Critical bone defect repair by autologous rabbit adipose-derived stem cells (ASCS) loaded onto hydroxyapatite scaffold

One of the most important issues in orthopaedic surgery is the loss of bone resulting from trauma, infections, tumors or congenital deficiencies. Nowadays, for the treatment of bone diseases a valid approach is the use of autologous cells able, alone or in combination with osteoconductive scaffold, to enhance the regeneration process of bone defect. Adipose-derived stem cells (ASCs), with their great availability and osteogenic potential may represent, in association with specific supports, a novel and efficient approach for bone regeneration. In this study, autologous rabbit ASCs were used for the treatment of a full-thickness bone defects in the proximal epiphysis of tibia of twelve New Zealand rabbits as follows: sham (just defect), insertion of hydroxyapatite disk (HA), of ASCs alone (ASCs), and of hydroxyapatite-ASCs seeded-disk (HA-ASCs). Each ASCs population was tested in vitro: all of them show a high proliferation rate with a doubling time of 56.5±16.9 hours, a marked clonogenic ability (3.0±1.6%) and osteogenic differentiation potential evaluated by extracellular calcified matrix deposition (161.6±77.9% increase of osteo- vs undifferentiated ASCs). Eight-weeks after surgery, the macroscopic analyses show satisfactory filling of the lesion 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 more efficient scaffold resorption than the unloaded ones. Furthermore, histological analyses show the osteogenic abilities of the scaffold-treated defects with respect to the scaffold cell-free samples, and in particular, the new formed bone was more mature and similar to native bone in presence of ASCs. These results indicate that autologous ASCs-hydroxyapatite construct is a potential treatment for the regeneration of bone defects.