Tissue-engineered bone formation using human bone marrow stromal cells and novel beta-tricalcium phosphate.

In this study we investigated not only the cellular proliferation and osteogenic differentiation of human bone marrow stromal cells (hBMSCs) on the novel beta-tricalcium phosphate (beta-TCP) scaffolds in vitro but also bone formation by ectopic implantation in athymic mice in vivo. The interconnected porous beta-TCP scaffolds with pores of 300-500 microm in size were prepared by the polymeric sponge method. beta-TCP scaffolds with the dimension of 3 mm x 3 mm x 3 mm were combined with hBMSCs, and incubated with (+) or without (-) osteogenic medium in vitro. Cell proliferation and osteogenic differentiation on the scaffolds were evaluated by scanning electron microscopy (SEM) observation, MTT assay, alkaline phosphatase (ALP) activity and osteocalcin (OCN) content measurement. SEM observation showed that hBMSCs attached well on the scaffolds and proliferated rapidly. No significant difference in the MTT assay could be detected between the two groups, but the ALP activity and OCN content of scaffolds (+) were much higher than those of the scaffolds (-) (p < 0.05). These results indicated that the novel porous beta-TCP scaffolds can support the proliferation and subsequent osteogenic differentiation of hBMSCs in vitro. After being cultured in vitro for 14 days, the scaffolds (+) and (-) were implanted into subcutaneous sites of athymic mice. In beta-TCP scaffolds (+), woven bone formed after 4 weeks of implantation and osteogenesis progressed with time. Furthermore, tissue-engineered bone could be found at 8 weeks, and remodeled lamellar bone was also observed at 12 weeks. However, no bone formation could be found in beta-TCP scaffolds (-) at each time point checked. The above findings illustrate that the novel porous beta-TCP scaffolds developed in this work have prominent osteoconductive activity and the potential for applications in bone tissue engineering.