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Updated: Jul 29, 2025
Investigation of Macrophage Polarization Using Bone Marrow Derived Macrophages
Published on: June 23, 2013
Mechanism of M2 macrophages modulating astrocyte polarization through the TGF-β/PI3K/Akt pathway
Qi-Ming Pang1, Qian Zhang2, Xiang-Chong Wu3
1Key Laboratory of Cell Engineering of Guizhou Province, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China; Department of Orthopaedic Surgery, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China; Department of Orthopedics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Abstract:
Recent studies have revealed that activated astrocytes (AS) are divided into two distinct types, termed A1 and A2. A2 astrocytes are neuroprotective and promote tissue repair and regeneration following spinal cord injury. Whereas, the specific mechanism for the formation of the A2 phenotype remains unclear. This study focused on the PI3K/Akt pathway and examined whether TGF-β secreted by M2 macrophages could mediate A2 polarization by activating this pathway. In this study, we revealed that both M2 macrophages and their conditioned medium (M2-CM) could facilitate the secretion of IL-10, IL-13 and TGF-β from AS, and this effect was significantly reversed after the administration of SB431542 (a TGF-β receptor inhibitor) or LY294002 (a PI3K inhibitor). Moreover, immunofluorescence results demonstrated that TGF-β secreted by M2 macrophages could facilitate the expression of A2 biomarker S100A10 in AS; combined with the results of western blot, it was found that this effect was closely related to the activation of PI3K/Akt pathway in AS. In conclusion, TGF-β secreted by M2 macrophages may induce the conversion of AS to the A2 phenotype through the activation of the PI3K/Akt pathway.
Insights
Transforming astrocytes (AS) into a neuroprotective A2 phenotype is crucial for spinal cord injury repair. This study reveals that TGF-β from M2 macrophages activates the PI3K/Akt pathway, driving A2 astrocyte polarization.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Activated astrocytes (AS) differentiate into A1 and A2 phenotypes.
- A2 astrocytes are vital for neuroprotection and tissue repair after spinal cord injury.
- The precise mechanisms governing A2 astrocyte polarization are not fully understood.
Purpose of the Study:
- To investigate if TGF-β secreted by M2 macrophages can induce A2 astrocyte polarization.
- To determine the role of the PI3K/Akt pathway in M2 macrophage-mediated A2 astrocyte polarization.
Main Methods:
- Co-culture of M2 macrophages and astrocytes.
- Treatment with M2 macrophage-conditioned medium (M2-CM).
- Inhibition of TGF-β receptor (SB431542) and PI3K (LY294002).
- Immunofluorescence staining for A2 biomarker S100A10.
- Western blot analysis for PI3K/Akt pathway activation.
Main Results:
- M2 macrophages and M2-CM promoted IL-10, IL-13, and TGF-β secretion from AS.
- Inhibition of TGF-β or PI3K reversed these effects.
- TGF-β from M2 macrophages increased S100A10 expression in AS.
- This process involved the activation of the PI3K/Akt pathway in AS.
Conclusions:
- TGF-β secreted by M2 macrophages induces A2 astrocyte polarization.
- The PI3K/Akt pathway is a key mediator in this M2 macrophage-driven astrocyte reprogramming.
- This finding offers potential therapeutic targets for spinal cord injury.
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