circLRP6 regulates high glucose-induced proliferation, oxidative stress, ECM accumulation, and inflammation in mesangial cells

Molecular mechanisms of diabetic nephropathy: A narrative review

Diabetic nephropathy (DN) is the predominant secondary nephropathy resulting in global end-stage renal disease. It is attracting significant attention in both domestic and international research due to its widespread occurrence, fast advancement, and limited choices for prevention and treatment. The pathophysiology of this condition is intricate and involves multiple molecular and cellular pathways at various levels. This article provides a concise overview of the molecular processes involved in the development of DN. It discusses various factors, such as signaling pathways, cytokines, inflammatory responses, oxidative stress, cellular damage, autophagy, and epigenetics. The aim is to offer clinicians a valuable reference for DN's diagnosis, treatment, and intervention.

The Role of Circular RNA in the Pathogenesis of Chemotherapy-Induced Cardiotoxicity in Cancer Patients: Focus on the Pathogenesis and Future Perspective

Cardiotoxicity is a serious challenge cancer patients face today. Various factors are involved in cardiotoxicity. Circular RNAs (circRNAs) are one of the effective factors in the occurrence and prevention of cardiotoxicity. circRNAs can lead to increased proliferation, apoptosis, and regeneration of cardiomyocytes by regulating the molecular pathways, as well as increasing or decreasing gene expression; some circRNAs have a dual role in cardiomyocyte regeneration or death. Identifying each of the pathways related to these processes can be effective on managing patients and preventing cardiotoxicity. In this study, an overview of the molecular pathways involved in cardiotoxicity by circRNAs and their effects on the downstream factors have been discussed.

A NOVEL CIRC_SUPT3/MIR-185-5P/G3BP2 CERNA NETWORK REGULATES HIGH GLUCOSE-INDUCED INJURY IN MOUSE PODOCYTE MPC5 CELLS

ABSTRACT

Background: Diabetic nephropathy (DN) is a complication of diabetes that is the leading cause of death in diabetic patients. Circular RNA (circRNA) is a hot topic in the research of human diseases. However, the role of circ_Supt3 in DN remains unclear. Methods: High glucose (HG) treatment of mouse podocyte (MPC5) cells to mimic DN cell injury. Quantitative real-time polymerase chain reaction was performed to detect the expression of circ_Supt3, microRNA-185-5p (miR-185-5p), and GTPase-activating protein-binding protein 2 (G3bp2). 5-Ethynyl-2'-deoxyuridine (EdU) and 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium Bromide (MTT) assays were used to examine cell proliferation, and flow cytometry was used to detect cell apoptosis. Western blot was used to assess the levels of relative proteins. Enzyme-linked immunosorbent assay detected the inflammation cytokines. Dual-luciferase reporter and RNA pull-down assays were used to confirm the interaction of miR-185-5p and circ_Supt3 or G3bp2. Results: Circ_Supt3 and G3bp2 were highly expressed and miR-185-5p expression was diminished in DN mice. HG treatment inhibited cell proliferation and accelerated cell apoptosis and inflammation response, and the knockdown of circ_Supt3 reversed these effects. Bioinformatics predicted that circ_Supt3 contained a binding site for miR-185-5p, and G3bp2 was a direct target of miR-185-5p. Circ_Supt3 regulated G3bp2 expression by miR-185-5p. Moreover, the circ_Supt3/miR-185-5p/G3bp2 axis regulated the cell behavior of HG-induced MPC5 cells. Conclusion: Our findings suggest that the knockdown of circ_Supt3 protects mouse MPC5 cells against HG-induced cell injury via the miR-185-5p/G3bp2 axis.

Dapagliflozin restores autophagy and attenuates apoptosis via the AMPK/mTOR pathway in diabetic nephropathy rats and high glucose-induced HK-2 cells

PURPOSE

Diabetic nephropathy (DN) is a serious microvascular complication of diabetes mellitus. Significantly reduced levels of autophagy in diabetic kidneys play an important role in the development of DN. The present study investigated the effects of dapagliflozin (DAP) on renal autophagy and AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway in vivo and in vitro.

METHODS

We explored the effect of DAP in streptozotocin (STZ)-induced DN rats. The anti-DN effect of DAP was assessed by body weight, kidney weight/body weight ratio, blood and urine biochemical parameters, and pathological changes of kidney tissue. Number of autophagosomes in the kidney was investigated through Transmission electron microscopy. Besides, cell viability and apoptosis of DAP alone or combined with Compound C (CC, a selective AMPK inhibitor)-treated high glucose (HG)-induced HK-2 cells were detected by Cell Counting Kit-8 (CCK-8) and flow cytometry assays. Immunohistochemistry, Western blot, Enzyme-linked immunosorbent assay (ELISA), and immunofluorescence were employed to detect the expression levels of extracellular matrix (ECM) deposition, autophagy, apoptosis, and AMPK/mTOR pathway-associated targets in vivo and in vitro.

RESULTS

The results showed that DAP ameliorated the body weight and decreased kidney weight, fasting blood glucose, and serum/urine biochemical parameters of renal damage, as well as renal pathological changes. Moreover, DAP significantly ameliorated HG-induced cell apoptosis and ECM deposition in HK-2 cells. However, these favorable effects of DAP could be abolished by co-treatment with CC in HG-induced HK-2 cells. Mechanistically, DAP can enhance autophagy in DN including increased LC3-II/I ratio, Beclin-1, p-AMPK protein levels, and decreased p62 and p-mTOR protein expressions, as well as inhibited renal fibrosis and apoptosis.

CONCLUSION

In summary, DAP alleviated fibrosis, apoptosis, and autophagy in DN rats and HG-induced HK-2 cells by regulating the AMPK/mTOR pathway.

Circ-0000953 deficiency exacerbates podocyte injury and autophagy disorder by targeting Mir665-3p-Atg4b in diabetic nephropathy

Circular RNAs (circRNAs) are special non-coding RNA (ncRNA) molecules that play a significant role in many diseases. However, the biogenesis and regulation of circRNAs in diabetic nephropathy (DN) are largely unknown. Here, we investigated the expression profile of circRNAs in kidney of DN mice through circular RNA sequencing (circRNA-seq). The renal biopsy samples of patients with DN had low circ -0,000,953 expression, which was significantly associated with renal function. Furthermore, loss-of-function and gain-of-function experiments were carried out to prove the role of circ -0,000,953 in DN. Podocyte conditional knockin (cKI) or systemic overexpression of circ -0,000,953 alleviated albuminuria and restored macroautophagy/autophagy in kidney of diabetic mice. However, circ -0,000,953 knockdown exacerbated albuminuria and podocyte injury. Mechanistically, we found circ -0,000,953 directly binds to Mir665-3p-Atg4b to perform its function. Silencing of Mir665-3p or overexpression of Atg4b recovered podocyte autophagy both in vitro and in vivo. To examine the cause of circ -0,000,953 downregulation in DN, bioinformatics prediction found that circ -0,000,953 sequence has a high possibility of containing an m6A methylation site. Additionally, METTL3 was proved to regulate the expression and methylation level of circ -0,000,953 through YTHDF2 (YTH N6-methyladenosine RNA binding protein 2). In conclusion, this study revealed that circ -0,000,953 regulates podocyte autophagy by targeting Mir665-3p-Atg4b in DN. Therefore, circ -0,000,953 is a potential biomarker for prevention and cure of DN.Abbreviation: CCL2/MCP-1: C-C motif chemokine ligand 2; ceRNA: competing endogenous RNA; circRNA: circular RNA; cKI: conditional knockin; cKO: conditional knockout; CRE: creatinine; DM: diabetes mellitus; DN: diabetic nephropathy; ESRD: end-stage renal disease; HG: high glucose; IF: immunofluorescence; MAP1LC3/LC3B: microtubule-associated protein 1 light chain 3 beta; MPC5: mouse podocyte clone 5; MTECs: mouse tubular epithelial cells; MTOR: mechanistic target of rapamycin kinase; NC: normal control; ncRNA: non-coding RNA; NPHS1: nephrosis 1, nephrin; NPHS2: nephrosis 2, podocin; PAS: periodic acid-Schiff; RELA/p65: v-rel reticuloendotheliosis viral oncogene homolog A (avian); SDs: slit diaphragm proteins; Seq: sequencing; STZ: streptozotocin; SV40: SV40-MES13-cells, mouse mesangial cell line; T1D: type 1 diabetes mellitus; T2D: type 2 diabetes mellitus; TEM: transmission electron microscopy; TNF/TNF-α: tumor necrosis factor; VECs: vascular endothelial cells; WT1: WT1 transcription factor; YTHDF2: YTH N6-methyladenosine RNA binding protein 2.

CircGAB1 Facilitates Podocyte Injury Through Sponging miR-346 and Activating MAPK6 in Diabetic Nephropathy

BACKGROUND

Podocyte injury is very important process in diabetic nephropathy (DN) progression. Circular RNA (circRNA) takes part in regulating the advancement of DN. Herein, we explored the role and mechanism of circGAB1 in DN progression.

METHODS

The abundances of circGAB1, microRNA-346 (miR-346) and mitogen-activated protein kinase 6 (MAPK6) were detected by qRT-PCR in DN serum samples and podocyte HGPC. Moreover, cell viability and apoptosis were determined using CCK8 assay and flow cytometry. Also, the protein levels of MAPK6, proliferation-related markers and apoptosis-related markers were analyzed by western blot. ELISA assay was used to measure the levels of inflammatory factors, and corresponding kits were used to detect the levels of oxidative stress-related markers. The relationship between miR-346 and circGAB1 or MAPK6 was distinguished by dual-luciferase reporter assay.

