Study of multipotent mesenchymal stromal cells as a cellular delivery system for antitumor drugs and their remote control activation

Summary

The effectiveness of a number of cytotoxic drugs directly depends on the concentration of the active substance in the tumor zone. However, an increase in the administered doses also leads to an increase in side effects in relation to healthy tissues. The solution can be a novel dosage form that would accumulate high local concentrations of cytostatic drugs in the tumor area without affecting the surrounding healthy tissue. To create such a drug delivery system, it is possible to utilize multipotent mesenchymal stromal cells (MMSCs) modified with hybrid polyelectrolyte microcapsules. MMSCs due to the effect of pathotropism are able to ensure active delivery of biologically active substances to the tumor site, while microcapsules have a high loading capacity and can protect carrier cells from the effects of the encapsulated drug. In this work, the microcapsules were additionally modified with gold nanoparticles, which makes them sensitive to infrared radiation and allows to control the release of the drug. In this study, vincristine was used as a model drug with a dose-dependent effect.

Objects and methods

Capsules were synthesized using Layer-by-Layer technique (Polyarginine / Dextran sulfate) and sol-gel synthesis (Tetraethyl orthosilicate). The loading capacity of micrometer (1-2 microns) and submicron (500-600 nm) capsules was evaluated. We demonstrated that without an infrared laser irradiation of the capsules, a release of vincristine was less than 10%. Therefore, these capsules are non-toxic to carrier cells which was confirmed by cytotoxicological experiments. The effect of capsules on spontaneous and directed migration of MMSCs was studied and it was shown that at the ratio of cells to capsules of 1 to 10, there is no significant decrease in the migration potential of carrier cells. Evaluation of spontaneous migration was carried out using scratch wound assay and a monitoring system for living cells Cell-IQ. The effect of vincristine-loaded capsules on directed migration was evaluated using slides for chemotaxis. The invasive potential of MMSC was determined using a Transwell assay. In experiments on directed cell migration, the SDF-1 cytokine, which is expressed by a number of tumors and is considered crucial for the regulation of MMSC migration, was used.

Results

The effectiveness of this delivery system was also investigated on the model of a tumoroid in a collagen gel. The tumor spheroid consisted of melanoma cells expressing SDF-1. It was demonstrated that MMSCs modified with capsules were able to not only migrate towards the tumor site, but also penetrate the tumoroid to a depth of up to 50 μm. Comparison of the efficacy of pure vincristine, vincristine-loaded capsules, and MMSCs modified with vincristine-loaded capsules, showed a significant increase in efficiency in the case of MMSC. It was also demonstrated that the exposure of the capsules to infrared radiation increases the effect by 2-4 times due to the simultaneous release of the vincristine from the capsules.

Conclusions

Thus, we developed a drug delivery system that was able to provide high local concentrations of the active substance in the tumor area and demonstrated several times greater in vitro efficacy compared to the free drug.

Keywords

Micro- and nanocapsules, targeted delivery antitumor drugs, internalization, mesenchymal stromal cells, migration, pharmacokinetics, synthesis, cultivation, carrier cells.