Cell based therapies - pleuripotent stem cells
January 08, 2016
This is the third and final part of my blog related to the International Conference on Cell-based Therapies for MS that was held in November 2015. Today I will discuss pleuripotent stem cells
The term “pleuripotent” means that these cells are capable of growing into any tissue in the body. For example, they could become kidney, lung, brain or any other tissue. In humans, cells are pleuripotent up until the embryo is 32 cells in size (eight to 10 days after fertilization). After that, the cells are committed to being one particular type of tissue.
Technology has been developed so that cells from an adult animal can be reprogrammed to behave like these pleuripotent cells. These are called induced pleuripotent stem cells. This technique is only recently being applied to human cells. In the case of MS, we are most interested in replacing myelin, and the cells that produce myelin are called oligodendrocyte progenitor cells (OPCs).
OPCs are in the very early stages of research in MS. There are many questions that must be answered before these become available for treatment of MS. One of the most pressing issues is determining the best source of these cells.
Growing fetal pleuripotent stem cells in culture and nudging them to form OPCs is difficult because of the limited availability of these cells, as well as ethical issues regarding fetal sources. Inducing OPCs from other stem cells has not been perfected yet. Reprograming an adult cell from the patient so that it behaves as an OPC is not yet feasible. Much work is going on in this field and it is hoped that a good source of these cells might be available in the near future.
Another issue is to make sure that the OPC cell product is stable and reproducible. Safety measures must be put in place to assure that the cells are stable in culture, do not get genetic mutations or get contaminated with viruses.
It also has to be determined where the cells go and what they do after being given to patients. For example, do all of the OPCs go to the brain or do some go elsewhere in the body? Do these cells stay committed to forming myelin or do some spread to form tumors or cause other complications?
It must also be determined how the cells should be delivered. Is it sufficient to give the cells intravenously or do they have to be injected directly into the brain? How should the cells be prepared for administration?
Fortunately, progress is being made in answering some of these questions. Studies in animals are exploring the best sources of cells, how to administer them and how the cells should be prepared. A study by the New York State Consortium plans to explore results after injecting OPCs directly into the brain in a small number of patients. This first study will be very useful in guiding future development of this technology.