胚胎活检时机和方法选择及其对植入前遗传学诊断及筛查结局影响

胚胎活检可以获取细胞进而用于植入前遗传学诊断或植入前遗传学筛查,包括极体活检、卵裂球活检和滋养层细胞活检。胚胎活检不仅要保证所获取的细胞能适用于遗传学诊断的要求,而且还要尽可能地降低活检对胚胎发育的影响。因此,选择一个合适的时机、合适的方法进行胚胎活检十分重要。     

New perspectives on preimplantation genetic diagnosis and preimplantation genetic screening

Preimplantation genetic diagnosis is a procedure that involves the removal of one or more nuclei from oocytes (a polar body) or embryos (blastomeres or trophectoderm cells) in order to test for problems in genome sequence or chromosomes of the embryo prior to implantation. It provides new hope of having unaffected children, as well as avoiding the necessity of terminating an affected pregnancy for genetic parents who carry an affected gene or have balanced chromosomal status. Polymerase chain reaction-based molecular techniques are the methods used to detect gene defects with a known sequence and X-linked diseases. The indication for using this approach has expanded for couples who are prevented from having babies because they carry a serious genetic disorder to couples with conditions that are not immediately life threatening, such as cancer predisposition genes and Huntington disease. In addition, fluorescent in situ hybridization (FISH) has been widely applied for the detection of chromosome abnormalities. FISH allows the evaluation of many chromosomes at the same time, up to 15 chromosome pairs in a single cell. Preimplantation genetic screening, defined as a test that screens for aneuploidy, has been most commonly used in situations of advanced maternal age, a history of recurrent miscarriage, a history of repeated implantation failure, or a severe male factor. Unfortunately, randomized controlled trials have as yet shown no benefit with respect to preimplantation genetic screening using cleavage stage biopsy, which is probably attributable to the high levels of mosaicism at early cleavage stages and the limitations of FISH. Recently, two main types of array-based technology combined with whole genome amplification have been developed for use in preimplantation genetic diagnosis; these are comparative genomic hybridization and single nucleotide polymorphism-based arrays. Both allow the analysis of all chromosomes, and the latter also allows the haplotype of the sample to be determined. The promising results of these two approaches will inspire further validation of these array platforms, even at the single-cell level. It remains to be decided which embryo stage is the best for biopsy. Moreover, if randomized controlled trials are confirmed to play a role in increasing delivery rates, this will be a major step forward for assisted reproductive technology patients around the world.     

植入前遗传学诊断及筛查咨询

随着分子生物学技术的飞速发展及其在生殖领域的应用,植入前遗传学诊断（PGD）、植入前遗传学筛查（PGS）的遗传咨询变得更加复杂。在PGD、PGS的遗传咨询中,医生应充分告知患者PGD、PGS的应用现状、利弊、可能的预后、技术缺陷与安全性问题。同时,经PGD、PGS成功妊娠的孕妇,仍需进行常规的产前诊断,这一点对于PGD、PGS的安全性至关重要。     

植入前遗传学诊断周期促排卵方案选择及特点分析

控制性促排卵是植入前遗传学诊断（PGD）中的关键步骤之一。不同遗传性疾病可供移植的胚胎比例不同,因此对获卵数的要求有所不同。某些遗传性疾病本身对卵巢反应性可能有一定影响。文章首先介绍遗传性疾病中遗传方式决定的可供移植胚胎比例,然后重点分析PGD中控制性促排卵的特点,包括遗传性疾病可能对卵巢反应性的影响以及PGD中促排卵方案的选择和目前文献报道PGD获卵数的截断值。     

Preimplantation genetic diagnosis

This article aims to inform about the current practices in Preimplantation Genetic Diagnosis (PGD) from a United Kingdom perspective. Progress in the field has been marked over the last decade and new techniques have superseded traditional analysis. The review moves from governance and data collection for PGD to the patient journey. We discuss embryo biopsy and the challenges of analysis when starting with a small amount of DNA. Segments are introduced which introduce basic principles to allow better appreciation of the tests and when they should be applied. We discuss PGD for single gene disorders by preimplantation genetic haplotyping, including for autosomal dominant de novo mutations. Translocations are also discussed and PGD by microarray analysis. We conclude by considering next generation sequencing with the advantages and challenges this may provide to the field.     

