Huishu Hou,1 M. Jake Pushie,1 Nicole J. Sylvain,1 Sharleen Weese Maley1, Mark J. Hackett,2 and Michael E. Kelly1

1 Department of Surgery, College of Medicine, University of Saskatchewan.

2Nanochemistry Research Institute, Department of Chemistry, Curtin University, Perth, Australia. ​


The changes in elemental distributions (Ca, K, Zn, etc.) during the progression from the acute to chronic phase following ischemic stroke are poorly understood due to the limitations of conventional imaging and biochemical detection techniques. Synchrotron-based X-ray fluorescence imaging (XFI) is a non-destructive technique providing visualization and quantification of microscopic distributions of elements without pre-treatment or staining. We employ a mouse model of focal ischemia to induce a thrombus in the motor cortex. At pre-defined post-stroke intervals (1h, 24h, 48h, 72h, and 7, 14, 21 and 28 days), brains are collected and frozen for cryo-sectioning. 30-micron thick sections are collected and mapped using XFI for Cl, Ca, Mn, K, and Zn. The XFI results show significant accumulation of Cl and Ca within the stroke lesion, and reduction in P, S, and Zn as early as 1h post-stroke. These trends continue until 72h post-stroke. Unaffected areas of brain show no significant changes compared to shams throughout the time course. Many elements return to normal levels in the penumbra after 1 week. We hypothesize that these changes in elemental levels are due to redistribution between the infarct, extracellular environment, and blood, due to disruption of the blood-brain-barrrier. Mn started accumulate after 3d post-stroke. Transmission electron microscope (TEM) result shows mitochondria die acutely in ischemic tissues and re-appear at later time points. Mitochondria are rich in Mn, and Mnis incorporated into enzymes as Mn-superoxide dismutase (SOD2) which protects cells from oxidative.​

X-ray fluorescence imaging reveals the dynamic time course of elemental changes in an ischemic stroke model