O19 Using an immune-responsive human skin equivalent ageing model to dissect cutaneous immune ageing

Introduction and aims Skin ageing is associated with visible phenotypical changes such as wrinkling. On a cellular level, the number of senescent cells accumulates with age, which can drive skin ageing phenotype. During ageing, there are also profound changes in cutaneous immunity which render older adults more susceptible to skin cancers and infections. We have previously shown that skin from older adults (≥ 65 years) has impaired antigen-recall response against pathogens. This age-associated impairment is due to recruitment of proinflammatory monocytes by activated senescent fibroblasts, these monocytes secret prostaglandin E2 and blunt antigen-specific immunity. However, the mechanisms of senescent fibroblast activation that induces the recruitment of inflammatory monocytes are currently unknown. Owing to ethical limitations of performing repeated biopsies on humans, a novel ageing skin model needs to be developed. The aim of this project is to build immune responsive ‘young’ and ‘old’ in vitro three-dimensional human skin equivalent (HSE) model to identify the cellular source of this age-associated skin inflammation. Methods We have built ‘young’ (100% proliferating fibroblasts) and ‘old’ (10% senescent; 90% proliferating) HSEs. The dermal fibroblasts were isolated from sun-protected healthy human skin, and N/TERTs were employed for the epidermis. Furthermore, we established immune-responsive HSEs with the addition of monocytes isolated from fresh peripheral blood to the dermal layer. Results The ‘old’ HSEs exhibited epidermal thinning and ECM disorganization. Additionally, the increase of senescent fibroblast percentage within the HSE dermis is associated with further impairment of epidermal development. The monocytes within the HSEs differentiated into dermal macrophages as defined by CD68 expression. Conclusions We have developed HSEs that recapitulate human skin ageing. Research is ongoing to determine the influence of the old skin environment on mononuclear phagocyte differentiation. This project will aid our understanding of age-related cutaneous immune decline, and ultimately, the identification of druggable pathways to help improve skin health in older adults.