Assisted reproductive technologies (ART) are noncoital methods of conception that are used to treat infertility employing either donor or non-donor eggs and sperm. ART, such as in vitro fertilization (IVF), have resulted in over 9 million births worldwide since 1978 and iIt is expected that the use of ART will continue to increase. However, ART is associated with adverse outcomes including but not limited to low fetal weight, high placental weight, hypertensive disorders such as preeclampsia, and preterm birth.

ART are also associated with a higher risk for imprinting disorders. Genomic imprinting is an epigenetic modification in which one of the parental alleles is controlled by methylation. This involves imprinting control regions (ICRs) that regulate the expression of an imprinted gene. Genomic imprinting leads to imprinting disorders that affect metabolism, growth, and development.

This project studied two specific aims: to examine the differences between natural, IVF, and IVF + TEBx placentas and to determine the effect of 2% versus 5% oxygen environments on in vitro generated blastocysts, both using mouse models. 

The trophectoderm biopsy (TEBx) is an invasive procedure in which several trophectoderm (TE) cells are removed from the blastocyst for genetic testing of the embryonic day 3.5 (E3.5) pre-implantation embryo. Placentas were analyzed from the natural, IVF, and IVF + TEBx for the areas of the junctional zone (maternal/fetal vasculature for nutrient and gas exchange) and labyrinth zone (endocrine function) using H&E and CD34 staining. Based on Fiji analysis from H&E stained placenta images, IVF + TEBx placentas show no difference compared to IVF with respect to junctional and labyrinth areas, but showed a difference with respect to labyrinth areas in the CD34 stained placentas. 

It is suggested that hypoxia might be better for blastocyst development, and that oxygen tension in the uterus is lower at approximately 2% than the oviduct which is around 5%, so IVF 5% and IVF 2% experimental groups were investigated. Studies have reported greater cell cumbers and decreased apoptosis in blastocysts that are cultured at reduced oxygen tensions. We found that 2% oxygen increased blastocyst cell numbers compared to 5%. IVF 2% did not show differences with 5% in terms of fetal weight, placental weight, and the fetal to placental weight ratio. We assessed methylation using LUMA (luminometric methylation assay) and bisulfite pyrosequencing and found that IVF 2% did not prevent the loss of DNA methylation globally or at selected ICRs in the placenta, but partially prevented the loss of DNA methylation at ICRs in fetal tissue. In conclusion, there is some evidence that embryo culture is more advantageous in 2% oxygen.