Umbilical Cord-Derived Mesenchymal Stem Cell-Derived Exosomal MicroRNAs Suppress Myofibroblast Differentiation by Inhibiting the Transforming Growth Factor-β/SMAD2 Pathway During Wound Healing

Abstract

Excessive scar formation caused by myofibroblast aggregations is of great clinical importance during skin wound healing. Studies have shown that mesenchymal stem cells (MSCs) can promote skin regeneration, but whether MSCs contribute to scar formation remains undefined. We found that umbilical cord-derived MSCs (uMSCs) reduced scar formation and myofibroblast accumulation in a skin-defect mouse model. We found that these functions were mainly dependent on uMSC-derived exosomes (uMSC-Exos) and especially exosomal microRNAs. Through high-throughput RNA sequencing and functional analysis, we demonstrated that a group of uMSC-Exos enriched in specific microRNAs (miR-21, -23a, -125b, and -145) played key roles in suppressing myofibroblast formation by inhibiting the transforming growth factor-b2/SMAD2 pathway. Finally, using the strategy we established to block miRNAs inside the exosomes, we showed that these specific exosomal miRNAs were essential for the myofibroblast-suppressing and anti-scarring functions of uMSCs both in vitro and in vivo. Our study revealed a novel role of exosomal miRNAs in uMSC-mediated therapy, suggesting that the clinical application of uMSC-derived exosomes might represent a strategy to prevent scar formation during wound healing. STEM CELLS TRANSLATIONAL MEDICINE 2016;5:1425-1439 SIGNIFICANCEExosomes have been identified as a new type of major paracrine factor released by umbilical cordderived mesenchymal stem cells (uMSCs). They have been reported to be an important mediator of cell-to-cell communication. However, it is still unclear precisely which molecule or group of molecules carried within MSC-derived exosomes can mediate myofibroblast functions, especially in the process of wound repair. The present study explored the functional roles of uMSC-exosomal microRNAs in the process of myofibroblast formation, which can cause excessive scarring. This is an unreported function of uMSC exosomes. Also, for the first time, the uMSC-exosomal microRNAs were examined by high-throughput sequencing, with a group of specific microRNAs (miR-21, miR-23a, miR-125b, and miR-145) found to play key roles in suppressing myofibroblast formation by inhibiting excess a-smooth muscle actin and collagen deposition associated with activity of the transforming growth factor-b/SMAD2 signaling pathway.

Mesenchymal Stem Cells Reduce Corneal Fibrosis and Inflammation via Extracellular Vesicle-Mediated Delivery of miRNA

“…These results suggest a role for miRNA in the anti‐inflammatory/regenerative function displayed by the CSSC EVs. Such a function is consistent with a number of recent studies that have linked miRNA delivery by EVs to regenerative, antifibrotic, and immune suppressive properties of the vesicles . Some authors have suggested that the small amount of miRNA in EVs makes it more likely that a protein cargo is involved in their biological properties .…”

Amnion Epithelial Cell-Derived Exosomes Restrict Lung Injury and Enhance Endogenous Lung Repair

“…Among the 10 most abundant miRNAs were miR‐27a, which reportedly targets myofibroblast differentiation, and lentiviral delivery of miR‐27a‐3p diminished bleomycin induced lung fibrosis . hAEC Exo also packaged miRNAs that target various aspects of TGFβ signaling including miR‐23a , which inhibits Smad 2 , miR‐203a which inhibits Smad 3 and thereby contributes to the repression of TGFβ mediated epithelial‐mesenchymal transition as well , and miR‐34a which induces lung fibroblast senescence and suppresses fibroblast proliferation . Furthermore, miR‐150 and miR‐194 , both of which are enriched in hAEC Exo, inhibit the activation of hepatic stellate cells and reduce collagen deposition in the setting of liver fibrosis by inhibiting c‐MYB and RAC 1 expression .…”

Mesenchymal stem cells-derived exosomal microRNAs contribute to wound inflammation

“…Under physiological and pathological conditions, these vesicles are formed by inward budding of late endosomes and then released into the extracellular environment upon fusion with the plasma membrane (Basso and Bonetto, 2016). They can shuttle biologically active molecules, such as intact and functional microRNAs (miRNAs), messenger RNAs (mRNAs), and proteins, to targeted recipient cells and reprogram cell behaviors (Zhou et al, 2016;Fang et al, 2016). miRNAs are highly conserved, small (19-24 nt), non-coding RNA molecules that regulate gene expression at the post-transcriptional level by promoting the degradation or blocking of mRNA translation.…”