Abstract: FR-OR058

A Novel Nephrotic Syndrome Circulating Factor Disease Model Based on PAR-1 Activation

Session Information

Category: Glomerular

  • 1002 Glomerular: Basic/Experimental Pathology

Authors

  • May, Carl J., University of Bristol, Bristol, United Kingdom
  • Higgins, Sarah, University of Bristol, Bristol, United Kingdom
  • Barrington, Fern, University of Bristol, Bristol, United Kingdom
  • Coward, Richard, University of Bristol, Bristol, United Kingdom
  • Welsh, Gavin Iain, University of Bristol, Bristol, United Kingdom
  • Saleem, Moin, University of Bristol, Bristol, United Kingdom
Background

There is strong evidence for the role of a circulating factor in the pathogenesis of idiopathic nephrotic syndrome (iNS). Several candidates have been put forward over the years, however, none have been definitively proved. Work previously published by this group has suggested a role for Protease Activated Receptor 1 (PAR-1). Cultured podocytes respond to treatment with nephrotic syndrome relapse plasma (and not paired remission plasma) by phosphorylating VASP and increasing motility. Furthermore, the response can be blocked by knocking down the PAR-1 receptor with siRNA. A transgenic mouse was developed that expressed a podocyte specific constitutively active form of PAR-1. We hypothesise that this replicates over exposure to a circulating protease and hence causes idiopathic nephrotic syndrome.

Methods

Transgenic mice were generated by Genoway (Lyon, France). The transgene was inserted at the Rosa 26 locus. These mice were crossed with Pod- Cre mice for the developmental line and Pod- rtTA Tet- O- Cre mice for the inducible line. Kidneys were harvested and processed for histological staining and EM as indicated.

Results

The developmental PAR-1active mice were born normal, and died consistently between the ages of 39 and 45 days. They demonstrate proteinuria from the age of 14 days. The level of proteinuria increases considerably over time. By day 40 they have significantly higher blood urea and creatinine (mean 70mMol/L, 60μMol/L respectively), suggesting the mice die of renal failure. EM analysis showed a significantly thickened GBM and foot process effacement. PAS and Masson’s Trichrome staining over a time-course ranging from 8 to 40 days demonstrated an initial hypercellualrity within the Bowman’s capsule at 8 days that appear to reduce by 14 days. By 30 days there is clear evidence of fibrosis and by 40 days there is both fibrosis and sclerosis. The inducible PAR-1 Active mice show a similar phenotype although less severe. These mice die around 6 months old. We have also seen increased staining for activated PAR-1 in human iNS, compared to IgAN control biopsies.

Conclusion

This work demonstrates a clear role for the PAR-1 receptor in proteinuria, and strengthens the hypothesis that circulating factor(s) may act via this receptor. Additionally, this is a novel model for circulating factor NS, to test therapies in vivo.

Funding

  • Government Support - Non-U.S.