Isolating clinical-grade umbilical cord blood‐derived small extracellular vesicles

Extracellular vesicles (EV) are a promising therapeutic tool in regenerative medicine. These particles were shown to accelerate wound healing, through delivery of regenerative mediators, such as microRNAs. Researchers at Exogenus Therapeutics describe an optimized and upscalable process for the isolation of EV smaller than 200 nm (sEV), secreted by umbilical cord blood mononuclear cells (UCB‐MNC) under ischemic conditions and propose quality control thresholds for the isolated vesicles, based on the thorough characterization of their protein, lipid and RNA content. Ultrafiltration and size exclusion chromatography (UF/SEC) optimized methodology proved superior to traditional ultracentrifugation (UC), regarding production time, standardization, scalability, and vesicle yield. Using UF/SEC, the researchers were able to recover approximately 400 times more sEV per mL of media than with UC, and upscaling this process further increases EV yield by about 3‐fold. UF/SEC‐isolated sEV display many of the sEV/exosomes classical markers and are enriched in molecules with anti‐inflammatory and regenerative capacity, such as hemopexin and miR‐150. Accordingly, treatment with sEV promotes angiogenesis and extracellular matrix remodeling, in vitro. In vivo, UCB‐MNC‐sEV significantly accelerate skin regeneration in a mouse model of delayed wound healing. The proposed isolation protocol constitutes a significant improvement compared to UC, the gold‐standard in the field. Isolated sEV maintain their regenerative properties, whereas downstream contaminants are minimized. The use of UF/SEC allows for the standardization and upscalability required for mass production of sEV to be used in a clinical setting.

Comparison of ultracentrifugation (UC) and combined ultrafiltration and size exclusion chromatography (UF/SEC) for the isolation of small extracellular vesicles (sEV)

Workflow for (A) UC and (B) UF/SEC. C, Particle and protein concentration as a function of UF/SEC fraction. D, sEV yield per mL of conditioned media (CM), using UC or UF/SEC (n = 5). E, Workflow for upscaled UF/SEC, based in the pooling from several UCB donors. F, FPLC chromatogram comparing smaller and larger SEC columns. G, sEV yield per mL of conditioned media (CM), using smaller‐ or larger‐scale UF/SEC (n ≥ 7). All values are mean ± SEM. **P < .01; ****P < .0001

Cardoso RMS, Rodrigues SC, Gomes CF, Duarte FV, Romao M, Leal EC, Freire PC, Neves R, Simões-Correia J. (2021) Development of an optimized and scalable method for isolation of umbilical cord blood-derived small extracellular vesicles for future clinical use. Stem Cells Transl Med [Epub ahead of prin]. [article]

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