In vitro mineralization of osteoblastic cells derived from human bone

Osteoblastic cells were isolated from human maxilla by embedding the bone pieces in collagen gel. The isolated cells could be maintained in monolayer culture up to 50 population doubling levels (PDLs). Both parathyroid hormone (PTH) and prostaglandin E2 (PGE2) increased intracellular cyclic AMP level of the cells. The cells also showed high level of alkaline phosphatase (ALPase) activity and formed mineralized areas in monolayer culture. Electron microscopy demonstrated that these cells were surrounded by numerous well-banded collagen fibrils, among which matrix vesicles were scattered. It was also observed that needle-shaped crystals protruded from some matrix vesicles. These protruded crystals appeared to deposit along the collagen fibrils and a mineralized matrix was formed. The minerals of mineralized matrix mainly consisted of calcium and phosphorus and had the same Ca/P ratio as hydroxyapatite. These results indicate that the cells derived from human bone have characteristics of osteoblastic cells.