When someone has a severe burn, a protective covering needs to be temporarily grafted onto the wound site – and as soon as possible. Although that covering typically consists of skin from a human cadaver, genetically-engineered live-cell pig skin has now been used on a patient for the first time.
Applied to second- and third-degree burns, sheets of human cadaveric skin – also known as allografts – initially help to protect wounds against infection and fluid loss, along with the potentially-lethal complications that could follow. Once the recipient has stabilized, the allograft is removed and a piece of the patient's own skin is permanently transplanted onto the wound, from another part of their body.
Unfortunately, though, allografts are often in short supply, plus they can be expensive. With that in mind, scientists at Massachusetts General Hospital (MGH) developed a genetically-modified line of pigs, back in the 1990s. Those animals lack a gene that is ordinarily present in pigs but not in humans, allowing skin grafts from the pigs to appear less "foreign" to a human patient's immune system.
The technology has since been commercialized by spinoff company XenoTherapeutics, in the form of live-cell tissue grafts known as Xeno-Skin. In a recent clinical trial, MGH surgeon Jeremy Goverman used one of those "xenografts" on a human recipient for the first time.
Measuring 5 by 5 cm (2 by 2 inches), the Xeno-Skin was applied to a burn alongside a larger conventional allograft. Both were secured in place using surgical staples and gauze bandages, and then removed five days later. At that point, the two coverings were found to be "indistinguishable from each other" in appearance, having performed equally well at protecting the underlying wound by temporarily adhering to it as the patient stabilized.
A skin graft from the recipient's own thigh was then permanently applied to the wound, with healing now progressing as anticipated. Importantly, the scientists detected no transmission of porcine endogenous retroviruses, the risk of which has previously limited the viability of transplanting live tissue or organs from pigs to humans.
"This small step we took today, represents a massive number of hours spanning decades of research in a multitude of fields including transplantation biology, immunology and genetic engineering," says Goverman. "Additionally, rapid advancements in gene-editing technology open a vast new avenue for genetically modifying pig skin that isn’t rejected, representing the next chapter in standards of care for burn and transplant patients alike."