植入前遗传学诊断100个周期临床分析

目的 探讨染色体易位对早期胚胎发育的影响,以及植入前遗传学诊断(PGD)技术的诊断效率和可行性.方法 回顾性分析PGD中23个罗伯逊(罗氏)易位周期、19个平衡易位周期(染色体易位组),以及58个α地中海贫血周期(地贫组)共100个周期中的胚胎发育情况、PGD的诊断效率以及临床结局.结果 染色体易位组中有354个胚胎进行PGD,321(90.7%)个胚胎有荧光原位杂交(FISH)结果,其中罗氏易位者中正常和(或)平衡易位胚胎占38.3%(64/167),显著高于平衡易位者的20.8%(32/154).地贫组有537个胚胎进行PGD,单个卵裂球的扩增效率为82.5%(443/537),诊断出正常纯合子140个、杂合子112个、异常纯合子155个、另36个诊断结果不明确,总体诊断效率为75.8%(407/537).染色体易位组中,取卵后第3天卵裂球数≥7的胚胎中,正常和(或)平衡易位发生率(34.4%,77/224)显著高于卵裂球数＜7的胚胎(19.6%,19/97),在取卵后第4天,正常和(或)平衡易位胚胎的细胞融合率为59.4%(57/96),显著高于染色体不平衡胚胎的34.2%(77/225).染色体易位组共在37个周期移植了75个胚胎,获得10例临床妊娠,临床妊娠率27.0%(10/37).地贫组共在58个周期移植了170个胚胎,获得25例临床妊娠,临床妊娠率为43.1%(25/58).结论 PGD技术可有效为染色体易位和地中海贫血基因携带者提供优生选择.染色体易位可能对着床前胚胎的发育有一定的影响.

Abstract：

Objective To investigate influence of chromosomal translocations on early embryo development and to evaluate the efficacy and feasibility of preimplantation genetic diagnosis (PGD)techniques through clinical analysis on PGD cycles. Methods Embryo development, efficacy of PGD and clinical outcome of 100 cycles were studied retrospectively, including 23 cycles with Robertsonian translocations, 19 cycles with reciprocal translocations, and 58 cycles for α-Thalassaemia. Results Among 354 embryos biopsied by PGD for translocations, 321 (90. 7% ) presented fluorescence in situ hybridization (FISH) results. The rate of normal/balanced embryos in the Robertsonian translocation was 38. 3% (64/167),which was significantly higher than 20. 8% (32/154) in the reciprocal translocation group. Amplification was achieved in 443 blastomeres from 537 embryos in Thalassaemia group, which given to an amplification efficiency rate of 82. 5% ( 443/537 ). Totally, 140 normal homozygous, 112 heterozygotes and 155 affected homozygous embryos were identified, while 36 embryos had uncertain result. The successful diagnostic rate was 75.8% (407/537). After 3 days in the translocation groups, the rate of normal and/or balanced translocations in biopsed embryos with ≥7 cells was 34. 4% (77/224), which was significantly higher than 19. 6% ( 19/97 ) of biopsed embryos with ＜ 7 cells. After 4 days, the compaction rate in normal/balanced embryos was 59.4% ( 57/96 ), which was significantly higher than 34. 2% ( 77/225 ) in imbalanced embryos significantly. Seventy-five embryos transferred in 37 cycles with translocations group led to clinical pregnancy rate of 27.0% (10/37), and 170 embryos transferred in 58 cycles with Thalassaemia got a clinical pregnancy rate of 43. 1% ( 25/58 ) . Conclusions PGD can provide management efficiently for both chromosome translocations and Thalassaemia. Translocations might have slightly negative impact on embryo development before implantation.     

Linking back-to-back stimulation cycles with oral contraceptives or progestins in women undergoing embryo accumulation for preimplantation genetic testing,a retrospective study

Abstract

The purpose of this study was to determine the pregnancy rate in the double sequential transfer of embryos on both day 3 and day 5 compared to day 5 alone, in in vitro fertilization-embryo transfer (IVF/ET) in patients with the three repeated consecutive IVF failures. In this controlled trial, women scheduled for IVF/ET with the three repeated consecutive IVF failures were randomized to either sequential transfer of embryos on day 2 and on day 5 after ovum pick-up (group 1, n = 60) or blastocyst ET on day 5 (group 2, n = 60) as a control group. The primary outcome measures were the chemical and clinical pregnancy rate. Baseline and cycle characteristics were comparable in both groups. Chemical and clinical pregnancy rate was similar in the sequential ET group (40%) compared to the day 5 of ET group (38.3%) (p value = .85). It seems that the double ET does not increase the chance of pregnancy rate compared to blastocyst ET on day 5 in the patients with the three repeated IVF-ET failures.     

