Transport distraction osteogenesis with recombinant human bone morphogenic protein-2 for large calvarial defect reconstruction

Supramolecular self-assembling peptides to deliver bone morphogenetic proteins for skeletal regeneration

Recombinant human bone morphogenetic proteins (BMPs) have shown clinical success in promoting bone healing, but they are also associated with unwanted side effects. The development of improved BMP carriers that can retain BMP at the defect site and maximize its efficacy would decrease the therapeutic BMP dose and thus improve its safety profile. In this review, we discuss the advantages of using self-assembling peptides, a class of synthetic supramolecular biomaterials, to deliver recombinant BMPs. Peptide amphiphiles (PAs) are a broad class of self-assembling peptides, and the use of PAs for BMP delivery and bone regeneration has been explored extensively over the past decade. Like many self-assembling peptide systems, PAs can be designed to form nanofibrous supramolecular biomaterials in which molecules are held together by non-covalent bonds. Chemical and biological functionality can be added to PA nanofibers, through conjugation of chemical moieties or biological epitopes to PA molecules. For example, PA nanofibers have been designed to bind heparan sulfate, a natural polysaccharide that is known to bind BMPs and potentiate their signal. Alternatively, PA nanofibers have been designed to synthetically mimic the structure and function of heparan sulfate, or to directly bind BMP specifically. In small animal models, these bio-inspired PA materials have shown the capacity to promote bone regeneration using BMP at doses 10-100 times lower than established therapeutic doses. These promising results have motivated further evaluation of PAs in large animal models, where their safety and efficacy must be established before clinical translation. We conclude with a discussion on the possiblity of combining PAs with other materials used in orthopaedic surgery to maximize their utility for clinical translation.

Bone Transport Distraction Osteogenesis in the Reconstruction of Pediatric Posttraumatic Calvarial Defects

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Reconstruction of posttraumatic calvarial bone defects in pediatric patients is a challenge due to the growing brain and limited autogenous bone supply. Traditional techniques such as split calvarial and particulate bone grafts are associated with prolonged operative time and significant blood loss, which is a major concern in children under the age of 3 years. Bone transport distraction osteogenesis has proven efficacy and safety in the reconstruction of other craniofacial deformities. This procedure is less invasive and requires shorter operative times and hospital stay. We report our experience with 2 cases of bone transport distraction osteogenesis for the reconstruction of large posttraumatic calvarial defects in pediatric patients.

Off-Label Use of Bone Morphogenetic Protein 2 in the Reconstructions of Mandibular Continuity Defects

This paper describes 3 patients of off-label use of bone morphogenetic protein 2 (rhBMP-2) in the reconstruction of mandibular continuity defects. In the first patient, rhBMP-2 was associated with iliac crest bone graft for late mandibular reconstruction after resection of osteosarcoma. In the 2 other patients, rhBMP-2 was used alone. In 1 patient the mandibular continuity defect was due to resection for treatment of osteomyelitis and in the other patient a continuity defect was created by unsuccessful osteogenic distraction for correction of mandibular hypoplasia. Despite the good results in those patients, the off-label use of rhBMP-2 is associated with increased rate of complications, so more studies are needed to assess the predictability of the use of rhBMP-2 in mandibular continuity defects. Therefore, at the moment the off-label use of rhBMP-2 should be restricted to complicated bone defects in which the conventional alternatives of reconstruction were unsuccessful.