In vitro Human Embryo Morphology - An Odissey Outside the Oviduct

The authors describe the human embryo development in vitro, during the preimplantation stages, i.e., from the zygote until the blastocyst stage. They also describe the methods to select the most suitable embryo for transfer in cycles of In vitro fertilization treatment, performed by infertile patients, in order to increase implantation and pregnancy rates.

Differential localization of serotoninergic system elements in human amniotic epithelial cells†

Serotonin or 5-hydroxytryptamine (5-HT) is a biogenic amine involved in regulating several functions, including development. However, its impact on human embryo development has been poorly studied. The present work investigated the expression and distribution of the main components of the serotoninergic system in human amniotic tissue and in human amniotic epithelial cells (hAEC) in vitro, as an alternative model of early human embryo development. Amniotic membranes from full-term healthy pregnancies were used. Human amnion tissue or hAEC isolated from the amnion were processed for RT-PCR and immunofluorescence analyses of the main components of the serotoninergic system. We found the expression of tryptophan hydroxylase type 1 (TPH1), type 2 (TPH2), serotonin transporter (SERT), monoamine oxidase-A (MAO-A) as well as HTR1D and HTR7 receptors at mRNA level in amnion tissue as well in hAEC. Interestingly, we found the presence of 5-HT in the nucleus of the cells in amnion tissue, whereas it located in the cytoplasm of isolated hAEC. We detected TPH1, TPH2 and HTR1D receptor in both the nucleus and cytoplasm. SERT, MAO-A and HTR7 receptor were only observed in the cytoplasm. The results presented herein show, for the first time, the presence of the serotoninergic system in human amnion in vivo and in vitro.

MiR-191-5p Is Upregulated in Culture Media of Implanted Human Embryo on Day Three of Development

Background: Morphologic features are the most common criteria for selecting human embryo to be transferred to the receptive uterine cavity. However, such characteristics are not valid for embryos in cellular arrest. The aim of this study was to quantify the expression profile of hsa-miR-21-3p, -24-1-5p, -191-5p, and -372-5p on day 3 of culture media from in vitro fertilization (IVF) embryo that were implanted or failed to be implanted in patients (n=25 pregnant and 25, non-pregnant patients). Methods: Fifty patients were accepted in the Department of Reproductive Biology of a Hospital in México City, based on the Institutional inclusion criteria for in vitro fertilization. On day 3 of development, embryos were transferred to women, and the culture medium was collected from implanted embryos (n=25, pregnant patients) and non-implanted embryos (n=25, non-pregnant). In the culture medium, RNA was isolated using TRIzol reagent. MiRNA expression was detected through RT-PCR with specific primers. Expression bands were quantified using an optic density.Results: The expression profiles were compared between pregnant and non-pregnant patients revealing a significant 5.2-fold greater expression of hsa-miR-191-5p in the former group (p ≤0.001) and a significantly higher expression of hsa-miR-24-1-5p (p =0.043) in the latter. No significant difference was found between the two groups in regard hsa-miR-21-3p or hsa-miR-372-5p (p =0.41). Conclusions: According to the results, has-miR-191-5p could possibly be a possible biomarker of adequate human embryo development. This miRNA modulated IGF2BP-1 and IGF2R, which are associated with the implantation window. On the other hand, hsa-miR-24-1-5p may be related to a poor prognosis of human embryo development.

Parental genome unification is highly erroneous in mammalian embryos

The vast majority of human embryos are aneuploid. Aneuploidy frequently arises during the early mitotic divisions of the embryo, but the origin of this remains elusive. Using bovine embryos as a model for human embryos, we identify an error-prone mechanism of parental genome unification which often results in aneuploidy. Surprisingly, genome unification initiates hours before breakdown of the two pronuclei that encapsulate the parental genomes. While still within intact pronuclei, the parental genomes polarize towards each other, in a process driven by centrosomes, dynein, and microtubules. The maternal and paternal chromosomes eventually cluster at the pronuclear interface, in direct proximity to each other. Parental genome clustering often fails however, leading to massive chromosome segregation errors, incompatible with healthy embryo development. Nucleoli, which associate with chromatin, also cluster at the pronuclear interface in human zygotes. Defects in nucleolar clustering correlate with failure in human embryo development, suggesting a conserved mechanism.