Assessment of the microRNA system in salt-sensitive hypertension

Panel miRNAs are potential diagnostic markers for chronic kidney diseases: a systematic review and meta-analysis

BACKGROUND

Accurate detection of kidney damage is key to preventing renal failure, and identifying biomarkers is essential for this purpose. We aimed to assess the accuracy of miRNAs as diagnostic tools for chronic kidney disease (CKD).

METHODS

We thoroughly searched five databases (MEDLINE, Web of Science, Embase, Scopus, and CENTRAL) and performed a meta-analysis using R software. We assessed the overall diagnostic potential using the pooled area under the curve (pAUC), sensitivity (SEN), and specificity (SPE) values and the risk of bias by using the QUADAS-2 tool. The study protocol was registered on PROSPERO (CRD42021282785).

RESULTS

We analyzed data from 8351 CKD patients, 2989 healthy individuals, and 4331 people with chronic diseases. Among the single miRNAs, the pooled SEN was 0.82, and the SPE was 0.81 for diabetic nephropathy (DN) vs. diabetes mellitus (DM). The SEN and SPE were 0.91 and 0.89 for DN and healthy controls, respectively. miR-192 was the most frequently reported miRNA in DN patients, with a pAUC of 0.91 and SEN and SPE of 0.89 and 0.89, respectively, compared to those in healthy controls. The panel of miRNAs outperformed the single miRNAs (pAUC of 0.86 vs. 0.79, p < 0.05). The SEN and SPE of the panel miRNAs were 0.89 and 0.73, respectively, for DN vs. DM. In the lupus nephritis (LN) vs. systemic lupus erythematosus (SLE) cohorts, the SEN and SPE were 0.84 and 0.81, respectively. Urinary miRNAs tended to be more effective than blood miRNAs (p = 0.06).

CONCLUSION

MiRNAs show promise as effective diagnostic markers for CKD. The detection of miRNAs in urine and the use of a panel of miRNAs allows more accurate diagnosis.

MicroRNAs in kidney injury and disease

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by degrading or repressing the translation of their target messenger RNAs. As miRNAs are critical regulators of cellular homeostasis, their dysregulation is a crucial component of cell and organ injury. A substantial body of evidence indicates that miRNAs are involved in the pathophysiology of acute kidney injury (AKI), chronic kidney disease and allograft damage. Different subsets of miRNAs are dysregulated during AKI, chronic kidney disease and allograft rejection, which could reflect differences in the physiopathology of these conditions. miRNAs that have been investigated in AKI include miR-21, which has an anti-apoptotic role, and miR-214 and miR-668, which regulate mitochondrial dynamics. Various miRNAs are downregulated in diabetic kidney disease, including the miR-30 family and miR-146a, which protect against inflammation and fibrosis. Other miRNAs such as miR-193 and miR-92a induce podocyte dedifferentiation in glomerulonephritis. In transplantation, miRNAs have been implicated in allograft rejection and injury. Further work is needed to identify and validate miRNAs as biomarkers of graft function and of kidney disease development and progression. Use of combinations of miRNAs together with other molecular markers could potentially improve diagnostic or predictive power and facilitate clinical translation. In addition, targeting specific miRNAs at different stages of disease could be a promising therapeutic strategy.

Role of MicroRNAs and their corresponding ACE2/Apelin signaling pathways in hypertension

Hypertension is controlled via the alteration of microRNAs (miRNAs), their therapeutic targets angiotensin II type I receptor (AT1R) and cross talk of signaling pathways. The stimulation of the Ang II/AT1R pathway by deregulation of miRNAs, has also been linked to cardiac remodeling as well as the pathophysiology of high blood pressure. As miRNAs have been associated to ACE2/Apelin and Mitogen-activated protein kinases (MAPK) signaling, it has revealed an utmost protective impact over hypertension and cardiovascular system. The ACE2-coupled intermodulation between RAAS, Apelin system, MAPK signaling pathways, and miRNAs reveal the practicalities of high blood pressure. The research of miRNAs may ultimately lead to the expansion of an innovative treatment strategy for hypertension, which indicates the need to explore them further at the molecular level. Therefore, here we have focused on the mechanistic importance of miRNAs in hypertension, ACE2/Apelin signaling as well as their biological functions, with a focus on interplay and crosstalk between ACE2/Apelin signaling, miRNAs, and hypertension, and the progress in miRNA-based diagnostic techniques with the goal of facilitating the development of new hypertension-controlling therapeutics.

Impact of Nutritional Epigenetics in Essential Hypertension: Targeting microRNAs in the Gut-Liver Axis

PURPOSE OF REVIEW

To review the current knowledge on interactions between dietary factors and microRNAs (miRNAs) in essential hypertension (EH) pathogenesis.

