Ferdos Ali¹

1 – Newcastle University, UK. Supervisor: Professor Mark Birch-Machin

Background: Variation in skin colour is the most noticeable of human polymorphisms yet skin’s primary functions of maintaining homeostasis, defence against environmental insults (solar ultraviolet radiation, pollution, ozone). Historically, skin biology research has mostly focussed on white Northern European skin. However, from limited research on more pigmented skin it is apparent that there are differences in facial ageing appearance and response to environmental stressors. Therefore, it is imperative that we understand the fundamental biology of skin across the entire spectrum of pigmentation.

Aims: Investigating how external stressors such as sun exposure affect skin ageing in different skin types.

Methods: Cell viability of skin cells including epidermal melanocytes and dermal fibroblasts was assessed 24 hours after exposure to increasing doses of a full solar spectrum using MTS assays. In addition to fibroblast cell line (HDFn), non-pigmented A375 and moderately pigmented FM55 human melanoma cell lines were used to represent differently pigmented skin cells. Irradiation was carried out using Newport oriel solar simulator with 1000W output. Doses of the solar light were expressed as standard erythemal doses (SEDs).

Results: All three cell lines showed a significant decrease in cell viability as the doses of the full solar increased despite cell type or pigmentation level. However, non-pigmented A375 and mildly pigmented FM55 cell lines were shown to be more resistant to the irradiation than HDFns as the 2.16 SED led to 50% reduction in the cell viability of the fibroblasts whereas it caused around 35% reduction in the cell viability of the melanocytes.

Conclusion: Exposure to increasing doses of solar light negatively affects the cell viability of skin cells despite their type or level of pigmentation. Overall, this suggests that photoprotective measures should be taken regardless of the skin type.