Introduction:
Tumor necrosis factor receptor 2 (TNFR2)in plasma (pTNFR2)is a well-known prognostic biomarker for diabetic kidney disease (DKD) progression. The relationship between urinary TNFR2 (uTNFR2), and kidney damage is sparsely reported and poorly understood. Additionally, how uTNFR2 levels correlate with intra-kidney TNFR2 expressions in same set of patients is unknown.
Methods:
In this study, uTNFR2 (normalized by urine creatinine) and pTNFR2 levels were measured using SOMAscan proteomics analysis in a subgroup of patients with nephrotic syndrome (NS) from NEPTUNE cohort with matching urine, plasma, and kidney biopsy transcriptomic data (n=89). SOMAscan concentration of uTNFR2 was validated using ELISA assay (R&D). Glomeruli (glomerulus) and tubulointerstitium (TI) expression values for TNFRSF1B, the gene encoding TNFR2, and genes that contributed to the creation of TNF pathway score (TNFPAS) were extracted from published bulk RNA-seq profiles. Single-cell RNA-seq on kidney biopsies was employed to determine TNFRSF1B expression in kidney cells. Statistical methods employed included spearman correlation analysis and survival models to evaluate the association of uTNFR2 with quantitative digital pathology parameters and clinical outcomes.
Results:
SOMAscan uTNFR2 levels are highly correlated with ELISA measurements of the same set of samples (r=0.95, p=1e-043). uTNFR2 levels were significantly higher in patients compared to healthy controls (3.9-fold, p<0.0001). Elevated uTNFR2 correlated with lower glomerular filtration rate (GFR), higher proteinuria, increased inflammation indicated by mono-nuclear white blood cells (MWBCs), and more active TNF pathway, represented by TNFPAS. While uTNFR2 showed a significant correlation with TI TNFRSF1B mRNA, this was not observed with glomerular TNFRSF1B mRNA. uTNFR2 levels correlated with pTNFR2, although pTNFR2 had a weaker correlation with the aforementioned clinical parameters compared to uTNFR2. uTNFR2 was significantly associated with progression showing a 1.37-fold increased risk to composite endpoint of kidney failure or a 40% reduction in baseline GFR. Notably, scRNAseq analysis on kidney biopsies demonstrated enriched expression of TNFRSF1B in endothelial and immune cell clusters in the kidney, and the level of TNFRSF1B expression is higher in patients with a higher TNFPAS score compared to those with lower TNFPAS.
Conclusions:
Our integrative analysis demonstrated uTNFR2 levels are significantly associated with both cross-sectional and longitudinal outcomes in NS patients. The expression of TNFRSF1B mRNA in kidney endothelial and immune cells, along with the strong correlation of uTNFR2 over pTNFR2 with TI TNFRSF1B mRNA and MWBCs, suggests that kidney cells contributed to uTNFR2 levels. The strong correlation between uTNFR2 and TNFPAS indicates that uTNFR2 could serve as a non-invasive biomarker for kidney TNF pathway activation in patients with NS, warranting further investigation.
A version of this study is submitted at the American Society of Nephrology Kidney Week 2024
I have no potential conflict of interest to disclose.
I did not use generative AI and AI-assisted technologies in the writing process.