Evolutionary justifications for human reproductive limitations

In Vitro Culture of Mammalian Embryos: Is There Room for Improvement?

Preimplantation embryo culture, pivotal in assisted reproductive technology (ART), has lagged in innovation compared to embryo selection advancements. This review examines the persisting gap between in vivo and in vitro embryo development, emphasizing the need for improved culture conditions. While in humans this gap is hardly estimated, animal models, particularly bovines, reveal clear disparities in developmental competence, cryotolerance, pregnancy and live birth rates between in vitro-produced (IVP) and in vivo-derived (IVD) embryos. Molecular analyses unveil distinct differences in morphology, metabolism, and genomic stability, underscoring the need for refining culture conditions for better ART outcomes. To this end, a deeper comprehension of oviduct physiology and embryo transport is crucial for grasping embryo-maternal interactions' mechanisms. Research on autocrine and paracrine factors, and extracellular vesicles in embryo-maternal tract interactions, elucidates vital communication networks for successful implantation and pregnancy. In vitro, confinement, and embryo density are key factors to boost embryo development. Advanced dynamic culture systems mimicking fluid mechanical stimulation in the oviduct, through vibration, tilting, and microfluidic methods, and the use of innovative softer substrates, hold promise for optimizing in vitro embryo development.

Population monitoring of trisomy 21: problems and approaches

Trisomy 21 (Down syndrome) is the most common autosomal aneuploidy among newborns. About 90% result from meiotic nondisjunction during oogenesis, which occurs around conception, when also the most profound epigenetic modifications take place. Thus, maternal meiosis is an error prone process with an extreme sensitivity to endogenous factors, as exemplified by maternal age. This contrasts with the missing acceptance of causal exogenous factors. The proof of an environmental agent is a great challenge, both with respect to ascertainment bias, determination of time and dosage of exposure, as well as registration of the relevant individual health data affecting the birth prevalence. Based on a few exemplary epidemiological studies the feasibility of trisomy 21 monitoring is illustrated. In the nearer future the methodical premises will be clearly improved, both due to the establishment of electronic health registers and to the introduction of non-invasive prenatal tests. Down syndrome is a sentinel phenotype, presumably also with regard to other congenital anomalies. Thus, monitoring of trisomy 21 offers new chances for risk avoidance and preventive measures, but also for basic research concerning identification of relevant genomic variants involved in chromosomal nondisjunction.

Transmission ratio distortion of mutations in the master regulator of centriole biogenesis PLK4

The evolutionary conserved Polo-like kinase 4 (PLK4) is essential for centriole duplication, spindle assembly, and de novo centriole formation. In man, homozygous mutations in PLK4 lead to primary microcephaly, altered PLK4 expression is associated with aneuploidy in human embryos. Here, we report on a consanguineous four-generation family with 8 affected individuals compound heterozygous for a novel missense variant, c.881 T > G, and a deletion of the PLK4 gene. The clinical phenotype of the adult patients is mild compared to individuals with previously described PLK4 mutations. One individual was homozygous for the variant c.881G and phenotypically unaffected. The deletion was inherited by 14 of 16 offspring and thus exhibits transmission ratio distortion (TRD). Moreover, based on the already published families with PLK4 mutations, it could be shown that due to the preferential transmission of the mutant alleles, the number of affected offspring is significantly increased. It is assumed that reduced expression of PLK4 decreases the intrinsically high error rate of the first cell divisions after fertilization, increases the number of viable embryos and thus leads to preferential transmission of the deleted/mutated alleles.

Health Problems and Financial Burdens in Mislabeling IVF Failures as RIF

The Article Abstract is not Available.

The VACTERL association: mosaic mitotic aneuploidy as a cause and a model

While mitotic errors commonly cause aneuploid clones soon after conception, the embryos often normalize as clones are rapidly eliminated. Although generally considered benign, evidence suggests clone elimination as the primary cause of the vertebral, ano-rectal, cardiac, tracheo-esophageal, renal, and limb (VACTERL) association of anomalies, and possibly other adverse outcomes as well. Here, clone elimination-related development disruption at specific locations is used as the basis of a comprehensive theoretical VACTERL association model that also elucidates mitotic mosaic aneuploidy effects. For the association, the model explains random temporal and spatial origins during a limited time frame and overlapping clusters of component anomalies. It supports early developmental effects involving the stage of determination, where the position in a specific morphogen field controls what a cell will become and where it will be located. Developmental properties related to determination also create specific vulnerabilities to the midline and distal defects, the latter explaining exclusively radial and tibial defects with duplications and deficiencies. The model also supports isolated anomalies as part of the association and, for mosaic mitotic aneuploidy, indicates that clone elimination nears completion at the time of lower limb determination. Although mosaic clone elimination may cause other defects, occurrences in different developmental fields separate them from VACTERL anomalies. Clone elimination may also be related to risks for a single umbilical artery and for non-structural adverse pregnancy outcomes such as losses, prematurity, and growth delays, while a paucity of clone lethality in non-humans explains the rarity of the association and of single umbilical arteries in animals.

MTHFR C677T polymorphism is associated with follicle-stimulating hormone levels and controlled ovarian hyperstimulation response: a retrospective study from the clinical database

OBJECTIVE

To evaluate the impact of methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism with clinical data analysis in controlled ovarian hyperstimulation (COH) of infertile women in the Intravenous Infusion Safety Evaluation Center of Hunan Province, People's Republic of China.

DESIGN

Genetic Association Study.

SETTING

Reproductive medicine clinical.

PATIENT(S)

This genetic association study included 722 infertile women who received the standard long treatment protocol with accessible and complete electronic medical records.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The clinical parameters were obtained from the Intravenous Infusion Safety Evaluation center.

RESULT(S)

Basal FSH levels in the TT group were significantly higher than those of the CC group. The FSH levels after down-regulation in the TT group were higher than those of CC/CT genotypes. The TT genotype patients received significantly higher total doses of GnRH agonist and FSH compared with CC/CT genotypes, whereas the total dose of hCG was higher in the CT genotypes compared with the CC/TT genotypes. Further association analysis between hormone levels and COH outcomes indicated significantly negative correlation of basal FSH levels with antral follicle count and number of oocytes as well as the down-regulation FSH levels with the number of metaphase II oocytes and oocytes.

CONCLUSION(S)

The MTHFR C677T polymorphism was associated with high doses of ovarian stimulation medications, as well as higher FSH levels. The negative correlation between FSH levels and the number of oocytes suggested that C677T polymorphism may play a role in the poor prognosis of COH oocytes. This needs to be studied in future prospective studies with longer follow-up.