title: Effects of the orientation of anti-BMP2 monoclonal antibody immobilized on scaffold in antibody-mediated osseous regeneration.
abstract: Recently, we have shown that anti-BMP2 monoclonal antibodies (mAbs) can trap endogenous osteogenic BMP ligands, which can in turn mediate osteodifferentiation of progenitor cells. The effectiveness of this strategy requires the availability of the anti-BMP-2 monoclonal antibodies antigen-binding sites for anti-BMP-2 monoclonal antibodies to bind to the scaffold through a domain that will leave its antigen-binding region exposed and available for binding to an osteogenic ligand. We examined whether antibodies bound to a scaffold by passive adsorption versus through Protein G as a linker will exhibit differences in mediating bone formation. In vitro anti-BMP-2 monoclonal antibodies was immobilized on absorbable collagen sponge (ACS) with Protein G as a linker to bind the antibody through its Fc region and implanted into rat calvarial defects. The biomechanical strength of bone regenerated by absorbable collagen sponge/Protein G/anti-BMP-2 monoclonal antibodies immune complex was compared to ACS/anti-BMP-2 monoclonal antibodies or ACS/Protein G/isotype mAb control group. Results demonstrated higher binding of anti-BMP-2 monoclonal antibodies/BMPs to C2C12 cells, when the mAb was initially attached to recombinant Protein G or Protein G-coupled microbeads. After eight weeks, micro-CT and histomorphometric analyses revealed increased bone formation within defects implanted with absorbable collagen sponge/Protein G/anti-BMP-2 monoclonal antibodies compared with defects implanted with absorbable collagen sponge/anti-BMP-2 monoclonal antibodies (p < 0.05). Confocal laser scanning microscopy (CLSM) confirmed increased BMP-2, -4, and -7 detection in sites implanted with absorbable collagen sponge/Protein G/anti-BMP-2 monoclonal antibodies in vivo. Biomechanical analysis revealed the regenerated bone in sites with Protein G/anti-BMP-2 monoclonal antibodies had higher mechanical strength in comparison to anti-BMP-2 monoclonal antibodies. The negative control group, Protein G/isotype mAb, did not promote bone regeneration and exhibited significantly lower mechanical properties (p < 0.05). Altogether, our results demonstrated that application of Protein G as a linker to adsorb anti-BMP-2 monoclonal antibodies onto the scaffold was accompanied by increased in vitro binding of the anti-BMP-2 mAb/BMP immune complex to BMP-receptor positive cell, as well as increased volume and strength of de novo bone formation in vivo.
authors.affiliation: Laboratory for Immunoregulation and Tissue Engineering (LITE), Ostrow School of Dentistry of USC, University of Southern California, Los Angeles, CA, USA Center for Craniofacial Molecular Biology, Ostrow School of Dentistry of USC, University of Southern California, Los Angeles, CA, USA.
authors.forename: Sahar
authors.initials: S
authors.lastname: Ansari
authors.affiliation: Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Freire
authors.affiliation: Laboratory for Immunoregulation and Tissue Engineering (LITE), Ostrow School of Dentistry of USC, University of Southern California, Los Angeles, CA, USA.
authors.forename: Moon G
authors.initials: MG
authors.lastname: Choi
authors.affiliation: Laboratory for Immunoregulation and Tissue Engineering (LITE), Ostrow School of Dentistry of USC, University of Southern California, Los Angeles, CA, USA.
authors.forename: Azadeh
authors.initials: A
authors.lastname: Tavari
authors.affiliation: Dental Research Center (DRC), Tissue Engineering and Biomaterials Research Unit (TEBRU), College of Dentistry, Qassim University, Qassim, Saudi Arabia.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Almohaimeed
authors.affiliation: Center for Craniofacial Molecular Biology, Ostrow School of Dentistry of USC, University of Southern California, Los Angeles, CA, USA.
authors.forename: Alireza
authors.initials: A
authors.lastname: Moshaverinia
authors.affiliation: Laboratory for Immunoregulation and Tissue Engineering (LITE), Ostrow School of Dentistry of USC, University of Southern California, Los Angeles, CA, USA zadeh@usc.edu.
authors.forename: Homayoun H
authors.initials: HH
authors.lastname: Zadeh
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D055910:Antibodies, Immobilized / Q000008:administration & dosage / Q000276:immunology / Q000627:therapeutic use*; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000276:immunology / Q000627:therapeutic use*; D055396:Bone Morphogenetic Protein 2 / Q000276:immunology*; D001861:Bone Regeneration / Q000187:drug effects*; D002460:Cell Line; D003094:Collagen / Q000737:chemistry; D005260:Female; D051379:Mice; D017207:Rats, Sprague-Dawley; D012886:Skull / Q000187:drug effects* / Q000276:immunology / Q000293:injuries / Q000502:physiology*
chemical_list: D055910:Antibodies, Immobilized; D000911:Antibodies, Monoclonal; D055396:Bone Morphogenetic Protein 2; D003094:Collagen
keywords: Bone regeneration; Protein G; biomaterials; chimeric anti-BMP2 monoclonal antibodies; tissue engineering