The human bone marrow harbors a CD45^- CD11B⁺ cell progenitor permitting rapid microglia-like cell derivative approaches

Microglia, the immune sentinel of the central nervous system (CNS), are generated from yolk sac erythromyeloid progenitors that populate the developing CNS. Interestingly, a specific type of bone marrow-derived monocyte is able to express a yolk sac microglial signature and populate CNS in disease. Here we have examined human bone marrow (hBM) in an attempt to identify novel cell sources for generating microglia-like cells to use in cell-based therapies and in vitro modeling. We demonstrate that hBM stroma harbors a progenitor cell that we name stromal microglial progenitor (STR-MP). STR-MP single-cell gene analysis revealed the expression of the consensus genetic microglial signature and microglial-specific genes present in development and CNS pathologies. STR-MPs can be expanded and generate microglia-like cells in vitro, which we name stromal microglia (STR-M). STR-M cells show phagocytic ability, classically activate, and survive and phagocyte in human brain tissue. Thus, our results reveal that hBM harbors a source of microglia-like precursors that can be used in patient-centered fast derivative approaches.