Identifying parental and cell-division origins of aneuploidy in the human blastocyst

Preimplantation genetic testing commonly employs simplistic copy-number analyses to screen for aneuploidy in blastocyst trophectoderm biopsies. Interpreting intermediate copy number alone as evidence of mosaicism has led to suboptimal estimation of its prevalence. Because mosaicism originates from mitotic nondisjunction, utilizing SNP microarray technology to identify the cell-division origins of aneuploidy might provide a more accurate estimation of its prevalence. The present study develops and validates a method of determining the cell-division origin of aneuploidy in the human blastocyst by using both genotyping and copy-number data in parallel. The concordance of predicted origins with expected results was demonstrated in a series of truth models (99%-100%). This included determination of X chromosome origins from a subset of normal male embryos, determination of the origins of translocation chromosome-related imbalances via embryos from couples with structural rearrangements, and prediction of either mitotic or meiotic origins via multiple rebiopsies of embryos with aneuploidy. In a cohort of blastocysts with parental DNA (n = 2,277), 71% were euploid, 27% were meiotic aneuploid, and 2% were mitotic aneuploid, indicating a low frequency of bona fide mosaicism in the human blastocyst (mean maternal age: 34.4). Chromosome-specific trisomies in the blastocyst were also consistent with observations previously established in products of conception. The ability to accurately identify mitotic-origin aneuploidy in the blastocyst could benefit and better inform individuals whose IVF cycle results in all aneuploid embryos. Clinical trials with this methodology might also help provide a definitive answer regarding the reproductive potential of bona fide mosaic embryos.

Preimplantation genetic testing for aneuploidy versus morphology as selection criteria for single frozen-thawed embryo transfer in good-prognosis patients: a multicenter randomized clinical trial

OBJECTIVE

To evaluate the benefit of next-generation sequencing (NGS)-based preimplantation genetic testing for aneuploidy (PGT-A) for embryo selection in frozen-thawed embryo transfer.

DESIGN

Randomized controlled trial.

SETTING

Not applicable.

PATIENT(S)

Women aged 25-40 years undergoing IVF with at least two blastocysts that could be biopsied.

INTERVENTION(S)

Randomization for single frozen-thawed embryo transfer with embryo selection based on PGT-A euploid status versus morphology.

MAIN OUTCOME MEASURE(S)

Ongoing pregnancy rate (OPR) at 20 weeks' gestation per embryo transfer.

RESULT(S)

A total of 661 women (average age 33.7 ± 3.6 years) were randomized to PGT-A (n = 330) or morphology alone (n = 331). The OPR was equivalent between the two arms, with no significant difference per embryo transfer (50% [137/274] vs. 46% [143/313]) or per intention to treat (ITT) at randomization (41.8% [138/330] vs. 43.5% [144/331]). Post hoc analysis of women aged 35-40 years showed a significant increase in OPR per embryo transfer (51% [62/122] vs. 37% [54/145]) but not per ITT.

CONCLUSION(S)

PGT-A did not improve overall pregnancy outcomes in all women, as analyzed per embryo transfer or per ITT. There was a significant increase in OPR per embryo transfer with the use of PGT-A in the subgroup of women aged 35-40 years who had two or more embryos that could be biopsied, but this was not significant when analyzed by ITT.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02268786.

Maternal age, morphology, development and chromosome abnormalities in over 6000 cleavage-stage embryos

Previous studies assessing the relationship between embryo development, maternal age and chromosome abnormalities were either small or analysed mostly embryos not suitable for replacement. The present study includes >6000 embryos, including many suitable for replacement. Embryos with the best morphology and development were 44% euploid in patients younger than 35, decreasing to 21% in patients 41 and older. The worst morphology group had only 30% normal embryos from patients younger than 35, and 12% in embryos from patients 41 and older. Thus morphological analysis was able to improve the population of normal embryos only from 30 to 44% in the best of cases. Regarding specific abnormalities, 20% of embryos were aneuploid, 32% aneuploid plus other abnormalities, and the rest had post-meiotic abnormalities. Of those, only aneuploidy increased with maternal age. There were no big differences in the frequency of chromosome abnormalities depending on patient indication, within a similar age group. In summary, previous trends detected in suboptimal embryos were also confirmed in the best embryos for replacement. Although dysmorphism and advanced maternal age are both related to chromosome abnormalities, these parameters can yield at most <50% euploid embryos, and other techniques such as preimplantation diagnosis are required to ensure that only euploid embryos are replaced.

Self-correction of chromosomally abnormal embryos in culture and implications for stem cell production

OBJECTIVE

To ascertain whether embryos classified by preimplantation genetic diagnosis (PGD) for infertility as abnormal and then plated to obtain stem cells would self-correct partially or totally in culture, producing disomic stem cells.

