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

Identification of Stable Housekeeping Genes for miRNA Expression Studies in a Mouse Unilateral Ureteral Obstruction Model

Recently, several studies have aimed to establish the role of microRNAs (miRNAs) in the unilateral ureteral obstruction (UUO) model. Therefore, it is essential to identify the best housekeeping genes (HKG) to correctly estimate the expression levels of miRNAs. The present study aimed to identify suitable HKG to normalize the expression of miRNAs by RT-qPCR in kidney samples from the UUO mice model. We analyzed the stability of twelve endogenous reference genes of small non-coding RNAs (Snord61, Snord68, Snord72, Snord95, Snord96a, U6, let-7e-5p, let-7i-3p, miR-15b-5p, miR-16a-5p, miR-26a-5p, and miR-30c-5p) by using four software packages: NormFinder, GeNorm, ΔCt method, and BestKeeper. The optimal number of genes was calculated using GenEx software analysis. To validate the best HKG, we normalized the expression of miR-18a-5p, miR-21a-3p, and miR-29b-3p. In silico analysis revealed that Snord61, Snord68, and Snord72 were the most stable HKG between the groups. Using GenEX software and Pearson's correlation, we determined that the combination of Snord61 and Snord68 or the combination of Snord68 and Snord72, provided the best HKG association. These results along with the correlation analyses establish that the association of Snord68 and Snord72 is the best choice for miRNA expression analysis by RT-qPCR in the UUO model.

MiR-363: A potential biomarker of kidney diseases

MicroRNAs (miRNAs), a class of endogenous small RNAs with lengths of approximately 19-24 nucleotides, play important regulatory roles in cells. In recent years, miR-363 has emerged as a prominent member of the miR-92a family, participating in various biological functions, including cellular proliferation, cycle, migration, and apoptosis. In particular, miR-363 plays a critical role in acute kidney injury, renal fibrosis, and diabetic nephropathy and can serve as a biomarker for the diagnosis of renal cell carcinoma. Ongoing research is exploring its potential as a biomarker of other kidney diseases. This review focuses on the role of miR-363 in kidney diseases, elucidating its regulatory mechanisms and exploring its possible value as a biomarker of kidney diseases.

Enrichment of RedoxifibromiR miR-21-5p in Plasma Exosomes of Hypertensive Patients with Renal Injury

Several microRNAs (miRNAs) emerged as powerful regulators of fibrotic processes, "fibromiRs", and can also influence the expression of genes responsible for the generation of reactive oxygen species, "redoximiRs". We aimed to investigate whether plasma exosomes from hypertensive and diabetes patients are enriched in fibromiRs and redoximiRs using deep sequencing technology and their association with relevant signalling pathways implicated in oxidative stress and fibrogenesis by GO terms and KEGG pathways. RNA-Seq analysis from P-EXO identified 31 differentially expressed (DE) miRNAs in patients compared to controls, of which 77% are biofluid specific. The majority of the exosomal DE miRNAs were identified as fibromiRs (55%) or redoximiRs (26%). One of the most representative miRNAs identified was miR-21-5p, of which levels in P-EXO were increased by 3.83-fold change (p < 0.0001) in hypertensive patients with albuminuria and were highly associated (r Spearman = 0.64, p < 0.0001). In addition, P-EXO miR-21-5p had a high accuracy in discriminating renal damage (AUC = 0.82, p < 0.0001). Bioinformatic analysis revealed that miR-21-5p regulates key pathways in the context of organ fibrosis, such as chemokine, Ras, and MAPK signalling. Additionally, in vitro studies showed an increase in P-EXO miR-21-5p levels after TGF-β1 damage and oxidative stress. This novel study found an enrichment of fibromiRs and redoximiRs in P-EXO from hypertensive/diabetic patients with renal dysfunction. miR-21-5p, such as a RedoxifibromiR, has a significant accuracy for discriminating renal damage and is closely related with relevant signalling pathways implicated in fibrogenesis in podocytes.

