title: Antibody-mediated osseous regeneration: a novel strategy for bioengineering bone by immobilized anti-bone morphogenetic protein-2 antibodies.
abstract: Bone regeneration often requires harvesting of autologous bone with significant potential morbidity and cost. Recombinant human bone morphogenetic protein (rhBMP)-2 has been approved by the U.S. Food and Drug Administration for specific regenerative indications. However, administration of exogenous growth factors has many drawbacks. The objective of the present proof-of-concept study was to determine whether immobilized anti-BMP-2 antibodies (Abs) could capture endogenous BMP-2 in local sites to mediate osteogenesis, a strategy we refer to as antibody-mediated osseous regeneration (AMOR). We have generated a murine anti-BMP-2 monoclonal antibody library, which was tested along with commercially available Abs in vitro and in vivo for their ability to mediate AMOR. In vitro studies demonstrated that only some anti-BMP-2 Abs tested formed immune complexes with BMP-2, which can bind to BMP cellular receptor, whereas other BMP-2/anti-BMP-2 complexes failed to bind. To investigate whether anti-BMP-2 Abs were able to mediate AMOR in vivo, anti-BMP-2 Abs were immobilized on absorbable collagen sponge (ACS) and surgically placed in rat calvarial defects. Microcomputed tomography analysis of live animals at 2, 4, and 6 weeks demonstrated that some anti-BMP-2 Abs immobilized on ACS mediated significant bone regeneration, whereas other clones did not mediate any bone regeneration. In situ BMP-2 and osteocalcin expression was investigated by immunohistochemistry. Results demonstrated higher BMP-2 and osteocalcin expression in sites with increased bone regeneration. Results provide first evidence for the ability of anti-BMP2 Abs to form an immune complex with endogenous BMP-2 and mediate bone regeneration in vivo, suggesting a promising therapeutic method for tissue engineering.
authors.affiliation: Laboratory of Immune Regulation and Tissue Engineering, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90089, USA.
authors.forename: Marcelo O
authors.initials: MO
authors.lastname: Freire
authors.forename: Huyng-Keun
authors.initials: HK
authors.lastname: You
authors.forename: Joong-Ki
authors.initials: JK
authors.lastname: Kook
authors.forename: Jeong-Ho
authors.initials: JH
authors.lastname: Choi
authors.forename: Homayoun H
authors.initials: HH
authors.lastname: Zadeh
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology*; D057005:Bioengineering / Q000379:methods*; D055396:Bone Morphogenetic Protein 2 / Q000276:immunology*; D001861:Bone Regeneration / Q000187:drug effects*; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000502:physiology*; D002460:Cell Line; D005434:Flow Cytometry; D006801:Humans; D055767:Immobilized Proteins / Q000494:pharmacology*; D007150:Immunohistochemistry; D020007:Implants, Experimental; D051379:Mice; D015675:Osteocalcin / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D011994:Recombinant Proteins / Q000276:immunology; D012886:Skull / Q000000981:diagnostic imaging / Q000187:drug effects / Q000473:pathology; D016212:Transforming Growth Factor beta / Q000276:immunology*; D055114:X-Ray Microtomography
chemical_list: D000906:Antibodies; D055396:Bone Morphogenetic Protein 2; D055767:Immobilized Proteins; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D015675:Osteocalcin