Development of a growth factor bioavailability enhanced allograft (GFBA) for bone regeneration

Bone morphogenetic protein (BMP) stimulated osteoinduction is critical for bone regeneration. Human demineralized bone matrix (DBM) has been one of the most widely used bone graft substitutes, but its osteoinductive potential is weak and clinical effectiveness limited in part due to ineffective processing methods. Here, we describe a novel process designed to enhance allograft bioactivity by increasing the bioavailability of the native BMPs present within the matrix the product of which we call Natural Matrix Protein® (NMP®). BMP-7 release was quantified from NMP and DBM prepared from both bovine and human cortical bone. In both species, NMP significantly increased BMP-7 levels in acidic and physiologic extracts compared to DBM. NMP also demonstrated sustained release of BMP-7 and total protein for up to 12 weeks in simulated body fluid. Osteoinductive potential was evaluated in vitro using C2C12 cells and osteoinductivity in vivo in the athymic rat model. Direct treatment of cells with NMP in vitro produced a greater than tenfold increase in alkaline phosphatase activity at 40 mg/mL. In vivo, human NMP showed increased osteoinductivity compared to human DBM histologically, and the recovered NMP explants had significantly more mineralized bone and a higher bone volume fraction compared to DBM and to Infuse® Bone Graft (105 µg rhBMP-2 on an absorbable collagen sponge) as measured by microCT. These findings demonstrate that the novel NMP process reproducibly increases BMP-7 bioavailability, that NMP implants produce sustained BMP and protein release and have marked increase in osteoinductive activity.