To characterize ischemia reperfusion injury (IRI)-induced acute kidney injury (AKI) in C57BL/6 (B6) and CD1-mice by longitudinal functional MRI-measurement of edema formation (T2-mapping) and inflammation (diffusion weighted imaging (DWI)). IRI was induced with unilateral right renal pedicle clamping for 35min. 7T-MRI was performed 1 and 14 days after surgery. DWI (7 b-values) and multiecho TSE sequences (7 TE) were acquired. Parameters were quantified in relation to the contralateral kidney on day 1 (d1). Renal MCP-1 and IL-6-levels were measured by qPCR and serum-CXCL13 by ELISA. Immunohistochemistry for fibronectin and collagen-4 was performed. T2-increase on d1 was higher in the renal cortex (127 ± 5% vs. 94 ± 6%, p < 0.01) and the outer stripe of the outer medulla (141 ± 9% vs. 111 ± 9%, p < 0.05) in CD1, indicating tissue edema. Medullary diffusivity was more restricted in CD1 than B6 (d1: 73 ± 3% vs. 90 ± 2%, p < 0.01 and d14: 77 ± 5% vs. 98 ± 3%, p < 0.01). Renal MCP-1 and IL-6-expression as well as systemic CXCL13-release were pronounced in CD1 on d1 after IRI. Renal fibrosis was detected in CD1 on d14. T2-increase and ADC-reduction on d1 correlated with kidney volume loss on d14 (r = 0.7, p < 0.05; r = 0.6, p < 0.05) and could serve as predictive markers. T2-mapping and DWI evidenced higher susceptibility to ischemic AKI in CD1 compared to B6.
Keywords: T2 mapping; acute kidney injury; diffusion weighted imaging; functional MRI; ischemia reperfusion injury.