Characterization of Adult Progenitor Cells and their Fate in a Rat Femur Fracture Model

This study was carried out to characterize two progenitor cell populations in the context of orthopaedics and to examining their fate in a rat bone defect model. Endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs) isolated from syngeneic bone marrow were characterized utilizing flow cytometry and osteogenic/angiogenic differentiation assays in vitro. To assess in vivo fate, genetically labeled cells were implanted into a defect and examined at two and four weeks post-implantation. Fluorescent microangiography (FMA) was used to model nascent vasculature two weeks post-implantation. The results show populations that resemble established definitions. In vitro, EPCs demonstrated a similar osteogenic capacity to MSCs and superior angiogenic capacity on the basis of tube formation. In vivo experiments showed presence of cells at the fracture site at 2 and 4 weeks. EPCs showed a trend towards increased vessel formation with FMA. These results provide groundwork for future investigation into mechanisms of healing.M.Sc