title: Discontinuous release of bone morphogenetic protein-2 loaded within interconnected pores of honeycomb-like polycaprolactone scaffold promotes bone healing in a large bone defect of rabbit ulna.
abstract: The choice of an appropriate carrier and its microarchitectural design is integral in directing bone ingrowth into the defect site and determining its subsequent rate of bone formation and remodeling. We have selected a three-dimensional polycaprolactone (PCL) scaffold with an interconnected honeycomb-like porous structure to provide a conduit for vasculature ingrowth as well as an osteoconductive pathway to guide recruited cells responding to a unique triphasic release of osteoinductive bone morphogenetic proteins (BMP) from these PCL scaffolds. We hypothesize that the use of recombinant human bone morphogenetic protein 2 (rhBMP2)-PCL constructs promotes rapid union and bone regeneration of a large defect. Results of our pilot study on a unilateral 15 mm mid-diaphyseal segmental rabbit ulna defect demonstrated enhanced bone healing with greater amount of bone formation and bridging under plain radiography and microcomputed tomography imaging when compared with an empty PCL and untreated group after 8 weeks postimplantation. Quantitative measurements showed significantly higher bone volume fraction and trabecular thickness, with lower trabecular separation in the rhBMP2-treated groups. Histology evaluation also revealed greater mature bone formation spanning across the entire scaffold region compared with other groups, which showed no bone regeneration within the central defect zone. We highlight that it is the uniqueness of the scaffold having a highly porous network of channels that promoted vascular integration and allowed for cellular infiltration, leading to a discontinuous triphasic BMP2 release profile that mimicked the release profile during natural repair mechanisms in vivo. This study serves as preclinical evidence demonstrating the potential of combining osteoinductive rhBMP2 with our PCL constructs for the repair of large defects in a large animal model.
authors.affiliation: Department of Orthopaedic Surgery, Korea University Ansan Hospital, Ansan Si, Gyeonggi Do, Korea.
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Bae
authors.forename: Hae-Ryong
authors.initials: HR
authors.lastname: Song
authors.forename: Hak-Jun
authors.initials: HJ
authors.lastname: Kim
authors.forename: Hong-Chul
authors.initials: HC
authors.lastname: Lim
authors.forename: Jung-Ho
authors.initials: JH
authors.lastname: Park
authors.forename: Yuchun
authors.initials: Y
authors.lastname: Liu
authors.forename: Swee-Hin
authors.initials: SH
authors.lastname: Teoh
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology*; D006801:Humans; D008297:Male; D011091:Polyesters / Q000494:pharmacology*; D016062:Porosity / Q000187:drug effects; D011817:Rabbits; D011994:Recombinant Proteins / Q000494:pharmacology; D054457:Tissue Scaffolds / Q000737:chemistry*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014457:Ulna / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000473:pathology* / Q000601:surgery; D014945:Wound Healing / Q000187:drug effects*; D055114:X-Ray Microtomography
chemical_list: D055396:Bone Morphogenetic Protein 2; D011091:Polyesters; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; C016240:polycaprolactone