About Stem Cell Lines

The disconcerting fact at the moment is that there just aren't that many viable cell lines for study and use – not if you're a researcher who depends, at least in part, upon federal funding, a description that pretty much includes all interested scientists and laboratories.

When President Bush restricted stem cell research in 2001, spurred by opposition to using human embryos as source material, he declared that the number of pre-existing cell lines was adequate to meet the nation's research needs.

That number was 78, and it proved to be an illusion. Almost half of the cell lines identified by the Bush administration were not actually available to U.S. scientists...

The passage of Proposition 71 in November, which allocates $3 billion for stem cell research over the next 10 years, is bound to raise that number.

When it comes to making a stem cell line, the hard part isn't only about the science. Researchers derive starter stem cells from human embryos originally created by fertility clinics. These embryos must be donated to science. They cannot be bought or sold[...]

How the Stem Cell line gets created

At the bottom of the tissue culture dish, which has been negatively charged to encourage cell adhesion, lies a first layer of fibroblast cells, usually mouse-derived.

Fibroblasts, or "feeders," are connective tissue cells that create an underlying matrix upon which stem cells can grow. But maybe more importantly feeder cells secrete factors that help keep stem cells in their undifferentiated state.

Keeping stem cell lines undifferentiated is absolutely essential if they are eventually to be used for medical purposes. There are 3 types of stem cells that develop life through a gradual restriction:

1. Totipotent stem cells can create whole organisms, plus all extra-embryonic tissues such as the placenta. They are master cells and, in humans, exist only during the first few divisions after an egg is fertilized;

2. Pluripotent stem cells are slightly more specialized. They can make all of the cells of the organism, and some but not necessarily all the placental cell types;

3. Multipotent stem cells are even more specialized. They can develop into only a limited number of cell types. Hematopoietic cells, for example, are blood stem cells that can morph into several types of blood cells but cannot develop into, say, neurons.[...]

Last month, researchers at UCSD and the Salk Institute reported that all human embryonic stem cell lines currently approved for use in federally funded studies were contaminated with a foreign molecule derived from mice. The finding, they said, renders the lines unusable for human medical therapies.[...]

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