A research team from Tohoku University has discovered a new type of pluripotent stem cell in the skin and bone marrow of adults, providing a possible third source of stem cells after embryonic stem cells and human-made induced pluripotent stem cells.

The cells -- dubbed Muse cells -- apparently have a lower proliferation rate than the other two types, but according to the research team led by professor Mari Dezawa, there is little risk they will become cancerous, and expectations of practical treatment applications are high.

The research team focused on the Muse cells -- which are extremely rare -- when they realized how similar they were to embryonic stem cells. After extraction and cultivation, the Muse cells transformed into a number of tissues, including nerve, muscle and liver.

When applied to the damaged skin, muscle and livers of mice, the Muse cells transformed into the appropriate tissue, and unlike embryonic or induced stem cells -- which can multiply infinitely -- they stopped multiplying after about two weeks. Furthermore, Muse cells implanted in mouse testicles did not become cancerous after six months of observation, while embryonic cells turned into tumors after eight weeks.

The results will be published during the week of April 19 in the U.S. journal Proceedings of the National Academy of Sciences.