RESULTS

CircGAB1 expression was increased in DN serum samples and HG-treated HGPC cells. CircGAB1 knockdown inhibited HG-induced apoptosis, inflammatory response and oxidative stress in HGPC cells. In terms of mechanism, circGAB1 sponged miR-346, and miR-346 targeted MAPK6. The inhibition effect of circGAB1 knockdown on HG-induced podocyte injury could be reversed by miR-346 inhibitor. Moreover, miR-346 overexpression repressed HG-induced podocyte injury by targeting MAPK6. CircGAB1 served as miR-346 sponge to positively regulate MAPK6.

CONCLUSION

CircGAB1 contributed to podocyte injury through mediating miR-346/MAPK6 axis, suggesting that circGAB1 might promote DN progression.

Circ-Luc7l Absence Attenuates Diabetic Nephropathy Progression by Reducing Mesangial Cell Excessive Proliferation, Inflammation, and Extracellular Matrix Accumulation via Mediating the miR-205-5p/Tgfbr1 Pathway

Diabetic nephropathy (DN) threatens the survival quality of patients, with complex pathogenesis. Circular RNA (circRNA) dysregulation occurs in DN development. This work aimed to investigate the role of circ-Luc7l in DN cell models and related molecular mechanisms. The expression of circ-Luc7l, microRNA (miR)-205-5p, and transforming growth factor-beta receptor 1 (Tgfbr1) was examined by real-time quantitative PCR (RT-qPCR). Cell viability and proliferation were detected by Cell Counting Kit-8 (CCK-8) assay and EdU assay. The expression of extracellular matrix (ECM)-related markers and Tgrbr1 protein was measured by Western blot. The binding between miR-205-5p and circ-Luc7l or Tgfbr1 was validated by dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, or RNA pull-down assay. Experimental animal models were established to elucidate the function of circ-Luc7l in vivo. Circ-Luc7l expression was notably enhanced in high glucose (HG)-treated mesangial cells. Knockdown of circ-Luc7l attenuated HG-induced cell proliferation, inflammation, and ECM accumulation in vitro and relieved inflammation and ECM accumulation of kidneys of diabetic mice in vivo. Circ-Luc7l targeted miR-205-5p, and miR-205-5p inhibition rescued the depletion effects of circ-Luc7l knockdown on cell proliferation, inflammation, and ECM accumulation. MiR-205-5p bound to Tgfbr1 whose expression was negatively regulated by circ-Luc7l. Tgfbr1 overexpression also rescued the depletion effects of circ-Luc7l knockdown on cell proliferation, inflammation, and ECM accumulation. In HG conditions, increased circ-Luc7l upregulated Tgfbr1 expression via targeting miR-205-5p to induce DN progression.

N6-methyladenosine RNA methylation in diabetic kidney disease

Diabetic kidney disease (DKD) is a major microvascular complication of diabetes, and hyperglycemic memory associated with diabetes carries the risk of disease occurrence, even after the termination of blood glucose injury. The existence of hyperglycemic memory supports the concept of an epigenetic mechanism involving n6-methyladenosine (m6A) modification. Several studies have shown that m6A plays a key role in the pathogenesis of DKD. This review addresses the role and mechanism of m6A RNA modification in the progression of DKD, including the regulatory role of m6A modification in pathological processes, such as inflammation, oxidative stress, fibrosis, and non-coding (nc) RNA. This reveals the importance of m6A in the occurrence and development of DKD, suggesting that m6A may play a role in hyperglycemic memory phenomenon. This review also discusses how some gray areas, such as m6A modified multiple enzymes, interact to affect the development of DKD and provides countermeasures. In conclusion, this review enhances our understanding of DKD from the perspective of m6A modifications and provides new targets for future therapeutic strategies. In addition, the insights discussed here support the existence of hyperglycemic memory effects in DKD, which may have far-reaching implications for the development of novel treatments. We hypothesize that m6A RNA modification, as a key factor regulating the development of DKD, provides a new perspective for the in-depth exploration of DKD and provides a novel option for the clinical management of patients with DKD.

The role of innate immunity in diabetic nephropathy and their therapeutic consequences

Diabetic nephropathy (DN) is an enduring condition that leads to inflammation and affects a substantial number of individuals with diabetes worldwide. A gradual reduction in glomerular filtration and emergence of proteins in the urine are typical aspects of DN, ultimately resulting in renal failure. Mounting evidence suggests that immunological and inflammatory factors are crucial for the development of DN. Therefore, the activation of innate immunity by resident renal and immune cells is critical for initiating and perpetuating inflammation. Toll-like receptors (TLRs) are an important group of receptors that identify patterns and activate immune responses and inflammation. Meanwhile, inflammatory responses in the liver, pancreatic islets, and kidneys involve inflammasomes and chemokines that generate pro-inflammatory cytokines. Moreover, the activation of the complement cascade can be triggered by glycated proteins. This review highlights recent findings elucidating how the innate immune system contributes to tissue fibrosis and organ dysfunction, ultimately leading to renal failure. This review also discusses innovative approaches that can be utilized to modulate the innate immune responses in DN for therapeutic purposes.

Circular RNAs: An emerging precise weapon for diabetic nephropathy diagnosis and therapy

Diabetic nephropathy (DN) is a prevalent chronic microvascular complication associated with diabetes mellitus and represents a major cause of chronic kidney disease and renal failure. Current treatment strategies for DN primarily focus on symptom alleviation, lacking effective approaches to halt or reverse DN progression. Circular RNA (circRNA), characterized by a closed-loop structure, has emerged as a novel non-coding RNA regulator of gene expression, attributed to its conservation, stability, specificity, and multifunctionality. Dysregulation of circRNA expression is closely associated with DN progression, whereby circRNA impacts kidney cell injury by modulating cell cycle, differentiation, cell death, as well as influencing the release of inflammatory factors and stromal fibronectin expression. Consequently, circRNA is considered a predictive biomarker and a potential therapeutic target for DN. This review provides an overview of the latest research progress in the classification, functions, monitoring methods, and databases related to circRNA. The paper focuses on elucidating the impact and underlying mechanisms of circRNA on kidney cells under diabetic conditions, aiming to offer novel insights into the prevention, diagnosis, and treatment of DN.

Analysis of circRNA profiles and clinical value in Stevens-Johnson syndrome and toxic epidermal necrolysis

Severe cutaneous adverse drug reactions, including Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), are challenging to be early diagnosed and evaluate their prognoses. This investigation aimed to analyse the expression profiles of SJS/TEN in peripheral blood mononuclear cells (PBMC) and assess the correlation between circular RNA (circRNA) and disease severity. Sixteen SJS/TEN patients and sixteen controls were enrolled and serum samples of both groups were obtained. CircRNA expression profiles in three SJS/TEN patients and three controls were detected by RNA sequencing and bioinformatic analyses were then performed. The differentially expressed circRNAs were verified by quantitative polymerase chain reaction (qPCR). Then, analysing the correlation of circRNAs with the toxic epidermal necrolysis-specific severity of illness score (SCORTEN) and the epidermal detachment area. A total of 134 circRNAs were differentially expressed in the PBMCs of SJS/TEN individuals, according to our results. The qPCR showed that three circRNAs (hsa_circ_0000711, hsa_circ_0083619 and hsa_circ_0005615) were down-regulated, and one circRNA (hsa_circ_0003028) was up-regulated, which were compatible with the sequencing findings. The concentration of hsa_circ_0083619 was closely associated with the SCORTEN scale (r = -0.581, p = 0.037) and the epidermal detachment area (r = -0.576, p = 0.039). The circRNA-miRNA-mRNA prediction network was used to construct the hsa_circ_0083619/miR-18a-5p/BCL2L10 axis. The hsa_circ_0083619 could serve as a disease severity indicator for SJS/TEN. Through bioinformatics analysis, we speculated that hsa_circ_0083619/miR-18a-5p/BCL2L10 axis might play a role in SJS/TEN pathogenesis.

Multiple novel functions of circular RNAs in diabetes mellitus

Circular RNAs (circRNAs), as an emerging group of non-coding RNAs (ncRNAs), have received the attention given evidence indicating that these novel ncRNAs are implicated in various biological processes. Due to the absence of 5' and 3' ends in circ-RNAs, their two ends are covalently bonded together, and they are synthesised from pre-mRNAs in a process called back-splicing, which makes them more stable than linear RNAs. There is accumulating evidence showing that circRNAs play a critical role in the pathogenesis of diabetes mellitus (DM). Moreover, it has been indicated that dysregulation of circRNAs has made them promising diagnostic biomarkers for the detection of DM. Recently, increasing attention has been paid to investigate the mechanisms underlying the DM process. It has been demonstrated that there is a strong correlation between the expression of circRNAs and DM. Hence, our aim is to discuss the crosstalk between circRNAs and DM and its complications.

N6-methyladenosine methylation in kidney injury

Multiple mechanisms are involved in kidney damage, among which the role of epigenetic modifications in the occurrence and development of kidney diseases is constantly being revealed. However, N6-methyladenosine (M6A), a well-known post-transcriptional modification, has been regarded as the most prevalent epigenetic modifications in higher eukaryotic, which is involved in various biological processes of cells such as maintaining the stability of mRNA. The role of M6A modification in the mechanism of kidney damage has attracted widespread attention. In this review, we mainly summarize the role of M6A modification in the progression of kidney diseases from the following aspects: the regulatory pattern of N6-methyladenosine, the critical roles of N6-methyladenosine in chronic kidney disease, acute kidney injury and renal cell carcinoma, and then reveal its potential significance in the diagnosis and treatment of various kidney diseases. A better understanding of this field will be helpful for future research and clinical treatment of kidney diseases.

