A Comparative Analysis of Cord Blood Mononuclear Cell- and Plasma-Derived Exosomes in Regulating Apoptosis and Proliferation in U937 Cells.

[INTRODUCTION] Umbilical cord blood-derived exosomes have been considered an excellent resource for regenerative medicine and cancer therapy. These exosomes induce various therapeutic activities through specific cellular responses and molecular signaling mechanisms. In the present study, we investigated the biological effects of exosomes derived from cord blood mononuclear cells (CB-MNCs) and cord blood plasma (CBP) on the U937 cell line, a human acute myeloid leukemia (AML) model.

[METHODS] After cord blood collection, the cord blood units were processed to harvest CBP and CBMNCs. Exosomes were then isolated, purified, and identified by transmission electron microscopy, dynamic light scattering, and Western blotting. Subsequently, U937 cells were cultivated and exposed to the exosomes for 72 hours. Apoptosis and proliferation were assessed by flow cytometry, caspase-3/7 activity assays, and quantitative real-time PCR (qRT-PCR). Moreover, NF-κB and AMPK signaling pathway activity was evaluated by Western blotting.

[RESULTS] We showed that exosomes from CB-MNCs significantly induced apoptosis, triggered caspase- 3/7 activity, and upregulated the expression of pro-apoptotic genes in U937 cells compared with exosomes from CBP. In addition, CB-MNC-derived exosomes efficiently inhibited NF-κB signaling and activated the AMPK pathway.

[DISCUSSION] The observed pro-apoptotic effects and pathway modulation indicate that CB-MNCderived exosomes exert stronger anti-leukemic activity than CBP-derived exosomes. These variations could be attributed to the molecular cargo carried by each exosome population and suggest that the cellular source is a significant factor in exosome-based therapeutics.

[CONCLUSION] These findings suggest that exosomes derived from CB-MNCs could be a potent antileukemic agent and a promising novel therapeutic approach for AML.