Find Out More: Hans Keirstead talks about hurdles in developing a new therapy One of the biggest hurdles in any stem cell-based therapy is coaxing stem cells to become a single cell type.
The vital process of maturing stem cells from one state to another type is called differentiation. Guiding stem cells to become a particular cell type has been fraught with difficulty. For example, stem cells growing in a developing embryo receive a carefully choreographed series of signals from the surrounding tissue. To create the same effect in the lab, researchers have to try and mimic those signals. Add the signals in the wrong order or the wrong dose and the developing cells may choose to remain immature—or become the wrong cell type Many decades of research has uncovered many of the signals needed to properly differentiate cells.
Other signals are still unknown. Many CIRM-funded researchers are attempting to differentiate very pure populations of mature cell types that can accelerate therapies. Find Out More: Mark Mercola talks about differentiating cells into adult tissues Once a researcher has a mature cell type in a lab dish, the next step is to find out whether those cells can function in the body.
For example, embryonic stem cells that have matured into insulin-producing cells in the lab are only useful if they continue producing insulin once transplanted inside a body. Likewise, researchers need to know that the cells can integrate into the surrounding tissue and not be rejected by the body. Scientists test cells by first developing an animal model that mimics the human disease, and then implanting the cells to see if they help treat the disease.
Researchers have to examine each of these possible outcomes. So, a stem cell therapy that treats this mouse model of cystic fibrosis may not work in humans. The promise of embryonic stem cells is that they can form any type of cell in the body. The trouble is that when implanted into an animal they do just that, in the form of tumors called teratomas.
These tumors consist of a mass of many cells types and can include hair cells and many other tissues. These teratomas are one reason why it is necessary to mature the embryonic stem cells into highly purified adult cell types before implanting into humans. Transplanted stem cells, like any transplanted organ, can be recognized by the immune system as foreign and then rejected. In organ transplants such as liver, kidney, or heart, people must be on immune suppressive drugs for the rest of their lives to prevent the immune system from recognizing that organ as foreign and destroying it.
The machine separates the stem cells from the rest of the blood, which is returned to the donor during the same procedure. This takes several hours, and may need to be repeated for a few days to get enough stem cells. The stem cells are filtered, stored in bags, and frozen until the patient is ready for them. The stem cells travel to the bone marrow, engraft, and then start making new, normal blood cells.
The blood of newborn babies normally has large numbers of stem cells. Cord blood can be frozen until needed. A cord blood transplant uses blood that normally is thrown out after a baby is born. After the baby is born, specially trained members of the health care team make sure the cord blood is carefully collected.
The baby is not harmed in any way. Even though the blood of newborns has large numbers of stem cells, cord blood is only a small part of that number. So, a possible drawback of cord blood is the smaller number of stem cells in it. But this is partly balanced by the fact that each cord blood stem cell can form more blood cells than a stem cell from adult bone marrow.
Still, cord blood transplants can take longer to take hold and start working. Some cancers start in the bone marrow and others can spread to it.
For these cancers to stop growing, they need bone marrow cells to work properly and start making new, healthy cells. Most of the cancers that affect bone marrow function are leukemias , multiple myeloma , and lymphomas.
All of these cancers start in blood cells. Other cancers can spread to the bone marrow, which can affect how blood cells function, too. For certain types of leukemia, lymphoma, and multiple myeloma, a stem cell transplant can be an important part of treatment. There are different kinds of stem cell transplants. They all use very high doses of chemo sometimes along with radiation to kill cancer cells. But the high doses can also kill all the stem cells a person has and can cause the bone marrow to completely stop making blood cells for a period of time.
In other words, all of a person's original stem cells are destroyed on purpose. But since our bodies need blood cells to function, this is where stem cell transplants come in.
So, transplanting the healthy cells lets doctors use much higher doses of chemo to try to kill all of the cancer cells, and the transplanted stem cells can grow into healthy, mature blood cells that work normally and reproduce cells that are free of cancer.
You'll usually need to stay in hospital for a month or more until the transplant starts to take effect and it can take a year or 2 to fully recover.
Read more about what happens during a stem cell transplant. Stem cell transplants are complicated procedures with significant risks. It's important that you're aware of both the risks and possible benefits before treatment begins. Read more about the risks of having a stem cell transplant. If it is not possible to use your own stem cells for the transplant see above , stem cells will need to come from a donor.
As of now, no treatments using mesenchymal stem cells are proven to be effective. There are, however, some clinical trials investigating the safety and effectiveness of MSC treatments for repairing bone or cartilage. Other trials are investigating whether MSCs might help repair blood vessel damage linked to heart attacks or diseases such as critical limb ischaemia, but it is not yet clear whether these treatments will be effective.
Several other features of MSCs, such as their potential effect on immune responses in the body to reduce inflammation to help treat transplant rejection or autoimmune diseases are still under thorough investigation. It will take numerous studies to evaluate their therapeutic value in the future. Clinical studies in patients have shown that tissue stem cells taken from an area of the eye called the limbus can be used to repair damage to the cornea — the transparent layer at the front of the eye.
However, this can only help patients who have some undamaged limbal stem cells remaining in one of their eyes. The treatment has been shown to be safe and effective in clinical trials and has now been approved by regulatory authorities for widespread use in Europe.
Limbal stem cells are one of only three stem cell therapies treatments utilising blood stem cells and skin stem cells being the other two that are available through healthcare providers in Europe.
Recently, human ESCs embryonic stem cells that meet the strict quality requirements for use in patients have been produced. One example is a clinical trial carried out by The London Project to Cure Blindness , using ESCs to produce a particular type of eye cell for treatment of patients with age-related macular degeneration AMD.
Early clinical trials for both conditions are now completed. Before these therapies can be offered to a wide range of patients, currently ongoing long term studies need to test them for their safety, security and efficiency.
If the initial clinical trials are successful in terms of safety and clinical benefit, ESC research may soon begin to deliver its first clinical applications.
The road to success will be a long and winding one as described in our graphic short story. In , the only clinical trial so far using iPSCs induced pluripotent stem cells was started.
However, the study to treat a degenerative eye condition, was soon put on hold due to safety concerns. In recent years stem cells were used as a powerful tool for establishing patient-derived disease models both to understand the molecular basis for disorders and to use them for drug development in a dish.
A lot of diseases are more complex and are caused by mutations in a number of genes at the same time. These are difficult to model, even with modern genome engineering techniques. This has implications for understanding how the diseases actually happen — researchers can watch the process in a dish — and for searching and testing new drugs. Here are a few more examples of diseases, which have been modelled using ESCs or iPSCs or where drug development using pluripotent stem cells is under way further information is given via the links and in the reference list below :.
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