Once you start reading about stem cell therapies, it is very easy to get confused. No article will only use the term “stem cell”. Most will discuss a specific type of stem cell. Therefore, it is important to note that there are different kinds of stem cells, derived in different ways. As you find out about studies and clinical trials, it is good to know where the stem cells are coming from. There could be some ethical issues you want to consider, as could be the case with embryonic stem cells, for example. To help you navigate your way through the information you find, we listed the most important terms.
Glossary of terms
Adult stem cells: Stem cells can be found in about 20 places in the adult body including muscles, brain tissue, fat-storing connective tissue, bone, and skin to name a few. They are not as versatile as embryonic stem cells, but there are no ethical concerns. Taken from adults in small surgeries, they can be cultured and turned into the needed cells by adding appropriate growth hormones. It is even possible for doctors to derive stem cells for your treatment from your own body. This is called autologous stem cell therapy and contains the least risk of tissue rejection. However, it takes a few weeks to have them cultured in sufficient amounts. Therefore, they are not suitable for acute treatments after a stroke.
Allogenic: Stem cells from a healthy donor (includes embryonic stem cells and adult stem cells).
Autologous: Stem cells derived from your own body.
Clinical trial: An FDA approved study for the safety and efficacy of a treatment. Participation is always free of charge. Clinical trials come with the following labels:
- Double-blinded study: Neither researchers nor participants know who is assigned to which group. The reason for blind studies is to minimize and control for placebo effects.
- Open-labeled study: Study participants and researchers know who is having what treatment.
- Placebo group: Participants who are treated in exactly the same way as the treatment group, but do not receive the real therapy or medication. The more invasive the method of treatment is, the more ethical concerns arise (e.g., having a sham brain surgery, where only saline is injected).
- Single-blinded study: Study participants do not know what treatment group they are in, but the researchers do.
- Small-scale, dose-escalation: These are standard labels used in Phase I or early Phase II studies. A small number of participants receive different concentrations of the same drug.
- Randomized controlled study: Patients are assigned to either a treatment or a control group in a completely random way. Decisions on which group patients land in are made in a coin-tossing manner. This way, the experimenter has the least chance to influence results. Phase I trials are never randomized because they aim to assess the safety and tolerability of a treatment with only a few participants and have no control group.
Delivery methods of stem cells to the brain
- IV: Intravenous delivery is when the stem cells are administered through the veins. This method is safe, easy, and standard in all hospitals and most doctors’ practices. That means, you probably wouldn’t even need to go to a hospital to get treated. However, animal and human studies have clearly shown that stem cells administered in this way neither survive or start to form new stem cells. Positive effects reported are probably due to the systemic release of so-called neurotrophic factors. Neurotrophic factors include proteins and hormones that can cause changes in the immune and anti-inflammatory responses.
- Brain surgery (intracerebral, IC): Brain surgery is always risky. Any inflammation in the brain can destroy other tissue. However, devices for stem cell delivery are small and designed to avoid any damage of brain tissue during insertion. As with all surgeries, keeping the instruments and environment sterile is the number one priority, preventing infection and inflammation. During this method, a doctor injects stem cells either into brain tissue close to the site of injury or into ventricles (normal liquid-filled holes within the brain). With this method, cells can survive up to one month. Beneficial results might still stem primarily from released growth factors and hormones.
- Intra-arterial (IA): This is a safe and easy way to deliver stem cells through an artery. The procedure is very similar to IV-delivery, but a catheter is inserted into a vessel that transports blood away from the heart to organs (artery, as opposed to a vein which transports blood towards the heart). Some studies show that stem cells survive to a limited extent. As there are only 6 studies with 57 patients so far using this method for stem cell therapy, more studies are needed to test this method.
Watch this video for a first explanation of what stem cells are.
Embryonal pluripotent stem cells: The cellular all-rounders. If a fertilized egg cell matures into a blastocyst (a ball of unspecified cells), stem cells develop inside. Treated with certain substances like growth hormones, they can turn into any cell-type.
Induced pluripotent stem cells (IPSCs): By genetically programming cells with specific functions, researchers can turn them into stem cells. There are no ethical concerns since no embryo is destroyed to derive them. The disadvantage is that foreign genes are inserted into those cells, potentially harming other genes in this process. Therefore, there is a danger that these cells turn into cancer cells. However, in 2009 researchers could derive stem cells simply by bathing them in certain proteins.
Mesenchymal stem cells (MSC): Multipotent stem cells derived from certain (connective) tissue, including bone marrow, umbilical cord, or fat-storing connective tissue.
Multipotent: The ability of a stem cell to turn into only certain cell types.
Pluripotent: The ability of a stem cell to turn into any cell type.
What other terms would you like to know?
If you happen to stumble upon more terms you don’t understand while browsing stem cell treatment for stroke, please don’t hesitate to ask. We can add to our glossary accordingly. We know this can be confusing. By reaching out to us, you are helping other patients in the process.
You might also have a look here: http://www.closerlookatstemcells.org/patient-resources/stem-cell-glossary