Endothelial Progenitor Cells Induces The Osteogenesis Of Bone Marrow Mesenchymal Stem Cells Via The Activation Of P38 MAPK Signaling Pathway

Objective: The defects of oral and maxillofacial bone tissue are often caused by trauma,tumor,infection and other factors.It is a difficult problem in clinical treatment to restore the bone tissue which defects cause the disorder of chewing,swallowing,breathing and speech.Bone tissue engineering is the most promising field for bone defect restoration.The principle is to use seed cells to implant bone replacement material into bone defect and promote bone defect repair under the action of growth factors.There are still some problems in bone tissue engineering such as slow osteogenesis and limited osteogenesis due to poor blood supply.Endothelial progenitor cells(EPCs)can generate blood vessels to enhance new bone vascularization.In our study,the angiogenic EPCs and bone marrow mesenchymal stem cells(BMSCs)were co-cultured and the osteogenic ability was enhanced.In this study,the mechanism of enhanced osteogenic capacity in co-culture of EPCs and BMSCs was investigated in order to improve the deficiency of bone defect treatment and better reconstruction of bone tissue.Material and methods: In this experiment,BMSCs and EPCs were co-cultured by Corning Transwell 3450 to establish a co-culture system of BMSCs and EPCs.BMSCs osteogenic gene expression and osteogenic protein synthesis were detected.Transcriptome whole gene sequencing was used to analyze the osteogenic pathways of BMSCs and to study the related pathways on the biological behaviors of BMSCs.Results:1 After the isolation and identification of endothelial progenitor cells and bone marrow mesenchymal stem cells,an experimental group co-cultured with two kinds of cells and a control group cultured with bone marrow mesenchymal stem cells were established.ALP staining showed that the activity of alkaline phosphatase in the co-culture group was higher than control group.The expressions of osteogenic related genes OPN,BSP and RUNX2 were up-regulated.2 Western blot results showed that p38 protein synthesis of MAPK signaling pathway increased while JNK and erk1/2 protein synthesis showed no significant changes.3 Si RNA was transfected into BMSCs to silence p38 gene.The results of Western blot showed that protein synthesis were down-regulated.The results of ALP staining and alizarin red staining showed alkaline phosphatase activity and formation of mineralized nodules were decreased.Conclusion: When endothelial progenitor cells were co-cultured with bone marrow mesenchymal stem cells,endothelial progenitor cells promoted bone formation of bone marrow mesenchymal stem cells through p38-mapk pathway.