Turning back time: embryonic stem cell rejuvenates skin cell.

By fusing an embryonic stem cell with an adult skin cell, researchers have created cells that retain valuable embryonic characteristics but carry the adult cell's genes. This new method might eventually lead to stem cell lines that match a patient's DNA while avoiding the destruction of human embryos, a process that some people find morally unacceptable.

Scientists envision someday using embryolike cells to grow tissues for transplant or transplanting such cells into a patient, where they would grow to replace damaged or diseased tissues. If these cells carried a patient's genetic material, they might sidestep the risk of a destructive immune reaction.

Some scientists also predict that cells with embryonic properties could give researchers a new way to study genetic diseases. Cells that carry the DNA from a patient with a genetic disease could differentiate in a petri dish, permitting scientists to observe how disease characteristics develop.

Korean scientists recently created the first lines of embryonic stem cells derived from clones made with people's cells. However, the team used more than 100 human eggs, which are difficult to obtain, and created early human embryos, which they destroyed to harvest stem cells (SN: 5/21/05, p. 323).

Previous experiments had shown that when scientists fuse two types of cells, such as muscle and liver, the product often ends up resembling one cell type more than the other. Seeking a new way to create cells that have the qualities of embryonic stem cells, Kevin Eggan of Harvard University and his colleagues decided to fuse an embryonic stem cell with an adult cell.

Using a chemical that partially breaks down cell membranes, the researchers merged the cell interiors, including the DNA-bearing nuclei, of pairs of skin cells and embryonic stem cells. Eggan's team then let the combination cells multiply in petri dishes.

Genetic tests of the resulting colonies showed that the new cells contained two sets of chromosomes: one set from each of the contributing cell types. On their surfaces, the cells displayed protein markers that appear on embryonic stem cells as well as markers present on the adult cells.

The scientists found, however, that the cells grew into tight, round colonies characteristic of embryonic stem cells. Further examination showed that the new cells could multiply indefinitely, as embryonic cells do. In contrast, adult skin cells die after dividing a few times.

Much as embryonic stem cells do, the new cells differentiated into the three basic embryonic tissue types in the laboratory plates and when transplanted into mice.

Eggan says that the research, reported in the Aug. 26 Science, may give scientists clues to what factors "reprogrammed" the adult skin cells to an embryonic state. "If one could just understand how that reprogramming process works, then one might be able to directly turn adult cells into embryonic cells without using embryos," he says.

However, researchers will need to find a way to halve the double set of DNA in the new cells before they can be used to treat patients, says Robert Lanza of Advanced Cell Technology, a Worcester, Mass.-based company that studies cloning and stem cells. "Untangling the [new cells'] chromosomes could be more difficult than ... understanding how you reprogram an adult cell," he says.