Generation of microglial cells from mouse embryonic stem cells.

Microglia, the resident immune cells of the brain, are difficult to obtain in high numbers and purity using currently available methods; to date, microglia for experimental research are mainly isolated from the brain or from mixed glial cultures. In this paper, we describe a basic protocol for the in vitro differentiation of mouse embryonic stem (ES) cells into microglial precursor cells. Microglia are obtained by a protocol consisting of five stages: (i) cultivation of ES cells, (ii) formation and differentiation of embryoid bodies, (iii) differentiation into neuroectodermal lineage and isolation of myeloid precursor cells, (iv) differentiation into microglial precursor cells and (v) cultivation of ES cell-derived microglial precursors (ESdMs). The protocol can be completed in 60 d and results in stably proliferating ESdM lines, which show inducible transcription of inflammatory genes and cell marker expression comparable with primary microglia. Furthermore, ESdMs are capable of chemokine-directed migration and phagocytosis, which are major functional features of microglia.