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1438 uMSC Exosomes Suppress Scar Formation

fluorescent protein-labeled uMSCs into the subcutaneous tissue exosomal microRNAs are novel paracrine factors with important bi-
around wound sites. We found a sharp decline in the quantity of ological functions in stem cell-mediated tissue regeneration. Fur-
uMSCs present at the seventh day. At the 21st day, the implanted thermore, our findings could also lead to important potential
uMSCs had disappeared completely. Therefore, we focused on implications that specific miRNA-enriched uMSC-Exos might
the paracrine functions of uMSCs in the present study. We ob- act as a potential strategy for the intercellular transfer of RNA
served the phenomenon that the coalescent skin of the MSC molecules in vivo. Compared with other transfection strategies,
group was smooth, with no contracture. The expression of we believe that the uMSC-based approach might be more safe
a-SMA was apparently less than that in the PBS and HEK-293T and efficient, because it simulates the endogenous mechanism
groups. Classically, the presence of a-SMA has been considered for cell-cell communications well. Compared with uMSCs, many
tobeamarkerformyofibroblastdifferentiation[33],becausequi- other advantages of uMSC-Exos in clinical applications can also
escent myofibroblasts do not strongly express a-SMA [34]. How- be expected, such as simpler production and storage proce-
ever, the excess differentiation of fibroblasts is an important dures, easier quality control, and a lower risk of side effects.
aspect to its sustained expression. Thus, intervention is needed Thus, we suggest that uMSC-Exo-based therapy could be a can-
in the wound healing process to prevent myofibroblast accumu- didate strategy for not only promoting healing but also improv-
lation, instead of taking remedial measures after scar formation. ing excessive scar formation in the future.
Exosomes have been reported to “horizontally” transfer
functional proteins, mRNAs, and miRNAs to neighboring cells
CONCLUSION
and thus serve as mediators of intercellular communication
[35, 36]. In the present study, we found distinct biological func- The present report sheds light on the specific microRNAs of
tions for exosomal RNAs and proteins. Using proteinase and uMSC-Exos and clarified a new approach for using stem cell ther-
RNase treatments to selectively deplete each major compo- apy to promote wound healing and prevent scar formation.
nent of the exosomal contents, we found that the proteins in Through exosome-mediated intercellular transfer, miR-21, miR-
uMSC-Exos seemed to promote cell proliferation, which might 23a, miR-125b, and miR-145 from uMSC-Exos inhibited TGF-b2,
represent the functions of growth factors or cytokines. How- TGF-bR2, and SMAD2 and thereby suppressed expression of
ever, the RNAs in uMSC-Exos dominantly suppressed myofibro- the target gene a-SMA and reduced collagen I deposition. As
blastformation,whichmighthaveresultedfromthefunctionsof an alternative to cell therapy, administering modified uMSC-Exos
a group of TGF-b/SMAD2-targeting miRNAs. In our data, using with transfected miRNAs to wounds might have a clinically bene-
high-throughput sequencing and functional analysis, we de- ficial anti-scarring effect.
tected several highly abundant specific microRNAs derived from
uMSC-Exos, such as miR-21, miR-23a, miR-125b, and miR-145.
ACKNOWLEDGMENTS
MiR-21 and miR-145 have been previously reported to promote
organ fibrosis [37–40], and most studies have demonstrated We owe great gratitude to all the colleagues in the Department
that miR-21 directly targets to SMAD7 and promotes TGF-b/ of Plastic and Reconstruction. They have been of great help to
SMAD signaling. However, another report also showed that our work. We also thank Zhimin He, M.D., from Fengxian Central
miR-21 targeted TGFBR2 in HaCaT cell lines to inhibit TGF-bsig- Hospital for all of his help with our work. This study was sup-
naling [41], consistent with our present findings. As it is well ported bytheNational NaturalScienceFoundation ofChina(Grants
known that a miRNA could target different mRNAs at the 31471390, 31201110, 81272119, and 81301644) and the Founda-
same time, we therefore suggest that miR-21 might be a tion of Science and Technology Commission of Shanghai Municipal-
double-edged sword in the regulation of TGF-b/SMAD signaling, ity (Grants 13JC1407101 and 13ZR1334800).
and its functions might be alterable according to the state of cells
and their molecular network. Furthermore, the cell models used
AUTHOR CONTRIBUTIONS
in the previous studies were mostly abnormal types of cells, such
as systemic sclerosis skin fibroblasts [37] and tumor cells. We S.F.: conception and design, collection of data, data analysis
therefore also suggest that the functions of microRNAs might and interpretation, manuscript writing; C. Xu: provision of
be diverse among different cells from different organs and tis- study material or patients, data analysis and interpretation,
sues. Thus, our findings on the different roles of these two micro- collection of data; Y. Zhang: provision of study material or pa-
RNAs through uMSC-derived exosomes might improve our tients, manuscript writing; C. Xue: collection and/or assembly
understanding of the complexity of microRNA-mediated molecu- of data; C.Y. and X.Q.: performance of experiments, collection
lar regulations. In addition, we also found that the functions of and/or assembly of data; H.B.: provision of study material or
miR-23a and miR-125b act as inhibitors of the TGF-b/SMAD sig- patients; M.W.: performance of uMSC-related experiments,
naling in modulating myofibroblast differentiation, which is pre- collection and/or assembly of data; K.J. and Y. Zhao: proofread-
viously unreported. We believe that these uMSC-Exo-derived ing and manuscript writing; Y.W.: collection and/or assembly of
microRNAs could be important regulators of TGF-b/SMAD sig- data, data analysis and interpretation, manuscript writing; H.L.:
naling to suppress the differentiation of myofibroblasts during conception and design, data analysis and interpretation, financial
skin wound healing. support, administrative support, final approval of manuscript;
These exosomal miRNAs have been shown to be uMSC spe- X.X.: conception and design, administrative support, final ap-
cific and proved to be functional. Recent studies have indi- proval of manuscript.
cated that miRNAs are incorporated into exosomes and are
more stable than their cellular counterparts. They can resist
DISCLOSURE OF POTENTIAL CONFLICTS OF INTEREST
degradation through protection in vesicles released from cultured
cellsorduringcirculationinthebody[42].Wethereforesuggestthat The authors indicated no potential conflicts of interest.

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