The Effects Of Cell Surface Modifaction And Scaffold Topology On The Behaviour Of Mesenchymal Stem Cells

Tissue engineering and regenerative medicine research is aimed to take full advantages of the potential of cells in the repair of tissue damages by employing the interactions between cells,biomaterials scaffold and biological cues.Cell homing-based tissue engineering strategy is efficient in the repair of non-critical-sized defects,but not applicable for critical-sized defects.A few mesenchymal stem cells(BMSC)via intravenous infusion can successfully reach the damaged area.It is assume that the low efficiency in repaing large defects may be asscibed to the limited recruitment of cells into defect sites.Therefore,how to improve the migration of BMSC into defect sites and induce them into mature cells is the research focus.Cells secrete PDGF-BB conbined with PDGFR-beta on the surface of the BMSC,which can induce BMSC homing to the bone defect and participating in tissue repair in the fracture.Undesirably,the number of PDGFR-beta is decreasing with the passage number.As the homing efficiency of BMSC into bone marrow is co-related to the number of PDGFR-beta on the cell surface,it is assumed that it is promising to restore the homing efficiency of cells by increasing the numers of PDGFR-beta per cell.This project adopted the method of hydrophobi c interaction to modify the surface of BMSC.DMPE-PEG-maleimide can be functioned with cysteines of PDGFR-beta to form a complex.DMPE-PEG is a kind of phosphatide-polyethylene glycol(PEG)complex.DMPE is similar to the structure of liposome,it can ins ert inside the phospholipid bilayer of cell membrane.Thus,PDGFR-beta can combine with surface of BMSC to realize cell surface modification.We found the expression of MMP1 and MMP2 and phosphorylation of related proteins increase.This study layed the foundation for studying MSC migration to bone fracture after surface modification.Biological behaviour after BMSC homing,including adhesion,spreading,migration,infiltration,proliferation,differentiation which are related to cellular microenvironment directly.Scaffold is essential in large area defect repair and its interaction with cells greatly affects cell biology behavior.Electrostatic spinning technology is a kind of simple and economic way for the scaffold,including wound healing and tissue engineering applications.However,most of current understanding was mainly based on static observations of in vitro cell cultures for research on fiber diameter,fiber direction and material type,there is still limited understanding on the dynamics of stem cell–fibrous scaffold interactions and their role in deciding the fate of stem cells and scaffolds.Here,we employed microfibers(PLLA)and nanofibers(PCL/gelatin)to investigate the effects of fiber alignment on the behaviour of cell spreading,migration,differentiation,and scaffold remodelling.Cells were found to spread and migrate with increased velocity in the direction of aligned fibers as compared to random ones.Moreover,enhanced interactions between cells and aligned fibers were found to facilitate the infiltration of cells into the interior of fibrous constructs,which led to enhanced micro-integration and scaffold remodelling as well as more consistent behaviour of cell differentiation and extracellular matrix secretion as compared to random fibrous constructs.This study advances our understanding on the effects of fiber alignment on stem cell–fibrous scaffold interactions,and will facilitate the design of fibrous scaffolds with enhanced cell – matrix interactions for tissue engineering applications.This thesis focus on stem cells and scaffold metarial to discusse how surface mod ification and scaffold topography effect cell behaviors,layed a theoretical foundation for new strategy of tissue engineering that based on stem cell homing.