Artificial skin

Artificial skin, a synthetic equivalent to human skin, can dramatically increase the chance of survival of severely burned patients. The first synthetic skin was invented by John F. Burke, chief of Trauma Services at MassachusettsGeneral Hospital, and Ioannis V. Yannas, chemistry professor at MassachusettsInstitute of Technology. Seeing so many burn victims during his career, Burke had long been seeking a replacement for human skin that would prevent infection and dehydration. Meanwhile, Ioannis Yannas had been studying collagen, aprotein found in human skin. Teaming up during the 1970s, the two found thatcollagen fibers and a long sugar molecule (called a polymer) could be combined to form a porous material that resembled skin and, when placed on wounds of lab animals, seemed to encourage the growth of new skin cells around it. The pair then created a kind of artificial skin using polymers from shark cartilage and collagen from cowhide. Using their synthetic material, called Silastic, Burke and Yannas continued experimenting and found that artificialskin acts like a framework onto which new skin tissue and blood vessels grow, although these new cells are unable to produce hair follicles or sweat glands normally formed in the dermis. As the new skin grows, the cowhide and shark substances from the artificial skin are broken down and absorbed by the body. In 1979 Burke and Yannas used their artificial skin on their first patient, a woman who had suffered burns over half her body. After peeling away her burned skin, Burke applied a layer of artificial skin and, where possible, grafted to it some of her own unburned skin. Three weeks later, the woman's newskin, the same color as her unburned skin, was growing at an amazingly healthy rate.

Meanwhile, at nearby Harvard University, Howard Green had begun culturing human skin cells under sterile conditions and growing a sheet of human epidermiscells from a tiny piece of a person's skin. However, when the cultured skinwas placed on a wound it was rejected by the body's immune system. Green later began work with Eugene Bell of MIT who founded a research group called Organogenesis. The goal of this Boston-based firm was to make artificial skin that would include an epidermis layer and solve the problem of rejection. This research has produced a product called Graftskin--a living skin equivalent made of purified bovine collagen into which dermal cells from infant boys' foreskin have been "seeded." On top of that layer is an epidermal layer ofthe cultured human skin cells. It is formed into 4 x 8 in (10 x 20 cm) sheetsthat can be sutured or stapled onto a patient during surgery. No rejection was seen in clinical trials. Hospital trials included burn victims, patients needing skin grafts after cancer surgery, and those with chronic nonhealing wounds. In January, 1998, this multilayered, tissue-engineered skin trade marked Apligraf received unconditional recommendation from the FDA advisorypanel for treating venous leg ulcers, making it the first living manufactured organ ever recommended for approval by the FDA. (A welcome side benefit ofthis research is that it can be used to test dermatological products withouttesting on animals.)

Another company in California, Advanced Tissue Sciences, engineers a productcalled Dermagraft using a similar method, producing 250,000 square feet of final product from one foreskin. In a study of 85 burn patients, Dermagraft, used as a temporary skin until permanent skin grafts could be done, cutthe need for surgery in half and reduced hospital stays my months. Hy-Gene, Inc. in New Jersey, clones a patient's own skin cells producing an epidermis about 10 layers thick. In three weeks, a small patch of cloned skin can grow enough to cover an entire human from head to toe. This product was patented and went into clinical trials in November, 1997. A fourth company, Integra LifeSciences, does not clone skin but manufactures a matrix from collagen and shark cartilage with appropriate pore size and absorption rate for a wide rangeof human body parts. The environment of this lattice-like structure "tricks"the body into growing replacement tissue.

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