2023-09-07 13:10:07
Scientists have developed an entity that closely resembles an early human embryo, without using sperm, eggs or uterus . The Weizmann Institute team says their “embryo model,” made from stem cells, looks like a textbook example of a real 14-day embryo. It even released hormones that came back positive on a pregnancy test in the lab. The ambition of embryo models is to provide an ethical way of understanding the first moments of our lives. This investigation, published in the journal Nature is described by the Israeli team as the first “complete” embryo model that mimics all the key structures that emerge in the early stages of the embryo.
Instead of a sperm and egg, the starting material was naïve stem cells that were reprogrammed to gain the potential to become any type of tissue in the body. Chemicals were then used to cause these stem cells to become four types of cells found in the early stages of the human embryo: epiblast cells, which become the embryo itself (or fetus); trophoblastic cells, which develop into the placenta; hypoblastic cells, which become the supporting yolk sac; and extraembryonic mesoderm cells. A total of 120 of these cells were mixed in a precise ratio, and then the scientists step back and observe.
About 1% of the mixture began the journey of spontaneously assembling into a structure that resembles, but is not identical to, a human embryo. The embryo models were allowed to grow and develop until they were comparable to an embryo 14 days after fertilization. In many countries, this is the legal limit for normal embryo research. The hope is that embryo models can help scientists explain how different types of cells arise, witness the first steps in the construction of the body’s organs, or understand hereditary or genetic diseases. This study already shows that other parts of the embryo will not form unless the first cells of the placenta can surround it. There is even talk of improving in vitro fertilization (IVF) success rates by helping to understand why some embryos fail or using models to test whether drugs are safe during pregnancy.
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