DESIGN

Prospective study to determine the chromosome status of embryos on day 3 and 6, as well as cultured cells derived from inner cell masses from the same embryos when cultured up to day 12.

SETTING

Research laboratory.

PATIENT(S)

Patients undergoing PGD of aneuploidy.

INTERVENTION(S)

Of 142 embryos classified by PGD for aneuploidy as abnormal, 50 were cultured to the blastocyst stage. At that stage a fraction of the embryos underwent trophectoderm biopsy to reconfirm the PGD diagnosis. After further co-culture with feeders up to day 12, 34 embryos attached to the feeder cells. Of those, 24 were analyzed by fluorescence in situ hybridization (FISH) and the rest for the expression of Oct-4, SSEA-3, SSEA-4, TRA1-60, and TRA1-80.

MAIN OUTCOME MEASURE(S)

Disomic cells obtained from trisomic embryos.

RESULT(S)

Analysis by FISH of day-12 cultures showed that 7 were totally normal, 6 were mostly abnormal, and 11 had experienced some chromosome normalization, having between 21% and 88% normal cells. Day-12 culture was positive for Oct-4 expression by reverse transcriptase polymerase chain reaction analysis and for SSEA-3, SSEA-4, TRA1-60, and TRA1-80 by immunocytochemistry.

CONCLUSION(S)

Chromosome self-normalization occurs in a significant proportion of chromosomally abnormal embryos, possibly because of the loss of a chromosome in trisomic cells after blastocyst stage. Thus chromosomally abnormal embryos are a potential source of disomic stem cells. Not all chromosomally abnormal embryos self-corrected. Abnormal stem cells that might be derived could be used as models to study the effect of chromosomal abnormalities on human development.

Cryopreservation of unfertilized human oocytes

Previous investigations revealed that choline-based freezing media developed in our laboratory were superior to conventional sodium-based media for storing mouse oocytes. This paper examines the ability of the choline-based medium CJ2 and a modified form of this medium, CJ3, to cryopreserve unfertilized human oocytes. Oocytes that were consented for research and matured overnight, as well as freshly collected, donor, mature metaphase II (MII) oocytes, were cryopreserved using choline-based media and an optimized slow-cooling protocol. The results showed higher survival and fertilization rates when CJ3 supplemented with 0.2 mmol/l sucrose was used as compared with CJ2 supplemented with either 0.1 mmol/l or 0.2 mmol/l sucrose. Freshly collected oocytes were more difficult to cryopreserve than those matured in vitro. Modification of the base medium proved to be one of the key factors in obtaining survival rates over 90%. Fertilization rates, embryo development, and genetic analysis of embryos resulting from control and frozen-thawed oocytes are provided. There appears to be a high correlation between chromosomal anomalies and abnormal morphology in embryos from thawed oocytes.

Inhibition of human spermatozoa–zona pellucida binding by a combinatorially derived peptide from a synthetic target

Intact zona-free human oocytes were screened using a combinatorial peptide library selection protocol. Pieczenik Peptide Sequence 1 (PPS1) HEHRKRG binds human spermatozoa. A complementary and unique binding sequence HNSSLSPLATPA (PPS2) was developed from the first PPS1 ligand that binds to the human zona pellucida or oolemma. Cytoplasm-free zonae from unfertilized eggs were obtained and used as an assay system to test the effects of exposure to these two ligands. Spermatozoa were inserted into evacuated zonae and their behaviour and binding activity were assessed at regular intervals. The behaviour of spermatozoa exposed to PPS1 and unlabelled spermatozoa injected into unexposed zonae was similar as far as binding was concerned (50 and 54% binding), but PPS1 exposed spermatozoa had higher motility and displacement, marked by their escape from the zona pellucida. Zonae exposed to PPS2 inhibited the interaction between injected spermatozoa and the inside of the zona when compared with controls (8.3 and 53.8% attached respectively, P < 0.001). The sperm-zona pellucida interaction described in this paper is applied as a functional assay for molecular interactions of sperm binding and can be used to assess function for potential surface markers on gametes. It is shown here that a unique binding ligand (PPS2) can be synthesized from another complimentary ligand (PPS1) without the need for a known intermediate substrate. PPS1 and PPS2 may have properties that can be used to target processes involved in conception and assisted reproduction. A movie sequence taken approximately 30 min after injection of spermatozoa into empty human zonae pellucidae shows behaviour of non-manipulated spermatozoa into zonae not exposed or exposed to ligand. This may be purchased for viewing on the Internet at www.rbmonline.com/Article/2159 (free to web subscribers).

