Investigating the consequences of primary and paracrine-driven secondary senescence for melanocyte function in 2D and 3D living skin equivalents

There is compelling evidence that senescence drives ageing. Senescence has been extensively investigated in fibroblasts, whose increased presence in skin has been linked to advanced skin ageing (e.g. wrinkles, aged elastin) and pigmented spots (e.g. melasma). The consequences of primary melanocyte senescence is comparatively underexplored but very recent evidence indicates it is the dominant senescent cell in the skin epidermis (Victorelli et al., 2019 EMBO in press). In addition, how senescent fibroblast and melanocytes effect normal pigmentation and the ageing phenotype is relatively unknown. We have developed a 3D adult, human living skin equivalent (LSE) that faithfully reproduces the dermis and a stratified epidermis. The inclusion of 10% (physiologically relevant) senescent HDFs produced a significant decrease in epidermal thickness and fundamentally changed the transcriptome of non-senescent HDFs within the dermis (via single cell RNAseq; scRNAseq), suggesting that primary senescence and paracrine-driven secondary senescence are distinct endpoints. We aim to explore the consequences of senescence on melanocyte and keratinocyte function in 2D and 3D.