P40 Photoageing-induced differences to the dermoepidermal junction proteome and associated basement membrane of the skin

Introduction and aims Photoageing presents with coarse wrinkles, laxity, abnormal pigmentation and functional decline in resilience and healing. Histologically, it is associated with flattening of the dermoepidermal junction (DEJ) and loss of major proteins such as collagen VII. However, the effects of photoageing on the wider network remain unknown. This study aimed to define these changes and identify DEJ biomarker candidates of photoageing, by spatial and structural proteomics. Methods DEJ-enriched samples of buttock (intrinsically aged) and forearm (photoaged) skin (N = 3, mean age 66 years, Fitzpatrick type I–III) were collected with laser-capture microdissection (∼20 µm either side of the DEJ), then analysed with liquid chromatography-tandem mass spectrometry. Differential abundance, principal component (PCA), and gene set variation (GSVA) analyses were performed, alongside peptide location fingerprinting (PLF). Results PCA reveals separation of buttock and forearm samples, demonstrating markedly different DEJ proteomic compositions between photoaged and intrinsically aged skin. GSVA of extracellular matrix proteins revealed a fold increase of core basement membrane (BM) proteins and proteoglycans in photoaged skin, these being the main protein classes impacted. Three proteins have significantly higher (Padj < 0.1) relative abundances in photoaged skin: vitronectin, collagen XIVα1, and serum amyloid P-component. PLF identified 198 proteins (intracellular and extracellular) with significant differences in peptide yield across protein structures, including 20 BM-associated proteins. Affected protein regions within plectin and integrin α6 and β4 subunits coincide with interaction sites for intermediate filaments and keratins-14/15, and extracellular and cytoplasmic regions respectively, revealing a potential dysregulation in basal keratinocyte attachment of the underlying BM. Collagen-VIIα1 exhibited differences within the NC1 domain and triple helical region, and cathepsin-D also harboured differences within the heavy chain, suggesting BM-specific damage. Conclusions Overall, using spatial proteomics we reveal photoageing-specific degeneration of the wider DEJ network, particularly in major components associated with epidermal attachment.