Early vascularization induced by EPC in a critical bone defect enhances bone healing after eights weeks in rats

Introduction: Early vascularization of bone defects is a prerequisite for ingrowth of osteogenic reparative cells to regenerate bone in vivo. The size of the bone defect may limit the ingrowth of bone forming cells, since lack of vessels does not ensure a sufficient nutritional support of the bone graft. Endothelial progenitor cells (EPC) participate in neovascularization, thus playing an important role in the process of vascular repair (1,2,3,4). These cells may provide a powerful cellular therapeutic strategy for vascularization of a bone matrix. This investigation tested the ability of human early endothelial progenitor cells (EPC, 5) in coculture with mesenchymal stem cells (MSC) seeded on suitable scaffold (β-tricalcium phosphate (β-TCP)) and placed into a critical-sized segmental defect in the femur of adult athymic rats. We hypothesized that coculture of EPC and MSC improve the vascularization and therefore accelerate the bone healing process of large bone defects in vivo.