Epigenetic modification in diabetic kidney disease

Diabetic kidney disease (DKD) is a common microangiopathy in diabetic patients and the main cause of death in diabetic patients. The main manifestations of DKD are proteinuria and decreased renal filtration capacity. The glomerular filtration rate and urinary albumin level are two of the most important hallmarks of the progression of DKD. The classical treatment of DKD is controlling blood glucose and blood pressure. However, the commonly used clinical therapeutic strategies and the existing biomarkers only partially slow the progression of DKD and roughly predict disease progression. Therefore, novel therapeutic methods, targets and biomarkers are urgently needed to meet clinical requirements. In recent years, increasing attention has been given to the role of epigenetic modification in the pathogenesis of DKD. Epigenetic variation mainly includes DNA methylation, histone modification and changes in the noncoding RNA expression profile, which are deeply involved in DKD-related inflammation, oxidative stress, hemodynamics, and the activation of abnormal signaling pathways. Since DKD is reversible at certain disease stages, it is valuable to identify abnormal epigenetic modifications as early diagnosis and treatment targets to prevent the progression of end-stage renal disease (ESRD). Because the current understanding of the epigenetic mechanism of DKD is not comprehensive, the purpose of this review is to summarize the role of epigenetic modification in the occurrence and development of DKD and evaluate the value of epigenetic therapies in DKD.

CircRNAs regulate the crosstalk between inflammation and tumorigenesis: The bilateral association and molecular mechanisms

Inflammation, a hallmark of cancer, has been associated with tumor progression, transition into malignant phenotype and efficacy of the chemotherapeutic agents in cancer. Chronic inflammation provides a favorable environment for tumorigenesis by inducing immunosuppression, whereas acute inflammation prompts tumor suppression by generating anti-tumor immune responses. Inflammatory factors derived from interstitial cells or tumor cells can stimulate cell proliferation and survival by modulating oncogenes and/or tumor suppressors. Recently, a new class of RNAs, i.e., circular RNAs (circRNAs), has been implicated in inflammatory diseases. Although there are reports on circRNAs imparting functions in inflammatory insults, whether these circularized transcripts hold the potential to regulate inflammation-induced cancer or tumor-related inflammation, and modulate the interactions between tumor microenvironment (TME) and the inflammatory stromal/immune cells, awaits further elucidation. Contextually, the current review describes the molecular association between inflammation and cancer, and spotlights the regulatory mechanisms by which circRNAs can moderate TME in response to inflammatory signals/triggers. We also present comprehensive information about the immune cell(s)-specific expression and functions of the circRNAs in TME, modulation of inflammatory signaling pathways to drive tumorigenesis, and their plausible roles in inflammasomes and tumor development. Moreover, the therapeutic potential of these circRNAs in harnessing inflammatory responses in cancer is also discussed.

Understanding the roles and regulation patterns of circRNA on its host gene in tumorigenesis and tumor progression

Circular RNAs (circRNAs) are a novel type of endogenous non-coding RNAs, which are covalently closed loop structures formed by precursor mRNAs (pre-mRNAs) through back-splicing. CircRNAs are abnormally expressed in many tumors, and play critical roles in a variety of tumors as oncogenes or tumor suppressor genes by sponging miRNAs, regulating alternative splicing and transcription, cis-regulating host genes, interacting with RNA binding proteins (RBPs) or encoding polypeptides. Among them, the regulation of circRNAs on their corresponding host genes is a critical way for circRNAs to exit their functions. Accumulating evidence suggests that circRNAs are able to regulate the expression of host genes at the transcriptional level, post-transcriptional level, translational level, post-translational level, or by encoding polypeptides. Therefore, this paper mainly summarized the roles and association of circRNAs and their corresponding host genes in tumorigenesis and tumor progression, generalized the circRNAs that function synergistically or antagonistically with their host genes, and elaborated the mechanisms of mutual regulation between circRNAs and their host genes. More importantly, this review provides specific references for revealing the potential application of circRNAs combined with their host genes in tumor diagnosis, treatment and prognosis.

LncRNA 1500026H17Rik knockdown ameliorates high glucose-induced mouse podocyte injuries through the miR-205-5p/EGR1 pathway

BACKGROUND

Podocyte injuries and dysfunctions contribute to the development of diabetic nephropathy (DN). This study aimed to investigate the role and novel mechanism of lncRNA 1500026H17Rik in high glucose (HG)-treated podocytes.

METHODS

DN mice were induced by streptozotocin, and DN in vitro models were constructed in mouse podocytes treated with HG. The expression of fibrosis-related proteins and early growth response protein 1 (EGR1) was detected by western blot. The expression of 1500026H17Rik, miR-205-5p and EGR1 mRNA was measured by quantitative real-time polymerase chain reaction (qRT-PCR). Cell apoptosis was monitored by flow cytometry assay. Oxidative stress was assessed according to the levels of superoxide dismutase (SOD), malondialdehyde (MDA) and reactive oxygen species (ROS). Inflammatory response was assessed according to the releases of interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). The target relationship between miR-205-5p and 1500026H17Rik or EGR1 was validated by dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay and RNA pull-down assay.

RESULTS

1500026H17Rik was upregulated in DN mice and HG-induced podocytes. 1500026H17Rik knockdown alleviated podocyte apoptosis, fibrosis, oxidative stress and inflammation induced by HG. MiR-205-5p was a target of 1500026H17Rik, and EGR1 was a downstream target of miR-205-5p. Rescue experiments presented that miR-205-5p inhibition reversed the effects of 1500026H17Rik knockdown. Moreover, miR-205-5p restoration also ameliorated HG-induced cell injuries, which were overturned by EGR1 overexpression. In addition, EGR1 overexpression recovered podocyte apoptosis, fibrosis, oxidative stress and inflammation weakened by 1500026H17Rik knockdown.

CONCLUSION

1500026H17Rik knockdown alleviated HG-induced podocyte injuries, including apoptosis, fibrosis, oxidative stress and inflammation, by governing the miR-205-5p/EGR1 pathway, thus involving in DN development.

Oxidative stress as a culprit in diabetic kidney disease

Diabetic kidney disease (DKD) has become the leading cause of end-stage renal disease (ESRD), and the prevalence of DKD has increased worldwide during recent years. DKD is associated with poor therapeutic outcomes in most patients, but there is limited understanding of its pathogenesis. This review suggests that oxidative stress interacts with many other factors in causing DKD. Highly active mitochondria and NAD(P)H oxidase are major sources of oxidants, and they significantly affect the risk for DKD. Oxidative stress and inflammation may be considered reciprocal causes of DKD, in that each is a cause and an effect of DKD. Reactive oxygen species (ROS) can act as second messengers in various signaling pathways and as regulators of metabolism, activation, proliferation, differentiation, and apoptosis of immune cells. Epigenetic modifications, such as DNA methylation, histone modifications, and non-coding RNAs can modulate oxidative stress. The development of new technologies and identification of new epigenetic mechanisms may provide novel opportunities for the diagnosis and treatment of DKD. Clinical trials demonstrated that novel therapies which reduce oxidative stress can slow the progression of DKD. These therapies include the NRF2 activator bardoxolone methyl, new blood glucose-lowering drugs such as sodium-glucose cotransporter 2 inhibitors, and glucagon-like peptide-1 receptor agonists. Future studies should focus on improving early diagnosis and the development of more effective combination treatments for this multifactorial disease.

Advanced Drug Delivery Systems for Renal Disorders

Kidney disease management and treatment are currently causing a substantial global burden. The kidneys are the most important organs in the human urinary system, selectively filtering blood and metabolic waste into urine via the renal glomerulus. Based on charge and/or molecule size, the glomerular filtration apparatus acts as a barrier to therapeutic substances. Therefore, drug distribution to the kidneys is challenging, resulting in therapy failure in a variety of renal illnesses. Hence, different approaches to improve drug delivery across the glomerulus filtration barrier are being investigated. Nanotechnology in medicine has the potential to have a significant impact on human health, from illness prevention to diagnosis and treatment. Nanomaterials with various physicochemical properties, including size, charge, surface and shape, with unique biological attributes, such as low cytotoxicity, high cellular internalization and controllable biodistribution and pharmacokinetics, have demonstrated promising potential in renal therapy. Different types of nanosystems have been employed to deliver drugs to the kidneys. This review highlights the features of the nanomaterials, including the nanoparticles and corresponding hydrogels, in overcoming various barriers of drug delivery to the kidneys. The most common delivery sites and strategies of kidney-targeted drug delivery systems are also discussed.

