Decorin interacts with collagen via its protein core and influences collagen fibrillogenesis, thus regulating excessive bundle-like aggregation of collagen. As skin ages, there is lack of functional decorin, which results in disrupted collagen fibres and in a reduction in the tensile strength of the skin. Therefore, a substitute for decorin would make up for the non-functional decorin that is present as we age. Two tetrapeptide sequences have been identified as the specific binding sites of decorin to collagen fibrils. These sequences were engineered to generate new tetrapeptides with improved affinity that would present a decorin-like activity. A focused library of several candidates was synthesized containing only tetrapeptides that mimicked the binding sequences of decorin. The candidates were screened with an in vitro collagen fibrillogenesis assay and the tetrapeptide with International Nomenclature of Cosmetic Ingredients (INCI) name Tripeptide-10 Citrulline achieved the best results. Like decorin, this synthetic tetrapeptide proved, through in vitro tests, to regulate collagen fibrillogenesis and to influence the diameter of collagen fibres, making them thinner and more uniform. Tripeptide-10 Citrulline is a new cosmetic active to target specifically collagen fibre organization. Skin collagen quality is addressed rather than skin collagen quantity. Tripeptide-10 Citrulline ensures uniformity in fibril diameter and increases skin suppleness because of a better cohesion of collagen fibres.
