title: Development of silk-based scaffolds for tissue engineering of bone from human adipose-derived stem cells.
abstract: Silk fibroin is a potent alternative to other biodegradable biopolymers for bone tissue engineering (TE), because of its tunable architecture and mechanical properties, and its demonstrated ability to support bone formation both in vitro and in vivo. In this study, we investigated a range of silk scaffolds for bone TE using human adipose-derived stem cells (hASCs), an attractive cell source for engineering autologous bone grafts. Our goal was to understand the effects of scaffold architecture and biomechanics and use this information to optimize silk scaffolds for bone TE applications. Silk scaffolds were fabricated using different solvents (aqueous vs. hexafluoro-2-propanol (HFIP)), pore sizes (250-500 μm vs. 500-1000 μm) and structures (lamellar vs. spherical pores). Four types of silk scaffolds combining the properties of interest were systematically compared with respect to bone tissue outcomes, with decellularized trabecular bone (DCB) included as a "gold standard". The scaffolds were seeded with hASCs and cultured for 7 weeks in osteogenic medium. Bone formation was evaluated by cell proliferation and differentiation, matrix production, calcification and mechanical properties. We observed that 400-600 μm porous HFIP-derived silk fibroin scaffold demonstrated the best bone tissue formation outcomes, as evidenced by increased bone protein production (osteopontin, collagen type I, bone sialoprotein), enhanced calcium deposition and total bone volume. On a direct comparison basis, alkaline phosphatase activity (AP) at week 2 and new calcium deposition at week 7 were comparable to the cells cultured in DCB. Yet, among the aqueous-based structures, the lamellar architecture induced increased AP activity and demonstrated higher equilibrium modulus than the spherical-pore scaffolds. Based on the collected data, we propose a conceptual model describing the effects of silk scaffold design on bone tissue formation.
authors.affiliation: Laboratory for Stem Cells and Tissue Engineering, Department of Biomedical Engineering, Columbia University, Vanderbilt Clinic, NY 10032, USA.
authors.forename: Cristina
authors.initials: C
authors.lastname: Correia
authors.forename: Sarindr
authors.initials: S
authors.lastname: Bhumiratana
authors.forename: Le-Ping
authors.initials: LP
authors.lastname: Yan
authors.forename: Ana L
authors.initials: AL
authors.lastname: Oliveira
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Gimble
authors.forename: Danielle
authors.initials: D
authors.lastname: Rockwood
authors.forename: David L
authors.initials: DL
authors.lastname: Kaplan
authors.forename: Rui A
authors.initials: RA
authors.lastname: Sousa
authors.forename: Rui L
authors.initials: RL
authors.lastname: Reis
authors.forename: Gordana
authors.initials: G
authors.lastname: Vunjak-Novakovic
mesh_terms: D000273:Adipose Tissue / Q000166:cytology*; D000818:Animals; D012831:Bombyx; D001842:Bone and Bones / Q000187:drug effects* / Q000502:physiology*; D002417:Cattle; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D039902:Multipotent Stem Cells / Q000166:cytology; D010012:Osteogenesis / Q000187:drug effects; D010641:Phenotype; D047011:Silk / Q000494:pharmacology*; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000648:ultrastructure; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds / Q000737:chemistry*
chemical_list: D047011:Silk