miR-100 suppresses mTOR signaling in hypoxia-induced pulmonary hypertension in rats

MiRNA-100 ameliorates diabetes mellitus-induced erectile dysfunction by modulating autophagy, anti-inflammatory, and antifibrotic effects

BACKGROUND

Diabetes mellitus-induced erectile dysfunction (DMED) has become a common disease in adult men that can seriously reduce the quality of life of patients, and new therapies are urgently needed. miRNA-100 has many targets and can induce autophagy and reduce fibrosis by inhibiting the mTOR pathway and the TGF-β pathway. However, no research has been conducted with miR-100 in the field of DMED, and the specific mechanism of action is still unclear.

OBJECTIVES

To ascertain the effects of miR-100 on corpus cavernosum tissue of DMED rats and vascular endothelial cells in a high glucose environment and to elucidate the relevant mechanisms in autophagy, fibrosis and inflammation to find a new approach for the DMED therapy.

METHODS

Thirty rats were divided into three groups: the control group, the DMED group, and the DMED + miR-100 group. Using intraperitoneal injections of streptozotocin, all rats except the control group were modeled with diabetes mellitus, which was verified using the apomorphine (APO) test. For rats in the DMED + miR-100 group, rno-miR-100-5p agomir (50 nmol/kg, every 2 days, 6 times in total) was injected via the tail vein. After 13 weeks, the erectile function of each rat was assessed using cavernous manometry, and the corpus cavernosum tissue was harvested for subsequent experiments. For cellular experiments, human coronary microartery endothelial cells (HCMEC) were divided into four groups: the control group, the high-glucose (HG, 40 mM) group, the HG + mimic group, and the HG + inhibitor group. The cells were cultured for 6 days and collected for subsequent experiments 2 days after transfection.

RESULTS

Diabetic modeling impaired the erectile function in rats, and miR-100 reversed this effect. By measuring autophagy-related proteins such as mTOR/Raptor/Beclin1/p62/LC3B, we found that miR-100 could suppress the expression of mTOR and induce autophagy. The analysis of the eNOS/NO/cGMP axis function indicated that impaired endothelial function was improved by miR-100. By evaluating the TGF-β1/CTGF/Smad2/3 and NF-κB/TNF-α pathways, we found that miR-100 could lower the level of inflammation and fibrosis, which contributed to the improvement of the erectile function. Cellular experiments can be used as supporting evidence for these findings.

CONCLUSION

MiR-100 can improve the erectile function by inhibiting mTOR and thus inducing autophagy, improving the endothelial function through the eNOS/NO/cGMP axis, and exerting antifibrotic and anti-inflammatory effects, which may provide new ideas and directions for the treatment of DMED.

Modulation of Small RNA Signatures by Astrocytes on Early Neurodegeneration Stages; Implications for Biomarker Discovery

Diagnosis of neurodegenerative disease (NDD) is complex, therefore simpler, less invasive, more accurate biomarkers are needed. small non-coding RNA (sncRNA) dysregulates in NDDs and sncRNA signatures have been explored for the diagnosis of NDDs, however, the performance of previous biomarkers is still better. Astrocyte dysfunction promotes neurodegeneration and thus derived scnRNA signatures could provide a more precise way to identify of changes related to NDD course and pathogenesis, and it could be useful for the dissection of mechanistic insights operating in NDD. Often sncRNA are transported outside the cell by the action of secreted particles such as extracellular vesicles (EV), which protect sncRNA from degradation. Furthermore, EV associated sncRNA can cross the BBB to be found in easier to obtain peripheral samples, EVs also inherit cell-specific surface markers that can be used for the identification of Astrocyte Derived Extracellular Vesicles (ADEVs) in a peripheral sample. By the study of the sncRNA transported in ADEVs it is possible to identify astrocyte specific sncRNA signatures that could show astrocyte dysfunction in a more simpler manner than previous methods. However, sncRNA signatures in ADEV are not a copy of intracellular transcriptome and methodological aspects such as the yield of sncRNA produced in ADEV or the variable amount of ADEV captured after separation protocols must be considered. Here we review the role as signaling molecules of ADEV derived sncRNA dysregulated in conditions associated with risk of neurodegeneration, providing an explanation of why to choose ADEV for the identification of astrocyte-specific transcriptome. Finally, we discuss possible limitations of this approach and the need to improve the detection limits of sncRNA for the use of ADEV derived sncRNA signatures.

