Effect of ion-incorporated porous calcium metaphosphate on osteoblastic differentiation of human mesenchymal stem cells

Calcium metaphosphate(CMP) is proposed as a bone substitute. We previously have shown that CMP has favorable biocompatibility and ability to stimulate osteoblastic differentiation of human bone marrow stromal cells(hBMSCs). In the present study, we investigate the effects of K or Na ion incorporated CMP block's biodegrad-ability, cytotoxicity, adhesion, osteogenicity and suitable pore size. A Pure CMP block and CMP blocks containing either 5 mol%(Na ₂O₅-CMP) or 5 mol% K₂O(K₅-CMP) with pore sizes of 300 or 600 μm were prepared. Porous K₅-CMP blocks incubated in a simulated body fluid(SBF) for 1, 7, and 21 days showed significant weight reduction compared to the pure and Na₅-CMP blocks. The ion-incorporated CMP blocks did not show cytotoxic response to hBMSCs. Osteoblastic differentiation of hBMSCs in vitro measured by RT-PCR, alkaline phosphatase(ALP) and von Kossa staining revealed that there were no differences among them. However, porous CMP blocks with 300 μm pores retained more von Kossa-positive colonies, compared to those with 600 μm. According to these results, bio-degradability of CMP could be controlled by addition of K ₂O retaining biocompatibility, and the CMP blocks with 300 μm size pores can retain cell adhesion effectively and support osteoblastic differentiation in vitro.