Phenotype of Renal Tubular Cell Death During Delayed Graft Function

S. Jain,¹ R. Plenter,¹ T. Nydam,¹ C. Ruller,¹ C. Edelstein,^1,2 A. Jani.^1,2

¹University of Colorado, Aurora, CO
²Veterans Affairs Medical Center, Denver, CO.

Meeting: 2015 American Transplant Congress

Abstract number: D99

Keywords: Apoptosis, Kidney transplantation, Necrosis, Renal ischemia

Background: Delayed graft function (DGF) independently predicts reduced 5 yr kidney transplant survival. Treatments of DGF are lacking. Cold ischemia (CI) is a significant risk factor for DGF but the mechanism by which CI leads to DGF is unknown. The aim of this study was to determine the effects of CI on donor kidneys alone versus CI followed by warm reperfusion after kidney transplant (CI+Txp). We hypothesized that CI alone would produce a different injury phenotype to CI+Txp.

Methods: Male C57BL6 mice aged 8-12 weeks, were subjected to mouse kidney transplant. Donor kidneys were subjected to 3 hours CI in UW solution, and processed immediately or subjected to syngeneic mouse kidney transplant. Renal function was assessed by serum creatinine. Renal tubular cell (RTC) apoptosis and necrosis were quantified by an independent nephropathologist. TLR4, RIP3, cleaved BID, cleaved caspase-8 (CC8) and cleaved caspase-3 (CC3) were examined by immunoblot.

Results: CI+ Txp resulted in a significantly increased serum creatinine versus transplant without CI (Txp alone) (n=3; *p<0.05 vs. Txp alone). CI alone results in increased RTC apoptosis and CC3 but did not result in necrosis. In contrast, CI +Txp led to; (1) increased apoptotic factors CC8, cleaved BID and CC3, and thus increased RTC apoptosis; (2) increased RTC necrosis that was associated with increased RIP3 and TLR4.

	Control	Donor Kidney (CI)	Transplant Kidney (CI+ Txp)
Apoptosis/10hpf	0.6±0.3	10.33±0.8*	13.33±0.3*
ATN Score	0.06±0.03	0.1±0.05	4.83±0.1*
CC3	0.04±0.02	0.37±0.02*	0.21±0.04*†
CC8	ND	ND	0.13±0.06*†
BID	0.1±0.04	0.23±0.03	0.53±0.01*†
TLR4	0.5±0.3	ND	0.34±0.01*†
RIP3	ND	ND	0.65±0.2*†

n=3; *p<0.05 vs. control,†p<0.05 vs. CI; ND=not detected Conclusions: Thus CI results in RTC apoptosis alone, whereas CI +Txp is characterized by a different injury phenotype that includes RTEC apoptosis and also programmed necrosis, that is associated with an increase in RIP3 and TLR4. Understanding the phenotype of injury following prolonged CI and kidney transplant may lead to novel therapies for DGF.

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