Early changes to the extracellular space in the hippocampus under simulated microgravity conditions

• Published in: Science China. Life sciences Vol. 65; no. 3; pp. 604 - 617
• Main Authors: Gao, Yajuan, Han, Hongbin, Du, Jichen, He, Qingyuan, Jia, Yanxing, Yan, Junhao, Dai, Hui, Cui, Bin, Yang, Jing, Wei, Xunbin, Yang, Liu, Wang, Rui, Long, Ren, Ren, Qiushi, Yang, Xing, Lu, Jiabin
• Format: Journal Article
• Language: English
• Published: Beijing Science China Press 01.03.2022; Springer Nature B.V
• Subjects: Animals; Biomedical and Life Sciences; Drainage; Extracellular Fluid; Extracellular matrix; Extracellular Space - diagnostic imaging; Hippocampus; Hippocampus - diagnostic imaging; Hippocampus - pathology; Life Sciences; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Male; Microgravity; Neuroimaging; Neuroprotection; Rats; Rats, Sprague-Dawley; Research Paper; Unloading; Weightlessness Simulation; interstitial fluid; interstitial system; tracer-based magnetic resonance imaging; brain extracellular space; hindlimb-unloading; simulated microgravity
• DOI: 10.1007/s11427-021-1932-3
• ISSN: 1674-7305; 1869-1889

The smooth transportation of substances through the brain extracellular space (ECS) is crucial to maintaining brain function; however, the way this occurs under simulated microgravity remains unclear. In this study, tracer-based magnetic resonance imaging (MRI) and D ECS -mapping techniques were used to image the drainage of brain interstitial fluid (ISF) from the ECS of the hippocampus in a tail-suspended hindlimb-unloading rat model at day 3 (HU-3) and 7 (HU-7). The results indicated that drainage of the ISF was accelerated in the HU-3 group but slowed markedly in the HU-7 group. The tortuosity of the ECS decreased in the HU-3 group but increased in the HU-7 group, while the volume fraction of the ECS increased in both groups. The diffusion rate within the ECS increased in the HU-3 group and decreased in the HU-7 group. The alterations to ISF drainage and diffusion in the ECS were recoverable in the HU-3 group, but neither parameter was restored in the HU-7 group. Our findings suggest that early changes to the hippocampal ECS and ISF drainage under simulated microgravity can be detected by tracer-based MRI, providing a new perspective for studying microgravity-induced nano-scale structure abnormities and developing neuroprotective approaches involving the brain ECS.