Directed differentiation of human pluripotent stem cells to microglia

Microglia, the immune cells of the brain, are crucial to proper development and maintenance of the central nervous system, and their involvement in numerous neurological disorders is increasingly being recognized. To improve our understanding of human microglial biology, we devised a chemically defined protocol to generate human microglia from pluripotent stem cells. Myeloid progenitors expressing CD14/CX3CR1 were generated within 30 days of differentiation from both embryonic and induced pluripotent stem cells (iPSCs). Further differentiation of the progenitors resulted in ramified microglia with highly motile processes, expressing typical microglial markers. Analyses of gene expression and cytokine release showed close similarities between iPSC-derived (iPSC-MG) and human primary microglia as well as clear distinctions from macrophages. iPSC-MG were able to phagocytose and responded to ADP by producing intracellular Ca2+ transients, whereas macrophages lacked such response. The differentiation protocol was highly reproducible across several pluripotent stem cell (PSC) lines. Comparison of human pluripotent stem cell derived microglia to human primary microglia, human primary hepatic macrophages and peripheral blood derived macrophages non-polarized or polarized with IFN-γ and LPS, IL-4 and IL-13 or IL-10.