THE CULTURE OF HUMAN OSTEOBLASTS UPON BONE-GRAFT SUBSTITUTES

In order to assess the ability of six potential bone graft substitutes to support the growth of human osteoblasts, these cells were grown in culture and then plated onto fragments of the six materials and cultu red for a further period of 15 days. Tests to confirm the osteoblastic phenotype of the cells included spectrophotometric alkaline phosphata se assay; Western blotting of secreted osteocalcin, osteonectin, bone sialoprotein, and collagen type I; and mineralization within the cultu res provided with a supplemented medium. Cells were seeded onto the ma terials in 24-well plates (Nunc, Naperville, IL) at density levels 12 500 cells/cm2 and 25 000 cells/cm2. Specimens were examined after the 15-day culture period by scanning electron microscopy. At a seeding de nsity of 12 500 cells/cm2 results showed that the human osteoblasts ha d greatest affinities for demineralized rat bone and demineralized Sur gibone(R), whilst few osteoblasts were found attached to Pyrost(R), Su rgibone(R), or coral. The collagen matrix of Callopat(R) hydrated in t he culture media exposing the hydroxyapatite crystals within it, and t hese became the foci for cell attachment and growth. At a seeding dens ity of 25 000 cells/cm2 the osteoblasts had attached to and proliferat ed upon the surfaces of all the materials, forming multilayers, with t he exception of Surgibone(R). These experiments demonstrated that all the materials, with the exception of nondemineralized Surgibone(R), we re biocompatable for human osteoblasts. The final population of osteob lasts on the bone graft substitutes appeared to be influenced by cell plating density, surface topography, and antigenicity of the materials .