The key roles of non-coding RNAs in the pathophysiology of hypertension

Hypertension is a multifactorial condition in which several genetic and environmental elements contribute. Recent investigations have revealed contribution of non-coding region of the transcriptome in this trait. CDKN2B-AS1, AK098656, MEG3, H19, PAXIP1-AS1, TUG1, GAS5, CASC2 and CPS1-IT are among long non-coding RNAs participating in the pathophysiology of hypertension. Several miRNAs have also been found to be implicated in this disorder. miR-296, miR-637, miR-296, miR-637, hsa-miR-361-5p, miR-122-5p, miR-199a-3p, miR-208a-3p, miR-423-5p, miR-223-5p and miR-140-5p are among dysregulated miRNAs in this condition whose application as diagnostic biomarkers for hypertension has been evaluated. Finally, hsa-circ-0005870, hsa_circ_0037911 and hsa_circ_0014243 are examples of dysregulated circular RNAs in hypertensive patients. In the current review, we describe the role of these non-coding RNAs in the pathophysiology of hypertension.

Roles of exosomes and exosome-derived miRNAs in pulmonary fibrosis

Pulmonary fibrosis is a chronic, progressive fibrosing interstitial lung disease of unknown etiology that leads rapidly to death. It is characterized by the replacement of healthy tissue through an altered extracellular matrix and damage to the alveolar structure. New pharmacological treatments and biomarkers are needed for pulmonary fibrosis to ensure better outcomes and earlier diagnosis of patients. Exosomes are nanoscale vesicles released by nearly all cell types that play a central role as mediators of cell-to-cell communication. Moreover, exosomes are emerging as a crucial factor in antigen presentation, immune response, immunomodulation, inflammation, and cellular phenotypic transformation and have also shown promising therapeutic potential in pulmonary fibrosis. This review summarizes current knowledge of exosomes that may promote pulmonary fibrosis and be utilized for diagnostics and prognostics. In addition, the utilization of exosomes and their cargo miRNAs as novel therapeutics and their potential mechanisms are also discussed. This review aims to elucidate the role of exosomes in the pathogenesis of pulmonary fibrosis and paves the way for developing novel therapeutics for pulmonary fibrosis. Further in-depth research and clinical trials on this topic are encouraged in the future.

Mesenchymal Stem Cell-Derived Nanovesicles as a Credible Agent for Therapy of Pulmonary Hypertension

Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) have been evaluated in many studies as promising therapeutic agents for pulmonary hypertension (PH). However, low yields and heterogeneity are a major barrier in the translational utility of EVs for clinical studies. To address these limitations, we fabricated MSCs derived nanovesicles (MSC-NVs) by serial extrusion through filters resulting in MSC-NVs with characteristics similar to conventional EVs but with much higher production yields. Herein, we examined the therapeutic efficacy of MSC-NVs in preclinical models of PH in vitro and in vivo. Intervention with MSC-NVs improved the core pathologies of monocrotaline (MCT) induced PH in rat. Intravenous administration of MSC-NVs resulted in significant uptake within hypertensive lungs, pulmonary artery lesions and especially in pulmonary artery smooth muscle cells (PASMCs). In vitro, MSC-NVs inhibited PDGF-induced proliferation, migration, and phenotype switch of PASMCs. miRNA sequencing analysis of the genetic cargo of MSC-NVs revealed that miR-125b-5p and miR-100-5p are highly abundant, suggesting they might account for the therapeutic effects of MSC-NVs in PH. Depletion of miR-125b-5p and miR-100-5p in MSCs almost completely abolished the beneficial effects of MSC-NVs in protecting PASMCs from PDGF stimulated changes in vitro, and also diminished the protective effects of MSC-NVs in MCT induced PH in vivo. These data highlight the efficacy and advantages of MSC-NVs over MSC-EVs as a promising therapeutic strategy against PH.

