Metformin inhibits IFN-g-mediated activation of macrophages in necrobiotic xanthogranuloma

This study included lesional and non-lesional skin samples of patients diagnosed with NXG as well as control skin (non-involved, discarded skin obtained during dermatologic surgical non-melanoma skin cancer removal) from otherwise healthy donors. Skin samples of NXG were obtained for diagnostic purposes at the Department of Dermatology at the University Hospital of Cologne. Trained dermatologists histologically and clinically confirmed NXG or healthy skin. Skin tissues were immediately stored in RNAlater (invitrogen, AM7020). 30 µg of tissue stored in RNAlater was mechanically homogenized using a pre-cooled RETSCH MM 400 mixer mill (Thermo Fischer, 10573034). RNA from homogenized tissue was isolated using the RNeasy Fibrous Tissue Kit (Qiagen, 74704) according to the manufacturer´s protocol. This study was conducted according to the principles expressed in the Declaration of Helsinki and approved by the local Ethic Committee (Ethikkommission) of the University of Cologne (votes #20-1082 and #19-1146). All donors participated voluntarily and provided written informed consent for collecting samples and subsequent analyses.