Hematology Education: the education program for the annual congress of the European Hematology Association | 2013; 7(1) | 389 | A. D’Alessandro L. Zolla Department of Ecological and Biological Sciences, University of Tuscia, Largo dell’Università, Viterbo, Italy Correspondence: Angelo D’Alessandro E-mail: a.dalessandro@unitus.it Acknowledgments: ADA and LZ are supported by the Italian National Blood Center (Centro Nazionale Sangue, CNS, Istituto Superiore Sanità, Rome, Italy). Hematology Education: the education program for the annual congress of the European Hematology Association 2013;7:389-396 Biochemistry of red cell aging in vivo and storage lesions Introduction Aging of red blood cells (RBCs) in vivo and in vitro represents a key biomedical issue. Human RBCs have an approximate lifespan of 120 days in vivo. In most countries, the shelf-life of RBC concentrates stored under blood bank conditions is limited to 42 days. Normal human RBCs all survive to about the same age, which implies the existence of a molecular countdown that triggers a series of changes leading to removal by the reticuloen- dothelial system (Table 1, Figure 1). 1,2 These changes share some distinct features with pro- grammed cell death of nucleated cells, which prompted Lang’s group to coin the term ‘eryp- tosis’, i.e. referring to erythrocyte-specific apoptosis. 3 Storage under blood bank conditions results in the exacerbation of most of these changes and a shortening of RBC lifespan, a phenome- non referred to as the ‘storage lesions’. 4-6 However, it should be remembered that an RBC concentrate unit already contains nor- mally distributed (partly aged) RBC popula- tions. It is still a matter of debate as to whether and to what extent transfusion of RBC concentrate units older than 14 days might cause untoward effects in certain categories of recipients (e.g. traumatized, peri-operative and critically ill patients). 7,8 Prospective clinical trials (summa- rized in 9 ) currently underway may shed light on this delicate issue, though results in very low birthweight infants have shown no effect of older RBC transfusions on clinical out- comes. 10 From a biochemical standpoint, storage lesions are only partly reversible and might affect RBC viability and functionality on transfusion. They might, therefore, at least the- oretically, affect the safety and effectiveness of the transfusion therapy with older units. 4-6 This paper will attempt to review the major aspects of RBC aging in vivo and in vitro, while focusing on recent findings with novel Transfusion medicine The study of in vivo and in vitro (storage conditions) aging of red blood cells has recently taken advantage of the introduction of mass spectrometry-based “-omics” disciplines, such as proteomics, metabolomics and lipidomics. In vivo and in vitro aging are characterized by shared features, including altered cation homeostasis, alteration of metabolic fluxes via decreased enzymatic activity and progressive depletion of high energy phosphates, increased susceptibility to oxidative stress, which in turn promotes oxidative lesions to proteins (carbonylation, fragmentation, hemoglobin glycation) and lipids (peroxidation), morphological changes (membrane blebbing, vesiculation). Most of these mechanisms closely resem- ble apoptosis-like phenomena. On the other hand, the closed system of blood bank storage in plastic bags and additive solutions results in particular in vitro alterations to red blood cells, such as hypothermically-depressed metab- olism, the exacerbation of oxidative stress-related phenomena, the progressive leakage of DEHP- plasticizers, the accumulation of microvesicles shed from red blood cells in the supernatant. These phenomena underlie the difficulties related to the extension of the shelf-life of red blood cell con- centrates in vitro from the currently allowed threshold (42 days) up to the actual life-span of red blood cells in vivo (120 days). Meanwhile, retrospective clinical and basic science evidence suggests that red blood cells stored longer than 14 days might not be as safe and effective as fresh ones. Learning goals At the conclusion of this activity, the participant should understand that: - mass spectrometry-based “-omics” (such as proteomics and metabolomics) strategies have con- tributed to recent developments in this field of research; - ageing of red blood cells in vivo and in vitro promotes the accumulation of reversible and irre- versible lesions; - in vitro storage of red blood cells (closed plastic bag system, hypothermia, additive solutions) exac- erbates oxidative stress and accelerates aging; - storage lesions accumulating in vitro soon after 14 days of storage are only partly reversible. A B S T R A C T