BACKGROUND:According to the core functional zone of amino acid sequence of the osteoinduction in bone morphogenetic proteins, our research group synthesized bone morphogenetic protein (BMP) active polypeptides Ⅰ and Ⅱ by artificial solid-state synthesis method. OBJECTIVE: To evaluate the osteoinductive ability of BMP active polypeptides Ⅰ and Ⅱ in animals. METHODS:Forty-two Sprague-Dawley rats were randomly divided into seven groups, and respectively implanted with hydroxyapatite/polylactic acid carrying 0.2, 0.4, 0.8 g/L BMP active polypeptides I, hydroxyapatite/polylactic acid carrying 0.2, 0.4, 0.8 g/L BMP active polypeptides Ⅱ, and hydroxyapatite/polylactic acid alone. At 3 and 5 weeks postoperatively, X-ray, CT and histological detection were conducted to evaluate osteoinductive conditions in the seven groups. RESULTS AND CONCLUSION:At 3 and 5 weeks postoperatively, there were better local osteoinductive effects in the groups hydroxyapatite/polylactic acid carrying BMP active polypeptides Ⅰ and Ⅱ than the group of hydroxyapatite/polylactic acid, indicating both two kinds of BMP active polypeptides possessed a certain osteoinductive ability. Moreover, this osteoinductive ability became stronger with time. At 5 weeks postoperatively, the osteoinductive effect in the 0.4 and 0.8 g/L BMP active polypeptides I groups was better than that in the 0.2 g/L BMP active polypeptides I group and the 0.2, 0.4 and 0.8 BMP active polypeptides Ⅱ groups (P < 0.05). In addition, there was no difference in the osteoinductive effect of 0.4 and 0.8 g/L BMP active polypeptides I groups. These results indicate that BMP active polypeptides I has a stronger osteoinductive ability than BMP active polypeptides Ⅱ.