells(HUVECs)in vitro.Western blot was used to detect the effect of HAP on PI3K/Akt pathway protein(Akt,p-Akt,eNOS,p-eNOS).The effect of HAP on endothelial cell viability and NO production was detected by IGF-1 pretreatment.Result:X-ray diffraction shows that the three kinds of HAP particles are pure hexagonal crystals,Fourier transform infrared spectroscopy shows that they have PO43-at the peak.Both np20 and np80 reduced the migration ability of HUVECs,and m-HAP had no significant effect on the migration ability of HUVECs.Three kinds of HAP significantly inhibited the viability of HUVECs,the amount of NO production and the ability of angiogenesis.The inhibitory effects were:np80>np20>m-HAP.Compared with the control group,np20 had a slight effect on VEGF secretion,while np80 and m-HAP had no significant effect on it.Conclusions:HAP can inhibit the biological function of HUVECs through PI3K/Akt pathway,and inhibition strength:np80>np20>m-HAP,nano-HAP can not promote the regeneration of blood vessels and promote the osteogenesis by promoting blood vessel regeneration.