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Updated: Aug 16, 2025
Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury
Published on: September 4, 2013
Role of post-ischemic phase-dependent modulation of anti-inflammatory M2-type macrophages against rat brain damage
Yoshitaka Kurashiki1, Hiroshi Kagusa1, Kenji Yagi1
1Department of Neurosurgery, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan.
Abstract:
Cerebral ischemia triggers inflammatory changes, and early complications and unfavorable outcomes of endovascular thrombectomy for brain occlusion promote the recruitment of various cell types to the ischemic area. Although anti-inflammatory M2-type macrophages are thought to exert protective effects against cerebral ischemia, little has been clarified regarding the significance of post-ischemic phase-dependent modulation of M2-type macrophages. To test our hypothesis that post-ischemic phase-dependent modulation of macrophages represents a potential therapy against ischemic brain damage, the effects on rats of an M2-type macrophage-specific activator, Gc-protein macrophage-activating factor (GcMAF), were compared with vehicle-treated control rats in the acute (day 0-6) or subacute (day 7-13) phase after ischemia induction. Acute-phase GcMAF treatment augmented both anti-inflammatory CD163+ M2-type- and pro-inflammatory CD16+ M1-type macrophages, resulting in no beneficial effects. Conversely, subacute-phase GcMAF injection increased only CD163+ M2-type macrophages accompanied by elevated mRNA levels of arginase-1 and interleukin-4. M2-type macrophages co-localized with CD36+ phagocytic cells led to clearance of the infarct area, which were abrogated by clodronate-liposomes. Expression of survival-related molecules on day 28 at the infarct border was augmented by GcMAF. These data provide new and important insights into the significance of M2-type macrophage-specific activation as post-ischemic phase-dependent therapy.
Insights
Targeting M2-type macrophages during the subacute phase after cerebral ischemia shows therapeutic potential. Activating these macrophages with Gc-protein macrophage-activating factor (GcMAF) promotes infarct clearance and enhances survival molecules.
Area of Science:
- Neuroscience
- Immunology
- Regenerative Medicine
Background:
- Cerebral ischemia induces inflammation and cell recruitment to the affected brain area.
- The role of M2-type macrophages in cerebral ischemia is not fully understood, particularly their phase-dependent modulation.
- Endovascular thrombectomy complications can worsen outcomes in brain occlusion.
Purpose of the Study:
- To investigate the therapeutic potential of post-ischemic phase-dependent M2-type macrophage modulation.
- To evaluate the effects of Gc-protein macrophage-activating factor (GcMAF) on ischemic brain damage in rats.
Main Methods:
- Rats were treated with GcMAF or vehicle during the acute (days 0-6) or subacute (days 7-13) phase after ischemia induction.
- Macrophage phenotypes (M1/M2) and gene expression (arginase-1, interleukin-4) were analyzed.
- Phagocytic activity and expression of survival molecules were assessed.
Main Results:
- Acute GcMAF treatment increased both M1 and M2 macrophages without beneficial effects.
- Subacute GcMAF treatment selectively increased M2 macrophages, upregulating arginase-1 and interleukin-4.
- M2 macrophages facilitated infarct clearance, and GcMAF enhanced survival-related molecules at the infarct border.
Conclusions:
- Subacute-phase M2-type macrophage activation is crucial for mitigating ischemic brain damage.
- GcMAF shows promise as a phase-dependent therapy for cerebral ischemia by promoting M2 macrophage polarization and infarct clearance.
