Efficacy of non-ablative fractional laser at different energy and density in the early treatment of hyperplastic scars in a rabbit ear model: a clinical observation

Abstract

Objective To preliminarily optimize the energy and density of laser radiation for the early treatment of hyperplastic scars in a rabbit ear model, and to explore possible therapeutic mechanisms. Methods Sixty-one hyperplastic scars were successfully established on the ears of 10 healthy New Zealand white rabbits with large ears, and randomly divided into 2 groups: 1-week group (30 scars) and 3-week group (31 scars) . These 2 groups were separately divided into 5 subgroups: group A treated with laser at a density of 100 PPA and an energy of 10 mJ, group B with laser at a density of 100 PPA and an energy of 50 mJ, group C with laser at a density of 169 PPA and an energy of 10 mJ, group D with laser at a density of 169 PPA and an energy of 50 mJ, and group E receiving no treatment. There were 6 scars in each group, except the group E in the 3-week group. Two healthy New Zealand white rabbits with large ears were not subjected to modeling, and served as group F (blank control group) . Immunohistochemical study was performed to determine the expression of matrix metalloproteinase (MMP) -13 in the skin tissues from the rabbit ears 1 week after the treatment. Three weeks after the treatment, the skin tissues from the rabbit ears were subjected to hematoxylin-eosin (HE) staining and Masson staining. Then, the structure of scars was observed, and scar elevation index was calculated. Statistical analysis was carried out by Kruskal-Wallis H test for the comparison of scar elevation index, and by one-way analysis of variance (ANOVA) for the comparison of the average absorbance value of MMP-13. Results As HE staining revealed, the groups A, B, C and D all showed thicker dermis and increased number of collagen fibers compared with the group F (normal skin tissues) , but showed thinner dermis, decreased number and more ordered arrangement of collagen fibers compared with the group E (untreated scar tissues) . No obvious difference was observed in the thickness of the dermis among the groups A, B, C and D. The scar elevation index significantly differed among the 6 groups (H= 22.757, P 0.05) . Conclusions Non-ablative fractional laser is effective for the treatment of early-stage hyperplastic scars. At the same laser density, 50-mJ laser was superior to 10-mJ laser for the treatment of hyperplastic scars, likely because high-energy laser can stimulate the recombi-nation of extracellular matrices and up-regulated MMP-13 expression to a greater extent. Key words: Cicatrix, hypertrophic; Lasers; Matrix metalloproteinase 13; Fractional laser; Energy