MicroRNA-29a inhibits mesenchymal stem cell viability and proliferation by targeting Roundabout 1

Micro-RNAs: A safety net to protect hematopoietic stem cell self-renewal

The hematopoietic system is sustained over time by a small pool of hematopoietic stem cells (HSCs). They reside at the apex of a complex hierarchy composed of cells with progressively more restricted lineage potential, regenerative capacity, and with different proliferation characteristics. Like other somatic stem cells, HSCs are endowed with long-term self-renewal and multipotent differentiation ability, to sustain the high turnover of mature cells such as erythrocytes or granulocytes, and to rapidly respond to acute peripheral stresses including bleeding, infections, or inflammation. Maintenance of both attributes over time, and of the proper balance between these opposite features, is crucial to ensure the homeostasis of the hematopoietic system. Micro-RNAs (miRNAs) are short non-coding RNAs that regulate gene expression posttranscriptionally upon binding to specific mRNA targets. In the past 10 years they have emerged as important players for preserving the HSC pool by acting on several biological mechanisms, such as maintenance of the quiescent state while preserving proliferation ability, prevention of apoptosis, premature differentiation, lineage skewing, excessive expansion, or retention within the BM niche. miRNA-mediated posttranscriptional fine-tuning of all these processes constitutes a safety mechanism to protect HSCs, by complementing the action of transcription factors and of other regulators and avoiding unwanted expansion or aplasia. The current knowledge of miRNAs function in different aspects of HSC biology, including consequences of aberrant miRNA expression, will be reviewed; yet unsolved issues will be discussed. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA in Disease and Development > RNA in Development.

MicroRNA-29b Promotes Subchondral Bone Loss in TMJ Osteoarthritis

Abnormal subchondral bone remodeling plays important roles during osteoarthritis (OA) pathology. Recent studies show that bone marrow mesenchymal stem cells (BMSCs) in osteoarthritic subchondral bones exhibit a prominent pro-osteoclastic effect that contributes to abnormal subchondral bone remodeling; however, the pathologic mechanism remains unclear. In the present study, we used a mouse model with OA-like change in the temporomandibular joint (TMJ) induced by an experimentally unilateral anterior crossbite (UAC) and found that the level of microRNA-29b (miR-29b), but not miR-29a or miR-29c, was markedly lower in BMSCs from subchondral bones of UAC mice as compared with that from the sham control mice. With an intra-articular aptamer delivery system, BMSC-specific overexpression of miR-29b by aptamer-agomiR-29b rescued subchondral bone loss and osteoclast hyperfunction in UAC mice, as demonstrated by a significant increase in bone mineral density, bone volume fraction, trabecular thickness, and the gene expression of osteocalcin and Runx2 but decreased trabecular separation, osteoclast number and osteoclast surface/bone surface, and the gene expression of cathepsin K, Trap, Wnt5a, Rankl, and Rank as compared with those in the UAC mice treated by aptamer-NC (all P < 0.05). In addition, BMSC-specific inhibition of miR-29b by aptamer-antagomiR-29b exacerbated those responses in UAC mice. Notably, although it primarily affected miR-29b levels in the subchondral bone (but not in cartilage and synovium), BMSC-specific overexpression of miR-29b in UAC mice largely rescued OA-like cartilage degradation, including decreased chondrocyte density, cartilage thickness, and the percentage areas of proteoglycans and type II collagen, while BMSC-specific inhibition of miR-29b aggravated these characteristics of cartilage degradation in UAC mice. Moreover, we identified Wnt5a, but not Rankl or Sdf-1, as the direct target of miR-29b. The results of the present study indicate that miR-29b is a key regulator of the pro-osteoclastic effects of BMSCs in TMJ-OA subchondral bones and plays important roles in the TMJ-OA progression.

