ABSTRACT
The periosteum provides a good cell source for bone formation because it possesses osteoprogenitors. In this study, the osteogenic activity of the rabbit periosteum and periosteal cells was investigated. The periosteum was harvested from the long bone surface of New Zealand White rabbits. The periosteal cells were isolated from the periosteum and expanded. In vitro examination, the morphological changes, mineralization, and osteogenicity of the periosteal cells were evaluated. The amount of osteocalcin released was measured to check the maximal activity of the cells. The periosteum and periosteal cells-scaffold composites were transplanted into athymic mice to observe the in vivo bone formation. Radiological and histological changes were checked every 2 weeks. The isolated periosteal cells were uniformly proliferated in a monolayer culture, and mineral deposition was confirmed after 10 weeks. The osteogenic markers such as osteopontin, osteonectin, type I collagen, and alkaline phosphatase were expressed from the periosteal cells after 2 weeks. Osteocalcin was expressed after 3 weeks and was maximally expressed at 4 weeks. In 3-dimensional culture, the periosteal cells were well adhered and proliferated on the poly L-lactic-co-glycolic acid scaffold. The periosteal cells-scaffold composite transplant produced of osteoid without calcification in vivo. Radiological examination showed minimal changes of bone formation during the experimental period. However, the periosteum transplant was converted to a cartilaginous structure at 2 weeks, bony calcification after 4 weeks, and complete bony trabecula and marrow space formation at 12 weeks. The radiological bone density also increased during the experimental period. The periosteum may be one of good cell sources for osseous tissue engineering. Engineered periosteal cells may be used for the treatment of nonunion, osteolysis, avascular necrosis and fusion of the spine.