Clinic for Reproductive Medicine and Preimplantation Genetic Diagnosis, Repromeda, Biology Park, Studentská 812/6, 625 00 Brno, Czech Republic.
Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic.
Mol Hum Reprod. 2020 Apr 24;26(4):269-276. doi: 10.1093/molehr/gaaa012.
Chromosomal mosaicism detected during preimplantation genetic testing for aneuploidy (PGT-A) and its impact on embryo implantation have been widely discussed, and healthy live births from mosaic embryos were reported by many groups. On the other hand, only very few studies have focused on segmental chromosome aneuploidies and their clinical impact. Eighty-nine embryos with various PGT-A results (trophectoderm 1: TE1) were re-analysed using a second trophectoderm biopsy (TE2) and the rest of the embryo (RE) for testing. Of 19 euploid TE1 biopsies, 18 were concordant across TE2 and RE. Similarly, whole chromosomal aneuploidies were concordant in 59 of 62 TE1-TE2 and 58 TE1-RE. In contrast, from 31 segmental aneuploidies detected in TE1, only 15 were observed again in TE2 and 14 in RE. If a TE1 segmental abnormality appeared again in TE2, it was almost always present in RE (17/18) as well. Moreover, when a TE1 segmental abnormality was not detected in TE2, in 12 out of 13 cases RE was also unaffected. Similarly, only 1 of 26 TE1 whole chromosome mosaics were repeated in TE2 and 7 in RE. Our study confirms that euploid and whole chromosomal aneuploidy results are highly predictive of the embryo. In contrast, mosaicism has a very low concordance rate. Most importantly, re-biopsy of embryos with segmental aneuploidies demonstrated that they are mostly not uniform across the embryo. Finally, in the case of segmental aneuploidy, the second biopsy enables an accurate prediction of the real status of the embryo and could be offered to patients undergoing PGT-A.
胚胎植入前遗传学检测（PGT-A）中发现的染色体嵌合及其对胚胎着床的影响已被广泛讨论，许多研究组报道了来自嵌合胚胎的健康活产儿。另一方面，只有极少数研究集中在片段性染色体非整倍体及其临床影响上。对 89 个具有不同 PGT-A 结果（滋养外胚层 1：TE1）的胚胎进行了重新分析，使用第二次滋养外胚层活检（TE2）和胚胎的其余部分（RE）进行检测。在 19 个整倍体 TE1 活检中，18 个与 TE2 和 RE 一致。同样，在 59 个 TE1-TE2 和 58 个 TE1-RE 中，全染色体非整倍体是一致的。相比之下，在 TE1 中检测到的 31 个片段性非整倍体中，只有 15 个在 TE2 中再次出现，14 个在 RE 中出现。如果 TE1 中的片段异常再次出现在 TE2 中，几乎总是在 RE 中也存在（17/18）。此外，当 TE1 中的片段异常在 TE2 中未被检测到时，在 13 例中有 12 例 RE 也未受影响。同样，在 26 个 TE1 全染色体嵌合体中，只有 1 个在 TE2 中重复，7 个在 RE 中重复。我们的研究证实，整倍体和全染色体非整倍体结果对胚胎具有高度预测性。相比之下，嵌合体的一致性非常低。最重要的是，对片段性非整倍体胚胎进行再次活检表明，它们在胚胎中大多不均匀。最后，在片段性非整倍体的情况下，第二次活检可以准确预测胚胎的真实情况，并可以提供给接受 PGT-A 的患者。