Recent insights into the roles of circular RNAs in human brain development and neurologic diseases

Circular RNAs (circRNAs) are a novel class of non-coding RNAs. They are single-stranded RNA transcripts characterized with a closed loop structure making them resistant to degrading enzymes. Recently, circRNAs have been suggested with regulatory roles in gene expression involved in controlling various biological processes. Notably, they have demonstrated abundance, dynamic expression, back-splicing events, and spatiotemporally regulation in the human brain. Accordingly, they are expected to be involved in brain functions and related diseases. Studies in animals and human brain have revealed differential expression of circRNAs in brain compartments. Interestingly, contributing roles of circRNAs in the regulation of central nervous system (CNS) development have been demonstrated in a number of studies. It has been proposed that circRNAs play role in substantial neurological functions like neurotransmitter-associated tasks, neural cells maturation, and functions of synapses. Furthermore, 3 main pathways have been identified in association with circRNAs's host genes including axon guidance, Wnt signaling, and transforming growth factor beta (TGF-β) signaling pathways, which are known to be involved in substantial functions like migration and differentiation of neurons and specification of axons, and thus play role in brain development. In this review, we have an overview to the biogenesis, biological functions of circRNAs, and particularly their roles in human brain development and the pathogenesis of neurodegenerative diseases including Alzheimer's diseases, multiple sclerosis, Parkinson's disease and brain tumors.

Circular RNAs in organ injury: recent development

Circular ribonucleic acids (circRNAs) are a class of long non-coding RNA that were once regarded as non-functional transcription byproducts. However, recent studies suggested that circRNAs may exhibit important regulatory roles in many critical biological pathways and disease pathologies. These studies have identified significantly differential expression profiles of circRNAs upon changes in physiological and pathological conditions of eukaryotic cells. Importantly, a substantial number of studies have suggested that circRNAs may play critical roles in organ injuries. This review aims to provide a summary of recent studies on circRNAs in organ injuries with respect to (1) changes in circRNAs expression patterns, (2) main mechanism axi(e)s, (3) therapeutic implications and (4) future study prospective. With the increasing attention to this research area and the advancement in high-throughput nucleic acid sequencing techniques, our knowledge of circRNAs may bring fruitful outcomes from basic and clinical research.

circMTND5 Participates in Renal Mitochondrial Injury and Fibrosis by Sponging MIR6812 in Lupus Nephritis

Recent studies have focused on nuclear-encoded circular RNAs (circRNAs) in kidney diseases, but little is known about mitochondrial circRNAs. Differentially expressed circRNAs were analyzed by RNA deep sequencing from lupus nephritis (LN) biopsies and normal human kidneys. In LN renal biopsies, the most downregulated circRNA was circMTND5, which is encoded in the mitochondrial genome. We quantitated circMTND5 by qPCR and localized by fluorescence in situ hybridization (FISH). Mitochondrial abnormalities were identified by electron microscopy. The expression of mitochondrial genes was decreased, and the expression of profibrotic genes was increased on qPCR and immunostaining. RNA binding sites for MIR6812 and circMTND5 were predicted. MIR6812 expression was increased by FISH and qPCR. In HK-2 cells and its mitochondrial fraction, the role of circMTND5 sponging MIR6812 was assessed by their colocalization in mitochondria on FISH, RNA immunoprecipitation, and RNA pulldown coupled with luciferase reporter assay. circMTND5 knockdown upregulated MIR6812, decreased mitochondrial functional gene expression, and increased profibrotic gene expression. Overexpression of circMTND5 reversed these effects in hTGF-β stimulated HK-2 cells. Similar effects were observed in HK-2 cells with overexpression and with knockdown of MIR6812. We conclude that circMTND5 alleviates renal mitochondrial injury and kidney fibrosis by sponging MIR6812 in LN.

Circ_0000064 knockdown attenuates high glucose-induced proliferation, inflammation and extracellular matrix deposition of mesangial cells through miR-424-5p-mediated WNT2B inhibition in cell models of diabetic nephropathy

BACKGROUND

Circular RNA (circRNA) is widely shown to be associated with the development of diabetic nephropathy (DN). Our study aimed to further explore the role of circ_0000064 and provide a new mechanism for its action in DN.

METHODS

Cell models of DN in vitro were constructed by treating human renal mesangial cells (HRMCs) with high glucose (HG). The expression of circ_0000064, microRNA-424-5p (miR-424-5p) and Wnt family member 2B (WNT2B) mRNA was detected by quantitative real-time PCR (qPCR). Cell proliferation was assessed by CCK-8 assay and EdU assay. Cell cycle was characterized by DNA content using flow cytometry. The releases of pro-inflammatory factors were checked using commercial ELISA kits. The expression of cell cycle- and fibrosis-associated proteins was detected by western blot. The interplays between miR-424-5p and circ_0000064 or WNT2B were verified by dual-luciferase reporter assay and RIP assay.

RESULTS

Circ_0000064 and WNT2B were upregulated, while miR-424-5p was downregulated in HG-treated HRMCs. Circ_0000064 knockdown largely attenuated HG-induced proliferation, inflammatory responses and extracellular matrix (ECM) accumulation in HRMCs, and miR-424-5p deficiency reversed the role of circ_0000064 knockdown. MiR-424-5p was a target of circ_0000064, and miR-424-5p directly bound to WNT2B. MiR-424-5p restoration alleviated HG-induced proliferation, inflammatory responses and ECM accumulation in HRMCs, and WNT2B overexpression partially abolished the effects of miR-424-5p.

CONCLUSION

Circ_0000064 knockdown ameliorated HG-induced HRMC dysfunctions through miR-424-5p enrichment-mediated WNT2B inhibition, hinting that circ_0000064 contributed to DN development.

Circ_0114428 promotes proliferation, fibrosis and EMT process of high glucose-induced glomerular mesangial cells through regulating the miR-185-5p/SMAD3 axis

Circular RNA (circRNA) has been confirmed to be the key regulators of diabetic nephropathy (DN) progression. However, the role of circ_0114428 in the DN progression remains unclear. Glomerular mesangial cells (GMCs) were treated with high glucose (HG) to mimic DN cell models in vitro. The expression levels of circ_0114428, microRNA (miR)-185-5p, and SMAD3 mRNA were examined by quantitative real-time PCR. Cell proliferation ability was detected by MTT assay, EdU staining and flow cytometry. The protein levels of proliferation marker, fibrosis markers, epithelial-mesenchymal transition (EMT) markers and SMAD3 were measured by western blot assay. The interaction between miR-185-5p and circ_0114428 or SMAD3 was confirmed via dual-luciferase reporter assay, RIP assay and RNA pull-down assay. Our data showed that circ_0114428 was upregulated in HG-induced GMCs. Circ_0114428 overexpression could aggravate the promotion effect of HG on the proliferation, fibrosis and EMT process of GMCs, while its knockdown had an opposite effect. In the terms of mechanisms, circ_0114428 could sponge miR-185-5p to regulate SMAD3. MiR-185-5p inhibitor could reverse the suppressive effect of circ_0114428 knockdown on the proliferation, fibrosis and EMT process in HG-induced GMCs. Also, SMAD3 overexpression abolished the inhibition of miR-185-5p on the proliferation, fibrosis and EMT process in HG-induced GMCs. Taken together, our data suggested that circ_0114428 might promote DN progression by regulating the miR-185-5p/SMAD3 axis.

lncRNA MALAT1 Promotes Diabetic Nephropathy Progression via miR-15b-5p/TLR4 Signaling Axis

Objective

The long noncoding RNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) are closely associated with the pathogenesis of diabetic nephropathy (DN). But a complete mechanism for MALAT1 in DN has yet to be identified. This study investigated the effect of MALAT1 on DN through the regulation of miR-15b-5p/TLR4 signaling.

Method

Renal tissues were collected from DN patients. Human renal tubular epithelial cells (HK-2) were used as a model of DN induced by high glucose (HG). We then measured the viability, apoptosis, and inflammatory cytokine levels of HK-2 cells using the corresponding assays. Following transfections of si-MALAT1, si-MALAT1+miR-15b-5p inhibitor, or si-MALAT1+vector TLR4 into HG-stimulated HK-2 cells, cell viability, apoptosis, and inflammatory cytokines were again measured. Furthermore, dual-luciferase reporter assay validated the interactions of MALAT1/miR-15b-5p and miR-15b-5p/TLR4. In addition, the interaction between MALAT1 and miR-15b-5p was investigated by RNA immunoprecipitation (RIP).

Results

A significant upregulation of MALAT1 was observed in DN kidney tissues, as well as in HG-stimulated HK-2 cells. MALAT1 knockdown attenuates the inhibition of cell viability, apoptosis, and inflammatory response induced by HG in HK-2 cells. Moreover, a miR-15b-5p inhibitor or TLR4 overexpression reversed the above effects induced by MALAT1 knockdown.

Conclusion

These results indicate that reduced MALAT1 ameliorates HG-stimulated HK-2 cell damage through an inhibition of the miR-15b-5p/TLR4 axis. MALAT1 may serve as a biomarker and potential therapeutic target for DN.

Procyanidin B2 suppresses hyperglycemia‑induced renal mesangial cell dysfunction by modulating CAV‑1‑dependent signaling

The dysfunction of renal mesangial cells (MCs) is a hallmark of diabetic kidney disease (DKD), which triggers glomerulosclerosis leading to end-stage renal disease. Procyanidin B2 (PB2), the main component of proanthocyanidin, is well known for its antioxidant and anti-inflammatory effects; however, it remains unclear as to whether it has protective effects on DKD. The present study investigated the protective effect of PB2 against hyperglycemia-induced renal MC dysfunction in mouse SV40-Mes13 (Mes13) cells. The Mes13 cells were treated with or without PB2 under HG conditions. Cell proliferation was assessed using an MTT assay and oxidative stress was assessed by examining intracellular ROS generation and H₂O₂ production. The changes in extracellular matrix accumulation- and cellular inflammation-related proteins were measured by western blot analysis, ELISA and immunofluorescence analysis. The results showed that PB2 treatment markedly attenuated hyperglycemia-induced cell proliferation, oxidative stress, extracellular matrix accumulation and cellular inflammation in Mes13 cells, which was accompanied by an inactivation of redoxosomes, TGF-β1/SMAD and IL-1β/TNF-α/NF-κB signaling pathways. The present study also demonstrated that hyperglycemia upregulated and activated caveolin-1 (CAV-1), whereas PB2 treatment potently reversed this effect. In accordance, CAV-1 overexpression abolished the protective effects of PB2 against hyperglycemia in Mes13 cells, indicating that the cytoprotective effect of PB2 was CAV-1-dependent. These findings form the basis of the potential clinical applications of PB2 in the treatment of DKD.

