Now stem cells will build our health
The best healing is performed by our stem cells. Now the researchers recruit the body's own health workers to build up new healthy organs.
Text: Fredrik Hedlund, first published in the magazine Medical Science, no 4, 2015.
The human body has an amazing ability to repair itself. Everyone knows that a skin cut quickly heals itself. The body can even handle quite large wounds with just a little help to hold together the edges of the wound, using a plaster or stitches. A person who breaks their leg can rest assured that they will walk again. However, it is beneficial if the fracture is secured with plaster, for example, so that it heals straight. But the healing itself is automatic.
But this is not always the case. Not all organs and tissues can recreate themselves, or regenerate as it is called. But with some additional help it is possible. This is the foundation of the rapidly growing area of research that doctors refer to as regenerative medicine.
That is, helping the body to help itself. And the help comes in the form of stem cells, immature cells, that exist naturally in the skin, in bone marrow or other parts of the body. Stem cell research is still very much under development and no one really knows what paths it will take in the future, but there are currently some main lines of inquiry and a number of smaller side trails.
Earliest known example
The earliest and so far most well-known example of stem cell treatment is bone marrow transplantation that was performed for the first time in the world in 1968 and in Sweden in 1976. Blood-forming stem cells were then transplanted to the bone marrow of a patient.
Other stem cells from the bone marrow have also been used in the same way; "mesenchymal stem cells", which can develop into bone, cartilage or connective tissues, etc. Bone marrow stem cells are examples of mature stem cells (see figure) that are very useable but that also have certain limitations. For example, it is not possible to cultivate large amounts of mature stem cells. It is also difficult to separate mature stem cells from other cells; something that is not always appropriate. Mature stem cells are multipotent, which means that they can build many types of cells but not all.
That is why it was a great advance when American researchers in 1998 could show how they had succeeded in creating embryonic stem cells. They can divide an infinite number of times and are pluripotent, which means that they can develop into any cell type found in an adult body. Most embryonic stem cells come from fertilised eggs left over from IVF. The cells are often so foreign to the patients that their immune system reacts and a rejection occurs, though this can be managed with immunosuppressive drugs. Another idea is to build up a large bank of different types of embryonic stem cells so that a sufficient amount of tissue-like cells can be chosen for each patient. This is currently happening in several parts of the world, including Karolinska Institutet.
But creating treatments out of left-over fertilised eggs has, primarily in the USA, been questioned based on ethical principles. Furthermore, the access to different genetic sets is limited. That is why the possibility of getting closer clinical application increased with the next big step.
Creating stem cells
In 2006, Japanese researchers were able to demonstrate an entirely new way of creating stem cells. They simply took regular cells and gave them an extra set of four genes that caused them to reverse their development and return to stem cells again. They will then be reminiscent of embryonic stem cells but have a completely different origin. The researchers called them induced pluripotent stem cells, or IPS cells.
The first attempts were made with mouse cells, but as early as 2007 they were able to revert human cells and now it is done with normal skin cells as original material. In the beginning, however, the cells that were developed from IPS cells were problematic in that there were cells that had not matured properly and that could cause cancer growth when transplanted. Today this can be managed. But it also seems that the cells change during cultivation. The first clinical study on IPS cells recently had to be aborted due to potentially dangerous cell changes.
The basic principle of helping the body repair itself is to control the stem cells so that they develop into the type of cells necessary to treat a certain disease. There are currently a large number of research projects to develop cells that can help patients with different types of diseases to repair themselves. Sweden is at the forefront in a global perspective.
This big question for most researchers within this field is where to source the stem cells. For most cases, one of the three versions mesenchymal (a type of mature stem cells), embryonic or induced pluripotent stem cells are available.
Liver diseases will be treated
But not for everyone. Professor Stephen Strom, at the Department of Laboratory Medicine, Karolinska Institutet, will within the next few months initiate clinical trials where he will treat small children with congenital liver diseases with cells from the inside of the membrane of the foetus. The story behind his discovery is almost as good as the discovery itself. But he prefers to tone this down.
“I was just lucky. There is a saying that it is better to be lucky than to be smart”, he says.
Stephen Strom started his scientific career at the Kansas City University, USA, with an interest in liver cells and how they handle carcinogenic chemicals. In order to study the cells' behaviour he developed a method for isolating liver cells from donated pieces of liver that could not be transplanted. Together with an American transplant surgeon he eventually developed the world's first method of transplanting these cells to patients.
