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.

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.

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.

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.