image: (A) Experimental schematic diagram. (B to D) PBM therapy apparatus (C) including a touchscreen control (B) and a lens (D). (E) The rats were fixed in a stereotaxic apparatus during PBM therapy. (F) Schematic illustration of the lens placed outside the skull, above the brain. The red box delineates the proposed treatment area. (G) Temperature: Surface temperature of the irradiated area of the rat brain before and after phototherapy. The surface temperatures of the irradiated area in the rat brain, measured at wavelengths of 638, 755, and 808 nm, showed no significant difference compared to pre-irradiation levels.
Credit: Hongbin Han, Department of Radiology, Peking University Third Hospital
Ischemic stroke exacts a heavy toll in death and disability worldwide. After ischemic stroke, the accumulation of pathobiomolecules in the brain extracellular space (ECS) will exacerbate neurological damage and cognitive impairment. “PBM has been demonstrated to improve cognitive function in Alzheimer’s disease mouse models by accelerating molecular transportation in the brain ECS. This suggests that PBM may have a potential role in the accumulation of pathobiomolecules in the brain ECS following ischemic stroke.” said study author Hongbin Han, a professor at Peking University Third Hospital. Recent research has revealed that PBM can accelerate ISF drainage by reducing the tortuosity and enhancing diffusion in the brain ECS. Irradiation with 630 nm red light reverses the Aβ-impeded interstitial fluid (ISF) flow and improves memory decline of APP/PS1 mice. This suggested that an essential pathway by which PBM exerts its neuroprotective effects is through modulation of the brain ECS.
In this study, authors developed a PBM therapy apparatus with custom parameters. By evaluating the treatment effect, the author identified that 755 nm was the optimal light wavelength for ischemic stroke in rats with transient middle cerebral artery occlusion/ reperfusion. Extracellular diffusion and ISF drainage were measured using a tracer based magnetic resonance imaging method. Results showed that PBM accelerated molecular transportation in the brain ECS and ISF drainage, promoting the clearance of pro-inflammatory cytokines and reducing the deposition of pathological proteins. Consequently, the infarct volume decreased and neurological cognitive function was improved. Besides, the acceleration of ISF drainage was achieved by reducing expression and restoring polarization of aquaporin 4 (AQP4) in the periinfarct area.
In summary, this paper highlights the neuroprotective effects of 755 nm light via the acceleration of ISF drainage during ischemic stroke. This study provides invaluable insight into the mechanisms by which 755 nm light modulates the brain ECS. PBM therapy offers a minimally invasive and effective approach that holds promise for treating ischemic strokes.
Authors of the paper include Liu Yang, Yajuan Gao, Leonor Serrano Lopes, Jingge Lian, Wanyi Fu, Hanbo Tan, Shuangfeng Yang, Zhaoheng Xie, Yixing Huang, Jicong Zhang, Yanye Lu, Hao Tang, Bo Xiong, Xunbin Wei, Lide Xie, Yun Peng, Xinyu Liu, and Hongbin Han.
This work was supported by the Major Program of the National Natural Science Foundation of China (grant no. 62394314), the National Natural Science Foundation of China (grant no. 12171330), the Youth Fund of the National Natural Science Foundation of China (grant nos. 62401022 and 62301245), the Science and Technology Program of Guangzhou (grant no. 2023A04J0531), the China Postdoctoral Science Foundation (grant no. 2022M720294), and the National Natural Science Foundation of China (grant no. 62450130).
The paper, “Accelerated Molecular Transportation in the Brain Extracellular Space with 755-nm Light Attenuates Post-Stroke Cognitive Impairment in Rats” was published in the journal Cyborg and Bionic Systems on May 6, 2025, at DOI: 10.34133/cbsystems.0262.
Journal
Cyborg and Bionic Systems