RECENT FINDINGS

There exists an integration of maintenance signals generated by genetic, epigenetic, immune, and environmental (e.g., dietary) factors that work to sustain balance in the gut-liver axis. It is well established that an imbalance in this complex, intertwined system substantially increases the risk for EH. As such, pertinent research has been taken to decipher how each signal operates in isolation and together in EH progression. Recent literature indicates that both macro- and micronutrients interrupt regulatory miRNA expressions and thus, alter multiple cellular processes that contribute to EH and its comorbidities. We highlight how carbohydrates, lipids, proteins, salt, and potassium modify miRNA signatures during EH. The disruption in miRNA expression can negatively impact communication systems such as over activating the renin-angiotensin-aldosterone system, modulating the vascular smooth muscle cell phenotype, and promoting angiogenesis to favor EH. We also delineate the prognostic value of miRNAs in EH and discuss the pros and cons of surgical vs dietary prophylactic approaches in EH prevention. We propose that dietary-dependent perturbation of the miRNA profile is one mechanism within the gut-liver axis that dictates EH development.

Involvement of miR-200b-PKCα signalling in pulmonary hypertension in cor pulmonale model

The right ventricle (RV) enlargement and pulmonary fibrosis are involved in cor pulmonale. The role of miR-200b in cor pulmonale is less well understood. This study was designed to evaluate the regulatory roles of miR-200b in cor pulmonale. Cor pulmonary mouse model was built via monocrotaline injection of monocrotaline (MCT). The expression of miR-200b in the lungs, RV and left ventricle (LV) are using real-time polymerase chain reaction. The transthoracic echocardiography was employed to determine the effects of miR-200b mimics and Gö6976 injection on MCT mice. The protein levels of protein kinase C α (PKCα), collagen, and fibronectin in the lung, RV, and LV in the mice with and without miR-200b mimics and Gö6976 injection were evaluated using western blot. The expression of miR-200b decreased in MCT mice, while there was no difference in LV. Both the miR-200b mimics and Gö6976 injection reversed the muscularization in the pulmonary artery, reversed RV hypertrophy, reduced RV systolic pressure, wall thickness and pulmonary fibrosis. The injection of miR-200b can reduce the PKCα expression in the lung, RV, and LV. This study confirmed the down-regulation of miR-200b in cor pulmonale. The reverse effects of miR-200b in the present study may provide a potential tool for cor pulmonary treatment.

Correlation Between Single-Nucleotide Polymorphisms Within miR-30a and Related Target Genes and Risk or Prognosis of Nephrotic Syndrome

This study was aimed to figure out the association of single-nucleotide polymorphisms (SNPs) within miR-30a and its downstream molecules (i.e., Notch1, Snail1, p53, CD73, and TET1) with susceptibility to and prognosis of nephrotic syndrome (NS). In the aggregate, 265 patients and 281 healthy controls were gathered, and related laboratory indicators were examined. The miR-30a, Notch1, Snail1, TET1, p53, and CD73 expressions were also evaluated by quantitative real-time polymerase chain reaction (qRT-PCR), immunohistochemistry, or enzyme-linked immunosorbent assay. Besides, the SNPs were genotyped by RT-PCR with aid of ABI-PRISM^™ 377 DNA sequencing instrument. As a result, the NS patients were correlated with remarkably higher 24-h protein excretion, random urine protein/creatinine (UPCR), and serum creatinine, along with lower estimated glomerular filtration rate and serum albumin, when compared with normal subjects (p < 0.05). Furthermore, significant correlations were present between miR-30a expression and the expressions of Notch1 (r_s = -0.350), p53 (r_s = -0.339), CD73 (r_s = -0.300), TET1 (r_s = -0.249), and Snail1 (r_s = -0.829) (all p < 0.05). The SNPs of miR-30a [i.e., rs2222722 (C>T)], Notch1 [i.e., rs3124599 (G>A), rs3124591 (C>T), and rs139994842 (G>A)], Snail1 [i.e., rs6020178 (T>C)], p53 [i.e., rs1042522 (C>G)], and CD73 [i.e., rs9444348 (G>A) and rs4431401 (T>C)] were significantly correlated with both differed NS risk and altered hormone sensitivity to NS (all p < 0.05). Moreover, haplotype AC of CD73 and haplotype ATG of Notch1 were the helpful factors against NS (p < 0.05), yet haplotype GT of CD73 functioned oppositely (p < 0.05). The haplotype AT of CD73 was beneficial to the NS patients for that the carriers could be treated with hormones without severe complications (p < 0.05). Conclusively, the SNPs situated within miR-30a and its downstream molecules (i.e., Notch1, Snail1, p53, CD73, and TET1) could become the promising biomarkers for both NS diagnosis and prediction of NS prognosis.

Placental Stem Villus Arterial Remodeling Associated with Reduced Hydrogen Sulfide Synthesis Contributes to Human Fetal Growth Restriction

