The discovery of a gene essential to early embryonic development sheds light on the preliminary stages of human placenta formation. A team led by scientists from the University of California San Diego (CA, USA) has used human pluripotent stem cells to model the early formation of the placenta, potentially furthering our understanding of pregnancy loss, reproductive disorders and placental disease. The trophectoderm is the outermost layer of cells in the blastocyst, the developmental stage that occurs 5–6 days after fertilization. It is the first tissue to differentiate during mammalian development and eventually forms the trophoblast compartment of the placenta. Fundamental to processes including embryo cavitation, implantation and pregnancy initiation, abnormalities in the establishment and differentiation of the trophectoderm during the first phases of placenta formation have been linked to pregnancy loss and placental-associated disorders. However, the mechanisms that underpin this formative step remain poorly defined. While animal models have been used to identify key signaling pathways involved in trophectoderm specification, differences during early development limit the translation of these findings to our own species, necessitating the need for human-specific models. Thus far, these have been hindered by ethical considerations and technical complications. Cradle cultures: growing stem cell-derived developmental cell models in vitro How are three stem cell-derived developmental cell models furthering our understanding of post-implantation human embryo development? And why have recent advancements in these human embryo-like models spurred ethical discussion and the need to refine our definition of ‘embryo’? In the new study, the researchers used human pluripotent stem…
