Photobiomodulation of lymphatic drainage and clearance: perspective strategy for augmentation of meningeal lymphatic functions
Alzheimer's Disease (AD) is the most common cause of dementia, a general term for loss of memory and other cognitive abilities serious enough to interfere with daily life. In the U.S., approximately 5.5 million people are affected, and the prevalence worldwide is estimated to be as high as 24 million. Despite the worldwide effort to find ways to treat the disease, delay its onset, and prevent it from developing, there are still no drugs that provide an effective therapy. This is why non-pharmacological methods of therapy for AD are being actively researched. It has been proposed, for example, that augmentation of drainage and clearing function of the meningeal lymphatic vessels (MLVs), which play an essential role in maintaining brain homeostasis by draining macromolecules from the Central Nervous System (CNS) into the cervical lymph nodes, could be a promising therapeutic target for preventing or delaying AD. The latest manuscript by Oxana Semyachkina-Glushkovskaya et al. explores this avenue for AD’s treatment by presenting very promising results on the effects of Photobiomodulation (PBM) on lymphatic drainage and clearance. In their pilot studies on mice models of AD, they observed that a 9-day course of transcranial photobiomodulation (tPBM, 1267 nm, 32 J/cm2) reduced beta-amyloid plaques in the brain, which is associated with improving memory and neurocognitive deficit. Additionally, using their original method based on optical coherence tomography (OCT) analysis of clearance of gold nanorods from the brain, they hypothesized that the tPBM-mediated stimulation of lymphatic drainage indeed might be a possible mechanism underlying the tPBM elimination of beta-amyloid from the brain. These very exciting results clearly validate an earlier hypothesis and provide strong incentive for continued development of this breakthrough strategy for an alternative, non-pharmacological therapy for AD.