Intrauterine fetal growth restriction (IUGR) is often associated with compromised umbilical arterial flow, indicating increased placental vascular resistance. Oxidative stress is causatively implicated. Hydrogen sulfide maintains differentiated smooth muscle in vascular beds, and its synthetic enzyme cystathionine-γ-lyase (CSE) is down-regulated in growth-restricted placentas. We hypothesized that remodeling of resistance arteries in stem villi contributes to IUGR by compromising umbilical blood flow via oxidative stress, reducing hydrogen sulfide signaling. Stem villus arteries in human IUGR placentas displaying absent or reversed end-diastolic flow contained reduced myosin heavy chain, smooth muscle actin, and desmin, and increased markers of dedifferentiation, cellular retinol-binding protein 1, and matrix metalloproteinase 2, compared to term and preterm controls. Wall thickness/lumen ratio was increased, lumen diameter decreased, but wall thickness remained unchanged in IUGR placentas. CSE correlated positively with myosin heavy chain, smooth muscle actin, and desmin. Birth weight correlated positively with CSE, myosin heavy chain, smooth muscle actin, and desmin, and negatively with cellular retinol-binding protein 1 and matrix metalloproteinase 2. These findings could be recapitulated in vitro by subjecting stem villus artery explants to hypoxia-reoxygenation, or inhibiting CSE. Treatment with a hydrogen sulfide donor, diallyl trisulfide, prevented these changes. IUGR is associated with vascular remodeling of the stem villus arteries. Oxidative stress results in reduction of placental CSE activity, decreased hydrogen sulfide production, and smooth muscle cell dedifferentiation in vitro. This vascular remodeling is reversible, and hydrogen sulfide donors are likely to improve pregnancy outcomes.

Mini-review: emerging roles of microRNAs in the pathophysiology of renal diseases

MicroRNAs (miRNA) are endogenously produced short noncoding regulatory RNAs that can repress gene expression by posttranscriptional mechanisms. They can therefore influence both normal and pathological conditions in diverse biological systems. Several miRNAs have been detected in kidneys, where they have been found to be crucial for renal development and normal physiological functions as well as significant contributors to the pathogenesis of renal disorders such as diabetic nephropathy, acute kidney injury, lupus nephritis, polycystic kidney disease, and others, due to their effects on key genes involved in these disease processes. miRNAs have also emerged as novel biomarkers in these renal disorders. Due to increasing evidence of their actions in various kidney segments, in this mini-review we discuss the functional significance of altered miRNA expression during the development of renal pathologies and highlight emerging miRNA-based therapeutics and diagnostic strategies for early detection and treatment of kidney diseases.

Mechanisms and therapeutic potential of microRNAs in hypertension

Hypertension is the major risk factor for the development of stroke, coronary artery disease, heart failure and renal disease. The underlying cellular and molecular mechanisms of hypertension are complex and remain largely elusive. MicroRNAs (miRNAs) are short, noncoding RNA fragments of 22-26 nucleotides and regulate protein expression post-transcriptionally by targeting the 3'-untranslated region of mRNA. A growing body of recent research indicates that miRNAs are important in the pathogenesis of arterial hypertension. Herein, we summarize the current knowledge regarding the mechanisms of miRNAs in cardiovascular remodeling, focusing specifically on hypertension. We also review recent progress of the miRNA-based therapeutics including pharmacological and nonpharmacological therapies (such as exercise training) and their potential applications in the management of hypertension.

Triptolide Attenuates Podocyte Injury by Regulating Expression of miRNA-344b-3p and miRNA-30b-3p in Rats with Adriamycin-Induced Nephropathy

Objectives. We investigated the action of triptolide in rats with adriamycin-induced nephropathy and evaluated the possible mechanisms underlying its protective effect against podocyte injury. Methods. In total, 30 healthy male Sprague-Dawley rats were randomized into three groups (normal group, model group, and triptolide group). On days 7, 28, 42, and 56, 24 h urine samples were collected. All rats were sacrificed on day 56, and their blood and renal tissues were collected for determination of biochemical and molecular biological parameters. Expression of miRNAs in the renal cortex was analyzed by a biochip assay and RT-PCR was used to confirm observed differences in miRNA levels. Results. Triptolide decreased proteinuria, improved renal function without apparent adverse effects on the liver, and alleviated renal pathological lesions. Triptolide also elevated the nephrin protein level. Furthermore, levels of miR-344b-3p and miR-30b-3p were elevated in rats with adriamycin-induced nephropathy, while triptolide treatment reversed the increase in the expression of these two miRNAs. Conclusions. These results suggest that triptolide may attenuate podocyte injury in rats with adriamycin-induced nephropathy by regulating expression of miRNA-344b-3p and miRNA-30b-3p.

miR-223: An inflammatory oncomiR enters the cardiovascular field

MicroRNAs (miRNAs) are small, noncoding RNAs of 18-22 nucleotides in length that regulate post-transcriptional expression by base-pairing with target mRNAs. It is now clearly established that miRNAs are involved in most of the cell's physiopathological processes (including carcinogenesis and metabolic disorders). This review focuses on miR-223, which was first described as a modulator of hematopoietic lineage differentiation. We outline the role of miR-223 deregulation in several types of cancers and highlight its inclusion in a newly identified and fast-growing family of miRNAs called oncomiRs. We then look at miR-223's emerging role in inflammatory and metabolic disorders, with a particular focus on muscle diseases, type II diabetes, atherosclerosis and vascular calcification. miR-223 is one of the growing number of RNA biomarkers of various human metabolic diseases and is thus of special interest to both researchers and clinicians in the cardiovascular field.

The regulation and function of microRNAs in kidney diseases

MicroRNAs (miRNA) are endogenous short noncoding RNAs, which regulate virtually all major cellular processes by inhibiting target gene expression. In kidneys, miRNAs have been implicated in renal development, homeostasis, and physiological functions. In addition, miRNAs play important roles in the pathogenesis of various renal diseases, including renal carcinoma, diabetic nephropathy, acute kidney injury, hypertensive nephropathy, polycystic kidney disease, and others. Furthermore, miRNAs may have great values as biomarkers in different kidney diseases.