Non-Coding RNA Networks in Pulmonary Hypertension

Non-coding RNAs (ncRNAs) are involved in various cellular processes. There are several ncRNA classes, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). The detailed roles of these molecules in pulmonary hypertension (PH) remain unclear. We systematically collected and reviewed reports describing the functions of ncRNAs (miRNAs, lncRNAs, and circRNAs) in PH through database retrieval and manual literature reading. The characteristics of identified articles, especially the experimental methods, were carefully reviewed. Furthermore, regulatory networks were constructed using ncRNAs and their interacting RNAs or genes. These data were extracted from studies on pulmonary arterial smooth muscle cells, pulmonary artery endothelial cells, and pulmonary artery fibroblasts. We included 14 lncRNAs, 1 circRNA, 74 miRNAs, and 110 mRNAs in the constructed networks. Using these networks, herein, we describe the current knowledge on the role of ncRNAs in PH. Moreover, these networks actively provide an improved understanding of the roles of ncRNAs in PH. The results of this study are crucial for the clinical application of ncRNAs.

PKR deficiency alleviates pulmonary hypertension via inducing inflammasome adaptor ASC inactivation

Pulmonary hypertension is a progressive fatal disease that currently has no specific therapeutic approaches. In this study, dsRNA-dependent protein kinase (PKR) was considered a candidate molecule in pulmonary hypertension. We demonstrated that PKR is activated in the endothelium of experimental pulmonary hypertension models. Deletion of PKR or treatment with the PKR activation inhibitor C16 inhibited the development of pulmonary hypertension. To explore the mechanism of PKR in pulmonary hypertension, we detected its downstream signaling and found that PKR knockout represses apoptosis-associated speck-like protein containing CARD (ASC) activation to inhibit high mobility group box 1 (HMGB1) and interleukin-1 beta release. To further explore whether ASC mediates the pro-pulmonary hypertension role of PKR, we used ASC deletion mice and found that ASC deletion inhibits the development of pulmonary hypertension and the release of HMGB1 and interleukin-1 beta. Furthermore, we co-cultured pulmonary arterial endothelial cells (PAECs) and pulmonary arterial smooth muscle cells (PASMCs) and found that endothelial PKR promotes PASMCs proliferation through the release of HMGB1 and interleukin-1 beta. In conclusion, these data indicate that endothelial PKR promotes the excessive proliferation of PASMCs by inducing ASC activation to release HMGB1 and interleukin-1 beta, which lead to the development of pulmonary hypertension. Our study will provide a novel insight that PKR is a potential target in the future treatment of pulmonary hypertension.

mTOR Signaling in Pulmonary Vascular Disease: Pathogenic Role and Therapeutic Target

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease without a cure. The exact pathogenic mechanisms of PAH are complex and poorly understood, yet a number of abnormally expressed genes and regulatory pathways contribute to sustained vasoconstriction and vascular remodeling of the distal pulmonary arteries. Mammalian target of rapamycin (mTOR) is one of the major signaling pathways implicated in regulating cell proliferation, migration, differentiation, and protein synthesis. Here we will describe the canonical mTOR pathway, structural and functional differences between mTOR complexes 1 and 2, as well as the crosstalk with other important signaling cascades in the development of PAH. The pathogenic role of mTOR in pulmonary vascular remodeling and sustained vasoconstriction due to its contribution to proliferation, migration, phenotypic transition, and gene regulation in pulmonary artery smooth muscle and endothelial cells will be discussed. Despite the progress in our elucidation of the etiology and pathogenesis of PAH over the two last decades, there is a lack of effective therapeutic agents to treat PAH patients representing a significant unmet clinical need. In this review, we will explore the possibility and therapeutic potential to use inhibitors of mTOR signaling cascade to treat PAH.

CGRP derived from cardiac fibroblasts is an endogenous suppressor of cardiac fibrosis

AIMS

Aberrant activation of cardiac fibroblasts leads to cardiac fibrosis, and evolving evidences suggest that endogenous bioactive substances derived from cardiac fibroblasts regulate cardiac fibroblasts activation in an autocrine/paracrine manner. Here we first presented evidence that cardiac fibroblasts can synthesize and secrete calcitonin gene-related peptide (CGRP), therefore, this study aimed to investigate the role of cardiac fibroblasts-derived CGRP in cardiac fibroblasts activation and its regulative mechanism.

