Introduction
Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects social communication and behavior. The causes of ASD are not fully understood, but genetic and environmental factors are believed to play a role. There is no cure for ASD, but some treatments can help improve the symptoms and quality of life of people with ASD.
One of the potential treatments for ASD is the transplantation of exosomes, which are tiny vesicles that carry various molecules from one cell to another. Exosomes can be derived from different sources, such as stem cells, which are cells that can develop into different types of cells in the body. Stem cells can be obtained from various tissues and organs, such as fat, umbilical cord, and bone marrow.
Researchers have recently published a paper in the Journal of Nanobiotechnology, where they investigated the effects of exosomes derived from human adipose-derived mesenchymal stem cells (hADSCs) on ASD-like behavior and neurogenesis in mice. Neurogenesis is the process of generating new neurons, which are the cells that transmit information in the brain.
What did they do?
The researchers used a mouse model of ASD, called BTBR T+tf/J (BTBR), which exhibits social deficits, repetitive behaviors, and impaired learning and memory. They compared the BTBR mice with normal mice, called C57BL/6J (B6).
They first sequenced the long non-coding RNAs (lncRNAs) in the exosomes derived from hADSCs and human umbilical cord mesenchymal stem cells (hUCMSCs). lncRNAs are a type of RNA that do not code for proteins, but can regulate gene expression and cellular functions. They found that hADSC exosomes contained more lncRNAs than hUCMSC exosomes, and that some of these lncRNAs were related to neurogenesis.
They then injected the hADSC exosomes into the brain ventricles of the BTBR and B6 mice, and tracked their distribution and uptake by the brain cells. They found that the hADSC exosomes were mainly distributed in the prefrontal cortex (PFC) and the hippocampus, which are brain regions involved in social cognition and memory. They also found that the hADSC exosomes were taken up by the neurons and astrocytes, which are the main types of brain cells.
They then evaluated the effects of the hADSC exosome injection on the behavior and neurogenesis of the BTBR and B6 mice. They used various tests to measure the social interaction, repetitive behavior, learning and memory, anxiety, and depression of the mice. They also used various methods to measure the neurogenesis, neuroinflammation, neuronal apoptosis, and synaptic plasticity of the mice. Synaptic plasticity is the ability of the synapses, which are the connections between neurons, to change their strength and efficiency.
What did they find?
The researchers found that the hADSC exosome injection improved the social interaction, reduced the repetitive behavior, enhanced the learning and memory, and alleviated the anxiety and depression of the BTBR mice. They also found that the hADSC exosome injection increased the neurogenesis, reduced the neuroinflammation, inhibited the neuronal apoptosis, and improved the synaptic plasticity of the BTBR mice.
They further identified a specific lncRNA, called IFNG-AS1, that was highly expressed in the hADSC exosomes and in the PFC of the BTBR mice after the hADSC exosome injection. They found that this lncRNA could bind to a microRNA, called miR-21a-3p, and prevent it from suppressing the expression of a protein, called PI3K, which is involved in the neurogenesis pathway. They confirmed this mechanism by using a synthetic RNA molecule, called antagomir, to block the function of the lncRNA IFNG-AS1, and found that this reversed the effects of the hADSC exosome injection on the BTBR mice.
What does it mean?
The researchers demonstrated that hADSC exosomes have the ability to confer neuroprotection and neuroregeneration in a mouse model of ASD, by delivering a specific lncRNA that regulates the neurogenesis pathway. They suggested that this lncRNA acts as a molecular sponge, which means that it can absorb and neutralize the microRNAs that inhibit the neurogenesis. They proposed that this mechanism could be a novel therapeutic strategy for ASD and other neurodevelopmental disorders.
The researchers acknowledged some limitations of their study, such as the small sample size, the short-term follow-up, and the lack of human data. They also noted that the safety and efficacy of hADSC exosome transplantation in humans need to be further evaluated in clinical trials.
Conclusion
This study showed that exosomes derived from human fat cells can help treat autism in mice, by delivering a long non-coding RNA that promotes neurogenesis. This finding could pave the way for a new cellular-free therapy for autism and other brain disorders.
Faq
What are exosomes?
Exosomes are tiny vesicles, or sacs, that are released by cells and carry various molecules, such as proteins, RNAs, and lipids. Exosomes can act as messengers between cells, transferring information and influencing their functions. Exosomes can be derived from different sources, such as stem cells, which are cells that can develop into different types of cells in the body.
What are long non-coding RNAs (lncRNAs)?
Long non-coding RNAs (lncRNAs) are a type of RNA that do not code for proteins, but can regulate gene expression and cellular functions. lncRNAs can interact with other molecules, such as DNA, proteins, and microRNAs, and modulate their activities. lncRNAs are involved in various biological processes, such as development, differentiation, and disease.
What are the advantages of using exosomes derived from human adipose-derived mesenchymal stem cells (hADSCs) for ASD treatment?
