The Joint Annual Scientific Meetings of the Endocrine Society of Australia and the Society for Reproductive Biology 2018

Characterisation of 5-methylcytosine and 5-hydroxymethylcytosine in human placenta cell types across gestation (#148)

Rebecca Wilson 1 2 , Maxime Francois 3 , Tanja Jankovic-Karasoulos 1 2 , Dale McAninch 1 2 , Dylan McCullough 1 2 , Claire Roberts 1 2 , Tina Bianco-Miotto 1 4
  1. Robinson Research Institute, University of Adelaide, Adelaide, SA, Australia
  2. Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
  3. Personalised Nutrition and Healthy Ageing, CSIRO Health and Biosecurity, Adelaide, SA, Australia
  4. Waite Research Institute, School of Agriculture, Food and Wine, University of Adelaide, Adelaide, SA

The placenta is one of the most important organs to human reproduction however, very little is understood about placental development at a molecular level, including how epigenetic mechanisms change throughout gestation. In addition, DNA methylation studies in this organ are complicated by the different cell types that make up the placenta. Placental dysfunction is often associated with pregnancy complications such as preeclampsia (PE), and aberrant DNA methylation in the placenta has been identified in pregnancy complications compared to uncomplicated samples. We used immunohistochemistry (IHC) and immunofluorescence (IF) to investigate the localisation of 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC), in placenta tissue across gestation. IHC analysis of tissue sections showed levels of 5-mC increased across gestation, as expected and previously shown. When specific trophoblast cell subtypes: cytotrophoblasts (CTB) and syncytiotrophoblasts (STB), were isolated and stained using IF, levels of both 5-mC and 5-hmC significantly increased in term CTBs compared to first/second trimester. Staining intensity of 5-hmC also increased in first trimester STBs compared to CTBs (P=0.0011). Finally, comparison of IHC staining in term tissue from PE and uncomplicated pregnancies revealed levels of 5-mC to be higher in placentas from PE pregnancies (P=0.028). Our analysis confirmed that 5-mC and 5-hmC staining intensity increased across gestation, and was different between CTB and STB. This provides a solid foundation for future research focused on single cell populations. Differences in DNA methylation profiles between different cell types of the placenta may be indicative of different functions and requires further study in order to elucidate what changes accompany placental pathologies.