Background
Renal biopsy plays a crucial role in diagnosing and assessing the severity of immunoglobulin A nephropathy (IgAN), despite being an invasive procedure with potential risk of failure. Our study focused on evaluating the capability of [18F]AlF-NOTA-FAPI-04 PET/CT in identifying the extent of pathological alterations in IgAN.
Conclusion
[18F]AlF-NOTA-FAPI-04 PET/CT imaging offers IgAN patients a non-invasive and reproducible auxiliary modality to monitor disease progression.
Methods
Twenty patients (13 males and 7 females; mean age, 44 ± 16 years) with newly diagnosed primary IgAN and 10 patients (7 males and 3 females; mean age, 51 ± 4 years) without known renal disease underwent [18F]AlF-NOTA-FAPI-04 PET/CT imaging. Kidney tissues from biopsies were stained with various techniques and examined using immunofluorescence. The Oxford classification was used to evaluate pathological indicators. Immunohistochemical staining was conducted to assess α-smooth muscle actin (αSMA) and fibroblast activation protein (FAP) expression. Renal FAPI uptake measured by positron emission tomography/computed tomography (PET/CT) (maximum and mean standardized uptake value, SUVmax and SUVmean) was correlated with histological findings.
Results
The renal parenchymal FAPI uptake was significantly higher in IgAN patients compared with control patients (SUVmax = 3.9 ± 1.3 vs 1.9 ± 0.4, SUVmean = 3.6 ± 1.2 vs 1.5 ± 0.4; all P < .001). We identified a significant difference in renal parenchymal FAPI uptake among the various categories of the Oxford classification. Correlation analysis revealed a positive association between SUVmax and interstitial fibrosis and tubular atrophy, as well as tubulointerstitial inflammation scores in scarred cortex and non-scarred cortex (r = 0.637, 0.593 and 0.491, all P < .05), Similar associations were observed between SUVmean and these scores (r = 0.641, 0.592 and 0.479, all P < .05). Furthermore, significant positive correlations were observed between SUVmax or SUVmean and the staining scores for glomerular αSMA and FAP, as well as for tubulointerstitial αSMA and FAP (all P < .01).