Refining the Composition and Significance of Human Renal Intratubular Casts Using Spatial Protein Imaging
Year: 2025
Type: preprint
Study design: Observational Study
Abstract: Background: Renal intratubular casts are frequently observed in the distal nephron segments of the kidney and have long been regarded as a sign of renal disease. However, the composition and pathological significance of intratubular casts have remained understudied. Methods: We leveraged Hematoxylin and Eosin (H&E) staining to identify intratubular casts along with concurrent Co-detection by indexing (CODEX) multiplexed spatial protein imaging on human kidney biopsy sections from the Kidney Precision Medicine Project (KPMP). We also conducted immunoblotting of Prominin-1 (PROM1) in urine and assessed its levels from publicly available urinary proteomics datasets of the KPMP consortium. Results: We analyzed 424 intratubular casts across 33 individuals with kidney disease or healthy controls. We identified PROM1 and IGFBP7 as major constituents of casts (positive staining in 90.1% and 35.6%, respectively). Staining for UMOD, an established cast component, was present in 86.1%. These components exhibited distinct alterations depending on the disease state. Intratubular casts were predominantly detected in the distal nephron segments, and their presence was associated with a marked loss of NCC and AQP2 expression in the cast-containing tubular epithelium, suggesting underlying injury. The loss of these membrane transporters correlated with protein components within casts, and the presence of intra-cast PROM1 showed the strongest association, with an odds ratio of 30.8 (95% confidence interval: 13.4-71.0). Urinary PROM1 secretion was confirmed by immunoblotting and was increased in patients with acute kidney injury (AKI) compared to healthy controls (p = 0.01). Conclusions: We identified PROM1, a dedifferentiation and injury marker expressed in epithelial cells, as a novel major constituent of intratubular casts. Our studies suggest that protein composition signature within casts varies with disease state and is associated with tubular injury in distal nephron segments. Our study also suggests that urinary PROM1 may serve as a biomarker for AKI.
Source: medRxiv
Authors: Azuma Nanamatsu, Angela R. Sabo, Daria Barwinska, William S. Bowen, Jessica Hata, Michael Ferkowicz, Takashi Hato, Michael T. Eadon, Pierre C. Dagher, Avi Z. Rosenberg, Tarek M. El-Achkar, the Kidney Precision Medicine Project
Language: English
Subfield: Nephrology
Field: Medicine
Domain: Health Sciences
Open Access status: green
Awards: G1141648645, G1393389346, G1468227772, G1803346691, G1941961128, G2401209495, G250158837, G3091030854, G3145000573, G3181924590, G3280926939, Understanding the Function of Tamm-Horsfall Protein in Acute kidney Injury., G3643202637, G382880093, G4575112883, G4960608113, Multidimensional cellular interrogation of the kidney in AKI and CKD, G665988906, Minnesota Precision Medicine CKD & Resilient Diabetes Recruiting Site: Engagement, Enrollment & Ethics, University of Illinois at Chicago KPMP CKD Recruitment Site, Boston Chronic Kidney Disease Research Biopsy Center, Spatial Mapping of Proteomic and Transcriptional Signatures in Kidney Disease
OpenAlex ID: W4413480507