November 21, 1997

New skin graft eases diabetic foot ulcers

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Dr. Lloyd King Jr. and Dr. June Chen examine patient Dee Teasley's diabetes-related foot ulcers. Photo by Donna Jone Bailey.

New skin graft eases diabetic foot ulcers

A new type of skin graft being tested at Vanderbilt University Medical Center and the Veterans Administration Medical Center is showing promise treating diabetic foot ulcers.

Commonly associated with severe diabetes, foot ulcers can sometimes go unnoticed due to nerve damage that limits the ability of diabetes patients to feel their feet.

In order to help these open wounds heal faster, physicians are using a 'living skin equivalent' to cover and blend with the patient's own skin.

Once applied, the living skin equivalent quickly bonds with the patient's skin and supplies it with fibroblasts ‹ cells responsible for skin growth ‹ and other nutrients such as keratinocytes, and growth factors.

"One of the major causes of hospital admissions for patients with diabetes is infected foot ulcers," said Dr. Lloyd E. King Jr., professor of Medicine and Director of the Division of Dermatology.

"This new therapy puts a 'living' roof over the hole created by the ulcer. The idea of the living skin equivalent is that the ulcer will heal quickly if there is something to hold and stimulate the matrix of collagen and fibroblasts in the ulcer."

The new skin cells in the graft that are added to the wound are like a biological computer which senses what is needed and then makes it. There is also reduced fear of rejection because the skin equivalent contains no lymphocytes or macrophages from the bone marrow, which cause an immune response in most other organs.

This lack of lymphocytes and macrophages in the skin equivalent also means that it does not likely contain diseases such as HIV or hepatitis, King said.

The skin equivalent is grown in plastic trays using skin cells taken from an unusual source ‹ the foreskins of newly circumcised infants. These cells are then grown using a nutrient base until they are ready to be applied to an ulcer.

Foot ulcers form in diabetics due to the loss of blood flow to the feet. Blood vessels that supply nerve cells with the nutrients and oxygen that keep them alive are damaged due to the thickening of these vessels caused by excess glucose in the bloodstream. This eventually leads the nerve cells in the feet to degenerate.

Diabetics can also lose the arch in their feet because the nerves no longer give the correct signals to the tendons and muscles which control the tension in the arch.

The loss of the arch gives people a "rocker" foot, which puts pressure on bones that meet the ground and cuts off the circulation to the feet, causing ulcers.

The majority of diabetic foot ulcers, up to 80 percent, heal on their own given enough time, said Dr. June Chen, a surgical resident doing a research fellowship in Dermatology with King.

"This new skin equivalent is being developed for the 20 percent that don't heal and need further treatment," Chen said.