Guoping Chen, and Naoki Kawazoe at the Tissue Regeneration Materials Unit, International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science, and researchers at RIKEN, the Immuno-Biological Laboratories Co., Ltd, and the National Institute for Child Health and Development added a collagen-binding domain from fibronectin to BMP4, a protein that promotes bone regeneration. The new fusion protein, BMP4-CBD, was immobilized in a hybrid scaffold of natural collagen sponge and a strong synthetic polymer, poly(lactic-co-glycolic acid) (PLGA). The hybrid scaffold provides space and support for the bone cell growth.

The researchers investigated the effect of BMP4-CBD immobilized in the collagen-PLGA scaffold by in vivo implantationfor four weeks. They compared the approach with a range of controls including scaffolds with wild-type BMP4 without the collagen-binding domain and scaffolds with just the collagen-binding domain. The expression of specific osteogenetic markers used as indicators of bone tissue regeneration was much higher for BMP4-CBD-immobilized hybrid scaffolds. Using BMP4-CBD also promoted calcification.

"These effects should be attributed to the retention of more effective molecules due to the specific binding of the fusion BMP4 to the collagen," say the authors. The stimulation effect of the protein promoting the bone regeneration is thus maintained over a longer period. The research may benefit patients suffering from bone defects in the future.