Flavin Mononucleotide as a Biomarker of Organ Quality-A Pilot Study

Abstract

Background: Flavin mononucleotide (FMN), released from damaged mitochondrial complex I during hypothermic liver perfusion, has been shown to be predictive of 90-day graft loss. Normothermic machine perfusion (NMP) and normothermic regional perfusion (NRP) are used for organ reconditioning and quality assessment before transplantation. This pilot study aimed to investigate the changes of FMN levels during normothermic reperfusion of kidneys, livers, and lungs and examine whether FMN could serve as a biomarker to predict posttransplant allograft quality.

Methods: FMN concentrations, in perfusates collected during NMP of kidneys, abdominal NRP, and ex vivo lung perfusion, were measured using fluorescence spectrometry and correlated to the available perfusion parameters and clinical outcomes.

Results: Among 7 transplanted kidneys out of the 11 kidneys that underwent NMP, FMN levels at 60 minutes of NMP were significantly higher in the allografts that developed delayed graft function and primary nonfunction (P = 0.02). Fifteen livers from 23 circulatory death donors that underwent NRP were deemed suitable for transplantation. Their FMN levels at 30 minutes of NRP were significantly lower than those not procured for transplantation (P = 0.004). In contrast, little FMN was released during the 8 lung perfusions.

Conclusions: This proof of concept study suggested that FMN in the perfusates of kidney NMP has the potential to predict posttransplant renal function, whereas FMN at 30 minutes of NRP predicts whether a liver would be accepted for transplantation. More work is required to validate the role of FMN as a putative biomarker to facilitate safe and reliable decision-making before embarking on transplantation.

FIGURE 1.

A, Concentration curves of FMN generated by fluorescence spectrometry. B, Comparison of the FMN fluorescence readings of fresh samples, samples stored at 4°C for 1 d and 7 d, and at –80°C for 28 d (n = 3).

FIGURE 2.

A, The FMN fluorescence readings of the perfusates taken before and at 60 min of normothermic machine perfusion of kidneys (n = 11). B, Correlation of the FMN fluorescence readings in the perfusates at 60 min of NMP with QAS (n = 11). C, Comparison of the FMN levels at 60 min of NMP in the kidneys that had initial function (n = 4) to those of the ones that did not (n = 3). FMN, flavin mononucleotide; NMP, normothermic machine perfusion; QAS, quality assessment score.

FIGURE 3.

A, The changes in the FMN fluorescence readings during the 2 h of abdominal normothermic regional perfusion. B, Comparison of the FMN levels at 30 min of NRP in the livers that were accepted for transplantation (n = 15) to those of the ones that were declined (n = 8). C, ROC analysis of FMN levels at 30 min of NRP on prediction of livers being accepted for transplantation after NRP. AUC, area under the receiver-operating characteristic curve; CI, confidence interval; FMN, flavin mononucleotide; NRP, normothermic regional perfusion. ROC, receiver-operating characteristic curve.