Cleavage anomalies in early human embryos and survival after prolonged culture in-vitro

This study examines the relationship between common morphological anomalies of cleaving embryos and their ability to form apparently normal blastocysts in vitro. The impact of cleavage rate, fragmentation, and multinucleation on compaction, cavitation, along with inner cell mass and trophectoderm formation has been assessed. The study population consisted of 102 patients who elected or were selected to have a day 5 embryo transfer. Clinical pregnancy and implantation rates were 66.7 and 49% respectively. Slow and fast cleavage had a significant negative association with normal blastocyst formation. Only 13.8% (67/484) of embryos with <7 cells and 27.5% (25/91) of those with >9 cells on day 3 formed blastocysts with apparently normal morphology, compared to 41.9% (252/602) with 7-9 cells on day 3 (P < 0.001). Fragmentation had a negative impact on normal blastocyst formation. Embryos with >15% fragmentation formed normal blastocysts at a significantly lower rate (46/279; 16.5%) than embryos with 0-15% fragmentation (311/935; 33.3%) (P < 0. 001). Furthermore, the pattern of fragmentation was associated with blastocyst formation. Type IV fragmentation led to a significant reduction in blastocyst formation (25/170 or 14.7%), compared to types I, II and III which performed much better (38.6, 32.9 and 32.4% respectively). Only 15.9% (22/138) of embryos with one or more multinucleate cells on day 2 and/or 3 formed normal blastocysts compared with 31.9% (335/1051) (P < 0.001) of those without multinucleation. Collectively, the data suggest that cleavage anomalies, some of which do not preclude development after short-term culture, may reduce the developmental competence of embryos after prolonged culture.

Sperm deposition site during ICSI affects fertilization and development

OBJECTIVE

To evaluate the effects of sperm placement during ICSI relative to the M-II spindle location on fertilization and preimplantation development.

DESIGN

Retrospective analysis of oocyte fertilization and embryo development with respect to sperm deposition site during ICSI.

SETTING

A program of IVF-ET.

PATIENT(S)

Seven hundred seventy-six patients.

INTERVENTION(S)

Egg quality, sperm deposition site, and polar-body position were recorded during ICSI; fertilization was assessed on day 1; embryo development was evaluated on days 2 and 3.

MAIN OUTCOME MEASURE(S)

Fertilization, embryo development, and implantation rates.

RESULT(S)

Normal fertilization is not affected by polar-body orientation, with the exception of a significantly lower fertilization rate from a 9 o'clock polar-body orientation. Injections with the polar-body positioned at 7 or 11 o'clock result in the greatest number of high-quality embryos, significantly more than the adjacent 6 or 12 o'clock polar-body orientations and irrespective of oocyte anomaly frequency. Embryos originating from the 7 or 11 o'clock polar-body category implant at a higher rate, although the data are not significant.

CONCLUSION(S)

The placement of the sperm during ICSI relative to the presumed location of the meiotic spindle significantly impacts fertilization and high-quality embryo development. Sperm deposition in the M-II spindle area should be avoided. It appears that development, and not fertilization, is improved by decreasing the distance between the sperm cell and the spindle.

The first births and ongoing pregnancies associated with sperm cryopreservation within evacuated egg zonae

This new procedure principally aims to avoid a second or possibly multiple surgical procedures for sperm extraction from the male partner in cases of limited amounts of sperm cells, where normal freeze-thaw protocols would fail. Patients (n = 34) diagnosed as azoospermic, extreme oligozoospermic, or oligoasthenozoospermic underwent the process of sperm cryopreservation within evacuated egg zonae. Other samples were allocated to conventional sperm freezing. Sperm samples were acquired using testicular sperm extraction (TESE), microepididymal sperm aspiration (MESA), or fresh ejaculate. Subsequently, five of these 34 couples have undergone in-vitro fertilization (IVF) and achieved normal fertilization using post-thawed spermatozoa frozen under zonae pellucidae in conjunction with intracytoplasmic sperm injection (ICSI). The average fertilization rate for the post-thaw injected spermatozoa was 65%. This is comparable with the regular fertilization rate of 65% for combined MESA and TESE using fresh spermatozoa. All patients underwent embryo transfer. The average implantation rate per embryo was 31%; nearly the same for regular MESA/TESE ICSI cycles (32%). The first pregnancy associated with this procedure concluded with the full term delivery of healthy twin girls on July 18, 1997. The remaining four thaw procedures resulted in another twin delivery, an ongoing singleton gestation, a negative pregnancy test and a biochemical pregnancy respectively.

Chromosome abnormalities in embryos obtained after conventional in vitro fertilization and intracytoplasmic sperm injection

OBJECTIVE

To compare the rate of numerical chromosome abnormalities in embryos derived from bipronucleated zygotes produced by intracytoplasmic sperm injection (ICSI) and conventional IVF.

