Photoageing describes complex cutaneous changes that occur over time due to chronic exposure to solar radiation. In lightly pigmented skin, photoageing is associated with solar elastosis and disintegration of the well-organised elastic fibre network containing fibrillin-rich microfibrils (FRMs). Our recent work in skin of colour has identified loss of FRM in chronically photoexposed skin, without overt solar elastosis. As topical retinoids are used as the clinical ‘gold standard’ for the treatment of white photoaged skin we wished to investigate their potential for dermal remodelling, particularly of FRM, in chronically photoexposed black skin. Here, we use the Manchester Patch-Test Assay to examine the histological effects of topical 0.025% all-trans retinoic acid (RA) applied to the extensor forearm (under occlusion) in healthy but photoaged white (n = 3; mean age: 70 years) and photoaged black (n = 3; mean age: 67 years) volunteers. After 96 hours, 3mm skin biopsies were obtained and processed for histological assessment. Treatment with RA produced significant epidermal thickening across both cohorts (P < 0.001) as compared to untreated baseline control skin; flattening of the dermal-epidermal junction (DEJ) persisted despite application of RA. Further analyses revealed that following RA treatment there was a doubling of keratinocyte cell layers (P < 0.001) with each individual keratinocyte having an increased area (P < 0.01). In addition, topical RA induced restoration of the FRM network at the DEJ regardless of skin type (P = 0.02). This pilot study confirms that topical RA has significant effects not only on keratinocyte morphology, but also on the distribution of FRMs. Deposition of FRMs following RA treatment suggests that topical retinoids may be beneficial in the treatment of photoageing in black skin. Further investigation of the mechanisms that underpin this repair is warranted.

Retinoids in the treatment of skin photoageing: A histological study of topical all-trans retinoic acid efficacy in black skin