In Vivo Bone Formation Within Engineered Hydroxyapatite Scaffolds in a Sheep Model

Area of Science:

• Orthopedic surgery
• Biomaterials science
• Regenerative medicine

Background:

• Large bone defects pose significant orthopedic challenges, often necessitating bone grafting.
• Bone tissue engineering offers a promising alternative using scaffolds and cells to enhance bone repair.
• Optimizing cell distribution within scaffolds is crucial for successful bone formation.

Purpose of the Study:

• To engineer hydroxyapatite (HA)-based bone grafts with autologous bone marrow mesenchymal stem cells.
• To evaluate the in vivo osseointegration and bone formation in an ovine model.
• To compare the efficacy of dynamically cultured, statically cultured, and cell-free scaffolds at tibia and femur sites.

Main Methods:

• Seeding and culturing mesenchymal stem cells within HA scaffolds using a perfusion bioreactor.
• Implantation of engineered constructs into ovine tibia and femur defects.
• Assessment of bone formation and osseointegration using micro-computed tomography (micro-CT) and histological analyses at 2 and 4 months.

Main Results:

• Acellular HA grafts demonstrated osseointegration comparable to cell-loaded scaffolds (static and dynamic).
• Femur sites showed better bone repair capacity than tibia sites.
• Dynamically cell-loaded implants showed a slight advantage over cell-free or static grafts specifically in the tibia.

Conclusions:

• Hydroxyapatite-based bone grafts can achieve significant osseointegration without cell loading.
• The tibia exhibits a reduced capacity for bone repair compared to the femur.
• Dynamic cell-loading strategies may be beneficial for enhancing bone repair in challenging anatomical locations like the tibia.