# M2 macrophage-derived exosomes mitigate acute inflammation following ischemic stroke

## TL;DR

Exosomes from M2 macrophages reduce brain inflammation after stroke by suppressing harmful immune responses and improving recovery.

## Contribution

The study identifies miR-330-5p in M2 macrophage-derived exosomes as a novel anti-inflammatory mediator targeting Syk and Stat3 in stroke.

## Key findings

- M2-exo significantly reduced inflammation and brain injury in a mouse stroke model.
- miR-330-5p was specifically enriched in M2-exo and inhibited Syk and Stat3 expression in microglia.
- Inhibiting Syk or Stat3 mimicked the anti-inflammatory effects of miR-330-5p.

## Abstract

The acute inflammatory response following ischemic stroke is a key factor in exacerbating brain injury. Modulating excessive inflammation during the oxidative stress (OS) phase represents a potential therapeutic strategy; however, clinical interventions remain limited.

M0 and M2 macrophage-derived exosomes (M0-exo and M2-exo) were administered to microglia under oxygen–glucose deprivation/reperfusion (OGD/R) conditions and to mice subjected to transient middle cerebral artery occlusion (tMCAO). The mechanisms underlying their anti-inflammatory effects were then investigated through a combination of bioinformatic analysis and fundamental experiments.

Treatment with exosomes markedly suppressed the expression of pro-inflammatory factors. Furthermore, they significantly reduced cerebral infarct volume and improved neurological function in mice. Notably, the anti-inflammatory effect of M2-exo was significantly superior to that of M0-exo. miRNA sequencing and subsequent validation revealed a specific enrichment of miR-330-5p in M2-exo. Mechanistic studies have demonstrated that miR-330-5p suppresses the expression of Spleen tyrosine kinase (Syk) and signal transducer and activator of transcription 3 (Stat3) in microglia, consequently reducing the production of downstream inflammatory factors. Treatment with Syk or Stat3 inhibitors partially mimicked the anti-inflammatory action of miR-330-5p in rescue studies.

Our results unveil a novel anti-inflammatory pathway mediated by M2-exo, providing novel insights for stroke therapy.

Illustrated flowchart depicting a study on exosomes and their effects. Top left shows cell culture and ultracentrifugation to isolate exosomes, followed by quality control graphs and images. Middle left indicates exosome interaction with microglia, detailing reduced inflammatory markers like CD86 and TNF-α. Top right shows a mouse model with reduced brain infarction and improved behavior. Lower sections detail exosomal content, including miRNA-seq analysis, KEGG, GO pathways, and a heatmap. Bottom left describes miR-330-5p effects in the cytoplasm and nucleus, illustrating pathways involving Syk and Stat3, and gene expression changes.