“In collaboration with several different surgeons, I have performed transplantations on about 25-30 patients, but the big problem is the lack of decent liver cells for transplantation. The surgeons have become better and better at successfully transplanting the left-over pieces that I was previously given. It's great for the patients, as it is a curing treatment, but their success has had negative consequences on my research”, he says.
He says that when transplanting liver cells in order to treat liver diseases, many cells are required.
“Even a little new-born baby needs several billion cells for a transplantation. A larger patient with acute liver failure needs about 15 million cells and it is in no way possible to manufacture that quantity, neither with embryonic stem cells nor induced pluripotent stem cells”, he says.
Instead he was lucky. In his role as editor of a scientific journal, he was reviewing a manuscript for a scientific paper written by another researcher. The trial involved gene therapy by means of cells from the inside of the membrane of the foetus being transplanted to laboratory animals.
“What I discovered on the photographs they sent was that the transplanted cells looked like liver cells. And I thought, oh my god, these membrane cells could become liver cells if we just place them in the liver. I don't think the other researcher understood this. He was not working on liver cells”, says Stephen Strom.
He immediately started to transplant human epithelial cells from the membrane of the foetus – which is attached to the placenta – to mice, and it worked straight away without any processing of the cells.
“We collect the cells and we transplant them, that's what we do. We don't need to treat them, we don't need to deal with Petri dishes, we don't need to differentiate them to liver-like cells. We administer a cell infusion straight into the blood system that goes to the liver. The cells will stay there and grow attached to the liver at the same time as they develop into liver-like cells. We let the liver do the work for us”, he says.
The big question is, how is it possible that this just works?
I don't know why it works. I can only guess. During foetal development, the placenta functions as the child's kidneys, liver and lungs, among other things. The placenta tissue is unique in that it has to perform a great number of tasks. We know that it expresses liver genes and since these genes are already active in the cells that we isolate, it may just be just a question of increasing the expression in them. It's like turning up the volume on something that already exists”, says Stephen Strom.
The placenta is a unique organ
He has not had any immunological problems either, even though he has transplanted human cells to mice; something that is due to the special contents of the placenta.
“The placenta is the organ that allows the child to be born without the mother's immune system rejecting it. The placenta contains human leukocyte antigen G (HLA-G), which tells the mother's immune system not to attach the tissue. Without this factor we would still be laying eggs”, he says.
That is why he is fairly sure that it will be possible to transplant the membrane cells without having to subdue the patient's immune system.
“Contrary to liver cells, where we have to put the patient on immunosuppressive drugs when we're transplanting the cells, we can probably transplant these cells without having to do that. That would be an absolutely crucial step forward for cell transplantation”, he says.
He agrees that this sounds almost too good to be true, but at the same time he has produced results that indicate that what he says is correct. What is really fascinating is that previously, these stem cells would just be thrown out.
“There is a saying that you shouldn't throw the baby out with the bath water, but that is exactly what we were doing. We used to throw out the placenta, so we were throwing away a rich source of stem cells”, he says.
Whether his research findings are too good to be true or not will soon be revealed. Stephen Strom has been given ethical approval to treat the first ten patients and is now just waiting for a last formal approval that the method of sourcing cells is adhering to all applicable rules.
“Hopefully we'll have a complete approval by the end of the year and we could start then or at the beginning of next year with clinical transplantation of these cells”, he says.
The patients that he is considering for treatment are children born with a defect in one single gene that causes a critical liver function, something that results in these children often having to go through a liver transplant very early in life. It could be about them being unable to metabolise the nitrogen in the proteins in their food or that they cannot handle bilirubin, which is a breakdown product of the red blood cells; something that could result in jaundice and brain damage.
“We add a cell that can express the gene that is missing in these patients. If you can just get enough of these cells into the liver you can treat the disease without having to perform a whole organ transplantation”, says Stephen Strom.
Then of course it remains to be seen how long the treatment will last. It is evident that it will not last forever. In the mouse model, the cells hold up until the middle of the mice's lives, but whether this means that the cells in humans will last until the middle of the patient's life or just within a similar time span is something no-one knows.
