Abstract Body: Introduction: Astrocytes are non-neuronal cells in the CNS that play crucial roles in synaptic formation, maturation, and maintenance through the synthesis and secretion of various proteins. We identified Chordin-like 1 (Chrdl1) as an astrocyte-secreted protein that limits synaptic plasticity by stabilizing GluA2-containing AMPA receptors (GluA2-AMPARs) at synaptic sites in the cortex. In a mouse model of ischemic stroke, we found that Chrdl1 is excessively upregulated in astrocytes in the peri-infarct area during the post-stroke plasticity window (2–30 days post-stroke in the mouse). We found that Chrdl1 KO mice displayed enhanced synaptic plasticity, and in response to stroke, deficits such as dendritic spine degeneration, impaired GluA2-AMPAR distribution, and motor dysfunction were significantly alleviated. Seeking a pharmacological approach to mitigate stroke-induced Chrdl1 upregulation, we explored the use of sub-anesthetic ketamine, known to enhance plasticity and alter astrocytic function, potentially affecting protein secretion. However, its impact on post-stroke astrocyte-regulated plasticity and recovery has not yet been explored.
We hypothesize that sub-anesthetic ketamine may restrict the upregulation of astrocytic Chrdl1 during the post-stroke plasticity window and reduce stroke-induced deficits.
Methods: To generate ischemia in vivo, we used photothrombosis to induce distal middle cerebral artery occlusion (PT-dMCAO). Male and female adult mice (2 months old) received a daily dose of sub-anesthetic ketamine (10mg/kg) via intranasal injection for one week. We used single molecule fluorescence in situ hybridization (smFISH) and immunohistochemistry to assess Chrdl1 mRNA and protein levels in peri-infarct astrocytes, synaptic staining and high-resolution confocal microscopy to analyze GluA2-AMPARs distribution, Golgi stainings to study dendritic branching and spine density, and several behavioral tests to assess motor performance, sensorimotor function, and learning and memory.
Results: We found that sub-anesthetic ketamine treatment reverts stroke-induced Chrdl1 upregulation in peri-infarct astrocytes and mitigates molecular, structural and behavioral deficits.
Conclusions: Our study suggests that sub-anesthetic ketamine treatment is a promising approach to limit astrocyte-driven molecular deficits during the critical post-stroke plasticity window, which may otherwise hinder recovery, and holds great promise for clinical translation.