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Journal Article Epublish 21 citations

PubMed: 35705953 DOI: 10.1186/s12974-022-02487-x

Reduced microglia activation following metformin administration or microglia ablation is sufficient to prevent functional deficits in a mouse model of neonatal stroke.

J Neuroinflammation 19(1):146

Authors: Clara Bourget, Kelsey V Adams, Cindi M Morshead

Affiliations

  • Institute of Medical Sciences, University of Toronto, Toronto, M5S1A8, Canada.
  • Institute of Medical Sciences, University of Toronto, Toronto, M5S1A8, Canada.
  • Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Room 1006, Toronto, ON, M5S3E1, Canada.
  • Division of Anatomy, Department of Surgery, University of Toronto, Toronto, M5S1A8, Canada.
  • Institute of Biomedical Engineering, University of Toronto, Toronto, M5S3E1, Canada.

Abstract

BACKGROUND

Neonatal stroke is a devastating insult that can lead to life-long impairments. In response to hypoxic-ischaemic injury, there is loss of neurons and glia as well as a neuroinflammatory response mediated by resident immune cells, including microglia and astrocytes, which can exacerbate damage. Administration of the antidiabetic drug metformin has been shown to improve functional outcomes in preclinical models of brain injury and the cellular basis for metformin-mediated recovery is unknown. Given metformin's demonstrated anti-inflammatory properties, we investigated its role in regulating the microglia activation and used a microglia ablation strategy to investigate the microglia-mediated outcomes in a mouse model of neonatal stroke.

METHODS

Hypoxia-ischaemia (H-I) was performed on post-natal day 8. Metformin was administered for one week, starting one day after injury. Immunohistochemistry was used to examine the spatiotemporal response of microglia and astrocytes after hypoxia-ischaemia, with or without metformin treatment. To evaluate the effects of microglia depletion after hypoxia-ischaemia, we delivered Plexxikon 5622 for 1 or 2 weeks post-injury. The regional pattern of microglia and astrocyte depletion was assessed through immunohistochemistry. Motor behaviour was assessed with the righting reflex, hindlimb suspension, grip strength and cylinder tests.

RESULTS

Herein, we revealed a spatiotemporally regulated response of microglia and astrocytes after hypoxia-ischaemia. Metformin treatment after hypoxia-ischaemia had no effect on microglia number and proliferation, but significantly reduced microglia activation in all regions examined, concomitant with improved behavioural outcomes in injured mice. Plexxikon 5622 treatment successfully ablated microglia, resulting in a > 90% depletion in microglia in the neonatal brain. Microglia rapidly repopulated upon treatment cessation of Plexxikon. Most interesting, microglia ablation was sufficient to reduce functional deficits after hypoxia-ischaemia, mimicking the effects of 1 week of metformin treatment post-injury.

CONCLUSION

These results highlight the importance of regulating the neuroinflammatory response after neonatal stroke to promote recovery.

MeSH

Stroke, Brain, Neuroglia, Astrocytes, Metformin, Microglia

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