What is important about stem cells

Healing with stem cells

Stem cells instead of organ transplants

Scientists around the world are looking for ways to use stem cells to cure disease. You have to make sure that the stem cells do not form tumors. In addition, the new, artificially created cells must function in the body. Without causing side effects - and without already refusing to work after a year.

Doctors are already treating blood diseases such as leukemia with the help of stem cells: These are contained in bone marrow - and can save lives if they are donated to a sick person. They can develop in all cells of the blood-building system, red blood cells, platelets and white blood cells.

The stem cells could make a difference in medicine. In the future, they should help treat various diseases, such as heart attacks. If a person suffers a heart attack, the heart is sometimes not supplied with sufficient oxygen. Billions of heart muscle cells die within a short time.

Hardly any therapies for heart attack patients

"So far, there have been hardly any treatment options for people with a heart attack," says Ulrich Martin, who works at the Clinic for Thoracic, Cardiac and Vascular Surgery in Hanover, the largest heart transplant center in Germany.

"These heart muscle cells cannot renew themselves afterwards, like skin cells, for example," he says. The tissue scars instead of regenerating. The result: the heart continuously loses its pumping capacity over time. "We can slow down this process, but in the end all that helps is often a heart transplant." There are too few donors.

A dilemma for cardiologists and heart surgeons. Martin and his research colleagues from the Hannover Medical School have been looking for a way to replace the dead heart muscle tissue for years. Her hope: with the help of stem cells, new muscle tissue could be grown and implanted in the patient's heart.

The researchers spent a long time looking for suitable cells. The use of embryonic stem cells is still ethically controversial today. In addition, these stem cells are not easy to handle: They usually come from an embryo whose genome differs from that of the recipient. The result: rejection reactions. The recipient's immune system does not accept the new cells - or they attack the cells in the new environment.

Adult stem cells, which every person carries into old age, rarely lead to complications in therapy. But tests have shown: These stem cells are not so versatile - and can only transform themselves into certain types of tissue. For example, they are not suitable for heart muscle cells.

Heart tissue from the test tube

Stem cells can also be obtained artificially in the laboratory. "Today we know that a certain gene plays a key role in this," says Hans Schöler from the Max Planck Institute for Molecular Biomedicine in Münster. He and his colleagues were able to show that a gene called "Oct4" is usually only active in two cell types: in embryonic stem cells as well as in egg cells and sperm.

In contrast, it is inactive in all mature body cells. If you want to transform these adult cells into the all-rounder stem cells, you have to wake Oct4 out of its slumber.

The Japanese Shin'ya Yamanaka succeeded in doing this in 2006. The induced pluripotent stem cells (iPS) showed a similar transformation potential as embryonic stem cells. The researchers at the Hannover Medical School also tried this procedure.

"We used the same technology as Yamanaka for our work on the production of heart muscle cells," says Ulrich Martin. Six years after the Japanese had announced their success, they too came a lot closer to their goal: In 2012, Martin and his colleagues succeeded in growing functional heart muscle tissue from iPS cells. This has the properties of natural tissue.

Other scientists have also succeeded in reconstructing the research results.

Risks cannot be ruled out

The stem cells promise blessings, but they also involve risks: They can begin to proliferate in an uncontrolled manner if they are transferred to humans during therapy. Researchers refer to the growths as teratomas. All possible cell types, such as skin, muscle and nerve cells, are found in such tumors.

Teratomas are not cancerous, yet dangerous. As they grow, they put pressure on the organs around them. Both embryonic stem cells and iPS cells can cause teratomas. To prevent this from happening, the researchers came up with a trick.

You do not transplant the stem cells yourself, but grow the desired tissue in the laboratory and transfer it to the patient. "We can already ensure that only pure heart muscle cells are left for the tissue to grow," says Ulrich Martin.

Dangerous: When the genome changes

The artificially produced stem cells also harbor another risk: They can form degenerate cells - and thus malignant tumors. One reason for this: To create an iPS cell, the researchers take cells from the body that have already reached a certain age. The older the donor, the more likely it is that genetic changes have crept in. When a cell mutates, it passes this change on from generation to generation, with each division.

Another potential risk posed by artificial stem cells: Mutations can occur during reprogramming of the various body cells. These genetic changes cannot always be controlled and can cause cancer. "In order to rule out this risk, we have to characterize the cells for the transplant very precisely," says Ulrich Martin. This is technically feasible, but involves a great deal of effort.

Help with old age blindness

When vital organs such as the heart are affected, initial tests on humans are a delicate matter. There are no clinical studies yet. It is different with organs like the eye.

"The eye is a very limited area of ​​the body," says Boris Stanzel from the eye clinic at the University Hospital in Bonn. The risks are therefore manageable and controllable. At the top of the list is the cure for old age blindness with the help of stem cells.

Age-related macular degeneration is the most common cause of blindness for people in the western world. Around four and a half million people in Germany suffer from it. The visual cells of the retina are no longer properly supplied. They are dying off.

The researchers want to convert the stem cells into the respective type of retinal cells - and then inject them into the eye. Such a retina has been grown in various laboratories around the world.

The scientists also use adult stem cells for this: "Adult people harbor ten percent of a cell population in their retina that has a multipotent stem cell capability," says Stanzel. Together with research colleagues from New York, they managed to grow entire pieces of tissue - and to transplant them into the eyes of rabbits. "The cells lasted up to four weeks without being rejected by the immune system," says Stanzel.

In the United States, researchers from the University of California have already carried out initial clinical studies on retinal transplants. They created retinal cells from embryonic stem cells and successfully transplanted them into human eyes. However, the individually injected cells were destroyed again by the patient's own immune system within two weeks.

The future of stem cell therapy

"The future still has to show whether the artificially produced cells will even survive permanently in the body," says biomedical scientist Hans Schöler from Münster. The problem is that these cells lack the natural development process in the laboratory.

The first cells in our body interacted with others in the egg cell and were programmed in this way, says Schöler. "You can imagine the artificial cells like Kaspar Hauser, who was born without contact with other people." As a result, Hauser was restricted in many abilities, for example he was barely able to communicate with other people.

The therapies with embryonic or artificially generated stem cells - they will come at some point, many scientists agree. "Stem cell transplants in the retina could be routine in ten years," believes Boris Stanzel. It remains to be seen whether these will then be affordable for everyone.

Boom in drug research

Artificial stem cells, however, offer another potential that has nothing to do with creating replacement organs and tissues: They can be used to research diseases that were previously hardly possible.

For example, doctors can easily take a skin sample from people with a hereditary skin disease. The diseased cells can then be examined under a microscope and grown in the laboratory. Scientists can carry out experiments with the diseased cells in order to examine the defect.

Medicines can also be tested on these cells in a test tube. In people who suffer from a hereditary nervous disease, for example, this was hardly possible until now. The researchers could not take a cell sample from the brains of those affected while they were still alive.

With the help of the artificially generated stem cells, a diagnosis is now possible: a simple skin sample can be taken from the patient. The skin cells can be converted into nerve cells in the brain in the test tube. Examinations or drug tests can be carried out on it - this would not be possible without stem cell research. "In the coming years this will lead to a boom in new active ingredients in the pharmaceutical industry," says Ulrich Martin.

Research on embryonic stem cells, in particular, has another potential: How does an embryo develop? At what stage of pregnancy, which drug is dangerous for its development? These are also questions that can be answered using stem cell research.