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Updated: Aug 1, 2025
Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury
Published on: September 4, 2013
Characteristics of activation of monocyte-derived macrophages versus microglia after mouse experimental intracerebral
Fenghui Ye1, Jinting Yang1, Katherine G Holste1
1Department of Neurosurgery, University of Michigan, Ann Arbor, MI, USA.
Abstract:
Both monocyte-derived macrophages (MDMs) and brain resident microglia participate in hematoma resolution after intracerebral hemorrhage (ICH). Here, we utilized a transgenic mouse line with enhanced green fluorescent protein (EGFP) labeled microglia (Tmem119-EGFP mice) combined with a F4/80 immunohistochemistry (a pan-macrophage marker) to visualize changes in MDMs and microglia after ICH. A murine model of ICH was used in which autologous blood was stereotactically injected into the right basal ganglia. The autologous blood was co-injected with CD47 blocking antibodies to enhance phagocytosis or clodronate liposomes for phagocyte depletion. In addition, Tmem119-EGFP mice were injected with the blood components peroxiredoxin 2 (Prx2) or thrombin. MDMs entered the brain and formed a peri-hematoma cell layer by day 3 after ICH and giant phagocytes engulfed red blood cells were found. CD47 blocking antibody increased the number of MDMs around and inside the hematoma and extended MDM phagocytic activity to day 7. Both MDMs and microglia could be diminished by clodronate liposomes. Intracerebral injection of Prx2 but not thrombin attracted MDMs into brain parenchyma. In conclusion, MDMs play an important role in phagocytosis after ICH which can be enhanced by CD47 blocking antibody, suggesting the modulation of MDMs after ICH could be a future therapeutic target.
Insights
Monocyte-derived macrophages (MDMs) are crucial for clearing blood clots after intracerebral hemorrhage (ICH). Enhancing MDM phagocytosis with CD47 blocking antibodies shows therapeutic potential for ICH recovery.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Intracerebral hemorrhage (ICH) triggers inflammatory responses involving microglia and monocyte-derived macrophages (MDMs).
- Understanding the roles of these immune cells is key to developing effective treatments for ICH.
Purpose of the Study:
- To investigate the dynamic roles of MDMs and microglia in hematoma resolution post-ICH.
- To evaluate the impact of CD47 blockade and phagocyte depletion on immune cell infiltration and activity.
Main Methods:
- Utilized Tmem119-EGFP transgenic mice and F4/80 immunohistochemistry to track microglia and MDMs.
- Established a murine ICH model with autologous blood injection, co-administered with CD47 blocking antibodies or clodronate liposomes.
- Administered blood components (Prx2, thrombin) to assess their chemoattractant properties for MDMs.
Main Results:
- MDMs formed a peri-hematoma layer by day 3 post-ICH, with giant phagocytes observed.
- CD47 blockade increased MDM presence and phagocytic activity up to day 7.
- Clodronate liposomes reduced both MDMs and microglia.
- Peroxiredoxin 2 (Prx2) attracted MDMs into the brain parenchyma.
Conclusions:
- MDMs play a significant role in phagocytosis during ICH hematoma resolution.
- CD47 blockade enhances MDM phagocytic capacity, presenting a potential therapeutic strategy.
- Targeting MDM function offers a promising avenue for future ICH treatments.