Mechanistic Pathogenesis of Endothelial Dysfunction in Diabetic Nephropathy and Retinopathy

Diabetic nephropathy (DN) and diabetic retinopathy (DR) are microvascular complications of diabetes. Microvascular endothelial cells are thought to be the major targets of hyperglycemic injury. In diabetic microvasculature, the intracellular hyperglycemia causes damages to the vascular endothelium, via multiple pathophysiological process consist of inflammation, endothelial cell crosstalk with podocytes/pericytes and exosomes. In addition, DN and DR diseases development are involved in several critical regulators including the cell adhesion molecules (CAMs), the vascular endothelial growth factor (VEGF) family and the Notch signal. The present review attempts to gain a deeper understanding of the pathogenesis complexities underlying the endothelial dysfunction in diabetes diabetic and retinopathy, contributing to the development of new mechanistic therapeutic strategies against diabetes-induced microvascular endothelial dysfunction.

Long Non-Coding RNAs in the Pathogenesis of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is one of the major microvascular complications of diabetes mellitus, with relatively high morbidity and mortality globally but still in short therapeutic options. Over the decades, a large body of data has demonstrated that oxidative stress, inflammatory responses, and hemodynamic disorders might exert critical influence in the initiation and development of DKD, whereas the delicate pathogenesis of DKD remains profoundly elusive. Recently, long non-coding RNAs (lncRNAs), extensively studied in the field of cancer, are attracting increasing attentions on the development of diabetes mellitus and its complications including DKD, diabetic retinopathy, and diabetic cardiomyopathy. In this review, we chiefly focused on abnormal expression and function of lncRNAs in major resident cells (mesangial cell, endothelial cell, podocyte, and tubular epithelial cell) in the kidney, summarized the critical roles of lncRNAs in the pathogenesis of DKD, and elaborated their potential therapeutic significance, in order to advance our knowledge in this field, which might help in future research and clinical treatment for the disease.

lncRNA LINC00284 promotes nucleus pulposus cell proliferation and ECM synthesis via regulation of the miR‑205‑3p/Wnt/β‑catenin axis

Intervertebral disc degeneration (IDD) is a leading cause of degenerative spinal disease. Long non-coding RNA (lncRNA) LINC00284 is overexpressed in multiple types of cancer and promotes cancer cell proliferation and inhibits apoptosis; however, its role in human IDD and nucleus pulposus (NP) remain unclear. In the present study, intervertebral disc (IVD) tissues were collected from IDD patients for detection of LINC00284 expression using reverse transcription-quantitative PCR, the binding effect between miR-205-3p and LINC00284 was validated by dual-luciferase reporter assay. miR-205-3p and small interfering RNA (siRNA) was used for LINC00240 knockdown to investigate the proliferation, apoptosis of cells in the NP cells measured by Cell Counting Kit (CCK)-8 assay and Annexin V-FITC/Propidium Iodide (PI) staining with flow cytometry receptivity. IDD animal models were constructed for in vivo study of the role LINC00284 in IDD improvement. The results showed that LINC00284 expression was upregulated in IDD tissue and IL-1β-induced NP cells. LINC00284 knockdown resulted in an increase in IL-1β-induced NP cell proliferation, a decrease in apoptosis and matrix metalloproteinase-3 expression and an increase in expression of extracellular matrix (ECM) markers aggrecan and collagen II. In vivo experiments and histomorphometric analysis confirmed the protective effect of LINC00284 knockdown in IDD. LINC00284 was also shown to be a target of microRNA (miR)-205-3p, and there was a negative correlation between LINC00284 and miR-205-3p levels in IDD tissue. Additionally, LINC00284 knockdown or miR-205-3p upregulation resulted in inhibition of Wnt/β-catenin signaling and subsequent degradation of the ECM. The present study demonstrated that LINC00284 activated the Wnt/β-catenin signaling via sponging miR-205-3p, resulting in inhibition of NP cell proliferation and ECM synthesis. These results suggested that targeting LINC00284 to rescue miR-205-3p expression may be a potential method for IDD management.

Danhong injection represses diabetic retinopathy and nephropathy advancement in diabetic mice by upregulating microRNA-30d-5p and targeting JAK1

Danhong injection (DHI) restrains diabetic retinopathy and nephropathy (DR and DN) advancement in diabetic mice. However, the downstream mechanism of its modulation is not fully studied. Diabetic model mice (db/db mice) were intravenously injected with DHI and corresponding virus particles. MiR-30d-5p and JAK1 were detected. The body weight and fasting blood glucose mice were measured every 4 weeks. The renal tissues and serum of mice were collected, and the contents of creatinine and blood urea nitrogen were biochemically analyzed. IL-6, IFN-γ and TNF-α were detected by ELISA, with the pathological conditions of renal tissues in mice by He staining, and the adjustment conditions by TUNEL. Human retinal pigment epithelium (ARPE-19) cells were selected to induce DR model in vitro by high glucose, and exposed to DHI for treatment. The corresponding plasmids were transfected, and miR-30d-5p and JAK1 were detected, with the proliferation ability by plate cloning, apoptosis by flow cytometry, and cell migration ability by Transwell. The angiogenesis ability of cells was assessed by tube formation assay. The targeting relationship between miR-30d-5p and JAK1 was detected. The results manifested that miR-30d-5p was declined in DR and DN, while JAK1 expression was elevated. DHI was able to improve DR and renal injury. DHI could regulate the miR-30d-5p-JAK1 axis in vivo, and miR-30d-5p targeted and regulated JAK1. Upregulation of miR-30d-5p or inhibition of JAK1 could improve DR and renal injury. The results implies that DHI can repress the development of DR and DN by elevating miR-30d-5p and targeting JAK1.

Microarray Analysis Reveals the Changes in Circular RNA Expression and Molecular Mechanisms in Mice With Ventilator-Induced Lung Injury

Circular RNA (circRNA) expression profiles in lung tissues from mice with and without ventilator-induced lung injury (VILI) were analyzed using high-throughput sequencing and bioinformatics to clarify their potential role in VILI pathogenesis and provide valuable molecular markers for VILI diagnosis and treatment. A VILI mouse model was established using high-tidal volume ventilation, and lung tissue was stained with HE and TUNEL. The present study used high-throughput sequencing technology to analyze the expression profile of circRNAs in the lung tissue of mice with and without VILI. Bioinformatics was used to analyze the enrichment of differentially expressed circRNAs using Gene Ontology and KEGG to predict function. Among the top 10 circRNAs with significant differential expression, we used real-time quantitative polymerase chain reaction technology (qRT-PCR) to verify the accuracy of the high-throughput sequencing results and constructed the corresponding circRNA-miRNA-mRNA-specific binding network map using software prediction. The most upregulated circRNAs were novel_circ_0000899 and novel_circ_0014815, and the most downregulated circRNAs were novel_circ_0015069. A total of 14,347 circRNAs were detected using high-throughput sequencing. Compared to the control group, 285 circRNAs were abnormally and significantly expressed in the lung tissues of VILI mice (|log2(FC)| > 1, p < 0.05). A total of 171 circRNAs were significantly upregulated, and 114 circRNAs were significantly downregulated. Gene ontology analyses indicated that the differentially expressed circRNAs were involved in multiple biological functions, such as regulation of metabolic processes, protein phosphorylation, and chromatin organization. KEGG pathway analyses revealed that the Ras signaling pathway, rap1 signaling pathway, PI3K − Akt signaling pathway, and ECM receiver interaction were related to the differentially expressed circRNAs. The qRT-PCR verification results were generally consistent with the circRNA expression trends of the high-throughput sequencing data. The circRNA-miRNA-mRNA interaction network suggested that miRNAs and mRNAs related to circRNAs played a key role in VILI. Differentially expressed circRNAs were identified in the tissues of VILI mice using high-throughput sequencing combined with bioinformatics analysis, and the results lay a foundation for further study of the mechanism of circRNAs in the occurrence and development of VILI.

Ameliorating role of microRNA-378 carried by umbilical cord mesenchymal stem cells-released extracellular vesicles in mesangial proliferative glomerulonephritis

BACKGROUND

Mesenchymal stem cells (MSCs) and their released extracellular vesicles (Evs) have shown protective effects against kidney diseases. This study aims to study the functions of umbilical cord MSCs-released Evs (ucMSC-Evs) and their implicated molecules in mesangial proliferative glomerulonephritis (MsPGN).

METHODS

A rat model of MsPGN was induced by anti-Thy-1.1, and rat mesangial cells (rMCs) HBZY-1 were treated with PDGF-BB/DD to mimic MsPGN condition in vitro. Rats and cells were treated with different doses of ucMSC-Evs, and then the pathological changes in renal tissues and proliferation of rMCs were determined. Differentially expressed microRNAs (miRNAs) after Evs treatment were screened by microarray analysis. The interactions among miR-378, PSMD14, and TGFBR1 were analyzed. Gain- and loss-of function studies of miR-378 and PSMD14 were performed to explore their effects on tissue hyperplasia and rMC proliferation and their interactions with the TGF-β1/Smad2/3 signaling pathway.