METHODS AND RESULTS

The abundantly expression of CGRP in rat, mouse, and human myocardium allowed us to explore the cellular origin of CGRP, and found that the cardiac CGRP was mainly derived from cardiac fibroblasts. Activating TRPA1 with a specific agonist allyl isothiocyanate promoted the synthesis and secretion of CGRP, as well as intracellular Ca2+. These effects were reversed by TRPA1-specific antagonist HC030031 and Ca2+ chelator BAPTA-AM. TGF-β1 was applied to induce the activation of cardiac fibroblasts, and found that TGF-β1 can increase the mRNA expression and secretion levels of CGRP in cardiac fibroblasts. Either CGRP8-37 (CGRP receptor antagonist) or α-CGRP small interfering RNA (siRNA) aggravated TGF-β1-induced proliferation, differentiation, collagen production, and instigated inflammation in cardiac fibroblasts. Moreover, TGF-β1-induced NF-κB activation including IκBα phosphorylation and p65 nuclear translocation were also promoted by CGRP8-37 and α-CGRP siRNA. NF-κB inhibitor pyrrolidinedithiocarbamate ammonium (PDTC) reversed the effects of CGRP8-37 on NF-κB activation. The promotive effects of CGRP8-37 on TGF-β1-induced activation of cardiac fibroblasts were all reversed by PDTC. Monocrotaline (MCT) induces pulmonary arterial hypertension, progressively leading to right ventricular fibrosis. This model of cardiac fibrosis was developed here to test the potentially beneficial effects of TRPA1 activation in vivo. The non-toxic TRPA1 agonist Cinnamaldehyde (CA) inhibited MCT-induced elevation in right ventricle systolic pressure, RV/LV + S, and right ventricular collagen accumulation, as well as down-regulation of CGRP. CA increased the synthesis and secretion of CGRP, and inhibited TGF-β1-induced activation in cardiac fibroblasts.

CONCLUSION

Our data suggested an autocrine role for cardiac fibroblasts-derived CGRP in suppressing activation of cardiac fibroblasts through inhibiting NF-κB activation. Increasing autocrine CGRP by activating TRPA1 can ameliorate cardiac fibrosis. These findings support the notion that CGRP derived from cardiac fibroblasts is an endogenous suppressor of cardiac fibrosis.

CAR (CARSKNKDC) Peptide Modified ReNcell-Derived Extracellular Vesicles as a Novel Therapeutic Agent for Targeted Pulmonary Hypertension Therapy

In recent years, mesenchymal stem cells (MSCs)–derived extracellular vesicles (EVs) are emerging as a potential therapeutic agent for pulmonary hypertension (PH). However, the full realization of MSCs-derived EVs therapy has been hampered by the absence of standardization in MSCs culture and the challenges of industrial scale-up. The study was to exploit an alternative replacement for MSCs using currently commercialized stem cell lines for effective targeted PH therapy. ReNcell VM—a human neural stem cell line—has been utilized here as a reliable and easily adoptable source of EVs. We first demonstrated that ReNcell-derived EVs (ReNcell-EVs) pretreatment effectively prevented Su/Hx (SU5416/hypoxia)-induced PH in mice. Then for targeted therapy, we conjugated ReNcell-EVs with CAR (CARSKNKDC) peptide (CAR-EVs)—a peptide identified to specifically target hypertensive pulmonary arteries, by bio-orthogonal chemistry. Intravenous administration of CAR-EVs selectively targeted hypertensive pulmonary artery lesions especially pulmonary artery smooth muscle cells. Moreover, compared with unmodified ReNcell-EVs, CAR-EVs treatment significantly improved therapeutic effect in reversing Su/Hx-induced PH in mice. Mechanistically, ReNcell-EVs inhibited hypoxia-induced proliferation, migration, and phenotype switch of pulmonary artery smooth muscle cells, at least in part, via the delivery of its endogenous highly expressed miRNAs, let-7b-5p, miR-92b-3p, and miR-100-5p. In addition, we also found that ReNcell-EVs inhibited hypoxia-induced cell apoptosis and endothelial-mesenchymal transition in human microvascular endothelial cells. Taken together, our results provide an alternative to MSCs-derived EVs–based PH therapy via using ReNcell as a reliable source of EVs. Particularly, our CAR-conjugated EVs may serve as a novel drug carrier that enhances the specificity and efficiency of drug delivery for effective PH-targeted therapy.

