Low-level green laser promotes wound healing after carbon dioxide fractional laser therapy

The carbon dioxide (CO₂ ) fractional laser resurfacing has become one of the hottest therapies for dermatoses. However, complications such as skin swelling, prolonged erythema, post-inflammatory hyperpigmentation, and scar formation remain. Low-level laser (LLL) therapy is accepted to promote skin wound healing and regeneration, decrease inflammation and pain, and modulate immunoreaction with low-dose laser of different wavelength. 532 nm laser therapy is commonly used to remove pigmented spots and to tender skin, but not utilized in wound care.

We aimed to determine the efficacy of the low-level 532 nm green laser in wound healing after CO₂ fractional laser.

Six adult male mice (C57BL/6, 8 weeks old) were prepared for animal experiments. The dorsum of each mouse was divided into four parts that, respectively, received designed treatments, as controlled (group Ctrl), 532 nm LLL-treated (group GL), CO₂ fractional laser-treated (group FL), and CO₂ fractional laser followed by three times 532 nm LLL-treated (group FG). Hematoxylin-eosin staining (H&E), Masson-trichrome staining, CD31 immunohistochemical staining were performed to evaluate the efficacy of wound healing after treated by different irradiations. Western blotting was used to detect the expression of related proteins. Mouse skin fibroblasts (MSFs) were treated with LLL using a wavelength of 532 nm once. Cellular responses were observed and analyzed after 48 hours. Cell viability and migration of different groups were assessed by scratch and the Cell Counting Kit-8 (CCK8) assays, respectively.

Collagen remodeling and epidermis thickness were significantly enhanced in group FG than that in group FL in morphology. Besides, CD31 immunohistochemical staining indicated prominently increased angiogenesis in both groups FL and FG than non-irradiation group. The expression of extracellular matrix (ECM)-related protein (Col1, Col3 and MMP1) showed a remarkable improvement in wound healing in group FG than that in group FL. Irradiated MSFs showed a better migration ability compared with non-irradiated controls. LLL enhanced the secretion function of MSFs on Collagen I and III.

Low-level green laser promotes wound healing after CO₂ fractional laser by improving the integrity of skin barrier and allowing for scarless healing. Therefore, low-level green laser therapy might serve as a sequential therapy of invasive laser surgery to ensure a better wound care.