Effect of canine cortical bone demineralization on osteogenic differentiation of adipose-derived mesenchymal stromal cells

Demineralized bone allografts and mesenchymal stromal cells have been used to promote bone regeneration. However, the degree to which cortical bone should be demineralized for use in combination with adipose-derived mesenchymal stromal cells (Ad-MSCs) remains to be clarified. In this study, the in vitro osteogenic ability of Ad-MSCs on allografts was investigated in relation to the extent of demineralization. Three treatment groups were established by varying exposure time to 0.6 N HCL: partially demineralized (PDB; 12 h), fully demineralized (FDB; 48 h), and non-demineralized bone (NDB; 0 h, as a control). Allografts were prepared as discs 6 mm in diameter for in vitro evaluation, and their demineralization and structure were evaluated by micro-computed tomography and scanning electron microscopy. Ad-MSC adhesion and proliferation were measured by MTS assay, and osteogenesis-related gene expression was assessed by quantitative reverse transcription polymerase chain reaction. PDB and FDB demineralization rates were 57.13 and 92.30%, respectively. Moreover, Ad-MSC adhesion rates on NDB, PDB, and FDB were 53.41, 60.65, and 61.32%, respectively. Proliferation of these cells on FDB increased significantly after 2 days of culture compared to the other groups (P < 0.05). Furthermore, expression of the osteogenic genes ALP, BMP-7, and TGF-β in the FDB group on culture day 3 was significantly elevated in comparison to the other treatments. Given its biocompatibility and promotion of the osteogenic differentiation of Ad-MSCs, our results suggest that FDB may be a suitable scaffold for use in the repair of bone defects.