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Abstract: FR-PO408

Diabetic Condition Induces Hypertrophy and Apoptosis in Parietal Epithelial Cells Through Mitotic Catastrophe

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Kawaguchi, Takahisa, Keio University, Tokyo, Japan
  • Hasegawa, Kazuhiro, Keio University, Tokyo, Japan
  • Wakino, Shu, Keio University, Tokyo, Japan
  • Itoh, Hiroshi, Keio University, Tokyo, Japan
Background

Podocyte hypertrophy and apoptosis are two hallmarks of diabetic glomeruli; however, little information is available about changes in parietal epithelial cells (PECs). We hypothesized that diabetes induces hypertrophy and apoptosis in PECs in a similar manner and causes damage. This study aimed to elucidate the effects of a diabetic condition on PECs in vitro and in vivo.

Methods

Conditionally immortalized mouse PECs were exposed to 5 mmol/L glucose (NG), 30 mmol/L glucose (HG), and angiotensin-II (AT-II) at the dosage of 10−6 mol/L or aldosterone at 10−7 mol/L. Hypertrophy and cell cycle analysis were assessed by flow cytometry. Podocyte apoptosis was ascertained by Annexin V/PI staining, Hoechst 33342 staining, and caspase 3/7 staining. For in vivo studies, streptozotocin-induced diabetic mice, db/db diabetic mice, and BTBR ob/ob mice were used as diabetic mouse models. Histomorphology of the renal tissue was observed using light microscopy and transmission electron microscopy (TEM). PEC apoptosis was assessed using the TUNEL assay and cleaved caspase-3 staining.

Results

In cultured PECs, HG induced hypertrophy, whereas AT-II and aldosterone failed to induce hypertrophy. Flow cytometry revealed that HG also induced PEC apoptosis in a dose-dependent manner and S-phase arrest of PECs, suggesting mitotic catastrophe of PECs. In TEM, PECs exhibited enlargement of both the cytoplasm and nucleus at the ultrastructural level in all diabetic mouse models. PAX 8 staining revealed PEC nuclear hypertrophy in diabetic mice, whereas the cell number of PECs remained unaltered, suggesting that PECs in diabetic condition underwent DNA replication with a mitotic defect. However, an increase in apoptotic PECs was not observed in diabetic glomeruli.

Conclusion

PECs in diabetic condition are in a state of dysregulation of proliferation similar to mitotic catastrophe. As PECs are considered a precursor of podocytes, this injury to PECs might impair glomerular regeneration. Nevertheless, further studies are warranted to elucidate the potential pathological role of morphological changes in PECs in diabetic kidney disease.