MiR-21 suppression in macrophages promotes M2-like polarization and attenuates kidney ischemia-reperfusion injury

MicroRNA-21 (miR-21) is one of the most frequently upregulated miRNAs in response to kidney ischemia-reperfusion (IR) injury, exhibiting both protective and pathogenic effects depending on the cell type, disease state, and target signaling. In this study, we analyzed the function of miR-21 in various cell types to elucidate its role in ischemia-induced inflammation and acute kidney injury (AKI). Utilizing a mouse model of IR injury, we observed significant upregulation of miR-21 in renal tubular epithelial cells and macrophages following IR. Deletion of miR-21 in macrophages mitigated IR-induced pro-inflammatory cytokine production and AKI. However, conditional deletion of miR-21 in proximal tubules or nonproximal tubules did not protect the kidneys against these effects. Mechanistically, miR-21 inhibition promoted M2-like polarization in macrophages and suppressed M1-like polarization and proinflammatory cytokine production in kidneys. In vitro, miR-21 knockdown in the mouse macrophage cell line Raw246.7 or genetic deletion of miR-21 in bone marrow-derived macrophages (BMDMs) increased the percentage of CD206+ cells (M2 phenotype) while decreasing the percentage of CD86+ cells (M1 phenotype) and the expressions of proinflammatory cytokines. Overexpression of miR-21 in Raw264.7 cells reduced the percentage of CD206+ cells. Furthermore, we demonstrated that signal transducer and activator of transcription 3 (STAT3) was a target gene of miR-21 in macrophages, and miR-21 deletion promoted M2 macrophage polarization via STAT3 activation. In conclusion, miR-21 plays a role in regulating macrophage polarization, and the blockade of miR-21/STAT3 signaling may represent a novel therapeutic strategy for the prevention or treatment of AKI.

Extracellular vesicles in kidney disease - A veterinary perspective

Extracellular vesicles (EVs) are membrane bound vesicles secreted from cells into the extracellular space which have an emerging role in both normal kidney physiology and the pathophysiology of kidney injury, predominantly as mediators of intercellular communication. EVs contain proteins and RNA cargo which reflect their cell of origin and can be isolated from the urine of cats and dogs. The majority of urinary EVs (uEVs) originate from the kidney, and both the uEV proteome and transcriptome have been investigated as sources of biomarkers of kidney disease. In addition to their possible diagnostic role, EVs may also have therapeutic potential, and veterinary species have been used as models to demonstrate the efficacy of exogenous EVs derived from mesenchymal stromal cells in the treatment of acute kidney injury. Furthermore, bioengineered EVs may represent a novel vehicle for the administration of drugs or therapeutic nucleic acids in kidney disease. This article reviews the biological functions of EVs within the kidney, techniques for their isolation, and their potential use as biomarkers and therapeutic agents, with particular focus on the potential significance to veterinary patients.

Multicenter, prospective, observational study for urinary exosomal biomarkers of kidney allograft fibrosis

Severity of deceased donor kidney fibrosis impacts graft survival in deceased-donor kidney transplantation. Our aim was to identify potential miRNA biomarkers in urinary exosomes that mirror interstitial fibrosis and tubular atrophy (IFTA) severity. Among 109 urine samples from deceased donors, 34 displayed no IFTA in the zero-day biopsy (No IFTA group), while the remaining 75 deceased donor kidneys exhibited an IFTA score ≥ 1 (IFTA group). After analyzing previous reports and electronic databases, six miRNAs (miR-19, miR-21, miR-29c, miR-150, miR-200b, and miR-205) were selected as potential IFTA biomarker candidates. MiR-21, miR-29c, miR-150, and miR-205 levels were significantly higher, while miR-19 expression was significantly lower in the IFTA group. MiR-21 (AUC = 0.762; P < 0.001) and miR-29c (AUC = 0.795; P < 0.001) showed good predictive accuracy for IFTA. In the No IFTA group, the eGFR level at 1 week after transplantation was significantly higher compared to the IFTA group (41.34 mL/min/1.73m2 vs. 28.65 mL/min/1.73m2, P = 0.012). These findings signify the potential of urinary exosomal miRNAs as valuable biomarker candidates for evaluating the severity of IFTA in deceased donor kidneys before they undergo recovery.

