The Recruitment Of Mesenchymal Stem Cells To The Fracture Site In Fracture Healing With The Expression Of The Related Factor

Objective The use of stem cells and cytokines to repair injured tissues after fracture is intensively studied by orthopecic researchers in recent years.To make this fracture heal, there must be plenty of stem cells homing into the fracture region first,then staying for an enough long time.However,there have been less viewpoints about how stem cells home after fracture in different studies at present,and the mechanism underlying it is even more poorly understood.In this study, we are going to establish a rat model of right femur fracture,and analyze how the related factor expression level would change at different time after fracture,then compare the results with the left femur control.So as to observe the recruiment of stem cells to the fracture site in fracture healing and explore the expression of the related factor.Methods In the first part, rats MSCs were isolated and expanded from bone marrow cells by adhering to the culture plastic, and identified with cell morphology, and the phenotypes were assessed by flow cytometry. Then the MSCs were labled by PKH-26.In the second part,24 rats were randomly divided A,B and C group,and then they were made models of right femur fracture and the left femur control. Then transplanted MSCs labled by PKH-26 into rat femoral fracture model, observing MSCs changes in vivo.The rats of A,B and C group were sacrificed respectively at 3,7and 14 days after transplantation of MSCs and then the labled MSCs of A,B and C group in the fracture site are detected respectively by fluorescence imaging.At the end of the experiment, the specimens of fracture were exposed, fixed, decalcified, wrapped and cut into slices.We use confocal laser scanning microscope and immuno-histochemical method to observe migration and distribution of MSCs and explore the expression of the related factor in different times.Results Uniform spindle-shaped in appearance and showed active proliferative capacity.The number of marked MSCs of A group in fracture sites was more than those in nomal femur by fluorescence imaging.And the number of marked MSCs of B and C group in fracture sites was more obviously than those in nomal femur by fluorescence imaging and more than A group in fracture sites.The number of SDF-1 a protein in fracture sites were more than the control in A group. And the number of SDF-1 a protein in fracture sites were more obviously than the control in B and C group.Conclusions SDF-1 is induced in fracture sites and promotes the homing of mesenchymal stem cells to the site of injury in the early stage of fracture healing.