The OxymiR response to oxygen limitation: a comparative microRNA perspective

From squid at the bottom of the ocean to humans at the top of mountains, animals have adapted to diverse oxygen-limited environments. Surviving these challenging conditions requires global metabolic reorganization that is orchestrated, in part, by microRNAs that can rapidly and reversibly target all biological functions. Herein, we review the involvement of microRNAs in natural models of anoxia and hypoxia tolerance, with a focus on the involvement of oxygen-responsive microRNAs (OxymiRs) in coordinating the metabolic rate depression that allows animals to tolerate reduced oxygen levels. We begin by discussing animals that experience acute or chronic periods of oxygen deprivation at the ocean's oxygen minimum zone and go on to consider more elevated environments, up to mountain plateaus over 3500 m above sea level. We highlight the commonalities and differences between OxymiR responses of over 20 diverse animal species, including invertebrates and vertebrates. This is followed by a discussion of the OxymiR adaptations, and maladaptations, present in hypoxic high-altitude environments where animals, including humans, do not enter hypometabolic states in response to hypoxia. Comparing the OxymiR responses of evolutionarily disparate animals from diverse environments allows us to identify species-specific and convergent microRNA responses, such as miR-210 regulation. However, it also sheds light on the lack of a single unified response to oxygen limitation. Characterizing OxymiRs will help us to understand their protective roles and raises the question of whether they can be exploited to alleviate the pathogenesis of ischemic insults and boost recovery. This Review takes a comparative approach to addressing such possibilities.

MicroRNA Nanotherapeutics for Lung Targeting. Insights into Pulmonary Hypertension

In this review, the potential future role of microRNA-based therapies and their specific application in lung diseases is reported with special attention to pulmonary hypertension. Current limitations of these therapies will be pointed out in order to address the challenges that they need to face to reach clinical applications. In this context, the encapsulation of microRNA-based therapies in nanovectors has shown improvements as compared to chemically modified microRNAs toward enhanced stability, efficacy, reduced side effects, and local administration. All these concepts will contextualize in this review the recent achievements and expectations reported for the treatment of pulmonary hypertension.

MicroRNA-100 Enhances Autophagy and Suppresses Migration and Invasion of Renal Cell Carcinoma Cells via Disruption of NOX4-Dependent mTOR Pathway

Renal cell carcinoma (RCC) is the most common kidney malignancy and has a poor prognosis owing to its resistance to chemotherapy. Recently, microRNAs (miRNAs or miRs) have been shown to have a role in cancer metastasis and potential as prognostic biomarkers in cancer. In the present study, we aim to explore the potential role of miR‐100 in RCC by targeting nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) through the mammalian target of rapamycin (mTOR) pathway. Initially, microarray‐based gene expression profiling of RCC was used to identify differentially expressed genes. Next, the expression of miR‐100 and NOX4 was examined in RCC tissues and cell lines. Then, the interaction between miR‐100 and NOX4 was identified using bioinformatics analysis and dual‐luciferase reporter assay. Gain‐of‐function or loss‐of‐function approaches were adopted to manipulate miR‐100 and NOX4 in order to explore the functional roles in RCC. The results revealed the presence of an upregulated NOX4 and a downregulated miR‐100 in both RCC tissues and cell lines. NOX4 was verified as a target of miR‐100 in cells. In addition, overexpression of miR‐100 or NOX4 silencing could increase autophagy while decreasing the expression of mTOR pathway‐related genes and migration and invasion. Conjointly, upregulated miR‐100 can potentially increase the autophagy and inhibit the invasion and migration of RCC cells by targeting NOX4 and inactivating the mTOR pathway, which contributes to an extensive understanding of RCC and may provide novel therapeutic options for this disease.

miR-100-5p-abundant exosomes derived from infrapatellar fat pad MSCs protect articular cartilage and ameliorate gait abnormalities via inhibition of mTOR in osteoarthritis

