MicroRNAs Regulate Key Effector Pathways of Senescence

The role of exosomes and their enhancement strategies in the treatment of osteoarthritis

With the increasingly prominent problem of population aging, osteoarthritis (OA), which is closely related to aging, has become a serious illness affecting the lives and health of elderly individuals. However, effective treatments are still lacking. OA is typically considered a low-grade inflammatory state. The inflammatory infiltration of macrophages, neutrophils, T cells, and other cells is common in diseased joints. These cells create the inflammatory environment of OA and are involved in the onset and progression of the disease. Exosomes, a type of complex vesicle containing abundant RNA molecules and proteins, play a crucial role in the physiological and pathological processes of an organism. In comparison to other therapeutic methods such as stem cells, exosomes have distinct advantages of precise targeting and low immunogenicity. Moreover, research and techniques related to exosomes are more mature, indicating a promising future in disease treatment. Many studies have shown that the impact of exosomes on the inflammatory microenvironment directly or indirectly leads to the occurrence of various diseases. Furthermore, exosomes can be helpful in the management of illnesses. This article provides a comprehensive review and update on the research of exosomes, a type of extracellular vesicle, in the treatment of OA by modulating the inflammatory microenvironment. It also combines innovative studies on the modification of exosomes. In general, the application of exosomes in the treatment of OA has been validated, and the introduction of modified exosome technology holds potential for enhancing its therapeutic efficacy.

Senescence-Associated miRNAs and Their Role in Pancreatic Cancer

Replicative senescence is irreversible cell proliferation arrest for somatic cells which can be circumvented in cancers. Cellular senescence is a process, which may play two opposite roles. On the one hand, this is a natural protection of somatic cells against unlimited proliferation and malignant transformation. On the other hand, cellular secretion caused by senescence can stimulate inflammation and proliferation of adjacent cells that may promote malignancy. The main genes controlling the senescence pathways are also well known as tumor suppressors. Almost 140 genes regulate both cellular senescence and cancer pathways. About two thirds of these genes (64%) are regulated by microRNAs. Senescence-associated miRNAs can stimulate cancer progression or act as tumor suppressors. Here we review the role playing by senescence-associated miRNAs in development, diagnostics and treatment of pancreatic cancer.

Dynamical modeling of miR-34a, miR-449a, and miR-16 reveals numerous DDR signaling pathways regulating senescence, autophagy, and apoptosis in HeLa cells

Transfection of tumor suppressor miRNAs such as miR-34a, miR-449a, and miR-16 with DNA damage can regulate apoptosis and senescence in cancer cells. miR-16 has been shown to influence autophagy in cervical cancer. However, the function of miR-34a and miR-449a in autophagy remains unknown. The functional and persistent G1/S checkpoint signaling pathways in HeLa cells via these three miRNAs, either synergistically or separately, remain a mystery. As a result, we present a synthetic Boolean network of the functional G1/S checkpoint regulation, illustrating the regulatory effects of these three miRNAs. To our knowledge, this is the first synthetic Boolean network that demonstrates the advanced role of these miRNAs in cervical cancer signaling pathways reliant on or independent of p53, such as MAPK or AMPK. We compared our estimated probability to the experimental data and found reasonable agreement. Our findings indicate that miR-34a or miR-16 may control senescence, autophagy, apoptosis, and the functional G1/S checkpoint. Additionally, miR-449a can regulate just senescence and apoptosis on an individual basis. MiR-449a can coordinate autophagy in HeLa cells in a synergistic manner with miR-16 and/or miR-34a.

