Cytokine exposure of human macrophages induces disease-associated microglia transcriptional signatures

Myeloid cells including brain-resident macrophages (microglia) and peripheral macrophages play a crucial role in various pathological conditions, including neurodegenerative diseases such as Alzheimer's disease (AD). They adapt to extracellular stimuli by acquiring various transcriptional states. Understanding of how these states are regulated is limited due to a lack of tools that enable robust reprogramming toward disease-associated phenotypes. In this study, we investigated the effects of a cytokine mix, including interleukin-4 (IL-4), colony stimulating factor 1 (CSF1/M-CSF), interleukin 34 (IL-34) and transforming growth factor beta (TGFß), on human THP-1 macrophages to elucidate their potential reprogramming towards disease-associated phenotypes and subsequential functional changes. Our results indicate that treatment with the cytokine mix led to significant transcriptomic changes, driving human THP-1 macrophages towards a transcriptional state reminiscent of disease-associated microglia (DAM) and lipid-associated macrophages (LAM) collectively referred to as DLAM. Transcriptome profiling revealed gene expression changes related to oxidative phosphorylation, lysosome function, and lipid metabolism. Single-cell RNA sequencing revealed the activation of DLAM-like transcriptional responses across multiple cell clusters. Functional assays demonstrated alterations in macrophage motility, phagocytosis, lysosomal activity, and metabolic and energetic profiles. Our findings provide insights into the cytokine-mediated reprogramming of macrophages towards disease-relevant states, highlighting their role in neurodegenerative diseases and potential for therapeutic development. Overall design: Human THP-1 monocytic leukemia line was differentiated to macrophages and treated with 1) three factors (3F): IL34, MCSF, TGFb; 2) IL4; 3) mix of 3F and IL4 (MIX): IL34, MCSF, TGFb, IL4. Control THP-1 macrophages were not treated (NT). Concentration of each cytokine in every treatment IL34 100ng/ml, TGFb 50ng/ml, MCSF 25ng/ml, IL4 20ng/ml