Table5_Mitochondrial DNA mutations can influence the post-implantation development of human mosaic embryos.DOCX

Introduction: Several healthy euploid births have been reported following the transfer of mosaic embryos, including both euploid and aneuploid blastomeres. This has been attributed to a reduced number of aneuploid cells, as previously reported in mice, but remains poorly explored in humans. We hypothesized that mitochondrial function, one of the most critical factors for embryonic development, can influence human post-implantation embryonic development, including a decrease of aneuploid cells in mosaic embryos. Methods: To clarify the role of mitochondrial function, we biopsied multiple parts of each human embryo and observed the remaining embryos under in vitro culture as a model of post-implantation development (n = 27 embryos). Karyotyping, whole mitochondrial DNA (mtDNA) sequencing, and mtDNA copy number assays were performed on all pre- and post-culture samples. Results: The ratio of euploid embryos was significantly enhanced during in vitro culture, whereas the ratio of mosaic embryos was significantly reduced. Furthermore, post-culture euploid and culturable embryos had significantly few mtDNA mutations, although mtDNA copy numbers did not differ. Discussion: Our results indicate that aneuploid cells decrease in human embryos post-implantation, and mtDNA mutations might induce low mitochondrial function and influence the development of post-implantation embryos with not only aneuploidy but also euploidy. Analyzing the whole mtDNA mutation number may be a novel method for selecting a better mosaic embryo for transfer.引言：已有研究报道，移植包含整倍体（euploid）与非整倍体（aneuploid）卵裂球（blastomeres）的嵌合胚胎（mosaic embryos）后，可诞生多例健康的整倍体新生儿。此类现象的成因被认为是非整倍体细胞数量的减少，该机制此前已在小鼠模型中得到验证，但在人类中仍鲜有探索。本研究提出假说：作为胚胎发育最关键的影响因素之一的线粒体功能（mitochondrial function），可调控人类植入后胚胎发育（post-implantation embryonic development），包括降低嵌合胚胎中的非整倍体细胞比例。 方法：为阐明线粒体功能在该过程中的作用，我们对每一枚人类胚胎的多个部位进行活检，并将剩余胚胎进行体外培养（in vitro culture）以作为植入后发育的体外模型（共纳入27枚胚胎）。对所有培养前后的样本均开展了核型分析（karyotyping）、全线粒体DNA（mtDNA）测序以及mtDNA拷贝数检测。 结果：体外培养过程中，整倍体胚胎的占比显著升高，而嵌合胚胎的占比则显著降低。此外，培养后存活的整倍体与可培养胚胎的mtDNA突变数量显著更少，尽管其mtDNA拷贝数并无显著差异。 讨论：本研究结果表明，人类胚胎植入后非整倍体细胞数量会出现减少，且mtDNA突变可能会诱发线粒体功能低下，进而影响携带非整倍体与整倍体的植入后胚胎发育。对全mtDNA突变数量进行分析，或可成为筛选更优质可移植嵌合胚胎的全新方法。