The identification and the use of compounds which activate the expression of at least one gene selected from LARGE, HS6ST2 and ST8SIA1, for preventing and/or attenuating ageing, and/or for hydrating skin is provided. An in vitro method for screening for candidate compounds for preventing and/or attenuating ageing of the skin, and/or for hydrating the skin, includes the following steps:(a) bringing at least one test compound in contact with a sample of keratinocytes(b) measuring the expression of at least one gene selected from LARGE, HS6ST2 and ST8SIA1, in said keratinocytes(c) selecting the compounds for which an activation of at least 1.4 fold of the expression of at least one of said genes is measured in the keratinocytes treated in (a) compared with the untreated keratinocytes.
