- Stem cell therapy for epilepsy is a possible treatment option in the future.
- Stem cell therapy may prove useful for:
- Improving seizure control
- Improving memory issues
- Stem cell therapy is not yet approved for the treatment of epilepsy- the safety and effectiveness of such treatment has to be thoroughly studied and approved by the FDA.
There are many exciting areas in epilepsy research. One topic of great interest is the use of stem cells to treat seizures. Although stem cell research related to epilepsy is in its early stages, preliminary data would suggest promise for this treatment option. The writing of this article has been prompted by several people in clinic and on our Facebook page asking for information on stem cell therapy for epilepsy. The goals of this article are to: 1) provide a basic understanding of stem cell therapy; and 2) to review stem cell therapy in epilepsy.
WHAT IS A STEM CELL? HOW DO STEM CELLS STOP SEIZURES?
When an organism (a human, mouse, etc) is developing, the organism will start as a single fertilized cell. This cell will begin dividing. As the cells divide, groups of cells are programmed to form parts of the body- heart, lungs, skin and brain, for example. These early dividing cells are called stem cells. Stem cells are cells that have the ability to develop into a wide variety of cell types. Some stem cells have the potential to become any cell type in the body. Cell types include muscle cells, skin cells or brain cells, such as neurons. In addition, stem cells have the special ability to renew themselves for long periods of time.
It has been shown that stem cells can be transplanted into the brain and produce functioning neurons. One strategy for the use of stem cells in neurological conditions is to transplant stem cells into abnormally functioning brain tissue—this will allow the stem cells to develop into normally functioning brain cells and produce normal brain function.
Illustrative case: Consider a patient with a small area of scarring in her left temporal lobe. Her seizures are coming from that area of scarring. This area of scarring has very abnormally functioning neurons. Properly functioning neurons are supposed to have a nice normal flow of electricity, from one neuron to the next. In our patient’s area of scarring, the neurons are electrically abnormal—the electrical charge is way too high. This abnormal electrical activity can lead to spreading electrical charge that results in a seizure (see our article “What is a seizure?” for details). Now, imagine that you could place stem cells in her brain in the area of scarring. This would result in relatively normal cells replacing the abnormal cells. Instead of excessive electrical activity, you would have normal electrical activity. Because the neurons are now functioning properly and not causing excessive electricity, the seizures are stopped! That is the hope of how stem cells could work.
TYPES OF STEM CELLS
Embryonic stem cells: Cells derived from embryos. An embryo is defined as a young animal (human, mouse, etc), early in the stages of development within the womb.
Adult stem cells: The study of adult stem cells for clinical use has been prompted for several reasons, including the ethical issues related to the use of embryonic stem cells. In 2006/2007, researchers identified conditions that would allow some specialized adult skin cells to be “reprogrammed” into stem cells. This is almost like turning the clock back in time—adult cells are reverted to an early stage in cell development—the stem cell. The stem cell could then be used to create a variety of different types of cells (heart cells, brain cells, etc).
This discovery leads to a great hope! Imagine this futuristic treatment plan: 1) patients could have some of their own skin cells removed; 2) skin cells are reverted to stem cells; 3) these stem cells are placed into the patient’s brain – they become normally functioning brain cells and replace the neurons that caused seizures; 4) seizures are stopped! Obviously, this is not reality at this time—but the potential is very exciting!
POSSIBLE WAYS THAT STEM CELLS COULD HELP PEOPLE WITH EPILEPSY (Shetty, Stem Cells, 2007):
- Replace neurons that are lost or dysfunctional- to stop seizures: It has been shown that patients with chronic epilepsy can have a reduced number of neurons in the area where their seizures originate (= the seizure focus). Also, the neurons in the region of the seizure focus may not function correctly – for example, they may be overly electrically active. This abnormally high electrical activity is what can produce seizure activity. Stem cells could be transplanted into the area of the seizure focus and replace the lost or abnormal neurons. The stem cells could be programmed to become normally functioning neurons. By replacing the abnormal function with the normal function, the potential for seizure activity could be potentially erased. This method to use stem cells is similar to the example described above (see above section: Illustrative case).
- Replace neurons that are lost or dysfunctional- to help memory: Some patients with epilepsy have memory complaints. There are a multitude of possible reasons for people with seizures to have memory issues- medication side effects, seizure activity, and mood problems are commonly identified causes. Some patients have memory problems related to losing neurons or dysfunctional neurons in the area of the seizure focus. By replacing the lost or dysfunctional neurons with normally functioning neurons derived from stem cells, memory problems could be potentially significantly improved.
- Transplant stem cells that have the ability to produce a chemical to stop seizures: Stem cells can be programmed to become neurons that produce a neurotransmitter called GABA. This is a chemical which can stop the overly active neuronal function that can produce seizures. GABA results in inhibition of neurons (opposes the excitation of dysfunctional neurons). If stem cell derived neurons could produce a high quantity of GABA and were placed in the area where seizures started (seizure focus), the seizures could be stopped before they started!
SAFETY ISSUES AND STEM CELLS (Naegele, Neuropharmacology, 2010)
There are several challenges that need to be worked out before stem cell therapy will be widely considered as safe:
- Stem cells can lead to the development of tumors. As noted above, stem cells have the ability to renew themselves for a long-term. This is a good thing- by continuously dividing, stem cells can produce a supply of new cells for therapy. An important negative- the long-term dividing process can lead to the development of tumors, in some cases. This issue is being studied. This issue needs to be considered safe before widespread clinical use will be possible.
- Stem cells can lead to rejection by the body’s defense system. When stem cells are placed into the brain, there is the potential for the body’s immune system to have a reaction to the stem cells- as if the stem cells are an infection that the body needs to get rid of. This can lead to the stem cells being cleared away by the body’s immune system. Obviously, the stem cells will not be able to provide therapy if this occurs. Again, this issue is being studied.
CAN CLINICIANS PRESCRIBE STEM CELL THERAPY FOR EPILEPSY NOW?
The answer is no. Essentially all the research on stem cell therapy for epilepsy has been carried out in animal models (rodents, for example). There are currently no FDA approved stem cell therapies for epilepsy. In the coming years, large scale human studies using stem cell therapy for the treatment of epilepsy will hopefully be carried out. Such studies will look at the safety and effectiveness of such treatment. These studies will be necessary to obtain FDA approval- so that patients can receive stem cell therapy in the clinic setting. An important question is- when will stem cell therapy be approved by the FDA? The answer to this question is unknown, although experts in the field are hopeful for significant advances in the next 10 years.
Stem cell therapy is a promising treatment for patients with epilepsy. More studies need to be performed to determine the safety and effectiveness of this treatment. Hopefully, in the not too distant future, stem cell therapy could be offered as a treatment for our patients.
Naegele J, Maisano Xu, Yang Jia, Royston S, Ribeiro E. Recent advancements in stem cell and gene therapies for neurological disorders and intractable epilepsy. Neuropharmacology 2010;58:855-864.
Riban V, Fitzsimons HL, During MJ. Gene therapy in epilepsy. Epilepsia 2009;50:24-32.
Shetty AK, Hattiangady B. Concise review:prospects of stem cell therapy for temporal lobe epilepsy. Stem Cells 2007;25:2396-2407.
Stem Cell Information: NIH resource for stem cell research http://stemcells.nih.gov