Abstract
Tissue engineering bones take great advantages in massive bone defect repairing; under the induction of growth factors, seed cells differentiate into osteoblasts, and the scaffold materials gradually degrade and are replaced with neogenetic bones, which simulates the actual pathophysiological process of bone regeneration. However, mechanism research is required and further developed to instruct elements selection and optimization. In the present study, we prepared vascular endothelial growth factor/bone morphogenetic protein-2- nanohydroxyapatite/collagen (VEGF/ BMP-2- nHAC/ PLGAs) scaffolds and inoculated mouse MC3T3-E1 preosteoblasts to detect osteogenic indexes and activation of related signaling pathways. The hypothesis is to create a three-dimensional environment that simulates bone defect repairing, and p38 mitogen-activated kinase (p38) inhibitor was applied and osterix shRNA was transferred into mouse MC3T3-E1 preosteoblasts to further investigate the molecular mechanism of crosstalk between BMP-2 and VEGF. Our results demonstrated the following: (1) BMP-2 and VEGF were sustainably released from PLGAs microspheres. (2) nHAC/PLGAs scaffold occupied a three-dimensional porous structure and has excellent physical properties. (3) MC3T3-E1 cells proliferated and differentiated well in the scaffold. (4) Osteogenic differentiation related factors expression of VEGF/BMP-2 loaded scaffold was obviously higher than that of other groups; p38 inhibitor SB203580 decreased the nucleus/cytoplasm ratio of osterix expression. To conclude, the active artificial bone we prepared could provide a favorable growth space for MC3T3-E1 cells, and osteogenesis and maturation reinforced by simultaneous VEGF and BMP-2 treatment may be mainly through the activation of the p38 MAPK pathway to promote nuclear translocation of osterix protein.
Highlights
Bone defect repair is a complex process involving several cell types as osteoblasts, endothelial cells, and so on, besides various growth factors [1]
Among the few BMP products approved by Food and Drug Administration (FDA) for clinical use, recombinant human bone morphogenetic protein-2 possesses potent osteogenic ability, which can induce bone and cartilage formation both in vivo and in vitro [9, 10]
Physical Properties of nHAC/PLGAs Scaffold. nHAC/ PLGAs scaffold displayed a cylindrical shape with a diameter of 0.8cm and height of 0.8cm, being milky white and rough and having a foamy surface (Figure 1(a))
Summary
Bone defect repair is a complex process involving several cell types as osteoblasts, endothelial cells, and so on, besides various growth factors [1]. Delivery of cells and growth factors towards the defect and preservation of their activity has already been proven to be the crux of the resolution [2, 3]. Tissue engineering has great advantages, cultivating seed cells in a natural or synthetic, biocompatible and degradable scaffold, constructing active artificial bones under the induction of growth factors. After being implanted into bone defect cavity, new bones gradually generate with the degradation of scaffold material, which can meet reconstructive objectives [4, 5]. Combination of nHA and collagen is expected to break through the physicchemical defects of the two materials and meet the requirements of ideal artificial bone scaffold [8]. It is reported that BMP-2 interacts with VEGF during bone
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