Extracellular vesicles (EVs) play central physiological and pathophysiological roles in intercellular communication. Biomarker studies addressing disorders such as cardiovascular diseases often focus on circulating microRNAs (miRNAs) and may, depending on the type of disease and clinic routine, utilise patient specimens sampled from arterial or venous blood vessels. Thus, it is essential to test whether circulating miRNA profiles depend on the respective sampling site. We assessed potential differences in arterial and venous cell-free miRNA profiles in a cohort of 20 patients scheduled for cardiac surgery. Prior to surgery, blood was simultaneously sampled from the radial artery and the internal jugular vein. After precipitating crude EVs, we performed small RNA Sequencing, which failed to detect significantly regulated miRNAs using stringent filtering criteria for differential expression analysis. Filtering with less strict criteria, we detected four miRNAs slightly upregulated in arterial samples, one of which could be validated by reverse transcription real-time PCR. The applicability of these findings to purified arterial and venous EVs was subsequently tested in a subset of the initial study population. While an additional clean-up step using size-exclusion chromatography seemed to reduce overall miRNA yield compared to crude EV samples, no miRNAs with differential arteriovenous expression were detected. Unsupervised clustering approaches were unable to correctly classify samples drawn from arteries or veins based on miRNAs in either crude or purified preparations. Particle characterisation of crude preparations as well as characterisation of EV markers in purified EVs resulted in highly similar characteristics for arterial and venous samples. With the exception of specific pathologies (e.g. severe pulmonary disorders), arterial versus venous blood sampling should therefore not represent a likely confounder when studying differentially expressed circulating miRNAs. The use of either arterial or venous serum EV samples should result in highly similar data on miRNA expression profiles for the majority of biomarker studies.

Abbreviations ACE inhibitors: Angiotensin-converting-enzyme inhibitors; ApoA1: Apolipoprotein A1; CNX: Calnexin; Cv: Coefficient of variation; cDNA: Complementary DNA; CABG: Coronary artery bypass graft; DGE: Differential gene expression; DPBS: Dulbecco’s Phosphate Buffered Saline; EVs: Extracellular vesicles; log2FC: Log2 fold change; baseMean: Mean miRNA expression; miRNA: MicroRNA; NTA: Nanoparticle Tracking Analysis; NGS: Next-Generation Sequencing; RT-qPCR: Reverse transcription quantitative real-time PCR; rRNA: Ribosomal RNA; RT: Room temperature; SEC: Size-exclusion chromatography; snoRNA: Small nucleolar RNA; snRNA: Small nuclear RNA; small RNA-Seq: Small RNA Sequencing; SD: Standard deviation; tRNA: Transfer RNA; TEM: Transmission electron microscopy; UA: Uranyl acetate.

细胞外囊泡（EVs）在细胞间通讯中发挥重要的生理和病理生理作用。针对诸如心血管疾病等疾病的生物标志物研究通常集中在循环微RNA（miRNA）上，并且可能根据疾病的类型和临床常规，利用从动脉或静脉血管采样的患者标本。因此，必须测试循环的miRNA谱是否取决于相应的采样位点。我们评估了计划进行心脏手术的20名患者的队列中无动脉和静脉无细胞miRNA谱的潜在差异。手术前，同时从the动脉和颈内静脉取血。在沉淀出粗制电动汽车后，我们进行了小分子RNA测序，使用严格的过滤标准进行差异表达分析无法检测到显着调节的miRNA。用不太严格的标准过滤，我们检测到了在动脉样品中略微上调的四个miRNA，其中之一可以通过逆转录实时PCR进行验证。随后在一部分初始研究人群中测试了这些发现对纯化的动脉和静脉电动汽车的适用性。尽管与粗制EV样品相比，使用尺寸排阻色谱法进行的额外清理步骤似乎降低了总体miRNA产量，但未检测到动静脉表达差异的miRNA。无监督的聚类方法无法基于粗制或纯化制剂中基于miRNA的从动脉或静脉抽取的样本进行正确分类。粗制品的颗粒表征以及纯化的EV中的EV标志物表征导致了动脉和静脉样品的高度相似。因此，在研究差异表达的循环miRNA时，除了特定的病理（例如严重的肺部疾病）外，动脉血与静脉血样本不应构成混淆。对于大多数生物标志物研究，使用动脉或静脉血清EV样品均应导致miRNA表达谱上的数据高度相似。因此，在研究差异表达的循环miRNA时，动脉血与静脉血样本不应代表可能的混淆。对于大多数生物标志物研究，使用动脉或静脉血清EV样品均应导致miRNA表达谱上的数据高度相似。因此，在研究差异表达的循环miRNA时，动脉血与静脉血样本不应代表可能的混淆。对于大多数生物标志物研究，使用动脉或静脉血清EV样品均应导致miRNA表达谱上的数据高度相似。

缩写ACE抑制剂：血管紧张素转换酶抑制剂；ApoA1：载脂蛋白A1；CNX：钙调蛋白；Cv：变异系数；cDNA：互补DNA；CABG：冠状动脉搭桥术；DGE：差异基因表达；DPBS：Dulbecco磷酸盐缓冲盐水；电动汽车：细胞外囊泡；log2FC：Log2倍数更改；baseMean：平均miRNA表达；miRNA：MicroRNA；NTA：纳米颗粒跟踪分析；NGS：下一代测序；RT-qPCR：反转录实时定量PCR；rRNA：核糖体RNA；RT：室温；SEC：体积排阻色谱法；snoRNA：小核仁RNA；snRNA：小核RNA；small RNA-Seq：小RNA测序；SD：标准偏差；tRNA：转移RNA；TEM：透射电子显微镜；UA：乙酸铀酰。