Israeli researchers have produced a human embryo in the lab using stem cells, without the use of sperm, eggs or a womb. This research will allow for new perspectives on the first stages of embryonic development.
They have been called embryoids because they are organoids (lookalikes of a sort) that are similar to human embryos, although they are not the product of an encounter between male and female gametes, but rather only of the experimental use of pluripotent, undifferentiated stem cells, taken from adult skin, which can theoretically become any type of mature cell, and which were encouraged to differentiate into specialized foetal cells.
The embryoid was developed by researchers at the Weizmann Institute in Rehovot, Israel, for one very clear purpose: to provide a model suitable for use in studying areas ranging from the very early days of embryonic development to assisted reproductive technologies, possible foetal responses to medications, the growth of tissues for transplant, and any other area involving foetal medicine, but without having to make any use whatsoever of cells derived from human embryos.
As described in the scientific journal Nature, the pluripotent stem cells, once put into a culture (using a protocol that the Israeli researchers have been refining for ten years, based only on specific culture mediums and not on genetic modifications), became something very similar to a 14-day embryo, complete with placenta, yolk sac and chorion (the three layers that protect the foetus) and, thanks to this fact, represent an extremely advanced model of a foetus in the second week of development.
Positive pregnancy test
All of the cells present within the embryoid seem to assume the correct function. For example, they secrete typical pregnancy hormones (if a commercial pregnancy test is used on the liquids secreted by the embryoid, the test result comes back positive). Moreover, the system has no way of developing further, not even if it were to be implanted into a uterus, because it is incapable of forming a structure similar to an organised muscular or skeletal system, and is therefore—the researchers claim—destined to remain permanently at the 14-day stage. At that point, the embryoid contains approximately 2,500 cells and has a diameter of half a millimetre.
Foetal health: a host of unanswered questions
As strange as it may seem, there are still myriad unanswered questions when it comes to the earliest stages of development and, specifically, the first month, which is also the riskiest in terms of foetal health, as well as that during which genetic or tissue abnormalities can originate. Some of these questions could be answered specifically thanks to embryoids, in a way that, until now, has not been possible, due to ethical reasons and practical difficulties. For instance, the researchers have already discovered that, if the embryo is not correctly enveloped in the placenta at day 3 (which corresponds to day 10 of human gestation), its internal structures will not develop properly. Similarly, several studies are to be designed involving drugs, which cannot be tested on live embryos, for clear ethical reasons.
The technique still needs to be optimised, given that, at the moment, only 1% of stem cells treated successfully develop into embryoids, and the effectiveness of the protocol must be improved if we wish for the embryoid to itself become a tool accessible to a large number of laboratories, one that can be produced without too high of a cost in terms of funds or of time.