Developing Lab-grown Skin: The Dermis
In the 1970s, after deciding to perform routine skin excisions, doctors needed a skin covering that could serve as a layer of skin and protect a burned body, and they needed more sources for skin grafts. The problem with developing these things is that skin, despite being thin, is fairly complicated. It contains seven different kinds of cells arranged in a complicated structure that doctors still can't duplicate. At the time, researchers could replicate most of the various kinds of skin cells, but they couldn't get them to work together the way that healthy skin does.
The researchers were particularly struggling with cells known as keratinocytes, which make their way to the surface of the skin before sloughing off. Before the sloughing, keratinocytes emit chemical signals that activate skin growth, making them a key ingredient in skin regeneration. But without the proper skin structure, keratinocytes act bizarrely, so even though scientists didn't understand the exact configuration of skin, they had to create a foundation close enough to it that the keratinocytes could flourish. They also needed the structure to form without the skin cells related to the immune system or blood vessels, as these cells are why a burn victim rejects a skin transplant.
Researchers James F. Burke and Ioannas Yannas came up with the artificial means that could serve as a skin covering while encouraging keratinocytes. They knew that the base of the skin is made up of collagen-producing cells known as fibroblasts, so they created a layer of "skin" by using collagen from cows and sharks in combination with glycosaminoglycan, a sugar molecule.
The components in Burke and Yannas's creation were arranged so that they served as scaffolding for new, growing skin cells; fibroblasts migrated from nearby healthy cells and from transplanted skin grafts to form new layers of skin. Once the new dermis formed, the fibroblasts caused the temporary model to dissolve, and the new cells took over. Since the human dermis can't regenerate on its own, this was a particularly notable achievement; unfortunately, further development and approval by the U.S. Food and Drug Administration were delayed for years, which is why the technology is still not widespread [source: Smith]. The product is now known as Integra.
The artificial skin membrane, which resembled plastic wrap, both protected the patient and kick-started growth of the patient's skin cells. But burn victims were only halfway down the road to new skin; they still needed an epidermis.