Bone Abstracts

Sustained release of bone morphogeneic protein (BMP)-2 by heparin-contained biomaterials is advantageous for bone tissue regeneration using low dose BMP-2. However, its effect in high dose BMP-2 is still unclear and should be clarified considering the clinical use of high dose of BMP-2 in spine and oral surgery. This study aimed to evaluate the efficacy of heparin-conjugated collagen sponge (HCS) in high dose BMP-2 delivery by investigating in vivo initial osteogenic regulation and bone healing over time passage to 12 weeks in comparison with that of an absorbable collagen sponge (ACS). The in vitro BMP-2 release profile in the HCS exhibited a lower burst followed by a sustained release of BMP-2, while that of the ACS showed an initial burst phase only. As a result of lower burst, the HCS-BMP group showed more expression of bone-forming/resorbing markers and more activation of osteoclasts than the ACS-BMP group within the scaffold of defect at 7 day, which is presumed to a retention of relatively higher amount of BMP-2. However, the surrounding calvaria were less resorbed in HCS-BMP group, compared to the aggressive resorptive response in the ACS-BMP group. Micro-computed tomography and histology revealed that HCS-BMP guided more effective bone regeneration of central defect during time passage by inducing minor ossification at defect exterior while ACS-BMP exhibited excessive ossification at the defect exterior. These results showed that HCS-mediated BMP-2 delivery at high dose has advantages over ACS including less early resorption of surrounding bone tissue and higher efficacy in compact bone regeneration over a longer period, highlighting a clinical feasibility.