Secretome of adipose-derived mesenchymal stem cells promotes skeletal muscle regeneration through synergistic action of extracellular vesicle cargo and soluble proteins

Abstract

Background The mechanisms underpinning the regenerative capabilities of mesenchymal stem cells (MSC) were originally thought to reside in their ability to recognise damaged tissue and to differentiate into specific cell types that would replace defective cells. However, recent work has shown that molecules produced by MSCs (secretome), particularly those packaged in extracellular vesicles (EVs), rather than the cells themselves are responsible for tissue repair. Methods Here we have produced a secretome from adipose-derived mesenchymal stem cells (ADSC) that is free of exogenous molecules by incubation within a saline solution. Various in vitro models were used to evaluate the effects of the secretome on cellular processes that promote tissue regeneration. A cardiotoxin-induced skeletal muscle injury model was used to test the regenerative effects of the whole secretome or isolated extracellular vesicle fraction in vivo. This was followed by bioinformatic analysis of the components of the protein and miRNA content of the secretome and finally compared to a secretome generated from a secondary stem cell source. Results Here we have demonstrated that the secretome from adipose-derived mesenchymal stem cells shows robust effects on cellular processes that promote tissue regeneration. Furthermore, we show that the whole ADSC secretome is capable of enhancing the rate of skeletal muscle regeneration following acute damage. We assessed the efficacy of the total secretome compared with the extracellular vesicle fraction on a number of assays that inform on tissue regeneration and demonstrate that both fractions affect different aspects of the process in vitro and in vivo. Our in vitro, in vivo , and bioinformatic results show that factors that promote regeneration are distributed both within extracellular vesicles and the soluble fraction of the secretome. Conclusions Taken together, our study implies that extracellular vesicles and soluble molecules within ADSC secretome act in a synergistic manner to promote muscle generation. Electronic supplementary material The online version of this article (10.1186/s13287-019-1213-1) contains supplementary material, which is available to authorized users.

Adipose‐Derived Biogenic Nanoparticles for Suppression of Inflammation

“…At lower concentrations of Lipo‐NPs (10 7 and 10 8 mL −1 ), IL‐6 remained unchanged (Figure S4, Supporting Information). ADSC‐EVs have previously been shown to contain miR‐let7b,54 which is a known suppressor of TLR4‐induced inflammation 55. It is likely that various miRNAs in both ADSC‐EVs and Lipo‐NPs are involved in suppression of TLR4‐induced inflammation.…”

Biomaterials Functionalized with MSC Secreted Extracellular Vesicles and Soluble Factors for Tissue Regeneration

“…[ 117 ] It is unlikely that the mode of action of MSC trophic factors arises from a single protein or RNA, and it was recently observed that EVs and soluble molecules secreted by MSCs act synergistically to promote muscle regeneration. [ 251 ] Cell culture medium is another important aspect to consider when determining the contents and functional effects of the EVs. Most published studies using fetal bovine serum (FBS) in the culture medium utilize prolonged UC to deplete the FBS of EVs; this technique was also reported to deplete human platelet lysates of EVs.…”

The emerging antioxidant paradigm of mesenchymal stem cell therapy

“…Antioxidant effects of MSC treatments have been associated with enhanced SOD activity or the expression of SODs in models of aging, age‐related erectile dysfunction, chemotherapy‐induced pulmonary fibrosis or gonadotoxicity colitis, pancreatitis, septic lung injury, arthritis, hepatotoxicity and hepatic ischemia reperfusion injury, Alzheimer's disease, and ovarian autografts 33,34,37,38,43,50,62‐70 . MSCs secrete all isoforms of SOD including SOD1 and SOD2, which are archetypically not released extracellularly 33,59,71,72 . Thus, it is difficult to interpret whether enhanced SOD activity and/or SOD expression is due to MSCs or host‐tissue‐derived SOD.…”