Regeneration of the femoral epicondyle on calcium-binding silk scaffolds developed using transgenic silk fibroin produced by transgenic silkworm

Genetically modified silk fibroin containing a poly-glutamic acid site, [(AGSGAG)4E8AS]4, for mineralization was produced as fibers by transgenic silkworms through systematic transformation of the silkworms. The Ca binding activity and mineralization of the transgenic silk fibroin were examined in vitro, showing that this transgenic silk fibroin had relatively high Ca binding activity compared with native silk fibroin. Porous silk scaffolds were prepared with the transgenic and native silk fibroins. Healing of femoral epicondyle defects in rabbit femurs treated with the scaffolds was examined by observing changes in images of the defects using micro-computed tomography. Earlier mineralization and bone formation were observed with scaffolds of transgenic silk fibroin compared with those of native silk fibroin. Thus, this study shows the feasibility of using genetically modified silk fibroin from transgenic silkworms as a mineralization-accelerating material for bone repair.