Abstract
Mesenchymal stem cell (MSC)-derived exosomes mediate tissue regeneration in a variety of diseases including ischemic heart injury, liver fibrosis, and cerebrovascular disease. Despite an increasing number of studies reporting the therapeutic effects of MSC exosomes, the underlying molecular mechanisms and their miRNA complement are poorly characterized. Here we microRNA (miRNA)-profiled MSC exosomes and conducted a network analysis to identify the dominant biological processes and pathways modulated by exosomal miRNAs. At a system level, miRNA-targeted genes were enriched for (cardio)vascular and angiogenesis processes in line with observed cardiovascular regenerative effects. Targeted pathways were related to Wnt signaling, pro-fibrotic signaling via TGF-β and PDGF, proliferation, and apoptosis. When tested, MSC exosomes reduced collagen production by cardiac fibroblasts, protected cardiomyocytes from apoptosis, and increased angiogenesis in HUVECs. The intrinsic beneficial effects were further improved by virus-free enrichment of MSC exosomes with network-informed regenerative miRNAs capable of promoting angiogenesis and cardiomyocyte proliferation. The data presented here help define the miRNA landscape of MSC exosomes, establish their biological functions through network analyses at a system level, and provide a platform for modulating the overall phenotypic effects of exosomes.
Highlights
Exosomes are 50–100 nm lipid vesicles produced by multi-vesicular bodies (MVBs) prior to extracellular secretion[1,2]
After confirming that the exosomes isolated from Mesenchymal stem cell (MSC) were positive for the common exosomal marker CD63 (Supplementary Fig. 1), the size of exosomes were analyzed by nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM)
The difference in size could be due to the fact that exosomes were in their natural, solvated state when measured by NTA while they were dry under TEM conditions
Summary
Exosomes are 50–100 nm lipid vesicles produced by multi-vesicular bodies (MVBs) prior to extracellular secretion[1,2]. MSC exosomes carry trophic factors through their protein, ncRNA, RNA, and lipid cargoes[7] In the heart, they mediate cardiac tissue repair through various mechanisms including modulating the injured tissue environment, inducing angiogenesis, promoting proliferation, and preventing apoptosis[8,9]. Most previous studies have taken a candidate approach and singled out specific miRNAs to assess their therapeutic effects[14], but this approach may not fully capture the various biological effects that miRNAs contained within MSC exosomes induce in recipient cells. The predicted regenerative effects of MSC exosomes were assessed using angiogenesis, cellular proliferation, and fibrosis assays. We determined if the regenerative effects of MSC-derived exosomes could be further improved by enrichment with specific proliferation- and angiogenesis-promoting miRNAs. Our non-viral miRNA loading strategy significantly enriched miRNAs into exosomes to potentiate exosome-mediated phenotypes
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