Introduction and Aims: Adipose-derived stem cells (ADSCs) are capable of osteogenic differentiation under appropriate conditions in vitro (1). In this study we demonstrate the differences and similarities of the healing potential of ADSCs against the bone marrow-derived stem cell population (BMSCs) in the critical size ovine cancellous defect model, healed with culture expanded autologous stem cells from adipose tissue (ADSCs).

Method: Bone marrow aspirates and subcutaneous adipose tissue were harvested from 42 adult wethers. The population of stromal cells was derived from both tissues. Populations of bone marrow cells and adipose stromal cells were expanded in culture and stimulated with osteogenic medium for seven days. Cultured cell populations were harvested, mixed with a hydroxy-apatite carrier (Pro-Osteon 200R) and deposited into bilateral medial femoral condyle confined cancellous defect. Seven groups were examined: Bone graft+ ADSCs, Bone graft+ BMSCs, Carrier + ADSCs, Carrier+ BMSCs, Bone graft, Carrier, Empty defect. Two week, four week and eight week time-points were examined.

Results: All specimens were decalcified and five μm histological slides were stained using H& E and Masson’s Trichrome. Histomorphometry analysis on Masson’s Trichrome stained slides was performed using colour threshold-based software Bioquant Nova 6.50.10. Immunohistochemical staining for BMP4 and BMP7 and their downstream regulators: Smad4 and CBFA1 were evaluated in the defect area and graded in a blind fashion by two trained observers. There was a progressive and time-dependent increase in woven bone formation in the defects treated with ADSCs across all time points. The amount of bone formed in this group was comparable with the amount formed by the use of BMSCs.

Conclusion: The results of this study support the hypothesis that seeding porous hydroxyappatite with ADSCs does enhance bone formation and defect healing.