MiR-21 overexpression improves osteoporosis by targeting RECK

Expression of Reversion-Inducing Cysteine-Rich Protein with Kazal Motifs (RECK) Gene and Its Regulation by miR200b in Ovarian Endometriosis

Endometriosis is a common chronic disorder characterized by the growth of endometrium-like tissue outside the uterine cavity. The disease is associated with chronic inflammation and pelvic pain and may have an impact on the patient's fertility. The causative factors and pathophysiology of the disease are still poorly recognized. The dysregulation of the immune system, aberrant tissue remodeling, and angiogenesis contribute to the disease progression. In endometriosis patients, the proteins regulating the breakdown and reorganization of the connective tissue, e.g., collagenases, and other proteases, as well as their inhibitors, show an incorrect pattern of expression. Here, we report that the expression of reversion-inducing cysteine-rich protein with Kazal motifs (RECK), one of the inhibitors of connective tissue proteases, is elevated in endometrioma cysts as compared to normal endometrium from unaffected women. We also demonstrate a reduced level of miR200b in endometriotic tissue that correlates with RECK mRNA levels. Furthermore, we employ the 12Z cell line, derived from a peritoneal endometriotic lesion, and the Ishikawa cell line, originating from endometrial adenocarcinoma to identify RECK as a direct target of miR200b. The described effect of miR200b on RECK, together with the aberrant expression of both genes in endometrioma, may help to understand the role played by the tissue remodeling system in the pathogenesis of endometriosis.

The Ambivalent Role of miRNA-21 in Trauma and Acute Organ Injury

Since their initial recognition, miRNAs have been the subject of rising scientific interest. Especially in recent years, miRNAs have been recognized to play an important role in the mediation of various diseases, and further, their potential as biomarkers was recognized. Rising attention has also been given to miRNA-21, which has proven to play an ambivalent role as a biomarker. Responding to the demand for biomarkers in the trauma field, the present review summarizes the contrary roles of miRNA-21 in acute organ damage after trauma with a specific focus on the role of miRNA-21 in traumatic brain injury, spinal cord injury, cardiac damage, lung injury, and bone injury. This review is based on a PubMed literature search including the terms "miRNA-21" and "trauma", "miRNA-21" and "severe injury", and "miRNA-21" and "acute lung respiratory distress syndrome". The present summary makes it clear that miRNA-21 has both beneficial and detrimental effects in various acute organ injuries, which precludes its utility as a biomarker but makes it intriguing for mechanistic investigations in the trauma field.

Human Aging and Age-Related Diseases: From Underlying Mechanisms to Pro-Longevity Interventions

As human life expectancy continues to rise, becoming a pressing global concern, it brings into focus the underlying mechanisms of aging. The increasing lifespan has led to a growing elderly population grappling with age-related diseases (ARDs), which strains healthcare systems and economies worldwide. While human senescence was once regarded as an immutable and inexorable phenomenon, impervious to interventions, the emerging field of geroscience now offers innovative approaches to aging, holding the promise of extending the period of healthspan in humans. Understanding the intricate links between aging and pathologies is essential in addressing the challenges presented by aging populations. A substantial body of evidence indicates shared mechanisms and pathways contributing to the development and progression of various ARDs. Consequently, novel interventions targeting the intrinsic mechanisms of aging have the potential to delay the onset of diverse pathological conditions, thereby extending healthspan. In this narrative review, we discuss the most promising methods and interventions aimed at modulating aging, which harbor the potential to mitigate ARDs in the future. We also outline the complexity of senescence and review recent empirical evidence to identify rational strategies for promoting healthy aging.

Up-regulation of plasma miRNA-21 and miRNA-422a in postmenopausal osteoporosis

BACKGROUND

Many researchers focused on diverse miRNAs in the progression of osteoporosis in postmenopausal women. This study aimed to evaluate the association between plasma miRNA-21-5p and miRNA-422a with osteoporosis in postmenopausal women.

METHODS

This cross-sectional comparative study was performed on 126 randomly selected postmenopausal women aged 50-65, including 65 osteoporotic and 61 normal-bone mineral density (BMD) women. miRNA-21 and miRNA-422a were identified using qRT-PCR in these women. BMD was evaluated by the dual-energy X-ray absorptiometry method. A binary logistic regression model adjusted for confounders was used to evaluate the associations between plasma miRNAs' expression levels and osteoporosis. The Area Under Curve (AUC) was calculated to differentiate low BMD in the postmenopausal period using Receiver-Operator Characteristic (ROC) curves.

RESULTS

miRNA-21 and miRNA-422a were significantly up-regulated in osteoporotic compared to non-osteoporotic postmenopausal women. The expression levels of miRNA-21 and miRNA-422a indicated a significant reverse correlation with both lumbar spine and femoral neck density. After adjusting the confounders, the likelihood of osteoporosis in the postmenopausal women with under the median plasma levels of miRNA-21 (OR = 0.025; 95% CI: 0.003 to 0.198, p<0.001) and miRNA-422a (OR = 0.037; 95% CI: 0.007 to 0.211, p<0.001) was significantly less than the women with the levels above the median. There were significant inverse correlations between miRNA-21 (p<0.001, r = -0.511) and miRNA-422a (p<0.001, r = -0.682) with BMD-lumbar spine as well as an inverse correlation between miRNA-21(p<0.001, r = -0.374) and miRNA-422a (p<0.001, r = -0.602) with BMD-femoral neck. The AUC (95%CI) for miRNA-21 and miRNA-422a was 0.84 (0.77 to 0.91) and 0.98 (0.96 to 0.99), respectively. ROC analysis illustrated that sensitivity and specificity values were 83.1% and 74%, respectively, for miRNA-21 at the cut-off point of 3.38. Also, at the cut-off point of 2.86, a sensitivity of 94% as well as a specificity of 89% was determined for miRNA-422a.

CONCLUSIONS

This study indicated that the odds of osteoporosis in postmenopausal women increased with the higher expression of plasma miRNA-21 and miRNA-422a.

The Potential of miR-21 in Stem Cell Differentiation and its Application in Tissue Engineering and Regenerative Medicine

MicroRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are two important types of non-coding RNAs that are not translated into protein. These molecules can regulate various biological processes, including stem cell differentiation and self-renewal. One of the first known miRNAs in mammals is miR-21. Cancer-related studies have shown that this miRNA has proto-oncogene activity and is elevated in cancers. However, it is confirmed that miR-21 inhibits stem cell pluripotency and self-renewal and induces differentiation by targeting various genes. Regenerative medicine is a field of medical science that tries to regenerate and repair damaged tissues. Various studies have shown that miR-21 plays an essential role in regenerative medicine by affecting stem cell proliferation and differentiation. In this review, we will discuss the function of miR-21 in regenerative medicine of the liver, nerve, spinal cord, wound, bone, and dental tissues. In addition, the function of natural compounds and lncRNAs will be analyzed as potential regulators of miR-21 expression in regenerative medicine.

