Institute for Systems Biology, Seattle, WA.
Program in Development and Fetal Health, Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Ontario, Canada; Department of Obstetrics and Gynecology, University of Toronto, Toronto, Ontario, Canada.
Am J Obstet Gynecol. 2018 Mar;218(3):345.e1-345.e30. doi: 10.1016/j.ajog.2017.12.234. Epub 2018 Jan 2.
Preterm birth is the leading cause of newborn death worldwide, and is associated with significant cognitive and physiological challenges in later life. There is a pressing need to define the mechanisms that initiate spontaneous preterm labor, and for development of novel clinical biomarkers to identify high-risk pregnancies. Most preterm birth studies utilize fetal tissues, and there is limited understanding of the transcriptional changes that occur in mothers undergoing spontaneous preterm labor. Earlier work revealed that a specific population of maternal peripheral leukocytes (macrophages/monocytes) play an active role in the initiation of labor. Thus, we hypothesized that there are dynamic gene expression changes in maternal blood leukocytes during preterm labor.
Using next-generation sequencing we aim to characterize the transcriptome in whole blood leukocytes and peripheral monocytes of women undergoing spontaneous preterm labor compared to healthy pregnant women who subsequently delivered at full term.
RNA sequencing was performed in both whole blood and peripheral monocytes from women who underwent preterm labor (24-34 weeks of gestation, N = 20) matched for gestational age to healthy pregnant controls (N = 30). All participants were a part of the Ontario Birth Study cohort (Toronto, Ontario, Canada).
We identified significant differences in expression of 262 genes in peripheral monocytes and 184 genes in whole blood of women who were in active spontaneous preterm labor compared to pregnant women of the same gestational age not undergoing labor, with 43 of these genes differentially expressed in both whole blood and peripheral monocytes. ADAMTS2 expression was significantly increased in women actively undergoing spontaneous preterm labor, which we validated through digital droplet reverse transcriptase polymerase chain reaction. Intriguingly, we have also identified a number of gene sets including signaling by stem cell factor-KIT, nucleotide metabolism, and trans-Golgi network vesicle budding, which exhibited changes in relative gene expression that was predictive of preterm labor status in both maternal whole blood and peripheral monocytes.
This study is the first to investigate changes in both whole blood leukocytes and peripheral monocytes of women actively undergoing spontaneous preterm labor through robust transcript measurements from RNA sequencing. Our unique study design overcame confounding based on gestational age by collecting blood samples from women matched by gestational age, allowing us to study transcriptomic changes directly related to the active preterm parturition. We performed RNA profiling using whole genome sequencing, which is highly sensitive and allowed us to identify subtle changes in specific genes. ADAMTS2 expression emerged as a marker of prematurity within peripheral blood leukocytes, an accessible tissue that plays a functional role in signaling during the onset of labor. We identified changes in relative gene expression in a number of gene sets related to signaling in monocytes and whole blood of women undergoing spontaneous preterm labor compared to controls. These genes and pathways may help identify potential targets for the development of novel drugs for preterm birth prevention.
早产是全球新生儿死亡的主要原因，与后期生活中的认知和生理挑战密切相关。迫切需要定义引发自发性早产的机制，并开发新的临床生物标志物来识别高危妊娠。大多数早产研究都使用胎儿组织，对母亲在自发性早产过程中发生的转录变化知之甚少。早期的研究表明，特定的母体外周白细胞（巨噬细胞/单核细胞）群体在分娩开始时发挥积极作用。因此，我们假设在自发性早产期间，母体血液白细胞中存在动态基因表达变化。
我们使用下一代测序技术，旨在描述与在足月时分娩的健康孕妇相比，在自发性早产（24-34 孕周）期间接受治疗的女性的全血白细胞和外周单核细胞中的转录组。
对在安大略省出生研究队列（多伦多，安大略省，加拿大）中接受自发性早产（n=20）的女性的全血和外周单核细胞进行 RNA 测序，并按孕龄与健康孕妇（n=30）相匹配。
与未分娩的同一孕龄孕妇相比，正在积极接受自发性早产的女性的外周单核细胞中表达的 262 个基因和全血中表达的 184 个基因存在显著差异，其中 43 个基因在全血和外周单核细胞中差异表达。ADAMTS2 的表达在积极接受自发性早产的女性中显著增加，我们通过数字液滴逆转录酶聚合酶链反应对此进行了验证。有趣的是，我们还确定了一些基因集，包括干细胞因子-KIT 信号、核苷酸代谢和高尔基网络囊泡出芽，它们在相对基因表达方面的变化可预测母体全血和外周单核细胞中的早产状态。
这项研究首次通过来自 RNA 测序的强大转录测量，研究了正在积极接受自发性早产的女性的全血白细胞和外周单核细胞中的变化。我们独特的研究设计通过收集与孕龄匹配的女性的血液样本，克服了基于孕龄的混杂因素，使我们能够研究与主动早产分娩直接相关的转录组变化。我们使用全基因组测序进行 RNA 分析，该方法具有高度敏感性，并允许我们识别特定基因的细微变化。ADAMTS2 的表达在周围血白细胞中作为早产的标志物出现，白细胞是一种具有功能作用的可及组织，在分娩开始时参与信号传递。与对照组相比，我们在接受自发性早产的女性的外周单核细胞和全血中发现了一些与信号相关的基因集的相对基因表达变化。这些基因和途径可能有助于确定预防早产的新型药物的潜在靶点。