Research Progress on Micro (Nano)Plastics Exposure-Induced miRNA-Mediated Biotoxicity

Micro- and nano-plastics (MNPs) are ubiquitously distributed in the environment, infiltrate organisms through multiple pathways, and accumulate, thus posing potential threats to human health. MNP exposure elicits changes in microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), thereby precipitating immune, neurological, and other toxic effects. The investigation of MNP exposure and its effect on miRNA expression has garnered increasing attention. Following MNP exposure, circRNAs serve as miRNA sponges by modulating gene expression, while lncRNAs function as competing endogenous RNAs (ceRNAs) by fine-tuning target gene expression and consequently impacting protein translation and physiological processes in cells. Dysregulated miRNA expression mediates mitochondrial dysfunction, inflammation, and oxidative stress, thereby increasing the risk of neurodegenerative diseases, cardiovascular diseases, and cancer. This tract, blood, urine, feces, placenta, and review delves into the biotoxicity arising from dysregulated miRNA expression due to MNP exposure and addresses the challenges encountered in this field. This study provides novel insights into the connections between MNPs and disease risk.

Polyethylene microplastics induced inflammation via the miR-21/IRAK4/NF-κB axis resulting to endoplasmic reticulum stress and apoptosis in muscle of carp

As a widespread environmental pollutant, microplastics pose a great threat to the tissues and organs of aquatic animals. The carp's muscles are necessary for movement and survival. However, the mechanism of injury of polyethylene microplastics (PE-MPs) to carp muscle remains unclear. Therefore, in this study, PE-MPs with the diameter of 8 μm and the concentration of 1000 ng/L were used to feed carp for 21 days, and polyethylene microplastic treatment groups was established. The results showed that PE-MPs could cause structural abnormalities and disarrangement of muscle fibers, and aggravate oxidative stress in muscles. Exposure to PE-MPs reduced microRNA (miR-21) in muscle tissue, negatively regulated Interleukin-1 Receptor Associated Kinase 4 (IRAK4), activated Nuclear Factor Kappa-B (NF-κB) pathway, induced inflammation, and led to endoplasmic reticulum stress and apoptosis. The present study provides different targets for the prevention of muscle injury induced by polyethylene microplastics.

Identifying key genes related to the peritubular capillary rarefaction in renal interstitial fibrosis by bioinformatics

Renal interstitial fibrosis (RIF) is a key feature of progressive chronic kidney disease (CKD), characterized by tubular epithelial cell (TEC) hypoxia and peritubular capillary (PTC) rarefaction. However, the mechanisms underlying these processes remain poorly understood. To address this knowledge gap, we conducted a comparative transcriptome analysis of hypoxic and normoxic HK-2 cells, identifying 572 differentially expressed genes (DEGs). Subsequent Gene Ontology (GO), protein‒protein interaction (PPI) network, and hub gene analyses revealed significant enrichment of DEGs in the HIF-1 signaling pathway based on KEGG enrichment analysis. To further explore TEC modulation under hypoxic conditions, we performed chromatin immunoprecipitation (ChIP) sequencing targeting HIF-1α, identifying 2915 genes potentially regulated by HIF-1α. By comparing RNA sequencing and ChIP sequencing data, we identified 43 overlapping DEGs. By performing GO analysis and peak annotation with IGV, we identified two candidate molecules, VEGFA and BTG1, that are associated with angiogenesis and whose gene sequences were reliably bound by HIF-1α. Our study elucidates the molecular mechanisms underlying RIF, providing valuable insights for potential therapeutic interventions.

