Journal of Clinical and Aesthetic Dermatology

DEC 2017

An evidence-based, peer-reviewed journal for practicing clinicians in the field of dermatology

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41 JCAD JOURNAL OF CLINICAL AND AESTHETIC DERMATOLOGY December 2017 • Volume 10 • Number 12 O R I G I N A L R E S E A R C H thickness of surgical scars, while pulsed dye laser (PDL) use was superior regarding treating vascularity and pigmentation. This suggests that firm, irregular scars are the best candidates to respond to fractional CO₂ laser use rather than erythematous, hyperpigmented ones. The initial management of hyperemic scars by PDL targeting the vasculature, followed by the fractional CO₂ laser, might be a more suitable plan for managing hyperemic scars. The significant improvement in scar thickness, pliability, and relief achieved by fractional CO₂ use in our study was shown by histological and histochemical analysis to be due to its effect on collagen and elastic fibers. The irregular sclerotic collagen fibers significantly changed to less sclerotic, finer, more fibrillar collagen, with a significant reduction in the amount of collagen fibers assessed morphometrically. Our findings were in agreement with Ozog et al, 7 Makboul et al, 12 and El-Zawahry et al. 10 Fractional CO₂ laser induces matrix metalloproteinases (MMPs), which clear the damaged collagen and allow for collagen remodeling to take place, with the formation of new, healthy collagen. 13 Similar effects were reported after fractional ablative and non- ablative Er:YAG treatment of photodamaged skin. 14 A significant improvement in the grading score of elastic fibers was detected in the current study, and morphometrically, the amount of elastic fibers increased significantly after treatment. Although not statistically significant, Ozog et al reported similar changes. 7 In contexts other than burn scars, Shin et al reported increased density of elastic fibers following fractional CO₂ laser treatment of striae distensae. 15 Also, Jiang et al performed a single pass fractional CO₂ laser session on mice dorsal skin and detected the replacement of lumps of old elastic fibers by slender elastic fibers with a wider distribution within few hours of fractional CO₂ resurfacing. 16 Improvement in scar vascularity by fractional CO₂ lasers occurred in our cases and this might be explained by the dermal blood vessels becoming less trapped and more perpendicular to the epidermis as a result of collagen remodeling. This observation was also reported by both Ozog et al 7 and Makboul et al. 12 In accordance with El-Zawahry et al, 10 our study showed no correlation between clinical and histological indices. This probably indicates that the clinical improvement in burn scars does not depend solely on the improvement of the arrangement and the amount of collagen and elastic fibers. It can be presumed that complex biochemical pathways elicited by fractional CO₂ laser, including changes at the cytokine level, also contribute to an improvement in scar pigmentation, vascularity, and patients' perception of their scars. We found that the shorter the scar duration, the better the improvement with fractional CO₂ laser. This finding is reiterated in the observation reported by Niwa et al, stating that scars less than one year in duration improve more FIGURE 5. Photomicrographs representing results of Masson's trichrome staining for collagen fibers for the same case presented in Figure 4, before treatment (A) and after treatment (B)—Reduction in collagen density (16% by image analysis) and improved collagen quality. (Masson's trichrome stain, original magnification x 40). FIGURE 4. Photomicrographs demonstrating histopathological grading of collagen fibers using routine H&E stain, before treatment (A) and after treatment (B)—The thick sclerotic collagen bundles (solid black arrows) in the scar tissue before treatment (Grade 5) changed to a combination of fibrotic (dotted black arrows) and fibrillar (red arrows) collagen, with vessels starting to appear in the scar tissue perpendicular to the epidermis after treatment (grade 2) (H&E staining original magnification x 40). A A B B

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