Photobiomodulation (PBM) is a regulatory approach that utilizes red or near-infrared (NIR) light to promote tissue repair and blood microcirculation, thereby generating positive therapeutic effects at multiple levels. In recent years, as an emerging non-invasive therapy, PBM has been widely applied in the modulation of neurodegenerative diseases. However, due to the light scattering and absorption characteristics in the skull and the incomplete understanding of the intracranial propagation properties of light at different wavelengths, the application of optical techniques in transcranial modulation is greatly limited. In order to optimize the light therapeutic efficacy of neurological diseases, there is an urgent need to investigate the physical property of light transcranial spread. In this work, the transmittance of NIR light at different power levels and frequencies in the mouse skull at various points were detected. Additionally, the penetrations of light at 808 nm and 660 nm with varying tissue thickness were compared by Monte Carlo simulation analysis, providing data support for establishing the optimal therapeutic strategy of transcranial PBM.
Meningeal lymphatic vessels (mLVs) have been confirmed to scavenge amyloid beta (Aβ) from brain and might been damaged early on by deleterious processes implicated in AD, which is considered as a novel target for Alzheimer’s disease (AD) treatment. However, whether modulation of mLVs in the early stage could delay pathological progression of AD remains unknown. In this study, based on the superficial distribution of mLVs in dura, a near-infrared light was utilized to modulate lymphatic drainage of 3-month AD mice, and the therapeutic effect and potential mechanism were investigated on the mice at 6 months of age. The results showed that light ameliorates cognitive deficits and AD-associated pathology of 6-month-old AD mice by preserving transport ability of mLVs since the early stage. This study provides a novel strategy for AD prevention and intervention via mLVs modulation in early time.
Photobiomodulation (PBM) is a type of phototherapy that uses red or near-infrared (NIR) light to stimulate healing or regeneration of tissues with injury or degradation. In recent years, PBM has been successfully used in the treatment of nervous system diseases. However, the application of optical technology in non-invasive transcranial therapy is greatly limited by the high scattering and absorbance of head tissues including scalp and skull, as well as the transcranial spread properties of light with different parameters still remain unclear. Therefore, for realization of phototherapy for brain diseases, in-depth understanding of the transcranial penetrability of light through head tissues is urgently needed. In this study, the wavelength dependence of light transmittance through scalp and skull of mice was investigated using a transcranial laser at wavelengths of 660 nm or 808 nm, which provides reference for future research and application of transcranial PBM.
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