MORE EFFORTS FOR TISSUE-ENGINEERING SKIN

Abstract

A251 Aims: Submit a review of Tissue-engineering skin, and provide new sight for future efforts. Reviews: Requirements for functions of tissue-engieering skin are resemblance to native human skin including three aspects: protection, perception and regulation. Protective function consists of barrier, UV light absorption, immune surveillance and mechanical stability. There are some permeability differences between artificial skin and native skin which may be ascribed to the different composition and ultrastructure of stratum corneum(SC) lipids, and absence of hair. The UV light absorption ability has a direct ratio with the pigmentation of healed cultured skin substitutes, which is frequently irregular and unpredictable. Paracrine factors from skin cells and the extracellular matrix act as local environmental signals for the the pigmentation which is proportional to growth density of melanocytes. Immune surveillance requires the complete engraftment of native skin cells and a functional vascular plexus which the available artificial skin lacks. Many factors contribute to inevitable contraction of cultured skin substitutes, such as the effect of keratinocytes and fibroblasts, thickness of dermis, immaturity of the dermal-epidermal junction and materials. The perception and regulation functions have almost been studied only in experiments because of difficult transplantation of necessary elements like touch domes and skin appendages. Immune rejection is the main reason for limitting the popularity of allogeinic grafts. In the process immune cells, cytokines and blood supply work. CD80 on keratinocytes might bring the ultimate rejection of allogeneic keratinocytes. The host inflammatory response to some extents acts as a more significant role than immune reaction. Prospects: Tissue-engineering skin needs further developments. This may be achieved through improvement of culture conditions. crosslink agents, certain cytokines, phorbol ester and vitamine C can be added to culture medium to enhance mechanical stability of artificial skin and accelerate its formation. Perfection of cultured skin substitutes requires complete engraftment of the celluar part and a functional vascular plexus which may conflict with requirement of diminishing antigenicity. Here improvement of culture condition appears to be significant through which cells can move from the peripheral healthy region without transplantion. Stem cell is another attractive topic. Due to the difficult acquirement and culture, a stem cell bank can be built. Skin is perhaps the most accessible of all somatic tissues for therapeutic gene transfer. Gene therapy for cultured skin grafts develops quickly. The goal includes accelerating wound healing and curing diseases and the key is how to prolong expression of the transfected gene. As artificial skin makes a transition from research to clinical practice, the uniform criterions for qualitative and quantitative analysis of cultured skin substitutes must be established for evaluation of materials, composition, performance and safety.Figure