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Abstract: PO1780

Investigating the Role of Complement in Membranous Nephropathy Using a Novel Ex Vivo Podocyte Model

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Moran, Sarah Margaret, Queen's University Faculty of Health Sciences, Kingston, Ontario, Canada
  • Ortiz, Carolina, The Hospital for Sick Children, Toronto, Ontario, Canada
  • Saleem, Moin, Bristol Royal Hospital for Children, Bristol, Bristol, United Kingdom
  • Cattran, Daniel C., Toronto General Hospital, Toronto, Ontario, Canada
  • Licht, Christoph, The Hospital for Sick Children, Toronto, Ontario, Canada
Background

Membranous nephropathy (MN) is an immune-mediated glomerular disease and is the commonest cause of nephrotic syndrome in adults. Progressive loss of kidney function leading to end-stage kidney disease occurs in up to one third of patients. We aimed to explore the potential functional link between antibody positive primary MN and the innate immune complement system using an ex vivo model of human podocytes.

Methods

Using a human podocyte ex vivo model, we evaluated complement activation via immunofluorescence staining for deposition of C3b and C5b-9, and functional alterations (demonstrated by cytoskeletal rearrangement) via IF staining for ActinGreen. Activation of complement via the classical pathway was used as positive control (incubation of podocytes with anti-CD59 and 50% NHS for 30 min), whereas NHS-only treated cells were used as negative control. Four patients with biopsy proven primary membranous nephropathy and detailed clinical phenotype were recruited from the Toronto GN Registry. To determine the role of complement in MN pathogenesis, podocytes were incubated with patient serum for 30 min.

Results

2/4 patients who were nephrotic, antibody (aPLA2R or THSD7A) positive with no current immunosuppression demonstrated (1) positive C3b and C5b-9 staining confirming complement activation (Fig. 1A), and (2) reduced actin staining confirming impaired cytoskeletal organization (Fig. 1B). The remaining 2 patients with negative findings were Ab positive and treated with rituximab at the time of sample collection.

Conclusion

We successfully applied a new ex vivo model using podocytes to demonstrate complement activation in non-immunosuppressed MN patients. Further studies are needed to elucidate the detailed structural and functional consequences of complement activation in MN.