Immunohistochemical study of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-2, -4 (BMP-2, -4) on lengthened rat femurs.
BACKGROUND
With a hypothesis that "angiogenesis occurs before osteogenesis," an experimental study using a rat model was carried out. Histological and immunohistochemical examinations of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-2, -4 (BMP-2, -4) were performed at the margins of bone formation after femoral bone lengthening.


METHODS
Thirty-five Wistar rats weighing 380-400 g (11-week-old males) were used. An external fixator was applied on the femur, and an osteotomy performed under general anaesthesia. Five days after the operation, femoral lengthening was initiated at a rate of 0.8 mm/day for 8 days. The rats were sacrificed just after distraction was completed, and at 1, 3, 5, 7, 9 and 14 days after distraction. The specimens from these rats were stained with haematoxylin-eosin, VEGF, and BMP-2, -4 immunohistochemical staining, and were investigated.


RESULTS
Expression of VEGF was observed in the woven bone at the osteogenetic front and near to osteoblasts around the newly formed bone. On the other hand, expressions of BMP-2, -4 were seen in the hypertrophic chondrocytes. In the same specimen, the VEGF area was further away from the bone stump than the BMP-2, -4 areas.


CONCLUSIONS
These results confirm the hypothesis that angiogenesis is induced before osteogenesis.
Department of Oral and Maxillofacial Surgery, Nagoya University, Graduate School of Medicine, Japan. ka-zu@med.nagoya-u.ac.jp
Kazumi
K
Sojo
Yoshihiro
Y
Sawaki
Hisashi
H
Hattori
Hideki
H
Mizutani
Minoru
M
Ueda
D000818:Animals; D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000032:analysis*; D005269:Femur / Q000737:chemistry* / Q000000981:diagnostic imaging; D008297:Male; D018919:Neovascularization, Physiologic; D019857:Osteogenesis, Distraction; D011859:Radiography; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000032:analysis*; D042461:Vascular Endothelial Growth Factor A / Q000032:analysis*
C525720:Bmp2 protein, rat; C525811:Bmp4 protein, rat; D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D016212:Transforming Growth Factor beta; D042461:Vascular Endothelial Growth Factor A