Patients affected by chronic venous insufficiency (CVI) and Lipodermatosclerosis present characteristic brown colouring of the lower legs due to iron overload, all together predisposing conditions of leg ulcer formation. Therefore, in this project, we aim to investigate the pathological effect of iron overload on the cross-talk of resident immune and tissue cells in the skin. At first, we collected skin samples of CVI patients and confirmed via immunohistochemistry (IHC) a massive accumulation of iron in the dermis. To dissect the response of macrophages to iron-overload we mimicked erythrocyte accumulation in the skin in vitro by co-culture of primary human M2-like macrophages with autologous erythrocytes. Gene expression microarray analysis revealed a shift in the gene signature towards inflammatory activation states and an upregulation of inflammatory pathways and iron-related genes. Hence, cytokine analysis confirmed a clear pro-inflammatory activation of macrophages (Ma) in ery-overload with an increased release of TNF, IL-6, IL-12, but decreased IL-10. In addition, we transferred conditional medium of erythrocyte-fed Ma to fibroblast (Fb) culture and found an enhanced proliferation accompanied with downregulation of typical genes related to extracellular matrix (ECM) production. Then, we generate a mouse model for local iron-overload, via intradermal injection of iron-dextran. Here, we confirmed that iron induces an expansion of immune cells and a pro-inflammatory activation in the skin with a shift in resident macrophage subtypes. IHC and IF staining of iron-mice skin showed increased cellularity of the lower dermis, which we linked to an expansion of the Fb population. Consistent with our in vitro data, we found ECM genes were downregulated in the dermis, which may explain changes in the skin architecture of these mice. In conclusion, our data suggest that local iron-overload cause a complex skin phenotype with a maintained inflammatory status, enhanced proliferation of immune and tissue cells, and a shift in resident Ma and Fb subtypes, which affects the cellular crosstalk in the skin and skin homeostasis.

ESDR213 - Iron overload in skin homeostasis

50th Annual Meeting of the European Society for Dermatological Research. VIRTUAL MEETING