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Photodynamic therapy may be beneficial for sun damaged skin, study

By Katie Bird , 21-Oct-2008

Laser treatment improves the appearance of sun damaged skin by increasing collagen production, according to scientists in Michigan.

Light-based therapies have been used for some time to improve skin appearance however, according to the researchers, little is known about the molecular mechanisms behind reported improvements.

The team based, at the University of Michigan Health System Department of Dermatology, set out to investigate the molecular effects resulting from pulsed dye-laser therapy, as well as the effect of pre-treatment with a topical photosensitizer.

After topical application of 5-aminolevulinic acid (5-ALA) that was left on the skin for three hours, 15 adult patients with significant photodamaged skin underwent pulsed dye-laser therapy to the forearm.

Increased markers for skin damage and repair

It is thought that most skin resurfacing treatments achieve results by removing layers of skin which results in new healthier skin emerging through the healing process.

Supporting this theory the team noted the increase in the levels of a number of molecular markers associated with skin damage and repair following the combination treatment.

The researchers, led by Jeffrey S. Orringer, noted an increase in the expression of cytokeratin 16, a market of epidermal irritation and injury, which was particularly exaggerated on day two following treatment.

Similarly, an increase in the expression of the matrix metalloproteinases gene 1 (MMP1) was recorded in the 24 hours following treatment. MMP1 is known to breakdown collagen, therefore an increase in its presence supports the idea that such treatments initially damage skin before healing can occur.

On the healing side, levels of the protein Ki67, a marker of keratinocyte proliferation, were significantly increased on days two and seven post treatment. In addition, and probably as a result of keratinocyte proliferation, the team recorded a thickening of the epidermis after treatment, an effect that lasted up to a month post therapy.

Furthermore, Levels of both type I procollagen mRNA and type III procollagen mRNA (precursors to two of the most important structural proteins in the skin) increased following treatment with the effect lasting up to a month, according to the study.

Treatment improved with prior ALA application

The study was not designed to compare the efficacy of pulsed-dye laser treatment on its own to the laser treatment supported by the application of the photosensitizer ALA, the researchers explained.

However, the team compared the results to prior research investigating the laser treatment alone and concluded the addition of the photosensitizer significantly improved results.

Source: Archives Dermatology
Volume 144, Issue 10, October 2008
Molecular effects of photodynamic therapy for photoaging
Jeffrey S. Orringer, Craig Hammerberg, Ted Hamilton, Timothy M. Johnson, Sewon Kang, Dana L. Sachs, Gary Fisher, John J. Voorhees

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