Stem cell: The hard copy

Doing science means working with rules. Repetition is a peculiarity of doing science. However, not everyone has never tasted the feeling of having " golden hands" and " thank you on blessing " to get the desired results. The following article shares that experience.

Explanation: the writer's wordplay, the hard copy is the print, but also means that something is hard to repeat.

Eight years ago, a group of scientists in Canada and Italy published an unbelievable article in Science magazine. Their material is rat neural stem cells, programmed cells that can only differentiate into brain tissue. At the time, the current doctrine suggested that such cells, ie cells that had developed in a given direction, could not change the direction of differentiation to create other types of cells. The article in Science magazine at that time really challenged this view. The team inserted these stem cells into mice that had lost their marrow. And miraculously, a miracle seems to have happened: these stem cells replaced

MAPCs cells injected into mouse embryos
(Photo: Sinhocvietnam)

change their fate and turn into hematopoietic stem cells, which are usually found only in the bone marrow and are the source of red blood cells and other immune cells. The article was put on a very provocative title "Turning the brain into blood". It is part of a wave of published studies of the existence of differentiation and it suggests being able to create replacement tissues without destroying embryos for embryonic stem cells.

Another research team took more than two years of hard work and diligence to prove that Science's article was not as promising as it once was. This group tried to repeat the experiment by putting neural stem cells into 128 mice that were also marrowed. But after a thorough analysis of every nook and cranny, they still couldn't see these stem cells transforming into hematopoietic stem cells. They conclude that cells can sometimes redirect differentiation, but this only occurs because of the genetic changes accumulated after a long time in Petri dishes. The authors of the other paper disagree with this conclusion, and so far there is no general consensus on whether the phenomenon has practical significance in medicine.

The reputation is threatened

The controversy of "turning the brain into blood" highlights a more common problem in the field of adult stem cell research: many research teams have struggled to repeat the experiments "seem to be full. hopeful " of other research groups. Repeating the experiment is an important and very laborious part of a scientific process and this is particularly troublesome in this area because of the limitations surrounding the use of stem cells and inexperience. of researcher and technical difficulties. Many scientists feel that these issues are hindering development and harming the reputation of the field. "The damage to this area is huge ," said Naohiro Terada, a stem cell researcher at the University of Florida Gainesville. 'If we continue to publish' advertising ', no one will believe in stem cell researchers anymore.'

The problem of repeating the most recent experimental results attracted the attention of the press because there was renewed interest in the Nature paper in 2000 by Catherine Verfaillie of the University of Minnesota, Minneapolis. After cultivating mouse bone marrow cells for several months, the group announced they could recruit a group of extraordinary cells they named mature mature pre-specialized cells (MAPCs-multipotent). adult progenitor cells). When they injected these cells into developing mouse embryos and studied mosaic mice that were born from this experiment, MAPC cells seemed to contribute to all kinds of cells in the body, including: brain, Heart, bone marrow, skin, blood and lungs. This article and several other articles suggest the possibility of using MAPCs in organ regeneration and repair. The article created an exciting atmosphere in this field of research because no adult stem cells have been found to be able to reproduce such a variety of cells, an almost no possibility. What embryonic stem cells are.

The mosaic mouse in Verfaillie's experiment is very difficult to repeat (Photo: Sinhocvietnam)

However, since the announcement, the Verfaillie group's results have proved extremely difficult to repeat, although some groups have successfully repeated part of it. Earlier this year, after spending years studying how to study MAPCs, Scott Dylla, a postdoc worked in Irving Weissman's lab at Stanford University and was able to use MAPCs to differentiate into hematopoietic stem cells. in the mouse. But although there have been many attempts, no group has succeeded in repeating the core results of Verfaillie's work - injecting MAPCs into embryos to create all the major types of cells in the body. .

'I have not seen any convincing data to show that someone has successfully repeated the mosaic mouse experiment, so I do not think this part of the work is really true,' Rudofl Jaenisch at Whitehead Institute in Cambridge. , Massachusetts says. His team also tried but failed to repeat the experiment.

