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Updated: Feb 24, 2026
Isolation and Flow Cytometric Assessment of Neuroimmune Interactions in a Mini-Stroke Murine Model
Published on: June 20, 2025
Impaired microglia process dynamics post-stroke are specific to sites of secondary neurodegeneration
Murielle G Kluge1,2, Laura Kracht3, Mahmoud Abdolhoseini4
1School of Biomedical Sciences and Pharmacy and the Priority Research Centre for Stroke and Brain Injury, University of Newcastle, Callaghan, New South Wales, Australia.
Abstract:
Stroke induces tissue death both at the site of infarction and at secondary sites connected to the primary infarction. This latter process has been referred to as secondary neurodegeneration (SND). Using predominantly fixed tissue analyses, microglia have been implicated in regulating the initial response at both damage sites post-stroke. In this study, we used acute slice based multiphoton imaging, to investigate microglia dynamic process movement in mice 14 days after a photothrombotic stroke. We evaluated the baseline motility and process responses to locally induced laser damage in both the peri-infarct (PI) territory and the ipsilateral thalamus, a major site of post-stroke SND. Our findings show that microglia process extension toward laser damage within the thalamus is lost, yet remains robustly intact within the PI territory. However, microglia at both sites displayed an activated morphology and elevated levels of commonly used activation markers (CD68, CD11b), indicating that the standardly used fixed tissue metrics of microglial "activity" are not necessarily predictive of microglia function. Analysis of the purinergic P2 Y12 receptor, a key regulator of microglia process extension, revealed an increased somal localization on nonresponsive microglia in the thalamus. To our knowledge, this is the first study to identify a non-responsive microglia phenotype specific to areas of SND post-stroke, which cannot be identified by the classical assessment of microglia activation but rather the localization of P2 Y12 to the soma.
Insights
Microglia in secondary neurodegeneration (SND) areas after stroke lose their ability to respond to damage, unlike those near the stroke core. This functional loss is linked to P2Y12 receptor changes, not just standard activation markers.
Area of Science:
- Neuroscience
- Immunology
- Pathology
Background:
- Stroke causes tissue death at the infarction site and secondary neurodegeneration (SND) in connected areas.
- Microglia, immune cells in the brain, are traditionally thought to regulate responses at both damage sites post-stroke.
- Fixed tissue analyses often assess microglial activation markers to infer function.
Purpose of the Study:
- To investigate dynamic microglia process movement and function in response to local damage in mice 14 days after photothrombotic stroke.
- To compare microglia behavior in the peri-infarct (PI) territory versus the ipsilateral thalamus, a key site of post-stroke SND.
- To determine if standard markers of microglial activation accurately reflect functional responses in different stroke-affected brain regions.
Main Methods:
- Acute slice based multiphoton imaging was used to observe microglia dynamics in live brain slices.
- Local laser damage was induced to assess microglia process extension and responsiveness.
- Microglia morphology, activation markers (CD68, CD11b), and P2Y12 receptor localization were analyzed.
Main Results:
- Microglia in the thalamus (SND area) showed lost process extension towards laser damage, while those in the PI territory retained this function.
- Despite functional differences, microglia in both regions displayed activated morphology and elevated CD68/CD11b levels.
- Non-responsive microglia in the thalamus exhibited P2Y12 receptor localization to the cell body (soma), unlike responsive microglia.
Conclusions:
- A distinct, non-responsive microglia phenotype exists in post-stroke SND areas (thalamus) that is not detectable by standard activation markers.
- P2Y12 receptor localization to the soma is a potential indicator of this functional impairment in microglia within SND regions.
- Dynamic imaging reveals functional deficits in microglia in SND areas that are masked by traditional fixed-tissue activation assessments.
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