Glycated Reconstructed Human Skin as a Platform to Study the Pathogenesis of Skin Aging

The advanced glycation end products (AGEs) of proteins are common factors in the pathophysiology of a number of disorders related to aging. The skin generation of AGEs occurs mainly through nonenzymatic glycation reactions of extracellular matrix (ECM) proteins in the dermis. The AGEs have been touted as one of the factors responsible for healing impairment and loss of elasticity of healing skin, affecting growth, differentiation, and cellular motility, as well as cytokines response, metalloproteinases expression, and vascular hemostasis. In this study, we generated an in vitro full-thickness reconstructed skin based on a glycated collagen matrix dermal compartment to evaluate the effects of glycation on dermal ECM and ultimately on the epidermis. Epidermal differentiation and stratification patterns and the glycation-induced ECM changes were evaluated by histology, immunohistochemistry, and mRNA levels. In this study, we reported for the first time that changes in the dermal matrix caused by collagen I in vitro glycation processes also affect the epidermal compartment. We demonstrated that glycation of collagen induces expression of carboxymethyllysine in dermal and epidermal compartments and, consequently, an aging phenotype consisting of poor stratification of epidermal layers and vacuolization of keratinocyte cytoplasm. Increased expression of cell-cell adhesion markers, such as desmoglein and E-cadherin in glycated skins, is observed in the stratum spinosum, as well as an increased compression of dermal collagen matrix. We also submitted our 3D model of reconstructed glycated skin to screening of anti-AGE molecules, such as aminoguanidine, which prevented the glycated morphological status. Controlled human studies investigating the effects of anti-AGE strategies against skin aging are largely missing. In this context, we proposed the use of skin equivalents as an efficient model to investigate cellular interactions and ECM changes in the aging skin, and to elucidate the role of anti-AGEs molecules in this process.