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Abstract: SA-OR24

γ Isoform of Phosphoinositide 3 Kinase Plays a Critical Role in Propagation of Podocyte Injury in a Genetic Podocytopathy

Session Information

Category: Glomerular Diseases

  • 1304 Glomerular Diseases: Podocyte Biology

Authors

  • Liang, Xiaoyan, Ann and Robert H Lurie Children's Hospital of Chicago, Chicago, Illinois, United States
  • Dalal, Vidhi, Ann and Robert H Lurie Children's Hospital of Chicago, Chicago, Illinois, United States
  • Hayashida, Tomoko, Ann and Robert H Lurie Children's Hospital of Chicago, Chicago, Illinois, United States
Background

Injury to podocytes is a hallmark of primary glomerular diseases. We previously showed that pharmacological inhibition of γ isoform of phosphoinositide 3 kinase (PIK3CG) abrogates podocyte injury in a mouse model of chemically induced podocytopathy. Here, we show that genetic abrasion of PIK3CG prevents podocyte injury in a mouse model of genetic glomerular disease.

Methods

NPHS2 deletion was induced by podocyte-specific inducible Cre (NPHS2-rtTA, Tet-o-Cre) in NPHS2f/f, PIK3CG-/- mice or their wild type littermates PIK3CG+/+ by doxycycline starting at 4 weeks of age for 2 weeks. Kidney, urine and serum samples were harvested 2 and 4 weeks after the completion of Cre induction. Urine albumin and creatinine levels were measured by ELISA. Podocytes were isolated by flow sorting with anti-NPHS1 antibody and subjected to RNA sequencing. Specificity for the effect of PIK3CG deletion in podocytes was validated with inducible PIK3CG knockout mice (PIK3CG cKO-podo) treated with intravenous administration of Adriamycin, a chemically-induced model of podocytopathy.

Results

Proteinuria became apparent after 2 weeks and peaked at 4 weeks after the completion of doxycycline administration in NPHS2f/f; NPHS2-rtTA Tet-o-Cre; PIK3CG+/+ mice. In contract, NPHS2f/f; NPHS2-rtTA Tet-o-Cre; PIK3CG-/- mice, proteinuria was minimal at 2 weeks and significantly less compared to PIK3CG+/+ mice at 4 weeks after Cre recombinase activation. Electron microscope evaluation confirmed that foot processes were preserved in the PIK3CG-/- mice. While PIKC3CG is also expressed in leukocytes, PIK3CG cKO-podo mice showed significantly less proteinuria in response to Adriamycin compared to their wild-type littermates, suggesting that the protective effect of PIK3CG deletion is specific to podocytes. RNA sequencing is being performed with RNAs isolated from podocytes of NPHS2f/f, NPHS2-rtTA Tet-o-Cre, PIK3CG-/- or +/+ mice with and without disease induction.

Conclusion

Together, our data suggest that PIK3CG mediates podocyte injury and could be a novel therapeutic target for children with genetic mutation causing steroid resistant nephrotic syndrome. However, previous studies found that systemic inhibition of PIK3CG increases severe infection due to suppression of its activity in leukocytes. Genes we find by RNA sequencing in this study could be an alternative target.

Funding

  • NIDDK Support