Oligogalacturonides improve tissue organization of in vitro reconstructed skin

The aim of this study was to analyse the effects of oligogalacturonides obtained from apple pectin enzymatic hydrolysis (mainly composed of galacturonic acid and oligogalacturonides; OGA) on normal human keratinocytes behaviour using different in vitro models. We demonstrate that 0.01% OGA promotes epidermal growth, organization and stratification in an in vitro reconstructed skin. The presence and the in vivo-like location of epidermal differentiation markers (i.e. keratin 10, involucrin, desmoglein 1 and 3, and cathepsin D) confirms the histological analysis, and underlines the cohesion of the treated epidermis. On the opposite, 0.05% OGA delays epidermal growth and disturbs differentiation, showing that the positive effects of OGA are dependent on its concentration. In parallel, using collagen IV and laminin 332 substrates, two relevant components of dermal-epidermal basement membrane, we demonstrate that the presence of 0.01% OGA clearly stimulates keratinocytes spreading out, paralleled by a well-organized microfilament network. Keratinocytes develop more focal adhesions with the substrates, implicating α6β4 on laminin 332. Cellular cohesion is also promoted by 0.01% OGA through the over-expression of integrins α2β1 on collagen IV, and α3β1 on laminin 332 at cell-cell junctions. Thus, by modulating integrins expression and organization, OGA 0.01% should improve cell-cell interactions and therefore dermal-epidermal cohesion. In conclusion, 0.01% OGA stimulates epidermal spreading and promotes keratinocytes attachment to basement membrane components by reorganizing cytoskeleton and modulating integrins recruitment. Furthermore, 0.01% OGA promotes epidermal differentiation and regulates epidermis homeostasis. Considering that OGA has a beneficial effect on parameters playing a key role in ageing, OGA can be presented as a new anti-ageing active ingredient.