Calcium phosphate ceramics promote the expression of bone cell markers in human mesenchymal stem cells

For bone tissue regeneration utilizing mesenchymal stem cells, it is important to use a scaffold that supports differentiation yet be fully degradable over time so as to promote full repair and remodeling of the defect. This study investigated the osteogenic differentiation of human MSCs on varying ratios of hydroxyapatite/tricalcium phosphate (HA/TCP) ceramic scaffolds. The faster degrading ratio of 20% HA/80% TCP was compared with the slower/nonresorbable formulation of 60/40 hydroxyapatite/tricalcium phosphate (HA/TCP) ceramic. MSCs were grown on these ceramics in the presence or absence (control) of osteogenic supplements in the media. Calcium and phosphate ion release in the culture media was also examined over time. Alkaline phosphatase activity was significantly higher for MSCs grown in control media on 20/80 HA/TCP ceramics than MSCs on tissue culture plastic and 60/40 HA/TCP at days 21 and 28. Osteocalcin was expressed by MSCs on 20/80 HA/TCP in control media, but not detected for MSCs grown on 60/40 HA/TCP and tissue culture plastic. In addition, the calcium level in the culture media containing MSCs on 60/40 HA/TCP decreased significantly at day 4 and remained below 1mM for up to 28 days. Whereas calcium levels in the culture media containing 20/80 HA/TCP decreased slightly at day 4 and remained relatively stable over time. This study has shown that 20/80 HA/TCP has a stimulatory effect on human MSCs differentiation into the bone cell phenotype as characterized by expression of high levels of alkaline phosphatase and osteocalcin production.