Biostimulatory effect of low-level laser therapy on keratinocytes in vitro

Epithelial cells play an important role in reparative events. Therefore, therapies that can stimulate the proliferation and metabolism of these cells could accelerate the healing process. To evaluate the effects of low-level laser therapy (LLLT), human keratinocytes were irradiated with an InGaAsP diode laser prototype (LASERTable; 780 +/- 3 nm; 40 mW) using 0.5, 1.5, 3, 5, and 7 J/cm(2) energy doses. Irradiations were done every 24 h totaling three applications. Evaluation of cell metabolism (MTT assay) showed that LLLT with all energy doses promoted an increase of cell metabolism, being more effective for 0.5, 1.5, and 3 J/cm(2). The highest cell counts (Trypan blue assay) were observed with 0.5, 3, and 5 J/cm(2). No statistically significant difference for total protein (TP) production was observed and cell morphology analysis by scanning electron microscopy revealed that LLLT did not promote morphological alterations on the keratinocytes. Real-time polymerase chain reaction (qPCR) revealed that LLLT also promoted an increase of type I collagen (Col-I) and vascular endothelial growth factor (VEGF) gene expression, especially for 1.5 J/cm(2), but no change on fibroblast growth factor-2 (FGF-2) expression was observed. LLLT at energy doses ranging from 0.5 to 3 J/cm(2) promoted the most significant biostimulatory effects on cultured keratinocytes.