The environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin disturbs the establishment and maintenance of cell polarity in preimplantation rat embryos

Estrogens—Origin of Centrosome Defects in Human Cancer?

Estrogens are associated with a variety of diseases and play important roles in tumor development and progression. Centrosome defects are hallmarks of human cancers and contribute to ongoing chromosome missegragation and aneuploidy that manifest in genomic instability and tumor progression. Although several mechanisms underlie the etiology of centrosome aberrations in human cancer, upstream regulators are hardly known. Accumulating experimental and clinical evidence points to an important role of estrogens in deregulating centrosome homeostasis and promoting karyotype instability. Here, we will summarize existing literature of how natural and synthetic estrogens might contribute to structural and numerical centrosome defects, genomic instability and human carcinogenesis.

Birth defects and congenital health risks in children conceived through assisted reproduction technology (ART): a meeting report

PURPOSE

Assisted Reproduction Treatment (ART) is here to stay. This review addresses the parental background of birth defects, before, during and after conception and focuses both on the underlying subfertility and on the question whether ART as a treatment is an additional contributing factor.

METHODS

Searches were performed in Medline and other databases. Summaries were discussed in a Delphi panel set-up by the European Society of Human Reproduction and Embryology (ESHRE).

RESULTS

Several birth defects and adult diseases arise during the earliest stages of ovarian development and oocyte differentiation: this is the case of cleft palate disorders in offspring from female rat exposed to Dioxin during fetal life or the polycystic ovary diseases in female offspring (primates) exposed to elevated androgen concentration during fetal life. Human oocytes and embryos often fail to stop the propagation of aneuploid cells but maintain their ability to repair DNA damages including those introduced by the fertilizing sperm. There is a 29 % increased risk of birth defects in the newborns spontaneously conceived by subfertile couples and the risk is further increased (34 %) when conception is achieved by treating infertlity with ART (Danish IVF Registry). Periconceptional conditions are critical for ART babies: their birth weight is in general smaller (Norvegian Registry) but a more prolonged culture time doubled the number of large babies (Finnish Registry).

CONCLUSION

The long-term developmental effects of ART on child and subsequent health as an adult remains a subject worthy of futher monitoring and investigation.

The aryl hydrocarbon receptor agonist 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) alters early embryonic development in a rat IVF exposure model

Aryl hydrocarbon receptor (AHR) ligands, including 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD), accelerate reproductive senescence and one proposed target is the early embryo. To discriminate between direct effects on the oocyte and early embryo and those mediated by complex ovarian interactions with TCDD, IVF was carried out in the presence of TCDD (10, 100 nM) and the aryl hydrocarbon antagonist CH-223191 (1 μM) combined factorially. TCDD-induced Cyp1a1 mRNA expression was absent in 2-cell embryos; however morulae exhibit dose-dependent Cyp1a1 expression. TCDD induced accumulation of sperm in the perivitelline space and displacement of blastomere nuclei. At 100 nM TCDD, aberrations in cytokinesis and nuclear positioning were observed 2-cell embryos and morula and these effects were reversed in the presence of CH-223191. Our data suggest that acute exposure to TCDD has direct effects on early development in the rat that permit discrimination of AHR-mediated and AHR-independent mechanisms through which environmental toxicants impair mammalian reproduction.