Novel skin photoageing biomarkers of epidermis and dermis revealed by traditional relative quantification in combination with a novel peptide locational fingerprinting MPLF.

Human skin undergoes profound structural remodelling following chronic exposure to ultraviolet radiation (UVR) – photoageing - that is normally studied by comparing photoexposed and photoprotected skin sites. Whilst it is well established that the abundance and distribution of major dermal extracellular matrix (ECM) proteins (principally collagen I and elastin) are compromised in skin, the influence of UVR exposure on other skin protein constituents, including epidermal proteins, is poorly understood. We used label-free LC-MS/MS proteomics to characterise the proteomic profiles of intrinsically aged buttock and photoaged forearm epidermis and dermis. Besides traditional shotgun proteomics we have also developed and used novel proteomics analysis approach to reveal locational changes in peptide yields from proteins named Manchester Peptide Locational Fingerprinting (MPLF) which is based on spectral counting. MPLF is a new proteomic analysis tool that can identify structural modification-associated differences within proteins from label-free liquid chromatography tandem mass spectrometry (LC-MS/MS) datasets generated from biological samples. We have identified a total of 174 dermal proteins and 146 epidermal proteins with MPLF while relative quantification revealed a total of 635 dermal proteins and 926 epidermal proteins significantly different between photoaged forearm and intrinsically-aged buttock according to peak area intensity.