植入前遗传学诊断技术风险环节

植入前遗传学诊断（PGD）相关的技术在近20年迅猛发展,随之而来的是在技术应用时可能存在的问题和风险。从遗传咨询到胚胎培养、活检,再到遗传学诊断的各个环节都有需要引起重视的问题。等位基因脱扣和早期胚胎的染色体嵌合现象是目前诊断中最主要的导致误诊的风险因素。文章就目前PGD中各个可能的风险环节以及相应的应对措施进行阐述。     

Reproductive outcomes after preimplantation genetic testing in mosaic Turner syndrome: a retrospective cohort study of 100 cycles

PurposeThe purpose of this study is to explore the reproductive outcomes of women with Turner syndrome (TS) in preimplantation genetic testing (PGT) cycles.MethodsA retrospective study of 100 controlled ovarian stimulating cycles, 68 TS (sixty-four mosaic Turner syndrome (MTS) and four pure Turner syndrome (PTS)) women underwent PGT was conducted from 2013 to 2018.ResultsEmbryo X chromosome abnormal rates of TS women were significantly higher than women with normal karyotype (7.04 vs 1.61%, P<0.01). Cumulative live birth rates (CLBR) after PGT-NGS treatment were lower in TS than control (31.15 vs 45.59%, P<0.05). Clinical pregnancy rates per transfer (CPR), miscarriage rates (MR) and live birth rates per transfer (LBR) remained comparable between TS and control group. Reproductive outcomes (X chromosome abnormal rates, CPR, MR, LBR and CLBR) among low (<10%), medium (10–50%) and high (>50%) level 45,X mosaicism groups were not statistically different.ConclusionsTo avoid high risk of embryo X chromosome abnormalities, prenatal or preimplantation genetic testing should be recommended to mosaic or pure TS patients.     

Over a decade of experience with preimplantation genetic diagnosis: a multicenter report

OBJECTIVE: To review a 12-year experience of the world's three largest preimplantation genetic diagnosis (PGD) centers. DESIGN: Multicenter analysis of the clinical outcome of PGD. SETTING: In vitro fertilization programs at the Reproductive Genetics Institute, Chicago, Illinois; Saint Barnabas Medical Center, West Orange, New Jersey; and SISMER, Bologna, Italy. PATIENT(S): Poor-prognosis IVF patients, patients carrying balanced chromosomal translocations, and couples at risk for producing children with Mendelian disorders. INTERVENTION(S): In vitro fertilization, intracytoplasmic sperm injection, polar body removal, blastomere biopsy, and ET. MAIN OUTCOME MEASURE(S): DNA or chromosomal analysis of biopsied polar bodies or blastomeres, implantation and clinical pregnancy rates, and live-born pregnancy outcome. RESULT(S): A total of 754 babies have been born as a result of 4,748 PGD attempts, which shows the expanded application and the practical relevance of PGD for single-gene disorders, chromosomal aneuploidies and translocations, late-onset diseases with genetic predisposition, and nondisease testing in couples at need for human leukocyte antigens-matched offspring for treatment of affected siblings. CONCLUSION(S): Preimplantation genetic diagnosis is evolving to become a clinical option for couples at risk for producing offspring with Mendelian diseases, has a positive numerical impact in standard assisted reproduction practices through aneuploidy testing, and reduces by at least fourfold the spontaneous abortion rate in couples carrying translocations.     

单基因病植入前遗传学诊断难点及误诊原因分析

可供检测的遗传物质极少是单基因病植入前遗传学诊断（PGD）的瓶颈问题。单基因病PGD误诊的原因主要包括单细胞聚合酶链反应（PCR）固有问题、胚胎细胞固有问题以及与诊断技术不相关的人为错误等。文章首先分析单基因PGD的诊断难点,在此基础上介绍欧洲人类生殖与胚胎协会（ESHRE）PGD联盟报道的误诊案例及其对诊断技术的验证。