Background: Ex-vivo normothermic perfusion (EVNP) with a blood based perfusate has the potential to both assess viability of and repair high-risk organs prior to transplantation. However, the optimal perfusate is yet to be established. Methods: Eight paired high-risk human kidneys were placed on three hours of pressure dependent EVNP at 37oC. Kidneys were perfused with either a leukocyte-depleted packed red blood cell (PRBC) with crystalloid perfusate or a whole blood (WB) perfusate. Continuous hemodynamic and functional parameters were assessed. Core needle tissue biopsies were taken for untargeted metabolomics and lipidomics profiling. A t test was used to assess group differences in functional and hemodynamics outcomes. Results: After a mean cold ischemia time (CIT) of 54 hours, all kidneys showed high renal blood flow (RBF) through perfusion. Renal resistance (RR) increased for both groups during the first hour and then decreased to similar terminal values. The kidneys perfused with PRBC had 55 ml/min greater RBF (95% CI of 21 to 89; P=0.004) and higher total urine output (UO) (145 vs 25 ml, P= 0.002) compared to the WB group. Urinary acute kidney biomarkers of NGAL and KIM-1 were also significantly lower (mean differences of 281 and 2.1 ng/ml respectively; P<0.01) in the PRBC perfused kidneys. Compared to PRBC, within group tissue metabolic profiling revealed a similar (23% vs 18%) but a more pronounced alteration predominantly involving (branched chain) amino acid and mitochondrial energy metabolism in the WB group. Similarly, lipid profile temporal changes showed WB group were highlighted by elevation of plasma membrane and structure lipids including glycerolipids, sphingolipids, and steroids. The PRBC group had minimal temporal tissue lipid profile changes. Conclusion: Compared to WB, PRBC perfusion is superior in mitigating post-ischemia damage and facilitating function and metabolic recovery of high-risk kidneys subjected to long CITs during a three-hour ENVP.

The authors have declared no competing interest.

This work was supported by grants from the Organ Donor Research Consortium (to RVP), NIDDK (R01DK129793 [to BR], TL1DK139565 (to HY)), and Dialysis Clinics (C-4122 [to BR]).

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