Low-level laser irradiation promotes the proliferation and maturation of keratinocytes during epithelial wound repair

Low‐level laser therapy (LLLT) has been extensively employed to improve epithelial wound healing, though the exact response of epithelium maturation and stratification after LLLT is unknown. Thus, this study aimed to assess the in vitro growth and differentiation of keratinocytes (KCs) and in vivo wound healing response when treated with LLLT. Human KCs (HaCaT cells) showed an enhanced proliferation with all the employed laser energy densities (3, 6 and 12 J/cm2, 660 nm, 100 mW), together with an increased expression of Cyclin D1. Moreover, the immunoexpression of proteins related to epithelial proliferation and maturation (p63, CK10, CK14) all indicated a faster maturation of the migrating KCs in the LLLT‐treated wounds. In that way, an improved epithelial healing was promoted by LLLT with the employed parameters; this improvement was confirmed by changes in the expression of several proteins related to epithelial proliferation and maturation. Immunofluorescent expression of cytokeratin 10 (red) and Cyclin D1 (green) in (A) Control keratinocytes and (B) Low‐level laser irradiated cells. Blue color illustrates the nuclei of the cells (DAPI staining). Low‐level laser therapy accelerates the epithelium maturation during wound healing; this picture illustrates how the immunohistochemical expression of cytokeratin 10, a terminal differentiation biomarker, is significantly augmented in the keratinocytes of the laser‐irradiated lesion if compared to the control group. The center of the wound (CW) shows complete re‐epithelialization; the covering epithelium over the connective tissue (CT) notably expresses cytokeratin 10.