Human miRNome profiling identifies microRNAs differentially present in the urine after kidney injury

The role of non-protein-coding RNAs in ischemic acute kidney injury

Acute kidney injury (AKI) is a condition characterized by a rapid decline in kidney function within a span of 48 hours. It is influenced by various factors including inflammation, oxidative stress, excessive calcium levels within cells, activation of the renin-angiotensin system, and dysfunction in microcirculation. Ischemia-reperfusion injury (IRI) is recognized as a major cause of AKI; however, the precise mechanisms behind this process are not yet fully understood and effective treatments are still needed. To enhance the accuracy of diagnosing AKI during its early stages, the utilization of innovative markers is crucial. Numerous studies suggest that certain noncoding RNAs (ncRNAs), such as long noncoding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs), play a central role in regulating gene expression and protein synthesis. These ncRNAs are closely associated with the development and recovery of AKI and have been detected in both kidney tissue and bodily fluids. Furthermore, specific ncRNAs may serve as diagnostic markers and potential targets for therapeutic interventions in AKI. This review aims to summarize the functional roles and changes observed in noncoding RNAs during ischemic AKI, as well as explore their therapeutic potential.

MicroRNA-126 in dogs with immune complex-mediated glomerulonephritis

BACKGROUND

Most proteinuric dogs with naturally occurring chronic kidney disease have amyloidosis (AMYL), glomerulosclerosis (GS), or immune complex-mediated glomerulonephritis (ICGN), each with different treatment and prognosis. A noninvasive and disease-specific biomarker is lacking.

HYPOTHESIS

We hypothesized that the expression pattern of biofluid microRNA (miRNAs and miRs) would correlate with disease progression and categorization.

ANIMALS

Archived serum and urine samples from 18 dogs with glomerular disease and 6 clinically healthy dogs; archived urine samples from 49 dogs with glomerular disease and 13 clinically healthy dogs.

METHODS

Retrospective study. Archived biofluid samples from adult dogs with biopsy-confirmed glomerular disease submitted to the International Veterinary Renal Pathology Service between 2008 and 2016 were selected. Serum and urinary miRNAs were isolated and profiled using RNA sequencing. Urinary miR-126, miR-21, miR-182, and miR-486 were quantified using quantitative reverse transcription PCR.

RESULTS

When comparing more advanced disease with earlier disease, no serum miRNAs were differentially expressed, but urinary miR-21 and miR-182 were 1.63 (95% CI: .86-3.1) and 1.45 (95% CI: .82-2.6) times higher in azotemic dogs, respectively (adjusted P < .05) and weakly correlated with tubulointerstitial fibrosis (miR-21: r = .32, P = .03; miR-182: r = .28, P = .05). Expression of urinary miR-126 was 10.5 (95% CI: 4.1-26.7), 28.9 (95% CI: 10.5-79.8), and 126.2 (95% CI: 44.7-356.3) times higher in dogs with ICGN compared with dogs with GS, AMYL, and healthy controls, respectively (P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

The miR-126 could help identify dogs that might benefit from immunosuppressive therapy in the absence of a biopsy. MiR-21 and miR-182 are potential markers of disease severity and fibrosis.

Profiling salivary miRNA expression levels in Fanconi anemia patients - a pilot study

The overarching goal of this study is to predict the risk of developing oral squamous cell carcinoma (OSCC) in Fanconi anemia (FA) patients. We have compared the microRNA (miRNA, miR) expression levels in saliva samples from FA patients (n = 50) who are at a low-moderate and/or high risk of developing OSCC to saliva samples from healthy controls (n = 16). The miRNA expression levels in saliva samples were quantified using qPCR. We observed that miR-744, miR-150-5P, and miR-146B-5P had the best discriminatory capacity between FA patients and controls, with an area under the curve (AUC) of 94.0%, 92.9% and 85.3%, respectively. Our data suggest that miR-1, miR-146B-5P, miR-150-5P, miR-155-5P, and miR-744 could be used as panel to predict the risk of developing OSCC in FA patients, with a 89.3% sensitivity and a 68.2% specificity (AUC = 81.5%). Our preliminary data support the notion that the expression levels of salivary miRNAs have the potential to predict the risk of developing OSCC in FA patients and in the future may reduce deaths associated with OSCC.

MicroRNAs as Biomarkers and Therapeutic Targets for Acute Kidney Injury

Acute kidney injury (AKI) is a clinical syndrome where a rapid decrease in kidney function and/or urine output is observed, which may result in the imbalance of water, electrolytes and acid base. It is associated with poor prognosis and prolonged hospitalization. Therefore, an early diagnosis and treatment to avoid the severe AKI stage are important. While several biomarkers, such as urinary L-FABP and NGAL, can be clinically useful, there is still no gold standard for the early detection of AKI and there are limited therapeutic options against AKI. miRNAs are non-coding and single-stranded RNAs that silence their target genes in the post-transcriptional process and are involved in a wide range of biological processes. Recent accumulated evidence has revealed that miRNAs may be potential biomarkers and therapeutic targets for AKI. In this review article, we summarize the current knowledge about miRNAs as promising biomarkers and potential therapeutic targets for AKI, as well as the challenges in their clinical use.

Inflammation- and cancer-related microRNAs in rat renal cortex after subchronic exposure to fluoride

The proximal tubule is a target of subchronic exposure to fluoride (F) in the kidney. Early markers are used to classify kidney damage, stage, and prognosis. MicroRNAs (miRNAs) are small sequences of non-coding single-stranded RNA that regulate gene expression and play an essential role in developing many pathologies, including renal diseases. This study aimed to evaluate the expression of Cytokine-Chemokine molecules (IL-1α/1β/4/6/10, INF-γ, MIP-1α, MCP-1, RANTES, and TGF β1/2/3) and inflammation-related miRNAs to evidence the possible renal mechanisms involved in subchronic exposure to F. Total protein and miRNAs were obtained from the renal cortex of male Wistar rats exposed to 0, 15 and 50 mg NaF/L through drinking water during 40 and 80 days. In addition, cytokines-chemokines were analyzed by multiplexing assay, and a panel of 77 sequences of inflammatory-related miRNAs was analyzed by qPCR. The results show that cytokines-chemokines expression was concentration- and time-dependent with F, where the 50 mg NaF/L were the main altered groups. The miRNAs expression resulted in statistically significant differences in thirty-four miRNAs in the 50 mg NaF/L groups at 40 and 80 days. Furthermore, a molecular interaction network analysis was performed. The relevant pathways modified by subchronic exposure to fluoride were related to extracellular matrix-receptor interaction, Mucin type O-glycan biosynthesis, Gap junction, and miRNAs involved with renal cell carcinoma. Thus, F-induced cytokines-chemokines suggest subchronic inflammation; detecting miRNAs related to cancer and proliferation indicates a transition from renal epithelium to pathologic tissue after fluoride exposure.

Molecular profiling of urinary extracellular vesicles in chronic kidney disease and renal fibrosis

Chronic kidney disease (CKD) is a long-term kidney damage caused by gradual loss of essential kidney functions. A global health issue, CKD affects up to 16% of the population worldwide. Symptoms are often not apparent in the early stages, and if left untreated, CKD can progress to end-stage kidney disease (ESKD), also known as kidney failure, when the only possible treatments are dialysis and kidney transplantation. The end point of nearly all forms of CKD is kidney fibrosis, a process of unsuccessful wound-healing of kidney tissue. Detection of kidney fibrosis, therefore, often means detection of CKD. Renal biopsy remains the best test for renal scarring, despite being intrinsically limited by its invasiveness and sampling bias. Urine is a desirable source of fibrosis biomarkers as it can be easily obtained in a non-invasive way and in large volumes. Besides, urine contains biomolecules filtered through the glomeruli, mirroring the pathological state. There is, however, a problem of highly abundant urinary proteins that can mask rare disease biomarkers. Urinary extracellular vesicles (uEVs), which originate from renal cells and carry proteins, nucleic acids, and lipids, are an attractive source of potential rare CKD biomarkers. Their cargo consists of low-abundant proteins but highly concentrated in a nanosize-volume, as well as molecules too large to be filtered from plasma. Combining molecular profiling data (protein and miRNAs) of uEVs, isolated from patients affected by various forms of CKD, this review considers the possible diagnostic and prognostic value of uEVs biomarkers and their potential application in the translation of new experimental antifibrotic therapeutics.

