Background Extracellular RNAs (exRNAs) in biofluids are amenable to quantitative analysis and proposed as noninvasive biomarkers for monitoring organ function. Cell-lineage-specific microRNAs (miRNAs) are present in plasma as soluble ribonucleoproteins or enclosed in exRNA carriers and transported through the vasculature. However, more extensive studies of healthy individuals are needed to gain insights into the variability of plasma miRNA abundance and composition. Methods The exRNA composition of platelet-depleted plasma collected twice from 236 healthy individuals was characterized by small RNA sequencing. Plasma of pregnant women featuring dramatically increased placental miRNAs and samples from subject P12 with noticeably increased epithelial- and neuroendocrine-origin miRNAs were included for comparison. The miRNA content of 10 000g and 100 000g pellet fractions of plasma generated by ultracentrifugation was also determined. Data analysis methods included Pearson correlation, differential gene expression, and unsupervised clustering. Results The abundance changes for more variable miRNAs in plasma of normal individuals correlated between coexpressed cell-lineage-specific miRNAs of the liver, neuroendocrine organs, epithelial cells, and muscle. ExRNA of pellet fractions contained <2% of total plasma miRNA with modest enrichment of lineage-specific and variable miRNAs compared to supernatant. The abundance fold changes of miRNAs observed in pregnancy and P12 compared to normal exceeded interquartile variability of healthy individuals. The neuroendocrine miRNA signature of P12 persisted for more than 4 years and was absent in other individuals. Conclusions This study defines the framework and effect size for screening of extensive plasma collections for miRNA phenotypes and biomarker discovery.

中文翻译：

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健康个体、孕妇和具有稳定改变的神经内分泌表型的个体的血浆 microRNA 个体间变异性

背景 生物体液中的细胞外 RNA (exRNA) 适合进行定量分析，并被提议作为监测器官功能的非侵入性生物标志物。细胞谱系特异性 microRNA (miRNA) 作为可溶性核糖核蛋白存在于血浆中，或封装在 exRNA 载体中并通过脉管系统运输。然而，需要对健康个体进行更广泛的研究，以深入了解血浆 miRNA 丰度和组成的可变性。方法 对 236 名健康个体两次采集的去血小板血浆的 exRNA 组成进行小 RNA 测序。包括胎盘 miRNA 显着增加的孕妇血浆和上皮和神经内分泌来源 miRNA 显着增加的受试者 P12 的样品用于比较。还测定了通过超速离心产生的血浆的 10 000g 和 100 000g 颗粒部分的 miRNA 含量。数据分析方法包括皮尔逊相关、差异基因表达和无监督聚类。结果 正常个体血浆中更多可变 miRNA 的丰度变化与肝脏、神经内分泌器官、上皮细胞和肌肉的共表达的细胞谱系特异性 miRNA 相关。与上清液相比，沉淀部分的 ExRNA 含有 <2% 的总血浆 miRNA，具有适度富集的谱系特异性和可变 miRNA。与正常相比，在怀孕和 P12 中观察到的 miRNA 的丰度倍数变化超过了健康个体的四分位间变异性。P12 的神经内分泌 miRNA 特征持续了 4 年以上，在其他个体中不存在。结论 本研究定义了筛选大量血浆样本的 miRNA 表型和生物标志物发现的框架和效应量。