Urinary TNFR2 and Association with Kidney Injury in Patients with Nephrotic Syndrome

Background: Tumor necrosis factor receptor 2 (TNFR2) in plasma (pTNFR2) has been identified as a prognostic biomarker strongly associated with DKD progression. The association of urinary TNFR2 (uTNFR2) levels with kidney injury, clinical outcome, and intra-kidney TNFR2 expression remains poorly understood. Methods: uTNFR2 (normalized by urine creatinine) and pTNFR2 levels were obtained using SOMAscan proteomics analysis for a subgroup of patients with nephrotic syndrome (NS) with matching urine, plasma, and kidney biopsy transcriptomic data (n=96) in the NEPTUNE cohort. uTNFR2 level was validated using ELISA. Glomeruli (glom) and tubulointerstitium (TI) expression values for TNFRSF1B, the gene encoding TNFR2, and the TNF pathway score (TNFPAS) were extracted from published RNA-seq profiles. Mono-nuclear white blood cells (MWBCs) were used to evaluate tubulointerstitial inflammation. Correlations were performed using Pearson’s correlation. Single cell RNA-seq was used to determine the expression in kidney cells. Cox regression model was used to evaluate the association with outcome. Results: SOMAscan uTNFR2 is tightly correlated with ELISA results (r=0.95, p=1e-043). uTNFR2 was higher in patients than healthy controls (p<0.0001). Higher uTNFR2 is correlated with lower GFR, higher proteinuria, inflammation by MWBCs, and TNFPAS. uTNFR2 is significantly correlated with TI but not glom TNFRSF1B mRNA. uTNFR2 was correlated with pTNFR2. Notably, pTNFR2 showed weaker correlation with above parameters than uTNFR2. Enriched expression of TNFRSF1B is observed in kidney endothelial and immune cells. Furthermore, uTNFR2 showed significant association with progression to composite endpoint of kidney failure or 40% reduction of baseline GFR after adjusting for age, sex, race, GFR, and UPCR (HR 2.11, 95% CI (1.03,4.31), p = 0.04). Conclusion: uTNFR2 is significantly associated with cross- sectional and longitudinal outcome in patients with NS. The enriched expression of TNFRSF1B mRNA in kidney cells, and the stronger correlation of uTNFR2 over pTNFR2 with TI TNFRSF1B and MWBCs suggest that kidney cells could contribute to uTNFR2 level. The significant correlation of uTNFR2 with TNFPAS suggests that uTNFR2 may serve as a non-invasive biomarker for kidney TNF pathway activation. Funding: NIDDK Support