Impact of leukoreduction on the metabolome of ovine packed red blood cells during refrigerated storage.

Background: Blood transfusion is a life-saving intervention for many species of veterinary interest, including sheep. Despite extensive research on the impact of refrigerated storage of packed red blood cells (pRBC) in humans, research on the quality of stored ovine blood is limited and storage guidelines are mostly informed by studies in humans. Human pRBC are currently stored without residual white blood cells, following selective removal of the leukocytes by filtration (leukoreduction). This process delays the onset and mitigates the progression of the storage lesion, a series of molecular changes that RBC undergo as a function of storage duration. However, leukoreduction of ovine pRBC is not routinely performed.

Materials and methods: Here we performed metabolomics analyses of non-leukoreduced (nLR) and LR pRBC from six sheep. Units were stored under standard veterinary blood bank conditions (4°C) for up to 42 days and sterilely sampled weekly for metabolomics analyses of cells and supernatants.

Results: LR-pRBC showed significantly lower levels of mono-, di- and tri-carboxylates in both the cellular and supernatant compartments, and slower accumulation of lactate and immunomodulatory succinate, fumarate and malate. The presence of residual white blood cells in the units accelerated the consumption of glucose from the media, with no increase in detectable high energy phosphate compounds (AMP). nLR showed a higher degree of purine breakdown and deamination products, (hypoxanthine, xanthine and allantoate). Elevated free fatty acids in nLR RBC are consistent with increased lipid peroxidation and lipolysis. Strong sex dimorphism was observed across all samples, independently of storage duration or leukoreduction.

Discussion: Leukoreduction of ovine pRBC delays the onset and mitigates the metabolic storage lesion to central energy and redox metabolism, while almost completely abrogating the accumulation of carboxylates in stored units.