Distinction Between Paternal and Maternal Contributions to the Tripronucleus in Human Zygotes Obtained after In Vitro Fertilization

Abnormally cleaving embryos are able to produce live births: a time-lapse study

PURPOSE

This study investigated the prevalence of abnormally cleaved embryos and determined which types of abnormally cleaved embryos (1-3c, 2-4c, 3-5c, 4-6c), might be suitable for transfer based on live birth data.

METHODS

One hundred seventy-one women (whose transferred embryos were confirmed to be either fully implanted or fully unimplanted) provided 1256 embryos, which were analyzed.

RESULTS

Of these embryos, 320 embryos were transferred, of these transferred embryos, 291 embryos were normal and 29 embryos were abnormal, which five embryos were not analyzed because each one was presented one abnormal cleavage type. These 24 embryos were divided into four groups. Inclusion criteria were as follows: women under 37 years of age undergoing first fresh in vitro fertilization (IVF) treatment with a basal antral follicle count of 5-15, body mass index (BMI) of 18-25 kg/m(2), number of retrieved oocytes between 5 and 20, and tubal factors as the cause of infertility. Time-lapse imaging analysis software was used to compare temporal parameters of normal cleavage and abnormal cleavage groups (there were four abnormal groups, based on the prevalence of abnormal cleavage embryos). Cleavage times were analyzed before the abnormal cleavage occurred, and time intervals were analyzed after the abnormal cleavage based upon the types of abnormal cleavage. In addition, the time intervals of t4-t3 and t8-t5 were also analyzed; corresponding time parameters were measured in the normal group as well. Implantation rate, clinical pregnancy rate, ongoing pregnancy rate, and live birth rate were also measured in the normally cleaved and abnormally cleaved embryos. The prevalence of abnormal cleavage was 15.92% (200/1256). T8-t5 was the most important parameter in the prediction of potential development (production of a live-born baby) of abnormally cleaving embryos.

CONCLUSIONS

Abnormally cleaving embryos were able to produced live births with T8-t5 the best parameter to predict the developmental potential of abnormally cleaving embryos.

The parental origin correlates with the karyotype of human embryos developing from tripronuclear zygotes

Objective

It has previously been suggested that embryos developing from intracytoplasmic sperm-injected (ICSI) zygotes with three pronuclei (3PN) are endowed with a mechanism for self-correction of triploidy to diploidy. 3PN are also observed in zygotes after conventional in vitro fertilization (IVF). The parental origin, however, differs between the two fertilization methods. Whereas the vast majority of 3PN IVF zygotes are of dispermic origin and thus more likely to have two centrioles, the 3PN ICSI zygotes are digynic in origin and therefore, more likely to have one centriole. In the present study, we examine whether the parental origin of 3PN embryos correlates with the karyotype.

Methods

The karyotype of each nucleus was estimated using four sequential fluorescence in situ hybridizations-each with two probes-resulting in quantitative information of 8 different chromosomes. The karyotypes were then compared and correlated to the parental origin.

Results

3PN ICSI embryos displayed a significantly larger and more coordinated reduction from the assumed initial 3 sets of chromosomes than 3PN IVF embryos.

Conclusion

The differences in the parental origin-and hence the number of centrioles-between the 3PN IVF and the 3PN ICSI zygotes are likely to be the cause of the differences in karyotypes.

Tripolar mitosis in human cells and embryos: occurrence, pathophysiology and medical implications

Tripolar mitosis is a specific case of cell division driven by typical molecular mechanisms of mitosis, but resulting in three daughter cells instead of the usual count of two. Other variants of multipolar mitosis show even more mitotic poles and are relatively rare. In nature, this phenomenon was frequently observed or suspected in multiple common cancers, infected cells, the placenta, and in early human embryos with impaired pregnancy-yielding potential. Artificial causes include radiation and various toxins. Here we combine several pieces of the most recent evidence for the existence of different types of multipolar mitosis in preimplantation embryos together with a detailed review of the literature. The related molecular and cellular mechanisms are discussed, including the regulation of centriole duplication, mitotic spindle biology, centromere functions, cell cycle checkpoints, mitotic autocorrection mechanisms, and the related complicating factors in healthy and affected cells, including post-mitotic cell-cell fusion often associated with multipolar cell division. Clinical relevance for oncology and embryo selection in assisted reproduction is also briefly discussed in this context.

Altered cleavage patterns in human tripronuclear embryos and their association to fertilization method: a time-lapse study

PURPOSE

To analyze the cleavage patterns in dipronuclear (2PN) and tripronuclear (3PN) embryos in relation to fertilization method.

METHOD

Time-lapse analysis.

RESULTS

Compared to 2PN, more 3PN IVF embryos displayed early cleavage into 3 cells (p < 0.001), displayed longer duration of the 3-cell stage (p < 0.001), and arrested development from the compaction stage and onwards (p < 0.001). For the IVF embryos, the 2nd and 3rd cleavage cycles were completed within the expected time frame. However, timing of the cell divisions within the cleavage cycles differed between the two groups. In contrast, the completion of the 1st, 2nd, and 3rd cleavage cycle was delayed, but with a similar division pattern for 3PN ICSI compared with the 2PN ICSI embryos. 3PN, more often than 2PN ICSI embryos, displayed early cleavage into 3 cells (p = 0.03) and arrested development from the compaction stage and onwards (p = 0.001). More 3PN IVF than ICSI embryos displayed early cleavage into 3 cells (p < 0.001).

CONCLUSIONS

This study reports differences in cleavage patterns between 2PN and 3PN embryos and for the first time demonstrates differences in the cleavage pattern between 3PN IVF and ICSI embryos.

Human chorionic gonadotropin (hCG) in the secretome of cultured embryos: hyperglycosylated hCG and hCG-free beta subunit are potential markers for infertility management and treatment

Human chorionic gonadotropin (hCG) is produced by trophoblast cells throughout pregnancy, and gene expression studies have indicated that hCG-beta subunit (hCGβ) expression is active at the 2 blastomere stage. Here, we investigated the qualitative hCG output of developing embryos in culture and hCG isoforms expressed in the secretome as a novel sensitive method for detecting hCG. Culture media was collected from the culture plates of 118 embryos in culture (including controls and embryos at different stages of culture) from 16 patients undergoing routine fertility treatment. The hCGβ was detectable in media from 2 pronuclear (2PN) stage embryos through to the blastocyst stage. The hCGβ was absent in 1PN and arrested embryos as well as all media controls. Prior to hatching, hyperglycosylated hCG (hCGh) was observed selectively in 3PN embryos, but after hatching, along with hCG, became the dominant hCG molecule observed. We have reported at the 2PN stage the earliest evidence of hCGβ expression in embryos. There is a suggestion this may be indicative of quality in early embryos, and hCGh seen at the pronuclear stage may suggest triploid abnormality. The dominance of hCG, and hCGh expression, seen after blastocyst hatching may be indicative of potential implantation success. Thus, hCG isoforms have potential roles as biomarkers of embryo viability for embryo/blastocyst transfer.