Keratin Scaffold Formulation Impacts rhBMP-2 Biodistribution and Bone Regeneration in a Rat Femur Defect Model

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Orthopedic Surgery

Background:

• Nonunion in long bones is a significant clinical challenge.
• Current collagen-based carriers for bone morphogenetic protein 2 (BMP-2) face limitations due to rapid resorption and uncontrolled release.
• Keratin proteins offer tunable degradation rates for controlled therapeutic delivery.

Purpose of the Study:

• To investigate keratin-based scaffolds as a novel carrier for recombinant human bone morphogenetic protein 2 (rhBMP-2).
• To evaluate the efficacy and safety of keratin scaffolds in a rat femur nonunion model.
• To compare keratin scaffolds with traditional collagen carriers.

Main Methods:

• Two keratin forms, kerateine (KTN) and keratose (KOS), were used to create freeze-dried scaffolds with varying ratios.
• Scaffolds were loaded with rhBMP-2 and implanted into critical-sized rat femur defects.
• Bone regeneration, rhBMP-2 retention, and systemic distribution were assessed using micro-computed tomography (μ-CT) and fluorescence imaging.

Main Results:

• A 50:50 KOS:KTN formulation demonstrated equivalent bone bridging, mineral density, and volume to collagen scaffolds at 8 weeks.
• Keratin scaffolds (50:50 KOS:KTN and 100% KTN) exhibited fourfold higher retention of rhBMP-2 at the implant site compared to collagen.
• Increased local retention of rhBMP-2 in keratin scaffolds correlated with reduced levels in distal organs, indicating improved safety.

Conclusions:

• Keratin scaffolds are effective in promoting bone regeneration comparable to collagen carriers.
• Keratin-based carriers offer an improved safety profile due to controlled release and enhanced local retention of rhBMP-2.
• These findings support the potential of keratin scaffolds for treating long bone nonunions.