Efficient conversion of human induced pluripotent stem cells into microglia by defined transcription factors

Microglia, the immune cells of the central nervous system (CNS), play critical roles in brain physiology and pathology. We report a novel approach that produces within ten days the differentiation of human induced pluripotent stem cells (hiPSCs) into microglia (iMG) by forced expression of both SPI1 and CEBPA. High-level expression of the main microglial markers and the purity of the iMG cells were confirmed by RT-qPCR, immunostaining and flow cytometry analyses. Whole transcriptome analysis demonstrated that these iMGs resemble human fetal/adult microglia but not human monocytes. Moreover, these iMGs exhibited appropriate physiological functions, including various inflammatory responses, ADP/ATP-evoked migration and phagocytic ability. When co-cultured with hiPSC-derived neurons (iNs), the iMGs respond and migrate toward injured neurons. This study has established a protocol for the rapid conversion of hiPSCs into functional iMGs, which should facilitate functional studies of human microglia using different disease models and also help with drug discovery. Transcriptomal profile of iMGs from two hiPS cell lines in independent triplication, comparing with RNA-seq data of human adult microglia, human fetal primary microglia, CD14+ monocytes and hiPSC-derived microglia obtained using other differentiation protocols downloaded from NCBI GEO (GSE89189 and GSE110952)