Functional bilayered skin substitute constructed by tissue-engineered extracellular matrix and microsphere-incorporated gelatin hydrogel for wound repair.

Our aim in this study was to develop a new methodology for constructing a bilayer skin equivalent to create a clinically compliant skin graft composite for the treatment of various skin defects. We utilized tissue-engineered extracellular matrix (TEECM) that maintains the native dermal components, as analogical dermal layer, and gelatin hydrogel containing epidermal growth factor (EGF)-loaded microspheres, as epidermis layer upon TEECM. The bilayer skin equivalent (GG-EGF/TEECM) could be synthesized appropriately and has been hypothesized to provide an enhanced effect on re-epithelization, apart from dermal reconstruction improved by TEECM. Morphological properties, EGF release efficiency, cytotoxicity, and effects on wound repair of this composite were investigated in this study. It was shown that the two layers adhered firmly to each other, and the percentage of cumulative release was approximately 80% by day 14. Moreover, as a biocompatible equivalent, GG-EGF/TEECM improved the healing of the wound area as indicated by significantly earlier re-epithelialization and dermal maturation. These results suggest that GG-EGF/TEECM can provide an optimal microenvironment and proper template for skin tissue engineering.