A systematic review of the literature showed that trophectoderm biopsy could assist in the selection of healthy embryos for uterine transfer without affecting implantation rates. However, previous studies attempting to establish the relationship between trophectoderm gene expression profiles and implantation competency using either microarrays or RNA sequencing strategies, were not sufficiently optimized to handle the exceptionally low RNA inputs available from biopsied material. In this pilot study, we report that differential gene expression in human trophectoderm biopsies assayed by an ultra-sensitive next generation RNA sequencing strategy could predict blastocyst implantation competence. RNA expression profiles from isolated human trophectoderm cells were analysed with established clinical pregnancy being the primary endpoint. Following RNA sequencing, a total of 47 transcripts were found to be significantly differentially expressed between the trophectoderm cells from successfully implanted (competent) versus unsuccessful (incompetent) blastocysts. Of these, 36 transcripts were significantly down-regulated in the incompetent blastocysts, including Hydroxysteroid 17-Beta Dehydrogenase 1 (HSD17B1) and Cytochrome P450 Family 11 Subfamily A Member 1 (CYP11A1), while the remaining 11 transcripts were significantly up-regulated, including BCL2 Antagonist/Killer 1 (BAK1) and KH Domain Containing 1 Pseudogene 1 (KHDC1P1) of which the latter was always detected in the incompetent and absent in all competent blastocysts. Ontological analysis of differentially expressed RNAs revealed pathways involved in steroidogenic processes with high confidence. Novel differentially expressed transcripts were also noted by reference to a de novo sequence assembly. The selection of the blastocyst with the best potential to support full-term pregnancy following single embryo transfer could reduce the need for multiple treatment cycles and embryo transfers. The main limitation was the low sample size (N = 8). Despite this shortcoming, the pilot suggests that trophectoderm biopsy could assist with the selection of healthy embryos for embryo transfer. A larger cohort of samples is needed to confirm these findings.

Abbreviations: AMA: advanced maternal age; ART: assisted reproductive technology; CP: clinical pregnancy; DE: differential expression; FDR: false discovery rate; IVF: in vitro fertilization; LD PCR: long distance PCR; qRT-PCR: quantitative real-time PCR; SET: single embryo transfer; TE: trophectoderm

对文献的系统回顾表明，滋养外胚层活检可以帮助选择健康胚胎进行子宫移植，而不影响着床率。然而，之前的研究尝试使用微阵列或RNA测序策略建立滋养外胚层基因表达谱与植入能力之间的关系，但没有得到充分优化，无法处理来自活检材料的极低RNA输入。在这项初步研究中，我们报告说，通过超灵敏的下一代 RNA 测序策略测定的人类滋养外胚层活检中的差异基因表达可以预测囊胚植入能力。以已确定的临床妊娠为主要终点，对分离的人滋养外胚层细胞的 RNA 表达谱进行了分析。 RNA 测序后，发现成功植入（有能力）的胚泡与不成功（无能力）囊胚的滋养外胚层细胞之间总共有 47 个转录本存在显着差异表达。其中，36个转录本在无能囊胚中显着下调，包括羟基类固醇17-β脱氢酶1（ HSD17B1 ）和细胞色素P450家族11亚家族A成员1（ CYP11A1 ），而其余11个转录本显着上调，包括BCL2拮抗剂/杀伤剂 1 ( BAK1 ) 和含有 1 个假基因的 KH 结构域 1 ( KHDC1P1 )，其中后者总是在无能力囊胚中检测到，而在所有有能力囊胚中均不存在。差异表达 RNA 的本体论分析高度可信地揭示了类固醇生成过程中涉及的途径。 还通过参考从头序列组装注意到新的差异表达转录本。在单胚胎移植后选择最有可能支持足月妊娠的囊胚可以减少多个治疗周期和胚胎移植的需要。主要限制是样本量较小（N = 8）。尽管存在这一缺点，该试点项目表明滋养外胚层活检可以帮助选择健康胚胎进行胚胎移植。需要更多的样本来证实这些发现。

缩写： AMA：高龄产妇； ART：辅助生殖技术； CP：临床妊娠； DE：差异表达； FDR：错误发现率； IVF：体外受精； LD PCR：长距离PCR； qRT-PCR：实时定量PCR； SET：单胚胎移植； TE：滋养外胚层