Keller Andreas, Meese Eckart
Chair for Clinical Bioinformatics, Saarland University, University Hospital, Saarbrücken, Germany.
Institute of Human Genetics, Saarland University, University Hospital, Homburg, Germany.
Wiley Interdiscip Rev RNA. 2016 Mar-Apr;7(2):148-56. doi: 10.1002/wrna.1320. Epub 2015 Dec 15.
MicroRNAs have been discussed as non- or minimal invasive biomarkers with a remarkable extracellular stability. Despite a multitude of studies in basic research, there are only few independent validation studies on blood-born miRNAs as disease markers. Toward clinical applications numerous obstacles still need to be overcome. They are of technical origin but also fundamentally associated with the source and the nature of miRNAs. Here, we emphasize on potential confounding factors, the nature and the source of miRNAs. We recently showed that age and gender could influence the pattern of circulating miRNAs. On the cellular level, the miRNA pattern differs between plasma and serum preparations. On the molecular level, one has to differentiate between extracellular miRNAs that are encapsulated in microvesicles or bound to proteins or high-density lipoproteins. Using whole blood as source for miRNAs helps to minimize miRNA expression changes due to environmental influences and allows attributing miRNA changes to their cells of origin like B-cells and T-cells. Moreover, unambiguous annotation and differentiation from other noncoding RNAs can be challenging. Even not all miRNAs deposited in miRBase do necessarily represent true miRNAs, just a fraction of miRNAs in the reference database have been experimentally validated by Northern blotting. Functional evidence for a true miRNA should be obtained by cloning the precursor miRNA and by subsequent detection of the processed mature form in host cells. Surprisingly, attempts to finally confirm a true miRNA are frequently postponed until evidence has been established for a likely value as biomarker.
微小RNA（miRNA）已被视为具有显著细胞外稳定性的非侵入性或微创生物标志物。尽管基础研究中有大量相关研究，但关于血液中miRNA作为疾病标志物的独立验证研究却很少。在临床应用方面，仍有许多障碍需要克服。这些障碍既有技术层面的原因，也与miRNA的来源和性质密切相关。在此，我们着重探讨潜在的混杂因素、miRNA的性质和来源。我们最近发现年龄和性别会影响循环miRNA的模式。在细胞水平上，血浆和血清制剂中的miRNA模式存在差异。在分子水平上，必须区分包裹在微泡中、与蛋白质或高密度脂蛋白结合的细胞外miRNA。以全血作为miRNA的来源有助于将环境影响导致的miRNA表达变化降至最低，并能够将miRNA的变化归因于其起源细胞，如B细胞和T细胞。此外，与其他非编码RNA进行明确的注释和区分可能具有挑战性。甚至并非所有存于miRBase中的miRNA都必然代表真正的miRNA，参考数据库中只有一小部分miRNA已通过Northern印迹法进行了实验验证。真正miRNA的功能证据应通过克隆前体miRNA并随后在宿主细胞中检测加工后的成熟形式来获得。令人惊讶的是，最终确认真正miRNA的尝试常常被推迟，直到有证据表明其作为生物标志物可能具有价值。