Ageing at Molecular Level: Role of MicroRNAs

The progression of age triggers a vast number of diseases including cardiovascular, cancer, and neurodegenerative disorders. Regardless of our plentiful knowledge about age-related diseases, little is understood about molecular pathways that associate the ageing process with various diseases. Several cellular events like senescence, telomere dysfunction, alterations in protein processing, and regulation of gene expression are common between ageing and associated diseases. Accumulating information on the role of microRNAs (miRNAs) suggests targeting miRNAs can aid our understanding of the interplay between ageing and associated diseases. In the present chapter, we have attempted to explore the information available on the role of miRNAs in ageing of various tissues/organs and diseases and understand the molecular mechanism of ageing.

Morinda officinalis polysaccharide regulates rat bone mesenchymal stem cell osteogenic-adipogenic differentiation in osteoporosis by upregulating miR-21 and activating the PI3K/AKT pathway

Osteoporosis (OP) is a prevailing bone metabolic disease. Morinda officinalis polysaccharide (MOP) has biological activities and medicinal potential. This study explored its mechanism in OP. Rat bone mesenchymal stem cells (rBMSCs) were pretreated with low/high concentrations of MOP and subjected to osteogenic differentiation (OD) or adipogenic differentiation (AD) induction. The protein markers of OD (RUNX2 and BMP2) and AD (CEBPα and PPARγ) and miR-21 expression were detected. miR-21 was overexpressed to study its effects on rBMSC OD and AD. rBMSCs were transfected with miR-21 inhibitor and treated with high concentration of MOP for verification. The targeted relationship between miR-21 and PTEN was verified by bioinformatics and dual-luciferase assay. The PTEN/PI3K/AKT pathway-related proteins were detected. Ovariectomy (OVX)-induced OP rats were treated with MOP. Rat bone mineral density (BMD), serum bone metabolism indexes bone-derived alkaline phosphatase (BALP), and osteocalcin (BGP) levels were assessed by BMD detectors and ELISA kits. miR-21 expression in rBMSCs was detected. After treatment with low/high concentrations of MOP, the OD of rBMSCs was increased and AD was inhibited and miR-21 was upregulated. miR-21 overexpression enhanced the OD of rBMSCs and inhibited AD. miR-21 knockdown reversed the effect of high concentration of MOP on rBMSCs. miR-21 targeted PTEN. After treatment with low/high concentrations of MOP, PI3K, and AKT phosphorylation were increased and the PI3K/AKT pathway was activated. BMD, BALP, BGP, and miR-21 levels in OVX rats were decreased. MOP partially alleviated OP in OVX rats. Briefly, MOP enhanced rBMSC OD and inhibited AD via the miR-21/PTEN/PI3K/AKT axis.

Exosomes derived from microRNA-21 overexpressed adipose tissue-derived mesenchymal stem cells alleviate spine osteoporosis in ankylosing spondylitis mice

MicroRNA-21 (miR-21) can induce proliferation and differentiation of mesenchymal stem cells (MSCs) to promote bone formation, we therefore aimed to investigate whether exosomes derived from miR-21 overexpressing adipose tissue-derived MSCs (AD-MSCs) could improve spine osteoporosis in ankylosing spondylitis (AS) mice. Cultured AD-MSCs were transfected with lentivirus vectors containing miR-21 or control vector, and the supernatant was centrifugated and filtrated to harvest the exosomes (miR-21-Exos or vector-Exos). BALB/c mice were immunized with cartilage proteoglycan to establish proteoglycan-induced ankylosing spondylitis (PGIA) model. Six weeks later, PGIA mice were further injected with miR-21-Exos or vector-Exos. Transfection of miR-21 in AD-MSCs significantly enhanced miR-21 levels in AD-MSCs and their exosomes. miR-21-Exos showed concentration-dependent protective effect against spine osteoporosis in PGIA mice, evidenced by increased bone mineral content and bone mineral density, reduced number of osteoclasts, decreased content of deoxypyridinoline in the urine, decreased content of tartrate-resistant acid phosphatase (TRACP)-5b and cathepsin K in the serum, and down-regulated interleukin (IL)-6 expression in the spine, whereas vector-Exos did not show any treatment benefit. The above findings indicate that miR-21-Exos could be utilized to treat spine osteoporosis in AS.

WITHDRAWN: Role of microRNA-19b-3p on osteoporosis after experimental spinal cord injury in rats

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

MicroRNA-21: An Emerging Player in Bone Diseases

MicroRNAs (MiRNAs) are small endogenous non-coding RNAs that bind to the 3′-untranslated region of target genes and promote their degradation or inhibit translation, thereby regulating gene expression. MiRNAs are ubiquitous in biology and are involved in many biological processes, playing an important role in a variety of physiological and pathological processes. MiRNA-21 (miR-21) is one of them. In recent years, miR-21 has received a lot of attention from researchers as an emerging player in orthopedic diseases. MiR-21 is closely associated with the occurrence, development, treatment, and prevention of orthopedic diseases through a variety of mechanisms. This review summarizes its effects on osteoblasts, osteoclasts and their relationship with osteoporosis, fracture, osteoarthritis (OA), osteonecrosis, providing a new way of thinking for the diagnosis, treatment and prevention of these bone diseases.

Effects of miRNAs, lncRNAs and circRNAs on osteoporosis as regulatory factors of bone homeostasis (Review)

Osteoporosis is a common metabolic bone disorder typically characterized by decreased bone mass and an increased risk of fracture. At present, the detailed molecular mechanism underlying the development of osteoporosis remains to be elucidated. Accumulating evidence shows that non-coding (nc)RNAs, such as microRNAs (miRNAs), long ncRNAs (lncRNAs) and circular RNAs (circRNAs), play significant roles in osteoporosis through the post-transcriptional regulation of gene expression as regulatory factors. Previous studies have demonstrated that ncRNAs participate in maintaining bone homeostasis by regulating physiological and developmental processes in osteoblasts, osteoclasts and bone marrow stromal cells. In the present review, the latest research investigating the involvement of miRNAs, lncRNAs and circRNAs in regulating the differentiation, proliferation, apoptosis and autophagy of cells that maintain the bone microenvironment in osteoporosis is summarized. Deeper insight into the aspects of osteoporosis pathogenesis involving the deregulation of ncRNAs could facilitate the development of therapeutic approaches for osteoporosis.

