title: Combination therapy with BMP-2 and a systemic RANKL inhibitor enhances bone healing in a mouse critical-sized femoral defect.
abstract: Recombinant human BMP-2 (rhBMP-2) is a potent osteoinductive agent, but has been associated not only with bone formation, but also osteoclastogenesis and bone resorption. Osteoprotegerin (OPG) is a RANKL inhibitor that blocks differentiation and function of osteoclasts. We hypothesized that the combination of local BMP-2 (recombinant protein or a product of gene therapy) plus systemic OPG-Fc is more effective than BMP-2 alone in promoting bone repair. To test this hypothesis we used a mouse critical-sized femoral defect model. Col2.3eGFP (osteoblastic marker) male mice were treated with rhBMP-2 (group I), rhBMP-2 and systemic OPG (group II), rhBMP-2 and delayed administration of OPG (group III), mouse BM cells transduced with a lentiviral vector containing the BMP-2 gene (LV-BMP-2; group IV), LV-BMP-2 and systemic OPG (group V), a carrier alone (group VI) and administration of OPG alone (group VII). All bone defects treated with BMP-2 (alone or combined with OPG) healed, whereas minimal bone formation was noted in animals treated with the carrier alone or OPG alone. MicroCT analysis showed that bone volume (BV) in rhBMP-2+OPG and LV-BMP-2+OPG groups was significantly higher compared to rhBMP-2 alone (p<0.01) and LV-BMP-2 alone (p<0.001). Similar results were observed in histomorphometry, with rhBMP-2 alone defects exhibiting significantly lower bone area (B.Ar) compared to rhBMP-2+OPG defects (p<0.005) and LV-BMP-2 defects having a significantly lower B.Ar compared to all BMP-2+OPG treated groups (p≤0.01). TRAP staining demonstrated a major osteoclast response in the groups that did not receive OPG (rhBMP-2, LV-BMP-2 and sponge alone) beginning as early as 7days post-operatively. In conclusion, we demonstrated that locally delivered BMP-2 (recombinant protein or gene therapy) in combination with systemically administered OPG improved bone healing compared to BMP-2 alone in a mouse critical-sized bone defect. These data indicate that osteoclasts can diminish healing responses to BMP-2 and that RANKL inhibition may thus accentuate BMP-2 efficacy.
authors.affiliation: Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Sofia
authors.initials: S
authors.lastname: Bougioukli
authors.affiliation: Department of Orthopaedic Surgery, UConn Musculoskeletal Institute, University of Connecticut Health, Farmington, CT, USA.
authors.forename: Ashish
authors.initials: A
authors.lastname: Jain
authors.affiliation: Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Osamu
authors.initials: O
authors.lastname: Sugiyama
authors.affiliation: Department of Orthopaedic Surgery, UConn Musculoskeletal Institute, University of Connecticut Health, Farmington, CT, USA.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Tinsley
authors.affiliation: Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Amy H
authors.initials: AH
authors.lastname: Tang
authors.affiliation: Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Matthew H
authors.initials: MH
authors.lastname: Tan
authors.affiliation: Department of Orthopaedic Surgery, UConn Musculoskeletal Institute, University of Connecticut Health, Farmington, CT, USA.
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Adams
authors.affiliation: Phylon Pharma Services, Newbury Park, CA, USA; Department of Periodontics and Oral Medicine, School of Dentistry, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Kostenuik
authors.affiliation: Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA. Electronic address: Jay.Lieberman@med.usc.edu.
authors.forename: Jay R
authors.initials: JR
authors.lastname: Lieberman
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology*; D002452:Cell Count; D004359:Drug Therapy, Combination; D005269:Femur / Q000000981:diagnostic imaging / Q000187:drug effects / Q000473:pathology* / Q000601:surgery; D005629:Frozen Sections; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D016086:Lentivirus / Q000235:genetics; D008297:Male; D008810:Mice, Inbred C57BL; D010010:Osteoclasts / Q000187:drug effects / Q000473:pathology; D010012:Osteogenesis; D053244:Osteoprotegerin / Q000494:pharmacology*; D053245:RANK Ligand / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D000071681:Tartrate-Resistant Acid Phosphatase; D014161:Transduction, Genetic; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014945:Wound Healing / Q000187:drug effects*; D055114:X-Ray Microtomography
chemical_list: D055396:Bone Morphogenetic Protein 2; D007527:Isoenzymes; D053244:Osteoprotegerin; D053245:RANK Ligand; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase
keywords: Antiresorptives; BMP; Bone healing; Bone histomorphometry; Osteoclasts