Porous calcium phosphates have been proposed as bone tissue engineering scaffolds due to their osteoconductive properties and widespread clinical use as synthetic bone graft. Recently, microporous calcium phosphates have been described that are capable of inducing osteogenic differentiation of stem cells and bone formation in ectopic sites. In this study, we investigated such an osteoinductive biphasic calcium phosphate (BCP1200) as a potential bone tissue engineering scaffold and compared this to two non-osteoinductive calcium phosphates (BCP1300 and HA60).
Bone marrow derived mesenchymal progenitor cells were isolated from the Os Ilium of goats, expanded and seeded onto all three types of porous calcium phosphate in a concentration of 8.16 million cells per cc scaffold. After implanting the tissue engineered implants and control samples in the dorsal muscle of goats for twelve weeks, histology and histomorphometry was performed to evaluate the amount of newly formed bone in the available pore area.
Control samples of the osteoinductive biphasic calcium phosphate showed a limited amount of newly formed bone tissue in the inner pores (0.9 +/- 1.1%), confirming its osteoinductive properties. None of the control BCP1300 or HA60 samples showed any bone formation, while the tissue engineered samples of these materials only occasionally revealed some bone formation. On the other hand, the tissue engineered and osteoinductive BCP1200 samples showed many areas of bone formation. At twelve weeks, bone was still actively being formed as indicated by the presence of seams of cuboidal osteoblasts and osteoid, and filled 15.9 +/- 5% of the available pore area. These results indicate that the osteoinductive biphasic calcium phosphate BCP1200 is a superior bone tissue engineering scaffold as compared to the non-osteoinductive calcium phosphates HA60 and BCP1300, by retaining or inducing an osteogenic phenotype of seeded mesenchymal progenitor cells.