title: Global DNA methylation levels are altered by modifiable clinical manipulations in assisted reproductive technologies.
abstract: We analyzed placental DNA methylation levels at repeated sequences (LINE1elements) and all CCGG sites (the LUMA assay) to study the effect of modifiable clinical or laboratory procedures involved in in vitro fertilization. We included four potential modifiable factors: oxygen tension during embryo culture, fresh embryo transfer vs frozen embryo transfer, intracytoplasmic sperm injection (ICSI) vs conventional insemination or day 3 embryo transfer vs day 5 embryo transfer.
  
  
  
  Global methylation levels differed between placentas from natural conceptions compared to placentas conceived by IVF. Placentas from embryos cultured at 20% oxygen showed significant differences inLINE1methylation compared to in vivo conceptions, while those from embryos cultured at 5% oxygen, did not have significant differences. In addition, placentas from fresh embryo transfer had significantly differentLINE1methylation compared to placentas from in vivo conceptions, while embryos resulting from frozen embryos were not significantly different from controls. On sex-stratified analysis, only males had significant methylation differences atLINE1elements stratified for the modifiable factors. As expected,LINE1methylation was significantly different between males and females in the control population. However, we did not observe sex-specific differences in the IVF group. We validated this sex-specific observation in an additional cohort and in opposite sex IVF twins.
  
  
  
  We show that two clinically modifiable factors (embryo culture in 5 vs 20% oxygen tension and fresh vs frozen embryo transfer) are associated with global placental methylation differences. Interestingly, males appear more vulnerable to such treatment-related global changes in DNA methylation than do females.
authors.affiliation: Center for Research on Reproduction and Women's Health, University of Pennsylvania School of Medicine, Philadelphia, PA 19104 USA.
authors.forename: Jayashri
authors.initials: J
authors.lastname: Ghosh
authors.affiliation: Center for Research on Reproduction and Women's Health, University of Pennsylvania School of Medicine, Philadelphia, PA 19104 USA.|Department of Obstetrics & Gynecology, University of Pennsylvania School of Medicine, 3701 Market Street, 8th Floor, Philadelphia, PA 19104 USA.
authors.forename: Christos
authors.initials: C
authors.lastname: Coutifaris
authors.affiliation: Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA 19140 USA.|Department of Pathology and Laboratory Medicine, Temple University School of Medicine, Philadelphia, PA 19140 USA.
authors.forename: Carmen
authors.initials: C
authors.lastname: Sapienza
authors.affiliation: Center for Research on Reproduction and Women's Health, University of Pennsylvania School of Medicine, Philadelphia, PA 19104 USA.|Department of Obstetrics & Gynecology, University of Pennsylvania School of Medicine, 3701 Market Street, 8th Floor, Philadelphia, PA 19104 USA.
authors.forename: Monica
authors.identifier: 0000-0003-3306-4791
authors.initials: M
authors.lastname: Mainigi
mesh_terms: D000328:Adult; D019175:DNA Methylation; D046149:Embryo Culture Techniques; D044127:Epigenesis, Genetic; D005260:Female; D006801:Humans; D020084:Long Interspersed Nucleotide Elements; D008297:Male; D010920:Placenta / Q000378:metabolism / Q000502:physiology*; D011247:Pregnancy; D027724:Reproductive Techniques, Assisted
keywords: Fresh transfer; Frozen transfer; IVF; LINE1; Methylation; Modifiable factors; Oxygen tension