595-nm pulsed dye laser combined with fractional CO2 laser reduces hypertrophic scar through down-regulating TGFβ1 and PCNA.

595-nm pulsed dye laser and fractional CO2 laser have been demonstrated effective to treat hypertrophic scar. The underlying mechanism may involve transforming growth factor-beta1 (TGFβ1) and proliferating cell nuclear antigen (PCNA), but remains to be clarified. Our study was performed to investigate how 595-nm pulsed dye laser combined with fractional CO2 laser treats hypertrophic scars in a rabbit model through regulating the expression of TGFβ1 and PCNA. Twenty-four New Zealand white rabbits were randomly divided into control group, pulsed dye laser group, fractional CO2 laser group, and pulsed dye laser + fractional CO2 laser (combination) group. Surgical wounds were made and allowed to grow into hypertrophic scars at day 28. Next, 595-nm pulsed dye laser (fluence: 15 J/cm2; square: 7 mm; pulse duration: 10 ms) was used in pulsed dye laser and combination group, while fractional CO2 laser (combo mode, deep energy: 12.5 mJ; super energy: 90 mJ) in fractional CO2 laser and combination groups, once every 4 weeks for 3 times. The appearance and thickness of hypertrophic scar samples were measured with hematoxylin-eosin and Van Gieson's straining. The expressions of TGFβ1 and PCNA were evaluated by immunohistochemical and western blot analysis. A significant improvement was noted in the thickness, size, hardness, and histopathology of hypertrophic scar samples after laser treatment, especially in combination group. Scar Elevation Index (SEI), fiber density (NA), and collagen fiber content (AA) decreased most significantly in combination group (2.10 ± 0.14; 2506 ± 383.00; 22.98 ± 2.80%) compared to 595-nm pulsed dye laser group (3.35 ± 0.28; 4857 ± 209.40; 42.83 ± 1.71%) and fractional CO2 laser group (2.60 ± 0.25; 3995 ± 224.20; 38.33 ± 3.01%) (P < 0.001). Furthermore, TGFβ1 and PCNA expressions were more suppressed in combination group (8.78 ± 1.03; 7.81 ± 1.51) than in 595-nm pulsed dye laser (14.91 ± 1.68; 15.73 ± 2.53) and fractional CO2 laser alone group (15.96 ± 1.56; 16.13 ± 1.72) (P < 0.001). The combination of 595-nm pulsed dye laser with fractional CO2 laser can improve the morphology and histology of hypertrophic scars in a rabbit model through inhibiting the expression of TGFβ1 and PCNA protein. Our findings can pave the way for new clinical treatment strategies for hypertrophic scars.