Background: Using recent advances in tissue engineering and the principles behind the prefabrication of flaps, the goal of this project was to induce bone growth in a prefabricated capsular flap. From previous experiments on prefabrication and prelamination of different cell types, including urothelial cells, tracheal epithelial cells, and chondrocytes, we have found that transposing a vascular pedicle to a subcutaneously placed silicone block will result in a vascular capsule that can be mobilized and transferred based solely on the pedicle. The capsule provides the necessary blood supply for cell growth.

Methods and Materials: Using a rat model, a capsular flap was created (n=10). At two weeks, the silicone block was removed, and mesenchymal stem cells cultured from processed lipoaspirate and rhBMP (bone morphogenic protein) were inserted in the capsular flap to promote osteoinduction (n=5). Rats with mesenchymal stem cells inserted into the capsule without rhBMP served as the control group (n=5). Eight weeks later, the rats were sacrificed and examined for gross, radiologic, and histologic evidence of bone growth.

Results: The combination of mesenchymal stem cells and rhBMP induced more bone growth within the capsule than mesenchymal stem cells alone when specimens were examined grossly, radiologically, and histologically.

Conclusions: The use of rhBMP and mesenchymal stem cells within a vascularized capsular flap may represent important prelimary steps in designing an ideal construct for tissue-engineered bone. The ultimate goal is to provide a technique to reconstruct bony defects by using a composite tissue flap engineered at a distant location and in a specific shape and then transferred to the site of the defect.