The Versatile Role of miR-21 in Renal Homeostasis and Diseases

MicroRNAs (miRNAs) are small, non-coding RNA species that control gene expression and confer robustness to biological processes. Over the last two decades, their important roles during kidney development, homeostasis and the treatment of diseases have been established, in particular during the onset and progression of various forms of acute and chronic renal disorders. In recent years, miR-21, one of the best-characterized miRNAs to date, has received much attention in renal physiology in particular given its high degree of conservation and expression in kidneys, as well as its potent pathogenic role in various debilitating renal diseases. This review summarizes the current knowledge on miR-21’s involvement in both renal homeostasis and diseases, in particular its double-edged-sword role in acute versus chronic kidney injuries. Finally, we also discuss the potential of miR-21 as a biomarker and therapeutic target in renal diseases.

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.

Bioengineering exosomes for treatment of organ ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury is a leading cause of death worldwide. It arises from blood reflowing after tissue hypoxia induced by ischemia that causes severe damages due to the accumulation of reactive oxygen species and the activation of inflammatory responses. Exosomes are the smallest members of the extracellular vesicles' family, which originate from nearly all eukaryotic cells. Exosomes have a great potential in the treatment of I/R injury either in native or modified forms. Native exosomes are secreted by different cell types, such as stem cells, and contain components such as specific miRNA molecules with tissue protective properties. On the other hand, exosome bioengineering has recently received increased attention in context of current advances in the purification, manipulation, biological characterization, and pharmacological applications. There are various pre-isolation and post-isolation manipulation approaches that can be utilized to increase the circulation half-life of exosomes or the availability of their bioactive cargos in the target site. In this review, the various therapeutic actions of native exosomes in different I/R injury will be discussed first. Exosome bioengineering approaches will then be explained, including pre- and post-isolation manipulation methods, applicability for delivery of bioactive agents to injured tissue, clinical translation issues, and future perspectives.

The Impact of General Anesthesia on Redox Stability and Epigenetic Inflammation Pathways: Crosstalk on Perioperative Antioxidant Therapy

Worldwide, the prevalence of surgery under general anesthesia has significantly increased, both because of modern anesthetic and pain-control techniques and because of better diagnosis and the increased complexity of surgical techniques. Apart from developing new concepts in the surgical field, researchers and clinicians are now working on minimizing the impact of surgical trauma and offering minimal invasive procedures due to the recent discoveries in the field of cellular and molecular mechanisms that have revealed a systemic inflammatory and pro-oxidative impact not only in the perioperative period but also in the long term, contributing to more difficult recovery, increased morbidity and mortality, and a negative financial impact. Detailed molecular and cellular analysis has shown an overproduction of inflammatory and pro-oxidative species, responsible for augmenting the systemic inflammatory status and making postoperative recovery more difficult. Moreover, there are a series of changes in certain epigenetic structures, the most important being the microRNAs. This review describes the most important molecular and cellular mechanisms that impact the surgical patient undergoing general anesthesia, and it presents a series of antioxidant therapies that can reduce systemic inflammation.

Progress of exosome research in systemic lupus erythematosus

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Regulation of pro-inflammatory cytokines and immune cells by exosomes derived from SLE.

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Abnormal expression of exosome composition in SLE.

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Diagnostic role of miRNAs in Exosomes for SLE.

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Feasibility of exosomes in the treatment of SLE.

Systemic lupus erythematosus (SLE) is a global chronic autoimmune disease that invades most organs of the body, with kidney injury being the most prominent feature. Exosomes are extracellular vesicles that carry a variety of proteins, lipids and genetic material, participate in the exchange of local and intersystem information, and play an important immunoregulatory role in a variety of autoimmune diseases. At the same time, the use of exosomes as disease biomarkers and drug delivery carriers also shows great application prospects. This article reviews current progress in the application of exosomes in the pathogenesis, diagnosis and treatment of SLE.

Nucleic Acid Nanotechnology for Diagnostics and Therapeutics in Acute Kidney Injury

Acute kidney injury (AKI) has impacted a heavy burden on global healthcare system with a high morbidity and mortality in both hospitalized and critically ill patients. However, there are still some shortcomings in clinical approaches for the disease to date, appealing for an earlier recognition and specific intervention to improve long-term outcomes. In the past decades, owing to the predictable base-pairing rule and highly modifiable characteristics, nucleic acids have already become significant biomaterials for nanostructure and nanodevice fabrication, which is known as nucleic acid nanotechnology. In particular, its excellent programmability and biocompatibility have further promoted its intersection with medical challenges. Lately, there have been an influx of research connecting nucleic acid nanotechnology with the clinical needs for renal diseases, especially AKI. In this review, we begin with the diagnostics of AKI based on nucleic acid nanotechnology with a highlight on aptamer- and probe-functionalized detection. Then, recently developed nanoscale nucleic acid therapeutics towards AKI will be fully elucidated. Furthermore, the strengths and limitations will be summarized, envisioning a wiser and wider application of nucleic acid nanotechnology in the future of AKI.

Tissue Culture Models of AKI: From Tubule Cells to Human Kidney Organoids

AKI affects approximately 13.3 million people around the world each year, causing CKD and/or mortality. The mammalian kidney cannot generate new nephrons after postnatal renal damage and regenerative therapies for AKI are not available. Human kidney tissue culture systems can complement animal models of AKI and/or address some of their limitations. Donor-derived somatic cells, such as renal tubule epithelial cells or cell lines (RPTEC/hTERT, ciPTEC, HK-2, Nki-2, and CIHP-1), have been used for decades to permit drug toxicity screening and studies into potential AKI mechanisms. However, tubule cell lines do not fully recapitulate tubular epithelial cell properties in situ when grown under classic tissue culture conditions. Improving tissue culture models of AKI would increase our understanding of the mechanisms, leading to new therapeutics. Human pluripotent stem cells (hPSCs) can be differentiated into kidney organoids and various renal cell types. Injury to human kidney organoids results in renal cell-type crosstalk and upregulation of kidney injury biomarkers that are difficult to induce in primary tubule cell cultures. However, current protocols produce kidney organoids that are not mature and contain off-target cell types. Promising bioengineering techniques, such as bioprinting and "kidney-on-a-chip" methods, as applied to kidney nephrotoxicity modeling advantages and limitations are discussed. This review explores the mechanisms and detection of AKI in tissue culture, with an emphasis on bioengineered approaches such as human kidney organoid models.

