Abstract
Ex-situ machine perfusion (MP) has been increasingly used to enhance liver quality in different settings. Small animal models can help to implement this procedure. As most normothermic MP (NMP) models employ sub-physiological levels of oxygen delivery (DO2), the aim of this study was to investigate the effectiveness and safety of different DO2, using human red blood cells (RBCs) as oxygen carriers on metabolic recovery in a rat model of NMP. Four experimental groups (n = 5 each) consisted of (1) native (untreated/control), (2) liver static cold storage (SCS) 30 min without NMP, (3) SCS followed by 120 min of NMP with Dulbecco-Modified-Eagle-Medium as perfusate (DMEM), and (4) similar to group 3, but perfusion fluid was added with human RBCs (hematocrit 15%) (BLOOD). Compared to DMEM, the BLOOD group showed increased liver DO2 (p = 0.008) and oxygen consumption (2) (p < 0.001); lactate clearance (p < 0.001), potassium (p < 0.001), and glucose (p = 0.029) uptake were enhanced. ATP levels were likewise higher in BLOOD relative to DMEM (p = 0.031). 2 and DO2 were highly correlated (p < 0.001). Consistently, the main metabolic parameters were directly correlated with DO2 and 2. No human RBC related damage was detected. In conclusion, an optimized DO2 significantly reduces hypoxic damage-related effects occurring during NMP. Human RBCs can be safely used as oxygen carriers.
Highlights
Liver machine perfusion (MP) was introduced in the clinical setting by Guarrera and colleagues [1] in 2009
We reviewed all those reporting rat ex-situ perfusions with recirculating fluid and 39 of them described normothermic machine perfusion (NMP)/normothermic machine reperfusion (NMRP)
Twenty rats were randomly assigned to four experimental groups (n = 5/group): (1) Dulbecco-Modified-Eagle-Medium as perfusate (DMEM) whose livers were subjected to in-situ cold flushing, procured, cold stored for 30 min, and ex-situ perfused for 120 min with a perfusion fluid without an oxygen carrier; (2) BLOOD, whose livers were subjected to all the procedures of the DMEM group, but NMP perfusion fluid included human red blood cells (RBC) as an oxygen carrier; (3) Cold storage, whose livers were subjected to in-situ cold flushing, procured, and
Summary
Liver machine perfusion (MP) was introduced in the clinical setting by Guarrera and colleagues [1] in 2009. Over the last ten years, 94 research papers were based on liver MP use in rodents We reviewed all those reporting rat ex-situ perfusions with recirculating fluid and 39 of them described NMP/NMRP (Supplementary Materials: a brief review of the literature is provided in Tables S1 and S2). The infrequent use of OxC could be related to the high number of rats needed to be used as blood donors (at least 3-4 animals/experiment) and unavailability of other oxygen carriers. Was observed in the absence of an oxygen carrier, the increased oxygen consumption (VO2) needed to control the reperfusion injury suggests the opportunity to increase DO2 during reperfusion [8,17] To this purpose, two main strategies may be adopted: use of non-cellular hemoglobin [18] or employment of other sources of blood [13]. The use of non-murine red blood cells can allow for the reduction of the number of animals/experiments in full respect of the 3Rs principles (Refinement, Reduction, and Replacement) [19]
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