STEM CELLS
What are stem cells?
They are immature cells able to reproduce and differentiate themselves in various tissues. They are also called mother-cells. They can be:
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Embryonic: |
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They are able to reproduce quickly, giving origin to all types of differentiated tissues. Adults: |
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Mature cells that reproduce more slowly, the most well-known being the ones taken from the bone marrow, and they are only able to generate some types of differentiated tissues. |
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The fertilization of the ovum by the spermatozoon initiates a sequence of cell reproductions that builds up a group of cells with characteristics that are very peculiar. While reproducing, they give origin to identical cells and, from a certain stage, are able to originate any type of tissue in the organism and, eventually, the different organs. Hence, the name embryo stem cells. It is worth highlighting that the two characteristics mentioned (reproduction of identical cells and differentiated cells) constitute the core research interest in embryo stem cells. These cells can play key role in the treatment of any variety of tissue, in the substitution of the damaged cells for other cells of the same differentiation, but with total vitality. Unlike the stem cells, the already differentiated cells reproduce themselves with their own specificities, and thus as they reproduce themselves the cells of the oral mucous membrane generate cells of the oral mucous membrane, exclusively. |
As concerns the capacity to originate different species of tissue, the stem cells can be qualified as:
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Totipotent: |
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They are able to reproduce quickly, giving origin to all types of differentiated tissues. Adults: |
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The embryonic stem cells that can develop into any type of tissue, including the placenta, are denominated totipotent-embryonic. They make up the first group of up to 32 cells, and develop in the first 72 hours after fertilization of the ovum. At this point, no differentiation of specificic tissue can be made in this cellular group. any differentiation of specific tissue. The development of the placenta and its adnexa only occur when these totipotent cells are implanted into the uterus. |
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Multipotent: |
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When forming a group of 64 cells, the embryonic cells, from the fifth or sixth day after the fertilization, are able to transform themselves in any type of tissue, except the placenta, and they are denominated multipotent cells. |
Unipotent
Adult-type stem cells are found in organs that are already formed, such as the nervous system, and give origin to only one type of tissue, and whose likely function is to repair certain tissues, but in the bone marrow the function of the adult stem cells is to maintain the level of certain figured elements of the blood requiring constant substitution.
Oligopotents
Adult stem cells that are able to originate more than one type of tissue are called oligopotents and are found, for example, in intestinal tissue.
What makes the embryonic cells to transform themselves into each type of tissue?
There are studies that identify the differentiation factors, which as they are put into stem cell cultures, they determine the cells to differentiate into a given tissue.
Another possibility under investigation: would stem cells, when in contact with a differentiated tissue, transform themselves into that very differentiated tissue? For example: can adult stem cells, obtained from umbilical cord blood, or bone marrow, when put in contact with a certain tissue, turn into the cells of this very tissue? The answer to this question is fundamental for the development of cell therapy. Multipotent embryonic stem cells can, with absolute certainty, do it.
Adult stem cells are expected to be able to reproduce a specific tissue as they reproduce themselves while in contact with it. Will the administration of an injection of stem cells from bone marrow in the myocardium produce the formation of new vessels to irrigate the cardiac muscle, or originate a new cardiac musculature to substitute harmed cells, or carry out both alternatives?
Cell Therapy
As an example of an effective, well-established routine method of cellular therapy, we have the bone marrow transplant for the treatment of leukemia. In this procedure, the donator's bone marrow provides unipotent stem cells that will produce new healthy blood cells. What can be expected?
It is expected that harmed cells, or those with little functional effectiveness, of the most varied categories, can be replaced for younger cells within any single organ of our body, which are induced to carry out the tasks of the original cells. Seemingly, the reach of this new therapeutic possibility achieves unprecedented objectives. However, researches are still at an early stage. It is necessary to demonstrate various know-how and techniques that are still incipient. The path is promising and certainly long.