Grape-seed extract may help skin wounds heal faster and with less scarring, a new study suggests.
Researchers at the Ohio State University's Heart and Lung Research Institute report that the extract seemed to aid wound healing in two ways: it helped the body make more of a compound used to regenerate damaged blood vessels, and it also increased the amount of free radicals in the wound site. Free radicals help clear potentially pathogenic bacteria from a wound.
In two related experiments, the researchers tested the effects of grape-seed extract on mice and on human skin cells. Chandan Sen, a study co-author and director at the Laboratory of Molecular Medicine at the Institute said this is the first evidence suggesting that a natural extract can have a profound effect on wound healing.
"We saw the healing effects grape-seed extract had on wounds from day one," he said. "It seemed to enhance the formation of epidermal tissue as well as the deposition of connective tissue."
The researchers treated skin wounds on mice with a topical formulation of grape seed proanthocyanidin extract (GSPE). Proanthocyanidin, one of the main ingredients in grape-seed extract, is thought to be a potent antioxidant. But in a wound site, which is rich in free radicals, the extract assumes some pro-oxidant properties, according to the researchers.
The nine mice in the study were given two small puncture wounds - GSPE was applied to one of the wounds, and the other was covered with saline solution as a control. Otherwise, the wounds were left to heal naturally.
The animals were euthanised five days after they were wounded. A small area of skin - 1 to 1.5 millimetres - was excised from the edges of the treated and untreated wounds. The researchers looked for signs of enhanced healing in the GSPE-treated samples, and compared these samples to the healing patterns of the saline-treated tissue.
"The skin treated with grape-seed extract was further along in the healing process compared to the saline-treated tissue," Sen said. "The extract-treated skin showed signs of healing faster and the newly formed tissue was denser, meaning that its structure was stronger."
The researchers saw increased levels of tenascin, a protein that helps build connective tissue, in the granulation tissue of the wounds treated with GSPE. Granulation tissue is the rough, pinkish tissue that normally forms as a wound heals. It contains new capillaries and connective tissue.
"Tenascin is a marker for skin wound healing," Sen said. "There was much more tenascin present in the granulation tissue of the wounds treated with GSPE."
The researchers also noted increased levels of VEGF, the compound that helps the body rebuild blood vessels. In previous research, Sen and his colleagues found that GSPE helped turn on the gene responsible for initiating the making of VEGF.
In a related experiment, the researchers also treated human skin cells with GSPE, and found that the extract helped the laboratory-grown cells produce more VEGF. "More VEGF means blood vessels will form faster and that more nutrients will be carried by the blood to regenerate damaged tissue," Sen said.
In addition to helping blood vessels regenerate, GSPE also seemed to increase free radical levels at the wound site. Sen explained the unusual effect of the antioxidant - which helped free radicals flourish: "The extract assumed a mild pro-oxidant property while in an oxidant-rich environment," Sen said. "Excessive amounts of free radicals are damaging. But every living cell makes free radicals. In controlled amounts, they help the body function."
At low concentrations, free radicals can stimulate the proliferation of cells as well as the formation of connective tissue and new blood vessels, he added. "Skin wounds are rich in free radicals. There was a longer-lasting free radical effect in the wounds that had been treated with grape-seed extract. We think that's partly why these wounds healed faster and better."
However Sen cautioned that topical grape seed extract is not sold commercially and consumers would not get the same wound-healing benefits from taking grape-seed extract in vitamin form.
"Taken orally, the extract functions like an antioxidant. But in a wound, where free radicals are abundant, that proanthocyanidin assumes pro-oxidant behaviour."
The study appears in a recent issue of the journal Free Radical Biology and Medicine. The National Institutes of Health funded the work and InterHealth Nutraceuticals supplied the grape-seed proanthocyanidin extract.