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Abstract: FR-PO402

Urothelial-Specific Insulin Receptor Deletion Suppresses Host Defenses of the Kidney and Bladder

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Murtha, Matthew J., Ohio State University Hospital, Columbus, Ohio, United States
  • Schwartz, Laura, Nationwide Children''s Hospital, Columbus, Ohio, United States
  • Bender, Kristin, The Research Institute at Nationwide Children''s Hospital, Columbus, Ohio, United States
  • Li, Birong, Nationwide Children's Hospital, Columbus, Ohio, United States
  • Eichler, Tad, The Research Institute at Nationwide Childrens Hospital, COLUMBUS, Ohio, United States
  • Spencer, John David, The Research Institute at Nationwide Children's, Columbus, Ohio, United States
Background

In people with diabetes mellitus (DM), urinary tract infection (UTI) is more common and has worse outcomes. With DM, UTI is more likely to cause acute kidney injury, which increases the risk of chronic and end-stage kidney disease. The mechanisms that predispose diabetics to UTI remain elusive. To investigate the significance of insulin signaling on kidney and urothelial host defense, we genetically deleted the insulin receptor (IR) in murine urothelium.

Methods

Urothelial-specific IR knock-out mice (IRKO) were generated by breeding homozygous mice for the floxed Insr gene (insulin receptor gene) with transgenic mice that have tamoxifen-inducible Cre recombinase under the Uroplakin 2 (Upk2) promoter. Littermates lacking the Upk2-Cre transgene served as controls (IRflox). To determine if urothelial-specific IR deletion impacts host defense, female mice were transurethrally infected with uropathogenic E. coli (UPEC). At 24, 48, and 72 hrs post infection, UPEC burden was enumerated in urine, bladder, and kidney. To assess why IRKO mice have increased UTI susceptibility, human urothelial cells were assayed in vitro using siRNA to silence IR and investigate if silencing IR disrupts urothelial barrier formation.

Results

PCR confirmed urothelial-specific Cre-LoxP recombination and IR transcript deletion in bladders of IRKO mice. Compared to IRflox, IRKO mice exhibit normal development, no evidence of hyperglycemia, and normal bladder/kidney histology. Following transurethral UPEC infection, the bladders of IRKO mice developed significantly pronounced and prolonged inflammation and edema. This was accompanied by significantly greater UPEC burden in the urine, bladder, and kidneys at all time points. siRNA-mediated INSR silencing in human bladder cells in vitro resulted in marked differences in urothelial proliferation and migration.

Conclusion

These results suggest that intact insulin signaling is critical for UTI defense. Also, they indicate that hyperglycemia alone does not explain increased UPEC susceptibility. Finally, they indicate that abnormal bladder defenses, including a reduced ability to regenerate an impermeable urothelial barrier, increases the likelihood for significant bladder and kidney infection. Additional studies are warranted to identify how IR deletion impacts urothelial defenses.

Funding

  • NIDDK Support