Nowadays, more and more Chinese science and technology are changing our lives, such as Tiangong Dream, Beidou Networking, 5G Unimpeded, Dream Artificial Sun and so on. So, in your impression, which is the most anti-heavenly technology?
Today, I will tell you a bit of a counter-natural technology: chimeras.
That's right, the kind of chimera you might imagine, the chimaera, or chimera, is a monster from ancient Greek mythology and legend, with the head of a lion, the body of a goat, and the tail of a python.
Of course, there are such sayings in Chinese and foreign cultures, such as the Fuxi and Nüwa in our legend of the human head and snake body, which are also similar.
Today, scientists are also artificially synthesizing this monster, of course, this synthesis, at present, is not for war, but to cure diseases and save people.
01, shrimp pork heart
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In many cases, human deaths are caused by an organ problem that leads to systemic death (otherwise there would be no organ donation). Therefore, if the problem of organ origin can be solved, many people can live longer. Typically, a kidney transplant is used to treat uremia.
Organs, though, are a problem. So scientists thought of xenotransplantation, that is, finding an organ from other animals to transplant to humans.
The most common is pigs. Moreover, at present, no small progress has been made, for example, at the beginning of the year, foreign scientists transplanted pig hearts and lived for 2 months, which is an epic breakthrough.
However, for this organ transplant, there are still some problems. For example, the most typical problem is immune rejection.
No matter how modified, this organ is an organ of a pig, then you will always face a problem, immune rejection. Humans reject even organ transplants of their own species, let alone cross-species. Therefore, after transplanting organs, it is necessary to always take immune rejection drugs, and even so, it will be difficult to carry.
Secondly, many people's acceptance of this organ from pigs is still very low, and even some groups are strongly opposed to pigs, although pigs are currently recognized as the top 1 organ transplants.
02, borrow chickens to make eggs
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What to do in the face of rejection and people's acceptance? Can it be directly produced from human organs?
Embryos are a good idea, but this road is currently "this road is not open". Because the embryo develops into an organ, in fact, it is already a relatively complete person, and taking the organ is killing, so this road is directly resisted by all mankind.
Some people may wonder, can you induce in vitro orientation to allow stem cells to develop into organs? In theory, yes, but in reality, it is not feasible, you induce cells to develop towards the heart in vitro, you can grow a bunch of cardiomyocytes. However, they are a lump of meat, not a heart. Not to mention, those tiny nerves and blood vessels cannot be achieved by humans at present, so this lump of flesh rots internally as it grows.
Therefore, the miracle of life is really a sigh of relief all the time.
Therefore, some people have put forward new ideas, can we "borrow chickens and eggs"? That is, let the animal grow personal organs in the body?
This is the idea of "chimerism".
03, "chimera" first grows into
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In 2010, this technology debuted, and Nakauchi Kaiguang used blastocyst complementary technology, that is, the iPSCs of other species were mixed into the blastocyst at the blastocyst stage of the animal, so that it could be chimeric, and finally the organs of other animals grew in the animal. In this way, for the first time, the pancreas of voles was cultivated in white rats.
These are two different species Ha
Specifically, Nakauchi first knocked out the pancreas of mice by genetic manipulation, and then extracted fertilized eggs from such mice for culture and injected stem cells from rats into them. Next, the fertilized eggs of mice and the stem cells of rats develop together, mixing with each other. The result is a mouse whose pancreas comes entirely from rat cells.
This research can be said to open up a whole new field, mouse (mouse) and rat (rat) are different species of different genera.
Finally, the pancreas of rats can grow in mice, providing a completely new idea for heterogeneous organ culture. You know, this pancreas is completely a rat cell, therefore, it can be transplanted directly into the rat without worrying about rejection. In addition, this organ itself is developed in the animal body, with a complete rat pancreas function, avoiding the problem of lack of function of the cultured organ in vitro. This provides us with a whole new way of thinking about cultivating human organs.
This is the standard Chimera.
04, Chimera and Humans
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Again, why this experiment shocked, because mice and rats, it seems that there is only a difference in size, in fact, they are two species.
Just like man and chimpanzees, there are two species.
Combining the growth of two species and cultivating organs of another species in one species is not the standard Chimera.
Moreover, this is not a relatively low-end technology such as a rat back with long human ears, after all, you let the animal grow a piece of human flesh, the difficulty is at present, general. But to really have an animal grow a functioning xeno organ is amazing. Humans have been experimenting with stem cells for so many years, but they have not solved this problem, and can only grow a lump of meat.
Think about the difficulty of realizing this not only in appearance, but also in internal structure, but also in blood vessels, nerves and fully functional organs in the current human world.
If so, is it possible to use it for human organ culture?
This technique has a lot of advantages over xenotransplantation.
First of all, the problem of rejection is directly gone. This is not even avoidable by human organ transplantation. After all, people and people have organ rejection.
But what about this? It takes cells directly from the patient's body, such as epidermal fibroblasts, and then uses the patient's cells to culture chimeras. That means that you can directly repel without immunity, and you can still reject yourself.
Second, more accurate customization. The difference between people and people is not only immunity, but also genes, and no two people in the world have exactly the same genes.
But this organ, because it is cultured with the human's own cells, must be exactly the same as the original human.
Well, better. Therefore, this set of technologies has attracted a lot of attention at present.
05, we, in action
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At present, many scientists around the world are studying in this direction, and the progress has also given us hope.
For example, in 2021, the first case of human-monkey chimera
Ji Weizhi, an academician of the Chinese Academy of Sciences, led his team to produce the first human-monkey chimeric embryos in history[1].
The embryos studied have differentiated to the germ layer stage and have demonstrated a potential for chimeras.
Despite the difficulties, chimera research is already on the way, and this is the hope for the future.
[1] Tan T , Wu J , Si C , et al. Chimeric contribution of human extended pluripotent stem cells to monkey embryos exvivo[J]. Cell, 2021, 184(8):2020-2032.e14.