RESULTS

The ucMSC-Evs treatment ameliorated mesangial hyperplasia and fibrosis in rat renal tissues and suppressed the aberrant proliferation of rMCs in a dose-dependent manner. miR-378 was the most upregulated miRNA in tissues and cells after ucMSC-Evs treatment. miR-378 directly targeted PSMD14, and PSMD14 maintained the stability of TGFBR1 through deubiquitination modification, which led to TGF-β1/Smad2/3 activation. Either miR-378 knockdown or PSMD14 overexpression diminished the protective functions of ucMSC-Evs by activating the TGF-β1/Smad2/3 signaling pathway.

CONCLUSION

UcMSC-Evs ameliorate pathological process in MsPGN through the delivery of miR-378, which suppresses PSMD14-mediated TGFBR1 stability and inactivates the TGF-β1/Smad2/3 signaling pathway to reduce tissue hyperplasia and rMC proliferation. Video abstract.

Hypercalciuria switches Ca2+ signaling in proximal tubular cells, induces oxidative damage to promote calcium nephrolithiasis

Proximal tubule (PT) transports most of the renal Ca2+, which was usually described as paracellular (passive). We found a regulated Ca2+ entry pathway in PT cells via the apical transient receptor potential canonical 3 (TRPC3) channel, which initiates transcellular Ca2+ transport. Although TRPC3 knockout (-/-) mice were mildly hypercalciuric and displayed luminal calcium phosphate (CaP) crystals at Loop of Henle (LOH), no CaP + calcium oxalate (CaOx) mixed urine crystals were spotted, which are mostly found in calcium nephrolithiasis (CaNL). Thus, we used oral calcium gluconate (CaG; 2%) to raise the PT luminal [Ca2+]o further in TRPC3 -/- mice for developing such mixed stones to understand the mechanistic role of PT-Ca2+ signaling in CaNL. Expectedly, CaG-treated mice urine samples presented with numerous mixed crystals with remains of PT cells, which were pronounced in TRPC3 -/- mice, indicating PT cell damage. Notably, PT cells from CaG-treated groups switched their mode of Ca2+ entry from receptor-operated to store-operated pathway with a sustained rise in intracellular [Ca2+] ([Ca2+]i), indicating the stagnation in PT Ca2+ transport. Moreover, those PT cells from CaG-treated groups demonstrated an upregulation of calcification, inflammation, fibrotic, oxidative stress, and apoptotic genes; effects of which were more robust in TRPC3 ablated condition. Furthermore, kidneys from CaG-treated groups exhibited fibrosis, tubular injury and calcifications with significant reactive oxygen species generation in the urine, thus, indicating in vivo CaNL. Taken together, excess PT luminal Ca2+ due to escalation of hypercalciuria in TRPC3 ablated mice induced surplus CaP crystal formation and caused stagnation of PT [Ca2+]i, invoking PT cell injury, hence mixed stone formation.

LncRNA HOTAIR facilitates high glucose-induced mesangial cell proliferation, fibrosis and oxidative stress in diabetic nephropathy via regulating miR-147a/WNT2B axis

BACKGROUND

Long non-coding RNAs (lncRNAs) have been shown to be involved in the regulation of many disease progression. However, the role of lncRNA HOX transcript antisense RNA (HOTAIR) in diabetic nephropathy (DN) remains unclear.

METHODS

High glucose (HG)-induced human mesangial cells (HMC) was used to construct DN cell models in vitro. HMC proliferation was evaluated by CCK8 assay and EDU staining. Protein levels of proliferation markers, fibrosis markers, and wingless-type family member 2B (WNT2B) were measured using western blot analysis. HMC oxidative stress was assessed by determining the levels of oxygen species and malondialdehyde, as well as superoxide dismutase activity. Relative expression levels of lncRNA HOTAIR, microRNA (miR)-147a, and WNT2B were examined using quantitative real-time PCR. The interaction between miR-147a and lncRNA HOTAIR or WNT2B was confirmed by dual-luciferase reporter assay and RIP assay.

RESULTS

Our data showed that lncRNA HOTAIR knockdown could inhibit the proliferation, fibrosis, and oxidative stress in HG-induced HMC. LncRNA HOTAIR could serve as a sponge of miR-147a. The inhibition effect of lncRNA HOTAIR silencing on the biological functions of HG-induced HMC could be reversed by miR-147a inhibitor. WNT2B was targeted by miR-147a, and its overexpression also overturned the suppressive effect of miR-147a on the proliferation, fibrosis, and oxidative stress of HG-induced HMC.

CONCLUSION

In total, our research pointed out that lncRNA HOTAIR could mediate miR-147a/WNT2B axis to promote DN progression.

Exosomal circTAOK1 contributes to diabetic kidney disease progression through regulating SMAD3 expression by sponging miR-520h

BACKGROUND

Diabetic nephropathy (DN) is a frequent diabetes complication with complex pathogenesis. Circular RNA (circRNA) circTAOK1 (also named circ_0003928) has been reported to be upregulated in high glucose (HG)-treated human umbilical vein endothelial cells. Also, exosomal circRNAs can exert significant roles in the pathology of various diseases. This study is designed to explore the role and mechanism of exosomal circTAOK1 on the glomerular mesangial cell (GMC) injury in DN.

METHODS

Exosomes were detected by a transmission electron microscope. The protein levels of CD9, CD63, proliferating cell nuclear antigen (PCNA), cyclinD1, α-SMA, fibronectin, E-cadherin, N-cadherin, and SMAD family member 3 (SMAD3) were examined by western blot assay. circTAOK1, microRNA-520h (miR-520h), and SMAD3 levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell proliferation and cell cycle progression were detected by cell counting kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), and flow cytometry assays. The binding relationship between miR-520h and circTAOK1 or SMAD3 was predicted by Starbase and then verified by a dual-luciferase reporter and RNA immunoprecipitation (RIP), RNA pull-down assays.

RESULTS

CircTAOK1 expression was upregulated in the exosomes isolated from HG-treated glomerular epithelial cells (GEC). Moreover, GEC-circTAOK1-Exo could promote proliferation, fibrosis, and epithelial-mesenchymal transition (EMT) of glomerular mesangial cells (GMCs). Mechanically, circTAOK1 could regulate SMAD3 expression by sponging miR-520h, GEO-si-circTAOK1 Exo-induced miR-520h and repressed SMAD3 expression in GMC.

CONCLUSION

GEC-circTAOK1-Exo could boost proliferation, fibrosis, and EMT of GMC through targeting the miR-520h/SMAD3 axis, providing new insights into the pathogenesis of DN.

ENSMUST00000147869 regulates proliferation and fibrosis of mesangial cells in diabetic nephropathy by interacting with Hspa9

AIMS

Our previous study showed that ENSMUST00000147869 was abnormally low expressed in the early stage of diabetic nephropathy (DN). ENSMUST00000147869 could inhibit the fibrosis and proliferation of mouse mesangial cells (MMCs), but the mechanism is still unclear. This study aims to explore the specific mechanism underline ENSMUST00000147869 regulates the proliferation and fibrosis of MMCs in DN.

METHODS

Nucleocytoplasmic fractionation was applied to define the location of ENSMUST00000147869 in MMCs. RNA-protein pulldown, RNA immunoprecipitation and mass spectrometry were used to identify upregulated Hspa9 directly interacting with ENSMUST00000147869. SiRNA and lentivirus packaging were used to clarify the role of Hspa9 downregulated by ENSMUST00000147869 in promoting proliferation and fibrosis in MMCs. CHX and MG132 were used to clarify the regulatory role of ENSMUST00000147869 to Hspa9. Immunoprecipitation confirmed the binding of Hspa9 and HMGB1.

RESULTS

HSPA9 was a direct binding protein of ENSMUST00000147869, and ENSMUST00000147869 could inhibit proliferation and fibrosis of MMCs by down-regulating HSPA9 through ubiquitination process. HMGB1 was the downstream binding protein of Hspa9, and ENSMUST00000147869 could inhibit the interaction between Hspa9 and HMGB1.

CONCLUSION

Our data showed that ENSMUST00000147869 regulates Hspa9 through the ubiquitin proteasome pathway, and inhibits the binding of Hspa9 and HMGB1. ENSMUST00000147869/Hspa9/HMGB1 axis may act as a diagnostic molecular marker and an effective therapeutic target for DN. This article is protected by copyright. All rights reserved.

The HDAC2/SP1/miR-205 feedback loop contributes to tubular epithelial cell extracellular matrix production in diabetic kidney disease

Extracellular matrix (ECM) accumulation is considered an important pathological feature of diabetic kidney disease (DKD). Histone deacetylase (HDAC) inhibitors protect against kidney injury. However, the potential mechanisms of HDACs in DKD are still largely unknown. Here, we describe a novel feedback loop composed of HDAC2 and miR-205 that regulates ECM production in tubular epithelial cells in individuals with DKD. We found that HDAC2 mRNA expression in peripheral blood was markedly higher in patients with DKD than in patients with diabetes. Nuclear HDAC2 protein expression was increased in TGFβ1-stimulated tubular epithelial cells and db/db mice. We also found that miR-205 was regulated by HDAC2 and downregulated in TGFβ1-treated HK2 cells and db/db mice. In addition, HDAC2 reduced histone H3K9 acetylation in the miR-205 promoter region to inhibit its promoter activity and subsequently suppressed miR-205 expression through an SP1-mediated pathway. Furthermore, miR-205 directly targeted HDAC2 and inhibited HDAC2 expression. Intriguingly, miR-205 also regulated its own transcription by inhibiting HDAC2 and increasing histone H3K9 acetylation in its promoter, forming a feedback regulatory loop. Additionally, the miR-205 agonist attenuated ECM production in HK2 cells and renal interstitial fibrosis in db/db mice. In conclusion, the HDAC2/SP1/miR-205 feedback loop may be crucial for the pathogenesis of DKD.

