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A debate about the necessity of developing a mouse with human genetic data for laboratory experiments

The developed embryo will have human cells in addition to the mouse cells

Avi Blizovsky

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A panel of scientists in North America is supposed to gather for a discussion where they will argue about a planned experiment in which scientists will create a "chimera" - a hybrid creature between a human and a mouse. This strange combination will help doctors try potential stem cell healing processes to fight serious diseases.
However, many experts consider the strange study unethical and unethical.
One proposed trial would involve injecting human stem cells into primary cells of a mouse embryo at the blastocyst stage. Then the scientists will ask to see what those stem cells will do in the developing embryo.
Stem cells are the progenitor cells of the body. These are undeveloped cells that have the potential to develop into a wide variety of tissues.
The scientists want to see if these human stem cells will help create tissue in the mouse embryo.
While the scientists cannot guarantee that the fetus will not die, there is a high chance that a mouse carrying human cells will be born.
Many scientists believe that this mixture will be of great importance when it will be possible to test the human response to many diseases and allow doctors to create a more effective model for treatments.
If the human cells are evenly distributed throughout the mouse's body, it could also be used to understand how the stem cells will work in healing humans.
However, there is also concern that the mouse with the human cells will develop a larger brain or that the gametes will produce human sperm.
In the debate that will take place next month at the Academy of Sciences in New York, nine researchers will participate discussing the broader aspects of ensuring the quality of human stem cells.
Dr. Janet Rossant from Mount Sinai Hospital in Toronto, said that she opposes the development if the cells contribute to too much development of the mouse. "I believe that this is something that most people will find unacceptable." saying.
Dr. Ann McLaren of the Wellcome Cancer Research Center in the UK and the University of Cambridge says she has some objections to using the technique because these cells will survive for a long time in the chimera embryo. "We really have to see what these cells will do in the developing embryo." She says because the cells come from a larger animal, they will tend to divide at a slower rate and won't survive as long. However, if anything, you should first try ape stem cells on mice and not humans. "Human stem cells have already been injected into mice and live and human genes have already been added many times to mouse embryos", but before taking another leap, to test it. she concludes.

A concentration of life science experts
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Israeli researchers implanted human cells in chicken embryos

by Tamara Traubman

Biology / Researchers in the US and Canada propose to transplant human stem cells into mouse embryos at an early stage of development

The technological developments of recent years allow scientists to transplant cells and genes taken from one animal into the body of another animal. For example, in the past, human cells were transplanted into the bodies of adult mice.
However, recently a team of Israeli researchers transplanted stem cells taken from human embryos into the spinal cord of chicken embryos. The researchers stopped the development of the embryos before they hatched. This experiment, of transplanting human cells into animal embryos, is the first of its kind. These days there is a discussion going on in the USA about the moral consequences of transplanting human cells into animals.

According to the team of researchers, led by Dr. Ron Goldstein, a developmental biologist from Bar Ilan University, and Prof. Nissim Benvanisti from the Hebrew University, the purpose of the experiment was to study the first stages of development of the body. As a result of the transplantation of the human cells, chicken embryos were obtained whose entire organ - the spinal cord - is mostly made of chicken cells and a small part of human cells.

Embryonic stem cells are the "source cells" from which the body is built. They are only found in embryos a few days old, and are capable of becoming almost any type of cell in the body. In addition, under laboratory conditions, these cells can reproduce almost without limit. Recently, researchers from the USA and Canada proposed to inject stem cells from human embryos into mouse embryos that are in an early stage of development. According to them, the purpose of the experiment will be to test the medical qualities and benefits of the embryonic stem cells. According to them, the best way to test this is to examine how the stem cells function in the developing body of mouse embryos.
Transplantation of human genes into mice is a common practice. Scientists insert human disease-related genes into the genomes of mice to study diseases such as Alzheimer's and stroke that would never naturally develop in mice. Mice that will be born as a result of the experiment proposed in the USA will be hybrids made of a mixture of cells from two different species, with human cells scattered throughout their bodies.

If the human cells survive in the mice's body, the resulting product will most likely be a mouse with human cells that obey mouse rules. Among other things, the human cells will participate in the construction of the eggs and sperm in the mouse's body.

The proposal to inject human stem cells into mouse embryos was made at a meeting held this month in New York under the auspices of the New York Academy of Sciences and Rockefeller University. The meeting was reported in the scientific journal "Nature." The organizer of the meeting, Prof. Eli Bribanello, a biologist from Rockefeller, said that in one of the experiments discussed it was proposed to inject stem cells from human embryos into mouse embryos that are at the beginning of their development and look like a hollow ball that might fit. According to him, researchers will then be able to check whether the human cells contributed to the development of all types of tissues in the mouse.

However, many researchers oppose the proposed experiment. "It seems unethical to me, and I don't see any scientific benefit in this type of experiment," said Prof. Benjamin Raubinoff, a stem cell expert from Hadassah Ein Kerem Hospital who participated in the experiment on the chicken embryos. According to him, there are many other ways, which are applied today, to test the capabilities of the cells. "I think that attempts of this kind can have a very negative effect on public opinion and its support in the field of embryonic stem cells and their development for medical transplantation purposes."

According to Goldstein and Raubinoff, there is a fundamental difference between their experiment and the experiment proposed in the US. "I think there is a difference in concept here," Raubinoff said. "The concept they presented is the creation of hybrids in which it can be assumed that the human cells will reside in all systems, including the sex cells. The cells will be injected there at a much earlier stage of development. We implanted the cells in embryos at a much more advanced stage of their development, when organs had already formed, and they were few and located in a very specific area. We never had the intention of creating a whole embryo."

Prof. Hagit Maser-Yeron, the chief scientist of the Ministry of Science, which finances many studies on embryonic stem cells in Israel, says: "On the one hand, because it is embryonic development, there are changes that may be substantial. On the other hand, the body of an adult is also dynamic and its cells change. At each stage of development there is a different ethical question. The question is where do we draw the line? I don't have an answer to this question today, but it is clear that it needs a discussion within the ethics of science."

"Today there are no uniform national rules for research in human embryonic stem cells," claims Dr. Gil Siegel, a lawyer and physician from the University of Haifa. "An experiment that would include the creation of hybrid children, as proposed in the USA, is a border that, as far as we know, has not been crossed to date and is considered unacceptable according to the conventions of countries and ethical practice."

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