The effects of residual platelets in plasma on plasminogen activator inhibitor-1 and plasminogen activator inhibitor-1-related assays

Due to controversial evidence in the literature pertaining to the activity of plasminogen activator inhibitor-1 in platelets, we examined the effects of residual platelets present in plasma (a potential pre-analytical variable) on various plasminogen activator inhibitor-1 and plasminogen activator inhibitor-1-related assays. Blood samples were collected from 151 individuals and centrifuged at 352 and 1500 g to obtain plasma with varying numbers of platelet. In a follow-up study, blood samples were collected from an additional 23 individuals, from whom platelet-poor (2000 g), platelet-containing (352 g) and platelet-rich plasma (200 g) were prepared and analysed as fresh-frozen and after five defrost-refreeze cycles (to determine the contribution of in vitro platelet degradation). Plasminogen activator inhibitor-1 activity, plasminogen activator inhibitor-1 antigen, tissue plasminogen activator/plasminogen activator inhibitor-1 complex, plasma clot lysis time, β-thromboglobulin and plasma platelet count were analysed. Platelet α-granule release (plasma β-thromboglobulin) showed a significant association with plasminogen activator inhibitor-1 antigen levels but weak associations with plasminogen activator inhibitor-1 activity and a functional marker of fibrinolysis, clot lysis time. Upon dividing the study population into quartiles based on β-thromboglobulin levels, plasminogen activator inhibitor-1 antigen increased significantly across the quartiles while plasminogen activator inhibitor-1 activity and clot lysis time tended to increase in the 4th quartile only. In the follow-up study, plasma plasminogen activator inhibitor-1 antigen was also significantly influenced by platelet count in a concentration-dependent manner. Plasma plasminogen activator inhibitor-1 antigen levels increased further after complete platelet degradation. Residual platelets in plasma significantly influence plasma plasminogen activator inhibitor-1 antigen levels mainly through release of latent plasminogen activator inhibitor-1 with limited effects on plasminogen activator inhibitor-1 activity, tissue plasminogen activator/plasminogen activator inhibitor-1 complex or plasma clot lysis time. Platelets may however also have functional effects on plasma fibrinolytic potential in the presence of high platelet counts, such as in platelet-rich plasma.

鉴于当前文献中关于血小板内纤溶酶原激活物抑制剂-1（plasminogen activator inhibitor-1）的活性存在争议性证据，本研究探讨了血浆中残留血小板（一种潜在的分析前变量）对多种纤溶酶原激活物抑制剂-1及纤溶酶原激活物抑制剂-1相关检测的影响。本研究共收集151名受试者的血液样本，分别以352 g和1500 g离心制备得到血小板数量各异的血浆。在后续研究中，额外招募23名受试者采集血液样本，分别制备乏血小板血浆（platelet-poor plasma，2000 g离心）、含血小板血浆（352 g离心）以及富血小板血浆（platelet-rich plasma，200 g离心），并分别以新鲜冻存状态及经过5次冻融循环（defrost-refreeze cycles，用于探究体外血小板降解的影响）进行检测分析。本次检测的指标包括纤溶酶原激活物抑制剂-1活性、纤溶酶原激活物抑制剂-1抗原水平、组织型纤溶酶原激活物（tissue plasminogen activator）/纤溶酶原激活物抑制剂-1复合物、血浆血凝块溶解时间、β血小板球蛋白（β-thromboglobulin）以及血浆血小板计数。研究发现，血小板α颗粒（α-granule）释放产物（血浆β血小板球蛋白）与纤溶酶原激活物抑制剂-1抗原水平存在显著相关性，但与纤溶酶原激活物抑制剂-1活性及纤维蛋白溶解（fibrinolysis）功能标志物血凝块溶解时间仅存在较弱关联。以β血小板球蛋白水平对研究人群进行四分位分组后，纤溶酶原激活物抑制剂-1抗原水平随四分位分组显著升高，而纤溶酶原激活物抑制剂-1活性及血凝块溶解时间仅在第4四分位组呈现升高趋势。在后续研究中，血浆纤溶酶原激活物抑制剂-1抗原水平同样受血小板计数的显著影响，且呈现浓度依赖性。当血小板完全降解后，血浆纤溶酶原激活物抑制剂-1抗原水平进一步升高。血浆中残留血小板主要通过释放潜伏型纤溶酶原激活物抑制剂-1，对血浆纤溶酶原激活物抑制剂-1抗原水平产生显著影响，而对纤溶酶原激活物抑制剂-1活性、组织型纤溶酶原激活物/纤溶酶原激活物抑制剂-1复合物或血浆血凝块溶解时间的影响有限。不过，当血小板计数较高时（如富血小板血浆场景），血小板也可能对血浆纤维蛋白溶解潜能产生功能性影响。