There was a time not talking about anything other than stem cells. Ten or fifteen years ago you were not anybody if you did not have an opinion on this research and its ethical implications. They were great promise until suddenly we stop talking about them.

Today we could say that “CRISPR kill the Stem Cell Star” and so we wondered, what it was of stem cells. What are they exactly? What has meant and what future awaits them? Why they have ceased to be fashionable? So we’ve prepared a series of post to get closer to the incredible world of stem cells.

What are Stem cells?

Stem cells are cells that have two properties: firstly, they are able to renew themselves (to produce more stem cells) and, on the other, with appropriate signals can lead daughter cells (cell lines that will eventually become specialized cells).

For many years, scientists were looking for was a way to keep cultures these cells so that under certain stimuli could develop into differentiated cells. To understand, what scientists were looking for was a way to keep fresh clay (stem cells) so they could use it to produce different objects (specialized cells) when necessary. It was not easy.

Stem cell
Image Source: Google Image

How to make a stem cell?

Once the egg is fertilized, creating the zygote, a cell totipotent that she alone is capable of creating whole organism. As the zygote begins to divide the morula forms a compact sphere also totipotent cell.

Specialization begins a few days later when the blasticito (or blastocyst) arises composed of the blastoderm (from which will emerge the trophoblast and then the placenta) and blastocele, a cavity filled with fluid in which the inner cell mass (ICM) is.

Mci cells are no longer totipotent, pluripotent are. Basically the difference is that while the first can, by themselves, generate an entire organism, the latter not: although they may potentially become so, they need to get the placenta (which cannot be).

With nearly pluripotent cells have stem cells. The problem with these cells is that they ‘are programmed’ to become other cells; i.e. not remain as such long. To have to extract stem cells and cultured in vitro under certain conditions. Thus, they are become ‘immortal’, pluripotent and revolving.

In search of human stem cells

In the early years of the eighties, scientists were able to make this first embryonic cell of mice. So, if we all, we had to wait twenty years until 1998, almost simultaneously, two research groups announced they had succeeded in obtaining human embryonic stem cells.

It was in November. On November 6, James Thomson and his team at the University of Wisconsin-Madison published in Science that they had been able to obtain stem cells from excess blastocysts programs fertilization in vitro. On the 10th, John Gearhart of Johns Hopkins published in PNAS that they had obtained germline stem cells from aborted fetuses (in this case, are isolated from the germinal ridge where cell differentiation occurs).

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Trouble in Paradise (genetic)

Needless to say that this discovery was as celebrated as condemned. The promise of cell therapies passed by the almost systematic destruction of many human embryos. Fortunately, a few months later, in January 1999, Angelo Vescovi and his team announced they had succeeded in creating various types of blood cells from neural stem cells of adult rats.

Understanding this just requires a detour: Embryonic cells are not the only stem cells that exist. There is some debate over who was the first person who discovered stem cells. It seems that they were the work of Theodor Boveri and Ernst Haeckel (dating from 1868) which, inspired by the ideas of August Weismann, developed the concept. Others say it was a thing of Sabin in 32 or Pappenheim at 17. Be as it may, the key date is 1963, when Till and McCulloch published his work on hematopoietic stem cells.

The hematopoietic cells are stem cells in the bone you install ósea’de adult animals that are dedicated to produce more blood when needed. Eventually, it was discovered that this type of stem cells were in many organs, especially those who had more wear; there are, for example, skin, nervous system or mesenchymal tissues such as bones, muscles or tendons. The question was whether they could use such cells to produce other specialized cell or cells could only develop their generations. That’s what the team discovered Vescovi, that you could do anything with them. Ethical problems passed again, even the background.

Regenerative medicine

The main therapeutic hope to be had in stem cells consisted that could develop cell therapies and tissue transplants without the current problems of those who have spoken before. This gave rise to a whole ‘specialty’ in medicine: regenerative medicine. This area where tissue engineering and molecular biology combine attempts to develop processes for replacement or modification of cells, tissues and organs to regain its normal functions. And their progress has not been waiting.

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Although we have yet to fully clarify the identity and localization of neural stem cells, they have made great achievements in the treatment of neuronal and muscle diseases. The (re) generation of functional cells have improved the way we approach spinal cord injury or stroke. In addition there are very interesting works using cell transplantation as a therapy against Parkinson’s, Huntington’s or Duchenne dystrophy.

Hepatocytes (adult stem cells liver) appear to reside in the bone marrow; therefore therapies for some liver diseases were initiated by bone marrow transplants. In the early 2000s, these techniques began to bear fruit and be able to cure diseases such as tyrosinemia. Later they addressed the hepatitis B and C and liver cirrhosis.

They are well known, the work of Bernat Soria with insulin -secreting cells with which managed to cure diabetic mice. In this line, Amon Peckmade profound progress in reversing diabetes while at UCSD announced they had managed to reactivate the production of insulin making produce all kinds of pancreatic cells from hepatocytes.

In matters of the heart, the thing was more complicated, although Geron showed that embryonic stem cells could be produced cardiomyocytes. In 2001, Albert Einstein Medical College in New York announced that they had been able to repair 68% of cardiac tissue infarcted mice by injecting stem cells in the bone marrow. Currently, different techniques are used not only for myocardial infarction, but also other types of heart disease.

On the other hand, and as to end this little review, very soon John Hopkins University was able to develop tissues of organs such as the intestines, lungs or skin from hematopoietic cells. As part of these efforts they have been rebuilt bladders (in dogs), have created biological bone prostheses and have achieved functional artificial arteries. Today, regenerative therapies used in lung, rheumatic diseases and many types.

Medicine has changed forever

But surely, the biggest change that have represented the stem cells in medicine has been the change in mentality. Everything we thought we knew about the biomedical sciences and therapeutic approaches turned out to be a tiny fraction of what we could do.

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