24 December 2007

Adult Stem Cells vs. Embryonic Stem Cells? No Contest!

On the one hand, with adult stem cells, you have the potential to create stem cells from your own tissue. A lot of progress is being made--including the recent Harvard Medical School study that went all the way from skin biopsy to embryonic stem cell.
"Ours is the only group to go from skin biopsy to cell line," Daley said in a statement.

They said they are now working to generate the so-called induced pluripotent stem cell or iPS cells to match a variety of diseases.

Daley cautioned the approach is not ready to test in people. The researchers use viruses called retroviruses to carry in four genes that transform the skin calls back into their primitive and malleable state.

And when injected into mice, the human iPS cells often formed tumors. Daley's team is afraid this method might cause cancer or other unforeseen problems in human beings.

So pluripotent adult stem cells (ASCs) are getting better--but are not ready for the clinic yet. What about embryonic stem cells? There is some progress on that front as well.
In a groundbreaking experiment scientists from International Stem Cell (ISC) Corp. derived four unique embryonic stem cell lines that open the door for the creation of therapeutic cells that will not provoke an immune reaction in large segments of the population. The stem cell lines are “HLA-homozygous,” meaning that they have a simple genetic profile in the critical areas of the DNA that code for immune rejection. The lines could serve to create a stem cell bank as a renewable source of transplantable cells for use in cell therapy to replace damaged tissues or to treat genetic and degenerative diseases.
Science Daily

Interesting. The International Stem Cell Corp. ESCs are made for specific tissue matching to the recipient--similar to how blood transfusions are matched. This would allow for large scale "stem cell banks" in every large medical center. Specific stem cell types could be matched to the recipient within hours for a minimal cost. These ISC Corp. line of ESCs are derived from parthenogenic embryos--unfertilised eggs.

If a person planned ahead, and created large numbers of their own pluripotent stem cells in advance, and carried them with them wherever they traveled in case of emergencies, one's own stem cells would obviously be preferable. But in an urgent or emergency situation, having standard lines of tissue-matchable standard cell line ESC's would be invaluable.

There is really no contest between the two approaches. Both are important.
"Understanding how to derive stem cells from embryos may teach us how to make the reprogramming process that much more efficient," Daley said.

It was by studying embryonic stem cells that researchers learned which genes are needed to make ordinary cells act in the same way. Daley's lab used four genes and discovered that two were essential for turning back the clock and making the skin cells act like embryo cells, and two others helped them grow efficiently.

His team also converted fetal and embryonic cells into various cell types, and found these were far easier to work with.

"The fact that embryonic and fetal cells convert more efficiently than adult cells was suggested in mouse studies but the pattern is quite apparent with human cells," Daley said. "This suggests that there are many aspects of the biology of reprogramming we still need to understand to make the process more efficient."


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