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Repair of bone defects remains a major concern in plastic and maxillofacial surgery. Based on modern concepts of tissue engineering, periosteum has gained attention as a suitable osteogenic material. We tested the hypothesis that surgically released and immediately repositioned periosteum would exhibit high osteogenic capacity upon grafting in a rat calvarial defect. Seven days after periosteum was released from the tibia and immediately repositioned, the "primed periosteum graft" (PPG; n = 15) was placed into a critical-sized defect of rat calvaria and the process of bone formation was evaluated histologically, immunohistologically, and radiographically at 7, 14, and 21 days after grafting. Findings were compared with a nonprimed periosteal graft (NPG; n = 15). Endochondral ossification was observed in both the PPG and NPG. The PPG showed higher expression of proliferative cell nuclear antigen, bone morphogenetic protein, and vascular endothelial growth factor than the NPG. Three-dimensional radiographic examination revealed significantly increased bone formation in the PPG than in the NPG (P < 0.01). These findings suggested that surgical stimulation of the periosteum enhanced the osteogenic potential of periosteal cells. This method may be suitable for the clinical repair of bone defects.

Vessel invasion is an important step in cartilage replacement that leads to bone formation, and vascular endothelial growth factor (VEGF) has been implicated as a key player in this process. Although grafted periosteum undergoes endochondral ossification, little is known about the role of VEGF in this process. In the current study the authors investigated by immunohistochemical, histochemical, and ultrastructural techniques the localization of VEGF during bone formation in periosteal grafts. At day 14 after grafting the tibias of Japanese white rabbits, periosteal cells in the grafted tissue had differentiated into chondrocytes to form cartilage. Some chondrocytes were immunopositive for VEGF expression, and subsequent vessel invasion occurred predominantly in these VEGF-positive areas. At day 45, the cartilage invaded by blood vessels had been replaced by newly formed bone. These findings suggest that VEGF is associated with the process of blood vessel invasion into cartilage before bone replacement in endochondral ossification from grafted periosteum.

Purpose: To clarify the involvement of bone morphogenetic proteins (BMPs) in the proliferation and differentiation of osteo/chondrogenic cells during the process of bone formation from grafted periosteum., Material and Methods: Tibial periosteum of young Japanese white rabbits was grafted into suprahyoid muscles and removed after 7, 9, 14 or 21 days. BMP-2, -4, proliferative cell nucleus antigen (PCNA) immunoreaction and Alcian blue staining in grafted periosteum was then sought microscopically., Results: PCNA positive cells in the grafted periosteum expressed BMP-2 at 7 days. These cells differentiated into chondroblasts that expressed BMP-2 and Alcian blue at 9 days. After 14 days, cartilage formation was seen, and BMP-2 and -4 expressions were observed in mature and hypertrophic chondrocytes. Endochondral ossification was observed at 21 days and osteoblasts showed both BMP-2 and -4 expression., Conclusion: Both BMP-2 and -4 appear to play regulatory roles in the process of endochondral ossification from grafted periosteum, due to their involvement in the proliferation and differentiation into chondrogenic and osteogenic cells.

Grafted periosteum has a rich potential to induce heterotopic bone formation. In the current study the authors investigate whether autogenous periosteal grafts can regenerate the mandibular head in a rabbit model. They removed the mandibular head of Japanese white rabbits and grafted tibial periosteum to the cut surface of the mandible. Grafted periosteum was observed histologically and radiographically at day 7, 14, 21, and 45 after surgery. At day 7 after grafting, grafted tissue showed remarkable cell proliferation. By 14 days these cells had differentiated into chondrocytes to form cartilage, and endochondral ossification took place after 21 days. At 45 days after surgery, soft X-ray findings showed a newly formed mandibular head, which was similar histologically to that of a normal mandibular head. The cut mandible without periosteal graft showed no regeneration. These findings indicate that grafted periosteum can regenerate the mandibular head without special procedures such as bone fixation in a rabbit model, and suggest that this technique may be useful clinically.

To determine whether grafted young periosteum can induce new bone formation in elderly patients, this preliminary study evaluated cell proliferation and differentiation in xenogeneic periosteal grafts in old rats radiographically, histologically, and immunohistochemically. Periosteum harvested from the tibia of young Japanese white rabbits were grafted into old Sprague-Dawley rats with or without administration of 1.0 mg per kilogram per day immunosuppressant FK506. Autogenous old periosteal tissue grafts were also evaluated as a control. Grafted tissue was extirpated after 7, 14, 21, and 45 days. In the xenogeneic group, proliferative cell nuclear antigen-positive cells were observed 7 days after surgery, which differentiated into chondroblasts with bone morphogenetic protein-2 expression and finally formed cartilage by 14 days. Endochondral ossification was observed at 21 days, and bone replacement was completed by 45 days. No osteogenic cell activity was observed in the two other groups. Xenogeneic young periosteum thus maintained its osteogenic/chondrogenic potentiality in older rats.

Purpose: The purpose of the study was to determine whether a prefabricated graft of new bone induced from periosteum grafted into muscle was an effective material for the repair of jaw defects., Material and Methods: Artificial mandibular jaw defects in young Japanese rabbits were covered either with free grafted periosteum (n = 5) or a prefabricated graft of newly formed bone induced from periosteum, which was first grafted into the floor of the mouth, and placed as a revascularized muscle-pedicled bone flap (n = 5). Bone formation in jaw defects was examined radiographically and histologically 28 days after grafting into defects., Results: Bone formation was confirmed radiographically and histologically in both groups. However, the free grafted periosteum formed thin bone and fibrous tissue existed between the new and the original bone. In contrast, more active bone formation was observed with the prefabricated graft. This grafted new bone developed further and fused to the mandible. Blood vessels surrounding the new bone were observed histologically., Conclusion: These experimental findings suggested that prefabricated bone grafts induced from periosteum grafts are potentially useful for correction of jaw defects.