Kidney Week

Abstract: SA-PO0754

Collagen Type IV Alpha-1 (Col4a1) Is Necessary for Glomerular Repair Through Pax2 Regulation

Session Information

• Glomerular Diseases: Profiling Through Multiomics
  November 08, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology

Authors

• Cunanan, Joanna, Division of Nephrology and Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada

Joanna Cunanan, MS

• Maksimowski, Nicholas, Division of Nephrology and Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada

Nicholas Maksimowski

• Zhang, Daniel, Division of Nephrology and Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada

Daniel Zhang

• De Gregorio, Vanessa Sara, Division of Nephrology and Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada

Vanessa Sara De Gregorio, MS

• Ricardo, Samantha, Division of Nephrology and Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada

Samantha Ricardo

• Caparali, Emine Bilge, Division of Nephrology and Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada

Emine Bilge Caparali, MD

• John, Rohan, Division of Nephrology and Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada

Rohan John, MD

• Konvalinka, Ana, Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada

Ana Konvalinka, MD, PhD

• Barua, Moumita, Division of Nephrology and Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada

Moumita Barua, MD

Background

Podocyte loss in glomerular disease is challenging to treat due to their terminal differentiation. Glomerular parietal epithelial cells (PECs) express developmental markers like the transcription factor PAX2. Our previous work suggests that Pax2 mutant (Pax2^A220G/+) mice exhibit impaired PEC-mediated podocyte regeneration. Here, we investigate the molecular mechanisms underlying this deficient repair.

Methods

Glomeruli from Pax2^A220G/+ and wildtype mice, at baseline and after Adriamycin-induced injury, were analyzed using mass spectrometry proteomics.

Results

While wildtype mice recovered from injury, Pax2^A220G/+ mice developed persistent albuminuria and podocyte foot process effacement (Fig-1A). To explore molecular drivers of repair, we analyzed an external glomerular single-cell RNA-sequencing dataset from Adriamycin-injured wildtype mice, identifying 40 top-ranked ligand-receptor pairs involved in glomerular repair. Of these, only collagen type IV alpha-1 (COL4A1) was differentially expressed in Pax2^A220G/+ versus wildtype glomeruli after injury in our proteomics data. The Col4a1 gene is also a predicted PAX2 target for expression, determined through bioinformatics-based analysis of known transcription factor binding site motifs (Fig-1B). COL4A1 expression was reduced in Pax2^A220G/+ mice post-injury, validated by capillary gel electrophoresis and immunohistochemistry. A luciferase assay in HEK293 cells transfected with mutant Pax2 (corresponding to the same mutation in Pax2^A220G/+ mice) showed lack of COL4A1 activation (Fig-1C).

Conclusion

Studies show COL4A1 contributes a flexible matrix during kidney development and this may be harnessed in glomerular repair. Our data suggests reduced PAX2-mediated Col4a1 transcription in the glomerulus leads to deficient COL4A1 expression, associated with abnormal repair, exacerbated podocyte loss, and worsened disease in Pax2^A220G/+ mice (Fig-1D).

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025wwgmvrgc