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Updated: May 11, 2026
Isolation of Cortical Microglia with Preserved Immunophenotype and Functionality From Murine Neonates
Published on: January 30, 2014
808 nm wavelength light induces a dose-dependent alteration in microglial polarization and resultant microglial
Ramona E von Leden1, Sean J Cooney, Teresa M Ferrara
1Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, Jones Bridge Road, Bethesda, Maryland 20814, USA.
Background And Objective:
Despite the success of using photobiomodulation (PBM), also known as low level light therapy, in promoting recovery after central nervous system (CNS) injury, the effect of PBM on microglia, the primary mediators of immune and inflammatory response in the CNS, remains unclear. Microglia exhibit a spectrum of responses to injury, with partial or full polarization into pro- and anti-inflammatory phenotypes. Pro-inflammatory (M1 or classically activated) microglia contribute to chronic inflammation and neuronal toxicity, while anti-inflammatory (M2 or alternatively activated) microglia play a role in wound healing and tissue repair; microglia can fall anywhere along this spectrum in response to stimulation.
Materials And Methods:
The effect of PBM on microglial polarization therefore was investigated using colorimetric assays, immunocytochemistry, proteomic profiling and RT-PCR in vitro after exposure of primary microglia or BV2 microglial cell line to PBM of differing energy densities (0.2, 4, 10, and 30 J/cm(2) , 808 nm wavelength, 50 mW output power).
Results:
PBM has a dose-dependent effect on the spectrum of microglial M1 and M2 polarization. Specifically, PBM with energy densities between 4 and 30 J/cm(2) induced expression of M1 markers in microglia. Markers of the M2 phenotype, including CD206 and TIMP1, were observed at lower energy densities of 0.2-10 J/cm(2) . In addition, co-culture of PBM or control-treated microglia with primary neuronal cultures demonstrated a dose-dependent effect of PBM on microglial-induced neuronal growth and neurite extension.
Conclusion:
These data suggest that the Arndt-Schulz law as applied to PBM for a specific bioassay does not hold true in cells with a spectrum of responses, and that PBM can alter microglial phenotype across this spectrum in a dose-dependent manner. These data are therefore of important relevance to not only therapies in the CNS but also to understanding of PBM effects and mechanisms.
Insights
Photobiomodulation (PBM) alters microglial polarization in a dose-dependent manner, influencing immune responses in the central nervous system (CNS). This research is key for understanding PBM
Area of Science:
- Neuroscience
- Immunology
- Biomedical Engineering
Background:
- Microglia are key immune cells in the central nervous system (CNS), mediating inflammatory responses after injury.
- Microglial polarization exists on a spectrum from pro-inflammatory (M1) to anti-inflammatory (M2) phenotypes.
- The impact of photobiomodulation (PBM) on microglial polarization remains unclear.
Purpose of the Study:
- To investigate the effect of PBM on microglial polarization.
- To determine the dose-dependent effects of PBM on M1 and M2 microglial phenotypes.
- To assess PBM's influence on microglial-mediated neuronal growth.
Main Methods:
- Primary microglia and BV2 cell lines were exposed to PBM at varying energy densities (0.2–30 J/cm²).
- Colorimetric assays, immunocytochemistry, proteomic profiling, and RT-PCR were employed.
- Co-culture experiments with primary neurons assessed PBM-induced effects on neuronal growth.
Main Results:
- PBM demonstrated a dose-dependent effect on microglial polarization.
- Higher PBM energy densities (4–30 J/cm²) induced M1 marker expression.
- Lower PBM energy densities (0.2–10 J/cm²) promoted M2 marker expression (e.g., CD206, TIMP1).
- PBM influenced microglial-induced neuronal growth and neurite extension in a dose-dependent manner.
Conclusions:
- PBM can modulate microglial phenotype across the M1/M2 spectrum in a dose-dependent way.
- The findings challenge the universal applicability of the Arndt-Schulz law in PBM bioassays involving cells with diverse responses.
- These results have significant implications for CNS therapies and understanding PBM mechanisms.