The role of exosomal non-coding RNAs in aging-related diseases

Aging is a biological process caused by the accumulation of senescent cells with a permanent proliferative arrest. To the influence of aging on human life expectancy, there is essential for new biomarkers which possibly will assistance in recognizing age-associated pathologies. Exosomes, which are cell-secreted nanovesicles, make available a new biomarker detection and therapeutic approach for the transfer of different molecules with high capacity. Recently, non-coding RNAs (ncRNA) which are contained in exosomes have developed as important molecules regulating the complexity of aging and relevant human diseases. The discovery of ncRNA provided perceptions into an innovative regulatory platform that could interfere with cellular senescence. The non-coding transcriptome includes a different of RNA species, spanning from short ncRNAs (<200 nucleotides) to long ncRNAs, that are >200 bp long. Upgraded evidence displays that targeting ncRNAs possibly will influence senescence pathways. In this article, we will address ncRNAs that participated in age-related and cellular senescence diseases. Growing conception of ncRNAs in the aging process possibly will be responsible for new understandings into the improvement of age-related diseases and elongated life span.

Size changes in miR‑21 knockout mice: Geometric morphometrics on teeth, alveolar bone and mandible

MicroRNA‑21 (miR‑21) is a small non‑coding RNA that is differentially expressed during tooth development, particularly during amelogenesis. Although orthodontic tooth movement and the innate immune response are impaired, miR‑21 knockout mice demonstrate no obvious skeletal phenotype. However, the consequence of miR‑21 knockout on tooth phenotype and corresponding alveolar bone is unknown. The current study utilized landmark‑based geometric morphometrics to identify anatomical dissimilarities of the three lower and upper molars, and the corresponding alveolar bone, in miR‑21 knockout and wild‑type control mice. The anatomical structures were visualized by microcomputer tomography. A total of 36 and 38 landmarks were placed on mandibular and maxillary molars, respectively. For the alveolar bone, 16 landmarks were selected on both anatomical sites. General Procrustes analysis revealed significantly smaller molars and dimensions of the alveolar bone in the mandible of the miR‑21 knockout mice when compared with wild‑type controls (P=0.03 and P=0.04, respectively). The overall dimension of the mandible was reduced by the lack of miR‑21 (P=0.02). In the maxilla, the dimension of the alveolar bone was significant (P=0.02); however, this was not observed in the molars (P=0.36). Based on principal component analysis, no changes in shape for any of the anatomical sites were observed. Dental and skeletal jaw length were calculated and no prognathism was identified. However, the fluctuating asymmetry of the molars in the mandible and the maxilla was reduced in the miR‑21 knockout mice by 38 and 27%, respectively. Taken together, the results of the present study revealed that the molars in the mandible and the dimension of the respective alveolar bone were smaller in miR‑21 mice compared with wild‑type littermates, suggesting that miR‑21 influences tooth development.

lncRNA XIST regulates cell proliferation, migration and invasion via regulating miR-30b and RECK in nasopharyngeal carcinoma

Long non-coding RNA (lncRNA) X-inactive specific transcript (XIST) plays an essential role in the development and progress of nasopharyngeal carcinoma (NPC). MicroRNA-30b (miR-30b) has been confirmed to play an inhibitory role in various types of cancer. The molecular mechanisms underlying the lncRNA XIST-mediated regulation of the metastasis of NPC cells by miR-30b is not clear. qPCR and western blot analysis were used to detect the expression of XIST, miR-30b, and reversion inducing cysteine rich protein with kazal motifs (RECK) in NPC tissues and cell lines. The detection of luciferase reporter gene confirmed the relationship between lncRNA XIST, miR-30b and RECK. CCK-8 and Transwell assays were performed in order to detect the proliferation, migration and invasion of the NPC cells. The results of qPCR and western blotting indicated that the expression levels of lncRNA XIST and RECK were higher in the NPC tissues and cell lines than that of the control group, while the expression of miR-30b was lower. Knockdown of lncRNA XIST significantly inhibited cell proliferation, migration and invasion in the NPC cell lines. In addition, lncRNA XIST was found to negatively regulate the expression of miR-30b, resulting in the upregulation of RECK. Overexpression of RECK was found to reverse the inhibitory effect of lncRNA XIST knockdown or miR-30b on NPC cell metastasis. Our results showed that cell migration and invasion were inhibited by knockdown of lncRNA XIST, suggesting that the lncRNA XIST/miR-30b/RECK axis is involved in the development of NPC.

lncRNA GAS5 Is Upregulated in Osteoporosis and Downregulates miR-21 to Promote Apoptosis of Osteoclasts

Background

It has been reported that lncRNA growth arrest-specific transcript 5 (GAS5) interacts with miR-21, which plays critical roles in osteoporosis. The involvement of GAS5 in osteoporosis was investigated in this study.

Methods

Expression levels of GAS5 and miR-21 in plasma of both osteoporosis patients and healthy controls were determined by RT-qPCR. Diagnostic values of GAS5 and miR-21 for osteoporosis were analyzed by ROC curve analysis. Overexpression experiments were used to assess the interactions between GAS5 and miR-21. The roles of GAS5 and miR-21 in the apoptosis of osteoclasts were investigated by cell apoptosis assay.

Results

The present study aimed to investigate the roles of GAS5 in osteoporosis. The results showed that GAS5 was upregulated, while miR-21 was downregulated in plasma of osteoporosis patients. Expression levels of GAS5 and miR-21 were inversely correlated across plasma samples from osteoporosis patients but not the plasma samples from the controls. Altered expression of GAS5 and miR-21 distinguished osteoporosis patients from the controls. In osteoclasts, overexpression of GAS5 led to downregulation of miR-21, while overexpression of miR-21 did not affect the expression of GAS5. Overexpression of GAS5 led to promoted apoptosis of osteoclasts, while overexpression of miR-21 led to suppressed apoptosis of osteoclasts. In addition, overexpression of miR-21 attenuated the enhancing effects of overexpressing GAS5 on cell apoptosis.

