Human umbilical cord blood-mesenchymal stem cell derived exosomes as an efficient nanocarrier for Docetaxel and miR-125a: Formulation optimization and anti-metastatic behaviour

Exosomes, as a nanocarrier for the co-delivery of biologicals and small anticancer molecules is yet in its infancy. Herein, we investigated hUCBMSC derived exosomes as a biogenic nanocarrier for the co-delivery of tumor suppressor miR-125a and microtubule destabilizing Docetaxel (DTX) to target the proliferative and migratory aggressiveness of the murine TNBC 4T1 cells. In this study, hUCBMSCs from the human umbilical cord blood cells (hUCB) were successfully transfected with miR-125a. Thereafter, DTX was encapsulated into both non-transfected and transfected exosomes by optimized mild sonication-incubation technique. The anticancer efficiency of hUCBMSC Exo-DTX and miR-125a Exo-DTX was compared by MTT and morphometric assay. The prominent anti-metastatic behaviour of the latter was confirmed by in-vitro wound healing and transwell invasion assay. Further, the synergistic effect of miR-125a and DTX was confirmed by F-actin and nuclear degradation by confocal and FESEM assay. hUCBMSC exosomes exhibited DTX payload of 8.86 ± 1.97 ng DTX/ μg exosomes and miRNA retention capacity equivalent to 12.31 ± 5.73 %. The co-loaded formulation (miR-125a Exo-DTX) exhibited IC50 at 192.8 ng/ml in 4T1 cells, which is almost 2.36 folds' lower than the free DTX IC50 (472.8 ng/ml). Additionally, miR-125a Exo-DTX treatment caused wound broadening upto 6.14±0.38 % while treatment with free DTX and miR-125a exosomes alone caused 18.71±4.5 % and 77.36±10.4 % of wound closure respectively in 36 h. miR-125a Exo-DTX treatment further exhibited significantly reduced invasiveness of 4T1 cells (by 3.5 ± 1.8 %) along with prominent cytoskeletal degradation and nuclear deformation as compared to the miR-125a exosomes treated group. The miR-125a expressing DTX loaded exosomal formulation clearly demonstrated the synergistic apoptotic and anti-migratory efficiency of the miR-125a Exo-DTX. The synergistic anticancer and anti-metastatic effect of miR-125a Exo-DTX was observed due to presence of both DTX and miR-125a as the cargo of hUCBMSC derived exosomes.