Method: To study their in vitro-behaviour, hADSCs were plated (104cells/cm2) with 450µm large coral particles (2.5mg/cm2). The cells were cultured either in plain medium (control) or in medium supplemented with vitC, b-glycerophosphate, and dexamethasone (osteogenic). DNA proliferation assays and quantification of alkaline phosphatase activity were performed according to established methods. To study their osteogenic potential, hADSCs were loaded on 3mm coral cubes (3.105 cells/cube) and cultured for 7 days in either control or osteogenic media. Then, the constructs were subcutaneously implanted in 6 week-old NMRI-nu/nu male mice. Non-demineralised histological analysis was performed.
Result: n vitro, compared to cells cultured in control media, hADSCs cultured in osteogenic media showed increased alkaline phosphatase activity from day21 and formed mineral from day21 to day28. Coral particles and glass micro beads (used as control) didn't interfere with hADSCs' osteoblastic differentiation. In vivo, after a 46-day-implantation, all hADSC-coral constructs implanted were fully cell-colonized. Constructs with differentiated cells showed coral surface dissolution, rich vascularization and collagen-rich extra-cellular matrix, whereas constructs with undifferentiated cells showed increased coral resorption. None of the constructs showed new bone formation.
Conclusion: This preliminary study shows that the association with coral doesn't modify hADSCs' behaviour in vitro and that hADSCs' state of differentiation affects coral dissolution in vivo. The optimal on-scaffold culture conditions (seeding density, loading techniques, differentiation state) and cell-survival after implantation need to be further investigated.