Circular RNAs in Diabetic Nephropathy: Updates and Perspectives

Circular RNAs (circRNAs) are widespread endogenous transcripts lacking 5′-caps and 3′-polyadenylation tails. Their closed-loop structure confers exonuclease resistance and extreme stability. CircRNAs play essential roles in various diseases, including diabetes. Diabetic nephropathy (DN) is the leading cause of end-stage kidney disease and is one of the most common complications of diabetes. CircRNAs are key in DN and therefore important for understanding DN pathophysiology and developing new therapeutic strategies. In the present review, we briefly introduce the characteristics and functions of circRNAs and summarize recent discoveries on how circRNAs participate in DN. Based on these advances, we suggest future perspectives for studying circRNAs in DN to improve DN treatment and management.

The DR1‑CSE/H2S system inhibits renal fibrosis by downregulating the ERK1/2 signaling pathway in diabetic mice

Glomerular mesangial cell (MC) proliferation and extracellular matrix deposition are the main pathological changes in diabetic nephropathy. Hydrogen sulfide (H2S) inhibits the proliferation of MCs. Dopamine 1 receptors (DR1) are expressed in MCs and serve important physiological roles. However, it is unclear whether DR1 activation inhibits MC proliferation by increasing endogenous H2S. The present study found that the production of H2S and the expression of DR1 and cystathionine‑γ‑lyase (CSE) were decreased in the renal tissues of diabetic mice and high glucose (HG)‑induced MCs. SKF38393 (a DR1 agonist) increased the production of H2S and the expression of DR1 and CSE and NaHS (an exogenous H2S donor) only increased H2S production and CSE expression but not DR1 expression. HG increased the thickness of the glomerular basement membrane, cell viability and proliferation, the expression of cyclin D1, PCNA, collagen 1 and α‑smooth muscle actin and the activity of phosphorylated ERK1/2 and decreased the expression of P21 and MMP9. SKF38393 and NaHS reversed the effects of HG. PPG (a CSE inhibitor) abolished the beneficial effects of SKF38393. The beneficial effects of SKF38393 were similar to those of PD98059 (an ERK1/2 inhibitor). Taken together, the findings suggested that the DR1‑CSE/H2S pathway activation attenuated diabetic MC proliferation and extracellular matrix deposition by downregulating the ERK1/2 signaling pathway.

Peripheral Blood circRNA Microarray Profiling Identities hsa_circ_0001831 and hsa_circ_0000867 as Two Novel circRNA Biomarkers for Early Type 2 Diabetic Nephropathy

PURPOSE

Type 2 diabetes mellitus (T2DM) increases the incidence of diabetic nephropathy (DN) and eventually progresses to end-stage renal disease. Circular RNAs (circRNAs) are a class of non-coding RNAs that are promising as diagnostic biomarkers and therapeutic targets for human diseases. The aim of this study was to analyze the differential expression of circRNAs (DECs) in peripheral blood from patients with early type 2 diabetic nephropathy (ET2DN), T2DM and controls, which will facilitate to discover some new biomarkers for ET2DN.

PATIENTS AND METHODS

Twenty ET2DN patients, 20 T2DM patients, and 20 normal controls were included in this study. Blood samples from 3 random subjects of age- and sex-matched patients in each group, respectively, were used to detect circRNA expression profiles by circRNA microarray, and the circRNA expression of remaining subjects was validated by real-time quantitative polymerase chain reaction (qRT-PCR). Further functional assessment was performed by bioinformatic tools.

RESULTS

There were 586 DECs in ET2DN vs T2DM group (249 circRNAs were upregulated and 337 circRNAs were downregulated); 176 circRNAs were upregulated and 101 circRNAs were downregulated in T2DM vs control group; 57 circRNAs were upregulated and 5 circRNAs were downregulated in ET2DN vs control group. The functional and pathway enrichment of DECs were analyzed by GO and KEGG. qRT-PCR results revealed that hsa_circ_0001831 and hsa_circ_0000867 were significantly upregulated in ET2DN group compared to both of T2DM and control group. The ROC curve demonstrated that hsa_circ_0001831 and hsa_circ_0000867 have high sensitivity and specificity associated with ET2DN.

CONCLUSION

Our study showed the expression profiles of circRNAs in ET2DN patients and demonstrated that hsa_circ_0001831 and hsa_circ_0000867 can be used as novel diagnostic biomarkers for ET2DN.

Circular RNAs in diabetes mellitus and its complications

Diabetes mellitus (DM) is an endocrine disorder characterized by a relative or absolute lack of insulin due to the dysfunction or destruction of β-cells. DM is one of the fastest growing challenges to global health in the 21^st century and places a tremendous burden on affected individuals and their families and countries. Although insulin and antidiabetic drugs have been used to treat DM, a radical cure for the disease is unavailable. The pathogenesis of DM remains unclear. Emerging roles of circular RNAs (circRNAs) in DM have become a subject of global research. CircRNAs have been verified to participate in the onset and progression of DM, implying their potential roles as novel biomarkers and treatment tools. In the present review, we briefly introduce the characteristics of circRNAs. Next, we focus on specific roles of circRNAs in type 1 diabetes mellitus, type 2 diabetes mellitus, gestational diabetes mellitus and diabetes-associated complications.

MiR-153-3p reduces extracellular matrix accumulation in high glucose-stimulated human glomerular mesangial cells via targeting PAQR3 in diabetic nephropathy

INTRODUCTION

This study aims to explore the effect and related molecular mechanism of miR-153-3p on high glucose-stimulated human glomerular mesangial cells.

MATERIALS AND METHODS

The quantitative real-time polymerase chain reaction (qPCR) assay was employed to check miR-153-3p and PAQR3 expression levels in diabetic nephropathy patients. (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) MTT assay was applied to investigate the effects of miR-153-3p transfection or PAQR3 administration on mesangial cell (MC) activity. ELISA assays were used to check the expression levels of extracellular matrix (ECM) related proteins. The bioinformatics method and dual-luciferase reporter assay were employed together to anticipate and check the targeting relationship between miR-153-3p and PAQR3. Western blot assays were applied to check the PAQR3, PI3K and AKT expression after miR-153-3p transfection or PAQR3 administration.

RESULTS

The expression level of miR-153-3p was lower in diabetic nephropathy patients, while the expression of PAQR3 was concomitantly higher. Upregulation of miR-153-3p can reduce MC proliferation and ECM accumulation. Further research indicated that miR-153-3p directly regulated PAQR3 expression via coupling with the 3'-UTR of PAQR3. Finally, the fact that miR-153-3p regulates the PI3K/AKT pathway by PAQR3 was confirmed.

CONCLUSION

MiR-153-3p regulates the PI3K/AKT pathway through PAQR3, thereby playing a role in regulating cell proliferation and ECM accumulation in high glucose-stimulated MCs.

Exosomal hsa_circ_0125310 promotes cell proliferation and fibrosis in diabetic nephropathy via sponging miR-422a and targeting the IGF1R/p38 axis

Diabetic nephropathy (DN) is still on the rise worldwide, and millions of patients have to be treated through dialysis or transplant because of kidney failure caused by DN. Recent reports have highlighted circRNAs in the treatment of DN. Herein, we aimed to investigate the mechanism by which high glucose‐induced exo‐circ_0125310 promotes diabetic nephropathy progression. circ_0125310 is highly expressed in diabetic nephropathy and exosomes isolated from high glucose‐induced mesangial cells (MCs). High glucose‐induced exosomes promote the proliferation and fibrosis of MCs. However, results showed that the effects of exosomes on MCs can be reversed by the knockdown of circ_0125310. miR‐422a, which targets IGF1R, was the direct target of circ_0125310. circ_0125310 regulated IGF1R/p38 axis by sponging miR‐422a. Exo‐circ_0125310 increased the luciferase activity of the WT‐IGF1R reporter in the dual‐luciferase reporter gene assays and upregulated the expression level of IGF1R and p38. Finally, in vivo research indicated that the overexpression of circ_0125310 promoted the diabetic nephropathy progression. Above results demonstrated that the high glucose‐induced exo‐circ_0125310 promoted cell proliferation and fibrosis in diabetic nephropathy via sponging miR‐422a and targeting the IGF1R/p38 axis.

CircSMAD4 alleviates high glucose-induced inflammation, extracellular matrix deposition and apoptosis in mouse glomerulus mesangial cells by relieving miR-377-3p-mediated BMP7 inhibition

BACKGROUND

Diabetic nephropathy (DN) is a common complication of diabetes mellitus. Accumulating studies suggest that the deregulation of circular RNA (circRNA) is involved in DN pathogenesis. This study aimed to investigate the role of circSMAD4 in DN models.

