Neonatal Subventricular Zone Neural Stem Cells Release Extracellular Vesicles that Act as a Microglial Morphogen

Area of Science:

• Neuroscience
• Cell Biology
• Developmental Biology

Background:

• Subventricular zone (SVZ) neural stem cells (NSCs) are crucial for perinatal neurogenesis.
• Microglia, the resident immune cells, are abundant in the neonatal SVZ and interact with NSCs.
• The bidirectional communication between SVZ NSCs and microglia is not fully understood.

Purpose of the Study:

• To investigate the role of extracellular vesicles (EVs) in mediating communication between SVZ NSCs and microglia.
• To identify the molecular cargo within EVs and their functional impact on microglia.

Main Methods:

• SVZ NSCs were identified as producers of EVs.
• EVs released by NSCs were tracked in vivo using fluorescent fusion proteins.
• Small RNA sequencing was employed to profile miRNA content of EVs.
• Microglial morphology and transcriptional changes post-EV treatment were analyzed.

Main Results:

• SVZ NSCs generate and release EVs that are taken up by microglia.
• EVs contain miRNAs that modulate microglial physiology and morphology, inducing a non-stellate phenotype (CD11b/Iba1+).
• EVs trigger a microglial transcriptional state with Let-7-regulated cytokine release, establishing a feedback loop controlling NSC proliferation.

Conclusions:

• A novel NSC-EV-microglia communication axis is identified in the neonatal brain.
• This axis plays a significant role in regulating neurogenesis and microglial function.
• Findings offer insights into normal brain development and potential pathophysiological mechanisms.