“We don't know if we have to transplant new cells every year, every other year, every fifth year or less frequently. But even if we have to add new cells fairly often, this is trivial compared to an organ transplantation. This is like coming in for a vaccination or an infusion”, says Stephen Strom.
Treatment of congenital osteoporosis
Another trial treatment is “Boost Brittle Bones Before Birth”, BOOSTB4, which will start in January 2016 at Karolinska Institutet. The project involves children suffering from congenital osteoporosis, osteogenesis imperfecta, who are to be treated with stem cells. The children have a genetic defect in their production of collagen.
Collagen works as reinforcement rods in the bones. The mutation results in the collagen not working as it should. It interrupts the bone formation and leads to the cardinal symptom broken bones, says Cecilia Götherström, researcher at the Department of Clinical Science, Intervention and Technology at Karolinska Institutet and leader of the study.
The disease has different degrees of severity, where the most severely ill die before or just after delivery, while those who survive can have anything from a mild form that is barely noticeable to suffering 30 fractures a year. The disease is extremely rare and only one or two children are born with this condition in Sweden each year. It is discovered in the ultrasound examination taken by all pregnant women; the foetuses with this disease are smaller than normal and have short, bent bones as well as fractures.
In the study in question, the researchers will treat 30 children with stem cells from the livers of aborted foetuses that will then develop into bone cells that can produce collagen.
“We have seen that the cells from foetuses develop bones better than stem cells from adults and there is data that shows that when transplant cells prior to birth, it is easier to use foetal stem cells instead of cells from adults. We don't know why, but it could be that they hit the right spot in another way”, says Cecilia Götherström.
The study is about how safe the stem cell treatment is and how well it works, and also about how early treatment should be initiated for the best results. Half of the children shall receive stem cell transplantation while in the womb and the other half will receive the first transplantation after delivery.
New transplantations will then be done every six months in order to increase the effect. A setup that is based on experience.
“We think that the sooner you treat, the better the result, and likewise with performing the treatment several times. We have previously transplanted stem cells to a child prior to birth and she is 13 years old now. We have evaluated her progress all these years, and she has also received top-ups as we have seen that the effect seems to wane”, says Cecilia Götherström.
Transplanting stem cells to a foetus inside the mother's womb may seem like an incredibly advanced treatment, but it is not, according to Cecilia Götherström.
“It's an established technique that we use. It's the same method as used when giving blood transfusions to the child during pregnancy. All foetal therapy centres that can administer blood transfusions can also do this”, she says.
As the disease is so uncommon, the study is a European collaboration project that includes research centres in Britain, the Netherlands and Germany, as well as Lund University. The number of Swedish children in the study will also be quite small.
“We have counted on a maximum of three. We would also like to recruit children from Norway, Denmark, Finland and Latvia for example”, says Cecilia Götherström.
The study will run for five years and when it is completed the researchers will be able to say something about which theory is the best. The children will then be monitored for a further ten years for security reasons. But this is not about any kind of miracle treatment.
“It's important to remember that this is not a curing treatment, instead it changes a severe variant of the disease to a milder one. For a patient that otherwise would have suffered ten fractures a year, we may be able to help cut than figure in half. But even that would mean a large improvement in quality of life. These patients will normally only become one metre tall. After that, they stop growing. The first patient is still growing and is almost 1.2 metres tall now”, she says.
Using stem cells from aborted foetuses and injecting them into other ill foetuses is naturally a sensitive issue and not something Cecilia Götherström sees as a permanent solution, but this study focuses mostly on demonstrating that it works and that it is safe.
“I'm sure it's possible to find more optimised methods of doing this. If it turns out that the treatment works, we'll have to think about how to solve the issue of access to stem cells. This is just the first study so there's lots more that we can do in the future”, she says.
Cells can be transplanted to the eye
If Stephen Strom and Cecilia Götherström are going to treat small children and even unborn foetuses, Anders Kvanta, Senior Consultant at St. Erik Eye Hospital and Adjunct Professor at Karolinska Institutet, has an entirely different patient group in mind – the elderly.
The most common cause of loss of central visual acuity and reading vision in older people in the Western world is the age-related widespread disease macular degeneration. The eye disease is a result of the supporting cells behind the retina, the "retinal pigment epithelium" cells, slowly dying, which means that the retinal cells that support vision – the rods and cones – also die. The disease has two forms; a wet and a dry form. The wet form can nowadays be halted with drugs but 90 per cent of the patients have the dry version, which so far has no effective treatment.
