Immunohistochemical characterization of guided bone formation by a biodegradable tissue engineering scaffold in a healing tooth socket of a rabbit model

We have developed a novel, biocompatible, biodegradable tissue engineering scaffold that has been shown to facilitate bone formation in vivo. The process of bone formation within this scaffold, however, is unknown at a molecular level. To study this process, a rabbit's four healing incisor sockets (two mandibular and two maxillar) that remain after tooth extraction were used as a bone defect model. One socket was left empty, while the remaining three were filled with crosslinked polymer networks formed from either the hydrophobic polymer poly(propylene fumarate) (PPF), the hydrophilic oligomer oligo(poly(ethylene glycol) fumarate) (OPF), or PPF with adsorbed transforming growth factor - β1 (PPF+TGF-β1). At 4 days, 1 week, 2 weeks, 4 weeks, 8 weeks, and 16 weeks both the mandible and maxilla were removed and prepared for histological analysis. Using immunohistochemical techniques, frozen sections were stained for the presence of TGF-β1, platelet derived growth factor (PDGF), fibroblast growth factor - 2 (FGF-2), vascular endothelial growth factor (VEGF), and bone morphogenetic protein - 2 (BMP-2). Results indicate the effect of differing biomaterial properties upon bone formation as described by the spatial and temporal development of those growth factors thought to be intimately involved in the process.