Dentin phosphophoryn (DPP) is an acidic non-collagenous protein in dentin. In vitro, DPP induces apatite formation when immobilized to insoluble substrates such as type I collagen fibrils and agarose beads. In the present study, DPP purified from fresh bovine dentin was evaluated as a co-factor for recombinant human bone morphogenetic pro-tein-2 (rhBMP-2) in rhBMP-2-induced bone formation in rats. Five micrograms of Es-cherichia coli-derived rhBMP-2 variant was adsorbed to composite of 50 mg of hy-droxyapatite (HAP) with or without 1 mg of DPP. Next, rhBMP-2/HAP/DPP composite or rhBMP-2/HAP composite was implanted subcutaneously in 4-week-old Wistar rats. Rats were sacrificed at 2 and 3 weeks after implantation. Throughout the experimental period, rhBMP-2/HAP/DPP composite induced more bone formation than rhBMP-2/HAP com-posite. In the histomorphological analysis, bone induced by rhBMP-2/HAP/DPP composite accounted for 69-17% (n=6) of the total composite while accounting for 45±13% (n=6) of the rhBMP-2/HAP composite at 3 week postimplantation. These results indicate that the bone-inducing activity of rhBMP-2 is enhanced by DPP as a co-factor of rhBMP-2 in vivo.
Key words: : Phosphophoryn (DPP), rhBMP-2, Co-factor, Carrier, Bone formation