Conclusion

GAS5 is upregulated in osteoporosis and may downregulate miR-21 to promote the apoptosis of osteoclasts.

miR-140-3p aggregates osteoporosis by targeting PTEN and activating PTEN/PI3K/AKT signaling pathway

Osteoporosis (OP) is a systemic bone metabolic disorder, which negatively affects the quality of life in the elders and postmenopausal females. Healthy volunteers and postmenopausal females with OP were enrolled in the present study. Bone densitometry (BMD) was detected by dual-energy X-ray absorptiometry (DXA). CD14+PBMCs and C2C12 cells were cultured to induce osteoclast differentiation and osteoblast differentiation, respectively. The interaction between miR‑140-3p and PTEN was predicted and verified by TargetScan 7.2 and dual luciferase reporter assay, respectively. miRNA/RNA level and protein level were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot, respectively. Cell proliferation and apoptosis were detected by 5-ethynyl-2'-deoxyuridine (EdU) staining and flow cytometry, respectively. Cell differentiation of CD14+PBMCs and C2C12 cells were detected by tartrate-resistant acid phosphatase (TRAP) staining and alizarin red staining, respectively. The activity of alkaline phosphatase (ALP) was detected by ALP assay. Differences were observed in age, body mass index (BMI), and BMD between the OP group and the control group. Higher miR‑140-3p level and lower PTEN level were found in PBMCs of OP group compared to control group; there was a negative correlation between them in the serum of OP group. miR-140-3p targeted and downregulated the expression of PTEN. miR-140-3p inhibitor inhibited cell proliferation, differentiation, and promoted cell apoptosis of CD14+PBMCs; while promoted cell proliferation, differentiation and inhibited cell apoptosis of C2C12 cells, by targeting PTEN and inactivating PTEN/PI3K/AKT signaling pathway. These findings suggested a potential therapeutic role of miR-140-3p in the treatment of patients with OP.

Zirconium Oxide Thin Films Obtained by Atomic Layer Deposition Technology Abolish the Anti-Osteogenic Effect Resulting from miR-21 Inhibition in the Pre-Osteoblastic MC3T3 Cell Line

Introduction

The development of the field of biomaterials engineering is rapid. Various bioactive coatings are created to improve the biocompatibility of substrates used for bone regeneration, which includes formulation of thin zirconia coatings with pro-osteogenic properties. The aim of this study was to assess the biological properties of ZrO₂ thin films grown by Atomic Layer Deposition (ALD) technology (ZrO₂^ALD).

Methodology

The cytocompatibility of the obtained layers was analysed using the mice pre-osteoblastic cell line (MC3T3) characterized by decreased expression of microRNA 21-5p (miR-21-5p) in order to evaluate the potential pro-osteogenic properties of the coatings. The in vitro experiments were designed to determine the effect of ZrO₂^ALD coatings on cell morphology (confocal microscope), proliferative activity (cell cycle analysis) and metabolism, reflected by mitochondrial membrane potential (cytometric-based measurement). Additionally, the influence of layers on the expression of genes associated with cell survival and osteogenesis was studied using RT-qPCR. The following genes were investigated: B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), p53 and p21, as well as osteogenic markers, i.e. collagen type 1 (Coll-1), osteopontin (Opn), osteocalcin (Ocl) and runt-related transcription factor 2 (Runx-2). The levels of microRNA (miRNA/miR) involved in the regulation of osteogenic genes were determined, including miR-7, miR-21, miR-124 and miR-223.

Results

The analysis revealed that the obtained coatings are cytocompatible and may increase the metabolism of pre-osteoblast, which was correlated with increased mitochondrial membrane potential and extensive development of the mitochondrial network. The obtained coatings affected the viability and proliferative status of cells, reducing the population of actively dividing cells. However, in cultures propagated on ZrO₂^ALD coatings, the up-regulation of genes essential for bone metabolism was noted.

Discussion

The data obtained indicate that ZrO₂ coatings created using the ALD method may have pro-osteogenic properties and may improve the metabolism of bone precursor cells. Given the above, further development of ZrO₂^ALD layers is essential in terms of their potential clinical application in bone regenerative medicine.

Elevation of long non-coding RNA GAS5 and knockdown of microRNA-21 up-regulate RECK expression to enhance esophageal squamous cell carcinoma cell radio-sensitivity after radiotherapy

OBJECTIVE

Lately, lncRNAs have been proposed to function in the radio-sensitivity of tumor cells, yet the role of lncRNA GAS5 in that of esophageal squamous cell carcinoma (ESCC) has scarcely been studied. This study aims to examine GAS5's effects on ESCC cell radio-sensitivity.

METHODS

GAS5, miR-21 and RECK expression in radiation-sensitive and radiation-resistant ESCC tissues, and TE-1 and TE-1-R cells was determined. TE-1 and TE-1-R cells were treated with pcDNA-GAS5 or miR-21 inhibitors to figure out their roles in ESCC cell proliferation, radio-sensitivity, and apoptosis via gain- and loss-of-function experiments.

RESULTS

We found underexpressed GAS5 and RECK, and overexpressed miR-21 in ESCC. GAS5 elevation and miR-21 inhibition reduced viability and the colony formation ability, and enhanced the apoptosis of ESCC cells under radiation.

CONCLUSION

Our study reveals that GAS5 elevation up-regulates RECK expression by down-regulating miR-21 to increase ESCC cell apoptosis after radiation therapy, thus enhancing cell radio-sensitivity.

MicroRNA-21 promotes bone reconstruction in maxillary bone defects

BACKGROUND

Bone reconstruction of the maxillary bone defects is an urgent issue due to its functional and aesthetic influence. MicroRNAs (miRNAs) are a class of non-coding RNAs that function in diverse biological and pathological processes. Recently, microRNA-21 (miR-21) was reported to play significant roles in bone formation, suggesting that miR-21 can be novel biomarker and therapeutic target for bone remodelling and skeletal diseases. However, the role of miR-21 in maxillary bone defects remains unclear.

OBJECTIVE AND METHODS

This study aimed to investigate the effect of miR-21 on the bone reconstruction by inducing maxillary bone defects in wild-type (WT) and miR-21 knockout (miR-21-KO) mice and explore these mice as maxillary bone defect models.

RESULTS

Micro-computed tomography (micro-CT) and histochemistry showed that the miR-21-KO mice had reduced bone reformation ability compared with the WT mice. The expression levels of alkaline phosphatase (ALP) and osteocalcin (OCN) were dramatically decreased in the miR-21-KO mice. In addition, injection of miR-21 agomir intra-peritoneally into miR-21-KO mice (miR-21-KO+ agomir) following the maxillary bone defects surgery displayed a significantly enhanced bone formation -promoting ability, which indicated that miR-21 agomir could ameliorate maxillary bone defects in miR-21-KO mice in vivo. Furthermore, immunohistochemistry suggested that ALP and OCN expressions were prominently increased in miR-21-KO+ agomir mice.

