Exosomes derived from bone-marrow mesenchymal stem cells alleviate cognitive decline in AD-like mice by improving BDNF-related neuropathology

Abstract

Background Alzheimer's disease (AD) is a neurodegenerative disease characterized by a progressive decline in cognitive ability. Exosomes derived from bone-marrow mesenchymal stem cells (BMSC-exos) are extracellular vesicles that can execute the function of bone-marrow mesenchymal stem cells (BMSCs). Given the versatile therapeutic potential of BMSC and BMSC-exos, especially their neuroprotective effect, the aim of this study was to investigate the potential effect of BMSC-exos on AD-like behavioral dysfunction in mice and explore the possible molecular mechanism. Methods BMSC-exos were extracted from the supernatant of cultured mouse BMSCs, which were isolated from the femur and tibia of adult C57BL/6 mice, purified and sorted via flow cytometry, and cultured in vitro. BMSC-exos were identified via transmission electron microscopy, and typical marker proteins of exosomes were also detected via Western blot. A sporadic AD mouse model was established by intracerebroventricular injection of streptozotocin (STZ). Six weeks later, BMSC-exos were administered via lateral ventricle injection or caudal vein injection lasting five consecutive days, and the control mice were intracerebroventricularly administered an equal volume of solvent. Behavioral performance was observed via the open field test (OFT), elevated plus maze test (EPM), novel object recognition test (NOR), Y maze test (Y-maze), and tail suspension test (TST). The mRNA and protein expression levels of IL-1β, IL-6, and TNF-α in the hippocampus were measured via quantitative polymerase chain reaction (qPCR) and Western blot, respectively. Moreover, the protein expression of Aβ1-42, BACE, IL-1β, IL-6, TNF-α, GFAP, p-Tau (Ser396), Tau5, synaptotagmin-1 (Syt-1), synapsin-1, and brain-derived neurotrophic factor (BDNF) in the hippocampus was detected using Western blot, and the expression of GFAP, IBA1, Aβ1−42 and DCX in the hippocampus was measured via immunofluorescence staining. Results Lateral ventricle administration, but not caudal vein injection of BMSC-exos improved AD-like behaviors in the STZ-injected mouse model, as indicated by the increased number of rearing, increased frequency to the central area, and increased duration and distance traveled in the central area in the OFT, and improved preference index of the novel object in the NOR. Moreover, the hyperactivation of microglia and astrocytes in the hippocampus of the model mice was inhibited after treatment with BMSC-exos via lateral ventricle administration, accompanied by the reduced expression of IL-1β, IL-6, TNF-α, Aβ1-42, and p-Tau and upregulated protein expression of synapse-related proteins and BDNF. Furthermore, the results of the Pearson test showed that the preference index of the novel object in the NOR was positively correlated with the hippocampal expression of BDNF, but negatively correlated with the expression of GFAP, IBA1, and IL-1β. Apart from a positive correlation between the hippocampal expression of BDNF and Syt-1, BDNF abundance was found to be negatively correlated with markers of glial activation and the expression of the inflammatory cytokines, Aβ1-42, and p-Tau, which are characteristic neuropathological features of AD. Conclusions Lateral ventricle administration, but not caudal vein injection of BMSC-exos, can improve AD-like behavioral performance in STZ-injected mice, the mechanism of which might be involved in the regulation of glial activation and its associated neuroinflammation and BDNF-related neuropathological changes in the hippocampus.

Extracellular vesicles in the study of Alzheimer's and Parkinson's diseases: Methodologies applied from cells to biofluids

“…Nevertheless, PP‐based isolation kits as ExoQ (Aulston et al, 2019; Ding et al, 2018; Guo et al, 2020; Park et al, 2020; Wang et al, 2012) and TEI (Lee et al, 2022; Liu et al, 2022; Marzano et al, 2019; Ozansoy et al, 2020; Peng et al, 2022; Tang et al, 2022) are also being employed in some studies, as well as UF kit Exo:pure (Zhdanova et al, 2021). To note, the employment of different methods for EVs isolation from diverse cell lines render in different results.…”

“…The therapeutic potential of EVs has also been addressed using Yang et al, 2020), alleviated brain inflammation by modulating microglia and astrocytes activation (Ding et al, 2018;Liu et al, 2022), and improved spatial learning and memory function (Ding et al, 2018;Liu et al, 2022;Zhdanova et al, 2021). MSCderived EVs were also used as a drug delivery system of neprilysn (an Aβ degrading enzyme), causing improvements spatial memory ability, reducing hippocampus neuronal damage, senile plaques accumulation and alleviating brain inflammation in the AD rat model (Izadpanah et al, 2020).…”

Review on the roles of specific cell-derived exosomes in Alzheimer's disease

“…With well-characterized immunoregulatory neurotrophic and regenerative properties, MSC-derived exosomes were considered as a promising candidate for AD therapy and most widely studied. In mouse models, MSC-derived exosome administration via the lateral ventricle or intravenous injection could reduce Aβ expression and improve AD-like behaviors (Chen et al, 2021 ; Liu et al, 2022 ). Enzymatically active neprilysin, the most important Aβ-degrading enzyme in the brain, is also found in MSC-derived exosomes (Joshi et al, 2015 ).…”

Long non-coding RNAs: Potential therapeutic targets for epilepsy

“…Neuroinflammation is a contributing factor for many neuropsychiatric diseases including Alzheimer’s disease and depression ( Fang et al, 2020 ; Qi et al, 2021 ; Liu S. et al, 2022 ), and increasing evidence have demonstrated its role in the pathogenesis of epilepsy ( Vezzani et al, 2019 ; Kumar et al, 2022 ). Using single-cell cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) techniques, Kumar et al (2022) uncovered a pro-inflammatory microenvironment in the brain lesions of epileptic patients, including an extensive activation of microglia and an infiltration of other pro-inflammatory immune cells, together with a direct interaction between T cells and microglia.…”

“…Using single-cell cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) techniques, Kumar et al (2022) uncovered a pro-inflammatory microenvironment in the brain lesions of epileptic patients, including an extensive activation of microglia and an infiltration of other pro-inflammatory immune cells, together with a direct interaction between T cells and microglia. It is well known that activated microglia and astrocytes could interact with surrounding cells by secreting inflammatory factors, promoting neuroinflammatory responses into a vicious circle ( Ginhoux et al, 2010 ; Tian et al, 2012 ; Santiago et al, 2017 ; Fang et al, 2020 ; Liu S. et al, 2022 ). Through microarray screening, Sun et al (2017) identified that LncRNA GAS5 could regulate the polarization of microglia, acting as an epigenetic regulator.…”