Shape of the first mitotic spindles impacts multinucleation in human embryos.

During human embryonic development, early cleavage-stage embryos are more susceptible to errors. Studies have shown that many problems occur during the first mitosis, such as direct cleavage, chromosome segregation errors, and multinucleation. However, the mechanisms whereby these errors occur during the first mitosis in human embryos remain unknown. To clarify this aspect, in the present study, we image discarded living human two-pronuclear stage zygotes using fluorescent labeling and confocal microscopy without microinjection of DNA or mRNA and investigate the association between spindle shape and nuclear abnormality during the first mitosis. We observe that the first mitotic spindles vary, and low-aspect-ratio-shaped spindles tend to lead to the formation of multiple nuclei at the 2-cell stage. Moreover, we observe defocusing poles in many of the first mitotic spindles, which are strongly associated with multinucleation. Additionally, we show that differences in the positions of the centrosomes cause spindle abnormality in the first mitosis. Furthermore, many multinuclei are modified to form mononuclei after the second mitosis because the occurrence of pole defocusing is firmly reduced. Our study will contribute markedly to research on the occurrence of mitotic errors during the early cleavage of human embryos.

An approach for live imaging of first cleavage in mouse embryos using fluorescent chemical probes for DNA, microtubules, and microfilaments.

Purpose: Dynamic morphological changes in the chromosome and cytoskeleton occur in mammals and humans during early embryonic development, and abnormalities such as embryonic chromosomal aneuploidy occur when development does not proceed normally. Visualization of the intracellular organelles and cytoskeleton allows elucidation of the development of early mammalian embryos. The behavior of the DNA and cytoskeleton in early mammalian embryos has conventionally been observed by injecting target molecule mRNAs, incorporating a fluorescent substance-expressing gene, into embryos. In this study, we visualized the chronological behavior of male and female chromosome condensation in mouse embryos, beginning in the two-pronuclear zygote, through the first division to the two-cell stage, using fluorescent chemical probes to visualize the behavior of DNA, microtubules, and microfilaments. Method: Mouse two-pronuclear stage embryo were immersed in medium containing fluorescent chemical probes to visualize DNA, microtubules, and microfilaments. Observation was performed with a confocal microscope. Results: This method allowed us to observe how chromosome segregation errors in first somatic cell divisions in mouse embryos and enabled dynamic analysis of a phenomenon called lagging chromosomes. Conclusions: By applying this method, we can observe any stage of embryonic development, which may provide new insights into embryonic development in other mammals.

A Case of Placenta Accreta Infection Managed by Hysterectomy After Treatment for Retained Products of Conception With Uterine Artery Embolization and Hysteroscopy.

Retained products of conception (RPOC) are frequently associated with previous cesarean section (C-section), abortion, and intrauterine operations, which may affect subsequent pregnancies. A 38-year-old female had a history of C-section and two abortions. After the second abortion, she underwent evacuation of RPOC and was treated with uterine artery embolization (UAE) and hysteroscopic resection. She became pregnant again and vaginally delivered an infant at full term. After delivery, RPOC was suspected on magnetic resonance imaging (MRI), but the patient was discharged for follow-up. She was rehospitalized with a diagnosis of infection and a placental remnant. Antibiotics did not improve the infection; therefore, she underwent a total hysterectomy. After the operation, signs of infection rapidly improved. The pathological diagnosis was placenta accreta. This case was considered a high-risk group for RPOC. In such rare and complicated cases, it is important to consider the possibility of recurrent RPOC and provide sufficient explanations before delivery for subsequent intensive management.