Multipotent Stem Cells
Stem cells remain an exciting area of research but the concept is often still a confusing one for the public. Complicating the complex topic of stem cells is the separation of stem cells into various categories. One such category is multipotent stem cells and it carries traits that separate it from totipotent and pluripotent stem cells.
What Are Multipotent Stem Cells?Multipotent stem cells have the same basic features of all stem cells. As with all stem cells multipotent stem cells are unspecialized cells that have the ability to: Self-renew for long periods of time and differentiate into specialized cells with specific functions
A multipotent stem cell can give rise to other types of cells but it is limited in its ability to differentiate. These other types of cells are also limited in numbers. Examples of multipotent stem cells include those in the brain that give rise to different neural cells and glia or haematopoietic cells, which can give rise to different blood cell types, but they can't create brain cells. Bone marrow also contains multipotent stem cells that give rise to all blood cell types but not other cells.
Hence, adult stem cells are considered multipotent because their specialization potential is limited to one or more cell lines. However, a multipotent stem cell known as a mesenchymal stem cell can give rise to several cell types. This particular stem cell has been found to give rise to bone, muscle, cartilage, fat, and other similar tissues.
Multipotent stem cells are essentially committed to produce specific cell types. They vary from stem cells such as pluripotent ones which can give rise to almost any cell type, or totipotent ones which can give rise to any cell, including the potential to create a complete organism. Pluripotent stem cells actually undergo specialization into multipotent stem cells, and then multipotent stem cells give rise to cells with a specific purpose and function. Multipotent stem cells can be likened to a family-although they do give rise to different cells, the cells themselves are within a certain family and therefore, are closely related.
Where Are Multipotent Stem Cells Found?Multipotent stem cells are found in the tissues of adult mammals. It is thought that they are in most body organs, where they replace diseased or aged cells. Thus, they function to replenish the body's cells throughout an individual's life.
Benefits of Multipotent Stem CellsThere are numerous benefits and uses to multipotent stem cells. Since multipotent stem cells are derived from pluripotent stem cells, these stem cells have already partially differentiated and they continue specializing as they develop. They haven't yet been identified in all adult tissues but new research is regularly indicating a discovery of multipotent adult stem cells in new body tissues. Multipotent adult stem cells are particularly useful in transplants. They can be isolated, albeit often with difficulty, from a person's tissues and then guided to develop into a certain type of cell, before being transplanted back into the same patient. This avoids the immunological challenges of pluripotent foetal stem cell usage, where a patient's immune system could potentially reject a 'foreign' tissue. Another benefit is that the ethical debate and controversy involved in extracting foetal stem cells is avoided, because neither foetal tissues nor an aborted embryo are necessary for treatments.
A key type of multipotent stem cell that research is currently focused on is a neural cell. Neural cells give rise to nerve cells, which don't have the same turnover rate as do other cell types such as blood. Neural cells have now been isolated from the adult brain and foetal brain tissues, which means that these cells may then be triggered to divide, or differentiate, into new nerve cells. The implications for treating brain and spinal cord injuries are enormous and could essentially provide a reversal of these conditions.
Challenges And Current Multipotent Stem Cell ResearchOne challenge that scientists must address is whether or not a multipotent cell could actually be triggered to specialize into a cell type different from that of the original tissue. Current research on multipotent stem cells, however, is now contradicting the belief that multipotent adult stem cells are restricted to giving rise to the cell types corresponding to their specific tissues. The stem cells appear to be able to go beyond the previously believed boundaries for producing specific cell types, but they do so infrequently and only under narrow conditions. To understand how this occurs, the issue of stem cell plasticity has to be considered. Stem cell plasticity is a term used to describe the phenomenon of adult stem cells from one tissue generating the specialized cells of another tissue. For a long time, it has been believed that adult multipotent stem cells are organ-specific, so they only give rise to cell types in their residing tissues. This possible finding of plasticity has enormous potential for stem cell therapy. It means that if scientists can re-focus this differentiation, a blood stem cell could, for instance, be used as a replacement for heart or nervous system tissues. There are still, however, numerous challenges that must be overcome before this idea can be put into practice. For now, it is more feasible that multipotent stem cells will have practical use in those tissues from which they are isolated.
Multipotent adult stem cells have also not been found in all of the body tissues, which means that use of pluripotent foetal stem cells is the only opportunity to obtain some types of tissue. The difficulty in isolating large quantities of multipotent cells from adult tissues is an additional challenge that must be overcome. In addition, the current time required for a multipotent stem cell to mature in a laboratory setting is quite lengthy but still necessary to provide sufficient cells for the treatment. Many patients are in dire need of the transplanted cells and simply can't stay alive long enough to receive the treatment. If the cells are intended to treat a disease that is genetically based, then it's likely that the isolated cells will also carry this genetic error and are ultimately rendered useless.
It's clear that there are many challenges to overcome before multipotent cells can be safely and regularly used, but their benefits are numerous and hold promise for treating disease. Their avoidance of the ethical issues associated with pluripotent and totipotent foetal cells also means that approval for research and therapeutic use is likely to be a more timely process.