Functionalization of scaffolds with chimeric anti-BMP-2 monoclonal antibodies for osseous regeneration

Abstract

Recent studies have demonstrated the ability of murine anti-BMP-2 monoclonal antibodies (mAb) immobilized on an absorbable collagen sponge (ACS) to mediate de novo bone formation, a process termed antibody mediated osseous regeneration (AMOR). The objectives of this study were to assess the efficacy of a newly generated chimeric anti-BMP-2 mAb in mediating AMOR, as well as to evaluate the suitability of different biomaterials as scaffolds to participate in AMOR. Chimeric anti-BMP-2 mAb was immobilized on 4 biomaterials, namely, titanium microbeads (Ti), alginate hydrogel, macroporous biphasic calcium phosphate (MBCP) and ACS, followed by surgical implantation into rat critical-size calvarial defects. Animals were sacrificed after 8 weeks and the degree of bone fill was assessed using micro-CT and histomorphometry. Results demonstrated local persistence of chimeric anti-BMP-2 mAb up to 8 weeks, as well as significant de novo bone regeneration in sites implanted with chimeric anti-BMP-2 antibody immobilized on each of the 4 scaffolds. Ti and MBCP showed the highest volume of bone regeneration, presumably due to their resistance to compression. Alginate and ACS also mediated de novo bone formation, though significant volumetric shrinkage was noted. In vitro assays demonstrated cross-reactivity of chimeric anti-BMP-2 mAb with BMP-4 and BMP-7. Immune complex of anti-BMP-2 mAb with BMP-2 induced osteogenic differentiation of C2C12 cells in vitro, involving expression of RUNX2 and phosphorylation of Smad1. The present data demonstrated the ability of chimeric anti- BMP-2 mAb to functionalize different biomaterial with varying characteristics to mediate osteogenesis.

Biomechanical analysis of engineered bone with anti‐BMP2 antibody immobilized on different scaffolds

“…Chimeric anti-BMP-2 mAb (25 μg/mL) and isotype control mAb (25 μg/mL) were immobilized on each scaffold material, as previously described. 23 …”

“…23,24 The sectioned specimens were stained with hematoxylin and eosin (H&E). Images were captured using an Olympus DP50 digital camera (Olympus Optical Co, Japan) and the area for new bone formation and the percentages of defect fill were analyzed using NIH ImageJ software by determining the percentage of new bone fill out of the total area.…”

“…21, 22 More recently, we demonstrated the ability of chimeric anti-BMP-2 monoclonal antibodies (mAb) immobilized on different types of scaffold materials to mediate de novo bone formation. 23 …”

BBP-functionalized biomimetic nanofibrous scaffolds can capture BMP2 and promote osteogenic differentiation

“…Although the mechanism remains elusive, the unique capacity of selectively binding to BMP prevents it from degradation and partially explains the intriguing function of BBP [26–32]. Notably, a series of emerging findings indicates that endogenous BMPs (mainly BMP2), generated at the injury site are enough to heal critical-sized bone defect by transplanting an anti-BMP2-antibody immobilized ACS [33–35]. Although the antibody-based strategy is expensive and difficult for therapeutic translation, these findings underscore the feasibility of promoting critical bone healing by coordinating endogenous BMPs.…”

Selective protein adsorption for implantable biomaterials: A new road to bioactivity

“…Alternatively, streptavidin-biotin systems have been proposed to support selective enrichment for target molecules [15], although this approach is suitable only for pre-implant scaffold loading, as target bioactive molecules require biotynilation prior to loading. A different strategy was proposed by Freire [16,17] by immobilizing anti BMP2 antibodies on biomaterials, to promote selective binding of growth factors on scaffolds. The use of antibodies may however be limited by the size of these proteins, by compatibility issues, by constraints in the production of antibodies.…”