Urinary miRNA Biomarkers of Drug-Induced Kidney Injury and Their Site Specificity Within the Nephron

Drug-induced kidney injury (DIKI) is a major concern in both drug development and clinical practice. There is an unmet need for biomarkers of glomerular damage and more distal renal injury in the loop of Henle and the collecting duct (CD). A cross-laboratory program to identify and characterize urinary microRNA (miRNA) patterns reflecting tissue- or pathology-specific DIKI was conducted. The overall goal was to propose miRNA biomarker candidates for DIKI that could supplement information provided by protein kidney biomarkers in urine. Rats were treated with nephrotoxicants causing injury to distinct nephron segments: the glomerulus, proximal tubule, thick ascending limb (TAL) of the loop of Henle and CD. Meta-analysis identified miR-192-5p as a potential proximal tubule-specific urinary miRNA candidate. This result was supported by data obtained in laser capture microdissection nephron segments showing that miR-192-5p expression was enriched in the proximal tubule. Discriminative miRNAs including miR-221-3p and -222-3p were increased in urine from rats treated with TAL versus proximal tubule toxicants in accordance with their expression localization in the kidney. Urinary miR-210-3p increased up to 40-fold upon treatment with TAL toxicants and was also enriched in laser capture microdissection samples containing TAL and/or CD versus proximal tubule. miR-23a-3p was enriched in the glomerulus and was increased in urine from rats treated with doxorubicin, a glomerular toxicant, but not with toxicants affecting other nephron segments. Taken together these results suggest that urinary miRNA panels sourced from specific nephron regions may be useful to discriminate the pathology of toxicant-induced lesions in the kidney, thereby contributing to DIKI biomarker development needs for industry, clinical, and regulatory use.

Urinary microRNAs as non-invasive biomarkers for toxic acute kidney injury in humans

MicroRNAs in biofluids are potential biomarkers for detecting kidney and other organ injuries. We profiled microRNAs in urine samples from patients with Russell's viper envenoming or acute self-poisoning following paraquat, glyphosate, or oxalic acid [with and without acute kidney injury (AKI)] and on healthy controls. Discovery analysis profiled for 754 microRNAs using TaqMan OpenArray qPCR with three patients per group (12 samples in each toxic agent). From these, 53 microRNAs were selected and validated in a larger cohort of patients (Russell's viper envenoming = 53, paraquat = 51, glyphosate = 51, oxalic acid = 40) and 27 healthy controls. Urinary microRNAs had significantly higher expression in patients poisoned/envenomed by different nephrotoxic agents in both discovery and validation cohorts. Seven microRNAs discriminated severe AKI patients from no AKI for all four nephrotoxic agents. Four microRNAs (miR-30a-3p, miR-30a-5p, miR-92a, and miR-204) had > 17 fold change (p < 0.0001) and receiver operator characteristics area-under-curve (ROC-AUC) > 0.72. Pathway analysis of target mRNAs of these differentially expressed microRNAs showed association with the regulation of different nephrotoxic signaling pathways. In conclusion, human urinary microRNAs could identify toxic AKI early after acute injury. These urinary microRNAs have potential clinical application as early non-invasive diagnostic AKI biomarkers.

MicroRNA in Human Acute Kidney Injury: A Systematic Review Protocol

BACKGROUND

Acute kidney injury (AKI) is a common complication of hospitalization with high morbidity and mortality for which no effective treatments exist and for which current diagnostic tools have limitations for earlier identification. MicroRNAs (miRNAs) are small non-coding RNAs that have been implicated in the pathogenesis of AKI, and some miRNAs have shown promise as therapeutic tools in animal models of AKI. However, less is known about the role of miRNAs in human AKI.

OBJECTIVE

To evaluate the role of miRNAs in human subjects with AKI.

DESIGN

Systematic review and meta-analysis.

MEASUREMENTS

Quantification of miRNA levels from human blood, urine, or kidney biopsy samples, and measures of renal function as defined in the study protocol.

METHODS

A comprehensive search strategy for Ovid MEDLINE All, Embase, Web of Science, and CENTRAL will be developed to identify investigational studies that evaluated the relationship between miRNA levels and human AKI. Primary outcomes will include measurements of kidney function and miRNA levels. Study screening, review and data extraction will be performed independently by 2 reviewers. Study quality and certainty of evidence will be assessed with validated tools. A narrative synthesis will be included and the possibility for meta-analysis will be assessed according to characteristics of clinical and statistical heterogeneity between studies.

LIMITATIONS

These include (1) lack of randomized trials of miRNAs for the prevention or treatment of human AKI, (2) quality of included studies, and (3) sources of clinical and statistical heterogeneity that may affect strength and reproducibility of results.

CONCLUSION

Previous studies of miRNAs in different animal models of AKI have generated strong interest on their use for the prevention and treatment of human AKI. This systematic review will characterize the most promising miRNAs for human research and will identify methodological constraints from miRNA research in human AKI to help inform the design of future studies.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020201253.

Molecular and functional profiling of apical versus basolateral small extracellular vesicles derived from primary human proximal tubular epithelial cells under inflammatory conditions

Proximal tubular epithelial cells (PTEC) are central players in inflammatory kidney diseases. However, the complex signalling mechanism/s via which polarized PTEC mediate disease progression are poorly understood. Small extracellular vesicles (sEV), including exosomes, are recognized as fundamental components of cellular communication and signalling courtesy of their molecular cargo (lipids, microRNA, proteins). In this study, we examined the molecular content and function of sEV secreted from the apical versus basolateral surfaces of polarized human primary PTEC under inflammatory diseased conditions. PTEC were cultured under normal and inflammatory conditions on Transwell inserts to enable separate collection and isolation of apical/basolateral sEV. Significantly increased numbers of apical and basolateral sEV were secreted under inflammatory conditions compared with equivalent normal conditions. Multi‐omics analysis revealed distinct molecular profiles (lipids, microRNA, proteins) between inflammatory and normal conditions for both apical and basolateral sEV. Biological pathway analyses of significantly differentially expressed molecules associated apical inflammatory sEV with processes of cell survival and immunological disease, while basolateral inflammatory sEV were linked to pathways of immune cell trafficking and cell‐to‐cell signalling. In line with this mechanistic concept, functional assays demonstrated significantly increased production of chemokines (monocyte chemoattractant protein‐1, interleukin‐8) and immuno‐regulatory cytokine interleukin‐10 by peripheral blood mononuclear cells activated with basolateral sEV derived from inflammatory PTEC. We propose that the distinct molecular composition of sEV released from the apical versus basolateral membranes of human inflammatory PTEC may reflect specialized functional roles, with basolateral‐derived sEV pivotal in modulating tubulointerstitial inflammatory responses observed in many immune‐mediated kidney diseases. These findings provide a rationale to further evaluate these sEV‐mediated inflammatory pathways as targets for biomarker and therapeutic development.

Urinary MicroRNAs in Environmental Health: Biomarkers of Emergent Kidney Injury and Disease

PURPOSE OF REVIEW

There is a critical need for sensitive biomarkers of renal disease and progression. Micro(mi)RNAs are attractive as next-generation biomarkers in kidney disease, particularly as urine miRNAs can inform kidney function and cellular integrity. This review summarizes recent epidemiologic and toxicologic advances using urinary miRNAs and exosomal miRNAs as novel biomarkers of chemical exposure and of kidney damage and disease.

RECENT FINDINGS

Urine miRNA biomarkers offer improved stability over protein in stored samples, relative ease of collection and quantitation, and conserved sequence homology across species. Particularly in the case of emergent environmental health threats such as chronic kidney disease of unknown origin, urinary miRNAs hold promise as biomarkers of disease and/or exposure. We present evidence to address scientific knowledge gaps, comment on the relevance of urine-derived miRNAs in environmental health research, and discuss limitations and recommendations for future directions needed to advance miRNA biomarker strategies.

