Modulation of gene expression and bone formation by expanded and dense polytetrafluoroethylene membranes during guided bone regeneration: An experimental study.

Abstract

Nonresorbable membranes promote bone formation during guided bone regeneration (GBR), yet the relationships between membrane properties and molecular changes in the surrounding tissue are largely unknown. To compare the molecular events in the overlying soft tissue, the membrane, and the underlying bone defect during GBR using dual-layered expanded membranes versus dense polytetrafluoroethylene (PTFE) membranes. Rat femur defects were treated with either dense PTFE (d-PTFE) or dual-layered expanded PTFE (dual e-PTFE) or left untreated as a sham. Samples were collected after 6 and 28 days for gene expression, histology, and histomorphometry analyses. The two membranes promoted the overall bone formation compared to sham. Defects treated with dual e-PTFE exhibited a significantly higher proportion of new bone in the top central region after 28 days. Compared to that in the sham, the soft tissue in the dual e-PTFE group showed 2-fold higher expression of genes related to regeneration (FGF-2 and FOXO1) and vascularization (VEGF). Furthermore, compared to cells in the d-PTFE group, cells in the dual e-PTFE showed 2.5-fold higher expression of genes related to osteogenic differentiation (BMP-2), regeneration (FGF-2 and COL1A1), and vascularization (VEGF), in parallel with lower expression of proinflammatory cytokines (IL-6 and TNF-α). Multiple correlations were found between the molecular activities in membrane-adherent cells and those in the soft tissue. Selective surface modification of the two sides of the e-PTFE membrane constitutes a novel means of modulating the tissue response and promoting bone regeneration.