Abstract Body: Introduction: White matter injury (WMI) underlies clinical deficits in stroke patients. Small vessel occlusions and lacunar infarcts are more common than large vessel occlusions. Therefore, understanding the focal WM ischemia progression and the correlated behavioral outcomes in longitudinal studies is essential to identify new treatment options and windows. Utilizing the in vivo selective focal WM injury (sfWMI), we aimed to develop novel MRI modalities to detect WMI and to correlate with behavioral and histological deficits. We previously reported that CX-4945, a selective CK2 inhibitor, promotes post-ischemic axon function recovery, and preserves mitochondria. Because neuronal NADPH oxidase (NOX) causes oxidative stress leading to mitochondria damage, we hypothesized that CK2 mediates WMI by activating NOX leading to mitochondrial dysfunction, and post-ischemic CK2 inhibition confers WM protection following ischemia.
Methods: Using male and female mice, 200nL of L-NIO (130µM) or saline for sham were deposited at earlier identified stereotaxic coordinates. Behavioral deficits were assessed using cylinder test, and pasta-eating test at baseline, and between days 1-28 post-injury. T2-weighted, magnetization transfer contrast (MTC), and diffusion tensor imaging (DTI), axonal tractography were taken between days 2-29 post-injury. CX-4945 (75mg/kg) or PBS was administered for the treatment and control group respectively for 5 days, twice daily. On days 7 and 28 the corpus callosum was isolated and processed for live mitochondrial function assessment using the Seahorse platform, and NOX enzymatic activity.
Results: the sfWMI caused significant long-term WM damage that is quantifiable using T2, MTC, and DTI modalities corresponding with impaired bilateral paw use and dexterity. The deficits are correlated with axon and myelin damage, astrocyte and microglia activation, mitochondrial dysfunction, and upregulation of NOX activity. Application of CX-4945 preserved WM integrity histologically, alleviated behavioral deficits, preserved mitochondrial function, attenuated NOX activity, and improved WM structure in MRI.
Conclusion: We established MRI modalities to longitudinally assess WMI damage which correlates with behavioral deficits and cellular and molecular damage. Additionally, we showed that CX-4945 exerts post-ischemic protection of WM integrity quantified with MRI images, decreased NOX activity, and improved mitochondrial function.