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Updated: May 2, 2026
Isolation of Cortical Microglia with Preserved Immunophenotype and Functionality From Murine Neonates
Published on: January 30, 2014
Distinct reduction in relative microglial glucose uptake compared to astrocytes and neurons upon isolation from the
Sebastian T Kunte1,2, Johannes Gnörich1,3, Philipp Beumers1
1Department of Nuclear Medicine, LMU University Hospital, Munich, Germany.
Introduction:
Microglial energy metabolism has gained attention for the treatment of neurodegenerative diseases. In vitro methods provide important insights; however, it remains unclear whether the metabolism of highly motile microglia is preserved outside their regular environment. Therefore, we directly compared the microglial glucose uptake in vivo and in vitro in mice.
Methods:
Microglia and astrocytes were isolated from the brain using immunomagnetic cell sorting following [18F]FDG injection in living mice, followed by gamma and single-cell radiotracing (scRadiotracing). Enriched cell fractions were incubated with excess [18F]FDG (50,000-fold) in vivo, washed, and measured equivalently. For all fractions, radioactivity per cell was normalized to the injected or incubated radioactivity, and ratios of microglialuptake were calculated relative to astrocytes and the microglia/astrocyte-negative fraction. The experiment was repeated using a glucose-free buffer and validated by in vitro incubation without prior in vivo [18F]FDG injection to exclude the influence of fasting and glucose injection.
Results:
scRadiotracing results were compared against cell culture [18F]-FDG incubation. The in vivo glucose uptake of microglia was higher when compared to astrocytes (50.4-fold, p < 0.0001) and non-microglia/ non-astrocyte cells (10.6-fold, p < 0.0001). Microglia still exhibited the highest glucose uptake in vitro, but with a distinct reduction in microglia-to-astrocyte (5.7-fold, p < 0.0015) and microglia-to-microglia/astrocyte-negative ratios (1.7 fold, p < 0.0001). Fasting and in vitro incubation were used to validate the results. Cell culture indicated low microglial uptake compared to that in neurons (1:100) or astrocytes (1:10).
Discussion:
Compared to astrocytes and other cells, microglia show a distinct reduction in uptake in vitro compared to in vivo uptake. Our results emphasize that in vitro experiments should be interpreted with caution when studying microglial energy metabolism.
Insights
Microglial glucose uptake is significantly higher in vivo than in vitro. These findings suggest caution when interpreting in vitro studies of microglial energy metabolism in neurodegenerative disease research.
Area of Science:
- Neuroscience
- Cell Biology
- Metabolism Research
Background:
- Microglial energy metabolism is crucial for neurodegenerative disease treatment.
- In vitro studies offer insights but may not reflect the in vivo environment of highly motile microglia.
Purpose of the Study:
- To directly compare microglial glucose uptake in vivo and in vitro in mice.
- To assess the preservation of microglial metabolism outside their natural environment.
Main Methods:
- Isolated microglia and astrocytes from mouse brains using immunomagnetic cell sorting after [18F]FDG injection.
- Utilized single-cell radiotracing (scRadiotracing) for in vivo and in vitro measurements.
- Normalized radioactivity per cell and calculated uptake ratios relative to other cell types.
Main Results:
- In vivo, microglia exhibited significantly higher glucose uptake than astrocytes (50.4-fold) and other cells (10.6-fold).
- In vitro, microglia retained the highest glucose uptake but showed reduced ratios compared to in vivo levels.
- Cell culture revealed low microglial uptake relative to neurons (1:100) and astrocytes (1:10).
Conclusions:
- Microglial glucose uptake is markedly reduced in vitro compared to in vivo.
- In vitro experimental conditions alter microglial energy metabolism.
- Results highlight the need for caution when interpreting in vitro findings for microglial metabolism in neurodegenerative diseases.
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