Low-level light therapy: Despite controversy, technology may be beneficial in wound healing

Key Points

Boston - Low-level light therapy (LLLT) has proven advantageous for a number of medical conditions; most recently, it has been shown again to be helpful in accelerating the healing of cutaneous wounds in mice.

For decades now, light therapy has been practiced worldwide; however, the therapy still remains controversial, probably because people have not settled on what the actual mechanism is.

"The whole field, unfortunately, does attract its share of alternative medicine practitioners and healers, which does not help LLLT's credibility. We do hope that by soundly based scientific studies with real hard biochemical mechanisms, we can convince the skeptics," says Michael R. Hamblin, Ph.D., associate professor, department of dermatology, Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School.

Dr. Hamblin recently conducted a study with LLLT, in which more than 100 mice of different strains were inflicted with a full-thickness and reproducible excisional wound. Thirty minutes following wounding, the mice received a single exposure of low-level light therapy, and the results were compared to controls.

Different wavelengths of light, different fluences and different irradiances were compared, as well as laser light with noncoherent light. Wounds were followed up for three weeks.

Results showed that some mice healed significantly faster when compared to the control mice. This seems to be strain-dependent, and a new finding, according to Dr. Hamblin.

Many different aspects of wound healing can be tested in wounds, such as collagen synthesis by fibroblasts and angiogenesis.

This wound model tested the ability of light to induce myofibroblasts at the wound edge in the dermis, which are responsible for wound contraction. The mechanism is thought to be the conversion of fibroblasts in the wound edge to contractile, smooth-muscle actin-expressing myofibroblasts that prevent the initial wound expansion seen in mouse wounds in certain strains.

WAVELENGTH EFFECT

The four main wavelengths used were 632, 670, 730 and 810. The most beneficial results were seen with the 810 wavelength, followed by 632.

Dr. Hamblin says that the 730 does not evoke a positive result, possibly because there is no absorption peak. However, the longer and shorter wavelengths were shown to be very effective.

"What we showed was that a single exposure of light, 30 minutes after wounding, had a long-lasting effect, and the reason for that was because it induced myofibroblasts in the dermis at the wound edge that prevented the initial expansion of the wound.

"It caused contraction to set in several days earlier than it otherwise would," Dr. Hamblin tells Dermatology Times.

According to Dr. Hamblin, the wounds did not arrive at complete healing much earlier than they would have without any light, but the actual course of wound healing was significantly accelerated for most of the tests.