Photobiomodulation effect on primary trigeminal ganglion neurons with near-infrared light

Abstract

Dry eye syndrome, also known as keratoconjuctivitis sicca, is a common eye disease that can be caused by a lack of adequate tear production. One of the causes of dry eye syndrome is damage to the nerve bundles of the cornea caused by ocular surgery such as laser-assisted in-situ keratomileuses (LASIK) and laser-assisted sub-epithelial keratectomy (LASEK) surgery. Photobiomodulation (PBM) therapy or low-level laser therapy (LLLT) refers to therapeutic approaches based on the interactions of visible or near-infrared (NIR) photons with biomolecules in the cells or tissues. NIR light irradiation on cells is known to generate photochemical responses majorly in mitochondria and nucleus. To yield effective therapeutic response, several parameters need to be optimized including wavelength, irradiance, radiant exposure, and the laser modes. In this study, we introduced a new system to stimulate the cultured primary trigeminal ganglion neuron (TgN) and compared the morphological growth between the irradiation group and non-irradiation group by illuminating the NIR (808 nm). In addition, we applied various radiant exposures of 1, 2, and 10 J/cm^2 with different frequencies of 1, 10, and 100 Hz. We found that NIR irradiation has an effect on neurite growth of TgN, and it works at low energy densities at the 1 and 2 J/cm^2. Irradiation frequency of 10 Hz is most effective than other frequencies. Thus, PBM with NIR irradiation on TgN cells facilitated neuronal growth in a dose and frequency-dependent fashion. NIR irradiation may provide a potential therapeutic approach to treat the injury of damaged TgN.