title: Porous silk fibroin 3-D scaffolds for delivery of bone morphogenetic protein-2 in vitro and in vivo.
abstract: Bone morphogenetic protein-2 (BMP-2) plays a key role in osteogenesis. Biomaterials used for the sustained delivery of BMP-2 in vivo have shown therapeutic benefits. In the present study, BMP-2 was loaded in porous silk fibroin scaffolds derived from silkworm cocoons (2.4 +/- 0.14 microg per scaffold). The release profile of BMP-2 under dynamic culture conditions (spinner flasks) showed that after 1 week in culture 25% of the initial BMP-2 was retained adsorbed to the scaffold; up to 4 weeks no additional BMP-2 was released. BMP-2 induced human bone marrow stromal cells (hMSCs) to undergo osteogenic differentiation when the seeded scaffolds were cultured in medium supplemented with osteogenic stimulants for 4 weeks, based on elevated alkaline phosphatase activity, calcium deposition, and transcript levels for bone sialoprotein, osteopontin, osteocalcin, BMP-2, and cbfa-1. Micro-computed tomography revealed densely deposited mineral at the center of the scaffolds. In contrast, hMSCs cultured in control scaffolds (no BMP-2) exhibited limited osteogenesis. When implanted in critical sized cranial defects in mice, scaffolds loaded with BMP-2 and seeded with hMSCs resulted in significant bone ingrowth. These results were qualitatively similar to scaffolds loaded with BMP-2 but no hMSCs or with BMP-2 and hMSCs but not pregrown into bone-like tissue. Bone-related outcomes were improved when compared with the scaffold controls implanted without BMP-2. These studies illustrate the potential use of slow degrading silk fibroin 3-D scaffolds loaded with BMP-2, in combination with hMSCs, in osteogenesis studies in vitro and in vivo, and provide a new range of material properties for these applications.
authors.affiliation: Department of Biomedical Engineering Chemical and Biological Engineering, Tufts University, 4 Colby Street, Medford, Massachusetts 02155, USA.
authors.forename: Vassilis
authors.initials: V
authors.lastname: Karageorgiou
authors.forename: Michael
authors.initials: M
authors.lastname: Tomkins
authors.forename: Robert
authors.initials: R
authors.lastname: Fajardo
authors.forename: Lorenz
authors.initials: L
authors.lastname: Meinel
authors.forename: Brian
authors.initials: B
authors.lastname: Snyder
authors.forename: Katherine
authors.initials: K
authors.lastname: Wade
authors.forename: Jake
authors.initials: J
authors.lastname: Chen
authors.forename: Gordana
authors.initials: G
authors.lastname: Vunjak-Novakovic
authors.forename: David L
authors.initials: DL
authors.lastname: Kaplan
mesh_terms: D000327:Adsorption; D000818:Animals; D001672:Biocompatible Materials; D012831:Bombyx; D001854:Bone Marrow Cells / Q000166:cytology*; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D004343:Drug Implants; D005349:Fibroins / Q000737:chemistry*; D006801:Humans; D007457:Iodine Radioisotopes; D051379:Mice; D010012:Osteogenesis / Q000187:drug effects; D053495:Osteopontin; D016062:Porosity; D012795:Sialoglycoproteins / Q000032:analysis / Q000235:genetics; D047011:Silk; D012887:Skull Fractures / Q000628:therapy; D017154:Stromal Cells / Q000166:cytology* / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology
chemical_list: C525718:BMP2 protein, human; D001672:Biocompatible Materials; C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D004343:Drug Implants; D007457:Iodine Radioisotopes; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; D047011:Silk; C506896:Spp1 protein, mouse; D016212:Transforming Growth Factor beta; D053495:Osteopontin; D005349:Fibroins