Evaluation of Senescence Induced Prematurely by Stress. Application for cosmetic active ingredients

Living cells are continuously subject to all sorts of stress such as ultraviolet rays on skin cells. Tests made in various laboratories show that when young fibroblasts (Le. at the beginning of their proliferate life) were repeatedly put under stress at subletal doses, they acquired a phenotype similar to Senescence Induced Prematurely by Stress (SIPS). The work presented hereafter was made on a new model of senescence induced prematurely by stress from ultraviolet Brays (UVB). The human fibroblast model was put under repeated UVB stress, causing SIPS. Several ageing biomarkers were used in order to characterise the cells that underwent stress:. an increase in the proportion of positive cells with senescence associated $\beta$-galactosidase activity (SA $\beta$-gal) measured by a specific coloration,. the proportion in the different morphological stages that fibroblasts undergo during culture visualised by microscopic observation,. the expression of genes known for overexpressing during senescence, particularly fibronectin and apolipoprotein J, measured by Real Time-PCR,. the common deletion of 4,977 bp in mitochondrial DNA, evaluated by nested PCR. Studying the variation of these 4 biomarkers, we have evaluated the protective effect of a Laminaria digitata extract (LDE) that can be used as a natural active ingredient for anti-ageing cosmetics.