Autologous mesenchymal stem cells loaded in Gelfoam® for structural bone allograft healing in rabbits

This study was designed to evaluate the effect of autologous bone marrow mesenchymal stem cells (MSCs) seeded into Gelfoam® on structural bone allograft healing. Thirty New Zealand white rabbits were divided into two groups. Segmental bone defect was created on diaphysis of the femur, and the defect was reconstructed with structural bone allograft. In experimental group, structural allograft was wrapped around by Gelfoam® containing autologous MSCs, whereas cells were not included in control group. At 4, 8, 12 weeks, the femur of rabbits underwent radiographic and histologic evaluation for bony union. Bone morphogenic protein-2 (BMP-2), BMP-4, BMP- 7, vascular endothelial growth factor (VEGF), and receptor activator of nuclear factor-kappa B ligand (RANKL) were measured within the grafted periosteal tissue. Bony union was not achieved in both groups at 4 and 8 weeks. At 12 weeks, three out of five femurs in experimental group were united, but one out of five in control group was united. Mean Taira scores were significantly different between two groups. The expression of BMP-2 was significantly higher at 4, 8 weeks, the expressions of BMP-4 and BMP-7 were significantly higher at 8 and 12 weeks, and the expression of VEGF and RANKL were significantly higher at all time points in experimental group. Incorporation of the structural bone allograft could be enhanced if allograft is covered with Gelfoam® containing autologous MSCs. MSCs have influence on not only bone formation, but neo-angiogenesis, and bone resorption.