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Nanotechnology in Stem Cell Regenerative Therapy and Its Applications
Published in Harishkumar Madhyastha, Durgesh Nandini Chauhan, Nanopharmaceuticals in Regenerative Medicine, 2022
ESCs originate from the blastocyst stage and divide the tissue to become derivatives of germ layers, further leading to the formation of all types of cells. Transcription factors such as octamer-binding transcription factor-4 (OCT4)and SRY-related high-mobility group box protein-2 (SOX2) are responsible for the pluripotency and self-renewal nature. The blastocyst forms the inner and outer cell mass; the inner cell mass forms embryos and the external cell mass forms the placenta. Specific conditions are maintained in growing ESC lines to separate the cells from the inner cell layer of trophoblasts and transfer them to a culture dish (Bongso 2006). In 1998, Thomson isolated human ESCs and divided them into more than 200 categories of cells, which is promising for the treatment of various diseases, described in the next session of this chapter.
Genetic Counseling in Assisted Reproductive Technology
Published in Carlos Simón, Carmen Rubio, Handbook of Genetic Diagnostic Technologies in Reproductive Medicine, 2022
One of the most relevant limitations of PGT-A is the accuracy of the test, typically quoted by laboratories at 98%. Results depend on the ploidy of the cells that were biopsied and which serve as a representative sample of the embryo. The cells of the inner cell mass, which will develop to become the fetus, cannot be tested without damage to the embryo. Mosaic embryos are those that have two or more cell lines with different chromosomal counts. Mosaicism in an embryo cannot be excluded, even when the PGT-A technology allows for the detection of mosaicism in the biopsy. Therefore, false-positives and false-negatives are possible.
Implantation and Embryonic Imaging
Published in Mary C. Peavey, Sarah K. Dotters-Katz, Ultrasound of Mouse Fetal Development and Human Correlates, 2021
Mary C. Peavey, Sarah K. Dotters-Katz
Similarly to human ovulation and fertilization, the mouse embryo after ovulation is transported through the fallopian tube, where fertilization with sperm occurs. The fertilized oocyte is known as the zygote, which will continue to divide into an embryo. As the embryo travels through the fallopian tube, it continues to undergo cell division; by the third day, the embryo is approximately eight cells and begins compaction. On its fifth day of growth, the human embryo has developed into a blastocyst and travels to the uterus where it begins the process of implantation and further growth. At this point, as in humans, the blastocyst consists of a discrete inner cell mass, within a spherical cavity lined by the trophectoderm cell layer. These preimplantation events cannot be ascertained via ultrasonographic methods in either the human or mouse. However, the non pregnant uterus, consisting of the myometrium and endometrium can be easily measured via sonographic methods. See Fig. 1.1.
Trophectoderm non-coding RNAs reflect the higher metabolic and more invasive properties of young maternal age blastocysts
Published in Systems Biology in Reproductive Medicine, 2023
Panagiotis Ntostis, Grace Swanson, Georgia Kokkali, David Iles, John Huntriss, Agni Pantou, Maria Tzetis, Konstantinos Pantos, Helen M. Picton, Stephen A. Krawetz, David Miller
The American Society for Reproductive Medicine (ASRM) guidelines indicate that the male (as the sole or contributing factor) causes approximately 40% of all cases of infertility, while female infertility as sole factor, accounts for another 40% (Kumar and Singh 2015; Walker and Tobler 2020), along with various other uncharacterized/undetermined parental factors (Wu H et al. 2017; Colaco and Sakkas 2018). The mammalian blastocyst consists of trophectoderm cells (outer layer) that gives rise to the extra-embryonic tissues including the placenta and the inner cell mass (internal cells or ICM) that ultimately gives rise to the fetus. Hence, the trophectoderm is the first embryonic tissue to communicate directly with the endometrium during a narrow implantation window (Figure 1). Implantation and pregnancy failure may be affected by various factors including a failure of communication and synchronization between the blastocyst and endometrium (Achache and Revel 2006; Margalioth et al. 2006) caused by uterine anomalies (Taylor and Gomel 2008) and/or embryonic factors such as chromosomal aneuploidies (Harper 2018; Cimadomo et al. 2020) and abnormal gene expression (McCallie et al. 2019; Ntostis et al. 2019; Abu-Halima et al. 2020; Ntostis et al. 2021). These deficiencies can be mitigated in part, by ensuring only transfer of euploid blastocyst where implantation rates from 50%-80% are observed (Saravelos and Li 2012).
