Hybrid or chimera?
Stanislav Lem, "The Star Diaries of Iyon the Quiet"On Thursday, October 23, news agencies and television reported that the British Parliament had allowed scientists to create hybrid embryos.
Later, news outlets began to clarify that the bill was approved only by the lower house and it has yet to pass through the upper one. In addition, various sources differ in determining what was allowed. Let's try to understand this issue.
The beginning of today's events was laid back in 1990, when the British Parliament adopted the Act on Human Fertilization and Embryological Development (Human Fertilization and Embryology Act). In particular, it was prescribed that researchers cannot replace cells or nuclei of human embryos with cells or nuclei of other organisms. Embryos consisting of a mixture of cells obtained from various organisms, or embryos whose cells contain "alien" nuclei, are called hybrid.
Choose who you want
For 18 years, science has made significant progress. One of the most "fashionable" objects to study was the stem cell. Despite the fact that stem and "ordinary" cells contain the same genetic material, their properties are very different.
The main feature of stem cells is their dedifferentiation. This difficult-to-pronounce term means that stem cells do not have a certain "specialization". That is, they are not "sharpened" to perform specific functions. Skin cells and corneal cells of the eye are "busy" with different things, they have different genes and even look completely different. Before becoming "specialists", cells go through a long way of dividing.
The "parent" of all cells is the fertilized egg (after the nucleus of the egg merges with the nucleus of the sperm, it gets the name zygote). The zygote begins to divide, and a cellular "lump" forms in place of one cell. The cells forming it do not have a specific specialization: under certain conditions, they can turn into liver cells, heart cells or cells of the immune system. Over time, the fate of the descendants of the first cells becomes more certain: that is, cells can "choose" not from all organs and tissues of the body, but only from some.
The cells formed during the very first divisions were called totipotent (they can become all cells of the body), at later stages pluripotent and multipotent cells are formed (they can become some cells of the body). Eventually, almost all the cells of the embryo become specialized. Those cells that can "choose" several options for further development are called stem cells. Embryonic stem cells originate from a small group of cells called the internal cell mass of the embryo at the blastocyst stage (photo from the website iscr.ed.ac.uk ).
Millions of dollars have been spent (and continue to be spent) on studying the remarkable properties of stem cells. Scientists can be understood. Many serious human diseases are caused by the loss of certain types of cells. These include, for example, neurodegenerative diseases such as Parkinson's disease. Theoretically, those suffering from such ailments can be cured by planting stem cells that will divide and replace the lost cells. In addition, whole organs can be grown from stem cells (again, theoretically). Transplantation of human organs grown from his own cells would solve the problem of rejection.
But to achieve all these excellent results, there is still a lot to learn about the properties of stem cells. The question arises where to get them. Obviously, the younger the body, the more stem cells there are in it. That is, the optimal source is embryos a few days or weeks after fertilization of the egg. But human embryos have several disadvantages: firstly, it is impossible to collect the necessary amount of material to conduct full-fledged research, and secondly, the use of embryos in many countries is prohibited for ethical reasons.
Hybrids rush to the rescueThat's where scientists needed hybrid embryos, also known as chimeras or hybrids.
They are divided into several types, one of which is called cytoplasmic hybrids. Such embryos are obtained when its own nucleus is removed from the mammalian egg and placed in the "vacant" place of the human cell nucleus. And not stem, but any. The properties of stem cells are determined not by their DNA (since its sequence does not differ from the DNA sequence of all other cells of this organism), but by the cytoplasm (the internal environment of the cell surrounding the nucleus). Therefore, the nucleus of an "ordinary" cell, once in an "unusual" environment, begins to behave like the nucleus of a stem cell.
The resulting hybrid embryo produces stem cells that differ in nothing (or rather, almost nothing) from the stem cells of human embryos. The stem cells of hybrid embryos still contain a small admixture of animal DNA. The fact is that organelles containing DNA are present in the cytoplasm. They are called mitochondria and supply the cell with energy. Mitochondria are able to divide independently and are transmitted from cell to cell. However, this difference does not affect the suitability of hybrid embryonic stem cells for research, but there are significantly fewer ethical issues.
(In addition to cytoplasmic, there are two other types of hybrid embryos: chimeras and "true" hybrids. Chimeras are commonly called embryos obtained by adding one type of cell to another to the embryo. "True" hybrid embryos develop from animal eggs fertilized by spermatozoa of another closely related species. Obtaining true hybrids of humans and animals, even great apes, seems to be fundamentally impossible.)
What happened in the British Parliament
On Wednesday, the House of Commons of the British Parliament in the third reading approved amendments to the Act on Fertilization and Embryological Development of Man, in particular, allowing the creation of cytoplasmic hybrids and work with them for no more than 14 days. After the expiration of this period, the embryo must be destroyed. The creation of other types of embryos is still prohibited. The original version of the bill banned any hybrids.
The discussion of this (and several more) amendments has been going on for a long time. For the first time, the Bill on Human Fertilization and Embryological Development, which was supposed to "adjust" the 1990 Act to the current situation, was submitted to the House of Lords for consideration on November 8, 2007. The decision itself to revise the norms of the Act was made in 2004. The bill was considered in the upper house of the British Parliament in three readings, plus parliamentarians discussed it several times during special sessions. In total, the debate on the bill was held in the House of Lords eleven times.
After that, the House of Commons "took up" the bill. There it was also discussed more than once and finally came to a consensus. At the next stage, the bill will be alternately debated in both chambers (a process known as "ping pong"). If this stage is successfully completed, the bill will go to Her Majesty, after which it will become an official law. According to optimistic forecasts, this should happen in November 2008.
Most likely, this will happen. Stem cells are a very powerful tool for the treatment of many diseases. In addition, they can help children born with serious disabilities to lead a normal life. Doctors will be able to "correct" the child by creating his sister or brother "saviour siblings" – that is, embryos created using the cells of a sick child. Hybrid stem cells can help in the cure of the disease.
In 2007, in the midst of debates in Parliament, the Human Fertilization and Embryology Authority (HFEA), which issues licenses for work with embryonic stem cells, stated that the creation of hybrids for medical purposes is fundamentally allowed. Moreover, the organization has even issued two licenses to conduct such research. In the event that the Parliament decides not to approve the new bill, HEFA will find itself in an unclear position from a legal point of view.
If the bill is approved, the UK will join the few countries where research using embryonic stem cells is allowed. Unofficially, they are already being held. This branch of science has a lot of opponents who claim that permission to create hybrids will allow scientists to create monstrous beastmen or do something else terrible. In addition, such studies cause criticism from the church.
However, it is unlikely that in the history of science there will be any truly revolutionary discovery that would be accepted by everyone at once and unconditionally.
Portal "Eternal youth" www.vechnayamolodost.ru
24.10.2008