Characterization of human monocytic cell line THP-1 associated with human 3D skin models under UVA exposure

Tissue resident macrophages play important roles in tissue homeostasis and acute response to external stimuli. Human skin equivalents (HSEs) incorporating human monocytic cell line THP-1, were fabricated to generate immunocompetent human skin models. These HSEs were used to investigate the influence of the skin microenvironment and UVA exposure on the phenotypes of macrophages. THP-1 in HSEs exhibited mixed M1 and M2 macrophage phenotypes. Transcriptomic analysis demonstrated that THP-1 in HSEs enriched extracellular matrix interaction while downregulated a DNA replication hallmark. Upon UVA exposure, immunocompetent HSEs exhibited epidermal distortion and increased DNA double-strand breaks (DSB). THP-1 isolated from UVA-exposed HSEs revealed significant upregulation of genes associated with oxidative stress, antioxidant regulation, inflammatory and UV response. A photoprotective agent, mycosporine-2-glycine (M2G), derived from cyanobacteria was applied on to immunocompetent HSEs and the responses of THP-1 cell line was investigated after UVA exposure. The result showed that UVA-induced DSB was significantly lower in M2G-treated HSEs. In addition, the inflammatory and UV response hallmarks were downregulated while the oxidative phosphorylation hallmark was upregulated in THP-1 from M2G-treated UVA exposed HSEs. Taken together, this study provides an immunocompetent 3D skin model that can be used to interrogate responses of skin resident innate immune cells to microenvironment and external stimuli such as UVA irradiation.