Evaluation of the Impact-R for monitoring the platelet storage lesion.

The aim of this study was to evaluate the Impact-R test for measuring changes in platelet function in stored platelet concentrates. Platelet function was measured within samples (reconstituted with red cells) taken from apheresis concentrates (n = 20) and buffy coat concentrates (n = 20) stored for up to 7 days. The final mean platelet counts and haematocrits in apheresis concentrates were 319 x 10(9)/l and 56.2%, and in buffy coat concentrates they were 296 x 10(9)/l and 54.6%, respectively. The surface coverage (a measure of adhesion) decreased significantly during storage of PCs from 11.6 +/- 4 and 8.5 +/- 3.8% on day 1 to 7.4 +/- 3.4 and 5.9 +/- 3% on day 7 in apheresis and buffy coat concentrates, respectively. Buffy coat concentrates exhibited a significantly lower surface coverage than apheresis concentrates on day 1 of testing. The average size (a measure of aggregation) also decreased significantly during storage from 26.9 +/- 3.7 microm(2) and 24.1 +/- 3.1 microm(2) on day 1 to 21.8 +/- 3 microm(2) and 20.8 +/- 2.2 microm(2) on day 7 in apheresis and buffy coat concentrates, respectively. However, in contrast to the surface coverage, no significant difference in the average size between the two types of concentrate was observed. In conclusion, both platelet adhesion and aggregation measured by the Impact-R device decline significantly during the storage of platelet concentrates. The Impact-R is a simple device to perform rapid test which may be useful for the assessment of platelet function within platelet concentrates

Markers of platelet activation and apoptosis during storage of apheresis- and buffy coat-derived platelet concentrates for 7 days.

BACKGROUND: The different production methods for platelet concentrates (PCs) result in products with variable in vitro quality and in vivo viability. The aim of this study was to compare in vitro variables of PCs produced by apheresis (AP-PC) or the buffy coat (BC-PC) method by applying a number of new and established assays. STUDY DESIGN AND METHODS: Standard TRIMA Accel (Gambro BCT) AP-PCs (n = 20) and BC-PCs (n = 20) were stored in 100 percent plasma and changes in mitochondrial membrane potential (DeltaPsi(m)) were assessed using 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethlybenzimidazolcarbocyanine iodide (JC-1) dye on Days 1, 3, 5, and 7. The capacity of platelets (PLTs) for oxidative phosphorylation was also monitored by measuring oxygen consumption using a Clark-type electrode. PLT viability was measured using a new assay that utilizes the vital stains calcein-AM and FM4-64. Expression of phosphatidylserine (PS), CD42b, CD47, CD61, and CD62P was also assessed. RESULTS: Although the JC-1 ratio (FL2/FL1) decreased significantly in both preparations, the percentage of PLTs with depolarized DeltaPsi(m) increased significantly in BC-PCs but not in AP-PCs. However, no significant change was detected in the PLTs' ability to consume oxygen in both preparations. PLTs in BC-PCs also showed significantly lower GPIb, CD47, and CD61 expression than AP-PCs on Day 1. PLTs in both preparations, however, showed a similar increase in CD62P and PS expression during storage, without significant loss of viability. CONCLUSIONS: PLTs in AP-PCs and BC-PCs undergo different degrees of deterioration in mitochondrial integrity and thus may undergo different degrees of apoptosis. Interventions that maintain mitochondrial integrity may improve PLT viability in vitro

Measurement of phosphatidylserine exposure during storage of platelet concentrates using the novel probe lactadherin: a comparison study with annexin V.

BACKGROUND: Annexin V binding to platelets (PLTs) is considered the gold standard for monitoring phosphatidylserine (PS) exposure. However, recent comparison of annexin V with the new calcium-independent PS probe lactadherin revealed that annexin V requires a certain threshold of PS exposure (2%-8%) for binding to occur. The aim of this study was to compare annexin V and lactadherin labeling of PLTs in PLT concentrates (PCs). STUDY DESIGN AND METHODS: Optimal labeling conditions for lactadherin and annexin V were established and then compared in either resting or calcium ionophore (CI)-activated PLTs from normal whole blood. Furthermore, 40 PCs (20 apheresis-derived and 20 pooled buffy coat-derived) were stored under standard blood bank conditions and PLT activation was monitored by measuring PS exposure with annexin V and lactadherin along with CD42b, CD61, and CD62P by flow cytometry on Days 1, 3, 5, and 7. RESULTS: Lactadherin reported a higher exposure of PS than did annexin V in normal PLTs at submaximal doses of CI. PLTs from both types of concentrate, as expected, demonstrated evidence of increased activation during storage using annexin V, lactadherin, CD42b, or CD62P. However, a significantly higher percentage of PS-positive PLTs was found with lactadherin than annexin V. CONCLUSION: PS exposure on the surface of stored PLTs has been previously underestimated due to the wide use of annexin V. Lactadherin provides a truer reflection of the degree of PS exposure and offers a new calcium-independent approach to studying PLT activation and/or apoptosis