Researchers at Michigan State University believe they may have unraveled some of the mysteries of stem cells: Where embryonic stem cells come from and how cells decide whether to form the placenta or the embryo.
In humans and other mammals, embryos develop inside the mother and receive their blood supply and nutrients through the placenta – the interface between mother and baby. In other animals, everything an embryo needs to develop is found inside the egg.
The formation of the placenta is not due to the mother but the developing embryo. During embryogenesis, cells divide and differentiate, and some go to form the placenta and others form the baby.
The process that determines where those cells go is very important as it is how pluripotent cells are formed. Pluripotent cells form pluripotent stem cells which are capable of developing into any cell in the body. Consequently, they are extremely valuable in research and are used in regenerative medicine.
While scientists have successfully created stem cells in the lab – termed induced pluripotent stem cells (iPSCs) as they involve reprogramming adult cells – there is clearly a gap in understanding of how they are formed> in the lab, the process is only 1% efficient, whereas in the human body it is 100% efficient.
In humans, the embryonic stem cells are created during the first four days of pregnancy. Understanding the process of how that is achieved will help scientists develop stem cells in the lab with greater efficiency.
The researchers believe they have identified two proteins that are involved in the process of pluripotent cell creation and influence whether the cells form the placenta or the baby. While the two proteins – YAP1 and WWTR1 – were believed to play a role in the creation of pluripotent cells in embryos, the method involved was not understood. The research was surprising.
The proteins, which are packaged into eggs by the mother, help to sort cells and determine whether they make the placenta or remain as embryonic cells by making the cells stick to the outside of the embryo.
“We’ve identified a way that cells evade this stickiness, crawl inside the embryo and acquire the properties that make stem cells so interesting and useful,” explained Tristan Frum co-author of the study.
The research is detailed in the paper – HIPPO signaling resolves embryonic cell fate conflicts during establishment of pluripotency in vivo – which was recently published in the journal eLife. DOI: 10.7554/eLife.42298.