Quantitation of Urine Sediment Podocalyxin (PCX) Reflects the Estimated Urinary Podocyte Number (eUPN) - Abstract
Introduction: Podocytes are key cells in renal physiology that become injured in many glomerular diseases. Although assessing podocyturia has proven useful in various settings,
the urine podocyte number detected by immunostaining is too small compared to the expected cell loss. This study aimed to estimate the original urinary podocyte number by
measuring the levels of the protein podocalyxin (PCX).
Methods: PCX quantitation by ELISA was performed in patients with glomerular diseases and normal controls. We calculated the quantity of PCX in a single podocyte (136.1
pg) based on previous research data. Subsequently, the estimated urinary podocyte number (eUPN) was calculated by dividing the sediment PCX level by the single podocyte PCX
level. eUPNs were compared between patients and normal controls using the Mann-Whitney U test.
Results: The eUPN was significantly elevated in patients with glomerular diseases than in healthy individuals (mean value, 20.6 cells/mg creatinine vs. 12.9; p<0.05). This
difference was more pronounced in individuals with diseases, such as lupus nephritis, membranous nephropathy, and diabetic kidney disease, involving podocyte injury. A low eUPN
was detected in normal controls. In patients with glomerular diseases, a positive correlation was found between eUPN and proteinuria, albuminuria, urinary alpha-1-microglobulin,
urinary beta-2-microglobulin, and urinary n-acetyl-beta-d-glucosaminidase.
Conclusion: The eUPN might be a sensitive and reliable indicator of urinary podocyte loss.