Differences between Platelets Derived from Neonatal Cord Blood and Adult Peripheral Blood Assessed by Mass Spectrometry

It has been proposed that differences may exist between umbilical cord blood (CB) platelets and adult peripheral blood (APB) platelets, including altered protein levels of the main platelet integrins. We have now compared the protein expression profiles of CB and APB platelets employing a label-free comparative proteomics approach. Aggregation studies showed that CB platelets effectively aggregate in the presence of thromboxane A2 analogue, collagen, and peptide agonists of the proteinase-activated receptors 1 and 4. In agreement with previous studies, higher concentrations of the agonists were required to initiate aggregation in the CB platelets. Mass spectrometry analysis revealed no significant difference in the expression levels of critical platelet receptors like glycoprotein (GP)­Ib, GPV, GPIX, and integrin αIIbβ3. This was confirmed using flow cytometry-based approaches. Gene ontology enrichment analysis revealed that elevated proteins in CB platelets were in particular enriched in proteins contributing to mitochondrial energy metabolism processes. The reduced proteins were enriched in proteins involved in, among others, platelet degranulation and activation. In conclusion, this study reveals that the CB and APB platelets are distinct. In particular, changes were observed for proteins that belong to metabolic and energy generation processes and not for the critical adhesive platelet integrins and glycoproteins.

已有研究提出，脐带血（umbilical cord blood, CB）血小板与成人外周血（adult peripheral blood, APB）血小板之间可能存在差异，包括主要血小板整合素的蛋白水平改变。本研究采用无标记比较蛋白质组学方法，对比了CB与APB血小板的蛋白表达谱。聚集实验结果显示，在血栓烷A2类似物、胶原以及蛋白酶活化受体1和4的肽类激动剂存在时，CB血小板可有效发生聚集。与既往研究结果一致，CB血小板启动聚集所需的激动剂浓度更高。质谱分析结果表明，关键血小板受体如糖蛋白（glycoprotein, GP）Ib、GPV、GPIX以及整合素αIIbβ3的表达水平无显著差异。该结论通过流式细胞术方法得到了验证。基因本体富集分析显示，CB血小板中表达上调的蛋白尤其富集于参与线粒体能量代谢过程的蛋白。表达下调的蛋白则富集于参与血小板脱颗粒与活化等过程的蛋白。综上，本研究表明CB与APB血小板存在显著差异，具体差异主要体现在参与代谢与能量生成过程的蛋白，而非关键的黏附性血小板整合素与糖蛋白。