PGS-FISH in reproductive medicine and perspective directions for improvement: a systematic review

Role of miRNAs in preimplantation embryo development and their potential as embryo selection biomarkers

CONTEXT

MicroRNAs (miRNAs) play different roles in oocyte fertilisation, degradation of maternal transcripts, embryo development, and implantation. During in vitro fertilisation (IVF), different miRNAs are released from embryos into the spent culture media (SCM) that can potentially reflect the status of the embryo.

AIMS

This study is the assessment of miRNAs, which secreted in SCM during the IVF cycles can be used as noninvasive biomarkers to predict an embryo's ability to form a blastocyst, implant, and give live birth.

METHODS

Systematic literature search was conducted to review all recent studies about miRNAs as potential non-invasive biomarkers for selecting the best embryos in the assisted reproductive technology (ART) cycle.

KEY RESULTS

Studies have shown that levels of some miRNAs in the SCM have an association with the implantation potential and pregnancy outcome of the embryo.

CONCLUSIONS

Embryo-secreted miRNAs can be used as potential non-invasive biomarkers for selecting the best embryos in the ART cycle. Unfortunately, few human studies evaluated the association between ART outcomes and miRNAs in SCM.

IMPLICATIONS

This review can pave the way for further miRNAs transcriptomic studies on human embryo culture media and introducing a specific miRNA profile as a multivariable prediction model for embryo selection in IVF cycles.

D-karyo-A New Prenatal Rapid Screening Test Detecting Submicroscopic CNVs and Mosaicism

Chromosomal microarray analysis (CMA), recently introduced following conventional cytogenetic technology, can detect submicroscopic copy-number variations (CNVs) in cases previously diagnosed as "cytogenetically benign". At present, rapid and accurate chromosomal analysis is required in prenatal diagnostics, but prenatal CMA is not widely used due to its high price and long turnaround time. We introduced a new prenatal screening method named digital karyotyping (D-karyo), which utilizes a preimplantation genetic test for the aneuploidy (PGT-A) platform. First, we conducted a preliminary experiment to compare the original PGT-A method to our modified method. Based on the preliminary results, we decided to implement the modified strategy without whole-genome amplification (WGA) and combined it with three analytical software packages. Next, we conducted a prospective study with 824 samples. According to the indication for invasive tests, the D-karyo positive rates were 2.5% and 5.0%, respectively, in the screening positive group with NT ≥ 3.5 mm and the group with fetal abnormalities by ultrasound. D-karyo is a breakthrough modality that can detect submicroscopic CNVs ≥ 1.0 Mb accurately in only 10.5 h for 24 samples at a low cost. Implementing D-karyo as a prenatal rapid screening test will reduce unnecessary CMA and achieve more accurate prenatal genetic testing than G-banding.

MicroRNAs secreted by human embryos could be potential biomarkers for clinical outcomes of assisted reproductive technology

Introduction

MicroRNAs (miRNAs) are important regulators of many biological functions, including embryo implantation and development. Recently, it has been reported that miRNAs in biofluids are predictive for physiological and pathological processes.

Objectives

In this study, we aim to investigate whether the miRNAs secreted by human embryos in culture medium can be used as embryonic biomarkers.

Methods

The culture media were prospectively collected from embryos of patients at reproductive medicine center with informed consent. A high-throughput miRNA sequencing method was applied to detect the miRNA profiles in the human embryo culture media. After bioinformatics analysis and screening of differentially expressed miRNAs, quantitative real-time polymerase chain reaction (qRT-PCR) assay was subsequently performed to further confirm the sequencing results with mixed samples. Furthermore, we performed droplet digital PCR (ddPCR) to verify the target miRNAs at single sample level. Receiver operating characteristic (ROC) analyses were performed for differentially expressed miRNAs.

Results

Compared with embryos with failed pregnancy, the embryos with successful pregnancy secreted different miRNA profiles into the culture media, which were predicted to be involved in multiple biological processes. Validated by droplet digital polymerase chain reaction (ddPCR), the expression of hsa-miR-26b-5p and hsa-miR-21-5p in the culture media of cleavage embryos with successful pregnancy was significantly lower than that of embryos with failed pregnancy. Moreover, the Receiver Operating Characteristic (ROC) curve analysis indicated that hsa-miR-26b-5p and hsa-miR-21-5p could serve as potential biomarkers for reproductive outcomes.

