Enhancement of the biological activity of BMP-2 by synthetic dextran derivatives.

ABSTRACT

In the present study, we explored the binding capacity of synthetic heparin-like dextran derivatives to recombinant human bone morphogenetic protein 2 (BMP-2), a heparin-binding osteoinductive growth factor. Affinity electrophoresis analysis provided evidence that carboxymethylated dextran polymers grafted with high amounts of benzylamide groups (named DMCB) interact with BMP-2. The capability of such polysaccharides to potentiate the growth factor biological activity was then investigated. In vitro, DMCB dose-dependently promoted osteoblast differentiation induced by BMP-2 in C2C12 myoblasts more efficiently than heparin. A screening study provided evidence that the potentiating effects of the dextran derivatives on the BMP-2-induced alkaline phosphatase activity improved with their benzylamide groups content and, therefore, with their affinity for the growth factor. The biological activity of BMP-2 was monitored in the culture medium after 6 days using C2C12 cells (containing a BMP sensitive luciferase reporter gene). Like heparin, DMCB sustained the biological activity of the growth factor; this result suggests that the formation of the BMP-2/DMCB complex may protect the protein from being inactivated. In rats in vivo, DMCB also stimulated ectopic calcification mediated by BMP-2. These data indicate that dextran-based polysaccharides prolong the half-life of the growth factor and promote its biological activity.