Cerebral Blood Flow Measured by Mri is a Key Translational Hallmark of Brain Injury in Experimental Models of Hypertension-Induced Cognitive Impairment

While several works pointed out the epidemiological associations between hypertension and dementia, the underlying mechanisms are still relatively unknown. In this work we focused on the application of translational tools like MRI to investigate the brain injury induced by hypertension and characterized by cognitive impairment and neuroinflammation. Cerebral hypertension was induced in mice by transverse aortic constriction (TAC) or sham procedure, as previously demonstrated by our group. We characterized cerebral blood flow (CBF) by 7T MRI, measuring the cerebral tissue blood prefusion. Morris Water Maze (MWM) was used to evaluate cognitive function in hypertensive and normotensive mice. Cortical microvasculature was analyzed in histological brain sections. A group of mice was treated with an antibody neutralizing IFNy, a key proinflammatory cytokine induced by hypertension. TAC mice showed a marked cerebral hypoperfusion, with CBF reduction in cortex (Sham: 96.58 vs TAC: 74.25 mL/100g/min p=0.024) and hypothalamus (Sham: 140 vs TAC: 121.4 mL/100g/min p=0.027). Tissue analysis revealed a reduction in capillary density defined as portion of field of view (FOV) occupied by capillaries (Sham: 11.3% vs TAC: 7.7%, p=0.004) and loss of their integrity in the cortex of hypertensive mice, defined as pericyte coverage percentage in the FOV (Sham: 79% vs TAC: 36%, p=0.01). Finally, the impairment in cognitive function measured by the MWM correlated with the CBF measures (r 2 :0.407, p=0.01). In the end, we subjected TAC mice to anti-IFNy treatment and analyzed the effects on brain vasculature assessed in vivo by MRI and ex vivo by histology. We observed that, while leaving unchanged the hemodynamic challenge on the brain, the treatment induced a global rescue in CBF (TAC: 99.85 vs TAC anti-IFNy: 116 mL/100g/min p=0. 008) and a strong correlation between MRI-measured CBF and microvascular density (r 2 :0.471, p=0.002). In conclusion, CBF evaluated by MRI is a key translational hallmark of hypertensive brain injury, and its evaluation in the clinical setting can provide insights on cerebral microvasculature health.