Perspectives of clinical application of bone morphogenetic proteins in children.

Abstract

The purpose of the study was to modify the method of Bone Morphogenetic Protein (BMP) extraction from bovine bones, estimate the osteoinductive potential of the extracted protein fractions in relation to the degree of protein purity and to test collagen formed in porous discs as a carrier. It was required before BMP application in reconstructive surgery in children. BMP preparation from bovine bones was conducted according to a modification of Luyten's method. Three fractions of different degree of purity - demineralised bone matrix "M", extract "E", and fraction after hydroxyapatite column "HP" - were tested for their osteoinductive potential. They were implanted on a collagen carrier into the right rat femoral muscle pouch. Controls were implanted in the same way in the left muscle pouch. The discs were removed after 3 and 6 weeks and tested for alkaline phosphatase activity, a marker of new bone formation. Out of the 10 animals used for testing the osteoinductive potential of matrix fraction, 7 results were positive and 3 negative. In the case of the extract fraction, the analysis was conducted for 3 weeks on 9 rats and 6 weeks on 13 rats. Six and 11 positive results were obtained, respectively. In the HP group 5 animals were observed for 3 weeks (3 positive, 2 negative) and 10 animals for 6 weeks (7 positive, 3 negative). In the case of the extract, the differences in alkaline phosphatase activity after 6 weeks were statistically significant (p <or= 0.05) compared to controls. In the other groups, a positive tendency was observed, but it was not statistically significant. Purified BMP has osteoinductive abilities causing ectopic new bone formation. From all obtained BMP fractions the extract had the highest osteoinductive potential and seems to be an optimal fraction for further clinical use. These results offer hope for a prompt clinical application of nonantigenic, xenogenic BMP, especially in three-dimensional bone reconstruction, for the treatment of non-united fractures or fractures with delayed union, to fill either bone cysts or other defects.