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Exosomes loaded with miR-665 inhibit the progression of osteosarcoma in vivo and in vitro.

OBJECTIVE
Osteosarcoma (OS) is the most common primary malignant bone tumor and has a poor prognosis. Recent research has suggested that miR-665 affects the progression of OS. Moreover, an exosome delivery system presents better targeting effects, higher permeability, and lower immunogenicity than other nano-delivery systems do. The purpose of this study is to explore whether an exosome loaded with the miR-665 delivery system can inhibit OS development.


METHODS
The miR-665 expression was detected through a quantitative real-time polymerase chain reaction assay. Transmission electron microscopy, nano-particle size analysis, and fluorescence microscope were utilized to observe exosomes. Cell growth was estimated by cell counting kit 8 and ethynyl deoxyuridine analyses. Assays of flow cytometry and Terminal-deoxynucleotidyl Transferase Mediated Nick End Labeling were introduced to test apoptosis in vitro or in vivo, respectively. Cell migration and invasion were measured using scratch and transwell assays. Engineered exosomes were prepared using electroporation. H&E staining was employed to observe necrotic cells and the function of heart, liver, spleen, lung and kidney. The expression of proteins was estimated by immunoblot analysis.


RESULTS
This work documented that the expression of miR-665 was down-regulated in OS tissues. Additionally, we proved that the over-expression of miR-665 inhibited OS proliferation. Besides, we found that exosomes loaded with miR-665 had similar tumor-inhibiting effects in vivo and in vitro. Furthermore, we verified that the exosome delivery system exhibited good safety and target efficiency.


CONCLUSION
This work proved that exosomes loaded with miR-665 inhibited the progression of OS in vivo and in vitro in a safe manner.