Detection of urinary miRNAs for diagnosis of clear cell renal cell carcinoma

The lack of symptoms at the early stages of clear cell renal cell carcinoma (ccRCC) allows the tumour to metastasize, leading to a dramatic reduction in patient survival. Therefore, we studied and set up a method based on urinary microRNAs (miRNAs) for the diagnosis of ccRCC. First, miRNA expression in ccRCC specimens and kidney tissues from healthy subjects (HSs) was investigated through analysis of data banks and validated by comparing expression of miRNAs in ccRCC and adjacent non-cancerous kidney tissue specimens by RT-qPCR. Subsequently, we developed an algorithm to establish which miRNAs are more likely to be found in the urine of ccRCC patients that indicated miR-122, miR-1271, and miR-15b as potential interesting markers. The evaluation of their levels and three internal controls in the urine of 13 patients and 14 HSs resulted in the development of a score (7p-urinary score) to evaluate the presence of ccRCC in patients. The resulting area under the Receiver Operating Characteristic (ROC) curve, sensitivity, and specificity were equal to 0.96, 100% (95% CI 75–100%), and 86% (95% CI 57–98%), respectively. In conclusion, our study provides a proof of concept that combining the expression values of some urinary miRNAs might be useful in the diagnosis of ccRCC.

Potential role of ACE2-related microRNAs in COVID-19-associated nephropathy

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for coronavirus disease (COVID-19), potentially have severe kidney adverse effects. This organ expressed angiotensin-converting enzyme 2 (ACE2), the transmembrane protein which facilitate the entering of the virus into the cell. Therefore, early detection of the kidney manifestations of COVID-19 is crucial. Previous studies showed ACE2 role in various indications of this disease, especially in kidney effects. The MicroRNAs (miRNAs) in this organ affected ACE2 expression. Therefore, this review aims at summarizing the literature of a novel miRNA-based therapy and its potential applications in COVID-19-associated nephropathy. Furthermore, previous studies were analyzed for the kidney manifestations of COVID-19 and the miRNAs role that were published on the online databases, namely MEDLINE (PubMed) and Scopus. Several miRNAs, particularly miR-18 (which was upregulated in nephropathy), played a crucial role in ACE2 expression. Therefore, the antimiR-18 roles were summarized in various primate models that aided in developing the therapy for ACE2 related diseases.

The Cell Type-Specific Functions of miR-21 in Cardiovascular Diseases

Cardiovascular diseases are one of the prime reasons for disability and death worldwide. Diseases and conditions, such as hypoxia, pressure overload, infection, and hyperglycemia, might initiate cardiac remodeling and dysfunction by inducing hypertrophy or apoptosis in cardiomyocytes and by promoting proliferation in cardiac fibroblasts. In the vascular system, injuries decrease the endothelial nitric oxide levels and affect the phenotype of vascular smooth muscle cells. Understanding the underlying mechanisms will be helpful for the development of a precise therapeutic approach. Various microRNAs are involved in mediating multiple pathological and physiological processes in the heart. A cardiac enriched microRNA, miR-21, which is essential for cardiac homeostasis, has been demonstrated to act as a cell–cell messenger with diverse functions. This review describes the cell type–specific functions of miR-21 in different cardiovascular diseases and its prospects in clinical therapy.

MicroRNA as an early diagnostic biomarker for contrast-induced acute kidney injury

Contrast-induced acute kidney injury (CI-AKI) is a common clinical complication and an important cause of increased mortality, prolonged hospitalization, and increased medical costs. For taking effective interventions in CI-AKI, early diagnosis and active prevention are of key importance. Currently, early CI-AKI detection depends on serum creatinine (Scr) levels, which lags behind the actual time of renal injury and seriously affects early diagnosis and interventions. MicroRNA (miRNA) has been found to be a useful biomarker in early CI-AKI diagnosis. Several studies have reported on tissue and time-specific miRNAs in AKI as effective diagnostic biomarkers and potential therapeutic targets, but there are only a few studies on miRNA in CI-AKI. However, these studies are preliminary exploratory investigations on changes in miRNA expression in CI-AKI, and whether these specific miRNAs can be used as biomarkers for early CI-AKI diagnosis and as clinical therapeutic targets requires systematic and in-depth studies. Therefore, more sensitive and specific miRNAs of CI-AKI could be discovered, providing newer options and development directions for early diagnosis and intervention in clinical CI-AKI practice. This review evaluates the research progress on specific miRNAs in the early diagnosis of CI-AKI with an aim of providing basic data for the clinical application of these molecular markers in CI-AKI.

MicroRNA-423-5p as a biomarker for early diagnosis and outcome prediction of acute kidney injury in patients with acute decompensated heart failure

OBJECTIVE

To evaluate the clinical significance of serum and urinary microRNA-423-5p in the prediction of acute kidney injury onset and survival in patients with acute decompensated heart failure.

METHODS

A total of 180 acute decompensated heart failure patients, including 57 acute kidney injury cases and 123 non-acute kidney injury cases, were included in this study. Serum and urinary neutrophil gelatinase-associated lipocalin, a biomarker of renal injury of acute kidney injury, was detected using an enzyme-linked immunosorbent assay. Expression of microRNA-423-5p in serum and urine samples was examined using quantitative real-time polymerase chain reaction. The clinical significance of microRNA-423-5p was evaluated using receiver operating characteristic curve and Kaplan-Meier survival analysis.

RESULTS

The levels of neutrophil gelatinase-associated lipocalin and microRNA-423-5p in serum and urine samples were elevated in patients with acute kidney injury compared with the non-acute kidney injury cases (all P < 0.05). Serum and urinary microRNA-423-5p had relatively high predictive performance for acute kidney injury onset in acute decompensated heart failure patients, and this predictive value was more significant when combined with urinary neutrophil gelatinase-associated lipocalin. In addition, serum and urinary elevated levels of microRNA-423-5p predicted a poor 180-day survival in the acute kidney injury group.

CONCLUSION

Increased serum and urinary microRNA-423-5p can predict the occurrence of acute kidney injury in acute decompensated heart failure patients, and is associated with poor survival of acute kidney injury patients. In addition, the diagnostic value of urine neutrophil gelatinase-associated lipocalin for the early screening of acute kidney injury from acute decompensated heart failure patients might be improved by considering the changes in urinary microRNA-423-5p.

Discovery and Validation of Urinary Molecular Signature of Early Sepsis

Supplemental Digital Content is available in the text.

Objectives:

Identify alterations in gene expression unique to systemic and kidney-specific pathophysiologic processes using whole-genome analyses of RNA isolated from the urinary cells of sepsis patients.

Design:

Prospective cohort study.

Setting:

Quaternary care academic hospital.

Patients:

A total of 266 sepsis and 82 control patients enrolled between January 2015 and February 2018.

Interventions:

Whole-genome transcriptomic analysis of messenger RNA isolated from the urinary cells of sepsis patients within 12 hours of sepsis onset and from control subjects.

Measurements and Main Results:

The differentially expressed probes that map to known genes were subjected to feature selection using multiple machine learning techniques to find the best subset of probes that differentiates sepsis from control subjects. Using differential expression augmented with machine learning ensembles, we identified a set of 239 genes in urine, which show excellent effectiveness in classifying septic patients from those with chronic systemic disease in both internal and independent external validation cohorts. Functional analysis indexes disrupted biological pathways in early sepsis and reveal key molecular networks driving its pathogenesis.

Conclusions:

We identified unique urinary gene expression profile in early sepsis. Future studies need to confirm whether this approach can complement blood transcriptomic approaches for sepsis diagnosis and prognostication.

