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Updated: Mar 16, 2026
Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury
Published on: September 4, 2013
Dynamic Modulation of Microglia/Macrophage Polarization by miR-124 after Focal Cerebral Ischemia
Somayyeh Hamzei Taj1, Widuri Kho1, Markus Aswendt1
1In-vivo-NMR Laboratory, Max Planck Institute for Metabolism Research, Gleuelerstrasse 50, D-50931, Köln, Germany.
Abstract:
Mononuclear phagocytes respond to ischemic stroke dynamically, undergoing an early anti-inflammatory and protective phenotype followed by the pro-inflammatory and detrimental type. These dual roles of microglia/macrophages suggest the need of subtle adjustment of their polarization state instead of broad suppression. The most abundant brain-specific miRNA, miR-124, promotes neuronal differentiation but can also modulate microglia activation and keeps them in a quiescent state. We addressed whether the intracerebral injection of miR-124 in a mouse model of ischemic stroke before or after the peak phase of the pro-inflammatory polarization modifies the pro-/anti- inflammatory balance. In the sub-acute phase, 48 h after stroke, liposomated miR-124 shifted the predominantly pro-inflammatory polarized microglia/macrophages toward the anti-inflammatory phenotype. The altered immune response improved neurological deficit at day 6 after stroke. When miR-124 was injected 10 days after stroke, the pro-/anti- inflammatory ratio was still significantly reduced although to a lower degree and had no effect on recovery at day 14. This study indicates that miR-124 administration before the peak of the pro-inflammatory process of stroke is most effective in support of increasing the rehabilitation opportunity in the sub-acute phases of stroke. Our findings highlight the important role of immune cells after stroke and the therapeutic relevance of their polarization balance.
Insights
MicroRNA-124 (miR-124) therapy during the sub-acute phase of ischemic stroke reduces detrimental inflammation. Early miR-124 administration promotes neurological recovery by shifting immune cell polarization.
Area of Science:
- Neuroscience
- Immunology
- Molecular Biology
Background:
- Mononuclear phagocytes, including microglia/macrophages, exhibit dynamic polarization in ischemic stroke, transitioning from protective to detrimental phenotypes.
- Microglia/macrophages play dual roles in stroke, necessitating precise modulation of their inflammatory state rather than broad suppression.
- MicroRNA-124 (miR-124), a brain-specific microRNA, influences neuronal differentiation and microglia quiescence.
Purpose of the Study:
- To investigate the therapeutic potential of intracerebral miR-124 administration in a mouse model of ischemic stroke.
- To determine if miR-124 injection timing (before or after the pro-inflammatory peak) affects immune cell polarization and neurological recovery.
Main Methods:
- Ischemic stroke induced in a mouse model.
- Intracerebral injection of liposomated miR-124 at different time points post-stroke (sub-acute vs. later phase).
- Assessment of microglia/macrophage polarization (pro-inflammatory vs. anti-inflammatory balance) and neurological deficit evaluation.
Main Results:
- Liposomated miR-124 administered 48 hours after stroke shifted microglia/macrophages towards an anti-inflammatory phenotype.
- This shift in immune response led to improved neurological deficit by day 6 post-stroke.
- Delayed miR-124 injection (10 days post-stroke) showed a lesser reduction in the pro-/anti-inflammatory ratio and no significant effect on recovery at day 14.
Conclusions:
- miR-124 administration is most effective when given before the peak of the pro-inflammatory response in the sub-acute phase of ischemic stroke.
- Modulating the polarization balance of immune cells, particularly microglia/macrophages, holds therapeutic relevance for stroke rehabilitation.
- Targeting immune cell polarization with miR-124 offers a promising strategy to enhance recovery opportunities in the sub-acute phase of stroke.