Preimplantation genetic diagnosis (PGD) and genetic testing for aneuploidy (PGT-A): status and future challenges
Published in Gynecological Endocrinology, 2020
Romualdo Sciorio, Luca Tramontano, James Catt
In the late 1990s, it became standard practice to extend embryo culture up to the blastocyst stage [30]. At this point, the embryo is already differentiated into two distinct cell types: the inner-cell mass (ICM) that will develop and form the fetus, and the trophectoderm (TE) cells which will become the placenta. As mentioned earlier, in recent times, many IVF units have left cleavage stage biopsy, and have turned to TEB as this biopsy offers some advantages. First, 5-10 cells can be biopsied from the blastocyst and this makes the genetic diagnosis more reliable and less prone to errors [31,32]. Second, TEB is believed to have a smaller detrimental effect on embryo viability compared to biopsy on day-3. Finally, TE biopsy reduced the risk of mosaicism [25]. To perform TEB, it is required to make a hole in the ZP either on day-3 or on day-5, and to wait for the beginning of TE herniation, which represents the optimal time to start the biopsy. Recently, the biopsy of blastocoel fluid has been proposed by Palini et al. [33] as new source of embryonic genetic material (Figure 2). With the introduction of vitrification as a highly efficient cryopreservation method, it is possible to combine blastocyst biopsy with vitrification and genetic screening, followed by warming and transfer of euploid embryos in a subsequent cycle [34,35].
Cleavage-stage embryo micromanipulation in the clinical setting
Published in Systems Biology in Reproductive Medicine, 2018
Iman Halvaei, Shahin Ghazali, Stefania A. Nottola, Mohammad Ali Khalili
ZP hatching is a natural process caused by serine proteases released from maternal (uterine cells) or embryonic (trophectoderm cells) sources or/and increasing internal pressure due to blastocyst expansion (Cohen 1991; O’Sullivan et al. 2002; Sathananthan et al. 2003). Normally, the embryo escapes from the ZP 5–6 days after fertilization just before implantation. There are some factors that impair hatching, including abnormality in ZP structure, increase in ZP thickness, and zona hardening. Advanced maternal age, ovarian stimulation protocol, sub-optimal in vitro culture and cryopreservation may induce zona hardening (Aston and Weimer 2010). Assisted hatching (AH), by creating an opening in the ZP, helps the embryo to escape from the ZP. In human embryos, the site of hatching is in close proximity to the blastocyst inner cell mass (Gonzales et al. 1996). Therefore, the site of AH seems important for the initiation of hatching (Miyata et al. 2010). The recommended indications for AH include advanced maternal age (≥40 years), elevated FSH level, thick ZP (>15µm), frozen-thawed embryos, and history of implantation failure (≥2) (Cohen et al. 1992; Schoolcraft et al. 1994; Tao and Tamis 1997; Mansour et al. 2000; Hammadeh et al. 2011). Some AH indications are referred to in vitro culture like zona hardening or lack of produced protease by the embryo (Schiewe et al. 1995). Recently, Razi et al. (2013) in a prospective randomized study evaluated the ART outcomes following laser AH (LAH) in patients undergoing their first ICSI treatment due to male factor infertility. They showed that the clinical pregnancy and the live birth rates were similar between patients with AH and the control group (Razi et al. 2013).