In Vivo Evaluation of Commercially Available Gel-Type Polyethylene Glycol Membrane for Carrier of Recombinant Human Bone Morphogenetic Protein-2

Abstract

This study evaluated a commercially available, 3-dimensional gel-type polyethylene glycol (PEG) membrane as a carrier for recombinant human bone morphogenetic protein-2 (rhBMP-2) using a rat calvarial defect model. Another gel-type carrier, fibrin-fibronectin system (FFS), was used as a positive control. Critical-size defects were made in the rat calvarium, which were allocated to 1 of 10 groups comprising 2 healing periods and biomaterial conditions: 1) sham control, 2) FFS only, 3) FFS plus BMP-2, 4) PEG only, and 5) PEG plus BMP-2. Radiographic and histologic analyses were performed at 2 and 8weeks after surgery. After 2weeks, some parts of the FFS were biodegraded and extensive cellular infiltration was observed at sites that received FFS or FFS plus BMP-2. The PEG membrane retained its augmented volume without cellular infiltration at sites that received PEG or PEG plus BMP-2. After 8weeks, the FFS was completely degraded and replaced by new bone and connective tissues. In contrast, the volume of residual PEG was similar to that at 2weeks, with slight cellular infiltration. In particular, there was progressive bone regeneration around micro-cracks and resorbed outer surface in the PEG+ BMP-2 group. Although the PEG+ BMP-2 group showed increased area and percentage of new bone, there was no statistical relevance after 2 and 8weeks in histomorphometric analyses. However, the appearance of the healing differed (with new bone formation along micro-cracks in the PEG+ BMP-2 group), and further studies with longer healing periods are needed to draw conclusions about clinical applications. Evidence of mechanical stability and new bone formation along micro-cracks when using PEG plus BMP-2 might support the PEG membrane as a candidate carrier material for rhBMP-2.