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Updated: Aug 27, 2026
A Cell Culture Model for Studying the Role of Neuron-Glia Interactions in Ischemia
Published on: November 14, 2020
Microglial Calcium Waves During the Hyperacute Phase of Ischemic Stroke
Lei Liu1, Kathryn N Kearns1, Ilyas Eli2
1Department of Neurological Surgery (L.L., K.N.K., K.A. Sharifi, S.S., K.W.S., M.Y.S.K., M.P., P.T.), University of Virginia Health System, Charlottesville.
Background And Purpose:
Ischemic injury triggers multiple pathological responses in the brain tissue, including spreading depolarizations across the cerebral cortex (cortical spreading depolarizations [CSD]). Microglia have been recently shown to play a significant role in the propagation of CSD. However, the intracellular responses of myeloid cells during ischemic stroke have not been investigated.
Methods:
We have studied intracellular calcium activity in cortical microglia in the stroke model of the middle cerebral artery occlusion, using the murine Polr2a-based and Cre-dependent GCaMP5 and tdTomato reporter (PC::G5-tdT). High-speed 2-photon microscopy through cranial windows was employed to record signals from genetically encoded indicators of calcium. Inflammatory stimuli and pharmacological inhibition were used to modulate microglial calcium responses in the somatosensory cortex.
Results:
In vivo imaging revealed periodical calcium activity in microglia during the hyperacute phase of ischemic stroke. This activity was more frequent during the first 6 hours after occlusion, but the amplitudes of calcium transients became larger at later time points. Consistent with CSD nature of these events, we reproducibly triggered comparable calcium transients with microinjections of potassium chloride (KCl) into adjacent cortical areas. Furthermore, lipopolysaccharide-induced peripheral inflammation, mimicking sterile inflammation during ischemic stroke, produced significantly greater microglial calcium transients during CSD. Finally, in vivo pharmacological analysis with CRAC (calcium release-activated channel) inhibitor CM-EX-137 demonstrated that CSD-associated microglial calcium transients after KCl microinjections are mediated at least in part by the CRAC mechanism.
Conclusions:
Our findings demonstrate that microglia participate in ischemic brain injury via previously undetected mechanisms, which may provide new avenues for therapeutic interventions.
Insights
Microglia exhibit calcium activity during ischemic stroke, contributing to brain injury. This activity, linked to cortical spreading depolarizations (CSD), is modulated by inflammation and CRAC channels, offering potential therapeutic targets.
Area of Science:
- Neuroscience
- Cellular Biology
- Pathology
Background:
- Ischemic stroke causes brain injury via pathological responses like cortical spreading depolarizations (CSD).
- Microglia are implicated in CSD propagation, but their intracellular responses during stroke remain unclear.
Purpose of the Study:
- Investigate intracellular calcium activity in microglia during ischemic stroke.
- Determine the role of microglial calcium signaling in CSD and potential therapeutic targets.
Main Methods:
- Utilized a murine stroke model (middle cerebral artery occlusion) with a Cre-dependent GCaMP5/tdTomato reporter.
- Employed high-speed 2-photon microscopy in vivo to record microglial calcium activity.
- Applied inflammatory stimuli and pharmacological inhibitors (CM-EX-137) to modulate responses.
Main Results:
- Observed periodical microglial calcium activity during the hyperacute phase of ischemic stroke.
- Calcium transient frequency peaked early, while amplitudes increased later.
- CSD-like calcium transients were triggered by KCl, enhanced by inflammation, and partially mediated by CRAC channels.
Conclusions:
- Microglia engage in previously unrecognized mechanisms during ischemic brain injury.
- Microglial calcium signaling during CSD presents novel therapeutic intervention possibilities.
