413 Quantitative morphometric analysis of intrinsic and extrinsic ageing in Caucasian individuals

Abstract

Introduction: The field of skin ageing is important due to the world ageing population. Due to its interface with the external environment, skin ageing is attributed to both intrinsic and extrinsic factors. The aim of this study was to define histomorphic disparities between intrinsically and extrinsically aged skin, and increase understanding of how skin structures change with age and photoexposure. Methods: Full-thickness skin biopsies were obtained from the photoexposed dorsal forearm and photoprotected buttock of young (21-24 years, n=10 females) and aged Caucasian volunteers (61-65 years, n=10 females). Biometrics analysis of epidermal thickness (Emin), epidermal proliferation, basal keratinocyte morphology, interdigitation index and morphology of rête ridges and dermal papilla was performed on blinded histological and immunofluorescence images (n=40 biopsies; n=160-240 images). Results: Our study found that Emin and epidermal proliferation do not change with age or photoexposure (P>0.05). The size and height of basal keratinocytes is increased by photoexposure in young and ageing individuals, but no differences were identified with age (P<0.0001). The dermal-epidermal junction is affected by both age and photoexposure with regards to decreased interdigitation and decreased height of rête ridges and dermal papilla (P<0.0001). Discussion: Our data suggest that basal keratinocyte morphology is affected by photoexposure, and dermal-epidermal junction characteristics are altered by age and photoexposure. Interestingly, flattening of the dermal-epidermal junction was most apparent in photoexposed areas, and we propose that there is an accelerated ageing phenotype due to the contribution of extrinsic factors. These data are important for both academic and industrial scientists to validate in vitro findings, and identify targets for cosmetic interventions.