Conclusion

Together, our findings highlight the important predictive potential of miRNAs secreted by human embryos in culture media, which is meaningful for non-invasive embryo selection in assisted reproductive technology.

Development of assisted reproductive technology services in Thailand between 2008 and 2014 before the new law: Results generated from the National ART Registry, Royal Thai College of Obstetricians and Gynecologists

Background

While the assisted reproductive technology (ART) relieves the burden of infertility in many couples, it presents significant public health challenges due to the substantial risk for multiple birth delivery and preterm birth, which are associated with poor maternal and fetal health outcomes. For this reason, it is important to monitor the development and effectiveness of ART services in Thailand.

Objective

To analyze the trends of ART services in Thailand between 2008 and 2014.

Methods

ART clinics in Thailand are required to submit data to the Royal Thai College of Obstetricians and Gynecologists via the National Reporting System. The data from 2008 to 2014 were collected and analyzed.

Results

The number of ART centers was increased from 35 to 47. The total fresh ART cycles were also increased from 3,723 to 6,516. The percentage values of intracytoplasmic sperm injection (ICSI), in vitro fertilization, gamete intrafallopian transfer, and zygote intrafallopian transfer cycles were changed from 77.87 to 95.59, 21.43 to 4.31, 0.21 to 0.09, and 0.45 to 0.05, respectively. The clinical pregnancy rates were 28.79–33.19, 22.84–51.34, 14.29–42.86, and 0.00–26.67, respectively. The clinical pregnancy rates in fresh vs. frozen-thawed cycles were 31.01–36.33 vs. 31.54–37.34 (P < 0.05). The clinical pregnancy rates in female age <35 vs. 35–39 vs. ≥40 years were 36.97–40.70 vs. 32.74–33.42 vs. 21.08–31.34, respectively (P < 0.001), and the percentage values of multifetal pregnancy rate were 18.75 vs. 13.30 and 13.69, respectively (P < 0.001). There were increasing preimplantation genetic screening (PGS) cycles, with the percentage of the clinical pregnancy rate (25.90–42.63, P < 0.05). The clinical pregnancy rates in medium-sized ART centers (100–300 cycles per year) vs. in small and large centers were 30.79–41.14 vs. 28.01–34.04 and 8.70–40.35, respectively (P < 0.001). Trends of increasing percentage of ART birth rate to total birth rate ratio were 0.24–0.34 (P < 0.05).

Conclusions

There were higher clinical pregnancy rates in frozen-thawed cycles. Higher multifetal pregnancy rate and clinical pregnancy rate were also found in younger females. There were increasing uses of ICSI and PGS. A trend toward increasing ART birth to total birth ratio was observed.

Is the resulting phenotype of an embryo with balanced X-autosome translocation, obtained by means of preimplantation genetic diagnosis, linked to the X inactivation pattern?

OBJECTIVE

To examine if a balanced female embryo with X-autosome translocation could, during its subsequent development, express an abnormal phenotype.

DESIGN

Preimplantation genetic diagnosis (PGD) analysis on two female carriers with maternal inherited X-autosome translocations.

SETTING

Infertility center and genetic laboratory in a public hospital.

PATIENT(S)

Two female patients carriers undergoing PGD for a balanced X-autosome translocations: patient 1 with 46,X,t(X;2)(q27;p15) and patient 2 with 46,X,t(X;22)(q28;q12.3).

INTERVENTION(S)

PGD for balanced X-autosome translocations.

MAIN OUTCOME MEASURE(S)

PGD outcomes, fluorescence in situ hybridization in biopsied embryos and meiotic segregation patterns analysis of embryos providing from X-autosome translocation carriers.

RESULT(S)

Controlled ovarian stimulation facilitated retrieval of a correct number of oocytes. One balanced embryo per patient was transferred and one developed, but the patient miscarried after 6 weeks of amenorrhea. In X-autosome translocation carriers, balanced Y-bearing embryos are most often phenotypically normal and viable. An ambiguous phenotype exists in balanced X-bearing embryos owing to the X inactivation mechanism. In 46,XX embryos issued from an alternate segregation, der(X) may be inactivated and partially spread transcriptional silencing into a translocated autosomal segment. Thus, the structural unbalanced genotype could be turned into a viable functional balanced one. It is relevant that a discontinuous silencing is observed with a partial and unpredictable inactivation of autosomal regions. Consequently, the resulting phenotype remains a mystery and is considered to be at risk of being an abnormal phenotype in the field of PGD.

