Construction Of SP Peptide Nanofibrous Scaffolds And Its Preliminary Applications For Bone Repair

Background and Objective: Bone defects caused by trauma are quite common in clinical practice.Bone defect repair is still a major challenge clinically as the characteristics of poor repair potential and multiple complications.Currently,bone tissue engineering strategy has provided a promising approach for the repair of bone defects.However,the vascularization of a scaffold after its implantation is an unsolved challenge for bone defect repair at present.Endothelial progenitor cells(EPCs)are promising seeding cells in tissue engineering and regenerative medicine.EPCs in the ischemic and injury sites can enhance neovascularization and promote tissue repair.Whereas,the potential to promote vascularization and tissue repair of EPCs is limited due to their low homing capacity.Previous studies showed that neuropeptide substance P(SP)promotes angiogenesis by the mobilization of EPCs to the injury sites,which further enhance the repair of injury tissues.Here,the aim of this study is to construct SP peptide-modified electrospun nanofiber scaffold(PCL/PGC-SF-SP)and evaluate its effect on promoting fast vascularization and bone defect repair at the scaffold implantation sites.The three main contents and results of this study are listed as follows:①PCL/PGC(3:1)nanofibrous scaffolds were fabricated by electrospinning,followed by self-assembly and click chemistry techniques,which aim to develop the PCL/PGC-SF-SP scaffold.Results from Laser scanning confocal microscopy(LSCM)and X-ray photoelectron spectroscopy(XPS)showed that SP peptides were immobilized to the surface of PCL/PGC scaffolds successfully.Deposition of SF and immobilizationSP peptide onto PCL fibers has not obvious change in tensile strength.②The characterization and EPCs biocompatibility of the nanoscaffold were evaluated.The results from field emission scanning electron microscopy(FESEM)showed that the nanoscaffold had fiber structure and the main structure of nanoscaffold was not changed obviously after the immobilization of SP peptide to the surface of PCL/PGC scaffolds;Contact angle test results show that SP peptide is hydrophobic,but PCL/PGC-SF-SP nanoscaffold has good hydrophilicity because of silk fibroin(SF)better hydrophilicity;PCL/PGC-SF-SP nanoscaffold was found to encourage EPCs proliferation and cell adhesion;Results from the Transwell migration assay demonstrated that PCL/PGC-SF-SP nanofibers significantly induced EPCs migration;Furthermore,enhanced tube formation by EPCs was observed on Matrigel in the presence of PCL/PGC-SF-SP nanofibers;The results of alizalin red staining showed that osteigenic differentiation of MSCs wre significantly promoted by PCL/PGC-SF-SP nanofibers.②The abilities to promote in situ vascularization and bone regeneration of critical-size cranial defects model of SD rats by the PCL/PGC-SF-SP nanoscaffold.Results from immunofluorescence staining showed homing and fast vascularization of EPCs was significantly promoted;In addition,PCL/PGC-SF-SP scaffolds were found to significantly improve the repair of rats’ cranial defects at 8 weeks after surgery;H&E staining assays confirmed the accelerated vascularization and bone formation after 8 weeks of implantation and revealed contribution of the fast vascularization to bone regeneration.Conclusion: The PCL/PGC-SF-SP nanofibrous scaffolds constructed by electrospinning,self-assembly and “click chemistry” techniques promote vascularization of bone defect areas and accelerate the repair of bone defect.The strategy of vascularized scaffold construction has a potential to provide guidance for resolving the technical problems of scaffolds vascularization and bone defect repair in clinic.