Potential Therapeutic Applications and Developments of Exosomes in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease around the world. Current treatments alleviate the symptoms through the administration of drugs, including dopamine precursors, dopamine metabolism inhibitors, and activated dopamine agonists, but they cannot prevent the ongoing dopaminergic damage. One of the pivotal factors is the poor drug transport efficiency of crossing the blood-brain barrier, while studies reveal that exosomes are endogenous vesicles that are useful for drug delivery and disease diagnosis. As drug carriers, exosomes can not only deliver effective therapeutic drugs but also conquer difficulties such as biocompatibility, blood-brain barrier penetrability, metabolic stability, and target specificity. Exosomes have been successfully loaded with catalase, dopamine, catalase mRNA, and small interfering RNA for PD treatment and shown significant therapeutic effects. As diagnostic indicators (biomarkers), exosomes are more sensitive and reliable. They can reflect the pathological conditions and monitor disease progression. Exosomes from cerebrospinal fluid, plasma, serum, saliva, and urine are valuable biomarkers for PD diagnosis. This review mainly illuminates the association between exosomes and PD, sums up the therapeutic and diagnostic applications of exosomes in PD, and raises some critical remaining questions on the field. It is proposed that future investigations could be dedicated to exploiting a standard procedure to prepare large-scale exosomal carriers with high loading efficiency and new components of exosomes as biomarkers (mRNA; receptors), for better therapeutic and diagnostic options of PD.