Does fresh or frozen embryo transfer affect imprinted gene expressions in human term placenta?

Our research aimed to compare the epigenetic alterations between placentae of in vitro fertilization (IVF) patients and spontaneous pregnancies. Additionally, the expression levels of proliferation markers (PCNA, Ki67) and glucose transporter proteins (GLUT1, GLUT3) were assessed in control and IVF placentae to examine the possible consequences of epigenetic alterations on placental development. Control group placentae were obtained from spontaneous pregnancies of healthy women (n = 16). IVF placentae were obtained from fresh (n = 16) and frozen (n = 16) embryo transfer pregnancies. A group of maternal and paternal imprint genes H19, IGF2, IGF2, IGF2R, PHLDA2, PLAGL1, MASH2, GRB10, PEG1, PEG3, and PEG10 were detected by Real-Time PCR. Additionally, PCNA, Ki67, GLUT1, and GLUT3 protein levels were assessed by immunohistochemistry and western blot. In the fresh embryo transfer placenta group (fETP), gene expression of paternal PEG1 and PEG10 was upregulated compared with the control group. Increased gene expression in paternal PEG1 and maternal IGFR2 genes was detected in the frozen embryo transfer placenta group (FET) compared with the control group. Conversely, expression levels of H19 and IGF2 genes were downregulated in the FET group. On the other hand, GLUT3 and PCNA expression was increased in FET group placentae. IVF techniques affect placental imprinted gene expressions which are important for proper placental development. Imprinted genes are differently expressed in fresh ET placentae and frozen ET placentae. In conclusion, these data indicate that altered imprinted gene expression may affect glucose transport and cell proliferation, therefore play an important role in placental development.