Reduced cystathionine γ-lyase and increased miR-21 expression are associated with increased vascular resistance in growth-restricted pregnancies: hydrogen sulfide as a placental vasodilator

Increased vascular impedance in the fetoplacental circulation is associated with fetal hypoxia and growth restriction. We sought to investigate the role of hydrogen sulfide (H₂S) in regulating vasomotor tone in the fetoplacental vasculature. H₂S is produced endogenously by catalytic activity of cystathionine β-synthase and cystathionine γ-lyase (CSE). Immunohistochemical analysis localized CSE to smooth muscle cells encircling arteries in stem villi. Immunoreactivity was reduced in placentas from pregnancies with severe early-onset growth-restriction and preeclampsia displaying abnormal umbilical artery Doppler waveforms compared with preeclamptic placentas with normal waveforms and controls. These findings were confirmed at the protein and mRNA levels. MicroRNA-21, which negatively regulates CSE expression, was increased in placentas with abnormal Doppler waveforms. Exposure of villus explants to hypoxia-reoxygenation significantly reduced CSE protein and mRNA and increased microRNA-21 expression. No changes were observed in cystathionine β-synthase expression, immunolocalized principally to the trophoblast, in pathologic placentas or in vitro. Finally, perfusion of normal placentas with an H₂S donor, after preconstriction with a thromboxane mimetic, resulted in dose-dependent vasorelaxation. Glibenclamide and N^G-nitro-l-arginine methyl ester partially blocked the effect, indicating that H₂S acts through ATP-sensitive K⁺ channels and nitric oxide synthesis. These results demonstrate that H₂S is a powerful vasodilator of the placental vasculature and that expression of CSE is reduced in placentas associated with increased vascular resistance.

MicroRNAs as newer therapeutic targets: A big hope from a tiny player

MicroRNAs (miRNAs) are a novel group of universally present small noncoding endogenous RNAs that regulate gene expression and protein coding by base pairing with the 3’ untranslated region (UTR) of target mRNAs. So they have been associated with several physiological processes and play an important role in the manifestation of diverse diseases. miRNAs expression is associated with the normal and diverse pathophysiological state including cardiac hypertrophy, neurodegenerative diseases, diabetes and its complication, and cancer because individual miRNAs are associated with the regulation of the expression of multiple target genes. Modulating the expression of a single miRNA can influence an entire gene network and thereby modify complex disease phenotypes. From recent studies, it has been confirmed that miRNA has a potential physiological role in various body systems. But in some specialized condition over expression of miRNA within the cytoplasm also leads to some pathological condition in the body. Here, we summarize the roles of miRNAs in various pathological conditions and consider the advantages and potential challenges of miRNA-based therapeutic approaches compared to conventional drug-based therapies.

MicroRNAs Are Involved in End-Organ Damage During Hypertension

Even in the new millennium, arterial hypertension remains a serious condition, with considerable morbidity and mortality worldwide. Crucial in managing the disease is not only lowering arterial blood pressure but also preventing or treating the typical end-organ damage caused by long-lasting and inadequately treated hypertension. In the past decade, it has been shown that microRNAs (miRs) are involved in several hypertension-related pathologies, such as cardiac hypertrophy and fibrosis, hypertensive heart failure, renal fibrosis, kidney failure, and, to a lesser extent, eye disease and hemorrhagic stroke. Whereas others extensively reviewed the role of miRs in atherosclerosis and vascular disease, this review focuses on their role in target organ damage during arterial hypertension. We emphasize the involvement of miRs in pathological end-organ remodeling processes and try to demonstrate some common miR signatures in distinct end organs. Hence, we aimed to provide proof of arterial hypertension being a systemic disease, similar to diabetes mellitus or metabolic syndrome. Furthermore, miRs that act on one particular process in different end organs are interesting therapeutic targets. Some future perspectives in miR research are highlighted with respect to novel therapeutic strategies in the cardiovascular field.

MicroRNA-21 represses human cystathionine gamma-lyase expression by targeting at specificity protein-1 in smooth muscle cells

Cystathionine gamma-lyase (CSE) is the major H(2)S-generating enzyme in vascular smooth muscle cells (SMCs). CSE/H(2)S system contributes to the maintenance of SMC phenotype, and transcript factor specificity protein-1 (SP1) is a critical regulator of CSE expression during SMC differentiation. The involvements of microRNA-21 (miR-21) in cardiovascular pathophysiology have been known, however miR-21 regulation of CSE and SP1 as well as SMC phenotype are uncertain. Using quantitative real-time PCR, we demonstrated that the expression of miR-21 was upregulated in dedifferentiated human aorta SMCs (HASMCs) and injured mouse carotid arteries. To determine the potential roles of miR-21 in SP1-mediated CSE gene expression and SMC phenotypic change, we showed that miR-21 expression was upregulated by miR-21 precursor. Interestingly, miR-21 overexpression significantly repressed the protein expressions of both CSE and SP1, inhibited H(2)S production, stimulated SMC proliferation, and reduced SMC differentiation marker gene expression, respectively. The mRNA expression of CSE but not SP1 was inhibited by miR-21 precursor. Blockage of SP1 binding by mithramycin or inhibition of CSE activity by DL-propargylglycine did not change miR-21 expression. We further demonstrated that miR-21 repressed SP1 protein expression by directly targeting at SP1 3' untranslational regions, which in turn downregulated CSE mRNA expression and stimulated SMC proliferation. Take together, these results suggest that miR-21 participates in CSE/H(2)S-mediated-SMC differentiation by targeting SP1.

