miR29a-Loaded Extracellular Vesicles Derived from Human Mesenchymal Stem Cells Inhibit Fibrotic and Inflammatory Signaling.

Fibrotic processes involve aberrant deposition of extracellular matrix and contribute to ∼ 45% of all deaths in the developed world. Fibrotic remodeling results in stiffening of the local tissue environment, driving a self-amplifying feedback loop of disease progression that involves hyperactivation of both the YAP/TAZ mechanosensing pathway and the NFκB inflammatory pathway. An important component of this fibrotic remodeling is integrin-dependent compaction of the extracellular matrix. Recent work has identified a network of miRNAs that target cytoskeletal, adhesion, and extracellular matrix-related genes in response to high stiffness, which are important in extracellular matrix mechanical homeostasis. Several of these miRNAs also target fibrosis-related genes, indicating some potential to slow or reverse fibrotic processes. In particular, several members of the miR29 family have been identified as potential antifibrotic miRNAs. Mesenchymal stem cells (MSCs) have been implicated for their antifibrotic effects, and their extracellular vesicles (EVs) could provide a means to deliver these miRNAs therapeutically. Here, we loaded and tested human MSC-derived EVs with an antifibrotic miR29a mimic and evaluated their impact on fibrotic and inflammatory signaling pathways in human dermal fibroblasts. We observe that the miR29a mimic reduces activation of YAP in MSCs on stiff substrates but does not significantly alter EV production. Using a miRNA sensor, we show that miR29a mimic-loaded EVs can deliver miR29a and target a microRNA response element for miR29a. These miR29a-loaded EVs also significantly reduce inflammatory signaling and the contractile phenotype of human dermal fibroblasts.