Renal ischemia-reperfusion injury in rabbits evaluated with quantitative susceptibility mapping: an animal study

There were no effective noninvasive methods to diagnose renal ischemia-reperfusion injury (IRI), which is a major clinical problem. The objective of this study was to explore the feasibility of the quantitative susceptibility mapping (QSM) technique in evaluating the dynamic changes in the renal IRI process.

A total of 36 New Zealand rabbits were randomly assigned to the IRI group (n=30) and the sham group (n=6). All rabbits underwent magnetic resonance imaging (MRI) examination, including T2-weighted imaging and QSM before the operation (pre-IRI) and 1, 12, 24, and 48 h after the operation (IRI-1h, IRI-12h, IRI-24h, and IRI-48h, respectively). Regions of interest were manually delineated in the outer medulla. All specimens were stained with hematoxylin and eosin (HE) and glutathione peroxidase 4 (GPX4). The pathological score of renal injury and the average optical density value of GPX4 were calculated. The repeated measurement analysis of variance (ANOVA) and Spearman correlation analysis were used to compare the differences between the susceptibility values and determine the correlation.

In the IRI group, the susceptibility values of the outer medulla at the pre-IRI, IRI-1h, IRI-12h, IRI-24h, and IRI-48h time points were (42.83±7.83)×10^-3, (-5.33±6.28)×10^-3, (6.50±3.94)×10^-3, (12.00±3.74)×10^-3, and (22.00±6.81)×10^-3 ppm, respectively. The susceptibility values significantly differed among the different time points (P<0.001). The susceptibility values had a negative correlation with the scores of cell edema (ρ=-0.61; P=0.002) and the average optical density value of GPX4 (ρ=-0.70; P<0.001). The susceptibility values had a positive correlation with iron content (ρ=0.79; P<0.001), the scores of cell necrosis (ρ=0.71; P<0.001), interstitial inflammation (ρ=0.60; P=0.002), cast (ρ=0.75; P<0.001), and the total pathological score of renal injury (ρ=0.51; P=0.01).

QSM can be used as a noninvasive method to assess the dynamic changes of the outer medulla in the early stage of renal IRI in rabbits.