Induction of granulation tissue for the secretion of growth factors and the promotion of bone defect repair

BACKGROUND The use of the Masquelet technique in the repair of large bone defects has gained increased acceptance in recent years. The core of this technique is the induction of granulation tissue membrane formation and the implantation of an autologous cancellous bone to reconstruct bone defects in the membrane. In this study, we purpose to explore the structure of induced membrane and the content of growth factors as well to compare between the structure and the effects on osteogenesis of induced membranes and the periosteum in animal models. METHODS Bilateral radial bone defects were generated in 32 healthy adult rabbits. The defects were implanted with bone cement. The induced membranes and periosteum were removed after 2, 4, 6, and 8 weeks. Thereafter, hematoxylin-eosin staining (HE) and an enzyme-linked immunosorbent assay (ELISA) were performed to detect vascular endothelial growth factor (VEGF), angiotensin II (ANG-II), bone morphogenetic protein 2 (BMP2), fibroblast growth factor 2 (FGF2), and prostaglandin E2 (PGE2). Proteins isolated from total cell lysates were cultured with mesenchymal stem cells to test the cell proliferation and alkaline phosphatase activity using epimysium as a control. RESULTS The induced membrane and periosteum exhibited similar structures and growth factor levels after 4 and 6 weeks. The highest concentration of BMP-2 and VEGF in the induced membranes occurred in week 6, and FGF-2 and ANG-II concentrations peaked in week 4. The thickness and vascular density of induced membranes gradually decreased with time. CONCLUSION Induced membrane matured between the 4th and the 6th week and secreted growth factors to promote osteogenesis. The matured induced membrane and periosteum had similar structures and abilities to promote the osteogenesis of mesenchymal stem cells. However, the induced membrane was thicker than the periosteum.