Departments of Obstetrics & Gynecology, and Biochemistry, University of Western Ontario, Schulich School of Medicine and Dentistry, London, Ontario, Canada.
Biol Reprod. 2012 May 10;86(5):143, 1-16. doi: 10.1095/biolreprod.111.096602. Print 2012 May.
Currently, the stage of embryo development has been proposed as one of many criteria for identifying healthy embryos in infertility clinics with the fastest embryos being highlighted as the healthiest. However the validity of this as an accurate criterion with respect to genomic imprinting is unknown. Given that embryo development in culture generally requires an extra day compared to in vivo development, we hypothesized that loss of imprinting correlates with slower rates of embryonic development. To evaluate this, embryos were recovered at the 2-cell stage, separated into four groups based on morphological stage at two predetermined time points, and cultured to blastocysts. We examined cell number, embryo volume, embryo sex, imprinted Snrpn and H19 methylation, imprinted Snrpn, H19, and Cdkn1c expression, and expression of genes involved in embryo metabolism-Atp1a1, Slc2a1, and Mapk14-all within the same individual embryo. Contrary to our hypothesis, we observed that faster developing embryos exhibited greater cell numbers and embryo volumes as well as greater perturbations in genomic imprinting and metabolic marker expression. Embryos with slower rates of preimplantation development were most similar to in vivo derived embryos, displaying similar cell numbers, embryo volumes, Snrpn and H19 imprinted methylation, H19 imprinted expression, and Atp1a1 and Slc2a1 expression. We conclude that faster development rates in vitro are correlated with loss of genomic imprinting and aberrant metabolic marker expression. Importantly, we identified a subset of in vitro cultured embryos that, according to the parameters evaluated, are very similar to in vivo derived embryos and thus are likely most suitable for embryo transfer.
目前，胚胎发育阶段已被提出作为鉴定不孕不育诊所中健康胚胎的众多标准之一，其中发育最快的胚胎被认为是最健康的。然而，就基因组印迹而言，这种标准的有效性尚不清楚。鉴于胚胎在培养中通常需要比体内发育多一天，我们假设印迹丢失与胚胎发育速度较慢有关。为了评估这一点，我们将胚胎回收至 2 细胞期，根据在两个预定时间点的形态阶段将其分为四组，并培养至囊胚期。我们检查了细胞数量、胚胎体积、胚胎性别、印迹的 Snrpn 和 H19 甲基化、印迹的 Snrpn、H19 和 Cdkn1c 表达以及与胚胎代谢相关的基因的表达-Atp1a1、Slc2a1 和 Mapk14-均在同一个胚胎内。与我们的假设相反，我们观察到发育较快的胚胎表现出更多的细胞数量和胚胎体积，以及更大的基因组印迹和代谢标志物表达的干扰。具有较慢的胚胎植入前发育速度的胚胎与体内来源的胚胎最相似，表现出相似的细胞数量、胚胎体积、Snrpn 和 H19 印迹甲基化、H19 印迹表达以及 Atp1a1 和 Slc2a1 表达。我们得出结论，体外发育速度较快与基因组印迹丢失和代谢标志物表达异常相关。重要的是，我们确定了一组体外培养的胚胎，根据评估的参数，与体内来源的胚胎非常相似，因此最适合胚胎移植。
