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Abstract: PO0874

Caspase Inhibition in a Mouse Model of Prenatal Ureteropelvic Obstruction Rescues Normal Ureter Development

Session Information

Category: Development, Stem Cells, and Regenerative Medicine

  • 500 Development, Stem Cells, and Regenerative Medicine

Authors

  • Villiger, Ross, University of Hawaii at Manoa, Honolulu, Hawaii, United States
  • Harrison-Chau, Malia H., University of Hawaii at Manoa, Honolulu, Hawaii, United States
  • Ortega, Michael, University of Hawaii at Manoa, Honolulu, Hawaii, United States
  • Fogelgren, Ben, University of Hawaii at Manoa, Honolulu, Hawaii, United States
Background

The most common cause of congenital obstructive nephropathy is ureteropelvic junction obstruction (UPJO). We previously described a unique mouse model of in utero UPJOs through urothelial knockout of Exoc5, a central subunit of the exocyst trafficking complex. In this neonatal-lethal model, UPJO formation is preceded by urothelial cell death in the ureter between E16.5 and E17.5. Here, we investigated if normal ureter development could be restored in this mouse model by blocking cell death pathways, and conversely, if we could induce UPJOs by simply activating urothelial cell death during ureter development.

Methods

We utilized the Cre-lox system to achieve either targeted gene knockout or activation during mouse embryonic development. For inhibition of cell death pathways in Exoc5FL/FL;Ksp-Cre ureters, we performed IP injections of caspase inhibitors into pregnant mice at gestational day E16.5. Also, diphtheria toxin A (DTA) mice crossed with Ksp-CreERT2 mice were used to investigate the effect of inducing urothelial cell death with tamoxifen administration at E16.5.

Results

Morphologically, dying Exoc5-KO urothelial cells appeared more necrotic than apoptotic, and they were negative for cleaved PARP and active caspase-3. However, a single IP injection of pan-caspase inhibitor z-VAD-FMK at E16.5 rescued ureter development in all Exoc5FL/FL;Ksp-Cre mice analyzed. At E18.5, all z-VAD-FMK treated embryos displayed patent ureters with no hydronephrosis (n=9 from multiple litters). If followed past birth, z-VAD-FMK treated Exoc5FL/FL;Ksp-Cre mice survived to adulthood. Interestingly, caspase-1 inhibitor Ac-YVAD-cmk also rescued ureter development when injected at E16.5, supporting the hypothesis that a non-apoptotic pathway is responsible for urothelial cell death in this mouse model. Conversely, DTA-induced urothelial cell death in E16.5 ureters showed evidence of UPJO formation by E18.5.

Conclusion

Based on these findings, we have shown that urothelial cell death is a critical event leading to UPJO pathogenesis and lethality in our mouse model. The data suggest inflammasome-associated caspase-1 may play a role in activating cell death in urothelial cells with disrupted exocyst trafficking.

Funding

  • NIDDK Support