(Agencies)
Updated: 2007-12-24 07:07

A scientific team from the University of Wisconsin-Madison created genetic modifications in skin cells, pictured here in this undated handout, to induce the cells into what scientists call a pluripotent state - a condition that is essentially the same as that of embryonic stem cells. [Agencies]

WASHINGTON - A third team of researchers has found a way to convert an ordinary skin cell into valued embryonic-like stem cells, with the potential to grow batches of cells that can be directed to form any kind of tissue.

Their study, published on Sunday in the journal Nature, shows the approach is not a rare fluke but in fact something that might make its way into everyday use.

Scientists hope they are starting an age of regenerative medicine, in which people can get tailor-made treatments for injuries, diseases such as Parkinson's and diabetes, and in which scientists can study disease far better than before.

Dr. George Daley of Harvard Medical School and Children's Hospital Boston and colleagues got their skin cells from a volunteer, whereas the other two teams of researchers who have accomplished the feat got theirs from commercially available cells grown in labs -- a seemingly small difference, but one Daley says shows it is feasible to get cells from any volunteer.

"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.

They also reprogrammed mesenchymal stem cells, a distinct adult stem cell type isolated from bone marrow that is the precursor of fat, bone and cartilage.

Embryonic Cell Work Continues

Daley said his team would also continue to work with true embryonic stem cells, taken from days-old embryos. While their use is controversial because it involves the destruction of the embryo, most stem cell experts say it is essential to continue to study them.

"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."