Background and Objectives: Low level light therapy (LLLT) is the treatment modality which is using photobiomodulatory effect of visible to near infrared spectrum light. LLLT is used in clinically to preventing hypertrophic scar or keloid and stimulating wound healing, while the mechanism of their effects remains unclear. Therefore, we investigated the effect of 415 nm, 632 nm, and 830 nm light emitting diodes (LED) to wound healing, especially in normal dermal fibroblasts and keloid dermal fibroblasts.
Material and methods: Normal fibroblasts and keloid fibroblasts were isolated from human. As preliminary study, we measured the viability of normal and keloid fibroblasts using EZ-CyTox viability assay after 24 hours from irradiation with 3, 10, and 30 J/cm2 of each wavelength. Proliferation rate of both fibroblasts relative to nonirradiated controls were measured using trypan blue exclusion assay after 24 hours from irradiation with 3, 10, and 30 J/cm2 of each wavelength. After suitable fluence was determinated, further repeated proliferation experiences were conducted. For migration assay, we made a scratched straight on the center of disc by sterile pipette tip and calculated migration rate by the filled area after 24 hours into the hollow space.
Results: There was no statistically significant effect of LLLT on both normal and keloid fibroblasts in viability assay. Because irradiation at 3, 10, and 30 J/cm2 of each wavelength made similar effect to normal fibroblasts, we decided to irradiate normal fibroblasts at fluence of 3 J/cm2. Because keloid fibroblasts increased their proliferation rate after irradiation at 3 J/cm2, we decided to irradiate keloid fibroblasts at fluence of 10 J/cm2. Normal fibroblasts irradiated with 632 nm at 3 J/cm2 showed significantly higher proliferation rate (p=0.034) and keloid fibroblasts irradiated with 632 nm at 10 J/cm2 showed significantly lower proliferation rate (p=0.010). In migration assay, normal fibroblasts showed significantly higher migration rate in 830 nm wavelength and keloid fibroblasts showed no significant difference between wavelengths.
Conclusion: At the aspect of fibroblasts, 632 nm LLLT could accelerate proliferation of normal fibroblasts, and inhibit proliferation of keloid fibroblasts. Furthermore, 830 nm LLLT could aid wound healing by increasing migration of normal fibroblasts. LLLT could modify proliferation or migration of fibroblasts, and that could stimulate wound healing and prevent hypertrophic scar or keloid.
