[Experimental observation of origins of osteoblasts in guided bone regeneration in long bone]

To study the origins of osteoblasts in guided bone regeneration (GBR) so as to understand the mechanism of GBR.

New Zealand rabbits were used. Standard ununited defect models were made in bilateral middle radial shaft of each rabbit. Randomly, one defect enveloped with silicon membrane as test, another without membrane as control. 12 rabbits were selected for X-ray examination weekly after procedure. 30 rabbits were divided into 6 groups, and sacrificed at 3 days, 1, 2, 3, 4, 5 weeks after surgery for histological observation by immunohistochemical staining of BMP, BGP.

The sealed spaces were made by silicon membranes in the defects to prevent peripheral tissue ingrowing early. The defect spaces were filled by granulation tissue formed from proliferative endoperiosteal and medullary stromal cells in bone end. Histological characteristics after callus forming showed that there were 2 - 3 layers of osteoblasts in the surface of callus, and granulation tissue in the center of bone defect. The transforming region existed between the extending callus and granulation tissue, which consisted of a few of cells and a lot of stroma. Early proliferative endo-periosteal and medullary stromal cells in the bone end were positive against BMP, BGP. Some cells in the transforming region were positive against BMP, BGP after callus forming.

Osteoblasts derive from endoperiosteum and medullary stroma in the early stage of GBR and from granulation tissue formed by proliferative endo-periosteal and medullary stromal cells in the later stage.