MicroRNAs in hypertension: mechanisms and therapeutic targets

Hypertension is a complex, multifactorial disease, and its development is determined by a combination of genetic susceptibility and environmental factors. Several mechanisms have been implicated in the pathogenesis of hypertension: increased activity of the sympathetic nervous system, overactivation of the renin-angiotensin aldosterone system (RAAS), dysfunction of vascular endothelium, impaired platelet function, thrombogenesis, vascular smooth muscle and cardiac hypertrophy, and altered angiogenesis. MicroRNAs are short, noncoding nucleotides regulating target messenger RNAs at the post-transcriptional level. MicroRNAs are involved in virtually all biologic processes, including cellular proliferation, apoptosis, and differentiation. Thus, microRNA deregulation often results in impaired cellular function and disease development, so microRNAs have potential therapeutic relevance. Many aspects of the development of essential hypertension at the molecular level are still unknown. The elucidation of these processes regulated by microRNAs and the identification of novel microRNA targets in the pathogenesis of hypertension is a highly valuable and exciting strategy that may eventually led to the development of novel treatment approaches for hypertension. This article reviews the potential role of microRNAs in the mechanisms associated with the development and consequences of hypertension and discusses advances in microRNA-based approaches that may be important in treating hypertension.

Beyond genome-wide association studies: new strategies for identifying genetic determinants of hypertension

Genetic linkage and association methods have long been the most important tools for gene identification in humans. These approaches can either be hypothesis-based (i.e., candidate-gene studies) or hypothesis-free (i.e., genome-wide studies). The first part of this review offers an overview of the latest successes in gene finding for blood pressure (BP) and essential hypertension using these DNA sequence-based discovery techniques. We further emphasize the importance of post-genome-wide association study (post-GWAS) analysis, which aims to prioritize genetic variants for functional follow-up. Whole-genome next-generation sequencing will eventually be necessary to provide a more comprehensive picture of all DNA variants affecting BP and hypertension. The second part of this review discusses promising novel approaches that move beyond the DNA sequence and aim to discover BP genes that are differentially regulated by epigenetic mechanisms, including microRNAs, histone modification, and methylation.

Cardiac insulin resistance and microRNA modulators

Cardiac insulin resistance is a metabolic and functional disorder that is often associated with obesity and/or the cardiorenal metabolic syndrome (CRS), and this disorder may be accentuated by chronic alcohol consumption. In conditions of over-nutrition, increased insulin (INS) and angiotensin II (Ang II) activate mammalian target for rapamycin (mTOR)/p70 S6 kinase (S6K1) signaling, whereas chronic alcohol consumption inhibits mTOR/S6K1 activation in cardiac tissue. Although excessive activation of mTOR/S6K1 induces cardiac INS resistance via serine phosphorylation of INS receptor substrates (IRS-1/2), it also renders cardioprotection via increased Ang II receptor 2 (AT2R) upregulation and adaptive hypertrophy. In the INS-resistant and hyperinsulinemic Zucker obese (ZO) rat, a rodent model for CRS, activation of mTOR/S6K1signaling in cardiac tissue is regulated by protective feed-back mechanisms involving mTOR↔AT2R signaling loop and profile changes of microRNA that target S6K1. Such regulation may play a role in attenuating progressive heart failure. Conversely, alcohol-mediated inhibition of mTOR/S6K1, down-regulation of INS receptor and growth-inhibitory mir-200 family, and upregulation of mir-212 that promotes fetal gene program may exacerbate CRS-related cardiomyopathy.

Detecting microRNA activity from gene expression data

Background

MicroRNAs (miRNAs) are non-coding RNAs that regulate gene expression by binding to the messenger RNA (mRNA) of protein coding genes. They control gene expression by either inhibiting translation or inducing mRNA degradation. A number of computational techniques have been developed to identify the targets of miRNAs. In this study we used predicted miRNA-gene interactions to analyse mRNA gene expression microarray data to predict miRNAs associated with particular diseases or conditions.

Results

Here we combine correspondence analysis, between group analysis and co-inertia analysis (CIA) to determine which miRNAs are associated with differences in gene expression levels in microarray data sets. Using a database of miRNA target predictions from TargetScan, TargetScanS, PicTar4way PicTar5way, and miRanda and combining these data with gene expression levels from sets of microarrays, this method produces a ranked list of miRNAs associated with a specified split in samples. We applied this to three different microarray datasets, a papillary thyroid carcinoma dataset, an in-house dataset of lipopolysaccharide treated mouse macrophages, and a multi-tissue dataset. In each case we were able to identified miRNAs of biological importance.

Conclusions

We describe a technique to integrate gene expression data and miRNA target predictions from multiple sources.