Circulating miRNAs in HER2-Positive and Triple Negative Breast Cancers: Potential Biomarkers and Therapeutic Targets

Breast cancer is one of the most prevalent diseases among women worldwide and is highly associated with cancer-related mortality. Of the four major molecular subtypes, HER2-positive and triple-negative breast cancer (TNBC) comprise more than 30% of all breast cancers. While the HER2-positive subtype lacks estrogen and progesterone receptors and overexpresses HER2, the TNBC subtype lacks estrogen, progesterone and HER2 receptors. Although advances in molecular biology and genetics have substantially ameliorated breast cancer disease management, targeted therapies for the treatment of estrogen-receptor negative breast cancer patients are still restricted, particularly for TNBC. On the other hand, it has been demonstrated that microRNAs, miRNAs or small non-coding RNAs that regulate gene expression are involved in diverse biological processes, including carcinogenesis. Moreover, circulating miRNAs in serum/plasma are among the most promising diagnostic/therapeutic tools as they are stable and relatively easy to quantify. Various circulating miRNAs have been identified in several human cancers including specific breast cancer subtypes. This review aims to discuss the role of circulating miRNAs as potential diagnostic and prognostic biomarkers as well as therapeutic targets for estrogen-receptor negative breast cancers, HER2+ and triple negative.

MicroRNAs as Biomarkers and Therapeutic Targets in Inflammation- and Ischemia-Reperfusion-Related Acute Renal Injury

Acute kidney injury (AKI), caused mainly by ischemia-reperfusion, sepsis, or nephrotoxins (such as contrast medium), is identified by an abrupt decline in kidney function and is associated with high morbidity and mortality. Despite decades of efforts, the pathogenesis of AKI remains poorly understood, and effective therapies are lacking. MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression at the posttranscriptional level to control cell differentiation, development, and homeostasis. Additionally, extracellular miRNAs might mediate cell-cell communication during various physiological and pathological processes. Recently, mounting evidence indicates that miRNAs play a role in the pathogenesis of AKI. Moreover, emerging research suggests that because of their remarkable stability in body fluids, microRNAs can potentially serve as novel diagnostic biomarkers of AKI. Of note, our previous finding that miR-494 is rapidly elevated in urine but not in serum provides insight into the ultimate role of urine miRNAs in AKI. Additionally, exosomal miRNAs derived from stem cells, known as the stem cell secretome, might be a potential innovative therapeutic strategy for AKI. This review aims to provide new data obtained in this field of research. It is hoped that new studies on this topic will not only generate new insights into the pathophysiology of urine miRNAs in AKI but also might lead to the precise management of this fatal disease.

Effects of oral exposure to arsenite on arsenic metabolism and transport in rat kidney

Nephrotoxicity is within the recognized toxic effects of arsenic. In this study we assessed the effect of arsenite on the renal capacity to metabolize and handle arsenicals in rats exposed to drinking water with 0, 1, 5, or 10 ppm sodium arsenite for ten days. Arsenite treatment did not affect the gene expression of the main enzyme catalyzing methylation of arsenite, As3mt, while it reduced the expression of GSTO1 mRNA and protein. Arsenite decreased the expression of Aqp3, Mrp1, Mrp4, and Mdr1b (i.e., transporters and channels used by arsenic), but not that of Aqp7, Glut1, Mrp2, and Mdr1a. The protein abundance of AQP3 was also reduced by arsenite. Arsenite increased urinary NGAL and FABP3 and decreased Klotho plasma levels, without alteration of creatinine, which evidenced early tubular damage. Renal Klotho mRNA and protein expressions were also downregulated, which may exacerbate renal damage. No effect was observed in selected miRNAs putatively associated with renal injury. Plasma PTH and FGF23 were similar between groups, but arsenite decreased the renal expression of Fgfr1 mRNA. In conclusion, exposure to arsenite alters the gene expression of proteins involved in the cellular handling of arsenical species and elicits tubular damage.

The circulating miRNAs as diagnostic and prognostic markers

A large portion of the human genome transcribes RNA sequences that do not code for any proteins. The first of these sequences was identified in 1993, and the best known noncoding RNAs are microRNA (miRNAs). It is now fully established that miRNAs regulate approximately 30% of the known genes that codify proteins. miRNAs are involved in several biological processes, like cell proliferation, differentiation, apoptosis and metastatization. These RNA products regulate gene expression at the post-transcriptional level, modulating or inhibiting protein expression by interacting with specific sequences of mRNAs. Mature miRNAs can be detected in blood plasma, serum and also in a wide variety of biological fluids. They can be found associated with proteins, lipids as well as enclosed in exosome vesicles. We know that circulating miRNAs (C-miRNAs) can regulate several key cellular processes in tissues different from the production site. C-miRNAs behave as endogenous mediators of RNA translation, and an extraordinary knowledge on their function has been obtained in the last years. They can be secreted in different tissue cells and associated with specific pathological conditions. Significant evidence indicates that the initiation and progression of several pathologies are "highlighted" by the presence of specific C-miRNAs, underlining their potential diagnostic relevance as clinical biomarkers. Here we review the current literature on the possible use of this new class of molecules as clinical biomarkers of diseases.

Circular RNA YAP1 acts as the sponge of microRNA-21-5p to secure HK-2 cells from ischaemia/reperfusion-induced injury

Circular RNA YAP1 (circYAP1) was reported to participate in progression of gastric cancer. However, the role of circYAP1 in acute kidney injury (AKI) remains obscure. We attempted to examine the effects of circYAP1 on ischaemia/reperfusion-stimulated renal injury. AKI model was established by treating HK-2 cells in ischaemia/reperfusion (I/R) environment. CircYAP1 expression in blood of AKI patients and I/R-treated HK-2 cells was evaluated via RT-qPCR. CCK-8, flow cytometry, ELISA and ROS assay were executed to test the impact of circYAP1 on cell viability, apoptosis, inflammatory cytokines and ROS generation. Bioinformatic analysis was executed to explore miRNA targets. The relativity between circYAP1 and miR-21-5p was verified by RT-qPCR and luciferase assay. The functions of miR-21-5p in I/R-triggered injury were reassessed. PI3K/AKT/mTOR pathway was detected by Western blot. Down-regulated circYAP1 was observed in AKI blood samples and I/R-treated HK-2 cells. CircYAP1 overexpression expedited cell growth and weakened secretion of inflammatory factors and ROS generation in I/R-disposed cells. Besides, we found circYAP1 could sponge to miR-21-5p. Interestingly, miR-21-5p overexpression overturned the repressive effects of circYAP1 on cell injury. Moreover, PI3K/AKT/mTOR pathway was activated by circYAP1 via inhibiting miR-21-5p. We demonstrated that circYAP1 activated PI3K/AKT/mTOR pathway and secured HK-2 cells from I/R injury via sponging miR-21-5p.

