Abstract: FR-PO701

Blockade of TNF Alpha Signaling Reverses Toxic Effects of Focal Segmental Glomerulosclerosis Sera on Podocyte Adhesion Independently of Serum TNFa Level

Session Information

Category: Glomerular

  • 1002 Glomerular: Basic/Experimental Pathology

Authors

  • Torban, Elena, McGill University Health Center, Montreal, Quebec, Canada
  • Kachurina, Nadezda, McGill University Health Center, Montreal, Quebec, Canada
  • Chung, Chen-Fang, McGill University Health Center, Montreal, Quebec, Canada
  • Pessina, Katarina Sonia, McGill University Health Center, Montreal, Quebec, Canada
  • Kitzler, Thomas, McGill University Health Center, Montreal, Quebec, Canada
  • Alachkar, Nada, The Johns Hopkins University, Baltimore, Maryland, United States
  • Goodyer, Paul R., McGill University Health Center, Montreal, Quebec, Canada
  • Cybulsky, Andrey V., McGill University Health Center, Montreal, Quebec, Canada
Background

Patients with primary FSGS often progress to end stage renal disease and require renal transplantation. In about half, the disease recurs in the allograft, suggesting a circulating podocyte-toxic factor in the host. We and others have reported clinical improvement following TNFα blockade in a subset of recurrent FSGS patients. Likewise, blockade of TNFα signaling in cultured human podocytes reverses the toxicity of some FSGS sera. In this study, we tested 100 FSGS serum/plasma samples for in vitro podocyte toxicity and responsiveness to TNFα blockade, and measured serum TNFα levels or serum effects on expression of podocyte TNFα pathway genes.

Methods

Plasma/serum samples from steroid-resistant nephrotic syndrome patients with biopsy-confirmed FSGS were tested for toxicity to human podocytes, as judged by disassembly of focal adhesion complexes (FACs) (Kachurina, AJP-R, 2016). Pre-treatment with blocking anti-TNFα Receptor I&II antibodies was used in some experiments. Expression of 8 TNFα pathway genes, whose expression differs significantly between FSGS and control samples in the Nephroseq database, was assessed by RT-qPCR.

Results

A significant loss of FACs (less than 60% of control) was induced by 47% of FSGS samples. Among these, TNFα blockade reversed podocyte toxicity in 24%. Neither serum toxicity nor responsiveness to TNFα blockade in podocytes correlated with circulating TNFα levels. Significant changes in expression of TNFα signaling pathway genes were induced by exposure to FSGS sera that disrupted podocyte FACs and that could be reversed by TNFα blockade, but not by sera from healthy controls or rheumatoid arthritis patients.

Conclusion

Sera from a subset of primary FSGS patients cause striking dispersion of podocyte FACs. This activity is unrelated to serum TNFα level but may be due to the effect of FSGS serum on activation of endogenous podocyte TNFα pathway signaling. Our assay may be useful in identifying patients at high risk for recurrence of FSGS in the renal allograft and who may potentially benefit from TNFα blockade to attenuate podocyte injury.

Funding

  • Government Support - Non-U.S.