Kidney Week

Abstract: PO0836

Stimulus and Cell-Specific Responses to Volume Depletion, Ischemia, and COVID-19

Session Information

• COVID-19: Clinical and Basic Science Characteristics
  October 22, 2020 | Location: On-Demand
  Abstract Time: 10:00 AM - 12:00 PM

Category: Coronavirus (COVID-19)

• 000 Coronavirus (COVID-19)

Authors

• Xu, Katherine, Columbia University Irving Medical Center, New York, New York, United States

Katherine Xu,

• Shen, Tian, Columbia University Irving Medical Center, New York, New York, United States

Tian Shen,

• Stauber, Jacob, Columbia University Irving Medical Center, New York, New York, United States

Jacob Stauber,

• Kiryluk, Krzysztof, Columbia University Irving Medical Center, New York, New York, United States

Krzysztof Kiryluk,

• D'Agati, Vivette D., Columbia University Irving Medical Center, New York, New York, United States

Vivette D. D'Agati,

• Barasch, Jonathan M., Columbia University Irving Medical Center, New York, New York, United States

Jonathan M. Barasch,

Background

A stimulus-response map of the injured kidney might reflect a common stereotyped “final common pathway” or alternatively, a set of “stimulus-specific”, “cell-specific”, and “time-specific” read outs.

Methods

We expressed uracil phosphoribosyl transferase (Uprt) in specific segments of the kidney (Rosa-Uprt^f/+;Hoxb7Cre and Rosa-Uprt^f/+;Atpase6v1b1Cre) and identified nascent RNA by 4-thiouracil pulse labeling after initiating two clinically relevant stimuli. Thio-RNA was isolated from intact kidneys with thio-biotin beads. We examined human biopsies with RNAScope to confirm patterns of gene expression.

Results

Hierarchical clustering of z-score transformed normalized counts (padj<0.05 and log₂ fold changes ≥1) demonstrated that 3180 genes distinguished volume depletion from arterial ischemia in Hoxb7Cre purified genes and 1405 genes in AtpaseCre purified genes, respectively. The vast majority of these stimulus specific genes (96% ischemia and 83% volume depletion) constituted cell specific responses as well (exclusive to Hoxb7Cre or AtpaseCre purified RNA). Pathway analyses demonstrated immune regulation, complement and the coagulation pathways in ischemic disease, whereas volume depletion activated inhibitors of inflammatory pathways and metabolic Foxo signaling, clock genes, and lipid metabolism. Timed evaluation demonstrated distinct early and late responses.

To confirm the unique responses to clinical injury, we examined the most prominent mouse genes responding to ischemia, LCN2 (NGAL) and HAVCR1 (KIM1) in human ATN kidneys (associated with NSAIA (1), hypotension (1), DGF (1), nephrectomy (2), COVID-19 (8), unknown etiology (1)), together with segment specific anchor genes (LRP2, AQP2). LCN2 and HAVCR1 expression was cell specific (HAVCR1: proximal tubule, LCN2 : Loop of Henle and Collecting Ducts > Proximal Tubules) in the majority of biopsies. LCN2 and HAVCR1 overlapped in the proximal tubule in a minority of severely affected kidneys.

Conclusion

KDIGO criteria for AKI imply that any elevation of serum creatinine marks injury to the nephron. Yet, without resorting to destructive methods of dissection or cell isolation, we identify snapshots of genes induced by different stimuli, expressed by different cells, specific in timing, constituting different sets of unrelated molecular responses.

Funding

• NIDDK Support