Macrophages derived from human induced pluripotent stem cells (iPSCs) serve as a high-fidelity cellular model for investigating HIV-1, dengue, and influenza viruses
Macrophages are important target cells for diverse viruses, and thus represent a valuable model system for studying virus biology. Isolation of primary human macrophages is done by culture of dissociated tissues or from differentiated blood monocytes, but these methods are both time consuming and result in low numbers of recovered macrophages. Here, we explore whether macrophages derived from human induced pluripotent stem cells (iPSCs)—which proliferate indefinitely and potentially provide unlimited starting material— could serve as a faithful model system for studying virus biology. Human iPSC-derived monocytes were differentiated into macrophages and then infected with HIV-1, dengue virus, or influenza virus as model macrophage-tropic human viruses. We show that iPSC-derived macrophages supported the replication of these viruses with similar kinetics and phenotypes to human blood monocyte-derived macrophages. These iPSC-derived macrophages were virtually indistinguishable from human blood monocyte-derived macrophages based on surface marker expression analysis (flow cytometry), transcriptomics (RNA-seq), and chromatin accessibility profiling (ATAC-seq) approaches. iPSC lines were additionally generated from nonhuman primate (chimpanzee) fibroblasts. When challenged with dengue virus, human and nonhuman primate iPSC-derived macrophages show differential susceptibility to infection, thus providing a valuable resource for studying the species-tropism of viruses. Collectively, our results substantiate iPSC-derived macrophages as an alternative to blood monocyte-derived macrophages for the study of virus biology. Overall design: We differentiated human iPSCs into hematopoietic stem progenitor cells (HSPCs), then differentiated those HSPCs into monocytes. Monocytes were loosely adherent to the HSPCs  and were readily harvested by gentle washing of the cell monolayer with growth media every 4-5 days, followed by media replacement for continued growth.  We next confirmed that iPSC derived monocytes could differentiate into macrophages and polarize into phenotypically distinct subtypes. Adherent monocytes were treated with macrophage colony stimulating factor for four days to generate naïve macrophages. M0 macrophages were then polarized into M1 or M2 subsets using interferon-gamma and lipopolysaccharide or interleukin-4, respectively. To examine whether blood- and iPSC-derived macrophages exhibit similar transcriptional profiles, we carried out transcriptomic and chromatin accessibility analyses of all cell types during differentiation and subsequent polarization via RNA-sequencing (RNA-seq) and Assay for Transposase-Accessible Chromatin-sequencing (ATAC-seq).