What embryos are we talking about?
About the blastocyst. This is an early stage of development of the mammalian embryo (including
In the evolution of mammals, the blastocyst as a developmental stage arose to ensure implantation, as well as to organize the spatial basis for the formation of the germinal disc in the absence of the yolk.
The blastocyst stage is not homologous to the blastula stage.The blastula stage follows later in mammalian ontogeny (embryonic disc), in the so-called. "The first phase of gastrulation", but traditionally the term "blastula" is not used for mammals and other amniotes. Accordingly, it is a common mistake to use the word "blastocoel" in relation to the blastocyst cavity.
Externally, the blastocyst is a ball,consisting of several tens or hundreds of cells. The size of the blastocyst ranges from fractions of a millimeter (0.1 mm in rodents and humans) to several millimeters (in equids).
The blastocyst consists of two cell populations: the trophoblast (trophectoderm) and the embryoblast (inner cell mass). The trophoblast forms the outer layer of the embryo - a hollow ball or vesicle.
The embryoblast forms the inner layer of the blastocyst and is located inside the trophoblastatic vesicle in the form of a cluster of cells at one of the poles of the ball (inner cell mass).
Trophoblast is involved in implantation (attachmentembryo to the uterine epithelium, invasion into the endometrium of the uterus, immunosuppressive effect, destruction of blood vessels), as well as in the formation of the ectoderm of the chorionic villi (ectodermal part of the placenta).
The embryoblast gives rise to the body of the fetus itself, as well as the mesodermal and endodermal structures of the extraembryonic organs (yolk sac, allantois, amnion, mesodermal part of the chorion).
Parthenogenesis
Typically, embryos are grown in laboratory conditions from donor fertilized eggs. In case of cloning, sperm can be discarded.
Since the mid-tenths, it became clearthat it is possible to grow embryos in a test tube without the participation of germ cells at all. The blastocyst consists of three types of cells, from which the tissues of the fetus, the placenta and the yolk sac are then formed. And they get it all from stem cells.
At the beginning of 2000 it was shown that by processingin vitrooocytes of mammals (rats, macaques, and thenhuman) or by preventing the separation of the second polar body during meiosis, it is possible to induce parthenogenesis, while in culture development can be brought to the blastocyst stage.
Thus obtained human blastocysts are potentially a source of pluripotent stem cells that can be used in cell therapy.
In 2004 in Japan, the fusion of two haploidoocytes taken from different mice, it was possible to create a viable diploid cell, the division of which led to the formation of a viable embryo, which, having passed the blastocyst stage, developed into a viable adult.
It is assumed that this experiment confirms the participation of genomic imprinting in the death of embryos formed from oocytes obtained from one individual at the blastocystal stage.
Stem cell pregnancy
Researchers at Utrecht University have createdmouse embryo from stem cells of two types - embryonic and trophoblastic. The blastocyst grown by them has formed all types of cells necessary for further development.
Moreover, when implanted into the uterus of an animalthe blastocyst caused pregnancy. True, the authors of the work emphasized that they did not get a completely real embryo and therefore the female could not bear it and give birth.
In 2019, scientists from the Institute of BiologicalSalk's research also initiated pregnancy in mice by transplanting embryos obtained from just one somatic cell. It was taken from the body of an adult animal, reprogrammed and propagated - thus the culture of embryonic stem cells appeared.
Then they were reprogrammed again, turning them intoso-called improved pluripotent cells, and were treated with a cocktail of special signaling substances - those that, during natural embryonic development, cause differentiation of the trophoblast (from which the placenta is formed) and the inner cell mass (from which the tissues of the embryo are formed).
As a result, in 15% of cases, blastoids grew from them - structures similar to blastocysts in cellular composition and gene expression.
Human embryo status
Question about the status of the human embryoconsidered, among other things, within the framework of bioethics. Of key importance in such consideration is the recognition or non-recognition of the “human” content of the embryo.
At the moment, the status of the embryo in Russianlegislation is not entirely clear, since it is difficult “to answer the question of whether the law perceives the idea of the existence of an embryo as a subject of legal relations.”
In particular, the law “On Transplantation of Human Organs and (or) Tissues” considers embryos askind of human organs, although its effect on embryos does not apply. Further, there is the notion that it is impossible to consider the embryo a human, "since it does not have legal capacity."
At the same time, legal thought recognizes that an embryo cannot be classified as a human organ, since it is a new organism with its own organs.
The fact that “the embryo containsall the basics of life. " Thus, the situation should be recognized as difficult due to the duality of the legal nature of embryos, which creates serious legal problems, because "the question arises as to whether the embryo can be an object of legal relations."
- Ownership of embryos
Embryos become the subject of propertydisputes in various countries, including the United States. The so-called Davis case (heard in 1989 in the state of Tennessee) is very well known, when in the process of dividing the property of divorcing spouses, the question of rights to previously frozen embryos arose.
As a result, the court transferred the embryos to the mother in temporarypossession for implantation purposes. In addition, the court found that human life begins from the moment of conception and that for this reason the embryo is not an object of property rights.
However, in another case heard inNew York in 1995, the embryos were transferred to the property of his ex-wife. There is also a known case when spouses demanded that an embryo that they had previously transferred for research be removed from the laboratory.
As a result, the court demanded that the embryo be transferred to the spouses, without, however, discovering the existence of ownership and confirming "that the human embryo is not an object of ownership."
Thus, American legal thought inIn principle, I am ready to recognize the embryo as an object of legal relations, but this object is very specific: as a rule, the courts do not recognize the ownership of the embryos, since the latter are the beginning of a new human life.
- Embryo rights
In discussions about acceptability or unacceptabilityof certain manipulations with embryos, the concept of embryo rights occupies an important place. In particular, the prohibition on the use of an embryo or embryonic tissue for medical research is based on the recognition of such rights.
Their defenders, supporters of the so-calledThe “conservative position” refers to the fact that from the moment of conception human life is sacred and inviolable, and also argues that the embryo has all human rights.
Supporters of the so-called "liberal position", even at the very late stages of pregnancy, refuse to recognize the independent status of the fetus, and the decision of its fate is left to the mother or doctors.
Natural inalienable human rightsinclude, inter alia, the right to life. The question of what is the moment of emergence of the right to life, from which legal personality begins, is extremely important for criminal and civil law and for jurisprudence in general.
There is a view according to whichthe legal status of the embryo should be determined on the basis of the fact that the embryo is the beginning of a new life, and not part of the human body. Supporters of this position proceed from the fact that man as a new creature (biological individual) occurs immediately after the fusion of the parental germ cells.
Why grow embryos?
In order to get around the rather harsh rules,directly prohibiting the creation of human embryos for research purposes. And without this, it is impossible to figure out what actually happens in the early stages of development.
It is likely that society as a whole willresearch on such models is more tolerant than experiments on real embryos, researchers at the University of Michigan (USA) say in the Nature editorial. So far, the main ethical question that needs to be addressed is whether the 14-day rule applies to them.
Today, human embryos obtainedexperimentally, destroyed 14 days after fertilization. In some countries, violation of this norm is punishable by law, in others - experiments with such embryos reject ethical committees and deprive them of funding.
If the ban is lifted in relation to blastoids, thenscientists will probably be able to understand not only the causes of miscarriages and IVF failures, but also to find out the mechanisms of a number of hereditary pathologies, including cardiovascular diseases and some types of diabetes.
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