title: Retention of in vitro and in vivo BMP-2 bioactivities in sustained delivery vehicles for bone tissue engineering.
abstract: In this study, we investigated the in vitro and in vivo biological activities of bone morphogenetic protein 2 (BMP-2) released from four sustained delivery vehicles for bone regeneration. BMP-2 was incorporated into (1) a gelatin hydrogel, (2) poly(lactic-co-glycolic acid) (PLGA) microspheres embedded in a gelatin hydrogel, (3) microspheres embedded in a poly(propylene fumarate) (PPF) scaffold and (4) microspheres embedded in a PPF scaffold surrounded by a gelatin hydrogel. A fraction of the incorporated BMP-2 was radiolabeled with (125)I to determine its in vitro and in vivo release profiles. The release and bioactivity of BMP-2 were tested weekly over a period of 12 weeks in preosteoblast W20-17 cell line culture and in a rat subcutaneous implantation model. Outcome parameters for in vitro and in vivo bioactivities of the released BMP-2 were alkaline phosphatase (AP) induction and bone formation, respectively. The four implant types showed different in vitro release profiles over the 12-week period, which changed significantly upon implantation. The AP induction by BMP-2 released from gelatin implants showed a loss in bioactivity after 6 weeks in culture, while the BMP-2 released from the other implants continued to show bioactivity over the full 12-week period. Micro-CT and histological analysis of the delivery vehicles after 6 weeks of implantation showed significantly more bone in the microsphere/PPF scaffold composites (Implant 3, p<0.02). After 12 weeks, the amount of newly formed bone in the microsphere/PPF scaffolds remained significantly higher than that in the gelatin and microsphere/gelatin hydrogels (p<0.001), however, there was no statistical difference compared to the microsphere/PPF/gelatin composite. Overall, the results from this study show that BMP-2 could be incorporated into various bone tissue engineering composites for sustained release over a prolonged period of time with retention of bioactivity.
authors.affiliation: Tissue Engineering and Biomaterials Laboratory, Department of Orthopedic Surgery, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA.
authors.forename: Diederik H R
authors.initials: DH
authors.lastname: Kempen
authors.forename: Lichun
authors.initials: L
authors.lastname: Lu
authors.forename: Teresa E
authors.initials: TE
authors.lastname: Hefferan
authors.forename: Laura B
authors.initials: LB
authors.lastname: Creemers
authors.forename: Avudaiappan
authors.initials: A
authors.lastname: Maran
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Classic
authors.forename: Wouter J A
authors.initials: WJ
authors.lastname: Dhert
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Yaszemski
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology; D001842:Bone and Bones / Q000166:cytology / Q000187:drug effects; D002460:Cell Line; D005650:Fumarates / Q000737:chemistry; D005780:Gelatin / Q000737:chemistry; D020100:Hydrogels / Q000737:chemistry; D019344:Lactic Acid / Q000737:chemistry; D008297:Male; D051379:Mice; D008863:Microspheres; D010012:Osteogenesis / Q000187:drug effects; D011100:Polyglycolic Acid / Q000737:chemistry; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011126:Polypropylenes / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D023822:Tissue Engineering / Q000379:methods*; D016212:Transforming Growth Factor beta / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology
chemical_list: C525719:Bmp2 protein, mouse; C525720:Bmp2 protein, rat; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D005650:Fumarates; D020100:Hydrogels; D011126:Polypropylenes; D016212:Transforming Growth Factor beta; C097850:poly(propylene fumarate); D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D005780:Gelatin