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MIT researcher tests new skin

Night Ed: Please put a kicker on this. The kicker should be: Technology -- it should be like the FEATURES kicker.

By Lauren Seeley

Researchers at MIT and Massachusetts General Hospital (MGH) are clinically testing an artificial skin that should provide a permanent replacement for irreparably damaged skin, according to Dr. Ioannis V. Yannas '59 of the Department of Mechanical Engineering.

Yannas, Dr. Dennis Orgill '83 and Mr. Eugene Skrabut '69, all of MIT's Department of Mechanical Engineering, have collaborated with Dr. John F. Burke of MGH to develop Stage 2 artificial skin.

Stage 2 artificial skin is an improvement over Stage 1, which Yannas and his research team have worked on for over a decade. He has already successfully tested Stage 1 skin on human burn victims.

Whereas Stage 1 skin only promotes regrowth of the dermis -- the innermost layer of skin -- Stage 2 also promotes the growth of new epidermis, said Yannas. The epidermis is the functionally crucial outer layer of skin.

The first step in making artificial skin is identical for Stages 1 and 2. Yannas makes a template of collagen fibers taken from cowhide.

The template provides a lattice around which the body's own cells can begin to grow. The collagen lattice slowly degrades, ideally at roughly the same rate as new tissue forms in the wound, Yannas said.

If a burn wound is smaller than a half-dollar, the skin can regenerate itself without too much damage by growing inward from the edge of the wound. But with a burn wound any larger, "the dermis is not spontaneously regenerable, and instead you get scar tissue," Yannas said.

The purpose of the collagen template is to "channel the process of wound healing away from scar synthesis to the synthesis of dermis," he said.

To prevent water loss and infection, Yannas places a silicone layer over the collagen template, which acts as a temporary epidermis.

After the dermis has regrown, which usually takes about 20days, Yannas replaces the silicone layer with patches of epidermis taken from unburned parts of the victim's body. These skin patches grow together, creating a new epidermis.

The problem with Stage 1 skin was that when large portions of the patient's body are severely burned, it was difficult to find enough unburned skin to patch up the epidermis.

Stage 2 skin eliminates this problem by providing an epidermis as well as a dermis. Yannas takes basal cells, "the innermost, baby cells," from a quarter-sized patch of unburned skin. He then seeds them into the collagen template in a centrifuge.

Basal cells in normal skin grow in a layer on top of the dermis and work their way up through the epidermis to replace old cells. In the seeded artificial skin they proliferate to form new epidermis complete with nerves and blood vessels.

The actual laboratory procedure for seeding the skin takes about 100 minutes from start to finish.

MGH surgeons take a quarter-sized layer of thin, unburned skin tissue from the patient and hand it over to the waiting Yannas. He puts the skin sample in a jar with the enzyme trypsin, which cuts the bonds between the dermis and epidermis.

Back at the MIT lab, Yannas and his research team throw away the epidermis and spin the remaining dermis in a vortex. The vortex separates the basal cells from the dermis.

Yannas then takes the basal cells and seeds them into the collagen template to create artificial skin custom-made for the particular burn victim.

The new skin is capable of "temperature regulation and almost every neurological sensation," Yannas said.

However, the new epidermis does not promote regrowth of hair follicles or sweat glands, he noted. The body uses sweat glands to regulate temperature.

Yannas said, however, the body has "another method of moisture loss, which is diffusion of water through the epidermis."

In addition to its ability to save lives and prevent disfigurement of burn victims, the Stage 2 artificial skin interests Yannas because the regrowth of skin is similar to embryonic development.

"Nerves regenerate because the growing axons find the same kind of tissue that nerves find when they grow in an embryo," Yannas said. He called this process "a biological phenomenon that shouldn't be happening but that is happening."

Yannas has not yet studied the metabolism of the Stage 2 skin, which would show whether the skin can perform functions such as producing Vitamin D. He is now studying the immunology of the artificial skin.

Stage 2 artificial skin has proven successful in tests with guinea pigs. Yannas expects the ongoing clinical tests to end in May, at which time he will report his findings in a scientific journal.