Stored platelets develop new cell bodies and increase in number. (A-B) Ex vivo aged (1 or 4 days) platelets were resuspended in M199 medium and immediately fixed (Baseline) or cultured in suspension for 6 hours. (A) The panels display a representative example of one study where the platelets were stained for actin. Scale bars represent 10 μm. (B) The bar graph indicates the number of ex vivo–aged platelets with at least 2 cell bodies per microliter (mean ± SEM; n = 4). *P < .05, cultured vs baseline. (C) Ex vivo–aged platelets (day 4) were resuspended in culture medium for 6 hours in the presence (far right panels) or absence of thrombin. From left to right in the top row, the top row panels identify αIIbβ3, P-selectin, β-tubulin, control IgG, respiring mitochondria (Mitotracker), or sialic acids (WGA). Corresponding transmission images are shown in the bottom row. Scale bars represent 5 μm. This figure is representative of 3 independent experiments. (D) Platelets were stored under standard blood bank conditions, and platelet counts as well as mean platelet volumes (MPV) were determined. The left graph shows the platelet count before (day 0) and after (day 5) storage (mean ± SEM; n = 10). The right panel displays the MPV obtained from platelets used for the counting studies. *P < .05, day 0 vs day 5, for both panels.
