Osteogenesis by human osteoblastic cells in diffusion chamber in vivo

Osteogenic potential of osteoblastic cells isolated from human bone was evaluated by a diffusion chamber method. Cells placed in diffusion chambers were implanted intraperitoneally into the athymic mice. The diffusion chambers cultured in vivo were harvested and examined after implantation for 6-8 weeks. The content of the chamber was proved by a soft roentogenogram to contain the radioopaque area. Light microscopic study revealed that this area was made up of bone-like nodule. Within the diffusion chambers, the cell layers were observed alongside the interior surface of the membrane filters, and mineralized nodules were formed among the cell layers. The mineralized nodules were confirmed by staining with the von Kossa technique for calcium mineral deposits. In electron microscopic study, the osteoblastic cells had a relatively large nuclei, and an abundant rough endoplasmic reticulum produced numerous extracellular matrix. In the bone-like nodules, the osteoblastic cells were surrounded by a heavily mineralized matrix with nonmineralized matrix separating the osteoblastic cells from the mineralized matrix. The mineralized matrix contained well-banded collagen fibrils. Matrix vesicles and collagen fibrils which were closely associated with mineral deposition were observed at the mineralizing front. These results together with our previous report [13] indicate that isolated human osteoblastic cells possessed osteogenic potential in vivo as well as mineralization activity in vitro.