CONCLUSION

These findings demonstrated that miR-21 deficiency impaired bone reformation and miR-21 contributed to the bone reconstruction of the maxillary bone defects. The evidence also supported the use of WT and miR-21-KO mice as maxillary bone defect models for further research.

MicroRNAs as modulators of longevity and the aging process

MicroRNAs (miRNAs) are short, non-coding RNAs that post-transcriptionally repress translation or induce mRNA degradation of target transcripts through sequence-specific binding. miRNAs target hundreds of transcripts to regulate diverse biological pathways and processes, including aging. Many microRNAs are differentially expressed during aging, generating interest in their use as aging biomarkers and roles as regulators of the aging process. In the invertebrates Caenorhabditis elegans and Drosophila, a number of miRNAs have been found to both positive and negatively modulate longevity through canonical aging pathways. Recent studies have also shown that miRNAs regulate age-associated processes and pathologies in a diverse array of mammalian tissues, including brain, heart, bone, and muscle. The review will present an overview of these studies, highlighting the role of individual miRNAs as biomarkers of aging and regulators of longevity and tissue-specific aging processes.

Deregulated miRNAs in bone health: Epigenetic roles in osteoporosis

MicroRNA (miRNA) has shown to enhance or inhibit cell proliferation, differentiation and activity of different cell types in bone tissue. The discovery of miRNA actions and their targets has helped to identify them as novel regulations actors in bone. Various studies have shown that miRNA deregulation mediates the progression of bone-related pathologies, such as osteoporosis. The present review intends to give an exhaustive overview of miRNAs with experimentally validated targets involved in bone homeostasis and highlight their possible role in osteoporosis development. Moreover, the review analyzes miRNAs identified in clinical trials and involved in osteoporosis.

OsteoporosAtlas: a human osteoporosis-related gene database

Background

Osteoporosis is a common, complex disease of bone with a strong heritable component, characterized by low bone mineral density, microarchitectural deterioration of bone tissue and an increased risk of fracture. Due to limited drug selection for osteoporosis and increasing morbidity, mortality of osteoporotic fractures, osteoporosis has become a major health burden in aging societies. Current researches for identifying specific loci or genes involved in osteoporosis contribute to a greater understanding of the pathogenesis of osteoporosis and the development of better diagnosis, prevention and treatment strategies. However, little is known about how most causal genes work and interact to influence osteoporosis. Therefore, it is greatly significant to collect and analyze the studies involved in osteoporosis-related genes. Unfortunately, the information about all these osteoporosis-related genes is scattered in a large amount of extensive literature. Currently, there is no specialized database for easily accessing relevant information about osteoporosis-related genes and miRNAs.

Methods

We extracted data from literature abstracts in PubMed by text-mining and manual curation. Moreover, a local MySQL database containing all the data was developed with PHP on a Windows server.

Results

OsteoporosAtlas (http://biokb.ncpsb.org/osteoporosis/), the first specialized database for easily accessing relevant information such as osteoporosis-related genes and miRNAs, was constructed and served for researchers. OsteoporosAtlas enables users to retrieve, browse and download osteoporosis-related genes and miRNAs. Gene ontology and pathway analyses were integrated into OsteoporosAtlas. It currently includes 617 human encoding genes, 131 human non-coding miRNAs, and 128 functional roles. We think that OsteoporosAtlas will be an important bioinformatics resource to facilitate a better understanding of the pathogenesis of osteoporosis and developing better diagnosis, prevention and treatment strategies.

miR-363-3p is activated by MYB and regulates osteoporosis pathogenesis via PTEN/PI3K/AKT signaling pathway

Osteoporosis results from the imbalance between osteogenesis and bone resorption mediated by osteoblasts and osteoclasts. During the disease process of osteoporosis, the alteration of gene expression occurs, which lead to the disease progression. MicroRNAs (miRNAs) have been previously demonstrated to be modulators for bone metabolism via regulation of osteoblast and osteoclast differentiation. In the present study, we detected the expression levels of five osteoporosis-related miRNAs in bone and serum samples of patient with or without osteoporosis. The downstream molecular mechanism of miR-363-3p was analyzed and detected by using bioinformatics analysis and mechanism experiment. The upstream transcription factor of miR-363-3p was analyzed by applying bioinformatics analysis and ChIP assay and luciferase reporter assay. The role of this pathway in osteoclastogenesis was demonstrated by functional assays. MiR-363-3p was significantly highly expressed in osteoporotic samples. Mechanistically, miR-363-3p promotes osteoclastogenesis and inhibits osteogenic differentiation by targeting PTEN and therefore activating PI3K/AKT signaling pathway. MiR-363-3p was activated by its upstream transcription activator MYB. This study revealed that MYB-induced upregulation of miR-363-3p regulates osteoporosis pathogenesis via PTEN/PI3K/AKT signaling pathway.

Upregulation of MicroRNA-21 promotes tumorigenesis of prostate cancer cells by targeting KLF5

Prostate cancer (PCa) is the second frequently newly diagnosed cancer in men. Androgen deprivation therapy has been widely used to inhibit PCa growth but eventually fails in many patients. Androgen receptor and its downstream molecules like microRNAs could be promising therapeutic targets. We aimed to investigate the involvement of miR-21 in PCa tumorigenesis. We found that miR-21 was an unfavorable factor and correlated positively with tumor grade in PCa patients from TCGA database. MiR-21 was more highly expressed in androgen-independent PCa cells than in androgen-dependent PCa cells. Overexpression of miR-21 promoted androgen-dependent and -independent PCa cell proliferation, migration, invasion, and resistance to apoptosis. Furthermore, increased miR-21 expression promoted mouse xenograft growth. We identified nine genes differentially expressed in PCa tumors and normal tissue which could be potential targets of miR-21 by bioinformatic analyses. We demonstrate that miR-21 directly targeted KLF5 and inhibited KLF5 mRNA and protein levels in PCa. STRING and functional enrichment analysis results suggest that GSK3B might be regulated by KLF5. Our findings demonstrate that miR-21 promotes the tumorigenesis of PCa cells by directly targeting KLF5. These biological effects are mediated through upregulation of GSK3B and activation of the AKT signaling pathway.

miRNA-seq analysis of human vertebrae provides insight into the mechanism underlying GIOP

