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Updated: Jul 5, 2025
Unilateral Ureteral Obstruction Model for Investigating Kidney Interstitial Fibrosis
Published on: April 25, 2025
Amide Proton Transfer-Weighted Magnetic Resonance Imaging for Application in Renal Fibrosis: A
Dan Zhao1, Wei Wang2, Yang-Yang Niu3
1Department of Nephrology, Shanghai Tongji Hospital, Tongji University School of Medicine, Shanghai, China, 13072118165@163.com.
Introduction:
Renal fibrosis (RF), being the most important pathological change in the progression of CKD, is currently assessed by the evaluation of a biopsy. This present study aimed to apply a novel functional MRI (fMRI) protocol named amide proton transfer (APT) weighting to evaluate RF noninvasively.
Methods:
Male Sprague-Dawley (SD) rats were initially subjected to bilateral kidney ischemia/reperfusion injury (IRI), unilateral ureteral obstruction, and sham operation, respectively. All rats underwent APT mapping on the 7th and 14th days after operation. Besides, 26 patients underwent renal biopsy at the Nephrology Department of Shanghai Tongji Hospital between July 2022 and May 2023. Patients underwent APT and apparent diffusion coefficient (ADC) mappings within 1 week before biopsy. MRI results of both patients and rats were calculated by comparing with gold standard histology for fibrosis assessment.
Results:
In animal models, the cortical APT (cAPT) and medullary APT (mAPT) values were positively correlated with the degree of RF. Compared to the sham group, IRI group showed significantly increased cAPT and mAPT values on the 7th and 14th days after surgery, but no group differences were found in ADC values. Similar results were found in human patients. Cortical/medullary APT values were significantly increased in patients with moderate-to-severe fibrosis than in patients with mild fibrosis. ROC curve analysis indicated that APT value displayed a better diagnostic value for RF. Furthermore, combination of cADC and cAPT improved fibrosis detection by imaging variables alone (p < 0.1).
Conclusion:
APT values had better diagnostic capability at early stage of RF compared to ADC values, and the addition of APT imaging to conventional ADC will significantly improve the diagnostic performance for predicting kidney fibrosis.
Insights
Amide proton transfer (APT) MRI shows promise for noninvasively assessing renal fibrosis (RF) in early-stage chronic kidney disease (CKD). APT values correlate with fibrosis severity in both animal models and human patients, outperforming ADC values.
Area of Science:
- Biomedical Imaging
- Radiology
- Nephrology
Background:
- Renal fibrosis (RF) is a key indicator of chronic kidney disease (CKD) progression.
- Current RF assessment relies on invasive kidney biopsies.
- Novel noninvasive imaging techniques are needed for early RF detection.
Purpose of the Study:
- To evaluate the efficacy of amide proton transfer (APT) weighting, a functional MRI (fMRI) technique, for noninvasive assessment of renal fibrosis.
- To compare the diagnostic performance of APT imaging with apparent diffusion coefficient (ADC) mapping for RF detection.
Main Methods:
- Animal models (rats) underwent induced kidney injury (ischemia/reperfusion, ureteral obstruction) and sham operations, followed by APT mapping.
- Human patients (n=26) with varying fibrosis severity underwent APT and ADC mapping prior to renal biopsy.
- Histopathology served as the gold standard for correlating MRI findings with fibrosis assessment.
Main Results:
- In both animal models and human patients, elevated cortical and medullary APT values showed a positive correlation with the degree of renal fibrosis.
- APT values were significantly higher in rats and patients with moderate-to-severe fibrosis compared to controls or mild fibrosis groups.
- APT imaging demonstrated superior diagnostic capability for RF compared to ADC values, with combined cADC and cAPT improving detection.
Conclusions:
- Amide proton transfer (APT) MRI offers a valuable noninvasive method for assessing renal fibrosis, particularly in the early stages of CKD.
- APT imaging exhibits better diagnostic performance for renal fibrosis than conventional ADC mapping.
- Integrating APT imaging with ADC mapping can significantly enhance the prediction of kidney fibrosis.