Rapid changes of miRNAs-20, -30, -410, -515, -134, and -183 and telomerase with psychological activity: A one year study on the relaxation response and epistemological considerations

Background and aim

Mental stress represents a pivotal factor in cardiovascular diseases. The mechanism by which stress produces its deleterious effects is still under study, but one of the most explored pathways is inflammation-aging and cell senescence. In this scenario, circulating microRNAs appear to be regulatory elements of the telomerase activity and alternative splicing within the nuclear factor kappa-light-chain-enhancer (NF-κB) network. Anti-stress techniques appeared to be able to slow down the inflammatory and aging processes. As we recently verified, the practice of the relaxation response (RR) counteracted psychological stress and determined favorable changes of the NF-κB, p53, and toll-like receptor-4 (TLR-4) gene expression and in neurotransmitters, hormones, cytokines, and inflammatory circulating microRNAs. We aimed to verify a possible change in the serum levels of six other micro-RNAs of cardiovascular interest, involved in cell senescence and in the NF-κB network (miRNAs -20, -30, -410, -515, -134, and -183), and tested the activity of telomerase in peripheral blood mononuclear cells (PBMCs).

Experimental procedure

We measured the aforementioned molecules in the serum of patients with ischemic heart disease (and healthy controls) immediately before and after a relaxation response session, three times (after the baseline), in one year of follow-up.

Results

According to our data, the miRNA-20 and -30 levels and PBMCs-telomerase activity increased during the RR while the -410 and -515 levels decreased. During the RR sessions, both miRNA-134 and -183 decreased.

Conclusion

The mediators considered in this exploratory work appeared to vary rapidly with the psychological activity (in particular when focused on relaxation techniques) showing that psychological activity should be part of the future research on epigenetics. Epistemological perspectives are also discussed.

Mechanisms and therapeutic implications of cellular senescence in osteoarthritis

The development of osteoarthritis (OA) correlates with a rise in the number of senescent cells in joint tissues, and the senescence-associated secretory phenotype (SASP) has been implicated in cartilage degradation and OA. Age-related mitochondrial dysfunction and associated oxidative stress might induce senescence in joint tissue cells. However, senescence is not the only driver of OA, and the mechanisms by which senescent cells contribute to disease progression are not fully understood. Furthermore, it remains uncertain which joint cells and SASP-factors contribute to the OA phenotype. Research in the field has looked at developing therapeutics (namely senolytics and senomorphics) that eliminate or alter senescent cells to stop disease progression and pathogenesis. A better understanding of how senescence contributes to joint dysfunction may enhance the effectiveness of these approaches and provide relief for patients with OA.

Downregulation of p16 Decreases Biliary Damage and Liver Fibrosis in the Mdr2/ Mouse Model of Primary Sclerosing Cholangitis

Biliary senescence and hepatic fibrosis are hallmarks of cholangiopathies including primary sclerosing cholangitis (PSC). Senescent cholangiocytes display senescence-associated secretory phenotypes [SASPs, e.g., transforming growth factor-1 (TGF-1)] that further increase biliary senescence (by an autocrine loop) and trigger liver fibrosis by paracrine mechanisms. The aim of this study was to determine the effect of p16 inhibition and role of the TGF-1/microRNA (miR)-34a/sirtuin 1 (SIRT1) axis in biliary damage and liver fibrosis in the Mdr2/ mouse model of PSC. We treated (i) in vivo male wild-type (WT) and Mdr2/ mice with p16 Vivo-Morpholino or controls before measuring biliary mass [intrahepatic bile duct mass (IBDM)] and senescence, biliary SASP levels, and liver fibrosis, and (ii) in vitro intrahepatic murine cholangiocyte lines (IMCLs) with small interfering RNA against p16 before measuring the mRNA expression of proliferation, senescence, and fibrosis markers. p16 and miR-34a increased but SIRT1 decreased in Mdr2/ mice and PSC human liver samples compared to controls. p16 immunoreactivity and biliary senescence and SASP levels increased in Mdr2/ mice but decreased in Mdr2/ mice treated with p16 Vivo-Morpholino. The increase in IBDM and hepatic fibrosis (observed in Mdr2/ mice) returned to normal values in Mdr2/ mice treated with p16 Vivo-Morpholino. TGF-1 immunoreactivity and biliary SASPs levels were higher in Mdr2/ compared to those of WT mice but returned to normal values in Mdr2/ mice treated with p16 Vivo-Morpholino. The expression of fibrosis/senescence markers decreased in cholangiocytes from Mdr2/ mice treated with p16 Vivo-Morpholino (compared to Mdr2/ mice) and in IMCLs (after p16 silencing) compared to controls. Modulation of the TGF-1/miR-34a/SIRT1 axis may be important in the management of PSC phenotypes.

