Effect of intranasal treatment with NAMPT-EVs on acetylated tau and cognitive function in mice with repeated controlled cortical injury.

Abstract

BACKGROUND: Repeated traumatic brain injury (rTBI) has attracted increasing attention owing to its long-term effects on cognition and behaviour. Moreover, research has shown that acetylated tau (ac-tau) represents a common pathology linking rTBI and Alzheimer's disease that can lead to neuronal cell death. Therefore, in this study, we evaluated the therapeutic potential of mesenchymal stromal cell-derived extracellular vesicles enriched with nicotinamide phosphoribosyltransferase (NAMPT-EVs) for improving cognitive and behavioral impairments following repeated controlled cortical injury (rCCI). METHODS: Morris water maze and novel object recognition test were evaluated at 1-month post-rCCI with intranasal treatment of NAMPT-EVs. Expression of Sirtuin 1(SIRT1), ac-tau, neuron loss, neuroinflammation, AQP4 polarity, and meningeal lymphatic morphology and function were assessed 1 month after treatment. RESULTS: Intranasal administration of NAMPT-EVs significantly increased the expression of SIRT1 to deacetylate tau in rCCI mice. Additionally, NAMPT-EVs suppressed neuroinflammation and maintained aquaporin protein-4 polarity to facilitate the glymphatic system and promote the repair of the meningeal lymphatic system, which benefits the clearance of ac-tau from the brain parenchyma. Notably, the reduction in ac-tau prevented axon initial segment degradation and tau mislocalisation, resulting in a neuroprotective effect. CONCLUSIONS: NAMPT-EVs reduce neuronal loss and improve cognitive function in rCCI mice through multiple mechanisms. Therefore, NAMPT-EVs is promising for preventing cognitive deficit after rTBI.