Researchers at the University of Michigan have found that photodynamic therapy using topical 5-aminolevulinic acid (5-ALA) and pulsed-dye laser treatment produces statistically significant quantitative cutaneous molecular changes—specifically the production of type I and III collagen. These changes are associated with an improvement in the skin's appearance.
The damaging effects of ultraviolet irradiation to the skin are well known. In recent years, several visible and infrared light sources and lasers have been found to improve the clinical and histologic appearance of the skin, and using a photosensitizing compound to enhance the effects of these therapies has been advocated.Jeffrey S. Orringer, M.D., clinical assistant professor, Department of Dermatology, University of Michigan, Ann Arbor, and his colleagues conducted the study "to quantitatively examine the epidermal and dermal cellular and molecular changes that occur after photodynamic therapy of photodamaged human skin."
The study included 25 patients between the ages of 54 and 83 years who had clinically evident photodamage on the skin of their forearms that was rated by investigators as "at least moderate in severity." Fifteen patients were women and 10 were men.
Exclusion criteria included the following:
In these study participants, 5-ALA was applied for three hours. Treated areas measured approximately 2.5 cm x 8.0 cm. After the treatment site was washed with Cetaphil cleanser, pulsed-dye laser therapy was applied to focal areas of patients' photodamaged forearms using non-purpura-inducing settings: 595-nm wavelength, 10-mm spot size, 10-ms pulse duration and a fluence of 7.5 J/cm2 . After laser therapy, the treatment site was washed with Cetaphil cleanser and covered with a bandage.
To evaluate the changes, biopsy specimens were obtained at baseline, and patients were re-evaluated and provided additional skin biopsy samples four to five times during the first six months after treatment. Twenty-four of the patients provided at least four skin biopsy samples. One patient developed contact dermatitis from the adhesive in the bandage placed after treatment and was excluded from the study.
The researchers used immunohistochemical analysis to assess patients' levels of epidermal proliferation (Ki67), epidermal injury (cytokeratin 16) and photodamage (p53). They also assessed markers of dermal collagen production, which included prolyl 4-hydroxylase, heat shock protein 47 and type I procollagen. To assess the amount of type I and type III collagen, real-time reverse transcriptase-polymerase chain reaction technology was used. Enzyme-linked immunosorbent assay was used to assess the amount of type I procollagen protein.
This treatment resulted in a 5-fold increase in Ki67 and a 1.4-fold increase in epidermal thickness. Additionally, the treatment produced epidermal injury, which was demonstrated by cytokeratin 16 levels that were 70-fold higher after treatment compared with baseline levels.
The researchers also observed upregulation of collagen production, which was demonstrated with 2.65-fold increases in procollagen I messenger RNA, 3.32-fold increases in procollagen III messenger RNA, and 2.42-fold increases in procollagen I protein levels.
"The baseline epidermal p53 level correlated with cytokeratin 16 levels at acute time points, and the latter were found to correlate with peak collagen production," the researchers report.
In other words, patients' dermal responses to this therapy regimen may be predicted by baseline epidermal p53 immunostaining levels. The investigators compared their results with historical data using pulsed-dye laser therapy alone, and they found that the use of the photosensitive compound in conjunction with laser therapy may provide more beneficial changes in the skin.
OTHER LIGHT SOURCES
The results of this study suggest that using a photosensitive compound may enhance the results obtained with other light sources. "For physicians already using visible light sources, such as IPL and some lasers, the findings of this study suggest that clinical results in terms of photorejuvenation might be enhanced by including the use of a topical photosensitizer (like Levulan [20% 5-ALA solution]) in the treatment regimen. The results of this study are specific to the topical photosensitizer (5-ALA) and light source (pulsed-dye laser) used. However, there is reason to believe that other light sources such as IPL devices might produce similar or even more profound molecular and clinical changes," Dr. Orringer says. He notes that this study was a "proof in principles" protocol in some respects because it examined the molecular effects of photodynamic therapy using a fairly long photosensitizer application time. Further studies are needed to determine whether shorter application times of the photosensitive compound would produce similar changes in the skin. "The study is an attempt to quantify the molecular and cellular changes brought about in the skin by a specific photodynamic therapy regimen. Several key findings provide evidence for the validity of this clinical treatment approach, including evidence of substantial dermal remodeling, collagen production, and epidermal thickening that result from photodynamic therapy. These results are part of an evolving molecular model that we believe will one day help predict the clinical value of new cosmetic interventions. We believe that the quantitative amount of dermal repair and regeneration induced by a specific treatment likely underlies the degree of clinical rejuvenation produced," he concludes.
Orringer JS, Hammerberg C, Hamilton T, et al. Molecular effects of photodynamic therapy for photoaging. Arch Dermatol. 2008;144:1296-1302.
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Jeffrey S. Orringer, M.D.