CONCLUSION(S)

It is necessary to be cautious regarding to PGD management for this type of translocation, particularly in transferred female embryos.

Human embryos secrete microRNAs into culture media--a potential biomarker for implantation

OBJECTIVE

To determine whether human blastocysts secrete microRNA (miRNAs) into culture media and whether these reflect embryonic ploidy status and can predict in vitro fertilization (IVF) outcomes.

DESIGN

Experimental study of human embryos and IVF culture media.

SETTING

Academic IVF program.

PATIENT(S)

91 donated, cryopreserved embryos that developed into 28 tested blastocysts, from 13 couples who had previously completed IVF cycles.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Relative miRNA expression in IVF culture media.

RESULT(S)

Blastocysts were assessed by chromosomal comparative genomic hybridization analysis, and the culture media from 55 single-embryo transfer cycles was tested for miRNA expression using an array-based quantitative real-time polymerase chain reaction analysis. The expression of the identified miRNA was correlated with pregnancy outcomes. Ten miRNA were identified in the culture media; two were specific to spent media (miR-191 and miR-372), and one was only present in media before the embryos had been cultured (miR-645). MicroRNA-191 was more highly concentrated in media from aneuploid embryos, and miR-191, miR-372, and miR-645 were more highly concentrated in media from failed IVF/non-intracytoplasmic sperm injection cycles. Additionally, miRNA were found to be more highly concentrated in ICSI and day-5 media samples when compared with regularly inseminated and day-4 samples, respectively.

CONCLUSION(S)

MicroRNA can be detected in IVF culture media. Some of these miRNA are differentially expressed according to the fertilization method, chromosomal status, and pregnancy outcome, which makes them potential biomarkers for predicting IVF success.

Chromosomal integrity of human preimplantation embryos at different days post fertilization

INTRODUCTION

In order to investigate the dynamics of genomic alterations that occur at different developmental stages in vitro, we examined the chromosome content of human preimplantation embryos by molecular-cytogenetic techniques at the single-cell level, up to 13 days post fertilization.

METHODS

The embryos were genetically analyzed several times during their development in culture; each embryo was first analyzed by FISH at 'Day 3' post fertilization, than during its growth in vitro and the third analysis was performed at development arrest, then the entire blastocyst was analyzed by comparative genomic hybridization (CGH/aCGH).

RESULTS

We found that while on 'Day 3' only 31% of the embryos were detected as normal, on 'Day 5-6', 44% of the embryos were classified as normal and on 'Day 7', 57% were normal. On 'Days 8-13', 52% of the embryos were classified as chromosomally normal. One third of the embryos that were chromosomally abnormal on 'Day 3', were found to be normal at development arrest point.

DISCUSSION

These dynamic changes that occur at early developmental stages suggest that testing a single blastomere at 'Day 3' post fertilization for PGD might inaccurately reflect the embryo ploidy and increase the risk of false aneuploidy diagnosis. Alternatively, blastocyst stage diagnosis may be more appropriate.

[Preimplantation genetic diagnosis--developments to expect?]

Preimplantation genetic diagnosis (PGD) has been practiced for over 20 years. It prevents the birth of children with serious genetic diseases by selecting healthy embryos before pregnancy. In France, the initial indications of PGD have been extended in two directions: on the one hand, to allow identification of a mutation combined with embryo's HLA typing, to obtain, at birth, stem cells for therapeutic purposes, and on the other hand, to avoid transmission of late onset diseases without having to test the at-risk parent. Other applications are practiced worldwide but are not allowed in our country, such as social sexing. Technological developments can enable more complex diagnosis, research of several diseases or other genetic traits. It may be useful, for example, to use this possibility to add screening for Down's syndrome at any PDG in older women, when the risk is high. Other objectives were considered but presenting difficulties in their application, not only for regulatory and technical reasons, but also from an ethical point of view.