Oxidative Stress Down-Regulates MiR-20b-5p, MiR-106a-5p and E2F1 Expression to Suppress the G1/S Transition of the Cell Cycle in Multipotent Stromal Cells

Oxidative stress has been linked to senescence and tumorigenesis via modulation of the cell cycle. Using a hydrogen peroxide (H₂O₂)-induced oxidative stress-induced premature senescence (OSIPS) model previously reported by our group, this study aimed to investigate the effects of oxidative stress on microRNA (miRNA) expression in relation to the G1-to-S-phase (G1/S) transition of the cell cycle and cell proliferation. On global miRNA analysis of the OSIPS cells, twelve significantly up- or down-regulated miRNAs were identified, the target genes of which are frequently associated with cancers. Four down-regulated miR-17 family miRNAs are predicted to target key pro- and anti-proliferative proteins of the p21/cyclin D-dependent kinase (CDK)/E2F1 pathway to modulate G1/S transition. Two miR-17 miRNAs, miR-20-5p and miR-106-5p, were confirmed to be rapidly and stably down-regulated under oxidative stress. While H₂O₂ treatment hampered G1/S transition and suppressed DNA synthesis, miR-20b-5p/miR-106a-5p over-expression rescued cells from growth arrest in promoting G1/S transition and DNA synthesis. Direct miR-20b-5p/miR-106a-5p regulation of p21, CCND1 and E2F1 was demonstrated by an inverse expression relationship in miRNA mimic-transfected cells. However, under oxidative stress, E2F1 expression was down-regulated, consistent with hampered G1/S transition and suppressed DNA synthesis and cell proliferation. To explain the observed E2F1 down-regulation under oxidative stress, a scheme is proposed which includes miR-20b-5p/miR-106a-5p-dependent regulation, miRNA-E2F1 autoregulatory feedback and E2F1 response to repair oxidative stress-induced DNA damages. The oxidative stress-modulated expression of miR-17 miRNAs and E2F1 may be used to develop strategies to retard or reverse MSC senescence in culture, or senescence in general.

Senescence cell-associated extracellular vesicles serve as osteoarthritis disease and therapeutic markers

Senescent cells (SnCs) are increasingly recognized as central effector cells in age-related pathologies. Extracellular vesicles (EVs) are potential cellular communication tools through which SnCs exert central effector functions in the local tissue environment. To test this hypothesis in a medical indication that could be validated clinically, we evaluated EV production from SnCs enriched from chondrocytes isolated from human arthritic cartilage. EV production increased in a dose-responsive manner as the concentration of SnCs increased. The EVs were capable of transferring senescence to nonsenescent chondrocytes and inhibited cartilage formation by non-SnCs. microRNA (miR) profiles of EVs isolated from human arthritic synovial fluid did not fully overlap with the senescent chondrocyte EV profiles. The effect of SnC clearance was tested in a murine model of posttraumatic osteoarthritis. miR and protein profiles changed after senolytic treatment but varied depending on age. In young animals, senolytic treatment altered expression of miR-34a, -30c, -125a, -24, -92a, -150, and -186, and this expression correlated with cartilage production. The primary changes in EV contents in aged mice after senolytic treatment, which only reduced pain and degeneration, were immune related. In sum, EV contents found in synovial fluid may serve as a diagnostic for arthritic disease and indicator for therapeutic efficacy of senolytic treatment.

