Running exercise mitigates amyloidosis in 5xFAD mice by improving the structure and function of the meningeal lymphatic system

Abstract

Background: Alzheimer’s disease (AD) progression is closely linked to the accumulation of amyloid- (A), with impaired clearance mechanisms playing a key role. The meningeal lymphatic (mLym) system, which drains cerebrospinal fluid (CSF) and waste from the brain to peripheral lymph nodes, has emerged as a critical pathway for A removal. While physical exercise is known to improve cognitive function and reduce AD risk, its effect on the mLym system and downstream AD pathology have not been fully elucidated. Methods: Three-month-old 5xFAD mice underwent a 3-month wheel-running exercise regimen. The function of the mLym system was assessed before and after exercise using high-frequency ultrasound imaging with nanoparticle tracers to monitor CSF drainage to deep cervical lymph nodes. The study evaluated changes in mLym vessel structure, A deposition, and cognitive performance. Additionally, the effects of serum and extracellular vesicles (EVs) from exercised rats on the expression of lymphatic vessel-related genes (LYVE-1, VEGFR3, and VEGF-C) were examined in lymphatic endothelial and microglial cell lines. Results: Compared to 3-month-old 5xFAD mice and age-matched wild-type controls, 6-month-old 5xFAD mice displayed progressive decline in mLym function, reduced vessel integrity, and increased amyloid plaque burden, accompanied by impaired learning and memory. These changes were associated with decreased expression of LYVE-1 and VEGFR3 in the meninges and VEGF-C in the brain. Exercise intervention reversed these deficits, restoring mLym function and vessel structure, enhancing A clearance, and improving cognitive performance. Surgical ligation of mLym vessels accelerated amyloid accumulation and removed the exercise-induced benefits, underscoring the system’s importance in A removal. In vitro, A oligomers suppressed VEGFR3 and VEGF-C expression, while serum and EVs from exercised rats counteracted this effect. Proteomic analysis of EVs from exercised animals revealed upregulation of CD9, suggesting a link to VEGFR3 signaling. Conclusions: This study demonstrates that A oligomers impair mLym function, exacerbating amyloid pathology. Exercise preserves the structure and function of the mLym system, promoting A clearance and mitigating AD progression. These findings highlight the therapeutic potential of targeting the meningeal lymphatic system to slow or prevent AD.