Renal medullary microRNAs in Dahl salt-sensitive rats: miR-29b regulates several collagens and related genes

MicroRNAs are endogenous repressors of gene expression. We examined microRNAs in the renal medulla of Dahl salt-sensitive rats and consomic SS-13(BN) rats. Salt-induced hypertension and renal injury in Dahl salt-sensitive rats, particularly medullary interstitial fibrosis, have been shown previously to be substantially attenuated in SS-13(BN) rats. Of 377 microRNAs examined, 5 were found to be differentially expressed between Dahl salt-sensitive rats and consomic SS-13(BN) rats receiving a high-salt diet. Real-time PCR analysis demonstrated that high-salt diets induced substantial upregulation of miR-29b in the renal medulla of SS-13(BN) rats but not in SS rats. miR-29b was predicted to regulate 20 collagen genes, matrix metalloproteinase 2 (Mmp2), integrin beta1 (Itgb1), and other genes related to the extracellular matrix. Expression of 9 collagen genes and Mmp2 was upregulated by a high-salt diet in the renal medulla of SS rats, but not in SS-13(BN) rats, an expression pattern opposite to miR-29b. Knockdown of miR-29b in the kidneys of SS-13(BN) rats resulted in upregulation of several collagen genes. miR-29b reduced expression levels of several collagen genes and Itgb1 in cultured rat renal medullary epithelial cells. Moreover, miR-29b suppressed the activity of luciferase when the reporter gene was linked to a 3'-untranslated segment of collagen genes Col1a1, Col3a1, Col4a1, Col5a1, Col5a2, Col5a3, Col7a1, Col8a1, Mmp2, or Itgb1 but not Col12a1. The result demonstrated broad effects of miR-29b on a large number of collagens and genes related to the extracellular matrix and suggested involvement of miR-29b in the protection from renal medullary injury in SS-13(BN) rats.

The miR-30 miRNA family regulates Xenopus pronephros development and targets the transcription factor Xlim1/Lhx1

MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression at the post-transcriptional level. They are involved in diverse biological processes, such as development, differentiation, cell proliferation and apoptosis. To study the role of miRNAs during pronephric kidney development of Xenopus, global miRNA biogenesis was eliminated by knockdown of two key components: Dicer and Dgcr8. These embryos developed a range of kidney defects, including edema formation, delayed renal epithelial differentiation and abnormal patterning. To identify a causative miRNA, mouse and frog kidneys were screened for putative candidates. Among these, the miR-30 family showed the most prominent kidney-restricted expression. Moreover, knockdown of miR-30a-5p phenocopied most of the pronephric defects observed upon global inhibition of miRNA biogenesis. Molecular analyses revealed that miR-30 regulates the LIM-class homeobox factor Xlim1/Lhx1, a major transcriptional regulator of kidney development. miR-30 targeted Xlim1/Lhx1 via two previously unrecognized binding sites in its 3'UTR and thereby restricted its activity. During kidney development, Xlim1/Lhx1 is required in the early stages, but is downregulated subsequently. However, in the absence of miR-30 activity, Xlim1/Lhx1 is maintained at high levels and, therefore, may contribute to the delayed terminal differentiation of the amphibian pronephros.

MicroRNAs miR-124 and miR-135a are potential regulators of the mineralocorticoid receptor gene (NR3C2) expression

MicroRNAs (miRNAs) comprise a post-transcriptional layer of gene regulation shown to be involved in diverse physiological processes. We aimed to study whether regulatory networks that determine susceptibility to hypertension may involve a miRNA component. Screening of loci, involved in renal water–salt balance regulation, highlighted the mineralocorticoid receptor gene NR3C2 as a potential target for several miRNAs. A luciferase assay demonstrated that miR-124 and miR-135a suppress NR3C2 3′UTR reporter construct activity 1.5- and 2.2-fold, respectively. As the tested miRNAs did not reduce the levels of target mRNA, we suggest that the binding of miR-124 and miR-135a to NR3C2 3′UTR contributes to the translational, not transcriptional regulation of the gene. Co-expression of two different miRNAs did not increase the repression of the reporter gene, indicating no additive or synergistic effects between the tested miRNAs.

Our results demonstrate that by repressing the mineralocorticoid receptor gene NR3C2, miR-124 and miR-135a could participate in the regulation of renin–angiotensin–aldosterone system and thereby might be involved in blood pressure regulation.

Plasma miR-208 as a biomarker of myocardial injury

BACKGROUND

MicroRNAs (miRNAs) are endogenous small RNAs of 21-25 nucleotides that can pair with sites in 3' untranslated regions in mRNAs of protein-coding genes to downregulate their expression. Recently, circulating miRNAs have been reported as promising biomarkers for various pathologic conditions. We assessed the hypothesis that miRNAs may leak into the circulating blood from injured cells and thereby serve as biomarkers for identifying the injured cell type.

METHODS

We used isoproterenol-induced myocardial injury in rats as a model and miRNA array analyses to identify candidate miRNAs specifically produced in the ventricles of the heart. Individual miRNA concentrations were measured by real-time reverse-transcription PCR. Plasma cardiac troponin I (cTnI) concentrations were measured with an ELISA.

RESULTS

Array analyses revealed miR-208 to be produced exclusively in the heart, and we selected this miRNA as a possible biomarker of myocardial injury. Plasma concentrations of miR-208 increased significantly (P < 0.0001) after isoproterenol-induced myocardial injury and showed a similar time course to the concentration of cTnI, a classic biomarker of myocardial injury.

