RENAL‐CHIP: Rejection Evaluation via Non‐Invasive Analysis of Circulating Podocytes With Herringbone‐Chip Isolation Platform

ABSTRACT Immune rejection limits long‐term renal allograft survival, yet current diagnostics lack non‐invasive, and precise detection. Here, donor‐derived circulating podocytes (CPCs) are identified as a blood‐based surrogate of acute rejection. A magnetically reversible herringbone microfluidic chip equipped with epithelial cell adhesion molecule (EpCAM) antibody‐functionalized magnetic beads efficiently isolates CPCs from 1 mL of peripheral blood (capture efficiency 84.4%, release 95.5%, viability 96.0%). Among 65 participants, only transplant recipients with biopsy‐confirmed rejection exhibited≥35 CPCs mL ^{− 1} (AUC = 1.0). Fluorescence in situ hybridization (FISH) of sex‐mismatched transplants confirmed donor origin. Single‐cell RNA‐seq of 10 isolated CPCs revealed up‐regulation of podocyte‐injury and innate/adaptive immune genes (such as NF‐κB, TNF, NOD‐like receptor pathways) in rejection versus stable samples. CPC enumeration thus provides a minimally invasive, mechanistically informed warning of renal allograft rejection.