“That's why the idea of trying to replace the dead cells by transplanting new healthy cells has come up”, says Anders Kvanta.
The idea is in the first stage to transplant new pigment epithelial cells that are to build up the support tissue and then try to repair dying visual cells. Anders Kvanta collaborates with Outi Hovatta, Professor in Obstetrics and Gynaecology, and Fredrik Lanner, researcher at Karolinska Institutet who extracts cells from embryonic stem cells.
“The natural thing is to start with these pigment epithelial cells as they are central to the emergence of the disease. Furthermore, stem cells are very susceptible to becoming this particular type of cell. Of all the cell types in the body, the retinal pigment epithelial cell is one of the easiest to create from stem cells”, says Anders Kvanta.
This is one of several reasons why the method is at an advanced stage. As early as 2012, American researchers tried injecting patients' pigment epithelium cells from embryonic stem cells and at the end of last year, Japanese researchers injected a patient with cells from induced pluripotent stem cells.
However, Anders Kvanta and Outi Hovatta claim to have significantly better cells with a higher degree of purity; something they can back up with the good results achieved with their rabbit model.
“We've managed to make the pigment epithelial cells lie perfectly in single cell layers, and once there they protect dying visual cells. We've got the cell layers to last for eight months, which is sensational as they are human cells transplanted to a rabbit”, says Anders Kvanta.
Conduct human trials
His plan is now to be able to conduct human trials with these cells in about a year and a half to two years. But this is just the first step in the process of actually being able to improve the patients' vision. For this it is also necessary to transplant photoreceptor cells; a feat which no-one has yet achieved.
“What we hope for with the transplantation of pigment epithelium cells is that we'll see a type of halting effect where vision is stabilised and does not deteriorate. We are working on photoreceptor cells as well but we haven't got as far in that area”, he says.
He says that the eye is a great organ to work with when it comes to replacing dead cells. There are methods for depicting what happens inside the eye, which also allegedly is less sensitive to cells foreign to the body, even though this is something that still needs to be completely proven. Anders Kvanta will use embryonic stem cells as a starting point for the pigment epithelium cells that he intends to transplant.
Another possibility is using induced pluripotent stem cells as a starting point for these cells. However, these have so far shown changes that risk causing tumours after transplantation. With a better technique of developing the cells, this risk has been decreased, but in principal he sees a safety advantage with the eye.
“The likely situation, if a tumour forms, is that is forms directly in the eye. And then it would be easier for us to see it. We have fairly few cells in the eye and we have very good control over the area we're injecting the cells into”, he says.
The final goal is to restore vision in older people who have suffered from macular degeneration. That this is achievable is something he has no doubts about.
“Absolutely. Considering how fast the development has been so far. In ten years we've gone from just having a vague notion of how this could be used to actually testing it on patients. In another ten years we'll have got much further and in 20 years we may have a vison-improving treatment. Fairly soon it will be possible to combine the treatment with photoreceptors”, says Anders Kvanta.
The other researchers also see the future potential in the treatments they work with. But Stephen Strom still wants to add a caveat.
“I'm very positive about the possibilities my research brings but I'm also a realist. I mean, we've already cured all diseases in mice – diabetes, cancer, cardiovascular diseases. But there's a fairly big step from our subjects with tails to all of us without tails”, he says.
Facts about stem cells
Stem cells are the source of all cells in the body. Here are the three types researchers use.
Embryonic stem cells
- Source: The immature embryo.
- Advantage: Great potential, can form almost all types of cells in the body (pluripotency).
- Disadvantage: Hard to access, must be extracted from an embryo the first week after the ovum is fertilised. It is also ethically controversial.
Mature stem cells
- Source: Body tissue from both children and adults.
- Advantage: Relatively easy to access.
- Disadvantage: Can only be developed into certain cells in certain tissue (multipotency).
- Example: Mesenchymal stem cells that can develop bones, cartilage and fat.
- Source: Common skin cells that are reprogrammed to become stem cells in a laboratory.
- Advantage: Unlimited access. Researchers can tailor-make stem cells for research. Pluripotent.
- Disadvantage: Still a risk factor of using them in treatments, may have undesirable qualities.
Text: Fredrik Hedlund, first published in the magazine Medical Science, no 4, 2015.