Abstract
Background We have previously found that papillary histopathology differs greatly between calcium oxalate and brushite stone formers (SF); the latter have much more papillary mineral deposition, tubular cell injury and tissue fibrosis.
Methods In this study, we applied unbiased orthogonal “omics” approaches on biopsied renal papillae and extracted stones from patients with brushite or calcium oxalate (CaOx) stones. Our goal was to discover stone type-specific molecular signatures to advance our understanding of the underlying pathogenesis.
Results Brushite SF did not differ from CaOx SF with respect to metabolic risk factors for stones, but did exhibit increased tubule plugging in their papillae. Brushite SF had upregulation of inflammatory pathways in papillary tissue, and increased neutrophil markers in stone matrix compared to those with CaOx stones. Large-scale 3D tissue cytometry on renal papillary biopsies showed an increase in the number and density of neutrophils in the papillae of brushite vs. CaOx patients, thereby linking the observed inflammatory signatures to the neutrophils in the tissue. To explain how neutrophil proteins appear in the stone matrix, we measured neutrophil extracellular trap (NET) formation, NETosis, and found it significantly increased in the papillae of brushite compared to CaOx patients.
Conclusions We show that increased neutrophil infiltration and NETosis is an unrecognized factor that differentiates brushite and CaOx SF, and may explain the markedly increased scarring and inflammation seen in the papillae of brushite patients. Given the increasing prevalence of brushite stones, the role of neutrophil activation in brushite stone formation requires further study.
Footnotes
Translational Statement Kidney stone disease is very common and causes significant morbidity. The main goal of this study was to uncover stone-type specific molecular signatures using a precision medicine approach that combines unbiased transcriptomics, proteomics and innovative 3D imaging strategies. We found that increased neutrophil infiltration and NETosis are unrecognized new factors specifically associated with brushite stone formation. These discoveries underscore the unequivocal presence of inflammation in human stone disease, and the divergence of cellular and molecular pathways in distinct forms of nephrolithiasis.