Mesenchymal Stem Cell-Derived Exosomes as Drug Delivery Vehicles in Disease Therapy

Abstract

Exosomes are small vesicles containing proteins, nucleic acids, and biological lipids, which are responsible for intercellular communication. Studies have shown that exosomes can be utilized as effective drug delivery vehicles to accurately deliver therapeutic substances to target tissues, enhancing therapeutic effects and reducing side effects. Mesenchymal stem cells (MSCs) are a class of stem cells widely used for tissue engineering, regenerative medicine, and immunotherapy. Exosomes derived from MSCs have special immunomodulatory functions, low immunogenicity, the ability to penetrate tumor tissues, and high yield, which are expected to be engineered into efficient drug delivery systems. Despite the promising promise of MSC-derived exosomes, exploring their optimal preparation methods, drug-loading modalities, and therapeutic potential remains challenging. Therefore, this article reviews the related characteristics, preparation methods, application, and potential risks of MSC-derived exosomes as drug delivery systems in order to find potential therapeutic breakthroughs.

Keywords: disease therapy; drug delivery; exosome; mesenchymal stem cell; nanocarriers.

Figure 1

MSC-derived exosomes as drug delivery vehicles in disease.

Figure 2

Schematic of preparation for MSC-derived exosomes. Classical separation methods include ultracentrifugation, density gradient centrifugation, polymer-based precipitation, and size-exclusion chromatography. Concurrently, technologies for isolation, exemplified by microfluidics, immunology, and covalent chemistry, are in development.

Figure 3

MSC-derived exosomes as drug delivery systems from different tissues can be applied for disease therapy such as inflammatory disease, cancer, immune disease, ischemic disease, and fibrotic disease.

Figure 4

MSC-EVs attenuated renal mitochondrial and mtDNA damage after acute kidney injury (AKI) [122]. (A) MSC-derived exosomes attenuate mitochondrial damage and inflammation by stabilizing mitochondrial DNA. (B) TFAM, PGC-1α, NDUFS8, and ATP5a1 mRNA levels in the mouse kidneys on day 3 after AKI (n = 6; * p < 0.05 vs. Ctrl group; # p < 0.05 vs. I/R group; & p < 0.05 vs. NC EV group). (C) ATP production in the mouse kidneys (n = 6; * p < 0.05 vs. Ctrl group; # p < 0.05 vs. I/R group). (D) Representative TEM images (scale bar = 2 μm) and micrographs of TOM20 and TFAM IHC staining in kidneys of mice (scale bar = 50 μm). (E) Mitochondrial areas and mitochondrial length/width ratio in TEM images (* p < 0.05 vs. Ctrl group; # p < 0.05 vs. I/R group; & p < 0.05 vs. NC EV group). (F) Quantification of TOM20 and TFAM protein expression in the kidneys detected using IHC staining (n = 6; * p < 0.05 vs. Ctrl group; # p < 0.05 vs. I/R group; & p < 0.05 vs. NC EV group). (G) Representative micrographs of TFAM and dsDNA costaining in mouse renal tubules on day 3 after surgery. The mice with I/R injury received intravenous EV injections (∼6.96 × 10¹⁰ particles/mouse) (scale bar = 20 μm). Renal tubular lumen (TL), normal mtDNA nucleoid (white arrowheads), and leaked mtDNA (dsDNA that was not colocalized with TFAM, pink arrowheads) were labeled. (H) The average size of mtDNA nucleoids in the renal tubules detected using IF staining (n = 10; * p < 0.05 vs. Ctrl group; # p < 0.05 vs. I/R group; & p < 0.05 vs. NC EV group). (I) Quantification of the leaked mtDNA intensity (n = 10; * p < 0.05 vs. Ctrl group; & p < 0.05 vs. NC EV group). (J) mtDNA copy number in kidneys of mice (* p < 0.05 vs. Ctrl group; # p < 0.05 vs. I/R group; & p < 0.05 vs. NC EV group).

Figure 5

Schematic representation of postoperative lung metastasis model and drug therapy and S100A4 expression in the lung post-treatment [131]. (A) Schematic illustration of exosome-mediated siRNA delivery to suppress postoperative breast cancer metastasis. (B) Expression of S100A4 in the lung determined by Western blot analysis after treatment with saline, free siS100A4, CBSA/siS100A4, CBSA/siS100A4@Liposome, CBSA/siS100A4@Exosome, and CBSA/siNC@Exosome. (C) S100A4/GAPDH values in the lung tissues of each group; the data represent the mean ± SE (n = 4, * p < 0.05, ** p < 0.01). (D) Immunostaining with anti-S100A4 antibody and Cy3-conjugated secondary antibody (red) showing immunofluorescence images of S100A4 expression in lung tissues from each group. Nuclei were stained with DAPI (blue) and samples were imaged by laser scanning confocal microscopy. Scale bar = 75 μm. (E) Quantitative assessment of S100A4 in treated lung tissue. The data represent the mean ± SE (n = 4, ** p < 0.01, *** p < 0.001).

Figure 6

The miR-125b-5p is enriched in MSC-derived exosomes and delivers to TECs [140]. (A) In ischemic AKI, the injuries of TECs could lead to cell cycle arrest in the G2/M phase and apoptosis. MSC-derived exosomes targeted the injured kidney especially the proximal tubules due to VLA-4 and LFA-1 mediated adhesive interactions. Moreover, miR-125b-5p was enriched in MSC-derived exosomes and exerted the tubular repair effect via suppressing the expression of p53, which not only up-regulated CDK1 and Cyclin B1 to rescue tubular G2/M arrest but modulated Bcl-2 and Bax to inhibit TEC apoptosis. (B) Heat map of the top ten most abundant miRNAs in MSC-exos by miRNA-seq. (C) The relative percentage of miRNAs in total miRNA reads. (D) RT-PCR analysis of the top five most abundant miRNAs in MSC-derived exosomes (n = 5). (E) RT-PCR analysis of the top five miRNAs in MSC-derived-exosome-treated mice renal tissues (n = 5–6). (F) FISH analysis of miR-125b-5p in kidney tissues. Scale bars, 50 µm. (G) Representative images of Cy3-miR-125b-5p mimic-MSC-derived exosomes internalized by HK-2 cells. Scale bars, 50 µm. (H) RT-PCR analysis of miR-125b-5p in HK-2 cells (n = 4–5). Data are presented as mean ± SD, * p < 0.05, ** p < 0.01 vs. sham group or control group, # p < 0.05, ## p < 0.01 vs. I/R or H/R group, one-way ANOVA.