Prediction, screening and characterization of novel bioactive tetrapeptide matrikines for skin rejuvenation

Background Extracellular matrices play a critical role in tissue structure and function and aberrant remodelling of these matrices is a hallmark of many age-related diseases. In skin, loss of dermal collagens and disorganization of elastic fibre components are key features of photoageing. Although the application of some small matrix-derived peptides to aged skin has been shown to beneficially affect in vitro cell behaviour and, in vivo, molecular architecture and clinical appearance, the discovery of new peptides has lacked a guiding hypothesis.Objectives To identify, using protease cleavage site prediction, novel putative matrikines with beneficial activities for skin composition and structure.Methods Here, we present an in silico (peptide cleavage prediction) to in vitro (proteomic and transcriptomic activity testing in cultured human dermal fibroblasts) to in vivo (short-term patch test and longer-term split-face clinical study) discovery pipeline, which enables the identification and characterization of peptides with differential activities.Results Using this pipeline we showed that cultured fibroblasts were responsive to all applied peptides, but their associated bioactivity was sequence-dependent. Based on bioactivity, toxicity and protein source, we further characterized a combination of two novel peptides, GPKG (glycine-proline-lysine-glycine) and LSVD (leucine-serine-valine-aspartate), that acted in vitro to enhance the transcription of matrix -organization and cell proliferation genes and in vivo (in a short-term patch test) to promote processes associated with epithelial and dermal maintenance and remodelling. Prolonged use of a formulation containing these peptides in a split-face clinical study led to significantly improved measures of crow's feet and firmness in a mixed population.Conclusions This approach to peptide discovery and testing can identify new synthetic matrikines, providing insights into biological mechanisms of tissue homeostasis and repair and new pathways to clinical intervention. Like other organs and tissues, the skin is composed of both cells and a complex network of molecules and proteins called an extracellular matrix. This matrix contains proteins such as collagen and elastin and undergoes many changes when the skin is damaged by the sun. We know from previous studies that small parts of matrix proteins (called peptide 'matrikines') can help to treat the signs of sun-related skin ageing.In this UK study, we show that new beneficial peptides (with matrikine activity) can be identified using machine learning (artificial intelligence) techniques that predict where common matrix proteins might be 'cut' by skin enzymes. Candidate peptides were first made in the laboratory and then applied to skin cells in culture. These cell culture screens demonstrated that, while all the peptides showed some matrikine activity, two were particularly promising. These two peptides were then tested in a short-term study on the forearm skin of volunteers and, in a longer-term study, on the face. We found that the combination of these two peptides can prompt forearm skin cells to express genes that are involved in many different aspect of skin health and, over the longer 6-month period, produce visible benefits in the appearance of fine lines and wrinkles and firmness on the face.Our findings suggest that this approach may be able to identify beneficial peptide treatments for not only skin ageing and diseases, but also unwanted changes in the extracellular matrix of other tissues and organs. Graphical Abstract Prediction, screening and characterization of skin bioactive peptides. (1) In silico cleavage site prediction for common skin proteases acting on dermal extracellular matrix proteins identifies a panel of small peptides as candidate matrikines. (2) Synthesis and in vitro screening against cultured human dermal fibroblasts results in the selection of two candidate peptides: GPKG and LSVD. (3) In vivo screening demonstrates efficacy of the peptide combination in restoring fibrillin-1 in the papillary dermis and enhancing the transcription of genes involved in key epidermal and dermal processes.