Role of autologous rabbit adipose-derived stem cells in the early phases of the repairing process of critical bone defects

Adipose-derived stem cells (ASCs) may represent a novel and efficient tool to promote bone regeneration. In this study, rabbit ASCs were expanded in culture and used for the regeneration of full-thickness bone defects in the proximal epiphysis of tibia of 12 New Zealand rabbits. Defects were implanted with graft material as follows: untreated (control), empty hydroxyapatite (HA) disk, ASCs alone, and HA disk seeded with ASCs. Each isolated ASCs population was tested in vitro: they all showed a high proliferation rate, a marked clonogenic ability, and osteogenic differentiation potential. Eight weeks after implantation, macroscopic analyses of all the samples showed satisfactory filling of the lesions without any significant differences in term of stiffness between groups treated with or without cells (p > 0.05). In both the scaffold-treated groups, a good osteointegration was radiographically observed. Even if HA was not completely reabsorbed, ASCs-loaded HA displayed a higher scaffold resorption than the unloaded ones. Histological analyses showed that the osteogenic abilities of the scaffold-treated defects was greater than those of scaffold-free samples, and in particular new formed bone was more mature and more similar to native bone in presence of ASCs. These results demonstrated that autologous ASCs-HA constructs is a potential treatment for the regeneration of bone defects.