Abstract: FR-PO164
Long-Term Maladaptive Repair of the Kidney Medulla after Reversal of Ureteric Obstruction
Session Information
- AKI: Mechanisms
October 25, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 103 AKI: Mechanisms
Authors
- Vanichapol, Thitinee, The University of Auckland, Auckland, New Zealand
- Davidson, Alan J., The University of Auckland, Auckland, New Zealand
- de Caestecker, Mark P., Vanderbilt University Medical Center, Nashville, Tennessee, United States
Background
There is a long-term decrease in urinary concentrating capacity (UCC) after urinary tract obstruction. UCC is dependent on the correct cellular organization and function of the inner medulla (IM), but little is known about the regenerative potential of the IM, nor the long-term structural and functional effects after reversal of urinary tract obstruction.
Methods
Ureteric clamps were placed in mice for 5 to 8 days to induce reversible unilateral ureteric obstruction (R-UUO), with contralateral nephrectomies to assess renal function. GFR and urine osmolality were measured, and kidneys harvested at Day 28 and 84. Renal histology (PAS), immunostaining, and genetic lineage analysis performed using Six2 and HoxB7 Cre; tdTomato Cre reporter mice. scRNA-Seq was performed using FLEX on isolated renal medullas.
Results
Survivable R-UUO clamp times varied between mouse strains, but all showed a marked decrease in UCC 84 days after R-UUO. Renal histology showed IM damage with papillary necrosis, followed by active tubular repair. Most tubular structures were repopulated by day 28, and the IM appeared indistinguishable from controls by day 84. Unsupervised clustering of scRNA-Seq data identified multiple clusters of loop of Henle (LOH), collecting duct (CD), and endothelial cell (EC) subtypes, likely reflecting their spatial location in the IM. There was a reduction in subsets of these cells and appearance of “injured” clusters at day 28 post R-UUO, with a loss of vasa recta ECs and persistence of injured CD and LOH cells at day 84. Inflammation and fibrosis genes were also increased in “non-injured” CD and LOH populations, suggestive of a persistent inflammatory state. Immunostaining confirmed a reduction in IM capillary density (CD31) and LOH (AQP1). However, CD markers recovered and expanded in the distal IM by day 84. Since dedifferentiation may affect cell identification, we confirmed these findings independently by genetic lineage labelling studies using Six2-Cre and HoxB7-Cre mice, respectively.
Conclusion
These data indicate that despite robust repair, there is a persistent defect in UCC associated with incomplete repair of vasa recta and LOH cell types in the IM, and persistence of “injured” LOH-derived cells. The CD recovers and expands but also retains populations of injured and inflammatory cells, suggestive of a persistent maladaptive repair state.
Funding
- NIDDK Support