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


METHODS
Different 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.


RESULTS
After 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.


CONCLUSIONS
Quantification 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.
Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.
Susanne
S
Tewes
Nephrology, Hannover Medical School, Hannover, Germany.
Faikah
F
Gueler
Nephrology, Hannover Medical School, Hannover, Germany.
Rongjun
R
Chen
Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.
Marcel
M
Gutberlet
Nephrology, Hannover Medical School, Hannover, Germany.
Mi-Sun
MS
Jang
Laboratory Animal Science, Hannover Medical School, Hannover, Germany.
Martin
M
Meier
Department of Laboratory Medicine & Pathology, University of Alberta, Edmonton, Canada.
Michael
M
Mengel
Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.
Dagmar
D
Hartung
Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.
Frank
F
Wacker
Nephrology, Hannover Medical School, Hannover, Germany.|The Transplantation Center of the affiliated hospital, Zunyi Medical College, Zunyi, China.
Song
S
Rong
Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.
Katja
K
Hueper
D058186:Acute Kidney Injury / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D004195:Disease Models, Animal; D018450:Disease Progression; D004487:Edema / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D005355:Fibrosis / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D007150:Immunohistochemistry; D007668:Kidney / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D008264:Macrophages / Q000473:pathology / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D009929:Organ Size; D015427:Reperfusion Injury; D012720:Severity of Illness Index; D013045:Species Specificity; D013997:Time Factors