METHODS

Mice were treated with streptozotocin to establish DN models in vivo. Mouse glomerulus mesangial cells (SV40-MES13) were treated with high glucose to establish DN models in vitro. The expression of circSMAD4, miR-377-3p and bone morphogenetic protein 7 (BMP7) mRNA was measured by quantitative real-time PCR (qPCR). The releases of inflammatory factors were examined by ELISA. The protein levels of fibrosis-related markers, apoptosis-related markers and BMP7 were checked by western blot. Cell apoptosis was monitored by flow cytometry assay. The predicted relationship between miR-377-3p and circSMAD4 or BMP7 was validated by dual-luciferase reporter assay or pull-down assay.

RESULTS

CircSMAD4 was poorly expressed in DN mice and HG-treated SV40-MES13 cells. HG induced SV40-MES13 cell inflammation, extracellular matrix (ECM) deposition and apoptosis. CircSMAD4 overexpression alleviated, while circSMAD4 knockdown aggravated HG-induced SV40-MES13 cell injuries. MiR-377-3p was targeted by circSMAD4, and miR-377-3p enrichment partly reversed the effects of circSMAD4 overexpression. BMP7 was a target of miR-377-3p, and circSMAD4 regulated BMP7 expression by targeting miR-377-3p. MiR-377-3p overexpression aggravated HG-induced injuries by suppressing BMP7.

CONCLUSION

CircSMAD4 alleviates HG-induced SV40-MES13 cell inflammation, ECM deposition and apoptosis by relieving miR-377-3p-mediated inhibition on BMP7 in DN progression.

Hyperglycemia-induced accumulation of advanced glycosylation end products in fibroblast-like synoviocytes promotes knee osteoarthritis

Osteoarthritis (OA) is significantly associated with diabetes, but how hyperglycemia induces or aggravates OA has not been shown. The synovium plays a critical role in cartilage metabolism and substance exchange. Herein, we intended to investigate whether and how hyperglycemia affects the occurrence and progression of OA by influencing the synovium. In patients with knee OA and diabetes (DM OA), we found a more severe inflammatory response, higher endoplasmic reticulum stress (ERS) levels, and more advanced glycosylation end products (AGEs) accumulation in the synovium than in patients without diabetes. Subsequently, we found similar results in the DM OA group in a rat model. In the in vitro cocultivation system, high glucose-stimulated AGEs accumulation, ERS, and inflammation in rat fibroblast-like synoviocytes (FLSs), which resulted in chondrocyte degeneration due to inflammatory factors from FLSs. Furthermore, in the synovium of the DM OA group and FLSs treated with high glucose, the expression of glucose transporter 1 (GLUT1) and its regulatory factor hypoxia-inducible factor (HIF)-1α was increased significantly. Inhibitors of HIF-1α, GLUT1 or AGEs receptors attenuated the effect of high glucose on chondrocyte degradation in the FLS-chondrocyte coculture system. In summary, we demonstrated that hyperglycemia caused AGEs accumulation in FLSs via the HIF-1α-GLUT1 pathway, which increases the release of inflammatory factors from FLSs, subsequently inducing chondrocyte degradation and promoting OA progression.

CircTLK1 Downregulation Attenuates High Glucose-Induced Human Mesangial Cell Injury by Blocking the AKT/NF-κB Pathway Through Sponging miR-126-5p/miR-204-5p

Diabetic nephropathy (DN) is the main cause of end-stage renal disease. Circular RNA hsa_circ_0004442 (circTLK1) accelerates the progression of renal cell carcinoma. However, the role of circTLK1 in DN pathogenesis is indistinct. The expression of circTLK1, microRNA-126-5p (miR-126-5p), and microRNA-204-5p (miR-204-5p) was tested by quantitative real-time polymerase chain reaction. The levels of interleukin-6 and interleukin-1β were measured by enzyme-linked immunosorbent assay. The levels of reactive oxygen species and malondialdehyde and the activity of superoxide dismutase were determined with corresponding kits. Several protein levels were evaluated with western blotting. The relationship between circTLK1 and miR-126-5p/miR-204-5p was verified by dual-luciferase reporter assay. CircTLK1 was highly expressed in DN patient's serum and high-glucose (HG)-treated human mesangial cells. Functionally, circTLK1 inhibition reduced HG-induced inflammation, oxidative stress, and ECM accumulation in human mesangial cells. CircTLK1 was verified as a sponge for miR-126-5p and miR-204-5p, which were downregulated in DN patient's serum and HG-treated human mesangial cells. Both miR-126-5p and miR-204-5p upregulation decreased inflammation, oxidative stress, and ECM accumulation in HG-treated human mesangial cells and circTLK1 silencing-mediated influence on HG-induced human mesangial cell injury was overturned by miR-126-5p or miR-204-5p inhibition. Moreover, circTLK1 knockdown blocked the AKT/NF-κB pathway by sponging miR-126-5p/miR-204-5p. CircTLK1 downregulation alleviated HG-induced inflammation, oxidative stress, and ECM accumulation through blocking the AKT/NF-κB pathway via sponging miR-126-5p/miR-204-5p, providing a new mechanism to comprehend the pathogenesis of DN.

Circular RNA circ_0000712 regulates high glucose-induced apoptosis, inflammation, oxidative stress, and fibrosis in (DN) by targeting the miR-879-5p/SOX6 axis

Diabetic nephropathy (DN), a frequent diabetes complication, has complex pathogenesis. Circular RNAs (circRNAs) circ_0000712 has been reported to be upregulated in kidney tissues and high glucose (HG)-inducted Mesangial cells (MCs). This study is designed to explore the role and mechanism of circ_0000712 in the HG-inducted MCs injury in DN. Circ_0000712, microRNA-879-5p (miR-879-5p), and SRY-Box Transcription Factor 6 (SOX6) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell apoptosis was examined by flow cytometry assay. Protein levels of B-cell lymphoma-2 (Bcl-2), Bcl-2 related X protein (Bax), fibronectin (FN), collagen type I (Col. I), collagen type IV (Col. IV), and SOX6 were assessed by western blot assay. Levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α) were measured by enzyme-linked immunosorbent assay (ELISA). Reactive oxygen species (ROS) generation, Lactate Dehydrogenase (LDH) activity, and Superoxide Dismutase (SOD) activity were detected by the corresponding kits. The binding relationship between miR-879-5p and circ_0000712 or SOX6 was predicted by starBase and Targetscan, and then verified by a dual-luciferase reporter and RNA Immunoprecipitation (RIP) assays. Circ_0000712 and SOX6 were highly expressed, and miR-879-5p was decreased in db/db DN mice and HG-inducted SV40-MES13 cells. Furthermore, circ_0000712 deficiency repressed HG-caused apoptosis, inflammation, oxidative stress, and fibrosis in SV40-MES13 cells. Mechanically, circ_0000712 could regulate SOX6 expression by sponging miR-879-5p. Circ_0000712 knockdown could hinder HG-inducted SV40-MES13 cell injury through targeting the miR-879-5p/SOX6 axis, implying a possible circRNA-targeted therapy for DN.

Circular RNAs; powerful microRNA sponges to overcome diabetic nephropathy

Diabetic nephropathy (DN), also known as diabetic kidney disease (DKD), is a drastic renal complication of type 1 and type 2 diabetes mellitus (DM). Poorly controlled DM over the years, may disrupt kidneys' blood vessels, leading to the hypertension (HTN) and DN onset. During DN, kidneys' waste filtering ability becomes disturbed. Being on a healthy lifestyle and controlling both DM and HTN are now the best proceedings to prevent or at least delay DN occurrence. Unfortunately, about one-fourth of diabetic individuals eventually experience the corresponding renal failure, and thus it is critical to discover effective diagnostic biomarkers and therapeutic strategies to combat DN. In the past few years, circular RNAs (circRNAs), as covalently closed endogenous non-coding RNAs (ncRNAs), are believed to affect DN pathogenesis in a positive manner. CircRNAs are able to impact different cellular processes and signaling pathways by targeting biological molecules or various molecular mechanisms. Still, as a key regulatory axis, circRNAs can select miRNAs as their molecular targets, in which they are considered as miRNA sponges. In this way, circRNA-induced suppression of particular miRNAs may prevent from DN progression or promotes the DN elimination. Since the expression of circRNAs has also been reported to be increased in DN-associated cells and tissues, they can be employed as either diagnostic biomarkers or therapeutic targets.

Circular RNAs as Novel Diagnostic Biomarkers and Therapeutic Targets in Kidney Disease

Circular RNAs (circRNAs) are a novel type of non-coding RNAs that have aroused growing attention in this decade. They are widely expressed in eukaryotes and generally have high stability owing to their special closed-loop structure. Many circRNAs are abundant, evolutionarily conserved, and exhibit cell-type-specific and tissue-specific expression patterns. Mounting evidence suggests that circRNAs have regulatory potency for gene expression by acting as microRNA sponges, interacting with proteins, regulating transcription, or directly undergoing translation. Dysregulated expression of circRNAs were found in many pathological conditions and contribute to the pathogenesis and progression of various disorders, including renal diseases. Recent studies have revealed that circRNAs may serve as novel reliable biomarkers for the diagnosis and prognosis prediction of multiple kidney diseases, such as renal cell carcinoma (RCC), acute kidney injury (AKI), diabetic kidney disease (DKD), and other glomerular diseases. Furthermore, circRNAs expressed by intrinsic kidney cells are shown to play a substantial role in kidney injury, mostly reported in DKD and RCC. Herein, we review the biogenesis and biological functions of circRNAs, and summarize their roles as promising biomarkers and therapeutic targets in common kidney diseases.