Experimental induction of heterotopic bone in abdominal implants

Induction of bone tissue requires three elements: osteoprogenitor cells, osteoinductive factors, and a supporting extracellular matrix. In this study, we report on an experimental model in dogs of heterotopic bone tissue production, based on the integration of these osteo-inductive factors into abdominal implants. The implants consist of either a type I collagen sponge wrapped with periosteum and omentum or a type I collagen sponge embedded with demineralized bone powder, platelet-rich plasma, thrombin, and calcium chloride wrapped with omentum, with or without periosteum. Automated histomorphometric analysis showed an efficient production of trabecular bone, which corresponded to 50-70% of the total tissue composition 4 months after implant formation. High expression of the osteoinductive cytokines transforming growth factor-beta and bone morphogenetic proteins-2 and -4 was shown by immunohistochemistry in macrophages, endothelial cells from neoformed capillaries, osteoblasts, osteoclasts, and the mesenchymal tissue around the bone trabeculae. These approaches are novel and efficient surgical procedures to produce mature trabecular bone that could be used as a potential source of bone tissue for autotransplantation.