OBJECTIVETo study the expression and distribution of bone morphogenetic protein (BMP) in newly formed bone by distraction osteogenesis (DO), and to explore the mechanism of the DO bone formation and remodeling.

METHODSThe cleft palate (CP) experimental animal models (23 Rhesus monkeys) were established surgically. In experimental group (21 Rhesus monkeys), the palatal defects were corrected by means of DO at the rhythm of 0.4 mm twice per day. The specimens were retrieved under euthanasia at 1, 2, 4, 6, 8, 12, 24 weeks intervals respectively in retention period. BMP immunohistochemical study was then performed. The blank control and experimental group (each of 2 animals) were set for comparison study.

RESULTSThe immunohistochemical study showed that BMP existed mainly in cytoplasma of osteoblasts, during the process of new bone formation. In early stage of 1 or 2 weeks, abundant osteoblasts aggregating on surfaces of the new bone trabeculae with positive DAB dye were observed. Through 4 to 6 weeks, the proliferative osteoblasts with very strong positive DAB dye indicating BMP expression were recorded. From 8 to 12 weeks, the expression of BMP and quantity of osteoblasts decreased gradually while more matured new bone structures were observed.

CONCLUSIONDuring the whole retention period, the expression of BMP showed a tendency from weak to strong and then to final cessation, this indicated a process of formation, remodeling and maturation of osteogenesis.