MS is currently classified as an autoimmune disease where one’s own immune cells attack the brain and spinal cord. These attacks can cause damage to the myelin, the protective layer that wraps the nerves, and injury within the brain and spinal cord. This leads to the many symptoms that are experienced by individuals living with MS. Current disease-modifying therapies are not always efficient at halting disease progression or able to promote repair, therefore stem cell-based therapies have generated interest. The research into stem cell use in MS focuses on two main ideas. First, replace disease causing immune cells with new immune cells that will not attack the brain and spinal cord. Second, replace the injured cells and repair damage to the brain and spinal cord. Below we will discuss stem cells and the current research into their use.
What are Stem Cells?
Stem cells are very unique; unlike regular cells, stem cells have the potential to develop into many different cell types in the human body like heart, muscle, or brain. The earliest observation of stem cells can be found in the human embryo; these are known as embryonic stem cells. We also retain stem cells into our adulthood; these are known as adult stem cells. Adult stem cells can be found in a variety of places including the bone marrow and brain, and they work to replenish different cell types in our body. There are different categories of adult stem cells and some of these are being explored as therapies.
The Different Types of Stem Cells
Haematopoetic stem cells (HSCs), and mesenchymal stem cells (MSCs) are two categories of stem cells that have potential to treat MS. HSCs are an immature cell that can develop into all types of blood cells, including white blood cells or immune cells, red blood cells, and platelets. These stem cells are found in the blood and the bone marrow and are called autologous when they are obtained from the same individual who will receive the transplant.
MSCs are an immature cell that comes from connective tissue, which is a group of cells that maintain the form of the body and its organs and provide internal support. These stem cells are traditionally found in the bone marrow; however, they do not have the capacity to make blood cells. They can also be found in a variety of other tissues including fat, umbilical cord blood, skin, and muscle. MSCs can become bone, cartilage, fat cells, connective tissue, and muscle. Laboratory studies of stem cells has enabled scientists to advance research and given the restorative capacity of stem cells, their potential in treating diseases has grown. Each of the above categories of stem cells is currently being explored as potential therapeutic options and we will discuss each below.
Immunoablation followed by autologous haematopoietic stem cells transplantation (I/AHSCT)
This treatment destroys the immune cells that are attacking the brain and spinal cord, and replaces them with the individuals own HSCs. The rationale behind this treatment is to reconstruct the immune system with cells that are not programmed to attack the brain and spinal cord. Many studies have shown that after treatment, there was a reduction in the aggressive cells (Muraro et al., 2005, 2014; Darlington et al., 2013; Arruda et al., 2015) Muraro et al., 2014), however some studies did detect a re-emergence of self-attacking cells (Darlington et al., 2013).
The available evidence suggests that this treatment can suppress immune attacks, however it is uncertain whether the benefit-risk-cost is better than other available DMTs.
Mesenchymal Stem Cell Therapy
The rationale behind this treatment is using these cells to help repair damage in the brain and spinal cord. These cells have been shown to promote myelin repair, reduce scar formation, reduce nerve loss, and supress immune activity. Some studies suggest that MSCs do not survive long after transplantation and that repeated administration would be necessary. However, most MSC therapies are still in early clinical trials, which will help clarify whether they can be used as a successful treatment. The effective dose of MSCs is not known and there is a need for quality and safety control which should aid caution in research into this treatment.
Clinical Trials: Bonab et al. (2012) Cohen et al. (2017) Connick et al.(2012) Karussis et al.(2010) Li et al.(2014) Liang et al. (2009) Llufriu et al. (2014) Lublin et al. (2014) Odinak et al. (2011) Rice et al.(2010) Riordan et al. (2009) Yamout et al. (2010)
Written by Alex Palmer and Trisha Lichtenberger