The role of microRNAs involved in PI3-kinase signaling pathway in colorectal cancer

In recent decades, cancer has been one of the most important concerns of the human community, which affects human life from many different ways, such as breast, lung, colorectal, prostate, and other cancers. Colorectal cancer is one of the most commonly diagnosed cancers in the world that has recently been introduced as the third leading cause of cancer deaths in the world. microRNAs have a very crucial role in tumorgenesis and prevention of cancer, which plays a significant role with influencing various factors through different signaling pathways. Phosphoinositide 3 (PI3)-kinase/AKT is one of the most important signaling pathways involved in the control and growth of tumor in colorectal cancer, through important proteins of this pathway, such as PTEN and AKT, that they can perform specific influence on this process. Our effort in this study is to collect microRNAs that act as tumor suppressors and oncomirs in this cancer through PI3-kinase/AKT signaling pathway.

Kallistatin attenuates endothelial senescence by modulating Let-7g-mediated miR-34a-SIRT1-eNOS pathway

Kallistatin, a plasma protein, protects against vascular and organ injury. This study is aimed to investigate the role and mechanism of kallistatin in endothelial senescence. Kallistatin inhibited H2 O2 -induced senescence in human endothelial cells, as indicated by reduced senescence-associated-β-galactosidase activity, p16INK4a and plasminogen activator inhibitor-1 expression, and elevated telomerase activity. Kallistatin blocked H2 O2 -induced superoxide formation, NADPH oxidase levels and VCAM-1, ICAM-1, IL-6 and miR-34a synthesis. Kallistatin reversed H2 O2 -mediated inhibition of endothelial nitric oxide synthase (eNOS), SIRT1, catalase and superoxide dismutase (SOD)-2 expression, and kallistatin alone stimulated the synthesis of these antioxidant enzymes. Moreover, kallistatin's anti-senescence and anti-oxidant effects were attributed to SIRT1-mediated eNOS pathway. Kallistatin, via interaction with tyrosine kinase, up-regulated Let-7g, whereas Let-7g inhibitor abolished kallistatin's effects on miR-34a and SIRT1/eNOS synthesis, leading to inhibition of senescence, oxidative stress and inflammation. Furthermore, lung endothelial cells isolated from endothelium-specific kallistatin knockout mice displayed marked reduction in mouse kallistatin levels. Kallistatin deficiency in mouse endothelial cells exacerbated senescence, oxidative stress and inflammation compared to wild-type mouse endothelial cells, and H2 O2 treatment further magnified these effects. Kallistatin deficiency caused marked reduction in Let-7g, SIRT1, eNOS, catalase and SOD-1 mRNA levels, and elevated miR-34a synthesis in mouse endothelial cells. These findings indicate that endogenous kallistatin through novel mechanisms protects against endothelial senescence by modulating Let-7g-mediated miR-34a-SIRT1-eNOS pathway.

DGCR8 is essential for tumor progression following PTEN loss in the prostate

In human prostate cancer, the microRNA biogenesis machinery increases with prostate cancer progression. Here, we show that deletion of the Dgcr8 gene, a critical component of this complex, inhibits tumor progression in a Pten-knockout mouse model of prostate cancer. Early stages of tumor development were unaffected, but progression to advanced prostatic intraepithelial neoplasia was severely inhibited. Dgcr8 loss blocked Pten null-induced expansion of the basal-like, but not luminal, cellular compartment. Furthermore, while late-stage Pten knockout tumors exhibit decreased senescence-associated beta-galactosidase activity and increased proliferation, the simultaneous deletion of Dgcr8 blocked these changes resulting in levels similar to wild type. Sequencing of small RNAs in isolated epithelial cells uncovered numerous miRNA changes associated with PTEN loss. Consistent with a Pten-Dgcr8 association, analysis of a large cohort of human prostate tumors shows a strong correlation between Akt activation and increased Dgcr8 mRNA levels. Together, these findings uncover a critical role for microRNAs in enhancing proliferation and enabling the expansion of the basal cell compartment associated with tumor progression following Pten loss.

