Endothelial Progenitor Cells for Fracture Healing: A Microcomputed Tomography and Biomechanical Analysis

Abstract

Local treatment of segmental bone defects with ex vivo expanded endothelial progenitor cells (EPCs) has been shown to increase osteogenesis and callus formation in rat femur diaphyseal defects. The purpose of this study was to evaluate the effects of local EPC therapy on the microarchitecture and biomechanical properties of a segmental bone defect in a rat model. Five-millimeter segmental defects were created in the femora of 14 Fisher 344 rats and stabilized with miniplates. The treatment group (n = 7) received 1 × 10(6) EPCs, seeded on a Gelfoam scaffold, locally at the site of the bone defect, and control animals (n = 7) received Gelfoam and saline only. Animals were euthanized 10 weeks after the procedure and new bone formation was assessed with radiographs, microcomputed tomography and biomechanical testing. Radiographically, all the animals in the EPC-treated group healed with bridging callus formation, whereas animals in the control group developed nonunion of the defect. Microcomputed tomography assessment demonstrated significantly superior bone formation in the EPC-treated group versus the control group for all parameters tested (P = 0.013-0.000). Biomechanical testing revealed that the EPC-treated group had significantly higher torsional strength (P = 0.000) and stiffness (P = 0.000) when compared with the control group. The results of this study suggest that local EPC therapy significantly enhances fracture healing in a segmental defect model in a rat femur. EPC therapy results in superior radiographic bone formation and healing when compared with appropriate controls.