Sources to variability in circulating human miRNA signatures

An increasing number of studies propose circulating microRNAs (miRNAs) as biomarkers for a large number of human diseases including cancer, cardiovascular diseases, neurologic pathologies and others. To further validate miRNA as biomarkers it is indispensable to understand the variability of circulating miRNAs in healthy individuals. We determined the longitudinal miRNomes of 90 serum samples from the Janus Serum Bank in Norway, which have been stored between 23 and 40 y at -25 °Celsius. We profiled 3 serum samples with microarrays for 30 individuals, each. For each individual the samples were collected with a time interval of approximately 5 y. This design allowed insights into inter-individual variability, age dependent miRNA variability and the impact of storage length and pre-processing. A significant proportion of the miRNome was affected by the age of the blood donor and a not negligible, albeit small, part of the miRNome by the storage time. A substantial part of miRNAs was differentially abundant between individuals, independent of the time when samples were collected. Stepwise filtering of the 529 miRNAs that were detected in the serum samples showed 168 miRNAs with differential abundance depending on the time point analyzed, 56 miRNAs differentially abundant between individuals, and 169 miRNAs with an abundance depending on the sampling procedure. While these groups of miRNAs contain generally interesting and biologically important miRNAs, the remaining 135 miRNAs constitute very promising biomarker candidates as they show an overall low variability between healthy individuals, a likewise overall low variability across a longer life span, and a high independence of the sampling process and the storage length.

越来越多的研究提出，循环微RNA（circulating microRNAs，miRNAs）可作为包括癌症、心血管疾病、神经系统疾病在内的多种人类疾病的生物标志物。若要进一步验证miRNAs作为生物标志物的价值，明确健康个体体内循环miRNAs的变异情况必不可少。我们对来自挪威雅努斯血清库（Janus Serum Bank）的90份血清样本开展了纵向微RNA组分析，这些样本在-25℃条件下已保存23至40年。我们针对30名受试者，每人利用微阵列技术对3份血清样本进行表达谱分析，每名受试者的样本采集间隔均约为5年。该实验设计可用于探究个体间表达差异、与年龄相关的miRNAs表达变异，以及样本保存时长与前处理流程的影响。微RNA组中有相当大的比例受献血者年龄的影响，另有一小部分比例（虽占比不高但不容忽视）受样本保存时长的影响。相当一部分miRNAs的表达丰度在个体间存在显著差异，且与样本采集时间无关。对血清样本中检出的529种miRNAs进行逐步筛选后，得到168种表达丰度随分析时间点变化的miRNAs、56种个体间表达丰度存在差异的miRNAs，以及169种表达丰度受采样流程影响的miRNAs。尽管上述三类miRNAs中均包含具有研究价值与生物学重要性的分子，但剩余的135种miRNAs则是极具前景的生物标志物候选分子——它们在健康个体间整体变异程度较低，在更长的生命周期内整体变异程度同样偏低，且几乎不受采样流程与样本保存时长的影响。