High-throughput sequencing (HTS) was recently applied to detect microRNA (miRNA) regulation in age-related osteoporosis. However, miRNA regulation has not been reported in glucocorticoid-induced osteoporosis (GIOP) patients and the mechanism of GIOP remains elusive. To comprehensively analyze the role of miRNA regulation in GIOP based on human vertebrae and to explore the molecular mechanism, a high-throughput sequencing strategy was employed to identify miRNAs involved in GIOP. Twenty-six patients undergoing spinal surgery were included in this study. Six vertebral samples were selected for miRNA sequencing (miRNA-seq) analysis and 26 vertebral samples were verified by qRT-PCR. Bioinformatics was utilized for target prediction, to investigate the regulation of miRNA-mRNA networks, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Six significantly up-regulated miRNAs (including one novel miRNA) and three significantly down-regulated miRNAs were verified via miRNA-seq and verified in the vertebrae of GIOP patients. Up-regulated miRNAs included hsa-miR-214-5p, hsa-miR-10b-5p, hsa-miR-21-5p, hsa-miR-451a, hsa-miR-186-5p, and hsa-miR-novel-chr3_49,413 while down-regulated miRNAs included hsa-let-7f-5p, hsa-let-7a-5p, and hsa-miR-27a-3p. Bioinformatics analysis revealed 5983 and 23,463 predicted targets in the up-regulated and down-regulated miRNAs respectively, using the miRanda, miRBase and TargetScan databases. The target genes of these significantly altered miRNAs were enriched to 1939 GO terms and 84 KEGG pathways. GO terms revealed that up-regulated targets were most enriched in actin filament-based processes (BP), anchoring junction (CC), and cytoskeletal protein binding (MF). Conversely, the down-regulated targets were mostly enriched in multicellular organismal development (BP), intracellular membrane-bounded organelles (CC), and protein binding (MF). Top-10 pathway analysis revealed that the differentially expressed miRNAs in GIOP were closely related to bone metabolism-related pathways such as FoxO, PI3K-Akt, MAPK and Notch signaling pathway. These results suggest that significantly altered miRNAs may play an important role in GIOP by targeting mRNA and regulating biological processes and bone metabolism-related pathways such as MAPK, FoxO, PI3K-Akt and Notch signaling, which provides novel insight into the mechanism of GIOP and lays a good foundation for the prevention and treatment of GIOP.

Interplay between microRNAs and Wnt, transforming growth factor-β, and bone morphogenic protein signaling pathways promote osteoblastic differentiation of mesenchymal stem cells

Osteoblasts are terminally differentiated cells with mesenchymal origins, known to possess pivotal roles in sustaining bone microstructure and homeostasis. These cells are implicated in the pathophysiology of various bone disorders, especially osteoporosis. Over the last few decades, strategies to impede bone resorption, principally by bisphosphonates, have been mainstay of treatment of osteoporosis; however, in recent years more attention has been drawn on bone-forming approaches for managing osteoporosis. MicroRNAs (miRNAs) are a broad category of noncoding short sequence RNA fragments that posttranscriptionally regulate the expression of diverse functional and structural genes in a negative manner. An accumulating body of evidence signifies that miRNAs direct mesenchymal stem cells toward osteoblast differentiation and bone formation through bone morphogenic protein, transforming growth factor-β, and Wnt signaling pathways. MiRNAs are regarded as excellent future therapeutic candidates because of their small size and ease of delivery into the cells. Considering their novel therapeutic significance, this review discusses the main miRNAs contributing to the anabolic aspects of bone formation and illustrates their interactions with corresponding signaling pathways involved in osteoblastic differentiation.

miR-505-3p is a repressor of the puberty onset in female mice

Puberty onset is a complex trait regulated by multiple genetic and environmental factors. In this study, we narrowed a puberty related QTL region down to a 1.7 Mb region on chromosome X in female mice and inferred miR-505-3p as the functional gene. We conducted ectopic expression of miR-505-3p in the hypothalamus of prepubertal female mice through lentivirus-mediated orthotopic injection. The impact of miR-505-3p on female puberty was evaluated by the measurement of pubertal/reproduction events and histological analysis. The results showed that female mice with overexpression of miR-505-3p in the hypothalamus manifested later puberty onset timing both in vaginal opening and ovary maturation, followed by weaker fertility lying in the longer interval time between mating and delivery, higher abortion rate and smaller litter size. We also constructed miR-505-3p knockout mice by CRISPR/Cas9 technology. MiR-505-3p knockout female mice showed earlier vaginal opening timing, higher serum gonadotrophin and higher expression of puberty-related gene in the hypothalamus than their wild type littermates. Srsf1 was proved to be the target gene of miR-505-3p that played the major role in this process. The results of RNA Immunoprecipitation-sequencing showed that SRSF1 (or SF2), the protein product of Srsf1 gene, mainly bound to ribosome protein (RP) mRNAs in GT1-7 cells. The collective evidence implied that miR-505-3p/SRSF1/RP could play a role in the sexual maturation regulation of mammals.

Extracellular matrix dynamics during mesenchymal stem cells differentiation

Mesenchymal stem cells (MSCs) are stromal cells that display self-renewal and multipotent differentiation capacity. The repertoire of mature cells generated ranges but is not restricted to: fat, bone and cartilage. Their potential importance for both cell therapy and maintenance of in vivo homeostasis is indisputable. Nonetheless, both their in vivo identity and use in cell therapy remain elusive. A drawback generated by this fact is that little is known about the MSC niche and how it impacts differentiation and homeostasis maintenance. Hence, the roles played by the extracellular matrix (ECM) and its main regulators namely: the Matrix Metalloproteinases (MMPs) and their counteracting inhibitors (TIMPs and RECK) upon stem cells differentiation are only now beginning to be unveiled. Here, we will focus on mesenchymal stem cells and review the main mechanisms involved in adipo, chondro and osteogenesis, discussing how the extracellular matrix can impact not only lineage commitment, but, also, their survival and potentiality. This review critically analyzes recent work in the field in an effort towards a better understanding of the roles of Matrix Metalloproteinases and their inhibitors in the above-cited events.