Targeting the SLIT/ROBO pathway in tumor progression: molecular mechanisms and therapeutic perspectives

The SLITs (SLIT1, SLIT2, and SLIT3) are a family of secreted proteins that mediate positional interactions between cells and their environment during development by signaling through ROBO receptors (ROBO1, ROBO2, ROBO3, and ROBO4). The SLIT/ROBO signaling pathway has been shown to participate in axonal repulsion, axon guidance, and neuronal migration in the nervous system and the formation of the vascular system. However, the role of the SLIT/ROBO pathway has not been thoroughly clarified in tumor development. The SLIT/ROBO pathway can produce both beneficial and detrimental effects in the growth of malignant cells. It has been confirmed that SLIT/ROBO play contradictory roles in tumorigenesis. Here, we discuss the tumor promotion and tumor suppression roles of the SLIT/ROBO pathway in tumor growth, angiogenesis, migration, and the tumor microenvironment. Understanding these roles will help us develop more effective cancer therapies.

Metformin Increases Proliferative Activity and Viability of Multipotent Stromal Stem Cells Isolated from Adipose Tissue Derived from Horses with Equine Metabolic Syndrome

In this study, we investigated the influence of metformin (MF) on proliferation and viability of adipose-derived stromal cells isolated from horses (EqASCs). We determined the effect of metformin on cell metabolism in terms of mitochondrial metabolism and oxidative status. Our purpose was to evaluate the metformin effect on cells derived from healthy horses (EqASCHE) and individuals affected by equine metabolic syndrome (EqASCEMS). The cells were treated with 0.5 μM MF for 72 h. The proliferative activity was evaluated based on the measurement of BrdU incorporation during DNA synthesis, as well as population doubling time rate (PDT) and distribution of EqASCs in the cell cycle. The influence of metformin on EqASC viability was determined in relation to apoptosis profile, mitochondrial membrane potential, oxidative stress markers and BAX/BCL-2 mRNA ratio. Further, we were interested in possibility of metformin affecting the Wnt3a signalling pathway and, thus, we determined mRNA and protein level of WNT3A and β-catenin. Finally, using a two-tailed RT-qPCR method, we investigated the expression of miR-16-5p, miR-21-5p, miR-29a-3p, miR-140-3p and miR-145-5p. Obtained results indicate pro-proliferative and anti-apoptotic effects of metformin on EqASCs. In this study, MF significantly improved proliferation of EqASCs, which manifested in increased synthesis of DNA and lowered PDT value. Additionally, metformin improved metabolism and viability of cells, which correlated with higher mitochondrial membrane potential, reduced apoptosis and increased WNT3A/β-catenin expression. Metformin modulates the miRNA expression differently in EqASCHE and EqASCEMS. Metformin may be used as a preconditioning agent which stimulates proliferative activity and viability of EqASCs.

Expression levels and co‑targets of miRNA‑126‑3p and miRNA‑126‑5p in lung adenocarcinoma tissues: Αn exploration with RT‑qPCR, microarray and bioinformatic analyses

Lung adenocarcinoma (LUAD) is the most common histological subtype of lung cancer. Previous studies have found that many microRNAs (miRNAs), including miRNA-126-3p, may play a critical role in the development of LUAD. However, no study of LUAD has researched the synergistic effects and co-targets of both miRNA-126-3p and miRNA-126-5p. The present study used real-time quantitative polymerase chain reaction (RT-qPCR) to explore the expression values of miRNA-126-3p and miRNA-126-5p in 101 LUAD and 101 normal lung tissues. Ten relevant microarray datasets were screened to further validate the expression levels of miRNA-126-3p and −5p in LUAD. Twelve prediction tools were employed to obtain potential targets of miRNA-126-3p and miRNA-126-5p. The results showed that both miRNA-126-3p and −5p were expressed significantly lower in LUAD. A significant positive correlation was also present between miRNA-126-3p and −5p expression in LUAD. In addition, lower expression of miRNA-126-3p and −5p was indicative of vascular invasion, lymph node metastasis (LNM), and a later tumor/node/metastasis (TNM) stage of LUAD. The authors obtained 167 targets of miRNA-126-3p and 212 targets of miRNA-126-5p; 44 targets were co-targets of both. Eight co-target genes (IGF2BP1, TRPM8, DUSP4, SOX11, PLOD2, LIN28A, LIN28B and SLC7A11) were initially identified as key genes in LUAD. The results of the present study indicated that the co-regulation of miRNA-126-3p and miRNA-126-5p plays a key role in the development of LUAD, which also suggests a fail-proof mode between miRNA-3p and miRNA-126-5p.

miR-218 inhibits gastric tumorigenesis through regulating Bmi-1/Akt signaling pathway

BACKGROUND

Previous studies indicated that miR-218 was deregulated in gastric cancer patients and correlated with tumor invasion and prognosis. The aim of this study was to clarify the effect of miR-218 on the malignant behavior of gastric cancer and its role in regulating Bmi-1/Akt signaling pathway.