CONCLUSIONS

The plasma concentration of miR-208 may be a useful indicator of myocardial injury. Our results suggest that profiling of circulating miRNAs may help identify promising biomarkers of various pathologic conditions.

MicroRNA expression pattern in different stages of nonalcoholic fatty liver disease

BACKGROUND/AIMS

To explore the unique microRNA expression pattern of nonalcoholic fatty liver disease in a rat model, and search for targets of certain dysregulated microRNAs.

METHODS

Microarray and stem-loop RT-PCR were utilized to detect dysregulated microRNAs in a rat model. Significance Analysis of Microarray, Prediction Analysis of Microarray and clustering analysis were implemented to calculate significantly aberrantly expressed microRNAs. TargetScan, miRanda and PicTar were jointly used to predict targets of microRNAs.

RESULTS

Confirmed by Significance Analysis of Microarray and predicted by Prediction Analysis of Microarray, portfolios of 27 and 21 microRNAs were selected as an accurate molecular signature in distinguishing steatosis and steatohepatitis from normal rat liver. Besides, a panel of microRNA-target pairs that may be involved in lipid and glucose metabolism and inflammation process was delineated.

CONCLUSION

This is by far the first report on the dysregulated microRNAs expression pattern in nonalcoholic fatty liver disease. The successful differentiation of steatosis and steatohepatitis from normal liver hints to the potential of using lists of dysregulated microRNAs for diagnosis, though many problems need to be solved. Besides, these data will guide further studies of the contribution of microRNAs to the pathogenesis of nonalcoholic fatty liver disease while disease-specific microRNAs might become potential targets for therapeutic intervention.

MicroRNA: a new frontier in kidney and blood pressure research

MicroRNA (miRNA) has emerged rapidly as a major new direction in many fields of research including kidney and blood pressure research. A mammalian genome encodes several hundred miRNAs. These miRNAs potentially regulate the expression of thousands of proteins. miRNA expression profiles differ substantially between the kidney and other organs as well as between kidney regions. miRNAs may be functionally important in models of diabetic nephropathy, podocyte development, and polycystic disease. miRNAs may be involved in the regulation of arterial blood pressure, including possible involvement in genetic elements of hypertension. Studies of miRNAs could generate diagnostic biomarkers for kidney disease and new mechanistic insights into the complex regulatory networks underlying kidney disease and hypertension. Further progress in the understanding of miRNA biogenesis and action and technical improvements for target identification and miRNA manipulation will be important for studying miRNAs in renal function and blood pressure regulation.

MicroRNAs: role in cardiovascular biology and disease

miRNAs (microRNAs) comprise a novel class of endogenous, small, non-coding RNAs that negatively regulate gene expression via degradation or translational inhibition of their target mRNAs. Recent studies have demonstrated that miRNAs are highly expressed in the cardiovascular system. Although we are currently in the initial stages of understanding how this novel class of gene regulators is involved in cardiovascular biological functions, a growing body of exciting evidence suggests that miRNAs are important regulators of cardiovascular cell differentiation, growth, proliferation and apoptosis. Moreover, miRNAs are key modulators of both cardiovascular development and angiogenesis. Consequently, dysregulation of miRNA function may lead to cardiovascular diseases. Indeed, several recent reports have demonstrated that miRNAs are aberrantly expressed in diseased hearts and vessels. Modulating these aberrantly expressed miRNAs has significant effects on cardiac hypertrophy, vascular neointimal lesion formation and cardiac arrhythmias. Identifying the roles of miRNAs and their target genes and signalling pathways in cardiovascular disease will be critical for future research. miRNAs may represent a new layer of regulators for cardiovascular biology and a novel class of therapeutic targets for cardiovascular diseases.

Individual mRNA expression profiles reveal the effects of specific microRNAs

BACKGROUND

MicroRNAs (miRNAs) are oligoribonucleotides with an important role in regulation of gene expression at the level of translation. Despite imperfect target complementarity, they can also significantly reduce mRNA levels. The validity of miRNA target gene predictions is difficult to assess at the protein level. We sought, therefore, to determine whether a general lowering of predicted target gene mRNA expression by endogenous miRNAs was detectable within microarray gene expression profiles.

RESULTS

The target gene sets predicted for each miRNA were mapped onto known gene expression data from a range of tissues. Whether considering mean absolute target gene expression, rank sum tests or 'ranked ratios', many miRNAs with significantly reduced target gene expression corresponded to those known to be expressed in the cognate tissue. Expression levels of miRNAs with reduced target mRNA levels were higher than those of miRNAs with no detectable effect on mRNA expression. Analysis of microarray data gathered after artificial perturbation of expression of a specific miRNA confirmed the predicted increase or decrease in influence of the altered miRNA upon mRNA levels. Strongest associations were observed with targets predicted by TargetScan.

CONCLUSION

We have demonstrated that the effect of a miRNA on its target mRNAs' levels can be measured within a single gene expression profile. This emphasizes the extent of this mode of regulation in vivo and confirms that many of the predicted miRNA-mRNA interactions are correct. The success of this approach has revealed the vast potential for extracting information about miRNA function from gene expression profiles.

