Adsorption and release pattern of recombinant human bone morphogenic proatin 2 onto different bone grafts and its consequent osteoblasts` activation and neutrophils` priming

Abstract

Objectives

Controlled long-term delivery of recombinant human bone morphogenic proatin 2 (rhBMP2) eluted in a collagen scaffolds suffer from only a high initial burst release. The purpose of the current study was to investigate the long-term delivery of rhBMP2 when mixed with different bone grafts and its impact on osteoblastic activity and neutrophil priming.

Methods

rhBMP2 was separately mixed with xenograft, allograft, or alloplast and incubated for 30 days. Levels of BMP2 adsorption and their release were measured using immunofluorescence and ELISA respectively. The supernatants from the grafts were then incubated with either osteoblast (Saos-2 cells) or neutrophils (differentiated from HL60) for alkaline phosphatase and oxidative stress measurements respectively. Gene expression of osteoblast functionality and neutrophil priming were measured with qRT-PCR.

Results

rhBMP2 was adsorbed onto all tested grafts, with a superior effect of alloplast. The release of the rhBMP2 from all grafts was similar and sustained for 30 days with the lowest levels in the alloplast group. Activation of osteoblast was robust in the allograft and xenograft groups, concomitant with elevated osteocalcin expression. Neutrophil priming was greatest in the xenograft group, together with elevated expression of interleukin 1β.

Conclusion

rhBMP2 with bone graft material constitutes its sustained release over time. This, in turn, robust osteoblast and neutrophil activity.