Totipotent Stem Cells
You may already be familiar with the basics of stem cells but perhaps you weren't aware that there are different types, or potencies of stem cells.
Totipotent stem cells are one of the most important stem cells types because they have the potential to develop into any cell found in the human body. In human development, the egg cell in a woman and the sperm cell from a man fuse together to form a single cell called the zygote. The zygote divides numerous times and forms cells that are the precursors to the trillions of cells that will eventually constitute the human body.
It may sound rather complex and in a sense it is, when you consider that a simple cell has the potential to develop into a specialised one with a specific job in the body. It is simple, however, in that it's a clear sequence of events that begins with an egg cell and a sperm cell. The zygote from that fusion of an egg cell and a sperm cell then begins cell divisions that are capable of forming the entire human body. It is these cells that are totipotent, so called because their potential is 'total.'
What Happens to the Zygote?Totipotent stem cells are perhaps the most versatile of the stem cell types. As explained, a totipotent zygote cell is created when a single celled sperm and egg unite. This totipotent fertilised egg has the potential to give rise to virtually all human cells, such as nerve or heart. It is during the early cell divisions in embryonic development that more totipotent cells are produced. Within several days, these totipotent cells divide and create replicas, therefore producing more totipotent cells. It is after approximately four days that the cells begin to specialise into pluripotent cells, which can go on to specialise further but can't ever produce an entire organism as totipotent cells can. Basically, the pluripotent stem cell can do everything the totipotent one can except for creating an entire organism.
When Does a Totipotent Stem Cell Change?A fertilised egg has totipotency, or total potential for about four days. Days after fertilisation, however, the totipotent stem cell divides and then matures to cause more specialised stem cells called pluripotent stem cells. Like totipotent stem cells, pluripotent stem cells can self-renew and give rise to trillions of cells in the body.
What are the Special Qualities of a Totipotent Stem Cell?The earlier stage foetal stem cells are totipotent because:
- They have the ability to become any cell type in a fully developed human
- They have the ability to replicate in unlimited numbers without losing their total potency
Benefits of Totipotent Stem CellsAll stem cells have the potential to develop into different cell types, but totipotent cells can develop into any cell type, which makes them ideal for cell and gene therapies as well as tissue engineering for transplants and replacement of diseased cells. This means that the therapeutic value of totipotent stem cells is enormous. By learning about the process of division, we can find out what goes wrong in disease states and then investigate ways to prevent diseased cell production and division.
A formidable challenge is for researchers to appease the ethical concerns around the harvesting of totipotent foetal cells. This is balanced by supporters who cite the huge range of benefits to those suffering from disease. For now, there doesn't appear to be an answer to satisfy all members of the public as well as scientists and government agencies. The promise of effective treatments or even a cure for many debilitating diseases is, however, reason enough to search for treatments with totipotent stem cells that everyone can live with.