Skin Burn Treatments : The Future of Wound Care

by Food and Drug Administration (FDA)

(Page 3 of 4)

TransCyte is made by Advanced Tissue Sciences Inc. of La Jolla, Calif., and was approved by the FDA in 1997. "TransCyte was the first product that FDA approved that delivered nonviable (dead) cellular material," says Rhodes. The product starts with living cells, but these cells die when frozen. TransCyte consists of human cells grown on nylon mesh, combined with a synthetic epidermal layer.

TransCyte is packaged and shipped in a frozen state to burn treatment facilities. The surgeon then thaws the product and stretches it over a burn site. In about one to two weeks, the TransCyte starts peeling off, not unlike a sunburn, and the surgeon trims it away as it peels.

TransCyte can be used as a temporary covering over full thickness and some partial-thickness burns until autografting is possible. It's also a temporary covering for some burn wounds that heal without autografting, as in Darren's case.

In addition to burn patients, people with chronic wounds can benefit from cellular wound dressings. Apligraf and Dermagraft are two products used for the treatment of diabetic foot ulcers. People with diabetes are particularly at risk for foot ulcers because of poor blood circulation in the legs and feet. If these ulcers do not heal, amputation of the foot may be required.

Apligraf, made by Organogenesis Inc., of Canton, Mass., was approved by the FDA in 1998 for leg ulcers caused by blood flow problems and in 2000 for treating the hard-to-heal diabetic foot ulcers. Apligraf is a two-layer wound dressing that contains live human skin cells combined with cow collagen.

"Apligraf is unique in that it's the first product approval that delivered live cells from a different donor," says Rhodes. As with OrCel and TransCyte, the donor cells come from circumcised infant foreskin. One small patch of cells, about the size of a postage stamp, from a single donor can be grown in the laboratory to produce tens of thousands of pieces of Apligraf.

Dermagraft, approved by the FDA in 2001, is a product of Advanced Tissue Sciences. Dermagraft is made from human cells placed on a dissolvable mesh material. Once placed on the wound or ulcer, the mesh material is gradually absorbed and the human cells grow and replace the damaged skin.

The Regulatory Challenge

Although the FDA has been regulating biological products for 100 years, the agency continues to adapt its experiences and regulatory approaches to the review of new technologies, such as cellular wound dressings. Some of these dressings use living cells and have a shelf life of only three days, says Rhodes. Some use a single donor to produce thousands of units of a product. These are just a few of the characteristics that require the agency to revise or adapt its existing regulatory approaches to these products, he says.

To help ensure the safety and quality of products such as cellular wound dressings, the FDA initiated a new regulatory system and issued a final rule, published in 2001, that requires all human cell, tissue, and cellular- and tissue-based product manufacturers to register and list their products with the FDA.

The FDA also issued other proposed rules under the regulatory system to ensure donor suitability and "good tissue practice." "The cells must be screened for a host of infectious agents and diseases," says Rhodes. And they must be handled properly to avoid viral contamination of tissue and cross-contamination that could occur if a donor cell is mixed up with another donor cell by accident in the laboratory.

"We're always walking this very delicate line between trying to be as safe as possible while also allowing progress to be made," says Noguchi. "It is very much of a dynamic balance. At FDA, we want to make sure that what we approve can be used in a way that is predictable for physicians to prescribe or to use in treatment, to the best of our ability, to the best of medicine's ability, and to the best of science's ability."

Despite the challenges of the evolving regulatory climate, the FDA is excited about these products, says Durfor. "We're attempting to set a very reasonable approach for getting cellular material grown up in tissue culture out in the commercial market, while ensuring the safety and effectiveness of every product."

The Future of Wound Care

The technology of burn and wound care using cellular wound dressings and grafts continues to make tremendous strides forward. But most surgeons agree that nothing seems to work as well as a person's own skin.

Boyce of Shriners Burns Hospital and other researchers are experimenting with cultured skin grown from a burned person's own skin cells. With this method, cells are taken from a small patch of skin, grown in the laboratory, and combined with a collagen matrix. After this cultured skin is placed on the burned area, the matrix dissolves, and the transplanted cells reform skin tissue to heal the wound.

Boyce has found this method to be especially valuable for people who have burns over more than 50 percent of their bodies, which limits the amount of healthy skin available for grafting.

Boyce envisions other future efforts to be focused on improving cosmetic outcome after burn injury. "Smoothness and pliability may have been restored completely," says Boyce, "but better color matching to uninjured skin is needed." Also needed is new technology to make wound treatment faster, and to restore hair and glands of the skin that do not regenerate from grafts.

"Researchers continue to make advances, but the field is in its infancy," says Rhodes.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.