A single cell has been identified that can rebuild the entire organism
Flatworms, small worms that inhabit rivers and lakes, have an amazing ability to. They are able to regenerate virtually without any limitations. Recently, scientists have succeeded in identifying the cell type that gives them this amazing ability.
For years, scientists have observed the astonishing abilities of flatwormsow also known as weasel worms (Platyhelminthes). The creatures are closely related to tapeworms, but are not parasites. They belong to the class of virkow and reach lengths of up to 20 mm. Their regenerative abilities are almost unlimited.
If only the right conditions occur, these worms can rebuild damaged or even compartmentalized poł. In this wayob arise from two individuals with the same genetic material. They can even cause their heads to grow back. Researchers lacked the tools necessary to effectively track this process, until now.
Using a pioneering technique combining genomics, flow cytometry and imaging, researchers have identified adult pluripotent stem cellsoThe stem cell responsible for the amazing regenerative abilities of wormsoin the flat. The scientists reported the results of their study in the pages of the journal „Cell”.
Flatworms can teach us a lot about comostem cells and regenerative medicine. – Our discovery essentially mosee that it is no longer an abstraction, that there really is a comorka, whichora can restoreoc to have regenerative abilities – said study leader Alejandro Sánchez Alvarado of the Stowers Institute for Medical Research.
Each multicellork organism is built from a single comorki, whichora is divided into two identical comorki, then four, and so on. Each of these cellsorek contains exactly the same DNA and is considered pluripotent – meaning it can contribute to all possible types ofoin comoIn the organism. But somewhere along the way these comoThe starter cells – called embryonic stem cellsostem cells – are resigning themselves to a different fate and becoming comorkami skory, comorkamikami serca, comorkami muscles or another type of comorek. As the organism develops, the cellsoThese cells are replaced by comorki in established roles.
In humans, the life stage in whichorym komorks have infinite potential, otherwise moInvolving are pluripotent, lasts very krotko and ends up actually krosoon after birth. But flatworms never lose this ability. Comorks together with worms enter adulthood becoming adult pluripotent cellsostem cells. Researchers are convinced that they hold the secret to regeneration.
Although studies on this type of comorek have been going on for more than a century, it is only in recent years that scientists have been able to characterize this massive population of comorek using modern molecular techniques. The efforts of the scientistsow have shown that this seemingly homogeneous population of comorek was in fact a conglomerate of rotrong subtypesow o ros properties and the ros different patterns of gene expressionow.
Although researchers have managed to learn a little about these mysterious comorki, it turned out that it is extremely difficult to isolate exactly those thatore allow unlimited regeneration. Sánchez Alvarado and his teamsoł began to look for a characteristic feature thatora could pomoc identify them.
One such trait, whichora has long been used for the odroThe research was carried out on the basis of the results of the studyostem cells from other comoworms, is the cell markerostem recs known as piwi-1. An Zeng belonging to the team of Sáncheza Alvarado first separated the comorki, whichore expressed this marker from those thatore they did not have. He noted that comothese cells can be divided into two groups – one, whichora expressed high levels of piwi-1 and the other, whichora expressed low levels of the marker. Zeng found that only those with high levels of piwi-1 fit the molecular definition of adult pluripotent cellsostem cells.
– This type of roearly quantitative analysis of gene expressionoin and the level ofoin proteins has never before been performed in flatwormsow. Many researchers assumed that all comorcs expressing piwi-1 are pluripotent and it does not matter how much of the marker they express. We have shown that it matters – admitted Sánchez Alvarado.
In a further study, Zeng selected about 8,000 comorek with high levels of the piwi-1 marker and analyzed their gene expression patternsow. To his surprise, Zeng identified 12 ro¿n subtypesoin these cellsorecords. Through a process of elimination, he then excluded any subgroups with genetic signatures indicating that the comor cells were destined to perform a specific role. Thus, he was left with two subgroups, whichore named Nb1 and Nb2.
By designing a green fluorescent protein thatore clinging to the surface of these comorek, researchers were then able to track exactly where in the body the wormsoin were found these comorki and observe what happens when flatworms have been injured. And indeed, if scientists cut the bug, the comorki Nb2 multiplied at the site of injury and healed the wound.
What’s more, the teamoł conducted another experiment, in whichothey have refined theorki Nb2, and then injected them into the flatworm, ktory was exposed to lethal doses of radiation. Komorki Nb2 repopulated the worm’s body and saved it from death.
The protein, whichore undergoes expression on the surface of adult pluripotent comostem cells in wormsow – known as tspan-1 – occurs roAlso in humans. This, the researchers suggest, may point to some new possibilities for the.
– Enriched with a pluripotent population of comostem cells, whichora opens the way for many experimentsow hoore previously not possible. The fact that the tracer, ktory we found, is expressed not only in flatwormsoin, but also in humans, suggests that there are some conservative mechanisms thatore we can use. I expect this to be widely applicable to any organism thatory ever relied on the comostem cells to become what they are today. And it’s basically all organisms on Earth – explained Sánchez Alvarado.
Sourceobackground: Stowers Institute, The Independent, fot. CC BY-SA 3.0/ Wikimedia Commons/ Eduard Sola