The Methodist Hospital Research Institute and The Methodist DeBakey Heart and Vascular Center, Houston, TX 77030, USA.
J Thromb Thrombolysis. 2010 Oct;30(3):251-62. doi: 10.1007/s11239-010-0489-x.
Circulating platelets are heterogeneous in size and structure. Whether this translates into differences in platelet function and efficacy of antiplatelet therapy is unclear. Hence, we decided to investigate the activation patterns among different platelet populations differentiated by size, and to compare the inhibitory effects of aspirin in these populations. Circulating platelets from 9 healthy volunteers were separated by size and stratified into the largest and smallest quintiles. Platelets were stimulated with 75 μM arachidonic acid (AA), 10 μM ADP or 25 μM TRAP. Alpha-granule protein secretion and expression (P-selectin, VWF, fibrinogen), surface-protein activation (activated integrin αIIbβ3) were assessed. Platelet thromboxane B(2) (TxB(2)) synthesis following AA stimulation was measured in vitro before and after incubation with 265 μM aspirin. Reticulated (juvenile) platelets were assessed using thiazole orange staining. A greater number of large platelets in the largest quintile were reticulated compared with the smallest quintile (6.1 ± 2.8% vs. 1.2 ± 1.5% respectively, p < 0.001). Larger platelets also synthesized more TxB(2) than small platelets both before (1348 ± 276 pg/mL vs. 1023 ± 214 pg/mL, respectively, p = 0.01) and after aspirin (1029 ± 190 pg/mL vs. 851 ± 159 pg/mL, respectively, p = 0.03). After stimulation with each agonist, a greater proportion of large platelets bound fibrinogen, VWF, P-selectin and activated integrin αIIbβ3 than small platelets both in the presence and in the absence of in vitro aspirin. In an in vitro setting, large platelets appear to be more active than small platelets and continue to be more active even after in vitro aspirin. Platelets exhibit heterogeneity in size and structure. Whether this translates into platelet function and efficacy of antiplatelet therapy is unclear. We evaluated platelet functional properties and the effects of aspirin on separated platelet subpopulations in an in vitro setting. Platelets were sorted into the largest and smallest size quintiles using flow cytometry forward scatter. Alpha-granule protein release, dense granule content, surface protein activation and thromboxane synthesis were significantly greater in large platelets compared with small platelets, before and after stimulation with arachidonic acid, ADP and TRAP. Even after incubation with aspirin, large platelets continued to be more active than small platelets. In conclusion, large platelets are more active than small platelets and aspirin fails to eliminate these differential activation properties.
循环血小板在大小和结构上存在异质性。这种差异是否会转化为血小板功能的差异以及抗血小板治疗的效果尚不清楚。因此，我们决定研究通过大小区分的不同血小板群体的激活模式，并比较阿司匹林在这些群体中的抑制作用。
我们从 9 名健康志愿者中分离出循环血小板，并按大小分为最大和最小的五分之一。用 75μM 花生四烯酸 (AA)、10μM ADP 或 25μM TRAP 刺激血小板。评估α-颗粒蛋白分泌和表达（P-选择素、VWF、纤维蛋白原）、表面蛋白激活（激活的整合素 αIIbβ3）。在体外用 265μM 阿司匹林孵育前后测量 AA 刺激后血小板血栓素 B2 (TxB2) 的合成。使用噻唑橙染色评估网织（幼稚）血小板。最大五分之一的大血小板比最小五分之一的血小板网织化程度更高（分别为 6.1±2.8%和 1.2±1.5%，p<0.001）。较大的血小板在未用阿司匹林和用阿司匹林处理后合成的 TxB2 均多于小血小板（分别为 1348±276 pg/mL 和 1023±214 pg/mL，p=0.01 和 1029±190 pg/mL 和 851±159 pg/mL，p=0.03）。在用每种激动剂刺激后，与小血小板相比，大血小板在有和没有体外阿司匹林的情况下结合纤维蛋白原、VWF、P-选择素和激活的整合素 αIIbβ3 的比例均更高。
在体外环境中，大血小板比小血小板更活跃，即使在体外阿司匹林处理后，它们仍然更活跃。血小板在大小和结构上表现出异质性。这种差异是否会转化为血小板功能和抗血小板治疗的效果尚不清楚。我们在体外环境中评估了分离的血小板亚群的血小板功能特性和阿司匹林的作用。
我们使用流式细胞术前向散射将血小板分为最大和最小的五个大小五分位。与小血小板相比，大血小板在受到 AA、ADP 和 TRAP 刺激前后，α-颗粒蛋白释放、致密颗粒含量、表面蛋白激活和血栓素合成均显著增加。即使在与阿司匹林孵育后，大血小板仍比小血小板更活跃。总之，大血小板比小血小板更活跃，阿司匹林未能消除这些差异激活特性。