DESIGN

Embryos were classified by maternal age and morphological and developmental characteristics to avoid bias when comparing chromosome abnormalities in ICSI and IVF embryos.

SETTING

The Institute for Reproductive Medicine and Science of Saint Barnabas Medical Center, West Orange, New Jersey.

PATIENT(S)

Seventy-nine couples undergoing IVF and 53 couples undergoing ICSI.

INTERVENTION(S)

Embryos donated for research were fully biopsied, and their cells were analyzed by fluorescence in situ hybridization with specific probes for chromosomes X, Y, 13, 18, and 21 and some with also a probe for chromosome 16.

MAIN OUTCOME MEASURE(S)

Embryo chromosome abnormalities.

RESULT(S)

A total of 245 embryos obtained through conventional IVF and 136 embryos obtained through ICSI were analyzed. There were no statistical differences between the rates of numerical chromosomal abnormalities detected in the IVF (61%) and ICSI (52%) embryos analyzed. Regarding gonosomal aneuploidy, the same rate was found in both ICSI (1%) and IVF groups (2%).

CONCLUSION(S)

If the parents are chromosomally normal, the results indicate that, at the embryo level and before any embryo selection has occurred in utero, ICSI does not produce more numerical chromosomal abnormalities than conventional IVF.

Preimplantation genetic diagnosis increases the implantation rate in human in vitro fertilization by avoiding the transfer of chromosomally abnormal embryos

OBJECTIVE

To verify the percentage of chromosomally abnormal preimplantation embryos in patients with a poor prognosis and possibly to increase the chance of implantation by selecting chromosomally normal embryos.

DESIGN

A prospective, randomized, controlled study.

SETTING

In vitro fertilization program at the Reproductive Medicine Unit of the Società Italiana Studi Medicina della Riproduzione, Bologna, Italy.

PATIENT(S)

In a total of 28 stimulated cycles, the maternal age was > or = 38 years and/or the patient had > or = 3 previous IVF failures, factors that indicated a poor prognosis. After consent, 11 patients underwent preimplantation genetic diagnosis for aneuploidy, whereas 17 controls underwent assisted zona hatching.

INTERVENTION(S)

Simultaneous analysis of chromosomes X, Y, 13, 18, and 21 in a blastomere biopsied from day-3 embryos. Chromosomal analysis was performed with fluorescence in situ hybridization. Assisted zona hatching was performed on day-3 embryos from the control-group patients.

MAIN OUTCOME MEASURE(S)

Embryo morphology, results of fluorescence in situ hybridization, clinical pregnancies, and implantation.

RESULT(S)

In the study group, a total of 61 embryos were analyzed by fluorescence in situ hybridization, and 55% were chromosomally abnormal. Embryo transfer with at least one normal embryo was performed in 10 cycles. Four clinical pregnancies resulted, with a 28.0% implantation rate. In the control group, 41 embryos were transferred in 17 cycles after the assisted zona hatching procedure, yielding four clinical pregnancies and an 11.9% implantation rate.

CONCLUSION(S)

Infertile patients classified as having a poor prognosis have a high percentage of chromosomally abnormal embryos. The advantage of selecting and transferring embryos with normal fluorescence in situ hybridization results has an immediate impact on implantation.

Beneficial aspects of co-culture with assisted hatching when applied to multiple-failure in-vitro fertilization patients

A study was conducted on patients who had attempted and failed previous in-vitro fertilization (IVF) procedures an average of 3.8 times following the application of assisted hatching with conventional culture systems. The aim of this investigation was to determine if addition of co-culture methodologies could reduce embryonic abnormalities and thus improve the prognosis for pregnancy. The study population consisted of 123 patients, subdivided into three patient categories. Previous IVF results from conventional culture were used to evaluate any potential benefits derived from the present co-culture application. Following co-culture, the rate of blastomere development was increased and the rate of fragmentation decreased. An increased rate of blastomere development was most noticeable in the patients aged < or = 39 years with no male factor as well as the intracytoplasmic sperm injection (ICSI) subgroup. Similarly, the rate of fragmentation was significantly reduced in the aforementioned subgroups. The most pronounced impact of co-culture was on pregnancy and implantation rates. The overall clinical and ongoing pregnancy rates were 38% (47/123) and 36% (44/123) respectively. The corresponding implantation rate was 17% (72/ 412) as shown by embryonic cardiac activity. The ongoing pregnancy rates in the < or = 39 years no male factor, > or = 40 years no male factor and ICSI no age limit patient subgroups were 41% (21/51), 30% (8/27) and 33% (15/45) respectively. The results indicate that addition of co-culture to the IVF procedure for poor-prognosis patients may be advisable.