The effects of silk sheets derived from germ-free silkworms on wound healing of full-thickness epithelial defects

Collagen is widely used as a scaffold for full-thickness epithelial defects but has poor biostability and often induces hypertrophic scarring. Silk, especially silk derived from germ-free silkworms (SGFS), has high biocompatibility and controllable durability. Therefore, SGFS is possibly for medicine. Herein, we evaluated the effects of SGFS as a scaffold in the wound healing of full-thickness epithelial defects. Epithelial defects were made in the dorsal skin of C57BL/6 J mice, and an SGFS or a collagen sheet was applied to each defect and compared. On days 1, 3, 7, and 14 after surgery, re-epithelialization, inflammatory responses, and granulation tissue formation of each wound were assessed and compared between the groups. Re-epithelialization was observed in the SGFS group on day 3 but no re-epithelialization occurred in the collagen group. Histopathological examination showed less granulation tissue formation in the SGFS group than in the collagen group. IL-6 expression was significantly higher in the SGFS group than in the collagen group on day 1. TGF-β1 expression in the SGFS group was significantly lower than that in the collagen sheet group on days 7 and 14. Based on these results, SGFS promoted re-epithelialization and reduced hypertrophic scarring in the wound healing process compared with collagen.