How do stem cells ‘know’ what type of cell to differentiate into?
How do stem cells ‘know’ what type of cell to differentiate into?
Last Updated on Monday, 19 July 2010 02:31 Written by Administrator Monday, 19 July 2010 02:31
Question by michael552000: How do stem cells ‘know’ what type of cell to differentiate into?
For example, if you extracted some stem cells from a patient in order to replace some heart tissue, how would the stem cells ‘know’ that they need to differentiate into this type of tissue?
Best answer:
Answer by My intelligence > yours
Certain genes within the DNA are activated.
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I can’t say for certain but it is my understanding that it is biochemical messengers (chemical signals) released by immediate surrounding tissues and cells that sort of put the stem cell on the right track for development.
Getting stem cells to differentiate into the correct cell type and maintain that type over time can be a bit tricky, depending on the type of stem cell. But cells and tissues talk to each other, chemically, such that any one particular cells sort of knows what is going on with the other cells and tissues in its immediate environment.
Scientists probably try and mimic cellular and tissue conditions in order to get stem cells in culture to differentiate into the desired cell type.
See: Stem Cells
http://biobasics.gc.ca/english/View.asp?x=788
Stem cell differentiation ( or cell fate) is a very complex and finicky process, and if you want a long and detailed answer, I can provide specific information about specific cells, etc. However, I suspect that isn’t the case, and so I will do my best to make a very complicated process as easy as possible to understand.
There are several key elements that help stem cells know what to differentiate into.
Growth factors are various biochemical compounds that are sent as “signals” from already differentiated cells out to stem cells. Receptors on stem cell surfaces recognize these signals, and send their own signaling compounds down to the stem cell’s nucleus and so specific DNA sequences are transcribed, and translated into cell specific protein. This can also work in reverse. Often, the concentration of a growth factor can determine what type of a cell a stem cell will become. Growth factors that are released from one part of the body can have a huge impact on the whole body. As an example, a high concentration of one growth factor could yield heart cells, a medium concentration could yield lung tissue and a low concentration could yield skin tissue. In fact, the early spinal cord is one such important player of mediating cell fate by the release of certain growth factors in a concentration dependent manner. Of course, it isn’t that simple in the human body, as there are a lot of growth factors and other issues that come into play. Also, you have to keep in mind that stem cells are often in competition with each other for these growth factors, and other cellular components may inhibit stem cells, causing them to die. Stem cells can also “sense” how many and what type of cells are nearby through cell-cell contact. This involves cell membrane structures called gap junctions.
These are all issues that come into play when trying to make organs from stem cells. In fact, it is common that stem cells differentiate into a mixed cell population in a petri dish (in vitro or ex vivo work), and pure cell cultures are not by happenstance.