Scaffolds for epidermal tissue engineering

The epidermis is the outermost layer of the skin, which otherwise comprises two additional layers, namely the dermis and hypodermis. The main function of the epidermis is to provide a barrier that prevents foreign agents, including chemicals and biological pathogens, from entering the body while preventing excessive fluid loss. The epidermis mainly consists of keratinocytes, but it also contains small numbers of melanocytes that provide skin pigmentation, Merkel cells that act as mechanotransducers to touch, and immune competent cells. After skin injury, restoration of a continuous epidermis defines wound closure. Although the ability of the epidermis to spontaneously repair is much greater than that of the dermis, therapeutic interventions to promote epidermal restoration are beneficial when large areas of skin are damaged, such as in extensive burns, or in cases of chronic nonhealing wounds (e.g., diabetic foot ulcers). Epidermal tissue engineering strategies have focused primarily on promoting the regeneration of the stratified keratinocyte layers to restore barrier function, which is crucial for long-term survival. Various biologically active wound coverings and scaffold materials have been developed for this purpose. These materials, which provide a physical substrate that supports cell migration, are also often designed to release soluble factors (e.g., growth factors and chemokines) and therapeutic agents. These factors may target epidermal cells directly, or indirectly by promoting dermal repair and revascularization, which is critical for providing a sufficient nutritional supply to the epidermis. In this chapter, we summarize the scaffold types, properties, and materials used to promote epidermal regeneration.