BACKGROUND The many manipulations and processes used in ART coincide with the timing of epigenetic reprogramming and imprinting during female gametogenesis and pre-implantation embryo development, leading to concerns that the actual ART could negatively affect epigenetic reprogramming and imprinting in gametes and early embryos. A growing body of literature suggests that ART may affect epigenetic marks, such as DNA methylation, in the fetus and placenta. Potentially, this may be responsible later in life for the increased risk of adverse outcomes associated with ART. Unfortunately, the conclusions are inconsistent and, despite the increasing usage of ART, its safety at the epigenetic level is still not established. OBJECTIVE AND RATIONALE To examine whether ART is associated with DNA methylation modifications and if these modifications persist throughout life, we provide an update on the current understanding of epigenetic reprogramming in human gametes and embryos, and then focus on the assessment of fetal and postnatal DNA methylation modifications that may remain until adulthood following the use of ART in humans. SEARCH METHODS We reviewed studies using targeted or epigenome-wide techniques to assess the DNA methylation patterns of the conceptus after ART compared with natural conceptions. A search for relevant studies was performed in the PubMed and EMBASE databases on 15 July 2021 with an extensive search equation. Studies on animals, gametes and embryos were subsequently excluded. After an in-depth review of full-text articles, studies on specific populations with imprinting disorders were removed and not further discussed. Before comprehensive analysis, the risk of bias of each included study was assessed with the Newcastle–Ottawa scale and quality of evidence was graded using the Grading of Recommendations, Assessment, Development and Evaluations criteria. OUTCOMES In total, 928 records were initially identified, and 51 were finally included in the systematic review. Given the variability in the genomic scale at which DNA methylation was measured in the different studies, they were separated into two categories: targeted DNA methylation or genome-wide DNA methylation study. The present systematic review has made it possible to assess a substantial number of children since more than 4000 DNA methylation profiles of ART concepti were compared to more than 7000 controls. There is evidence that ART conception is associated with aberrant DNA methylation in imprinted loci and other genes in various tissues. One isolated modification notably occur in the paternally expressed gene 1/mesoderm-specific transcript homologue (PEG1/MEST) region, and we cannot rule out other studied sequences owing to the heterogeneity of the evidence base. WIDER IMPLICATIONS Differences in DNA methylation after ART conceptions are modest, and the functional relevance in adult tissues is unknown. Functional effects in terms of gene expression as well as the roles of other epigenetic marks need to be further explored. Moreover, there is little overlap of findings obtained in targeted and genome-scale analyses owing to the lack of comparability of CpGs analyzed between both techniques. This issue also stems from small sample sizes and marked differences in methodology and cohort characteristics. Standardization of methodologies and large collaborative efforts are required to reduce the inconsistency of results and increase the robustness of findings. Finally, further studies are required to determine the contribution of parental infertility per se from the ART treatment.

中文翻译：

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人类生命周期内 ART 后的 DNA 甲基化谱：系统评价和荟萃分析

背景技术 ART 中使用的许多操作和过程与雌性配子发生和植入前胚胎发育过程中的表观遗传重编程和印记的时间相吻合，导致人们担心实际的 ART 可能会对配子和早期胚胎中的表观遗传重编程和印记产生负面影响。越来越多的文献表明，ART 可能会影响胎儿和胎盘中的表观遗传标记，例如 DNA 甲基化。潜在地，这可能会在以后的生活中增加与 ART 相关的不良后果的风险。不幸的是，结论并不一致，尽管 ART 的使用越来越多，但其在表观遗传水平上的安全性仍未确定。目的和理由 为了检验 ART 是否与 DNA 甲基化修饰相关，以及这些修饰是否会持续一生，我们提供了对人类配子和胚胎表观遗传重编程的最新理解，然后重点评估胎儿和出生后 DNA 甲基化在人类使用 ART 后可能会一直持续到成年的修饰。搜索方法 我们回顾了使用靶向或表观基因组技术评估 ART 后与自然受孕相比受孕的 DNA 甲基化模式的研究。2021 年 7 月 15 日，在 PubMed 和 EMBASE 数据库中进行了相关研究的搜索，并使用了广泛的搜索方程。随后排除了对动物、配子和胚胎的研究。在对全文文章进行深入审阅后，对患有印记障碍的特定人群的研究被删除，不再进一步讨论。在综合分析之前，使用纽卡斯尔-渥太华量表评估每项纳入研究的偏倚风险，并使用建议分级、评估、发展和评估标准对证据质量进行分级。结果 最初确定了 928 条记录，最终将 51 条记录纳入系统评价。鉴于在不同研究中测量 DNA 甲基化的基因组规模的可变性，它们被分为两类：靶向 DNA 甲基化或全基因组 DNA 甲基化研究。本系统评价使评估大量儿童成为可能，因为将 4000 多个 ART 概念的 DNA 甲基化谱与 7000 多个对照进行了比较。有证据表明，ART 受孕与印迹基因座和各种组织中其他基因的异常 DNA 甲基化有关。一个孤立的修饰显着发生在父系表达的基因 1/中胚层特异性转录同源物 (PEG1/MEST) 区域，由于证据基础的异质性，我们不能排除其他研究序列。更广泛的影响 ART 受孕后 DNA 甲基化的差异不大，成人组织中的功能相关性尚不清楚。需要进一步探索基因表达方面的功能效应以及其他表观遗传标记的作用。此外，由于两种技术之间分析的 CpG 缺乏可比性，在靶向分析和基因组规模分析中获得的结果几乎没有重叠。这个问题还源于样本量小以及方法和队列特征的显着差异。需要方法的标准化和大规模的协作努力，以减少结果的不一致并提高结果的稳健性。最后，需要进一步的研究来确定 ART 治疗对父母不孕症本身的贡献。