Abstract
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%, p<0.05) and d28 (76±7% vs. 102±3%, p<0.01). T1-values increased in the early phase after AKI in both mouse strains. T1-increase was more severe after prolonged ischemia times of 45 min compared to 35 min in both mouse strains, measured in the renal cortex and outer stripe of outer medulla. Kidney volume loss (compared to the contralateral kidney) occurred already after 7 days but proceeded markedly towards 4 weeks in severe AKI. Early renal perfusion impairment was predictive for later kidney volume loss. The progression to chronic kidney disease (CKD) in the severe AKI model was similar in both mouse strains as revealed by histology.ConclusionQuantification 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.
Highlights
Inbred mouse strains are commonly used in experimental studies, as they are known to serve as robust models to mimic human disease
After moderate acute kidney injury (AKI) relative perfusion impairment was significantly higher in B6- than in Svmice at d7 (55±7% vs. 82±8%, p
Renal perfusion impairment was stronger in B6- compared to Sv-animals following moderate AKI
Summary
Inbred mouse strains are commonly used in experimental studies, as they are known to serve as robust models to mimic human disease. Different outcomes among mouse strains have been discovered in animal models of renal injury, hypertension, ischemia reperfusion injury (IRI) of the brain and the kidney and in many more disease models [1,2,3,4,5,6,7]. Renal IRI contributes to acute kidney injury (AKI) in many clinical settings [8,9]. It often occurs after major surgery (e.g. cardiothoracic or trauma) or in patients with hemodynamic instability [10,11]. Decreased renal perfusion and inflammation with tissue edema after IRI leads to AKI and to progressive renal fibrosis as a long-term consequence [13,14,15]
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