Evaluation of heterotopic bone formation induced by squalane and bone morphogenetic protein composite

Bone morphogenetic protein is an important molecule whose bioactivity depends on the carrier. Squalane is used in the formulation of various kinds of cosmetics because it is easily emulsified and has the property of spreading well. Thus, squalane might be effective as a bone morphogenetic protein delivery system. As a test for this possibility, gelatin capsules containing squalane and bone morphogenetic protein (bovine derived partially purified) composite were implanted under the hind-quarter perimuscular membrane of ddY mice. Control capsules containing only bone morphogenetic protein were used for controls. The implants were radiographically and histologically examined at 1 to 4 weeks after the operation. According to the radiographic analysis, squalane and bone morphogenetic protein composite and bone morphogenetic protein only control specimens formed widespread heterotopic bone tissues. The amount of heterotopic bone formation in the composite experimental specimens was approximately 40% greater than that in the controls. Histologic examination of experimental and control specimens revealed varying amounts of perichondral ossification by 2 weeks. By 3 and 4 weeks, the bone deposits were colonized by hematopoietic bone marrow. Squalane was effective for the slow local release of bone morphogenetic protein. Furthermore, the squalane and bone morphogenetic protein composite was a reliable osteoinductive biomaterial.