Bone morphogenic protein expression and bone formation are induced by bioactive glass S53P4 scaffolds in vivo

The two-stage induced-membrane (IM) technique isincreasingly used for treatment of large bone defects. In stageone, the bone defect is filled with polymethylmethacrylate(PMMA), which induces a membrane around the implant. Instage two, PMMA is replaced with bone graft. Bioactiveglasses (BAGs) are bone substitutes with bone-stimulating andangiogenic properties. We have previously shown that a cer-tain type of BAG can also induce a foreign-body membranesimilar to PMMA. The aim of this study was to evaluate thebone-forming capacity of sintered BAG-S53P4 andpoly(lactide-co-glycolide) (PLGA)-coated BAG-S53P4 scaffoldsfor potential use as bone substitutes in a single-stage IM tech-nique. Sintered porous rods of BAG-S53P4, BAG-S53P4-PLGA,or PMMA were implanted in rabbit femurs for 2, 4, or 8 weeks.The expression of bone morphogenic protein (BMP)-2, -4, and-7 in the IMs of implanted materials were analyzed with real-time quantitative polymerase chain reaction. Micro-computedtomography imaging was used to evaluate bone growth andfurther verified with scanning electron microscopy. BAG-S53P4 and BAG-S53P4-PGLA scaffold IMs show similar orsuperior expression of BMP-2, -4, and -7 compared with PMMAIM. Bone ingrowth into BAG scaffolds increased over time.Active bone formation occurred inside the BAG scaffolds andthe respective BMP expressions were similar or superior forthe BAG IMs compared with PMMA, thus making BAGs apromising device for single-stage treatment of bone defects.