Direct reprogramming of fibroblasts into functional macrophages [RNA-Seq]

Macrophages derived from somatic cells by reprogramming technologies have the potential to enable the development of cell-based therapies for numerous malignant diseases. Here we report on the establishment of a novel methodology allowing for the conversion of fibroblasts into functional macrophages with pro-inflammatory phenotype just by c-Myc overexpression. Ectopic expression of c-Myc in fibroblasts in induced pluripotent stem cell (iPSC) culture medium induced the rapid appearance of CD45+ hematopoietic cell complex (HCC) intermediates with engraftment capacity as well as the repopulation of distant hematopoietic compartments. HCC intermediates were stably maintained in suspension culture and continuously generated functional and highly pure-induced macrophage (iMac) just by M-CSF cytokine stimulation. Single-cell transcriptomic analysis of HCC intermediates revealed that c-Myc up-regulates the expression of MafB, a major regulator of macrophage differentiation, to promote macrophage differentiation. Characterization of the macrophage activity showed NF-kB signaling activation and pro-inflammatory phenotype. iMac transplantation significantly reduced leukemia and breast cancer progression in animal xenograft models. Our finding indicates that reprogramming strategies of fibroblasts could help circumvent long-standing obstacles to gaining “off-the-shelf” macrophages for anti-cancer immunotherapy.