No need to worry about the ethical implications of stem-cell research anymore: American scientists have done it again! Continuing the work of their fellow Japanese and US colleagues, another team of US scientists has come up with a way to produce “safe patient-specific” cells that don’t pose the risk of developing cancer.

Back in November, probably the biggest medical discovery of 2007 was reported in journals Science and Cell by two teams of Japanese and US biologists. It referred to the creation of stem cells from human tissue, without passing through the un-ethical procedure of destroying human embryos. Dr. Shinya Yamanaka, from the University of Kyoto- who led the research in this domain- successfully reprogrammed human adult cells to function like pluripotent embryonic stem (ES) cells.

Stem cells are the most promising cure for most of the degenerative diseases affecting elderly people (Alzheimer, Parkinson) or for the “re-construction” of body-parts affected by accidents (burns, spinal cord-injuries, head-traumas, etc.). Stem cells are undifferentiated somatic cells with the capability of indefinitely replicating (they divide giving birth to exact replicas of themselves), but are valuable to science from another point of view: they can be “programmed” to give rise to highly specialized cells of each tissue type (using the appropriate “input” signal).

Stem cells also eliminate one of the boundaries that make organ-transplants dangerous: compatibility. In case of an organ-transplant from someone else, the patient is at risk of developing an immune reaction to the new organ, since its body doesn’t recognize the latter’s genetic code. Once organs “crafted” from the patient’s own cells will become a reality, the compatibility problem will cease to exist.

Dr. George Daley’s team from the Children's Hospital, in Boston, Massachusetts, recently reported in the journal Nature that Yamanaka’s breakthrough work has been pushed even further. Induced pluripotent stem cells (or iPS, the kind of cells obtained previously by Yamanaka) have been obtained from foetal lung and skin cells, from neo-natal skin cells as well as from skin samples taken from a healthy human volunteer. The procedure is similar: “turning back the clock” of the experimental cells by implanting four genes into them. The result, effectively achieved with the help of a retrovirus, shows that experimental cells lose their highly-specialized profile and become iPS.

But what is really outstanding is that Daley’s team obtained iPS without a cancer gene called c-Myc, which induced many cancers in lab mice during testing.

However, the scientists warn us that there’s a long way to go until we can successfully apply stem cell therapy to real life patients. "Clinical success with human iPS cells must await the development of methods that avoid potentially harmful genetic modification," the Nature article said.