Functional MRI for characterization of renal perfusion impairment and edema formation due to acute kidney injury in different mouse strains

PurposeThe purpose was to characterize acute kidney injury (AKI) in C57BL/6 (B6)- and 129/Sv (Sv)-mice by noninvasive measurement of renal perfusion and tissue edema using functional MRI.MethodsDifferent severities of AKI were induced in B6- and Sv-mice by renal ischemia reperfusion injury (IRI). Unilateral clamping of the renal pedicle for 35 min (moderate AKI) or 45 min (severe AKI) was done. MRI (7-Tesla) was performed 1, 7 and 28 days after surgery using a flow alternating inversion recovery (FAIR) arterial spin labeling (ASL) sequence. Maps of perfusion and T1-relaxation time were calculated. Relative MRI-parameters of the IRI kidney compared to the contralateral not-clipped kidney were compared between AKI severities and between mouse strains using unpaired t-tests. In addition, fibrosis was assessed by Masson Trichrome and collagen IV staining.ResultsAfter moderate AKI relative perfusion impairment was significantly higher in B6- than in Sv-mice at d7 (55±7% vs. 82±8%, pConclusionQuantification of renal perfusion and tissue edema by functional MRI allows characterization of strain differences upon AKI. Renal perfusion impairment was stronger in B6- compared to Sv-animals following moderate AKI. Prolonged ischemia times were associated with more severe perfusion impairment and edema formation in the early phase and progression to CKD within 4 weeks of observation.