Disruptive chemicals, senescence and immortality

Carcinogenesis is thought to be a multistep process, with clonal evolution playing a central role in the process. Clonal evolution involves the repeated 'selection and succession' of rare variant cells that acquire a growth advantage over the remaining cell population through the acquisition of 'driver mutations' enabling a selective advantage in a particular micro-environment. Clonal selection is the driving force behind tumorigenesis and possesses three basic requirements: (i) effective competitive proliferation of the variant clone when compared with its neighboring cells, (ii) acquisition of an indefinite capacity for self-renewal, and (iii) establishment of sufficiently high levels of genetic and epigenetic variability to permit the emergence of rare variants. However, several questions regarding the process of clonal evolution remain. Which cellular processes initiate carcinogenesis in the first place? To what extent are environmental carcinogens responsible for the initiation of clonal evolution? What are the roles of genotoxic and non-genotoxic carcinogens in carcinogenesis? What are the underlying mechanisms responsible for chemical carcinogen-induced cellular immortality? Here, we explore the possible mechanisms of cellular immortalization, the contribution of immortalization to tumorigenesis and the mechanisms by which chemical carcinogens may contribute to these processes.

Cellular senescence: from growth arrest to immunogenic conversion

Cellular senescence was first reported in human fibroblasts as a state of stable in vitro growth arrest following extended culture. Since that initial observation, a variety of other phenotypic characteristics have been shown to co-associate with irreversible cell cycle exit in senescent fibroblasts. These include (1) a pro-inflammatory secretory response, (2) the up-regulation of immune ligands, (3) altered responses to apoptotic stimuli and (4) promiscuous gene expression (stochastic activation of genes possibly as a result of chromatin remodeling). Many features associated with senescent fibroblasts appear to promote conversion to an immunogenic phenotype that facilitates self-elimination by the immune system. Pro-inflammatory cytokines can attract and activate immune cells, the presentation of membrane bound immune ligands allows for specific recognition and promiscuous gene expression may function to generate an array of tissue restricted proteins that could subsequently be processed into peptides for presentation via MHC molecules. However, the phenotypes of senescent cells from different tissues and species are often assumed to be broadly similar to those seen in senescent human fibroblasts, but the data show a more complex picture in which the growth arrest mechanism, tissue of origin and species can all radically modulate this basic pattern. Furthermore, well-established triggers of cell senescence are often associated with a DNA damage response (DDR), but this may not be a universal feature of senescent cells. As such, we discuss the role of DNA damage in regulating an immunogenic response in senescent cells, in addition to discussing less established "atypical" senescent states that may occur independent of DNA damage.

Multiple myeloma cells alter the senescence phenotype of bone marrow mesenchymal stromal cells under participation of the DLK1-DIO3 genomic region

Background

Alterations and senescence in bone marrow mesenchymal stromal cells of multiple myeloma patients (MM-BMMSCs) have become an important research focus. However the role of senescence in the pathophysiology of MM is not clear.

Methods

Correlation between senescence, cell cycle and microRNA expression of MM-BMMSCs (n = 89) was analyzed. Gene expression analysis, copy number analysis and methylation specific PCR were performed by Real-Time PCR. Furthermore, cyclin E1, cyclin D1, p16 and p21 genes were analyzed at the protein level using ELISA. Cell cycle and senescence were analyzed by FACS. MiRNA transfection was performed with miR-485-5p inhibitor and mimic followed by downstream analysis of senescence and cell cycle characteristics of MM-BMMSCs. Results were analyzed by Mann–Whitney U test, Wilcoxon signed-rank test and paired t-test depending on the experimental set up.

Results

MM-BMMSCs displayed increased senescence associated β-galactosidase activity (SA-βGalA), cell cycle arrest in S phase and overexpression of microRNAs. The overexpressed microRNAs miR-485-5p and miR-519d are located on DLK1-DIO3 and C19MC, respectively. Analyses revealed copy number accumulation and hypomethylation of both clusters. KMS12-PE myeloma cells decreased SA-βGalA and influenced cell cycle characteristics of MM-BMMSCs. MiR-485-5p was significantly decreased in co-cultured MM-BMMSCs in connection with an increased methylation of DLK1-DIO3. Modification of miR-485-5p levels using microRNA mimic or inhibitor altered senescence and cell cycle characteristics of MM-BMMSCs.

