Effects of low crystalline carbonate apatite on proliferation and osteoblastic differentiation of human bone marrow cells

Carbonated apatite (CO₃Ap) is the inorganic component of bone. We have proposed a new method for the fabrication of CO₃Ap blocks based on a dissolution-precipitation method using a synthetic precursor. The aim of this study is to examine the effects of low crystalline CO₃Ap on initial cell attachment, proliferation and osteoblastic differentiation of human bone marrow cells (hBMCs) using sintered hydroxyapatite and tissue culture plates as controls. Initial cell attachment and proliferation were assessed with a MTT assay. Expression of osteoblastic markers was examined by reverse transcription-polymerase chain reaction. XRD and FT-IR results showed formation of B-type carbonate apatite with lower crystallinity. No difference was observed for initial cell attachment between HAp and CO₃Ap discs. hBMSC attached more significantly on tissue culture plate than on HAp and CO₃Ap discs. The number of cells on HAp was higher than that on CO₃Ap until day 7, after which the number of cells was similar. hBMSC proliferated more significantly on tissue culture plate than on HAp and CO₃Ap discs. In contrast, hBMCs incubated on CO₃Ap demonstrated much higher expression of osteoblastic markers of differentiation, such as type I collagen, alkaline phosphatase, osteopontin and osteocalcin, than hBMCs on HAp. On the tissue culture plate, they were not any change throughout the culture period. These results demonstrated that low crystalline CO₃Ap exhibit higher osteoinductivity than HAp.