Osteogenic capacity of rat and human marrow cells in porous ceramics. Experiments in athymic (nude) mice.

Porous hydroxyapatite ceramics, alone and combined with rat marrow cells, were implanted subcutaneously in 22 nude mice. The ceramics alone were invaded by fibrovascular tissue without any bone formation. In contrast, all the ceramics combined with marrow cells had bone formation in the pores 4 to 8 weeks after implantation. The bone formation began on the surface of the ceramic with direct bonding of the bone to the ceramic and proceeded to the center of the pores. The ceramics were also combined with bone marrow cells from 7 humans and implanted in nude mice. In five experiments, bone formation occurred after implantation. In addition, the ceramics were combined with in vitro cultured fibroblastic cells, resulting in bone formation in 2/6 cases. Our results indicate that the osteogenic ability of human marrow cells is sustained by porous hydroxyapatite ceramics.