The first stages of placental development take place days before the embryo starts to form in human pregnancies. The finding highlights the importance of healthy placental development in pregnancy, and could lead to future improvements in fertility treatments such as IVF, and a better understanding of placental-related diseases in pregnancy.
In a study published in the journal Nature, researchers looked at the biological pathways active in human embryos during their first few days of development to understand how cells acquire different fates and functions within the early embryo.
They observed that shortly after fertilization as cells start to divide, some cells start to stick together. This triggers a cascade of molecular events that initiate placental development. A subset of cells change shape, or “polarize’” and this drives the change into a placental progenitor cell–the precursor to a specialized placenta cell–that can be distinguished by differences in genes and proteins from other cells in the embryo.
“This study highlights the critical importance of the placenta for healthy human development,” said Dr. Kathy Niakan, group leader of the Human Embryo and Stem Cell Laboratory at the Francis Crick Institute and Professor of Reproductive Physiology at the University of Cambridge, U.K., and senior author of the study. “If the molecular mechanism we discovered for this first cell decision in humans is not appropriately established, this will have significant negative consequences for the development of the embryo and its ability to successfully implant in the womb.”
Understanding the process of early human development in the womb “could provide us with insights that may lead to improvements in IVF success rates in the future. It could also allow us to understand early placental dysfunctions that can pose a risk to human health later in pregnancy,” Niakan added.