Extracellular Vesicles as Mediators of Communication Between Endothelial Cells and Fibroblasts

During tissue repair, the peak of angiogenesis is characterized by dense, disorganized and poorly perfused vasculature. As healing progresses, many newly formed vessels regress while surrounding fibroblasts undergo robust proliferation and matrix remodeling. Although fibroblast activation often coincides with angiogenesis, the mechanisms of endothelial-fibroblast cross-talk remain poorly defined. One emerging mode of intracellular communication is through extracellular vesicles (EVs), capable of transferring regulatory molecules such as microRNAs (miRNAs) to nearby or distant cells. This study investigated whether EVs secreted by human dermal microvascular endothelial cells (EC-EVs) influence fibroblast behavior. We isolated and characterized EC-EVs and confirmed their uptake by primary dermal fibroblasts. EV treatment enhanced fibroblast migration, proliferation, and collagen production in vitro. In a murine wound model, EC-EVs increased fibroblast density and collagen deposition in granulation tissue, though without accelerating wound closure, suggesting selective modulation of fibroblast function. To uncover molecular mechanisms, small RNA sequencing of EC-EVs identified abundant miRNA cargo, and target prediction using the miRWalk database yielded over 13,000 high confidence gene targets. Bulk RNA sequencing of fibroblasts treated with EC-EVs for 24 and 48 hours revealed differentially expressed genes, with enrichment in angiogenic, chemotactic, and biosynthetic pathways, and downregulation of TGF-β signaling and ECM genes. Integration of predicted miRNA targets with transcriptomic data identified more than 5,000 overlapping genes, implicating PI3K-Akt, MAPK, Wnt, and hypoxia signaling pathways, as well as cytoskeletal and focal adhesion regulation. Together, these findings demonstrate that EC-EVs reprogram fibroblast phenotype through both direct transcriptomic and miRNA-mediated mechanisms, uncovering a novel mode of endothelial-fibroblast communication that may be leveraged to modulate tissue repair.