What is Stem Cell?•Stem cells have the remarkable potential to develop into many different cell types in the body. •Serving as a sort of repair system for the body, they can theoretically divide without limit to replenish other cells as long as the person or animal is still alive (self-renewable)•When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell (differentiation).
Unique properties of all stem cells•All stem cells—regardless of their source—have three general properties: –they are capable of dividing and renewing themselves for long periods; –they are unspecialized; –and they can give rise to specialized cell types.
Stem cells are capable of dividing and renewing themselves for long periods.•starting population of stem cells that proliferates for many months in the laboratory can yield millions of cells. If the resulting cells continue to be unspecialized, like the parent stem cells, the cells are said to be capable of long-term self-renewal.
Questions related to their long-term self-renewal:1.why can embryonic stem cellsproliferate for a year or more in the laboratory without differentiating, but most adult stem cellscannot; and 2.what are the factors in living organisms that normally regulate stem cell proliferationand self-renewal?
•Discovering the answers to these questions may make it possible to understand how cell proliferation is regulated during normal embryonic development or during the abnormal cell divisionthat leads to cancer. Importantly, such information would enable scientists to grow embryonic and adult stem cells more efficiently in the laboratory.
Stem cells are unspecialized•A stem cell does not have any tissue-specific structures that allow it to perform specialized functions. –A stem cell cannot work with its neighbors to pump blood through the body (like a heart muscle cell); –it cannot carry molecules of oxygen through the bloodstream (like a red blood cell); –and it cannot fire electrochemical signals to other cells (like a nerve cell). •However, unspecialized stem cells can give rise to specialized cells, including heart muscle cells, blood cells, or nerve cells.
Stem cells can give rise to specialized cells•The signals inside and outside cells that trigger stem cell differentiation are just beginning to be understood. •The internal signals are controlled by a cell's genes, •the external signals for cell differentiation include chemicals secreted by other cells, physical contact with neighboring cells, and certain molecules in the microenvironment.