Effects of Escherichia Coli-derived Recombinant Human Bone Morphogenetic Protein-2 Loaded Porous Hydroxyaptite-based Ceramics on Calvarial Defect in Rabbits

BACKGROUND: Recombinant human bone morphogenetic proteins (rhBMPs) have been widely used in regenerative therapies to promote bone formation. The production of rhBMPs using bacterial systems such as Escherichia coli (E. coli) is estimated to facilitate clinical applications by lowering the cost without compromising biological activity. In clinical practice, rhBMP-2 and osteoconductive carriers (e.g., hydroxyapatite [HA] and bovine bone xenograft) are used together. This study examined the effect of E. coli-derived rhBMP-2 combined with porous HA-based ceramics on calvarial defect in rabbits. METHODS: Six adult male New Zealand white rabbits were used in this study. The experimental groups were divided into the following 4 groups: untreated (NC), bovine bone graft (BO), porous HA (HA) and porous HA with rhBMP-2 (HA-BMP). Four transosseous defects of 8 mm in diameter were prepared using stainless steel trephine bur in the frontal and parietal bones. Histological and histomorphometric analyses at 4 weeks after surgery revealed significant new bone formation by porous HA alone. RESULTS: HA-BMP showed significantly higher degree of bone formation compared with BO and HA group (P<0.05). The average new bone formation % (new bone area per total defect area) of NC, BO, HA, and HA-BMP at 4-week after surgery were 12.65±5.89%, 29.63±6.99%, 28.86±6.17% and 49.56±8.23%, respectively. However, there was no statistical difference in the bone formation between HA and BO groups. CONCLUSIONS: HA-BMP promoted more bone formation than NC, BO and HA alone. Thus, using E. coli-derived rhBMP-2 combined with porous HA-based ceramics can promote new bone formation.