Exosomes derived from human adipose-derived mesenchymal stem cells (hADSCs) have several advantages over other sources of exosomes or stem cells for ASD treatment. First, hADSCs are easy to obtain from fat tissue, which is abundant and accessible in humans. Second, hADSCs have low immunogenicity, which means they are less likely to cause immune reactions or rejection when transplanted into another individual. Third, hADSCs have high plasticity, which means they can differentiate into various types of cells, such as neurons and astrocytes, which are the main types of brain cells. Fourth, hADSCs have high paracrine activity, which means they can secrete various factors, such as exosomes, that can influence the surrounding cells and tissues. Fifth, hADSC exosomes contain more lncRNAs than other sources of exosomes, and some of these lncRNAs are related to neurogenesis, which is the process of generating new neurons.
How did the researchers inject the hADSC exosomes into the mouse brain?
The researchers injected the hADSC exosomes into the brain ventricles of the mice, which are cavities filled with cerebrospinal fluid (CSF) that communicate with the brain and spinal cord. The CSF acts as a cushion and a nutrient source for the brain and spinal cord, and also transports various substances, such as hormones, antibodies, and exosomes. By injecting the hADSC exosomes into the brain ventricles, the researchers ensured that the exosomes could reach the brain regions and cells that are involved in ASD, such as the prefrontal cortex and the hippocampus.
How did the researchers track the distribution and uptake of the hADSC exosomes in the mouse brain?
The researchers labeled the hADSC exosomes with a fluorescent dye, called PKH26, which emits red light when excited by a laser. The researchers then used a technique called in vivo imaging, which allows them to visualize the fluorescence of the exosomes in the living mice. The researchers also used a technique called immunofluorescence, which allows them to detect the presence of specific proteins or markers on the cells or tissues. The researchers used antibodies that bind to specific markers of neurons and astrocytes, such as NeuN and GFAP, and labeled them with fluorescent dyes that emit green or blue light. The researchers then used a microscope to observe the co-localization of the red, green, and blue fluorescence, which indicates the uptake of the exosomes by the neurons and astrocytes.
How did the researchers measure the behavior and neurogenesis of the mice?
The researchers used various tests to measure the behavior and neurogenesis of the mice. For the behavior, the researchers used the following tests:
- The three-chamber test, which measures the social interaction of the mice by exposing them to an unfamiliar mouse or an object in a chamber.
- The marble burying test, which measures the repetitive behavior of the mice by counting the number of marbles that they bury in their bedding.
- The Morris water maze test, which measures the learning and memory of the mice by testing their ability to find a hidden platform in a pool of water.
- The open field test, which measures the anxiety of the mice by recording their activity and exploration in an open arena.
- The tail suspension test, which measures the depression of the mice by recording their immobility when suspended by their tail.
For the neurogenesis, the researchers used the following methods:
- The bromodeoxyuridine (BrdU) labeling method, which measures the proliferation of new cells by injecting a chemical that incorporates into the DNA of dividing cells and staining them with an antibody.
- The immunohistochemistry method, which measures the differentiation of new cells by staining them with antibodies that recognize specific markers of neurons and astrocytes, such as DCX and GFAP.
- The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method, which measures the apoptosis of cells by staining them with a chemical that binds to the DNA fragments of dying cells.
- The western blot method, which measures the expression of proteins by separating them by size and detecting them with antibodies.
- The synaptic vesicle protein 2 (SV2) staining method, which measures the synaptic plasticity by staining the synapses with an antibody that recognizes a protein involved in neurotransmitter release.
What is the role of lncRNA IFNG-AS1 in neurogenesis and ASD?
lncRNA IFNG-AS1 is a lncRNA that is highly expressed in the hADSC exosomes and in the prefrontal cortex of the mice after the hADSC exosome injection. lncRNA IFNG-AS1 can act as a molecular sponge, which means that it can bind to and neutralize a microRNA, called miR-21a-3p, that inhibits the expression of a protein, called PI3K, which is involved in the neurogenesis pathway. By blocking the function of miR-21a-3p, lncRNA IFNG-AS1 can increase the expression of PI3K, which can activate another protein, called AKT, which can promote the survival and differentiation of new neurons. lncRNA IFNG-AS1 can also regulate the expression of other genes that are related to neurogenesis and ASD, such as BDNF, GSK3B, and PTEN. By enhancing the neurogenesis and synaptic plasticity, lncRNA IFNG-AS1 can improve the social interaction, learning and memory, and mood of the mice with ASD-like behavior.
How did the researchers confirm the mechanism of lncRNA IFNG-AS1?
The researchers confirmed the mechanism of lncRNA IFNG-AS1 by using a synthetic RNA molecule, called antagomir, to block the function of lncRNA IFNG-AS1. Antagomir is a modified RNA molecule that can bind to and degrade a specific RNA molecule, such as lncRNA IFNG-AS1. The researchers injected the antagomir into the brain ventricles of the mice, and found that this reversed the effects of the hADSC exosome injection on the behavior and neurogenesis of the mice. This indicates that lncRNA IFNG-AS1 is essential for the therapeutic effects of the hADSC exosomes.
Source:
https://jnanobiotechnology.biomedcentral.com/articles/10.1186/s12951-024-02338-2