Skin photorejuvenation effects of light-emitting diodes (LEDs): a comparative study of yellow and red LEDs invitro and invivo

BackgroundRed-coloured light-emitting diodes (LEDs) can improve skin photorejuvenation and regeneration by increasing cellular metabolic activity. AimTo evaluate the effectiveness of visible LEDs with specific wavelengths for skin photorejuvenation invitro and invivo. MethodsNormal human dermal fibroblasts (HDFs) from neonatal foreskin were cultured and irradiated invitro by LEDs at different wavelengths (410-850nm) and doses (0-10J/cm(2)). In vivo experiments were performed on the skin of hairless mice. Expression of collagen (COL) and matrix metalloproteinases (MMPs) was evaluated by semi-quantitative reverse transcription PCR (semi-qRT-PCR), western blotting and a procollagen type I C-peptide enzyme immunoassay (EIA). Haematoxylin and eosin and Masson trichrome stains were performed to evaluate histological changes. ResultsIn HDFs, COL I was upregulated and MMP-1 was downregulated in response to LED irradiation at 5952 and 630 +/- 8nm. In the EIA, a peak result was achieved at a dose of 5J/cm(2) with LED at 595 +/- 2nm. In vivo, COL I synthesis was upregulated in a dose-dependent manner to both 595 and 630nm LED irradiation, and this effect was prolonged to 21days after a single irradiation with a dose of 100J/cm(2). These histological changes were consistent with the results of semi-qRT-PCR and western blots. ConclusionSpecific LED treatment with 595 +/- 2 and 630 +/- 8nm irradiation was able to modulate COL and MMPs in skin, with the effects persisting for at least 21days after irradiation. These findings suggest that yellow and red LEDs might be useful tools for skin photorejuvenation.