MATERIALS AND METHODS

We used miR-218 mimic to transfect gastric cancer cell lines AGS and SGC-7901, and the overexpression efficiency was validated using qRT-PCR assay. MTT assay and Transwell chamber system were performed to detect the effect of miR-218 on cell proliferation, invasion and migration on gastric cancer. Western blot and qRT-PCR assay was used to test the role of miR-218 in regulating Bmi-1/Akt signaling pathway.

RESULTS

As shown in our research, ectopic expression of miR-218 in gastric cancer cells inhibits the proliferation, invasion and migration of gastric cancer cells. In addition, miR-218 re-expression inhibits the expression of Bmi-1 and its downstream target p-Akt⁴⁷³, as well as MMPs and EMT process.

CONCLUSIONS

miR-218 inhibits the proliferation, invasion and migration of gastric cancer cells through modulating EMT process and the expression of MMPs via Bmi-1/Akt signaling pathway.

Conserved temporal ordering of promoter activation implicates common mechanisms governing the immediate early response across cell types and stimuli

The promoters of immediate early genes (IEGs) are rapidly activated in response to an external stimulus. These genes, also known as primary response genes, have been identified in a range of cell types, under diverse extracellular signals and using varying experimental protocols. Whereas genomic dissection on a case-by-case basis has not resulted in a comprehensive catalogue of IEGs, a rigorous meta-analysis of eight genome-wide FANTOM5 CAGE (cap analysis of gene expression) time course datasets reveals successive waves of promoter activation in IEGs, recapitulating known relationships between cell types and stimuli: we obtain a set of 57 (42 protein-coding) candidate IEGs possessing promoters that consistently drive a rapid but transient increase in expression over time. These genes show significant enrichment for known IEGs reported previously, pathways associated with the immediate early response, and include a number of non-coding RNAs with roles in proliferation and differentiation. Surprisingly, we also find strong conservation of the ordering of activation for these genes, such that 77 pairwise promoter activation orderings are conserved. Using the leverage of comprehensive CAGE time series data across cell types, we also document the extensive alternative promoter usage by such genes, which is likely to have been a barrier to their discovery until now. The common activation ordering of the core set of early-responding genes we identify may indicate conserved underlying regulatory mechanisms. By contrast, the considerably larger number of transiently activated genes that are specific to each cell type and stimulus illustrates the breadth of the primary response.

MicroRNA-29a regulates lipopolysaccharide (LPS)-induced inflammatory responses in murine macrophages through the Akt1/ NF-κB pathway

Akt activation in macrophages enhances lipopolysaccharide (LPS)-induced inflammatory responses through upregulation of the NF-κB signal pathway. Akt phosphorylation via microRNA (miR) caused the downregulation of Akt1. Here, we evaluated the role of miR-29a in LPS-triggered inflammatory responses. LPS stimulation of primary macrophages and RAW264.7 cells gradually increased the levels of miR-29a and was dependent on the LPS concentration. Overexpression of miR-29a in macrophages enhanced the expression of proinflammatory cytokines including IL-1β and IL-6, but not TNF-α. Conversely, knockdown of miR-29a diminished cytokine expression. Bioinformatics analyses indicated that Akt1 was a potential target of miR-29a through its interaction with the CDS region of Akt1. The miR-29a also enhanced LPS-induced NF-κB signaling through increased NF-κB transcriptional activity and phosphorylation of p65, and through binding to Akt1. Moreover, Akt1 silencing promoted the LPS-induced expression of IL-1β and IL-6, and upregulated the NF-κB pathway. Taken together, our results suggested that miR-29a participates in the regulation of inflammatory responses in LPS-stimulated macrophages by promoting NF-κB activation through targeting Akt1.