Osteoarthritis (OA) is the most common disabling joint disease throughout the world and its therapeutic effect is still not satisfactory in clinic nowadays. Recent studies showed that the exosomes derived from several types of mesenchymal stem cells (MSCs) could maintain chondrocyte homeostasis and ameliorate the pathological severity of OA in animal models, indicating that MSCs-derived exosomes could be a novel promising strategy for treating OA. In this study, we investigated the role and underlying mechanisms of infrapatellar fat pad (IPFP) MSCs-derived exosomes (MSC^IPFP-Exos) on OA in vitro and in vivo. Our data revealed that MSC^IPFP could produce amounts of MSC^IPFP-Exos, which exhibited the typical morphological features of exosomes. The MSC^IPFP-Exos ameliorated the OA severity in vivo and inhibited cell apoptosis, enhanced matrix synthesis and reduced the expression of catabolic factor in vitro. Moreover, MSC^IPFP-Exos could significantly enhance autophagy level in chondrocytes partially via mTOR inhibition. Exosomal RNA-seq showed that the level of miR-100-5p that could bind to the 3'-untranslated region (3'UTR) of mTOR was the highest among microRNAs. MSC^IPFP-Exos decreased the luciferase activity of mTOR 3'UTR, while inhibition of miR-100-5p could reverse the MSC^IPFP-Exos-decreased mTOR signaling pathway. Intra-articular injection of antagomir-miR-100-5p dramatically attenuated MSC^IPFP-Exos-mediated protective effect on articular cartilage in vivo. In brief, MSC^IPFP-derived exosomes protect articular cartilage from damage and ameliorate gait abnormality in OA mice by maintaining cartilage homeostasis, the mechanism of which may be related to miR100-5p-regulated inhibition of mTOR-autophagy pathway. As it is relatively feasible to obtain human IPFP from OA patients by arthroscopic operation in clinic, MSC^IPFP-derived exosomes may be a potential therapy for OA in the future.

miR-100 maintains phenotype of tumor-associated macrophages by targeting mTOR to promote tumor metastasis via Stat5a/IL-1ra pathway in mouse breast cancer

Tumor-associated macrophages (TAMs), the main part of immune cells in tumor microenvironment (TME), play a potent role in promoting tumorigenesis through mechanisms such as stimulating angiogenesis, enhancing tumor migration and suppressing antitumor immunity. MicroRNAs (miRNAs) are considered as crucial regulators in multiple biological processes. The relationship between miRNAs and macrophages function has been extensively reported, but the roles that miRNAs play in regulating TAMs phenotype remain unclear. In this study, we screened highly expressed microRNAs in TAMs, and first identified that miR-100 represented a TAMs-high expression pattern and maintained TAMs phenotype by targeting mTOR signaling pathway. Moreover, miR-100 expression level in TAMs was positively related to IL-1ra secretion, a traditional immune-suppressive cytokine, which was determined to promote tumor cells stemness via stimulating Hedgehog pathway. Mechanism study suggested that mTOR/Stat5a pathway was involved in IL-1ra transcriptional regulation process mediated by miR-100. More importantly, tumor metastasis and invasion capacity were significantly decreased in a 4T1 mouse breast cancer model injected intratumorally with miR-100 antagomir, and combination therapy with cisplatin showed much better benefit. In this study, we confirm that highly expressed miR-100 maintains the phenotype of TAMs and promotes tumor metastasis via enhancing IL-1ra secretion. Interfering miR-100 expression of TAMs in mouse breast cancer model could inhibit TAMs pro-tumor function and reduce tumor metastasis, which suggests that miR-100 could serve as a potential therapy target to remodel tumor microenvironment in breast cancer.

MicroRNA-100 shuttled by mesenchymal stem cell-derived exosomes suppresses in vitro angiogenesis through modulating the mTOR/HIF-1α/VEGF signaling axis in breast cancer cells

BACKGROUND

Human mesenchymal stem cells (MSCs) have been shown to be involved in the formation and modulation of tumor stroma and in interacting with tumor cells, partly through their secretome. Exosomes are nano-sized intraluminal multi-vesicular bodies secreted by most types of cells and have been found to mediate intercellular communication through the transfer of genetic information via coding and non-coding RNAs to recipient cells. Since exosomes are considered as protective and enriched sources of shuttle microRNAs (miRNAs), we hypothesized that exosomal transfer of miRNAs from MSCs may affect tumor cell behavior, particularly angiogenesis.

