Coordinated Hippo, IFN and NF-κB pathway activation in kidney rejection.

OBJECTIVES: Renal allograft rejection diagnosis requires invasive biopsy. We assessed whether peripheral blood mRNA of 14 Hippo, interferon (IFN) and NF-κB pathway genes and 11 serum biomarkers could distinguish acute rejection from stable graft function. METHODS: Three groups: biopsy-confirmed acute rejection (n=20), stable graft (n=25), healthy controls (n=30). PBMC mRNA was quantified by qRT-PCR; serum biomarkers by ELISA and spectrophotometry. Statistical analyses used Mann-Whitney U with Benjamini-Hochberg correction; ROC analyses used bootstrap 95 % CIs and 5-fold cross-validation. GEO datasets GSE51675 and GSE145408 provided directional cross-validation. RESULTS: Thirteen of 14 genes were upregulated in rejection vs. controls (pFDR<0.01); TEAD1 (log2FC=+2.44) and TRAF6 (+2.40) led. ISG15 was downregulated in both transplant groups, consistent with calcineurin inhibitor-mediated suppression, while serum free ISG15 protein was unchanged in stable graft but markedly lower in rejection than in both controls and stable graft (pFDR<0.001 and 0.002), discriminating rejection from stable graft in a way the mRNA signal did not. Only TEAD1 (Cohen's d=1.40) and YAP1 (d=1.17) discriminated rejection from stable graft with adequate power. TEAD1 mRNA (AUC=0.849) and serum leptin (AUC=0.922) were the strongest single markers; their combination yielded cross-validated AUC=0.990. CONCLUSIONS: PBMC YAP1/TEAD1 with serum leptin are promising non-invasive biomarkers for acute renal rejection. ISG15 downregulation is more consistent with calcineurin inhibitor-mediated suppression than with generalized immune impairment, although this interpretation requires direct mechanistic confirmation; notably, serum free ISG15 protein discriminated rejection from stable graft even though PBMC ISG15 mRNA did not, suggesting the protein-level measurement warrants further evaluation as a candidate marker. Prospective multicentre validation is required.