Scientists get a first look at a key stage of human embryo development | La Vanguardia
The decisive stage of human development that occurs after the embryo is implanted in the uterus has now been studied for the first time thanks to a technical advance developed by scientists in the UK and US.
This advance, presented this week in the journals Nature and Nature Cell Biology, opens the door to a better understanding of how the human body is formed, which will allow to study why some pregnancies end in miscarriage, to improve assisted reproduction techniques, and, in what may be the most important practical application of the new technique, to grow tissues from stem cells for use in future regenerative medicine treatments.
However these promising applications open a new bioethical debate, as they will not see the light of day unless the current ban on research on human embryos over 14 days old is lifted. Once the technical challenge of handling two week-old embryos was solved, the first voices demanding that this rule be reviewed began to emerge.
Previous research on the development of human embryos had been limited to the first week after fertilisation, a period during which the embryo grows to about 0.2 millimetres in diameter and 250 cells, but is not yet implanted in the uterine wall.
Once implanted, on the seventh day after fertilisation, its survival requires a suitable environment which had never been simulated in a laboratory until now. A research team at the University of Cambridge (UK) and another from the Rockefeller University in New York (USA) have overcome this obstacle by bathing embryos in a solution containing molecules that favour their development. In addition, they are provided with a substrate inspired by the uterine wall to implant into. With this support, embryos were able to thrive for another week before being destroyed by the research team so as not to violate the fourteen day limit.
The first results have revealed some unexpected surprises, the biggest of which was the ability of the different types of human embryonic cells to self-organise in the first two weeks after fertilisation. This discovery breaks with the previously accepted concept that embryos depend on environmental signals which originate from the mother in order to develop.
A second unexpected finding was that there are significant differences between the development of human vs. mouse embryos, mice being among the animals most widely used in biomedical research labs. It had previously been assumed that since both are mammals, the two would develop in a similar manner, but the new research suggests that the early stages of our development cannot be understood without studying human embryos.
"This part of human development remains completely unknown", says Anna Veiga, Reproductive Medicine specialist at Center of Regenerative Medicine in Barcelona and Dexeus Women's Health-Quirónsalud Group. "A breakthrough shedding light on what happens at this stage could be very useful".