Predictive Value of Perfusate Cell-free DNA During Hypothermic and Normothermic Machine Perfusion of Donor Kidneys.

BACKGROUND

Cell-free DNA (cfDNA) is a potential biomarker for graft (dys)function during machine perfusion, but its ability to predict posttransplant outcomes in donor kidneys remains unclear.

METHODS

We analyzed perfusate cfDNA from 57 hypothermic machine-perfused (HMP) and 56 normothermic machine-perfused (NMP) deceased donor kidneys. Nuclear cfDNA and mitochondrial cfDNA (mt-cfDNA) were quantified and compared across immediate graft function (IGF), delayed graft function (DGF), primary nonfunction (PNF), and discarded kidneys. Methylated DNA sequencing was used to analyze the cfDNA methylome during HMP to identify differentially methylated regions between IGF and PNF kidneys. Associations with donor characteristics and transplant outcomes, including serum creatinine, estimated glomerular filtration rate, and DGF duration, were assessed.

RESULTS

Perfusate cfDNA concentrations during HMP were significantly higher in PNF kidneys (0.72 ng/µL) compared with both IGF (0.48 ng/µL) and DGF kidneys (0.43 ng/µL; P = 0.030 and P = 0.031, respectively). mt-cfDNA was more abundant than nuclear cfDNA and was associated with better posttransplant graft outcome during HMP and, independently, predicted better graft outcome during NMP. Methylated DNA sequencing identified 5 differentially methylated regions between IGF and PNF located in pseudogenes or intergenic cytosine-phosphate-guanine dinucleotide islands.

CONCLUSIONS

cfDNA-especially mt-cfDNA-measured during machine perfusion is associated with posttransplant graft outcome during both HMP and NMP. Therefore, it may serve as a candidate biomarker that warrants validation in larger prospective studies.