Artificial skin that slowly releases a stem-cell-attracting protein could improve the healing process for patients with severe burns and for diabetics with foot ulcers. Preliminary studies combining a commonly used skin substitute with a growth factor have demonstrated faster healing in mice. The animals even appear to have regenerated new tissue, rather than scar tissue.

For patients with extensive, severe burns, skin grafts alone are not enough to help them heal: they may not have enough healthy skin to allow doctors to graft all the wounds immediately, or their burns may extend deep below the top layer of skin. Skin substitutes help close the wounds and coax the lower layer of the skin to regenerate. These skin substitutes, which doctors overlay with skin grafts after a few weeks, have helped many patients. But it takes about two weeks for the body to fill them with blood vessels that bring infection-fighting immune cells to the wounds, leaving patients vulnerable. And the scar tissue that heals over their wounds lacks sweat glands and hair follicles.

François Berthiaume, assistant professor of engineering and surgery at Harvard Medical School, is trying to use stem cells to help improve artificial skin's resistance to infection and reduce its tendency to scar. Although there has not been much research into using stem cells to heal wounds such as burns, Berthiaume says that they could help regenerate tissue more quickly and with less scarring than normally occurs when skin substitutes are used to treat wounds.

But patients with extensive burns are fragile, and harvesting their stem cells for a skin graft could be traumatic. So Berthiaume and his colleagues at the Shriner's Hospital decided to try to draw the stem cells circulating in a patient's blood to the wound with a growth factor known to attract stem cells.

Tests in mice involving the growth factor have demonstrated better wound healing, says Berthiaume. "At three weeks, the wounds closed completely and seemed to form new, rather than scar, tissue," he says. Wounds treated with the skin substitute without the growth factor were still red and leaky after the same amount of time. Berthiaume still doesn't know for certain whether stem cells were attracted to the wounds or whether the growth factor improved healing by some other means.

Each year, about 45,000 people are hospitalized with burn injuries, and half of them require treatment in a special burn unit. For patients suffering severe burns and for diabetics with foot ulcers, better artificial skin would mean faster healing and an improved quality of life.