MicroRNA-target pairs in the rat kidney identified by microRNA microarray, proteomic, and bioinformatic analysis

Mammalian genomes contain several hundred highly conserved genes encoding microRNAs. In silico analysis has predicted that a typical microRNA may regulate the expression of hundreds of target genes, suggesting miRNAs might have broad biological significance. A major challenge is to obtain experimental evidence for predicted microRNA-target pairs. We reasoned that reciprocal expression of a microRNA and a predicted target within a physiological context would support the presence and relevance of a microRNA-target pair. We used microRNA microarray and proteomic techniques to analyze the cortex and the medulla of rat kidneys. Of the 377 microRNAs analyzed, we identified 6 as enriched in the renal cortex and 11 in the renal medulla. From approximately 2100 detectable protein spots in two-dimensional gels, we identified 58 proteins as more abundant in the renal cortex and 72 in the renal medulla. The differential expression of several microRNAs and proteins was verified by real-time PCR and Western blot analyses, respectively. Several pairs of reciprocally expressed microRNAs and proteins were predicted to be microRNA-target pairs by TargetScan, PicTar, or miRanda. Seven pairs were predicted by two algorithms and two pairs by all three algorithms. The identification of reciprocal expression of microRNAs and their computationally predicted targets in the rat kidney provides a unique molecular basis for further exploring the biological role of microRNA. In addition, this study establishes a differential profile of microRNA expression between the renal cortex and the renal medulla and greatly expands the known differential proteome profiles between the two kidney regions.

Cardiac hypertrophy: mechanisms and therapeutic opportunities

Cardiac hypertrophy and heart failure are major causes of morbidity and mortality in Western societies. Many factors have been implicated in cardiac remodeling, including alterations in gene expression in myocytes, cardiomyocytes apoptosis, cytokines and growth factors that influence cardiac dynamics, and deficits in energy metabolism as well as alterations in cardiac extracellular matrix composition. Many therapeutic means have been shown to prevent or reverse cardiac hypertrophy. New concepts for characterizing the pathophysiology of cardiac hypertrophy have been drawn from various aspects, including medical therapy and gene therapy, or use of stem cells for tissue regeneration. In this review, we focus on various types of cardiac hypertrophy, defining the causes of hypertrophy, describing available animal models of hypertrophy, discussing the mechanisms for development of hypertrophy and its transition to heart failure, and presenting the potential use of novel promising therapeutic strategies derived from new advances in basic scientific research.

A micro-RNA signature associated with race, tumor size, and target gene activity in human uterine leiomyomas

Human uterine leiomyomas (ULMs) are the most common neoplasms of women. Many genes are dysregulated in ULMs and some of this dysregulation may be due to abnormal expression of micro-RNAs (miRNAs). In this study, 55 ULMs and matched myometrium were collected from 41 patients for microarray-based global miRNA expression analysis. Of 206 miRNAs examined, 45 miRNAs were significantly up- or down-regulated in ULMs in comparison to the matched myometrium (P < 0.001). The top five dysregulated miRNAs in ULMs are the let-7 family, miR-21, miR-23b, miR-29b, and miR-197. Four polycistronic clusters of miRNAs were either up- or down-regulated, but not in a mixed pattern, indicative of coordinated regulation of these miRNAs. Significance analysis revealed that subsets of miRNAs were strongly associated with tumor sizes and race. By prediction analysis we identified some important tumorigenic genes previously identified in ULMs that may be targeted by the dysregulated miRNAs. HMGA2 was identified as one of target genes of the let-7 family of miRNAs and has been found to be suppressed by let-7 in vitro. This article contains Supplementary material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat.

The Monocyte Chemotactic Protein-1 Gene May Contribute to Hypertension in Dahl Salt-Sensitive Rats

In a previous study, we performed a genome-wide quantitative trait loci (QTLs) analysis for blood pressure using F2 rats derived from Dahl salt-sensitive (DS) and Lewis (LEW) rats and identified two QTLs that influenced blood pressure levels. Although we determined that one of the causative genes in the chromosome (Ch) 1 region seemed to be Klk1, we did not perform detailed analyses on the Ch10 QTL region. The purpose of the present study was to identify candidate genes that influence blood pressure in the Ch10 QTL region. Using microarray analysis, we compiled a list of the genes that are differentially expressed between the two strains and that were localized to the Ch10 QTL region. Subsequent reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis identified that, while the expression levels of Ccl2 mRNA were not different between the kidneys of DS and LEW rats fed a normal diet, those in DS were 10-fold higher than those in LEW under a high-salt diet. Although the promoter reporter assay failed to identify causative nucleotide changes that led to the differential expression, monocyte chemotactic protein-1 (MCP-1) release from isolated monocytes were significantly higher in DS than in LEW. Intriguingly, this Ch10 QTL for blood pressure was also a possible QTL for urinary albumin excretion. Since Ccl2 is well known to be involved in various types of renal injury, it is likely that a higher expression of Ccl2 might aggravate macrophage infiltration, which in turn could aggravate tubulointerstitial injury, and thereby accelerate salt-sensitive hypertension. Thus, Ccl2 appears to be a interesting candidate gene for salt-sensitive hypertension in DS.