title: Differences in gene expression profiles between human preimplantation embryos cultured in two different IVF culture media.
abstract: OBJECTIVE
  Is gene expression in human preimplantation embryos affected by the medium used for embryo culture in vitro during an IVF treatment?
  
  
  CONCLUSIONS
  Six days of in vitro culture of human preimplantation embryos resulted in medium-dependent differences in expression level of genes involved in apoptosis, protein degradation, metabolism and cell-cycle regulation.
  
  
  BACKGROUND
  Several human studies have shown an effect of culture medium on embryo development, pregnancy outcome and birthweight. However, the underlying mechanisms in human embryos are still unknown. In animal models of human development, it has been demonstrated that culture of preimplantation embryos in vitro affects gene expression. In humans, it has been found that culture medium affects gene expression of cryopreserved embryos that, after thawing, were cultured in two different media for 2 more days.
  
  
  METHODS
  In a multicenter trial, women were randomly assigned to two culture medium groups [G5 and human tubal fluid (HTF)]. Data on embryonic development were collected for all embryos. In one center, embryos originating from two pronuclei (2PN) zygotes that were not selected for transfer or cryopreservation on Day 2 or 3 because of lower morphological quality, were cultured until Day 6 and used in this study, if couples consented.
  
  
  METHODS
  Ten blastocysts each from the G5 and HTF study groups, matched for fertilization method, maternal age and blastocyst quality, were selected and their mRNA was isolated and amplified. Embryos were examined individually for genome-wide gene expression using Agilent microarrays and PathVisio was used to identify the pathways that showed a culture medium-dependent activity.
  
  
  RESULTS
  Expression of 951 genes differed significantly (P < 0.01) between the G5 and HTF groups. Eighteen pathways, involved in apoptosis, metabolism, protein processing and cell-cycle regulation, showed a significant overrepresentation of differentially expressed genes. The DNA replication, G1 to S cell-cycle control and oxidative phosphorylation pathways were up-regulated in the G5 group compared with the HTF group. This is in agreement with the morphological assessment of the 1527 embryos (originating from 2PN zygotes), which showed that embryos consisted of more cells on Day 2 (3.73 ± 1.30 versus 3.40 ± 1.35, P < 0.001) and Day 3 (7.00 ± 2.41 versus 5.84 ± 2.36, P < 0.001) in the G5 group when compared with the HTF group. Furthermore, the implantation rate was significantly higher in the G5 group compared with the HTF group (26.7% versus 14.7%, P = 0.002) after transfer on the second or the third day after fertilization.
  
  
  CONCLUSIONS
  Despite careful matching of the embryos, it cannot be excluded that the differences observed between the study groups are caused by factors that we did not investigate. Extrapolation of these results to embryos used for transfer demands caution as in the present study embryos that were not selected for either embryo transfer or cryopreservation have been used for the culture experiment until Day 6.
  
  
  CONCLUSIONS
  This study shows that gene expression in human preimplantation embryos is altered by the culture medium used during IVF treatment and provides insight into the biological pathways that are affected. Whether these changes in gene expression have any long-term effects on children born after IVF remains unknown. However, it is possible that early adaptations of the preimplantation embryo to its environment persist during fetal and post-natal development.
  
  
  BACKGROUND
  No funding and no competing interests declared.
  
  
  BACKGROUND
  Not applicable.
authors.affiliation: Department of Obstetrics & Gynaecology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Sander H M
authors.initials: SH
authors.lastname: Kleijkers
authors.affiliation: Department of Bioinformatics-BiGCaT, Maastricht University, Maastricht, The Netherlands.
authors.forename: Lars M T
authors.initials: LM
authors.lastname: Eijssen
authors.affiliation: Department of Obstetrics & Gynaecology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Edith
authors.initials: E
authors.lastname: Coonen
authors.affiliation: Department of Obstetrics & Gynaecology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Josien G
authors.initials: JG
authors.lastname: Derhaag
authors.affiliation: Center for Reproductive Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands MicroArray Department and Integrative Bioinformatics Unit (MAD-IBU), Swammerdam Institute for Life Sciences, Faculty of Science (FNWI), University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Eleni
authors.initials: E
authors.lastname: Mantikou
authors.affiliation: MicroArray Department and Integrative Bioinformatics Unit (MAD-IBU), Swammerdam Institute for Life Sciences, Faculty of Science (FNWI), University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Martijs J
authors.initials: MJ
authors.lastname: Jonker
authors.affiliation: Center for Reproductive Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Sebastiaan
authors.initials: S
authors.lastname: Mastenbroek
authors.affiliation: Center for Reproductive Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Sjoerd
authors.initials: S
authors.lastname: Repping
authors.affiliation: Department of Obstetrics & Gynaecology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Johannes L H
authors.initials: JL
authors.lastname: Evers
authors.affiliation: Department of Obstetrics & Gynaecology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: John C M
authors.initials: JC
authors.lastname: Dumoulin
authors.affiliation: Department of Obstetrics & Gynaecology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands aafke.van.montfoort@mumc.nl.
authors.forename: Aafke P A
authors.initials: AP
authors.lastname: van Montfoort
mesh_terms: D000328:Adult; D000818:Animals; D017209:Apoptosis; D001755:Blastocyst / Q000166:cytology*; D002453:Cell Cycle; D015925:Cryopreservation; D003470:Culture Media / Q000737:chemistry*; D046149:Embryo Culture Techniques; D010064:Embryo Implantation; D004624:Embryo Transfer / Q000379:methods; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D011247:Pregnancy; D011256:Pregnancy Outcome; D059467:Transcriptome
chemical_list: D003470:Culture Media
keywords: IVF/ICSI; culture medium; gene expression; human; preimplantation embryos