MicroRNA-21 in gynecological cancers: From molecular pathogenesis to clinical significance

Ovarian, cervical, and endometrial cancers are the three most common gynecological cancer types (GCs). They hold a significant position as the leading causes of mortality among women with cancer-related death. However, GCs are often diagnosed late, severely limiting the efficacy of current treatment options. Thus, there is an urgent, unmet need for innovative experimentation to enhance the clinical treatment of GC patients. MicroRNAs (miRNAs) are a large and varied class of short noncoding RNAs (22 nucleotides in length) that have been shown to play essential roles in various biological processes involved in development. Recent research has shown that miR-211 influences tumorigenesis and cancer formation, adding to our knowledge of the miR-21 dysregulation in GCs. Furthermore, current research that sheds light on the crucial functions of miR-21 may provide supporting evidence for its potential prognostic, diagnostic, and therapeutic applications in the context of GCs. This review will thus focus on the most recent findings concerning miR-21 expression, miR-21 target genes, and the processes behind GCs. In addition, the latest findings that support miR-21's potential use as a non-invasive biomarker and therapeutic agent for detecting and treating cancer will be elucidated in this review. The roles played by various lncRNA/circRNA-miRNA-mRNA axis in GCs are also comprehensively summarized and described in this study, along with any possible implications for how these regulatory networks may contribute to the pathogenesis of GCs. Also, it is crucial to recognize the complexity of the processes involved in tumour therapeutic resistance as a significant obstacle in treating GCs. Furthermore, this review provides an overview of the current state of knowledge regarding the functional significance miR-21 in therapeutic resistance within the context of GCs.

Fibrotic Diseases of the Human Urinary and Genital Tract: Current Understanding and Potential Strategies for Treatment

Fibrosis is a disease condition characterized by abnormalities of the extracellular matrix, such as accumulation of the transforming growth factor β, infiltration by myofibroblasts, deposition of collagen, and a generalized dysregulation of collagen maturation. It can severely impair the function of organs by replacing normal tissue with a highly collagenized matrix, thereby reducing the elasticity and compliance of tissues. Fibrotic diseases of the genitourinary tract present relevant problems in healthcare, and their principles of pathophysiology remain unclarified; hence, the armamentarium for prevention and treatment is limited. These diseases include renal fibrosis, Peyronie's disease and ureteral and urethral strictures due to perturbations in the process of wound healing in response to injuries. Such deteriorations may contribute to obstructive uropathies or sexual dysfunction. This review provides a brief overview of the most frequent fibrotic diseases of the genitourinary system and of how the pathophysiology is related to symptoms, and also highlights potential therapeutic strategies to address the abnormal deposition of collagen. Although the understanding of factors associated with fibrotic conditions of the urinary and genital tract is still limited, some beneficial advances have been made. Further research will serve to provide a more comprehensive insight into factors responsible for the development of fibrotic tissue deposition.

Rab3A/Rab27A System Silencing Ameliorates High Glucose-Induced Injury in Podocytes

Diabetic nephropathy is a major complication in diabetic patients. Podocytes undergo loss and detachment from the basal membrane. Intra- and intercellular communication through exosomes are key processes for maintaining function, and the Rab3A/Rab27A system is an important counterpart. Previously, we observed significant changes in the Rab3A/Rab27A system in podocytes under glucose overload, demonstrating its important role in podocyte injury. We investigated the implication of silencing the Rab3A/Rab27A system in high glucose-treated podocytes and analysed the effect on differentiation, apoptosis, cytoskeletal organisation, vesicle distribution, and microRNA expression in cells and exosomes. For this, we subjected podocytes to high glucose and transfection through siRNAs, and we isolated extracellular vesicles and performed western blotting, transmission electron microscopy, RT-qPCR, immunofluorescence and flow cytometry assays. We found that silencing RAB3A and RAB27A generally leads to a decrease in podocyte differentiation and cytoskeleton organization and an increase in apoptosis. Moreover, CD63-positive vesicles experienced a pattern distribution change. Under high glucose, Rab3A/Rab27A silencing ameliorates some of these detrimental processes, suggesting a differential influence depending on the presence or absence of cellular stress. We also observed substantial expression changes in miRNAs that were relevant in diabetic nephropathy upon silencing and glucose treatment. Our findings highlight the Rab3A/Rab27A system as a key participant in podocyte injury and vesicular traffic regulation in diabetic nephropathy.