Conclusions

Here, we show for the first time that MM-BMMSCs have aberrant methylation and copy number of the DLK1-DIO3 and C19MC genomic region. Furthermore, this is the first study pointing that multiple myeloma cells in vitro reduce both the senescence phenotype of MM-BMMSCs and the expression of miR-223 and miR-485-5p. Thus, it is questionable whether senescence of MM-BMMSCs plays a pathological role in active multiple myeloma or is more important when cell interaction with myeloma cells is inhibited. Furthermore, we found that MiR-485-5p, which is located on the DLK1-DIO3 cluster, seems to participate in the regulation of senescence status and cell cycle characteristics of MM-BMMSCs. Thus, further exploration of the microRNAs of DLK1-DIO3 could provide further insights into the origin of the senescence state and its reversal in MM-BMMSCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1078-3) contains supplementary material, which is available to authorized users.

Senescence at a glance

Cellular senescence is a stable proliferation arrest that is associated with extensive cellular remodelling and an altered secretory pathway. Through its numerous inducers that lead to altered gene expression, senescence is able to influence many contrasting functions and pathologies, namely tumour suppression, tumour promotion, wound healing and ageing. As senescence is able to control such important tissue functions, it is now being pinpointed as a possible route for novel therapies. This article and accompanying poster aim to provide a summary of the initiators, pathways and roles of senescence, as well as present examples of senescence and a possible use for senescence in therapy.

Regulation of senescence by microRNA biogenesis factors

Senescence represents a state of indefinite growth arrest in cells that have reached the end of their replicative life span, have become damaged, or express aberrant levels of cancer-related proteins. While senescence is widely considered to represent a tumor-suppressive mechanism, the accumulation of senescent cells in tissues of older organisms is believed to underlie age-associated losses in physiologic function and age-related diseases. With the emergence of microRNAs (miRNAs) as a major class of molecular regulators of senescence, we review the transcriptional and post-transcriptional factors that control senescence-associated microRNA biosynthesis. Focusing on their enhancement or repression of senescence, we describe the transcription factors that govern the synthesis of primary (pri-)miRNAs, the proteins that control the nuclear processing of pri-miRNAs into precursor (pre-)miRNAs, including RNA editing enzymes, RNases, and RNA helicases, and the cytoplasmic proteins that affect the final processing of pre-miRNAs into mature miRNAs. We discuss how miRNA biogenesis proteins promote or inhibit senescence, and thus influence the senescent phenotype that affects normal tissue function and pathology.

Irinotecan induces senescence and apoptosis in colonic cells in vitro

Irinotecan (CPT-11) is topoisomerase I inhibitor used in the treatment of disseminated colorectal cancer. In colon cancer cells it induces DNA damage which leads to cytotoxicity with ensuing apoptosis or premature senescence. Despite its clinical use and efficiency in malignant colonocytes, its effects in normal colonic cells are relatively underexplored. In this work we report that CPT-11 induces dose-dependent cytotoxicity which results in apoptosis and premature senescence whose occurrence nevertheless varies in relation to the type of exposed cells. In normal colonic epithelial cells (NCM) the prevailing type of response is apoptosis whereas in normal colonic fibroblasts (NCF) it is premature senescence. Further analyses showed that CPT-11 induced in both types of cells DNA damage and activated stress response pathways including p53 and p16 but with varying activity of stress kinase p38 and selected stress-associated microRNAs. Epithelial cells upregulated the expression of p53, which was subsequently specifically phosphorylated, massively activated p38 and initiated mitochondrial, caspase-dependent apoptosis. These events occurred in the presence of moderately increased expression of miR-34a only. Conversely, in colonic fibroblasts p38 was only moderately activated, p53 as well as p16 expressions were upregulated in the presence of increased expression of miR-34a, miR-128a and miR-449a. Caspase-dependent apoptosis was found only in a minority of treated cells and the premature senescence phenotype was prevailing. Specific inhibition further proved that p53-dependent as well as independent mechanisms might be responsible for these cell type-specific differences.