Friday, December 21, 2007

Stem cell line

A stem cell line is a family of constantly-dividing cells, the product of a single parent group of stem cells. They are obtained from human or animal tissues and can replicate for long periods of time in vitro ("within glass"; or, commonly, "in the lab", in an artificial environment).

Embryonic line creation

Embryonic stem cell lines are created from embryos. A living single stem cell from the embryo is placed in a petri dish (without agar) and provided with nutrients and growth factors that simulate those found in the womb. The resulting cell line will continue to divide provided it receives sufficient chemical signals instructing it to remain undifferentiated. There are currently more than sixty {400 total stem cell lines, according to NIH} embryonic stem cell lines in the world, but this figure is currently under dispute and many researchers in the field consider it a significant overestimate. The U.S. National Institutes of Health currently lists only 22 lines that are available for distribution to researchers.

Alternative sources

Adult stem cell lines isolated from mature tissues are commonly used in stem cell research, as are cells isolated from umbilical cord blood. However, these cells have a genetic imprint of the host they were taken from, thus limiting their therapeutic use in genetic disorders. Also, adult stem cells are not totipotent or pluripotent like embryonic stem cells, but rather more specialized cells that are multipotent.

New techniques

Typically, stem cells have been maintained using tissue culture methods that essentially date from the 1950's. In particular, they are often "fed" using mouse embryonic fibroblasts ("feeder cells") while being simultaneously suspended in a nutrient solution ("media"). However, many scientists are recognizing the importance of using media that is completely free of animal ingredients. This not only liberates cell lines from animal feeder cells, but also brings the in vivo therapeutic use of stem cells one step closer to reality.

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