[Use of growth factors in the repair of bone]

Osteoformation is induced by numerous growth factors that play an important role in bone repair such as fracture healing. They may serve as therapeutic agent in the treatment of squeletal injuries in the orthopeadic and maxillo-facial fields. Among these proteins, Bone Morphogenetic Proteins (BMP) are the only known osteoinductive growth factors. Unfortunately, they are highly susceptible to proteolysis in vivo and require a suitable delivery system to potentiate their biological activity in a local, controlled and durable manner. In this aim, three options are under investigations: (i) osteoinductive materials made of appropriate carrier to release the protein in situ, (ii) in vivo gene therapy in which the gene is directly transfected in cells of the patient or (iii) ex vivo gene therapy in which cells are harvested from the patient, transfected with DNA in culture and then implanted in the defect. These different kinds of BMP delivery will be discussed.