Location of Neonatal Microglia Drives Small Extracellular Vesicles Content and Biological Functions

Combining proteomics and systems biology analyses, we demonstrated that neonatal microglial cells derived from two different CNS locations (cortex and spinal cord) displayed different phenotypes upon different physiological or pathological conditions. These cells also exhibited great variability in terms of both cellular and small extracellular vesicles (sEVs) protein contents and levels. Bioinformatics data analysis showed that the cortical microglia had anti-inflammatory and neurogenesis/tumorigenesis properties, while the spinal cord microglia was rather involved in inflammatory response process. Of interest, while both sEVs microglia sources enhanced growth of DRGs axons, only the spinal cord-derived sEVs microglia under LPS stimulation significantly attenuated glioma proliferation. These results were confirmed through neurite outgrowth assays in DRGs cell line and glioma proliferation analysis in 3D spheroid cultures. Results from these in vitro assays indicated that the microglia localized at different CNS regions can ensure different biological functions. Together, these works indicate that neonatal microglia locations regulate their physiological and pathological functional fates, and could explain the high prevalence of brain vs. spinal cord glioma in adults.