Biomedicine

Spraying on Skin Cells to Heal Burns

A new technique in burn treatment provides an alternative to skin grafts in the operating room.

Traditionally, treatment for severe second-degree burns consists of adding insult to injury: cutting a swath of skin from another site on the same patient in order to graft it over the burn. The process works, but causes more pain for the burn victim and doubles the area in need of healing. Now a relatively new technology has the potential to heal burns in a way that’s much less invasive than skin grafts. With just a small skin biopsy and a ready-made kit, surgeons can create a suspension of the skin’s basal cells–the stem cells of the epidermis–and spray the solution directly onto the burn with results comparable to those from skin grafts.

Spray-on skin: In a unique treatment for second-degree burns, surgeons harvest a small number of skin cells through a skin biopsy, suspend them in solution, and then spray the resulting mixture onto a burn wound. Once in place, skin stem cells, called basal cells, proliferate to create a new layer of skin.

The cell spray is intended to treat severe second-degree burns, in which the top two layers of skin are damaged but the subcutaneous tissue is left intact. Third-degree burns, which are more severe, still require a skin graft. The spray, already approved for use in some countries, has garnered interest from the United States Army, whose Armed Forces Institute of Regenerative Medicine is funding a trial, slated to begin before the end of this year, of more than 100 patients.

The technology, developed by Australian surgeon Fiona Wood, relies on cells, such as skin progenitor cells and the color-imparting melanocytes, that are most concentrated at the junction between the skin’s top two layers. With a small step-by-step kit dubbed ReCell, surgeons can harvest, process and apply these cells to treat a burn as large as 50 square inches. The kit, marketed by Avita Medical, a United Kingdom-based regenerative-medicine company, is a tiny, self-contained lab about the size and shape of a large sunglasses case.

After removing a small swatch of skin near the burn site (the closer the biopsy, the better for precise matching of color and texture), the surgeon places it in the kit’s tiny incubator along with an enzyme solution. The enzyme loosens the critical cells at the skin’s dermal-epidermal junction, and the surgeon harvests them by scraping them off the epidermal and dermal layers and suspending them in solution. The resulting mixture is then sprayed onto the wound, repopulating the burn site with basal cells from the biopsy site.

“Currently, treating any burn that requires a skin graft is the same technology we were routinely using 30 years ago,” says James Holmes, a surgeon and the medical director of the Burn Center at Wake Forest University Baptist Medical Center. Current practice with larger burns requires grafts from donor skin that are anywhere from one-quarter to the complete size of the burn area. ReCell requires only as much as four square centimeters. “This allows you to take a very small skin biopsy and process it at the table there in the operating room using a fully prepackaged device,” Holmes says. “You’re able to cover an area that’s 80 times the size of your biopsy.”

Holmes is the lead investigator on an upcoming multicenter trial that will compare skin grafts and ReCell. Patients in the trial will act as their own controls: If a burn victim has a second-degree burn severe enough for surgeons to deem treatable by skin graft, half of the burn will be treated that way, while the other half will be treated with the cell spray.

Lab in a box: The ReCell kit, hardly bigger than a designer sunglasses case, houses a miniature lab for harvesting skin basal cells.

Not everyone agrees that second-degree burns require grafts or other treatments to heal. “Most burns heal without a skin graft. They mostly heal with a Band-Aid,” says Robert Sheridan, a surgeon at the Shriners Burn Institute at Massachusetts General Hospital in Boston. “There’s a long history of autologous [derived from the patient] products for burn treatment, and they all suffer from high costs or neutral results.” The upcoming U.S. study won’t compare ReCell against no treatment, so this issue is unlikely to be resolved soon.

As a complete replacement for skin grafts, ReCell only works against severe second-degree burns–deeper, third-degree burns have destroyed the layer of skin that the ReCell solution would be able to repopulate. But the spray may be useful in treating more severe burns in conjunction with other approaches, as well as for treating existing scars. Wood, director of the burns unit at Royal Perth Hospital, uses ReCell in a process called scar remodeling, in which the cell spray helps repopulate scarred skin with melanocytes so that it more closely matches the patient’s original skin tone. She also uses it in combination with other treatments, such as the skin-growing scaffold Integra, to reduce scarring and improve healing time.

“I use this technology in combination with all the other traditional technologies, and I can improve the outcome and the speed of healing,” says Wood, who is also co-founder of the McCombs Foundation, a nonprofit dedicated to burn research and scarless healing. Royal Perth Hospital once had a long waiting list of patients for reconstruction surgery to fix the deep scars that accompanied third-degree burns. Now, she says, no waiting list exists. “Our reconstruction rates are going down because people don’t need it. Because we’re doing more at the beginning, they don’t need the secondary scar work.”

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