Emerging microRNA biomarkers for acute kidney injury in acute decompensated heart failure

Acute decompensated heart failure (ADHF) is associated with a high incidence of acute kidney injury (AKI), an abrupt loss of kidney function associated with a near doubling of mortality at 1 year. In addition to the direct threat acute HF itself poses to kidney function, the beneficial effects of commonly prescribed HF treatments must be weighed against their potentially adverse effects on glomerular perfusion. Consequently, there is an urgent need to identify early markers for AKI in ADHF to facilitate timely implementation of supportive measures to minimize kidney damage and improve outcomes. The recent recognition of the diagnostic potential of circulating microRNAs presents the potential to address this gap if microRNAs specific for AKI can be identified in serial plasma, serum and/or urine samples from well-phenotyped cohorts of ADHF patients, including a proportion with AKI. This review summarizes emerging circulating diagnostic and prognostic microRNA biomarkers (serum, plasma or urine) in HF and AKI.

microRNA-192-5p is involved in nerve repair in rats with peripheral nerve injury by regulating XIAP

Objective: MicroRNAs (miRNAs) have been demonstrated to engage in the nerve injury, while the effect of microRNA-192-5p (miR-192-5p) on the nerve repair has not yet been well understood. This study is performed to investigate how miR-192-5p affects nerve repair in rats with peripheral nerve injury by regulating X-linked inhibitor of apoptosis protein (XIAP).Methods: The rat model of left sciatic nerve injury was established, and the expression of miR-192-5p was then detected. A series of experiments were conducted to investigate the role of miR-192-5p on nerve repair in rats with peripheral nerve injury. The expression of apoptosis-related proteins (Caspase-3, Bax and Bcl-2) and nerve repair factors (NGF, BDNF, and GAP-43) was measured. Bioinformatics analysis and dual-luciferase reporter gene assay confirmed the targeting relationship between miR-192-5p and XIAP.Results: MiR-192-5p inhibition promoted the recovery of sensory function and the recovery and regeneration in rats with sciatic nerve injury. MiR-192-5p inhibition promoted the recovery of muscle atrophy caused by nerve injury. MiR-192-5p inhibition inhibited neuronal apoptosis by affecting the expression of apoptosis-related proteins and promoted the recovery of nerve function by elevating the expression of nerve repair factors induced by peripheral nerve injury. Bioinformatics analysis and dual-luciferase reporter gene assay confirmed that XIAP was a target gene of miR-192-5p.Conclusion: This study demonstrates that miR-192-5p inhibition can up-regulate the expression of XIAP, decrease the apoptosis of nerve cells, and promote the repair and regeneration of peripheral nerve injury.

The crosstalk between hypoxia-inducible factor-1α and microRNAs in acute kidney injury

Acute kidney injury (AKI) is a common critical clinical disease that is characterized by a rapid decline in renal function and reduced urine output. Ischemia and hypoxia are dominant pathophysiological changes in AKI that are induced by many factors, and the role of the “master” regulator hypoxia-inducible factor-1α (HIF-1α) is well recognized in AKI-related studies. MicroRNAs have been found to act as critical regulators of AKI pathophysiological process. More studies now have reported mutual interactions between HIF-1α and microRNAs in AKI. Therefore, in this brief review, we look into the mutual regulatory mechanisms between HIF-1α and microRNAs and discuss their function in the process of AKI. Recent studies demonstrated that HIF-1α is involved in the regulation of multiple functional microRNAs in AKI, and in turn, the level of HIF-1α is regulated by specific microRNAs. However, the role of the interactions between HIF-1α and microRNAs in AKI are controversial, and whether interventions targeting relevant mechanisms could achieve clinical benefits is not clear. Much work remains to further explore the value of targeting the HIF-1α-microRNA pathway in AKI treatment.

Impact statement

At first, we have discussed the role of hypoxia-inducible factor-1α (HIF-1α) and microRNAs in the acute kidney injury (AKI) pathophysiology. Then we have summarized the interactions between HIF-1α and microRNAs reported by AKI-related studies and concluded their regulatory effects in AKI process. Finally, we have made a vision of HIF-1α/microRNAs pathway’s potential as the intervention target in AKI. The mini review provides a systematic understanding of the crosstalk between HIF-1α and microRNAs in AKI and their effects on AKI pathophysiology and treatment.

A hairpin DNA-fueled nanoflare for simultaneous illumination of two microRNAs in drug-induced nephrotoxic cells with target catalytic recycling amplification

The detection of specific extracellular microRNAs (miRNAs) is beneficial for the prediction of drug-induced kidney injury. Here, a novel hairpin DNA-fueled nanoflare was developed for the simultaneous detection of drug-induced nephrotoxicity-related miRNA-21 and miRNA-200c with target catalytic recycling amplification. The nanoflare utilized gold nanoparticles (AuNPs) as the highly efficient quencher to ensure a low background signal. With the help of the fueled hairpin DNA, the miRNA targets could serve as the catalysts for the assembly of DNA duplexes. Therefore, the nanoflare could respond to the miRNAs to yield signal outputs of 1 : n (target : signal) rather than an equivalent reaction ratio of 1 : 1, achieving the signal amplified detection of low-abundant miRNAs. The targets can be concurrently detected with the detection limit of 18.1 and 21.1 pM for miRNA-21 and miRNA-200c, respectively, which are approximately 2 orders of magnitude lower than that of the non-catalytic probes. In addition, this nanoflare offered a high selectivity for determination between perfectly matched targets and single-base mismatched targets. It should be noted that the nanoflare was successfully employed to predict the drug-induced nephrotoxicity by the detection of miRNAs in culture media excreted from the drug-treated renal cells using a fluorescent microplate reader. Our hairpin DNA-fueled nanoflare could also accurately detect the divergence of miRNA-21 and miRNA-200c between drug-treated nephrotoxic cells and tumor cells, demonstrating a promising potential for exploring the pathogenesis of drugs and auxiliary diagnosis of drug-induced nephrotoxicity.

Epigenetic regulation in AKI and kidney repair: mechanisms and therapeutic implications

Acute kidney injury (AKI) is a major public health concern associated with high morbidity and mortality. Despite decades of research, the pathogenesis of AKI remains incompletely understood and effective therapies are lacking. An increasing body of evidence suggests a role for epigenetic regulation in the process of AKI and kidney repair, involving remarkable changes in histone modifications, DNA methylation and the expression of various non-coding RNAs. For instance, increases in levels of histone acetylation seem to protect kidneys from AKI and promote kidney repair. AKI is also associated with changes in genome-wide and gene-specific DNA methylation; however, the role and regulation of DNA methylation in kidney injury and repair remains largely elusive. MicroRNAs have been studied quite extensively in AKI, and a plethora of specific microRNAs have been implicated in the pathogenesis of AKI. Emerging research suggests potential for microRNAs as novel diagnostic biomarkers of AKI. Further investigation into these epigenetic mechanisms will not only generate novel insights into the mechanisms of AKI and kidney repair but also might lead to new strategies for the diagnosis and therapy of this disease.

Expression and significance of urinary microRNA in patients with chronic hepatitis B

The aim of this study was to investigate the alterations of urinary microRNA (miRNA) expression and explore its clinical significance in patients with chronic hepatitis B (CHB).The expression levels of urinary miRNA were detected by miRNA microarray and quantitative reverse transcription polymerase chain reaction (qRT-PCR) from 106 CHB and 40 healthy controls (Ctrl) subjects. The correlation between the levels of miRNA expression and clinical characteristics were analyzed. Receiver-operator characteristic (ROC) curves were generated to determine the specificity and sensitivity of each individual miRNA. MiRNAs expression were further measured by PCR from exosomes, which were isolated from urine samples. LX2 cells were transfected with miRNA inhibitor and accumulation of cytoplasmic lipid droplets was analyzed by Oil Red O staining.miRNA expression profile analysis showed that 22 miRNAs were upregulated and 55 miRNAs were downregulated in CHB patients compared with Ctrl subjects (fold-change>1.5 and P < .05). miR-92b-3p, miR-770-5p, miR-5196-5p, and miR-7855-5p were significantly higher (P < .0001) in CHB subjects than in Ctrl subjects. ROC curve analysis showed that these four miRNAs were sensitive and specific enough to distinguish CHB and Ctrl subjects. The levels of miR-92b-3p expression were negatively correlated with total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and APOA-1. Moreover, in vitro experiments indicated that inhibition of miR-92b-3p increased lipid droplet formation in LX2 cells.Aberrant expression of miRNAs has been observed in urine of CHB patients. Our findings may provide novel insights into the pathogenesis of CHB and may assist in the diagnosis of patients with CHB.

