Figure 1. A method for producing human iPSC-derived microglia and transplanting them into mice.

During the production stage (top left), embryoid bodies derived from human iPSCs (induced pluripotent stem cells; pink) develop into myeloid precursors, which then differentiate into microglia (green cells) after exposure to a cocktail of cytokines (IL-34, CSF1, TGFβ, and Cx3cl1). The microglia derived from the iPSCs express typical microglia markers (such as Cx3cr1, P2ry12, CD11b, and CD68). During the confirmation stage (top right), the properties of the microglia are validated through a combination of gene profiling, comparative Gene Pathway Analysis, phagocytosis assays (which probe the ability of the microglia to engulf particles coated with bacterial proteins), and xenotransplantation (which involves transplanting the microglia into the subretinal space of adult mice; bottom right). Xenotransplantation is followed by the repopulation stage (bottom left), in which the microglia derived from the iPSCs become integrated and distributed across the different retinal layers in a pattern consistent with endogenous microglia (red cell). GCL: ganglion cell layer; INL: inner nuclear layer; ONL: outer nuclear layer; RPE: retinal pigment epithelium.