The role of new zinc incorporated monetite cements on osteogenic differentiation of human mesenchymal stem cells.

ß-Tricalcium phosphate particles were sintered in the presence of different amounts (0-0.72mol) of zinc oxide (ZnO) to prepare zinc doped ß-TCP (Znß-TCP) particles for further use in novel monetite (DCPA: CaHPO4) zinc incorporated bone cements with osteogenic differentiation potential towards human mesenchymal stem cells (hMSCs). XRD analysis of zinc incorporated cements prepared with ß-TCP reagent particles doped with different amount of ZnO (i.e. 0.03, 0.09 and 0.18mol ZnO) revealed the presence of unreacted Znß-TCP and monetite. Furthermore, it was shown that zinc ions preferentially occupied the ß-TCP crystal lattice rather than the monetite one. Release experiments indicated a burst release of ions from the different fabricated cements during the first 24h of immersion with zinc concentrations ranging between 85 and 100% of the total concentration released over a period of 21days. Cell proliferation significantly increased (P<0.05) on zinc incorporated monetite respect to control samples (Zinc-free cement) at 7 and 14days post seeding. The expression of Runx-2 was significantly up regulated (P<0.05) in the case of cells seeded on monetite prepared with ß-TCP doped with 0.03 moles of ZnO. On the other hand, the cell mineralization as well as the expression of osteogenic marker genes ALP and OSC decreased significantly (P<0.05) at 14days post cell seeding. In conclusion, these results suggest that the zinc ions released from the cements during the first 24h of culture played a critical role in regulating the osteogenic differentiation of hMSCs.