Human adipose-derived mesenchymal stem cells toevaluate the biologicaò èerformances of ion-doped sintered hydrylapatite scaffolds

Tissue engineering (TE) aims to repair/regenerate tissues damaged by injuries or diseases. Biomaterials play a key role in these strategies, where they serve as a substrate for the incorporation and release of ions. The Mg2+, Sr2+ and Zn2+ ions are active regulators of the proliferation and differentiation of osteoblasts and osteoclasts, thus modulating bone turnover. Specifically, Mg2+ has attracted the attention of the scientific community in the field of TE. In the present work, an in vitro model of human adipose‐derived mesenchymal stem cells (hASCs) was used to evaluate the cytocompatibility and osteoinductivity properties of four different sets of ion‐doped sintered hydroxylapatite (S‐HA) powders. The set includes S‐HA doped with Mg2+, Sr2+ and Zn2+ ions (coded as S‐MgHA, S‐MgSrHA, S‐MgZnHA, respectively) and non‐doped S‐HA, as reference material. Live/Dead dye was carried out to evaluate the percentage of living cells. The cellular metabolic activity and the cytoskeleton organisation were investigated by AlamarBlue® metabolic assay and Phalloidin‐TRITC immunostaining, respectively. In order to evaluate the expression of genes involved in osteogenic differentiation, a Real‐Time PCR Array was performed. The Osteocalcin and Osteopontin proteins expression was assessed by performing ELISA. The cytoskeleton architecture of hASCs grown in contact with the scaffolds seems to be well organised, whereas its integrity remained uninfluenced by the scaffolds over time. Live/Dead staining and metabolic activity of hASCs grown on ion‐doped materials was increased during the experiments, up to day 14. Osteogenic genes, such as BMP1 and SP7 transcription factor, were expressed on hASCs grown on different ion‐doped materials with different fold‐changes. Our experiments suggest that multiple‐ion doping scaffolds seem to maintain a positive modulation of hASC osteogenic differentiation, compared to the control. The present work suggests that the exploration of different doping agents for scaffolds can yield new sintered materials with optimised biologic performances.