The miR-21 potential of serving as a biomarker for liver diseases in clinical practice

MiR-21 Is Induced by Hypoxia and Down-Regulates RHOB in Prostate Cancer

Tumour hypoxia is a well-established contributor to prostate cancer progression and is also known to alter the expression of several microRNAs. The over-expression of microRNA-21 (miR-21) has been consistently linked with many cancers, but its role in the hypoxic prostate tumour environment has not been well studied. In this paper, the link between hypoxia and miR-21 in prostate cancer is investigated. A bioinformatic analysis of The Cancer Genome Atlas (TCGA) prostate biopsy datasets shows the up-regulation of miR-21 is significantly associated with prostate cancer and clinical markers of disease progression. This up-regulation of miR-21 expression was shown to be caused by hypoxia in the LNCaP prostate cancer cell line in vitro and in an in vivo prostate tumour xenograft model. A functional enrichment analysis also revealed a significant association of miR-21 and its target genes with processes related to cellular hypoxia. The over-expression of miR-21 increased the migration and colony-forming ability of RWPE-1 normal prostate cells. In vitro and in silico analyses demonstrated that miR-21 down-regulates the tumour suppressor gene Ras Homolog Family Member B (RHOB) in prostate cancer. Further a TCGA analysis illustrated that miR-21 can distinguish between different patient outcomes following therapy. This study presents evidence that hypoxia is a key contributor to the over-expression of miR-21 in prostate tumours, which can subsequently promote prostate cancer progression by suppressing RHOB expression. We propose that miR-21 has good potential as a clinically useful diagnostic and prognostic biomarker of hypoxia and prostate cancer.

ADAR1 improved Treg cell function through the miR-21b/Foxp3 axis and inhibits the progression of acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Th17/Treg equilibrium towards the pro-inflammatory Th17 side contributes greatly to the rejection during allogeneic hematopoietic stem cell transplantation (allo-HSCT). Forkhead box P3 (Foxp3) is important in the pathogenic conversion between Th17 and Treg cells. However, how Foxp3 expression was regulated is largely unknown. Here, we investigated the role of RNA-editing enzyme ADAR1 in Foxp3-mediated Th17/Treg imbalance and progression of acute graft-versus-host disease (aGVHD), a most serious complication in patients received allo-HSCT. Th1, Th17 and Treg cells were respectively isolated from peripheral blood CD4 + T cells of allo-HSCT patients, and we found that proportions of Th1 and Th17 were markedly increased, while Treg proportion was significantly decreased in aGVHD patients post transplantation compared with non-aGVHD patients, accompanied by decreased ADAR1 and increased miR-21b levels. RNA-immunoprecipitation (RIP) combined with gain- and loss-of-function experiments demonstrated that ADAR1 improved Treg cell functions and negatively regulated the production of miR-21b, a Foxp3-targeting miRNA. Inhibition of miR-21b improved Treg functions, and Foxp3 knockdown could eliminate the effect of miR-21b inhibition or ADAR1 overexpression on Treg function. Finally, an aGVHD mouse model was established and Ad-O/E-ADAR1 was injected into aGVHD mice to verify the effect of ADAR1 on aGVHD progression in vivo. The results showed that ADAR1 overexpression decreased Th17 proportion and increased Treg proportion in aGVHD mice and obviously improved tissue necrosis and reticular structure of aGVHD liver and lung in vivo. Collectively, ADAR1 suppresses miR-21b production and improves Foxp3-mediated Treg cell function to inhibit the progression of aGVHD after allo-HSCT.

Role of Exosomes in Chronic Liver Disease Development and Their Potential Clinical Applications

Extracellular vesicles (EVs) are vesicular bodies (40-1000 nm) with double-layer membrane structures released by different cell types into extracellular environments, including apoptosis bodies, microvesicles, and exosomes. Exosomes (30-100 nm) are vesicles enclosed by extracellular membrane and contain effective molecules of secretory cells. They are derived from intracellular multivesicular bodies (MVBs) that fuse with the plasma membrane and release their intracellular vesicles by exocytosis. Research has shown that almost all human cells could secrete exosomes, which have a certain relationship with corresponding diseases. In chronic liver diseases, exosomes release a variety of bioactive components into extracellular spaces, mediating intercellular signal transduction and materials transport. Moreover, exosomes play a role in the diagnosis, treatment, and prognosis of various chronic liver diseases as potential biomarkers and therapeutic targets. Previous studies have found that mesenchymal stem cell-derived exosomes (MSC-ex) could alleviate acute and chronic liver injury and have the advantages of high biocompatibility and low immunogenicity. In this paper, we briefly summarize the role of exosomes in the pathogenesis of different chronic liver diseases and the latest research progresses of MSC-ex as the clinical therapeutic targets.

Exosome-Mediated miR-21 Was Involved in the Promotion of Structural and Functional Recovery Effect Produced by Electroacupuncture in Sciatic Nerve Injury

PURPOSE

Our study is aimed at investigating the mechanism by which electroacupuncture (EA) promoted nerve regeneration by regulating the release of exosomes and exosome-mediated miRNA-21 (miR-21) transmission. Furthermore, the effects of Schwann cells- (SC-) derived exosomes on the overexpression of miR-21 for the treatment of PNI were investigated.

METHODS

A sciatic nerve injury model of rat was constructed, and the expression of miR-21 in serum exosomes and damaged local nerves was detected using RT-qPCR after EA treatment. The exosomes were identified under a transmission electron microscope and using western blotting analysis. Then, the exosome release inhibitor, GW4869, and the miR-21-5p-sponge used for the knockdown of miR-21 were used to clarify the effects of exosomal miR-21 on nerve regeneration promoted by EA. The nerve conduction velocity recovery rate, sciatic nerve function index, and wet weight ratio of gastrocnemius muscle were determined to evaluate sciatic nerve function recovery. SC proliferation and the level of neurotrophic factors were assessed using immunofluorescence staining, and the expression levels of SPRY2 and miR-21 were detected using RT-qPCR analysis. Subsequently, the transmission of exosomal miR-21 from SC to the axon was verified in vitro. Finally, the exosomes derived from the SC infected with the miR-21 overexpression lentivirus were collected and used to treat the rat SNI model to explore the therapeutic role of SC-derived exosomes overexpressing miR-21.

RESULTS

We found that EA inhibited the release of serum exosomal miR-21 in a PNI model of rats during the early stage of PNI, while it promoted its release during later stages. EA enhanced the accumulation of miR-21 in the injured nerve and effectively promoted the recovery of nerve function after PNI. The treatment effect of EA was attenuated when the release of circulating exosomes was inhibited or when miR-21 was downregulated in local injury tissue via the miR-21-5p-sponge. Normal exosomes secreted by SC exhibited the ability to promote the recovery of nerve function, while the overexpression of miR-21 enhanced the effects of the exosomes. In addition, exosomal miR-21 secreted by SC could promote neurite outgrowth in vitro.

CONCLUSION

Our results demonstrated the mechanism of EA on PNI from the perspective of exosome-mediated miR-21 transport and provided a theoretical basis for the use of exosomal miR-21 as a novel strategy for the treatment of PNI.