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 demonstrated ability to support bone formation, in vitro and in vivo. In this study, we investigated a range of silk scaffolds for bone TE using human adipose-derived stem cells (hASC), 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 (250–500μm vs. 500–1000μm) 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 hASC and cultured for 7 weeks in osteogenic media. Bone formation was evaluated by cell proliferation and differentiation, matrix production, calcification and mechanical properties. We observed that 400–600μm 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.

Silk fibroin/cartilage extracellular matrix scaffolds with sequential delivery of TGF-β3 for chondrogenic differentiation of adipose-derived stem cells

“…12,13 Thus, ADSCs as seeded cells are widely used for cartilage tissue engineering. [14][15][16] Chondrocyte-related growth factors such as transforming growth factor β, 17 bone morphogenetic proteins, 18 and insulin-like growth factor 19 play a critical role in developing an appropriate microenvironment in cartilage tissue engineering. 20 However, the uncontrolled delivery of these factors may decrease their full reparative potential and have unwanted morphological effects.…”

Distinctive Capillary Action by Micro-channels in Bone-like Templates can Enhance Recruitment of Cells for Restoration of Large Bony Defect

“…Most of these approaches have resulted in the in vitro tissue ingrowth with cross-sections of less than a few µm to several mm from the external surface, an incomplete integration with host bone, and only partial bone regeneration in vivo . Therefore, it is clear that the architecture of the scaffolds (pore size, porosity, interconnectivity, and permeability) that affect the transport and diffusion of substances throughout the scaffolds is critical for achieving well-distributed cell proliferation and differentiation 9,10 . Although calcium phosphates have been used in the past for scaffold fabrication, different processes and procedures have often resulted in calcium phosphate scaffolds with varying architectures.…”

Degradability, biocompatibility, and osteogenesis of biocomposite scaffolds containing nano magnesium phosphate and wheat protein both in vitro and in vivo for bone regeneration

“…17 It is known that scaffolds for bone tissue regenerations play an important role in influencing the biological responses of cells (including attachment, proliferation, differentiation, etc) and the following new bone tissue formation (scaffolds entirely degraded) in vivo. 18,19 In this study, MWC scaffolds were fabricated using solution casting-particle leaching method. The results revealed that the MWC scaffolds exhibited a well-interconnected macroporous structure, and some micropores were found on the wall of the macropores.…”