Evaluation of Scaffolds Functionalized with Anti-BMP-2 Antibody in Promoting AMOR

Objectives: The purpose of the current study was to examine the efficacy of immobilized anti-BMP-2 antibodies on 4 different biomaterials in promoting Antibody Mediated Osseous Regeneration (AMOR). 

Methods: Four scaffold used included, Ti microbeads, alginate hydrogel (Alg), beta-TCP and absorbable collagen sponge (ACS).  Anti-BMP-2 mAb (25 ug/ml), isotype control Ab (negative control; 25 ug/ml), as well as recombinant human BMP-2 (rhBMP-2, 1.5mg/ml; positive control) were adsorbed on each of the scaffolds by incubation at room temperature for 1 hour. The treated biomaterials were surgically implanted into 5mm rat calvarial defects. After 8 weeks, the animals were sacrificed and calvarial specimens were harvested. Micro-CT analysis of dissected calvarial specimens was followed by histologic and histomorphometric analysis to evaluate bone formation. 5 μm thick sections were stained with hematoxylin and eosin and Masson Trichrome. Nikon camera was used to image the stained slides and, the histomorphometric analyses were performed using NIH ImageJ software. Immunohistochemistry was used to examine the distribution of BMP-2 and osteocalcin proteins in situ. One-way and two-way analysis of variance (ANOVA), followed by Tukey`s test at significant level of α = 0.05, was used for statistical analysis of data.

Results: The micro-CT and histomorphometric analysis showed significant bone regeneration within calvarial defects implanted with anti–BMP2 mAb immobilized on each of the scaffolds, but not those with isotype control Ab (p<0.05). Ti microbeads showed the highest degree of bone regeneration, followed by alginate hydrogels and ACS. The degree of bone regeneration achieved with immobilized anti–BMP2 mAb was comparable to the positive control (rhBMP-2).

Conclusions: This study confirms the ability of anti-BMP mAb to efficiently promote bone formation when immobilized on protein (ACS), hydrogel (Alg), mineral (TCP), as well as metal (Ti) scaffolds.