METHODS

Exosomes derived from MSCs were isolated and characterized by scanning electron microscopy analyses, dynamic light scattering measurements, and Western blotting. Fold changes in miR-100 expression levels were calculated in exosomes and their corresponding donor cells by qRT-PCR. The effects of exosomal transfer of miR-100 from MSCs were assessed by qRT-PCR and Western blotting of the mTOR/HIF-1α/VEGF signaling axis in breast cancer cells. The quantification of secreted VEGF protein was determined by enzyme-linked immunosorbent assay. The putative paracrine effects of MSC-derived exosomes on tumor angiogenesis were explored by in vitro angiogenesis assays including endothelial cell proliferation, migration and tube formation assays.

RESULTS

We found that MSC-derived exosomes induce a significant and dose-dependent decrease in the expression and secretion of vascular endothelial growth factor (VEGF) through modulating the mTOR/HIF-1α signaling axis in breast cancer-derived cells. We also found that miR-100 is enriched in MSC-derived exosomes and that its transfer to breast cancer-derived cells is associated with the down-regulation of VEGF in a time-dependent manner. The putative role of exosomal miR-100 transfer in regulating VEGF expression was substantiated by the ability of anti-miR-100 to rescue the inhibitory effects of MSC-derived exosomes on the expression of VEGF in breast cancer-derived cells. In addition, we found that down-regulation of VEGF mediated by MSC-derived exosomes can affect the vascular behavior of endothelial cells in vitro.

CONCLUSIONS

Overall, our findings suggest that exosomal transfer of miR-100 may be a novel mechanism underlying the paracrine effects of MSC-derived exosomes and may provide a means by which these vesicles can modulate vascular responses within the microenvironment of breast cancer cells.

miR-100-5p inhibition induces apoptosis in dormant prostate cancer cells and prevents the emergence of castration-resistant prostate cancer

Carcinoma of the prostate is the most common cancer in men. Treatment of aggressive prostate cancer involves a regiment of radical prostectomy, radiation therapy, chemotherapy and hormonal therapy. Despite significant improvements in the last decade, the treatment of prostate cancer remains unsatisfactory, because a significant fraction of prostate cancers develop resistance to multiple treatments and become incurable. This prompts an urgent need to investigate the molecular mechanisms underlying the evolution of therapy-induced resistance of prostate cancer either in the form of castration-resistant prostate cancer (CRPC) or transdifferentiated neuroendocrine prostate cancer (NEPC). By analyzing micro-RNA expression profiles in a set of patient-derived prostate cancer xenograft tumor lines, we identified miR-100-5p as one of the key molecular components in the initiation and evolution of androgen ablation therapy resistance in prostate cancer. In vitro results showed that miR-100-5p is required for hormone-independent survival and proliferation of prostate cancer cells post androgen ablation. In Silico target predictions revealed that miR-100-5p target genes are involved in key aspects of cancer progression, and are associated with clinical outcome. Our results suggest that mir-100-5p is a possible therapeutic target involved in prostate cancer progression and relapse post androgen ablation therapy.

Knockdown of AMPKα2 Promotes Pulmonary Arterial Smooth Muscle Cells Proliferation via mTOR/Skp2/p27(Kip1) Signaling Pathway

It has been shown that activation of adenosine monophosphate-activated protein kinase (AMPK) suppresses proliferation of a variety of tumor cells as well as nonmalignant cells. In this study, we used post-transcriptional gene silencing with small interfering RNA (siRNA) to specifically examine the effect of AMPK on pulmonary arterial smooth muscle cells (PASMCs) proliferation and to further elucidate its underlying molecular mechanisms. Our results showed that knockdown of AMPKα2 promoted primary cultured PASMCs proliferation; this was accompanied with the elevation of phosphorylation of mammalian target of rapamycin (mTOR) and S-phase kinase-associated protein 2 (Skp2) protein level and reduction of p27(Kip1). Importantly, prior silencing of mTOR with siRNA abolished AMPKα2 knockdown-induced Skp2 upregulation, p27(Kip1) reduction as well as PASMCs proliferation. Furthermore, pre-depletion of Skp2 by siRNA also eliminated p27(Kip1) downregulation and PASMCs proliferation caused by AMPKα2 knockdown. Taken together, our study indicates that AMPKα2 isoform plays an important role in regulation of PASMCs proliferation by modulating mTOR/Skp2/p27(Kip1) axis, and suggests that activation of AMPKα2 might have potential value in the prevention and treatment of pulmonary arterial hypertension.