Engineering scaffold-free bone tissue using bone marrow stromal cell sheets.

The use of exogenous scaffolds to engineer bone tissue faces several drawbacks including insufficient biological activity, potential immunogenicity, elevated inflammatory reaction, fluctuating degradation rate, and low cell-attachment efficiency. To circumvent these limitations, we sought to engineer large scaffold-free bone tissue using cell sheets. We harvested intact cell sheets from bone marrow stromal cells using a continuous culture method and a scraping technique. The cell sheets were then rolled and fabricated into large constructs. Finally, the constructs were implanted into the subcutaneous pockets of nude mice. The cells within the sheet maintained in vitro osteogenic potential after osteoblast differentiation. Computed tomography scans and histological examination confirmed new bone formation in vivo. Additionally, the engineered bone exhibited enhanced compressive strength. Our results indicate that the BMSC sheets can facilitate the formation of functional three-dimensional bone tissue without the use of exogenous scaffolds. Hence, the study provides an intriguing alternative strategy for bone repair. Copyright (c) 2009 Orthopaedic Research Society.