Mesenchymal stem cells (MSCs) are multi-functional stem cells that are present in multiple human tissues and can be found in the spinal cord, umbilical cord blood, umbilical cord tissue, placenta tissue, adipose tissue, etc..
With low immunogenicity, multi-directional diferentiation ability, in particular homing ability, MSCs have signifcant research potential in cardiovascular diseases, nervous diseases, and hematopoietic diseases.
The drug delivery system based on MSCs has become one of the most attractive therapeutic methods because of its characteristics. However, cells as drug carriers still face many problems such as uncertain diferentiation accidents, cell embolism, infection, production, and storage. As the secretion of MSCs, the exosomes inherit the relative advantages of MSCs and overcome the problems of MSCs as drug carriers.
The exosomes are secreted by mesenchymal stem cells (MSC-EXOs), most of which are cup-shaped or round with a diameter of 30–100 nm and a density of 1.13–1.19 g/ml. The exosomes contain lipid, protein, and RNA. The lipid bilayer maintains the integrity of exosomes and stabilizes biological activities. Protein modification on the surface enhances the recognition and targeting ability of the exosomes. Abundant RNA in the capsule improves the imaginative potential to regulate the transcription and translation of receptor cells.
With diferent sources of MSC, the characteristics of the exosomes are diferent. MSC-EXOs have many unique characteristics, such as small size, low immunogenicity, long-circulating half-life, good penetration, and good biocompatibility. It is one of the best choices for researchers to fnd drug carriers in vivo.
In current studies, researchers use MSC-EXOs as a carrier to deliver RNA, protein, and molecular drugs to specific parts of the body to achieve targeted therapy. However, problems such as carrier separation and purifcation, preservation and transportation, drug loading, and targeting still exist.
In this study, are first summarized the production and drug loading methods of MSC-EXOs, and the modifcation of MSC-EXOs for targeted drug delivery. Secondly, the delivery of RNA, small molecular drugs, and proteins by MSC-EXOs to treat diferent kinds of diseases are discussed. Furthermore, were also provided perspectives for enhancing the drug loading efficacy of MSC-EXOs.