Kidney Week

Abstract: TH-PO555

Mice with a Pax2 Missense Variant Are Susceptible to Experimental FSGS and Display Impaired Glomerular Repair

Session Information

• Glomerular Diseases: From Inflammation to Fibrosis - I
  November 02, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1401 Glomerular Diseases: From Inflammation to Fibrosis

Authors

• Cunanan, Joanna, Toronto General Research Institute, Toronto, Ontario, Canada

Joanna Cunanan,

• Sharif, Bedra U., Toronto General Research Institute, Toronto, Ontario, Canada

Bedra U. Sharif,

• Rajyam, Sriya, Toronto General Research Institute, Toronto, Ontario, Canada

Sriya Rajyam,

• Udwan, Khalil, Toronto General Research Institute, Toronto, Ontario, Canada

Khalil Udwan,

• Rana, Akanchaya, Toronto General Research Institute, Toronto, Ontario, Canada

Akanchaya Rana,

• De Gregorio, Vanessa Sara, Toronto General Research Institute, Toronto, Ontario, Canada

Vanessa Sara De Gregorio,

• Ricardo, Samantha, Toronto General Research Institute, Toronto, Ontario, Canada

Samantha Ricardo,

• Caparali, Emine Bilge, Toronto General Research Institute, Toronto, Ontario, Canada

Emine Bilge Caparali,

• John, Rohan, Toronto General Hospital, Toronto, Ontario, Canada

Rohan John,

• Farkona, Sofia, Toronto General Research Institute, Toronto, Ontario, Canada

Sofia Farkona,

• Konvalinka, Ana, Toronto General Research Institute, Toronto, Ontario, Canada

Ana Konvalinka,

• Weins, Astrid, Brigham and Women's Hospital, Boston, Massachusetts, United States

Astrid Weins,

• Pollak, Martin, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States

Martin Pollak,

• Barua, Moumita, Toronto General Research Institute, Toronto, Ontario, Canada

Moumita Barua,

Background

FSGS is a form of chronic kidney disease characterized by podocyte loss. Our team previously reported that PAX2 pathogenic missense variants account for 4% of adults with FSGS. PAX2 regulates glomerular development and its expression persists in adult parietal epithelial cells (PECs), postulated to serve as a reservoir for cells including podocytes. We hypothesize that in humans and mice with pathogenic PAX2 missense variants, PEC-mediated podocyte regeneration is impaired.

Methods

FSGS induced by Adriamycin was performed on wildtype mice and mice with a Pax2 missense variant (termed Pax2^MV). Kidney tissue were analyzed by histology and immunostaining. Glomeruli were isolated and subjected to mass spectrometry (MS), analyzed by Gene Ontology (GO) Enrichment Analysis. Kidney tissue from relatives with PAX2-associated FSGS was also analyzed.

Results

At embryonic day 16.5, mouse wildtype kidneys showed overlapping expression of PAX2 and WT-1 in the condensed mesenchymal cells until PEC and podocyte differentiation, supporting a close lineage relationship. Pax2^MV had reduced nephron number but displayed only minor differences in glomerular function at baseline. Adriamycin-injured Pax2^MVmice showed more severe FSGS compared to wildtype, including decreased podocyte numbers and increased albuminuria. Adriamycin-injured Pax2^MVmice showed PAX2-expressing glomerular tuft cells, which were rarely observed in injured wildtype and were similar to histological findings from PAX2-associated FSGS patients, suggesting a role of these ectopic PAX2-expressing cells in pathogenesis. GO processes obtained from isolated glomeruli demonstrated maladaptive repair in Pax2^MV, including increased epithelial cell migration, decreased cell adhesion, de-regulated actin cytoskeleton dynamics, and in-utero embryonic development; while GO terms of normal repair mechanisms including regulation of cell morphogenesis, cell adhesion, cell-cell junction assembly, and actin cytoskeleton organization were enriched in wildtype.

Conclusion

Our findings support decreased glomerular regeneration in Pax2^MV mice compared to wildtype. We are next pursuing glomerular single-cell RNA sequencing to characterize the role of PECs in this process.

Funding

• Government Support – Non-U.S.