BABBAGE
Skin transplants
No more hard graft?
REPAIRING the skin of those who have been burned is a process of autotransplantation. First, the surgeon removes the scorched tissue from the affected area. Then he takes a patch of healthy skin from elsewhere on the patient’s body, stretches it to fit the affected area and, that done, fixes it to the wound with sutures, staples or glue. In the hands of a skilled operator such grafts are nearly always successful, but the process could surely be improved on.
The source of the spray-on skin is the same as that of a traditional graft—a piece of undamaged skin tissue from the patient in question. But once this tissue has been removed, the treatment is completely different. First, the excised skin is bathed in an enzyme solution that separates its cells from one another. Then, using a syringe or a pneumatic spray, the surgeon squirts the cells on to the wound. The whole process, including the separation of the cells, can be completed in 70-90 minutes (a traditional skin graft takes between ten minutes and an hour, depending on the size of the affected area), and the burns thereafter heal at the same rate as those which have received traditional grafts, recovering fully after 12-13 days.
One advantage of the new method is the amount of coverage that can be achieved with a given amount of healthy skin. In a normal graft, the skin is stretched to three or four times its original size before being attached to the wound. That reduces the amount that needs to be taken, but stretching any further risks mesh-like scars appearing in the healed area.
The new method, however, can cover an area at least 20 times the size of the healthy skin it uses. The sprayed cells form islands across the burn and multiply rapidly to create a continuous surface. Indeed, Dr Wood says she has been able to use a piece of skin the size of a postage stamp to cover a burn across the whole of child’s chest.
There are other benefits, too. The researchers suggest spray-on skin results in less scarring than normal grafting, even when a graft has not been overstretched. And the need to remove only a small piece of skin means it is easier to match the colour of the grafted tissue to the place where it is going. In fact, Dr Wood says she sometimes sands down existing, discoloured burn scars and sprays them with skin cells to achieve a better tone.
In a study published earlier this year, Dr Gerlach describes treating eight burn patients with a skin spray. All had second-degree burns (those that destroy the epidermis, but only part of the underlying dermis) that had not been given grafts because the doctors treating them had thought the burns in question would heal in a satisfactory way without them. In these cases, though, that judgment proved incorrect and the burns had failed to heal. This kind of delayed recovery is often associated with unsightly scarring. At least two weeks after the patients were burned—on their legs, hands, faces and, in two cases, their penises—the misdiagnosed patients were given a skin spray. All recovered without complications, and the aesthetic results were judged excellent.
For the moment, the skin spray is being used mainly as a treatment for second-degree burns. For third-degree burns (those in which the dermis has been destroyed as well) spraying only works in conjunction with a graft, as spraying alone cannot, at the moment, regenerate dermal tissue. That may change, though. Dr Gerlach is investigating ways of extracting and spraying the special stem cells needed to regenerate dermal tissue, too.
Not surprisingly, one of the main interested parties in all this is the armed forces. In America, the Armed Forces Institute of Regenerative Medicine is thinking of paying for one of Dr Gerlach’s trials. The disfigurement by burning of airmen during the Battle of Britain was one of the impetuses for the early development of plastic surgery.
The work of Dr Gerlach and Dr Wood, then, continues an old tradition of trying to return wounded soldiers from the battlefield with their looks—and thus their self-esteem—intact, as well as their health.
Copyright © The Economist Newspaper Limited 2011
