Peripherally derived macrophages infiltrate the brain after bone marrow transplantation and during central nervous system (CNS) inflammation. It was initially suggested that these engrafting cells were newly derived microglia and that irradiation was essential for engraftment to occur. However, it remains unclear whether brain-engrafting macrophages (beMs) acquire a unique phenotype in the brain, whether long-term engraftment may occur without irradiation, and whether brain function is affected by the engrafted cells. In this study, we demonstrate that chronic, partial microglia depletion is sufficient for beMs to populate the niche and that the presence of beMs does not alter behavior. Furthermore, beMs maintain a unique functional and transcriptional identity as compared with microglia. Overall, this study establishes beMs as a unique CNS cell type and demonstrates that therapeutic engraftment of beMs may be possible with irradiation-free conditioning regimens. SOURCE: Christopher Overall University of Virginia

Pluto Bioinformatics

GSE84819: Peripherally derived macrophages can engraft the brain independent of irradiation and maintain an identity distinct from microglia