Functionalized Scaffold and Barrier Membrane with Anti-BMP-2 Monoclonal Antibodies for Alveolar Ridge Preservation in a Canine Model

Abstract

Introduction: The aim of this study was to investigate the ability of anti-bone morphogenetic protein 2 monoclonal antibody (anti-BMP-2 mAb) to functionalize scaffolds to mediate bone regeneration in a canine model.

Materials and methods: The mandibular right premolar 4 (PM4) was extracted in eight beagle dogs and grafted with anti-BMP-2 mAb+anorganic bovine bone mineral with 10% collagen (ABBM-C) and porcine bilayer native collagen membrane (CM). The ABBM-C and CM were functionalized with either anti-BMP-2 mAb (test group) or an isotype matched control mAb (control group). Animals were euthanized at 12 weeks for radiographic, histologic, and histomorphometric analyses. Outcomes were compared between groups.

Results: 3D imaging using cone beam computed tomography (CBCT) revealed that sites treated with ABBM-C and CM functionalized with anti-BMP-2 mAb exhibited significantly more remaining bone width near the alveolar crest, as well as buccal bone height, compared with control groups. Histologic and histomorphometric analyses demonstrated that in anti-BMP-2 mAb-treated sites, total tissue volume was significantly higher in the coronal part of the alveolar bone crest compared with control sites. In anti-BMP-2 mAb-treated sites, bone formation was observed under the barrier membrane.

Conclusion: Functionalization of the ABBM-C scaffold and CM appeared to have led to bone formation within healing alveolar bone sockets.

Figure 1

(a) The mandibular right premolar 4 (PM4) was extracted with flap elevation as atraumatically as possible. (b) The sockets were filled with anorganic bovine bone mineral with 10% collagen (ABBM-C) functionalized with either anti-bone morphogenetic protein 2 monoclonal antibody (anti-BMP-2 mAb, test group) or isotype matched control mAb (control group). (c) The sockets filled with ABBM-C were covered by porcine bilayer native collagen membrane (CM) functionalized with either anti-BMP-2 mAb or isotype matched control mAb. The marginal gingiva was then approximated to achieve primary wound closure with a nonresorbable suture.

Figure 2

Repeatable anatomical structures such as the adjacent crest level (red line in upper image) and long axis of the adjacent tooth (blue line in lower two images) were used as references to measure dimensional alveolar bone change. (a) Remaining bone width at different levels of 1 mm, 2 mm, 3 mm, and 5 mm from the bone crest at the adjacent tooth and (b) buccal bone height level relative to bone crest at the adjacent tooth were measured at the buccal thirds of the examined alveolus.

Figure 3

Landmarks for histomorphometric analysis, showing lingual crest (LC) as a relatively stable reference. Additional landmarks relative to the LC are represented at 1 mm coronal (i.e., -1 mm) and 1, 2, and 3 mm apical to the LC. The amounts of total tissue volume in different zones relative to the LC (0-1 mm coronal, 0-1 mm apical, 1-2 mm apical, and 2-3 mm apical) were measured.

Figure 4

(a) Representative cone bean computed tomography (CBCT) images of anti-bone morphogenetic protein 2 monoclonal antibody- (anti-BMP-2 mAb-) treated site and isotype matched control mAb-treated site. (b) Remaining bone width at 1, 2, 3, and 5 mm from the bone crest at the adjacent tooth: a statistically significant difference in remaining bone width at 2 mm and 3 mm was found between the test group (N = 4) and control group (N = 4) (P = 0.03, P = 0.02, respectively). (c) Bone height level at buccal aspect (mm): the amounts of buccal bone height loss in the anti-BMP-2 mAb-treated sites (N = 4) and the isotype matched control mAb-treated sites (N = 4) were 1.17 ± 0.94 mm and 2.69 ± 0.63 mm, respectively, and were statistically significantly different (P = 0.03).

Figure 5

Histology at low magnification in the (a) anti-bone morphogenetic protein 2 monoclonal antibody- (anti-BMP-2 mAb-) treated site and (b) isotype matched control mAb site. Outline of alveolar bone in control sites appeared as a knife-edged shape due to buccal bone loss. The residual barrier collagen membrane (CM) was observed in both test and control sites (green dotted lines). Osteogenesis was observed within the entire extraction socket of both test and control sites. Histology at high magnification in (c) anti-BMP-2 mAb-treated and (d) isotype matched control mAb sites. The micrographs showed osteoblast-like cells (yellow arrowheads) as well as blood vessels (pink arrowheads) participating in active bone formation. The superficial anorganic bovine bone mineral (ABBM) particles (black asterisks in d) in control sites showed fibrotic encapsulation, while osteogenic cells as well as osteoid bone formation around residual ABBM graft particles were noted in test sites (white asterisk in c).

Figure 6

The amounts of total tissue volume within the extraction socket at 0-1 mm coronal to the lingual crest and at 0-1 mm, 1-2 mm, and 2-3 mm apical to the lingual crest. The anti-bone morphogenetic protein 2 monoclonal antibody- (anti-BMP-2 mAb-) treated sites (N = 4) revealed a statistically significant higher amount of total tissue volume at 0-1 mm coronal as well as at 0-1 mm apical of the alveolar bone crest relative to the lingual crest compared with the isotype matched control mAb-treated sites (N = 4) (P = 0.01, P = 0.02, respectively). Landmarks used for the analysis are shown in Figure 3.