THE EVALUATION OF OSTEOGEMC POTENTIAL OF CULTURED PERIOSTEUM-DERIVED CELLS

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Periosteum has osteogenic potential and considerable attention has been focused on its use as a grafting material for the repair of bone and joint defects. Recently, the osteogenic potential of cultured periosteal cells has been reported. We present findings of bone formation induced from cultured periosteum-derived cells of rats tibiae. Periosteum was placed in culture medium with 10% Fetal Bovine Serum for 14 days. After reaching confluence, periosteal cells were resuspended with 025% trypsin/EDTA and then re-cultured three dimensionally on a collagen sponge for 7 days. Periosteal cell/collagen complex was grafted into rat submandibular muscle and A solution of plasmid DNA containing mouse BMP-4 (pMiw-BMP-4, kindly provided by Dr.Brigid I.M. Hogan and Dr.Kishimoto, Tohoku Univ.) was injected into grfated tissue and electric pulses were applied through paired-needle electrodes. As a control plasmid, Normal saline solution was injected. Immunosuppressant (FK506, 1.0 mg/kg/day) was administered intramuscularly. At 14, 21 and 35 days post grafting, grafted tissue was extirpated and compared histologically and radiographically with control groups. In the experimental group, periosteal cells had proliferated and differentiated into osteogenic cells by 14 days post grafting. Cell proliferation marker PCNA positive cells significantly increased compared with control groups. At 21 days post grafting, new bone formation was evident. At this stage, VEGF and BMP-4 positive cells significantly increased compared with control groups. By 35 days post grafting, bone growth was observed and new calcification was detected radiographically in the defect. New bone formation in experimental group developed and total calcified area was larger than control group. Cultured periosteum-derived cells treated with BMP-4 gene showed higher osteogenic potential in the early stage of periosteal cell graft model of rat.