Interactions of total bone marrow cells with increasing quantities of macroporous calcium phosphate ceramic granules.

The biological properties of synthetic calcium phosphate bioceramics have made them the third choice of material for bone reconstructive surgery, after autologous bone and allografts. Nevertheless, bioceramics lack the osteogenic properties that would allow them to repair large bone defects. One strategy in bone tissue engineering consists of associating a synthetic scaffold with osteogenic cells. Mesenchymal stem cells (MSC) are usually isolated from bone marrow cultured for several weeks and seeded on to a small quantity of bioceramic. We have studied the association of total bone marrow cells, harvested from femurs of rats, with increasing amounts of calcium phosphate ceramic granules (50-250 mg). A cell viability test indicated that a little quantity of bioceramics granules (50 mg) was less detrimental for culturing 1 million nucleated cells from the whole bone marrow population. Cell morphology, viability, adhesion and differentiation were studied after different culture periods. Among the heterogeneous population of bone marrow cells, only a limited amount of cells attached and differentiated on the bioceramics. To explain the influence of the amount of synthetic scaffold on cell viability, media calcium concentrations were measured. Low cell viability could be explained by calcium phosphate precipitation leading to a decrease in calcium concentrations observed with relatively large amounts of scaffold. This study showed that the chemical stability of the ceramic plays a critical role in the viability of bone marrow cells.