Mesenchymal stem cell-derived exosomes have altered microRNA profiles and induce osteogenic differentiation depending on the stage of differentiation

Human mesenchymal stem cell (hMSC)-derived exosomes have shown regenerative effects, but their role in osteogenesis and the underlying mechanism are yet to be determined. In this study, we examined the time-course secretion of exosomes by hMSCs during the entire process of osteogenic differentiation. Exosomes derived from hMSCs in various stages of osteogenic differentiation committed homotypic cells to differentiate towards osteogenic lineage, but only exosomes from late stages of osteogenic differentiation induced extracellular matrix mineralisation. Exosomes from expansion and early and late stages of osteogenic differentiation were internalised by a subpopulation of hMSCs. MicroRNA profiling revealed a set of differentially expressed exosomal microRNAs from the late stage of osteogenic differentiation, which were osteogenesis related. Target prediction demonstrated that these microRNAs enriched pathways involved in regulation of osteogenic differentiation and general mechanisms how exosomes exert their functions, such as "Wnt signalling pathway" and "endocytosis". Taken together, the results show that MSCs secrete exosomes with different biological properties depending on differentiation stage of their parent cells. The exosomal cargo transferred from MSCs in the late stage of differentiation induces osteogenic differentiation and mineralisation. Moreover, it is suggested that the regulatory effect on osteogenesis by exosomes is at least partly exerted by exosomal microRNA.

Reduced miR-144-3p expression in serum and bone mediates osteoporosis pathogenesis by targeting RANK

Osteoblasts and osteoclasts are responsible for the formation and resorption of bone, respectively. An imbalance between these two processes results in a disease called osteoporosis, in which a decreased level of bone strength increases the risk of a bone fracture. MicroRNAs (miRNAs) are small non-coding RNA molecules of 18-25 nucleotides that have been previously shown to control bone metabolism by regulating osteoblast and osteoclast differentiation. In this study, we detected the expression pattern of 10 miRNAs in serum samples from patients with osteoporosis, and identified the altered expression of 6 miRNAs by comparison with patients without osteoporosis. We selected miR-144-3p for further investigation, and showed that it regulates osteoclastogenesis by targeting RANK, and that it is conserved amongst vertebrates. Disrupted expression of miR-144-3p in CD14+ peripheral blood mononuclear cells changed TRAP activity and the osteoclast-specific genes TRAP, cathepsin K (CTSK), and NFATC. TRAP staining, CCK-8, and flow cytometry analyses revealed that miR-144-3p also affects osteoclast formation, proliferation, and apoptosis. Together, these results indicate that miR-144-3p critically mediates bone homeostasis, and thus, represents a promising novel therapeutic candidate for the treatment of this disease.

The synergistic effect of strontium-substituted hydroxyapatite and microRNA-21 on improving bone remodeling and osseointegration

Surgical failure, mainly caused by loosening implants, causes great mental and physical trauma to patients.

Mesenchymal stem cells deliver exogenous miR-21 via exosomes to inhibit nucleus pulposus cell apoptosis and reduce intervertebral disc degeneration

Although mesenchymal stem cells (MSCs) transplantation into the IVD (intervertebral disc) may be beneficial in inhibiting apoptosis of nucleus pulposus cells (NPCs) and alleviating IVD degeneration, the underlying mechanism of this therapeutic process has not been fully explained. The purpose of this study was to explore the protective effect of MSC‐derived exosomes (MSC‐exosomes) on NPC apoptosis and IVD degeneration and investigate the regulatory effect of miRNAs in MSC‐exosomes and associated mechanisms for NPC apoptosis. MSC‐exosomes were isolated from MSC medium, and its anti‐apoptotic effect was assessed in a cell and rat model. The down‐regulated miRNAs in apoptotic NPCs were identified, and their contents in MSC‐exosomes were detected. The target genes of eligible miRNAs and possible downstream pathway were investigated. Purified MSC‐exosomes were taken up by NPCs and suppressed NPC apoptosis. The levels of miR‐21 were down‐regulated in apoptotic NPCs while MSC‐exosomes were enriched in miR‐21. The exosomal miR‐21 could be transferred into NPCs and alleviated TNF‐α induced NPC apoptosis by targeting phosphatase and tensin homolog (PTEN) through phosphatidylinositol 3‐kinase (PI3K)‐Akt pathway. Intradiscal injection of MSC‐exosomes alleviated the NPC apoptosis and IVD degeneration in the rat model. In conclusion, MSC‐derived exosomes prevent NPCs from apoptotic process and alleviate IVD degeneration, at least partly, via miR‐21 contained in exosomes. Exosomal miR‐21 restrains PTEN and thus activates PI3K/Akt pathway in apoptotic NPCs. Our work confers a promising therapeutic strategy for IVD degeneration.

miR-365 Ameliorates Dexamethasone-Induced Suppression of Osteogenesis in MC3T3-E1 Cells by Targeting HDAC4

Glucocorticoid administration is the leading cause of secondary osteoporosis. In this study, we tested the hypotheses that histone deacetylase 4 (HDAC4) is associated with glucocorticoid-induced bone loss and that HDAC4 dependent bone loss can be ameliorated by miRNA-365. Our previous studies showed that miR-365 mediates mechanical stimulation of chondrocyte proliferation and differentiation by targeting HDAC4. However, it is not clear whether miR-365 has an effect on glucocorticoid-induced osteoporosis. We have shown that, in MC3T3-E1 osteoblasts, dexamethasone (DEX) treatment decreased the expression of miR-365, which is accompanied by the decrease of cell viability in a dose-dependent manner. Transfection of miR-365 ameliorated DEX-induced inhibition of MC3T3-E1 cell viability and alkaline phosphatase activity, and attenuated the suppressive effect of DEX on runt-related transcription factor 2 (Runx2), osteopontin (OPN), and collagen 1a1 (Col1a1) osteogenic gene expression. In addition, miR-365 decreased the expression of HDAC4 mRNA and protein by direct targeting the 3′-untranslated regions (3′-UTR) of HDAC4 mRNA in osteoblasts. MiR-365 increased Runx2 expression and such stimulatory effect could be reversed by HDAC4 over-expression in osteoblasts. Collectively, our findings indicate that miR-365 ameliorates DEX-induced suppression of cell viability and osteogenesis by regulating the expression of HDAC4 in osteoblasts, suggesting miR-365 might be a novel therapeutic agent for treatment of glucocorticoid-induced osteoporosis.

miR-21 deficiency inhibits osteoclast function and prevents bone loss in mice

MicroRNAs emerge as critical post-transcriptional regulators in bone metabolism. We have previously reported in vitro that miR-21 promotes osteogenesis, while studies have also revealed miR-21 as a regulator of osteoclastogenesis and a promoter of osteoclast differentiation in vitro. However, in vivo data are still lacking in identifying skeletal function of miR-21, particularly its effects on osteoporosis. Here, using miR-21 knockout (miR-21^-/-) mice, we investigated effects of miR-21 on bone development, bone remodeling and bone loss. Unexpectedly, miR-21^-/- mice demonstrated normal skeletal phenotype in development and maintained osteoblastogenesis in vivo. Besides, miR-21^-/- mice showed increased receptor activator of nuclear factor κB ligand (RANKL) and decreased osteoprotegerin (OPG) through miR-21 targeting Sprouty 1 (Spry1). Nevertheless, interestingly, miR-21 deficiency promoted trabecular bone mass accrual physiologically. Furthermore, in pathological states, the protection of bone mass was prominent in miR-21^-/- mice. These skeletal effects were attributed to inhibition of bone resorption and osteoclast function by miR-21 deficiency through miR-21 targeting programmed cell death 4 (PDCD4), despite the existence of RANKL. As far as we know, this is the first in vivo evidence of a pro-osteoclastic microRNA. Together, these findings clarified function of miR-21 in bone metabolism, particularly uncovering osteo-protective potential of miR-21 inactivation in osteoporosis.

