Application of In Vivo Animal Imaging System in the Study of the Relationship between Extracellular Vesicles and Neurodegenerative Diseases

Professor Zhao Yanxin and Professor Liu Xueyuan's research team from the Department of Neurology, Shanghai 10th People's Hospital Affiliated to Tongji University School of Medicine have made new progress in the research on the relationship between extracellular vesicles and neurodegenerative diseases. This study provides new insights into the excitatory inhibition imbalance that occurs in Alzheimer's disease from the perspective of small extracellular vesicles. The relevant research results have been published in the Journal of Nanobiotechnology (IF: 10.435, JCR Q2).

Extracellular Vesicles(EVs)’s Role in Neuronal Cell Growth and Apoptosis

Extracellular vesicles (EVs) are small vesicles released by cells into the extracellular environment. EVs are composed of lipid bilayer membranes that encapsulate small organelle-free cytoplasm.

According to their size, extracellular vesicles (EVs) are usually divided into three types: small sEVs (50-150 nm), large EVs (100-1000 nm), and apoptotic bodies (5 μm). Among them, sEVs typically become key mediators of communication between central nervous system (CNS) cells through the blood-brain barrier (BBB). There is evidence that microRNAs (miRNAs) in sEVs are involved in numerous cellular and biological processes, such as neuronal cell growth and apoptosis.

At present, the hypothesis of E/I (excitation/inhibition) imbalance is conceptualized as an imbalance between glutamate and aminobutyric acid (GABA) synaptic inputs. E/I imbalance is considered the foundation of brain dysfunction in neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), schizophrenia, and other neurological diseases. Excitotoxicity of glutamate and dysfunction of GABAergic neurons seem to be key causes of neuronal cell death in AD. However, the mechanism behind the impact of E/I imbalance on AD is still unclear.

To further elucidate this mechanism, Professor Zhao Yanxin and Professor Liu Xueyuan's team treated primary cultured neurons with glutamate/GABA/PBS in this study and isolated sEV. Then, add sEVs from different sources to Aβ(β Amyloid protein) treated neurons and injected them into AD model mice. Afterward, After that, aβ treated mice and neurons were evaluated. The sEVs released by GABA-treated neurons reduced Aβ induced damage, while glutamate-treated neurons release sEVs that exacerbate Aβ toxicity. In addition, this study compared the miRNA composition of sEV isolated from neurons treated with glutamate/GABA/PBS through miRNA sequencing. This study further indicates that changes in miR-132 in sEV accelerate biochemical changes that characterize pathology.

Figure 2 | Diagram of experimental scheme

After isolating the primary neurons, the primary cultured neurons were treated with glutamate/GABA/PBS and sEV was isolated. Add sEVs from different sources to Aβ processed neurons, and injected into AD model mice and subject to MWM testing.

Use Aniview100 IVIS to Study the Relationship between EVs and Neurodegenerative Diseases

In the article, the distribution of sEVs transmitted by the system in mice wasevaluated using Biolight Biotechnology’s AniView100 multi-modal in vivo animal imaging system.

In this experiment, the near-infrared dye DiR was used for labeling, and a negative control experiment was conducted (injecting only DiR and not sEV). DiR labeled sEV was injected into the tail vein of APP/PS1 mice, and the Aniview100 in vivo animal imaging system was used to capture images of the mice 24 hours after injection and evaluate their distribution. Fluorescence was detected in the brain and important organs of mice with sEV labeled with DiR. Subsequently, the mice were sacrificed, and their organs were removed and imaged, to identify the organ from which the fluorescence signal originated and minimize signal interference. In addition, to eliminate the possibility of free dyes interfering with the experimental results, mice were treated with free DiR without sEV before organ collection. The experimental results showed that the brain, heart, liver, lungs, spleen, intestine, and kidneys all showed varying degrees of fluorescence.

Figure 3 | In vivo and in vitro distribution of sEV

24 hours after injection of DiR labeled sEV, A-C live mice were imaged using a live imaging system.

a) Mouse back imaging

b) Mouse ventral imaging

c) Collect designated organs and use a live imaging system for imaging

This study demonstrated that the function of sEV can be regulated by the balance state of neurotransmitters, and the Aβ toxicity has different effects. And this study provides new insights into the E/I imbalance that occurs in AD from the perspective of sEV and suggests that biological modification of sEV through the GABAergic system may be a therapeutic approach to prevent or alleviate the pathogenesis of AD.

Biolight Biotechnology’s in vivo imaging system (IVIS)

Our AniView multi-model in vivo animal imaging system enables scientists to monitor the phenotype of lab animal without dissection, which significantly benefits the improvement of animal welfare and promote scientific research by reducing the use of the experimental animal.

Advantages of BLT’s in vivo imaging system (IVIS)

• Ultra-high sensitivity

• Ultra-low fluorescent background

• User-friendly operating software

• Smart design solutions

• More expansion modules

>> Learn More

Reference:

https://doi.org/10.1186/s12951-021-01070-5