Bone regeneration potential of allogeneic or autogeneic mesenchymal stem cells loaded onto cancellous bone granules in a rabbit radial defect model.

For developing a clinically effective bone regeneration strategy, we compare the bone regeneration potential of cultured allogeneic bone marrow-derived mesenchymal stem cells (BM-MSCs) and of autologous BM-MSCs loaded onto allogeneic cancellous bone granule scaffolds. A critical-sized segmental bone defect was made at the mid-shaft of both radiuses in 19 New Zealand White rabbits (NWRs). In the experimental group, allogeneic BM-MSCs loaded onto small-sized allogeneic cancellous bone granules (300~700 um in diameter) were implanted in one side of a bone defect. In the control group, autologous BM-MSCs loaded onto allogeneic cancellous granules were grafted in the other side. Bone regeneration was assessed by radiographic evaluation at 4, 8, 12 and 16 weeks post-implantation and by micro-computed tomography (micro-CT) and histological evaluation at 8 and 16 weeks. The experimental groups showed lower bone quantity indices (BQIs) than the control groups at 12 and 16 weeks (p < 0.05), although no significant difference was observed at 4 and 8 weeks (p > 0.05). Micro-CT analysis revealed that both groups had similar mean total bone volume and other parameters including trabecular thickness, number and separation at either 8 or 16 weeks. Only bone surface area revealed less area in the experimental group at 16 weeks. Histological evaluation of 8-week and 16-week specimens showed similar biologic processes of new bone formation and maturation. There was no inflammatory reaction indicating an adverse immune response in both allogeneic and autologous MSC groups. In conclusion, allogeneic BM-MSCs loaded onto allogeneic cancellous bone granules had comparable bone regeneration potential to autologous BM-MSCs in a rabbit radial defect model.