Scientists have created a novel model of human embryo that mimics the development of blood cells in the first weeks of pregnancy. The model, which is derived from stem cells, could have various applications in medical research and regenerative medicine.
The researchers used a technique called blastoid induction to generate structures that resemble the human blastocyst, the stage of the embryo that implants into the uterus. The blastocyst consists of an outer layer of cells called the trophectoderm, which forms the placenta, and an inner cell mass, which gives rise to the fetus and its supporting tissues.
The scientists combined two types of stem cells: naive pluripotent stem cells, which can become any cell type in the body, and extra-embryonic trophoblast stem cells, which are specific to the trophectoderm. By culturing these cells in a special medium, they were able to induce them to self-organize into blastoid-like structures that had all the features of a natural blastocyst.
What the model revealed
One of the most remarkable findings of the study was that the blastoids contained cells that resembled primitive blood cells, which are the precursors of all the blood cells in the body. These cells were found in the wall of the yolk sac, a structure that provides nutrients and oxygen to the developing embryo.
The presence of blood cells in the blastoids was surprising, because it was previously thought that human blood cell production begins only after the blastocyst implants into the uterus. The researchers confirmed their observation by comparing the blastoids with natural human embryos donated for research. They found that both types of embryos had similar patterns of gene expression and cell markers related to blood cell development.
The discovery of blood cells in the blastoids suggests that human blood cell production starts earlier than previously thought, and that it is influenced by both the inner cell mass and the trophectoderm. This could have implications for understanding the origin and evolution of blood cells, as well as the causes of blood disorders and diseases.
Why the model is useful
The blastoid model of human embryo offers a new way to study the early stages of human development, which are largely inaccessible and poorly understood. The model could help researchers to investigate the molecular and cellular mechanisms that regulate the formation and differentiation of the various cell types and tissues in the embryo.
The model could also have potential applications in regenerative medicine and drug testing. For example, the blastoids could be used as a source of blood cells for transplantation or disease modeling. The blastoids could also be used to screen for drugs that affect the development and function of the placenta, the yolk sac, or the embryo itself.
The researchers emphasize that the blastoids are not identical to natural human embryos, and that they do not have the potential to develop into a fetus. They also follow strict ethical guidelines and regulations for their work, and limit the culture of the blastoids to 14 days, which is the internationally accepted limit for human embryo research.