Spring is in the air: seasonal profiles indicate vernal change of miRNA activity

The envisioned application of miRNAs as diagnostic or prognostic biomarkers calls for an in-depth understanding of their distribution and variability in different physiological states. While effects with respect to ethnic origin, age, or gender are known, the inter-individual variability of miRNAs across the four seasons remained largely hidden. We sequentially profiled the complete repertoire of blood-borne miRNAs for 25 physiologically normal individuals in spring, summer, fall, and winter (altogether 95 samples) and validated the results on 292 individuals (919 samples collected with the Mitra home sampling device) by RT-qPCR. Principal variance component analysis suggests that the largest variability observed in miRNA expression is due to individual variability and the individuals’ gender. But the results also highlight a deviation of miRNA activity in samples collected during spring time. Following adjustment for multiple testing, remarkable differences are observed between spring and fall (77 miRNAs). The two most dys-regulated miRNAs were miR-181c-5p and miR-106b-5p (adjusted p-value of 0.007). Other significant miRNAs include miR-140-3p, miR-21-3p, and let-7c-5p. The dys-regulation was validated by RT-qPCR. Systems biology analysis further provides strong evidence for the immunological origin of the signals: dys-regulated miRNAs are enriched in CD56 cells and belong to various signalling and immune-system-related pathways. Our data suggest that besides known confounding factors such as age and sex, also the season in which a test is conducted might have a considerable influence on the expression of blood-borne miRNAs and subsequently might interfere with diagnosis based on such signatures.

将微小核糖核酸（microRNAs, miRNAs）用作诊断或预后生物标志物的预期应用场景，要求学界对其在不同生理状态下的分布与变异特征展开深入解析。尽管种族、年龄与性别对miRNAs表达的影响已为学界所证实，但四季更迭下miRNAs的个体间变异仍基本未被揭示。我们按季节顺序对25名生理状态正常的个体进行了血液源性miRNAs全表达谱分析，共计采集95份样本；并通过实时荧光定量聚合酶链式反应（RT-qPCR），利用Mitra家庭采样装置采集的292名个体的919份样本对上述结果进行了验证。主方差成分分析（Principal variance component analysis）结果显示，miRNAs表达水平的最大变异源于个体差异与个体性别因素。但研究结果同时表明，春季采集样本的miRNAs活性存在显著异常偏移。经多重检验校正后，春季与秋季样本间的miRNAs表达差异尤为显著，共涉及77种miRNAs。表达失调程度最高的两种miRNAs为miR-181c-5p与miR-106b-5p（校正后p值为0.007）；其他具有统计学意义的miRNAs还包括miR-140-3p、miR-21-3p及let-7c-5p。上述表达失调现象已通过RT-qPCR得到验证。系统生物学分析进一步为该信号的免疫起源提供了有力证据：失调的miRNAs在CD56细胞中富集，且参与多种信号通路及免疫系统相关通路。我们的研究数据表明，除年龄、性别等已知混杂因素外，样本采集季节也可能对血液源性miRNAs的表达产生显著影响，进而干扰基于此类分子标志物的诊断流程。