Limitations on access to cell sources

Stuart Orkin at Harvard Medical School, Boston asked Verfaillie's lab to send MAPCs cells to him a few months after the group's article was published. He discovered in the agreement on the transfer of materials the terms, for example contracts that govern the use of research materials, say that users are not allowed to disclose information about cells to people. Other do not participate in the project.'We can't accept that , ' Orkin said. Broadly speaking, many researchers sometimes cannot access stem cell lines because of competition between labs and because these cells can be commercially valuable. Therefore, obtaining the desired stem cell lines may be limited.

A significant part of the problem lies in the methodologies for working with these cells that are still in the process of forming, Paul Simmons of Texas Houston University, also one of those who tried to repeat the experiment. but hopelessly said.'So far there have been a series of changes to the conditions that can be repeated on the experiment,' he complained.

For example, later Verfaillie research shows that MAPCs cells grow better in less ooxxy conditions and are best collected from young mice.'The method is everything, but it is the new details that make us' headache', Simmon, director of the Stem Cell Research Association commented. 'The method section in the articles really needs to have all the details in the protocol'. But scientists feel that they are forced to omit the method section to be able to insert as much data as possible into articles published in prestigious journals, which are very limited in page numbers. And Verfaillie confirmed that improvements in culture conditions were discussed at the workshops and were published.

The situation around Verfaillie's article became darker last month when questions about re-used images in the Nature article and another published in Experimental Hematology led University of Minnesota to call a meeting. Investigation of her research.

This investigation found that some of her processes had problems. Verfaillie once claimed that these reused images were an unfortunate mistake. And other scientists do not think that she faked the results. In fact Verfaillie, currently working at the Catholic University of Leuven, Belgium is always known as a careful researcher. Verfaillie said that in the Nature paper, her group came up with some pseudo-likes to be able to give these mosaic mice and confirm that their conclusions are still valid.

However, she admits that the image reuse error in that study may have caused confusion among adult stem cell researchers: 'We made the mistake that I am responsible for, and we have done everything we can to alert the research community about these mistakes' Verfaillie wrote in an email to Nature. This confusion seems to be continuing: last week there were new questions about copy images in other works in Verfaillie's lab.

Shortage experience

Technical problems have led to many attempts to replicate stem cell experiments that failed. The best way to separate and work with stem cell lines has only just been discovered, and it is the nature of the stem cells, which are constantly dividing and mutating that make the acquisition and maintenance of the right population The original stem cells become very difficult.

In 2001, a Diane Krause-led research group at Yale University published a major paper in the Cell magazine, announcing that from a bone marrow cell can differentiate into a variety of types. cells, from the intestine to the lungs or even the skin. But the following year, another research group countered, saying they could not obtain such a type of cell from the bone marrow. Krause said that although some groups did something like parts of her work, some other groups did not do the same, and it was important for her to find out why. Perhaps the main reason is that different labs use different techniques, so they have separated slightly different populations of primary stem cells, Krause said.

In the same year, two other research groups demonstrated that Krause's results could be explained by cell fusion, in which stem cells seem to have turned away from the fact that merge with other cells. Cell unification experiments have helped negate the idea of ​​differentiation, which has become a taboo in the most serious stem cell researchers. Krause said her team is conducting experiments to clarify how the phenomenon of consolidating cells contributes much to the published results.

Inexperience is another problem in the field of stem cell research, which attracts new researchers because of its hot reputation. This is particularly a problem in differentiated navigation studies, says Sean Morrison at the University of Michigan, Ann Arbor. Some may make unfortunate mistakes because they just started studying. Some may be very sloppy.'In some cases, some people with thoughts of wanting to be' fast-known 'and often interested in posting in reputable magazines rather than finding the right answer,' he remarked.

Does this have a big impact? Similar problems often arise in new areas of research that scientists must struggle to repeat the seemingly promising data initially. Eventually some results will be eliminated if they cannot be repeated. But the area of ​​adult stem cell research is so critical because of its promise in the field of medical applications and the potential to replace embryonic stem cell research. It will take a lot of time and money to see if an experiment can be repeated. Difficulties in repeating the experiment may partly explain why there is no consensus about the nature of most adult stem cell lines, or determine which ones are most promising in medical applications. .

'If your research depends very much on the honesty of an observation, your duty is to repeat that observation - if it is not a grounded observation it will become a obstacle. be afraid, and how easy it can be to see how a field of study will be hindered when it comes to chasing typical examples instead of moving forward in new directions. "

Nguyen Ngoc Luong