STUDIO DENSITOMETRICO NELLA VALUTAZIONE DEI PROCESSI RIPARATIVI SU LESIONI OSSEE 'CRITICAL SIZE' IN MODELLI ANIMALI

Adipose-derived stem cells (ASCs) may represent a novel and efficient tool to promote bone regeneration. Our purpose was to evaluate new-bone tissue formation using BMD (bone mineral densitometry), radiology and histology; in literature there aren’t normal values of bone mineral content in rabbit, goat and pig. Then, The first step of this study (preliminary phase) was to evaluate normal BMD value in rabbit skull and tibia and in pig and goat tibia. The second step (experimental phase), 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 BMD 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.