Ever since late '90s and after all these great advances in that promising field of research, stem cells have become a very common term to everybody.
But, sometimes we hear about many different classifications, which may confuse things a bit. I would like to try to make things a little more clear, with a few words for each category...
So, stem cells can be classified into 4 different categories...
All of them keep the main stem cell traits, which are self-renewal for long periods of time and differentiation into cells with specific functions. But, they are further classified into Totipotent, Pluripotent, Multipotent and Unipotent, basically according to their differentiation ability.
Totipotent Stem Cells have the ability to differentiate into all the cell types of the human body. A totipotent cell is created after the fusion of a sperm and an egg cell, which form the zygote. Cells produced by the few first divisions of the zygote, are also totipotent. The totipotency of the zygote remains for about 4 days, till the formation of the blastocyst, when totipotent cells differentiate into pluripotent. The therapeutic value of totipotent SC is enormous, as they can produce any cell in the body, even placental cells.
Pluripotent Stem Cells (or "true" SC as often called) are descendants of totipotent SC and they have the ability to differentiate into almost any cell of the body. In order to keep their pluripotency, these cells should be isolated during early embryonic development, otherwise they can only differentiate into certain types of cells.
Pluripotent SC are further divided into 3 categories:
Examples of multipotent stem cells include cells in the brain that can produce neural cells or glia and haematopoetic stem cells that can further differentiate into red blood, white blood cells, platelets, etc. Multipotent SC, actually derive from pluripotent SC that undergo specialization into multipotent ones.
Unipotent Stem Cells that are found in adult tissues and they arise from multipotent stem cells. They have the lowest differentiation potential, as they can only produce one type of cell or tissue, but they still maintain their self-renewal ability, which distinguishes them from non stem cells. Thus they still have therapeutic potential in treating injuries and several diseases. Skin cells are the most abundant unipotent stem cells.
According to my first post on Latest Advances on Stem Cell research, scientists made it possible to produce functional cardiomyocytes from skin cells, by producing the Induced Pluripotent Stem (iPS) cells with the viral insertion of 4 transgenes into skin fibroblasts, a fact that makes great promises for the future treatment of major pathologic conditions.
For further reading: Explore Stem Cells, Wikipedia
So, stem cells can be classified into 4 different categories...
All of them keep the main stem cell traits, which are self-renewal for long periods of time and differentiation into cells with specific functions. But, they are further classified into Totipotent, Pluripotent, Multipotent and Unipotent, basically according to their differentiation ability.
Totipotent Stem Cells have the ability to differentiate into all the cell types of the human body. A totipotent cell is created after the fusion of a sperm and an egg cell, which form the zygote. Cells produced by the few first divisions of the zygote, are also totipotent. The totipotency of the zygote remains for about 4 days, till the formation of the blastocyst, when totipotent cells differentiate into pluripotent. The therapeutic value of totipotent SC is enormous, as they can produce any cell in the body, even placental cells.
Pluripotent Stem Cells (or "true" SC as often called) are descendants of totipotent SC and they have the ability to differentiate into almost any cell of the body. In order to keep their pluripotency, these cells should be isolated during early embryonic development, otherwise they can only differentiate into certain types of cells.
Pluripotent SC are further divided into 3 categories:
- Embryonic Stem Cells, which exist in the inner mass of the blastocyst after the 4th day of fertilization. The isolation of them is a great ethical issue, as it can cause harm to the embryo.
- Embryonic Germ Cells, that are being isolated from early cells in aborted foetuses.
- Embryonic Cancer Cells, which can be isolated from tumours that sometimes occur in the foetus.
Examples of multipotent stem cells include cells in the brain that can produce neural cells or glia and haematopoetic stem cells that can further differentiate into red blood, white blood cells, platelets, etc. Multipotent SC, actually derive from pluripotent SC that undergo specialization into multipotent ones.
Unipotent Stem Cells that are found in adult tissues and they arise from multipotent stem cells. They have the lowest differentiation potential, as they can only produce one type of cell or tissue, but they still maintain their self-renewal ability, which distinguishes them from non stem cells. Thus they still have therapeutic potential in treating injuries and several diseases. Skin cells are the most abundant unipotent stem cells.
According to my first post on Latest Advances on Stem Cell research, scientists made it possible to produce functional cardiomyocytes from skin cells, by producing the Induced Pluripotent Stem (iPS) cells with the viral insertion of 4 transgenes into skin fibroblasts, a fact that makes great promises for the future treatment of major pathologic conditions.
For further reading: Explore Stem Cells, Wikipedia
1 comment:
Very nicely done! Thanks for the super explanation! :)
Best wishes,
Tara
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