Uremic Toxin Lanthionine Interferes with the Transsulfuration Pathway, Angiogenetic Signaling and Increases Intracellular Calcium

(1) The beneficial effects of hydrogen sulfide (H2S) on the cardiovascular and nervous system have recently been re-evaluated. It has been shown that lanthionine, a side product of H2S biosynthesis, previously used as a marker for H2S production, is dramatically increased in circulation in uremia, while H2S release is impaired. Thus, lanthionine could be classified as a novel uremic toxin. Our research was aimed at defining the mechanism(s) for lanthionine toxicity. (2) The effect of lanthionine on H2S release was tested by a novel lead acetate strip test (LAST) in EA.hy926 cell cultures. Effects of glutathione, as a redox agent, were assayed. Levels of sulfane sulfur were evaluated using the SSP4 probe and flow cytometry. Protein content and glutathionylation were analyzed by Western Blotting and immunoprecipitation, respectively. Gene expression and miRNA levels were assessed by qPCR. (3) We demonstrated that, in endothelial cells, lanthionine hampers H2S release; reduces protein content and glutathionylation of transsulfuration enzyme cystathionine-β-synthase; modifies the expression of miR-200c and miR-423; lowers expression of vascular endothelial growth factor VEGF; increases Ca2+ levels. (4) Lanthionine-induced alterations in cell cultures, which involve both sulfur amino acid metabolism and calcium homeostasis, are consistent with uremic dysfunctional characteristics and further support the uremic toxin role of this amino acid.

Potential protective effects of Dapagliflozin in gentamicin induced nephrotoxicity rat model via modulation of apoptosis associated miRNAs

BACKGROUND

Drug-induced kidney injury (DIKI) can be manifested with progressive chronic kidney diseases or end-stage renal diseases. Understanding the molecular disarrangements caused by DIKI is an attractive point of interest. A class of non-coding RNA called microRNAs (miRNAs) is known to play a major role in regulation of gene expression and signaling pathways making miRNAs excellent targets for new therapeutic agents.

AIM OF THE STUDY

We aimed to investigate the role of miRNA 21 and 181a in gentamicin (GNT) induced nephrotoxicity rat model and the protective effect of Dapagliflozin (DAPA) in modulating their expression through studying its effect on renal function as well as renal histopathological changes.

MATERIALS AND METHODS

Wistar rats were used and divided into: naïve, DAPA, GNT and DAPA + GNT groups. In all studied groups, kidney function, oxidative stress, apoptosis markers and miRNAs' expression in serum and renal biopsies were investigated in addition to the histopathological studies to identify its early renoprotective effect.

RESULTS

DAPA was found to improve kidney function, oxidative stress markers, decrease apoptosis of renal tubular cells and increase miR-21 but decrease the expression of miR-181a with restoration of the renal architecture after 14 days of treatment in GNT induced nephrotoxicity rat model.

CONCLUSIONS

DAPA produced significant decrease in renal expression of miR-181a on the other hand it increased the expression of renal miR-21, this may introduce a novel early protective effect of DAPA against GNT-induced nephrotoxicity.

Non-Coding RNAs as New Therapeutic Targets in the Context of Renal Fibrosis

Fibrosis, or tissue scarring, is defined as the excessive, persistent and destructive accumulation of extracellular matrix components in response to chronic tissue injury. Renal fibrosis represents the final stage of most chronic kidney diseases and contributes to the progressive and irreversible decline in kidney function. Limited therapeutic options are available and the molecular mechanisms governing the renal fibrosis process are complex and remain poorly understood. Recently, the role of non-coding RNAs, and in particular microRNAs (miRNAs), has been described in kidney fibrosis. Seminal studies have highlighted their potential importance as new therapeutic targets and innovative diagnostic and/or prognostic biomarkers. This review will summarize recent scientific advances and will discuss potential clinical applications as well as future research directions.

MiR-424 is over-expressed and attenuates ischemia-reperfusion kidney injury via p53 and death receptor 6 pathway

BACKGROUND

Ischemic reperfusion injury of kidney is major cause for renal failure, however the involved pathogenesis remains unclear creating an void for its effective treatment. Here we studied involvement of microRNA-424 in renal injury.

METHODS

For the study, p53 or HIF-1α mice were used, ischemic renal injury was induced using clamping of renal pedicles bilateraly. Proximal kidney tubular cells were used for in vitro studies. Hoechst 33342 analysis was done for apoptosis. Blood urea nitrogen (BUN) and serum creatinine was done for renal function, Hematoxylin-eosin tissue damage and Terminal transferase-dUTP nick-end labeling assay for apoptosis. RT-PCR was done for miRNA and ChIP assay to identify the binding of p53 to miR-424. TargetScan and miRanda data base were scanned to find targets of miR-424. Protein expression was done by western blot analysis.

RESULTS

We discovered that, miR-424 was over-expressed in ischemic renal injury mice and in hypoxia exposed renal cells. In cells, miR-424 suppressed the expression levels of death receptor 6 (DR6) and halted the apoptosis mediated by hypoxia. Blocking of miR-424 halted the inhibition of DR6 and caused apoptosis and activation of caspase. In mice, miR-424 mimic inhibited expression of DR6 and attenuated ischemic renal injury. We established that, up-regulation of miR-424 in ischemic reperfusion injury was p53 dependent, also inhibition of p53 caused repression of miR-424 levels in hypoxia induced cells in vitro. The p53 knockout mice showed attenuation in levels of miR-424 confirming role of p53 behind up-regulation of miR-424 in vivo.

CONCLUSION

The study confirmed p53/miR-424/DR6 as a protective cascade during ischemic-reperfusion injury.

Identification of cell and disease specific microRNAs in glomerular pathologies

MicroRNAs (miRs) are small non‐coding RNAs that regulate gene expression in physiological processes as well as in diseases. Currently miRs are already used to find novel mechanisms involved in diseases and in the future, they might serve as diagnostic markers. To identify miRs that play a role in glomerular diseases urinary miR‐screenings are a frequently used tool. However, miRs that are detected in the urine might simply be filtered from the blood stream and could have been produced anywhere in the body, so they might be completely unrelated to the diseases. We performed a combined miR‐screening in pooled urine samples from patients with different glomerular diseases as well as in cultured human podocytes, human mesangial cells, human glomerular endothelial cells and human tubular cells. The miR‐screening in renal cells was done in untreated conditions and after stimulation with TGF‐β. A merge of the detected regulated miRs led us to identify disease‐specific, cell type‐specific and cell stress‐induced miRs. Most miRs were down‐regulated following the stimulation with TGF‐β in all cell types. Up‐regulation of miRs after TGF‐β was cell type‐specific for most miRs. Furthermore, urinary miRs from patients with different glomerular diseases could be assigned to the different renal cell types. Most miRs were specifically regulated in one disease. Only miR‐155 was up‐regulated in all disease urines compared to control and therefore seems to be rather unspecific. In conclusion, a combined urinary and cell miR‐screening can improve the interpretation of screening results. These data are useful to identify novel miRs potentially involved in glomerular diseases.

