Study Of Topical 5-ALA Photodynamic Therapy On Guinea Pig Photoaging Model

Objective To evaluate the efficacy of 5-aminolevulinic acid (ALA) with intense pulsed-light (IPL), known as photodynamic therapy (PDT) on guinea pig photoaging model and to set up the proper concentration of ALA.Methods The guinea pig photoageing model was set up by chronic sun-simulating radiation (SSR) exposure. The guinea pigs were divided into four groups and there were six guinea pigs in each group. The first group was normal while the second group was photoaged by SSR. The third group was spontaneous recovery after SSR. The skin of the last group were divided into three parts, sperately treated by topical matrix cream,10% ALA or 20%ALA combined with IPL and the animals received one treatment every 3 weeks. Dermal structure, including elastic and collagen fiber was observed after Hematoxylin-eosin stain, Weigert's stain and Siriured stain, while ultra structure of dermal, including fibroblasts, elastic and collagen fiber was observed by transmission electron microscopy. All the animals were of the same age.Results Albino guinea pigs were subjected to suberythemal dose of SSR 3 times a week after being hair-removed by the mixture of rosin and paraffin wax. Thirteen weeks after exposure, there was typical "solar elastosis" damage in the upper dermis. Mature elastic fibers were severely degraded and there was large amount of elastotic material accumulated in the upper dermis. Collagen I and Collagenâ…¢were degraded and disorderly. Mitochondria in dermal fibroblasts were damaged and rough endoplasmic reticulum was rare. ALA at concentration of 10% with IPL improved the photodamage changes significantly after being treated 3 times, for reducing the "solar elastosis" damage in the upper dermis, Collagenâ… and Collagenâ…¢trending to be well-arranged, more long fibers and break reduction. Vacuolization of mitochondria in dermal fibroblasts was relieved with the expansion of endoplasmic reticulum. So the efficacy of 10% ALA with IPL was significantly better than that of matrix cream with IPL. Although ALA at concentration of 20% with IPL improved the damage and repaired the injury, the efficacy was not increased and it even worsened the "solar elastosis" damage. Vacuolization of mitochondria in fibroblasts was in general and obvious.Conclusions Topical 5-ALA PDT has rejuvenation effects on photoaging and its efficacy is better than that of IPL only. It is important to choose proper concentration of ALA and concentration of 10% may be the more suitable.