Bioinformatic Studies to Predict MicroRNAs with the Potential of Uncoupling RECK Expression from Epithelial-Mesenchymal Transition in Cancer Cells

RECK is downregulated in many tumors, and forced RECK expression in tumor cells often results in suppression of malignant phenotypes. Recent findings suggest that RECK is upregulated after epithelial-mesenchymal transition (EMT) in normal epithelium-derived cells but not in cancer cells. Since several microRNAs (miRs) are known to target RECK mRNA, we hypothesized that certain miR(s) may be involved in this suppression of RECK upregulation after EMT in cancer cells. To test this hypothesis, we used three approaches: (1) text mining to find miRs relevant to EMT in cancer cells, (2) predicting miR targets using four algorithms, and (3) comparing miR-seq data and RECK mRNA data using a novel non-parametric method. These approaches identified the miR-183-96-182 cluster as a strong candidate. We also looked for transcription factors and signaling molecules that may promote cancer EMT, miR-183-96-182 upregulation, and RECK downregulation. Here we describe our methods, findings, and a testable hypothesis on how RECK expression could be regulated in cancer cells after EMT.

Effect of miR-19a and miR-21 on the JAK/STAT signaling pathway in the peripheral blood mononuclear cells of patients with systemic juvenile idiopathic arthritis

Overexpression of the components of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway are key factors of the pathogenic mechanisms underlying systematic juvenile idiopathic arthritis (SJIA). The present study aimed to investigate the association between microRNA (miR)-19a, miR-21 and the JAK/STAT signaling pathway. A total of 20 patients with SJIA were included in the study, and peripheral blood mononuclear cells (PBMCs) from 20 normal controls were also collected. RNAiso was used to extract total RNA, and the RNA was then reverse transcribed into cDNA. Primers were designed to detect the mRNA of miR-19a and miR-21, and U6 was set as the internal parameter. In addition, the mRNA of STAT3, suppressor of cytokine signaling 3 (SOCS3), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) was detected, and β-actin was set as the internal parameter. Reverse transcription-quantitative polymerase chain reaction was performed to detect the expression levels of these proteins in patients with SJIA and control subjects, and non-parametric tests were used to analyze the statistical differences in 2^-ΔΔCq between the two groups. The expression levels of miR-19a and miR-21 were significantly lower in the SJIA group compared with the control group (P<0.05). SOCS3, TNF-α and STAT3 were shown to be the target genes of miR-19a and miR-21, as determined by Targetscan. The expression levels of STAT3, SOCS3, TNF-α and IL-6 mRNA were significantly higher compared with those of the control group (P<0.05). In the PBMCs of sthe patients with SJIA, miR-19a and miR-21 expression levels were lower compared with those of the control group, and the JAK/STAT signaling pathway was activated, which indicated that miR-19a and miR-21 may participate in the activation of the JAK/STAT signaling pathway.

Prognostic value of microRNA-21 in pancreatic ductal adenocarcinoma: a meta-analysis

BACKGROUND

Recently, microRNA-21 (miR-21) has been reported to be associated with prognosis of pancreatic ductal adenocarcinoma (PDAC). The present studies aimed to evaluate the prognostic value of miR-21 for PDAC with meta-analysis.

METHODS

A systematic search in the PubMed and other databases was conducted to identify eligible studies. The pooled hazard ratios (HRs) with 95% confidence interval (CI) were calculated. The meta-analysis was conducted using the STATA 12.0 software.

RESULTS

A total of 12 articles (13 studies) which included 963 cases were selected for the meta-analysis. Elevated miR-21 expression was significantly predictive of poor overall survival (HR = 2.05, 95% CI 1.71-2.46, P < 0.001). In the subgroup analyses, similar results were observed in Asian (HR = 2.09, 95% CI 1.62-2.71, P < 0.001) and Caucasian (HR = 2.36, 95% CI 1.53-3.65, P < 0.001); in tissue sample (HR = 2.14, 95% CI 1.73-2.65, P < 0.001) and serum sample (HR = 1.84, 95% CI 1.30-2.60, P = 0.001); with quantitative real-time polymerase chain reaction assay method (HR = 2.31, 95% CI 1.86-2.86, P < 0.001); and in patients receiving adjuvant chemotherapy (HR = 2.37, 95% CI 1.88-3.00, P < 0.001). The association between miR-21 expression level and lymph node metastasis was statistically significant (OR = 1.45, 95% CI 1.02-2.06, P = 0.038). However, no significant relationship between miR-21 expression level and sex or vascular invasion or neural infiltration was observed (P > 0.05).

CONCLUSIONS

Our meta-analysis indicated that elevated miR-21 expression level can predict poor prognosis in patients with PDAC.

Small molecules targeting microRNA for cancer therapy: Promises and obstacles

Aberrant expression of miRNAs is critically implicated in cancer initiation and progression. Therapeutic approaches focused on regulating miRNAs are therefore a promising approach for treating cancer. Antisense oligonucleotides, miRNA sponges, and CRISPR/Cas9 genome editing systems are being investigated as tools for regulating miRNAs. Despite the accruing insights in the use of these tools, delivery concerns have mitigated clinical application of such systems. In contrast, little attention has been given to the potential of small molecules to modulate miRNA expression for cancer therapy. In these years, many researches proved that small molecules targeting cancer-related miRNAs might have greater potential for cancer treatment. Small molecules targeting cancer related miRNAs showed significantly promising results in different cancer models. However, there are still several obstacles hindering the progress and clinical application in this area. This review discusses the development, mechanisms and application of small molecules for modulating oncogenic miRNAs (oncomiRs). Attention has also been given to screening technologies and perspectives aimed to facilitate clinical translation for small molecule-based miRNA therapeutics.