MiR-802 causes nephropathy by suppressing NF-κB-repressing factor in obese mice and human

Obesity is associated with significant microvascular complications including renal injuries and may induce end-stage renal disease. Emerging studies have demonstrated microRNAs (miRNAs) are potential mediators in the pathophysiological process of nephropathy. The present study aimed to investigate the role of miR-802 in obesity-related nephropathy and potential molecular mechanisms. Through utilizing obese mouse model and human subjects, we explored the therapeutic benefits and clinical application of miR-802 in protecting against nephropathy. Renal miR-802 level was positively correlated with functional parameters, including blood urea nitrogen and creatinine in obese mice. Specific silencing of renal miR-802 improved high fat diet (HFD)-induced renal dysfunction, structural disorders and fibrosis. The up-regulated inflammatory response and infiltrated macrophages were also significantly decreased in miR-802 inhibitor-treated obese mice. Mechanistically, miR-802 directly bond to 3'-UTR of NF-κB-repressing factor (NRF) and suppressed its expression. In clinical study, the circulating miR-802 level was significantly increased in obese subjects, and positively correlated with plasma creatinine level but negatively correlated with creatinine clearance. Taken together, our findings provided evidence that miR-802/NRF signalling was an important pathway in mediating obesity-related nephropathy. It is a possible useful clinical approach of treating miR-802 inhibitor to combat nephropathy.

Human umbilical cord-derived mesenchymal stem cells enhanced HK-2 cell autophagy through MicroRNA-145 by inhibiting the PI3K/AKT/mTOR signaling pathway

Recent studies have shown that autophagy exhibits a protective role in acute kidney injury (AKI), and the accumulation of advanced oxidation protein products (AOPP) participates in the progression of kidney diseases. Our previous study indicated that AOPP induced injury in renal tubular epithelial cells (RTECs) through autophagy inhibition. Besides, we found that human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) enhanced autophagy in AOPP-treated RTECs, but the underlying mechanism remains unclear. We regulated microRNA-145 (miR-145) expression in HK-2 cells (a cell line of RTECs), or co-cultured hUC-MSCs with HK-2 cells and studied the autophagic activity in HK-2 cells to explore the underlying mechanism. Our data demonstrated that upregulated miR-145 increased LC3 II and Beclin 1 levels, decreased p62 level, three autophagy related proteins, inhibited the phosphorylation of PI3K/AKT/mTOR, and increased LC3B-positive staining and the autophagosome number. Furthermore, hUC-MSCs enhanced autophagy and inhibited phosphorylation of PI3K/AKT/mTOR in AOPP-treated HK-2 cells, which was then partially rescued using miR-145 knockdown in the hUC-MSCs co-culture system. In conclusion, our study showed that hUC-MSCs enhanced autophagy in AOPP-treated HK-2 cells mediated by miR-145 via inhibition of the PI3K/AKT/mTOR pathway, which indicated that hUC-MSCs might serve as a prospective therapy for AKI.

MicroRNAs in AKI and Kidney Transplantation

MicroRNAs are epigenetic regulators of gene expression at the posttranscriptional level. They are involved in intercellular communication and crosstalk between different organs. As key regulators of homeostasis, their dysregulation underlies several morbidities including kidney disease. Moreover, their remarkable stability in plasma and urine makes them attractive biomarkers. Beyond biomarker studies, clinical microRNA research in nephrology in recent decades has focused on the discovery of specific microRNA signatures and the identification of novel targets for therapy and/or disease prevention. However, much of this research has produced equivocal results and there is a need for standardization and confirmation in prospective trials. This review aims to provide an overview of general concepts and available clinical evidence in both the pathophysiology and biomarker fields for the role of microRNA in AKI and kidney transplantation.

A urinary microRNA panel that is an early predictive biomarker of delayed graft function following kidney transplantation

Predicting immediate and subsequent graft function is important in clinical decision-making around kidney transplantation, but is difficult using available approaches. Here we have evaluated urinary microRNAs as biomarkers in this context. Profiling of 377 microRNAs in the first urine passed post-transplantation identified 6 microRNAs, confirmed to be upregulated by RT-qPCR in an expanded cohort (miR-9, -10a, -21, -29a, -221, and -429, n = 33, P < 0.05 for each). Receiver operating characteristic analysis showed Area Under the Curve 0.94 for this panel. To establish whether this early signal was sustained, miR-21 was measured daily for 5 days post-transplant, and was consistently elevated in those developing Delayed Graft Function (n = 165 samples from 33 patients, p < 0.05). The biomarker panel was then evaluated in an independent cohort, sampled at varying times in the first week post-transplantation in a separate transplant center. When considered individually, all miRs in the panel showed a trend to increase or a significant increase in those developing delayed Graft Function (miR-9: P = 0.068, mIR-10a: P = 0.397, miR-21: P = 0.003, miR-29a: P = 0.019, miR-221: P = 0.1, and miR-429: P = 0.013, n = 47) with Area Under the Curve 0.75 for the panel. In conclusion, combined measurement of six microRNAs had predictive value for delayed graft function following kidney transplantation.

Elevated expression of miR-21 and miR-155 in peripheral blood mononuclear cells as potential biomarkers for lupus nephritis

AIM

Lupus nephritis (LN) is a severe complication of systemic lupus erythematosus (SLE). There is a great interest in using microRNAs (miRNAs) as diagnostic and prognostic biomarkers in autoimmune diseases.

MATERIALS AND METHODS

This study evaluated miR-16, miR-21, miR-141, miR-146a, and miR-155 expression levels in peripheral blood mononuclear cells (PBMCs) of 55 female SLE patients with absent, inactive, or active nephritis, and 30 healthy controls (HCs) using quantitative polymerase chain reaction.

RESULTS

MiR-21 and miR-155 levels were significantly greater in the active nephritis group than in the absent, inactive or HC groups. Moreover, receiver operating characteristic and logistic regression analyses revealed miR-21 and miR-155 were significant risk factors for LN.

CONCLUSION

Overexpression of miR-21 and miR-155 in PBMCs may participate in LN pathophysiology and these miRNAs could be used as biomarkers for the condition.

MicroRNA expression profile of urinary exosomes in Type IV lupus nephritis complicated by cellular crescent

Background

Type IV lupus nephritis (LNIV) is a severe disease characterized by diffuse proliferative lesions, and its prognosis is worse with cellular crescent (LNIV-CC) involvement. Urinary exosomes have been shown to reflect the degree of kidney injury. This study was aimed to identify non-invasive diagnostic markers for LNIV-CC. We analysed the expression profile of microRNAs (miRNAs) isolated from urinary exosomes in patients with LNIV-CC and LNIV, and healthy individuals using high-throughput sequencing.

Results

A total of 66 differentially expressed miRNAs were identified, which were significantly enriched in 15 signalling pathways. Bioinformatic analysis revealed a co-expression network of miRNAs, predicted transcription factors and target mRNAs. Expression of three miRNAs including miR-3135b, miR-654-5p, and miR-146a-5p were further analysed and validated by reverse transcription-quantitative polymerase chain reaction. ROC analysis suggested these as candidate biomarkers for LNIV-CC.

Conclusions

LNIV-CC has a unique miRNA expression profile of urinary exosome and complex regulatory network. miR-3135b, miR-654-5p and miR-146a-5p in urinary exosomes could be used as novel non-invasive diagnostic markers for LNIV-CC.

New Frontiers: Approaches to Understand the Mechanistic Basis of Renal Toxicity

A scientific session entitled "New Frontiers: Approaches to Understand the Mechanistic Basis of Renal Toxicity" focused on novel biomarkers to monitor kidney injury both preclinically and clinically, as well as providing mechanistic insight of the induced injury. Further, the role and impact of kidney membrane transporters in drug-induced kidney toxicity provided additional considerations when understanding kidney injury and the complex role of drug transporters in either sensitivity or resistance to drug-induced injury. The onset of nephropathy in diabetic patients was also presented, focusing on the quest to discover novel biomarkers that would differentiate diabetic populations more susceptible to nephropathy and renal failure. The session highlighted exciting new research areas and novel biomarkers that will enhance our understanding of kidney injury and provide tools for ensuring patient safety clinically.