Improving the Immunomodulatory Potential of MSC-derived Extracellular Vesicles to Attenuate M1 Macrophage Polarization
Background
Over the last years, extracellular vesicles (EVs) from mesenchymal stromal cells (MSCs) have been used clinically to treat inflammatory diseases. EVs transfer the immunomodulatory properties of their parental cells while having advantages regarding cold storage and administration to patients. After intravenous injection, EVs mainly accumulate in macrophage-rich organs, where they have the potential to modulate immune reactions, including the inhibition of pro-inflammatory M1 macrophage polarization. However, the clinical efficacy of MSC-EVs is highly variable. We investigated different factors and strategies to improve their immunomodulatory effect.
Methods
We characterized EVs from human umbilical cord-derived MSCs. Parental cells were either unmodified or activated with pro-inflammatory cytokines. We tested the effects of MSC-EVs on the polarization of human macrophages, which are important regulators of immune reactions. In a second step, we aimed to modulate MSC-EVs by lentiviral transduction of the parental MSCs to achieve targeted EV loading.
Results
MSC-EVs can attenuate the M1 inflammatory phenotype, evidenced by a reduction of secreted inflammatory cytokines by macrophages. This effect can be enhanced by short-term activation of MSCs with pro-inflammatory cytokines. Long-term MSC activation, on the other hand, upregulated the expression of CD317 and reduced EV release. Although the immune modulatory capacity of natural and activated EVs was promising, we observed high donor variability. Selective EV loading with key proteins involved in macrophage polarization might lead to more robust results. We found that tetraspanin-bound eGFP was notably enriched in EVs compared to soluble eGFP. Therefore, we are investigating which members of the tetraspanin family could serve as anchors for the transfer of molecules into EVs.
Conclusion
In summary, MSC-EVs hold the potential as an alternative treatment strategy in an inflammatory disease context. Enhancing their natural capabilities with tetraspanin-mediated EV loading might further increase the robustness of this treatment approach.
Keywords
Mesenchymal stromal/stem cells, macrophage polarization, inflammatory diseases, lentiviral modification, tetraspanins
Authors
Luisa Weisskoeppel1,2, Anton Selich3, Ralf Hass4, Constantin von Kaisenberg5, Axel Schambach1,2,6,
Michael Rothe1,2 (Corresponding author: rothe.michael[at]mh-hannover[dot]de)