Skin-tightening effect of fractional lasers: comparison of non-ablative and ablative fractional lasers in animal models.

This experimental study was performed to demonstrate the effects of non-ablative fractional laser (NAFL) and ablative fractional laser (AFL). Twenty male Sprague-Dawley rats were used for the study. Three 2×2-cm-sized squares were tattooed on the abdomen of the animals. Each tattooed square was used for NAFL, AFL and control experiments. The NAFL and AFL treatment were performed with the same total energy of 12,000 mJ cm(-2). The laser treatments consisted of four sessions, with an interval of 3 weeks between sessions. The areas of tattooed skin were serially measured, and skin samples were obtained for histologic examination after 4 months of treatment. NAFL did not cause immediate skin shrinkage, but the size of the NAFL-treated skin was reduced by 4.3% after 4 months. In contrast, AFL caused immediate skin shrinkage (11.5% reduction), and the size was maintained at 9% reduction after 4 months. In histologic examination, the dermal collagen was arranged flat and parallel to the skin surface in the upper dermis, and regenerated collagen fibres were clearly noticed in both NAFL-and AFL-treated skin samples. Immunohistochemical stains showed well-regenerated type I and III collagen fibres. Western blot analysis of skin samples showed that type I/III collagen ratio was not significantly changed after fractional laser treatment. Electron microscopic studies aimed to evaluate the long-term micro-architecture of the collagen fibrils. AFL treatment reduced D-band periodicity by 5.2% and fibril diameter by 14.8%, although there was no statistically significant difference (p>0.05). Fractional laser treatment shrinks the skin surface area and regenerates collagen. The AFL treatment showed more profound skin changes than NAFL.