Platelet storage: changes in cytosolic Ca2+ actin polymerization and shape

Abstract

Platelets gradually lose their disc shape during storage. The authors studied simultaneous changes in platelet cytosolic Ca2+ (Cai) and the polymerization state of actin as related to the shape. Platelet concentrates were stored under blood bank conditions for up to 10 days. Aliquots were removed and analyzed as follows: platelet Cai and increments in Cai induced by adenosine diphosphate (ADP) were determined by fluorescence of fura-2-loaded cells; loss of disc shape was determined by differences in light scattering intensity induced by stirring; and the ratio of globular and total actin (G/T) of platelets in plasma was determined by a modification of the DNase inhibition assay. Globular actin was found to be 86 +/- 3% of total actin in freshly drawn platelets suspended in plasma. The following changes occurred during storage: G/T in platelet concentrates increased from 63 +/- 5 (day 0) to 74 +/- 2% in the first 24 hours then fell to 33 +/- 6% by day 10. The percent discoid platelets also increased from day 0 to day 1 then fell in the ensuing days. There was an initial drop in Cai from day 0 to day 1, after which Cai increased on days 3 and 6. Globular actin polymerization during storage closely correlated with the change in percent discs (r = 0.95). During 6 days of storage Cai was highly correlated with shape change (r = 0.97) and to a lesser extent (r = 0.87) with the ratio of globular actin. The authors conclude that actin polymerization, shape, and Ca2+ change in a related fashion during storage.

Decreased responsiveness and development of activation markers of PLTs stored in plasma

“…There is only limited literature on altered PLT activation in response to physiologic stimuli during storage of PLT concentrates. Some early reports, mostly studying PLTs that were conventionally prepared by pooling PRP, describe changes in basal [Ca 2+ ] i levels and usually transient reduction in agonist‐induced Ca 2+ mobilization during prolonged storage 32‐34 . Differences with the present results may well relate to changes in preparation and processing of the concentrates during the past two decades.…”

“…Differences with the present results may well relate to changes in preparation and processing of the concentrates during the past two decades. Thrombin binding to PLTs was also found to decrease during storage, 35 as well as ADP‐ and thrombin‐induced PLT aggregation, 28,36 perhaps because of alterations in cytoskeletal organization and protein tyrosine phosphorylation 33,37 . Together, these reports underscore the present evidence that a major effect of storage is decreased excitability per se of PLTs (owing to senescence?)…”

Decreasing phosphodiesterase 5A activity contributes to platelet cGMP accumulation during storage of apheresis‐derived platelet concentrates

“…Studies of apheresis‐derived PLT concentrates (APCs) revealed an accumulation of soluble P‐selectin, PLT factor 4, CD62P‐positive PLTs, and increasing intracellular Ca 2+ levels . Flow cytometric analysis of PLTs in stored APCs show decreased expression of surface glycoproteins GPIIb/IIIa and GPIb, accompanied by the loss of high‐affinity thrombin receptors on PLT surface .…”

Platelet storage solution improves the in vitro function of preserved platelet concentrate

“…Furthermore, a significant progressive decrease in haemostatic properties occurs, as evidenced by a decreased platelet aggregation response, decreased adenine nucleotide concentration, collection‐ or storage‐induced activation, loss of expression or affinity of surface receptors, activation of complement, and/or a change in the intracellular calcium concentration, leading to a cascade of events promoting platelet activation [6]. The majority of platelets undergo some degree of activation during procurement, processing or storage, leading to in vivo functional compromise [20–24,35].…”

“…Such lesions might be mediated by alterations in the biochemical or metabolic activity of the stored platelets, leading to an ultimate compromise in the in vitro function. For instance, irreversible changes in the shape of platelets, elevation of cytosolic calcium, assembly of filamentous actin, loss of activity of enzymes that play a critical role in signal‐transduction events, loss of or decrease in the number of available receptors, or loss of adenylate energy charge, are considered as storage‐induced lesions [19–24]. These lesions, singly or together, will be reflected in the viability and function of a platelet [5,25].…”