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Kidney Week

Abstract: PO0158

CDK4-Related Tubular Epithelial Cell Proliferation Was Regulated by Pax2 in Renal Ischemia-Reperfusion Injury

Session Information

  • AKI Mechanisms - 1
    October 22, 2020 | Location: On-Demand
    Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Sako, Keisuke, Kanazawa University, Kanazawa, Ishikawa, Japan
  • Yamamura, Yuta, Kanazawa University, Kanazawa, Ishikawa, Japan
  • Iwata, Yasunori, Kanazawa University, Kanazawa, Ishikawa, Japan
  • Sakai, Norihiko, Kanazawa University, Kanazawa, Ishikawa, Japan
  • Shimizu, Miho, Kanazawa University, Kanazawa, Ishikawa, Japan
  • Furuichi, Kengo, Kanazawa Medical University School of Medicine, Uchinada, Ishikawa, Japan
  • Wada, Takashi, Kanazawa University, Kanazawa, Ishikawa, Japan
Background

Pax2 is a transcription factor necessary for kidney development. It has been reported that Pax2 is reactivated in tubular epithelial cells at the recovery phase of kidney injury. However, the roles of Pax2 in the regeneration of kidney injury is unknown. Here in we hypothesized that Pax2 reactivation is involved in the regeneration of impaired tubular cells.

Methods

To determine the function of Pax2 reactivation in mouse proximal tubules, we generated kidney proximal tubule-specific Pax2 conditional knockout (KO) mice. The conditional KO mice were established by KAP (kidney androgen regulated protein) Cre mice and Pax2 flox mice. Six to eight-week old male mice were used for ischemia-reperfusion (I/R) injury (left kidney, 60 minutes). The intensity of cell proliferation and fibrosis of injured kidney was evaluated. A Pax2 inhibitor (EG1) was used to evaluate the roles of Pax2 in the hypoxia condition of cultured tubular epithelial cells (O2 5%, 24 hour).

Results

The number of Pax2-positive cells and Pax2 mRNA increased after I/R injury. However, the reactivation of Pax2 was significantly suppressed in conditional KO mice (p<0.05). In analysis of interstitial fibrosis, the area of Sirius red staining and the content of hydroxyproline (chemical marker of collagen) were higher those observed in conditional KO mice 14 days after I/R injury (p<0.05). Moreover, the expression of CTGF was significantly increased in conditional KO mice (p<0.05). Furthermore, the number of Ki-67 and BrdU positive cells was significantly decreased in the conditional KO mice 14 days after I/R injury (p<0.001). In the cell cycle, the number of CDK4-positive cells (G1 phase marker) and the expression of CDK4 were significantly decreased in conditional KO mice (p<0.001). In vitro study revealed that CDK4 mRNA and protein expression were decreased by administration of Pax2 inhibitor, however Cyclin D mRNA and protein expression were not decreased by the inhibitor.

Conclusion

Pax2 reactivation may be involved in CDK4 related tubular epithelial cell proliferation. Inadequate Pax2 reactivation (or suppression of Pax2 expression) may be related in exacerbation of kidney fibrosis.