Stem cells are cells in the body that can mature into specialized cells that serve a specific function. They are also able to produce exact copies of themselves. There are two main types of stem cells: embryonic stem cells and adult stem cells. Embryonic stem cells are found in the developing embryo and can mature into most types of cells in the body. The incredible flexibility of these stem cells highlights their usefulness for tissue healing and regeneration; however, there exists ethical debate over the use of stem cells from embryos. Adult stem cells are found in some adult tissues and organs including the bone marrow, skin, blood and brain. Adult stem cells are not as flexible as embryonic stem cells and are therefore more limited in terms of the types of cells they mature into.
The unique properties of stem cells makes them promising candidates for treatments that can slow MS disease activity and repair tissue damage in the central nervous system. Currently, there are no approved stem cell therapies for MS, but encouraging research is underway to determine how stem cells work and whether the use of stem cells to treat people with MS is safe and effective.
Stem cells can be injected into the body in different ways. They can be administered intravenously (an injection into the vein), intrathecally (an injection into the space around the spinal cord) or intraparaenchymally (an injection into the brain). In addition to ethical concerns surrounding the use of stem cells, legitimate health concerns exist as well. Stem cell treatments can be invasive and risky procedures, as these cells
have the potential to develop into tumours.
Below are some applications for stem cells that are currently being tested for MS.
Hematopoietic Stem Cells
Hematopoietic stem cells (HSC) are found in bone marrow, blood and umbilical cord. These stem cells are capable of maturing into all cells that comprise the blood and immune system. They have been used for many years to treat leukemia, lymphoma and blood disorders. HSC transplant is a risky procedure with a reported 1-2% death rate. HSC transplants have been experimentally tested in people with aggressive forms of MS who are unresponsive to other treatments and have a poor prognosis. The primary objective for this type of transplant is to reboot the immune system which is thought to be causing damage the nerve cells in MS. The procedure involves collecting stem cells from an individual’s own bone marrow and then exposing them to chemotherapy to deplete the immune system. The stem cells are then reintroduced into the body where they mature into new immune cells. The goal of the procedure is to provide the person with a new, healthy immune system that will no longer attack myelin. HSC therapy is an aggressive treatment, and thus researchers are focused on lower intensity approaches in an effort to reduce side effects and make the treatment suitable for more people with MS.
The MS Society of Canada and MS Scientific Research Foundation funded a clinical trial involving HSC transplants, led by Drs. Mark Freedman and Harry Atkins from the Ottawa Hospital Research Institute. For more information see Canadian Bone Marrow Transplantation (BMT) Trial.
Mesenchymal Stem Cells
Mesenchymal stem cells (MSC) are found in many places in the body including the bone marrow, skin and fat. MSCs have been demonstrated to suppress inflammation and repair nerve tissue, making them attractive candidates for MS treatment.
Animal studies are underway examining the potential of MSC therapy to aid in brain repair. In one critical study led by Dr. Robert Miller from Case Western Reserve University, mice with MS-like disease were given human MSCs. The treatment resulted in the improvement of their MS-like symptoms and showed signs of brain repair and functional recovery. Dr. Dimitrios Karussis and colleagues published findings from a phase I/II clinical trial examining the safety and feasibility of MSC therapy in 15 people with MS. Participants demonstrated improvement over six months following treatment.
The discovered potential of MSC in treating
MS has culminated in the launch of MESCAMS (
MEsenchymal Stem cell
CAnadian MS patients), a phase II clinical trial
that is funded in part by the MS Scientific Research Foundation, Research
Manitoba, and A&W Food Services of Canada Inc. Spearheaded by Dr. Mark Freedman (Ottawa
Hospital Research Institute, University of Ottawa), principal investigator (PI)
at the Ottawa site and Dr.
James Marriott (University of Manitoba), PI at the Manitoba site, MESCAMS
is part of an international mesenchymal stem cell research effort encompassing nine
countries. For more Information see
MEsenchymal Stem cell therapy for CAnadian MS patients (MESCAMS).
Neural Stem Cells
Neural stem cells (NSC) are found in the brain and are able to mature into various types of brain cells including neurons,
oligodendrocytes, and astrocytes. NSCs may protect the brain and modulate the immune system. Early clinical trials in non-human primates demonstrated that treatment with NSCs benefitted the progression of an MS-like disease. Clinical trials in humans are required to determine the safety and efficacy of NSC
As demonstrated by the examples above, there is a vast array of research taking place which will provide answers about the use of stem cells to treat MS. Early results published thus far are promising. However larger, longer-term, controlled studies are needed to determine if stem cell therapies are safe and effective. Results of human clinical trials will make it possible to determine what kind of stem cells can be used, optimal delivery methods, and which forms of MS may benefit from the different stem cell procedures.
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- Holloman, J.P. et al. The development of hematopoietic and mesenchymal stem cell transplantation as an effective treatment for multiple sclerosis. Am J Stem Cell. 2013; 2: 95-107.
- Fassas A, et al. Long-term results of stem cell transplantation for MS: a single-center experience. Neurology. 2011; 76(12):1066-1070.
- Inoue M et al. Comparative analysis of remyelinating potential of focal and intravenous administration of autologous bone marrow cells into the rat demyelinated spinal cord. Glia. 2003; 44 (2):111–118.
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- Darling PJ et al. Diminished Th17 (Not Th1) Responses Underlie Multiple Sclerosis Disease Abrogation after Hematopoietic Stem Cell Transplantation. Annals of Neurology, 2012 Oct 11.
- Bai L et al. Hepatocyte growth factor mediates MSCs stimulated functional recovery in animal models of MS. Nature Neuroscience. 2012; 15(6): 862-870.