Nature knew what she was doing when she designed skin, the body's largest organ. As a covering for the body, nothing else comes close as a first level of defense against infection, trauma, and dehydration. The problem is that skin is always in short supply for the 4 million people plagued by chronic wounds and the more than 50,000 people hospitalized for burn treatment in the United States each year.

Traditional treatments for these painful and often life-threatening conditions include dressings that protect smaller wounds and passively allow the body to heal. Treatment for large or stubborn wounds may entail skin grafting. But a skin-graft operation requires hospitalization and creates another wound at the donor site. And after a great deal of pain, trouble, and expense the graft simply doesn't always survive.

Dissatisfied with these conventional treatments, researchers in the 1980s eagerly tried to isolate naturally occurring growth factors that promote healing. But the results with single growth factors have been generally disappointing because wound healing has turned out to be more complex than researchers originally thought, and figuring out which factors to daub on a wound, when, and at what dose remains a daunting task.

Scientists have therefore turned to cultured skin, hoping that it would not only provide a much needed covering but also be ready to use off the shelf without the need for donor matching. In fact, one novel type of cultured skin, called Apligraf Living Skin Equivalent, has shown great promise in that regard. According to its manufacturer, Organogenesis of Canton, Mass., when the living-skin tissue was used in clinical studies on patients with venous ulcers, which normally occur on the legs and feet as a result of abnormal blood drainage, wounds healed on average in 57 days. Comparable wounds treated with standard therapy using pressure dressings healed on average in 181 days. And 57 percent of patients who had battled their ulcers for more than a year saw their wounds close completely, compared with 17 percent of those receiving conventional treatment.