Introduction

Alzheimer's disease (AD) is a neurodegenerative disorder characterized primarily by progressive cognitive dysfunction and memory decline, and its onset and progression are closely associated with the aging process. Its core pathological features include abnormal deposition of amyloid-β (Aβ) plaques and the formation of neurofibrillary tangles composed of hyperphosphorylated microtubule-associated protein, phosphorylated Tau (P-Tau) [1]. The accumulation of these pathological proteins leads to synaptic damage, neuronal loss, and neuroinflammation, ultimately resulting in severe cognitive deficits [2]. Currently, clinical treatment of AD primarily relies on cholinesterase inhibitors and N-methyl-D-aspartate (NMDA) receptor antagonists to alleviate symptoms in patients with moderate to severe disease, but it cannot stop or reverse the disease progression [3]. In recent years, monoclonal antibodies targeting Aβ (such as aducanumab and lecanemab) have been approved for early-stage AD treatment, demonstrating disease-modifying potential. However, they still face challenges such as high cost, risk of side effects, and limited efficacy [4,5]. Overall, existing therapies are fundamentally limited by their inability to effectively cross the blood-brain barrier (BBB), difficulty in clearing pathological proteins already formed, incapacity to repair damaged neurons, and relatively late treatment windows. Therefore, developing novel therapeutic strategies that are precisely targeted, effectively intervene, and possess high safety remains a critical challenge awaiting breakthrough.

Exosomes (EXOs) are nano-sized vesicles actively secreted by cells, carrying bioactive substances such as proteins and nucleic acids. Due to their inherent biocompatibility, low immunogenicity, and potential to cross biological barriers, they have emerged as promising natural carriers in the fields of drug delivery and disease therapy [6]. In recent years, EXO-based therapeutic strategies have shown unique promise for age-related diseases, particularly neurodegenerative disorders such as AD. Ashok et al. utilized EXOs engineered with Fe65 and loaded with the compound corynoxine-B to significantly enhance autophagy function and improve cognitive behavior in AD model animals [7]. Another study found that hypoxia-preconditioned mesenchymal stem cell-derived EXOs could ameliorate synaptic dysfunction, modulate the inflammatory response in APP/PS1 mice, and mitigate cognitive decline [8].

To date, the role of blood-derived EXOs from young individuals in reversing age-related functional decline has attracted significant attention. Studies have shown that plasma-derived EXOs from young individuals demonstrate potential in ameliorating age-related functional decline and memory deficits [9]. Similarly, young serum-derived EXOs have also been shown to ameliorate age-related cognitive decline in aged mice [10]. In contrast to young EXOs, EXOs secreted by senescent cells may carry and transmit senescence-associated secretory phenotype components, such as pro-inflammatory factors, reactive oxygen species, and dysregulated microRNAs (miRNAs), thereby exacerbating neuroinflammation, oxidative stress, and cellular dysfunction, potentially promoting the progression of AD pathology [11]. Although young plasma-derived EXOs have attracted significant attention in the field of anti-aging, their direct therapeutic efficacy in AD treatment, the synergistic amplification effect following engineering modification, and the underlying molecular mechanisms have not yet been systematically elucidated.

Furthermore, natural EXOs inherently suffer from poor in vivo targeting ability and difficulty in accumulating at specific lesion sites (such as the brain), greatly limiting their therapeutic application [12]. The rabies virus glycoprotein (RVG)-derived peptide (RVG-29) can specifically recognize acetylcholine receptors on the neuronal surface and has been demonstrated to effectively mediate carriers in crossing the BBB and targeting neurons [13]. To enhance the delivery efficiency of young plasma-derived EXOs to neurons, this study performed surface engineering modifications on these EXOs. The targeting peptide RVG-29, which can specifically recognize neuronal surface receptors, was selected and conjugated onto the surface of young plasma EXOs via a lipid-anchoring method to construct RVG-EXOs.

Autophagy is a critical intracellular pathway involved in the clearance of misfolded proteins and damaged organelles, and its dysfunction has been closely linked to the pathogenesis of various neurodegenerative diseases, including AD [7,14,15]. Mammalian target of rapamycin complex 1 (mTORC1) serves as a key negative regulator of autophagy, and regulatory-associated protein of mTOR (RPTOR), also known as Raptor, as the core scaffold protein of mTORC1, plays a central role in autophagy regulation by mediating the inhibitory effect of mTORC1 on the ULK1 autophagy initiation complex [16]. Recent studies have suggested a potential association between RPTOR and the pathological progression of AD [17]. However, whether RPTOR can serve as a molecular target for exosome-based therapy has not yet been reported. The goals of our study were to: (1) using an AD cell model and a 3xTg transgenic mouse model to evaluate the brain delivery efficiency and neuronal targeting capability of RVG-EXOs, and analyze their effects on Aβ deposition, P-Tau levels, and the cognitive behavior of mice; (2) employing molecular biology approaches to investigated the mechanisms by which RVG-EXO intervention promotes the clearance of pathological proteins and exerts neuroprotective effects.