Neurodegenerative diseases (NDs) are illnesses that affect the central nervous system, resulting in neuronal death and protein misfolding or accumulation (Jan et al., 2017). ND, in addition to being a type of refractory sickness, have had a global influence on medicine, society, and the economy. Despite substantial efforts to study the pathogenic origins and create treatment ways to manage NDs, only a handful have proven effective (Ashique et al., 2024a). Neurodegeneration is characterized as gradual deterioration in brain tissues that leads to irreversible loss of neurones, affecting memory, movement, including cognitive decline in such individuals (Liu et al., 2017). The precise origins of NDs remain unknown, and no known effective therapies exist for these disorders. Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS), stroke, and spinal cord injury (SCI) are among the most common kinds of neurodegenerative disorders. AD, the most prevalent kind of dementia, affects more than 50 million people aged 65 and over (Nowell et al., 2023). The prevalence of MS has risen globally in recent decades. Europe has the greatest frequency of MS (Barrie et al., 2024). Parkinson's disease (PD) affects around 1–2 in 1000 people at any given moment. Among the most important concerns influencing the success of medication in curing such diseases is the limited entrance of foreign particles enter the brain's central nervous system (CNS) (Warren, 2018). The blood-brain barrier (BBB) is primarily responsible for restricted medication delivery to the brain. The therapeutic effects of traditional pharmaceuticals, such as small molecules, bigger molecules, therapeutic peptides, or inhibitors, are frequently poor in treating neurological illnesses due to obstacles in transporting them over the BBB (Kreuter, 2004).

Extracellular vesicles (EVs) are a significant component in neurodegenerative diseases, acting as biomarkers, treatments, or disease spreaders. They are released into the extracellular environment by all cell types in both healthy and diseased conditions. Three main types of EVs are microvesicles, exosomes, and apoptotic bodies. Apoptotic bodies, with a diameter of 1000–5000 nm, are expelled from cells going through apoptosis. Microvesicles, with a diameter of 50–1000 nm, are involved in synaptic activation, neuronal growth, and nerve regeneration. Exosomes, ranging in size from 30 to 150 nm, are produced from apoptotic bodies and transport biomolecules that can be absorbed by target cells.

Exosomes are small endosomal-derived membranes small vessels which have received during the last decade. Exosomes were discovered in extracellular space as early as the late 1980s (Johnstone et al., 1987). Exosomes, which are small extracellular vesicles, are generated by a variety of cell types. They are spherical and tiny, with a double-layered phospholipid membrane that contains lipids, proteins, and nucleic acids (Chen et al., 2022a). Exosomes transport physiologically active substances like as proteins, microRNA, mRNA, DNA, and other compounds. Compounds contained within exosomes can also be transferred on their surfaces. Because of their tiny size, exosomes are potential delivery methods in personalised medicine (Bunggulawa et al., 2018). Liposomes, the first known artificial vesicles identified as lipid-based drug delivery carriers, are typically composed of synthetic lipids and have the potential to transport a payload (Mukherjee et al., 2022). Exosomes are more stable in bodily fluids than liposomes, while having identical shapes and properties. In neurodegenerative diseases, malfunctioning mitochondria and other organelles can be transported via exosomes made from apoptotic bodies, affecting the destination cell's function (Fig. 1). The therapeutic function of exosomes will be the main topic of this study, as new research indicates that exosomes produced from stem cells may be used to treat neurodegenerative illnesses. Conversely, exosomes produced from sick cells, such as damaged neurons, can spread disease pathology pathogenicly.