Blood TGF-β1 and miRNA-21-5p levels predict renal fibrosis and outcome in IgA nephropathy

New biomarkers in IgA nephropathy

Currently, IgA nephropathy (IgAN) is the most common cause of chronic renal failure in patients with primary glomerulonephritis. However, IgAN diagnosis is usually performed by collecting a renal biopsy as gold standard to visualize pathological changes in the glomeruli. The randomized nature of this invasive procedure in clinical practice, together with the need to exclude patients with contraindications, often results in a limited number of eligible people. Therefore, over the past two decades, researchers have explored new biomarkers for IgAN to meet the urgent clinical need for rapid diagnosis and prognosis, as well as realistic prediction of IgAN progression. In addition to traditional common markers with low specificity to detect renal diseases, the classical antibody targeting galactose-deficient IgA1 has been progressively discovered. In addition, new types of diagnostic or prognostic biomarkers are emerging, including microRNA, complement factors, proteases, inflammatory molecules and serum or urinary metabolite profiles.

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.

Diagnostic value of serum TGF-β1 and CysC in type 2 diabetic kidney disease: a cross-sectional study

Background

Diabetic kidney disease (DKD) is one of the common microvascular complications of diabetes. The exploration of serum biomarkers holds promise for improving the efficiency and accuracy of early DKD diagnosis. This study aims to investigate the diagnostic value of transforming growth factor-β1 (TGF-β1) and cystatin C (CysC) in DKD patients.

Methods

A total of 126 patients with type 2 diabetes mellitus (T2DM) diagnosed at Dongzhimen Hospital, Beijing University of Chinese Medicine, between May 2021 and March 2023 were enrolled. Patients were categorized based on proteinuria levels and estimated glomerular filtration rate (eGFR). Correlation analyses were conducted to examine the relationships between serum TGF-β1, CysC, and clinical parameters. Logistic regression was applied to identify correlation factors for DKD and renal function impairment in T2DM patients. Furthermore, receiver operating characteristic (ROC) curve analysis was performed to assess diagnostic efficacy.

Results

Significant differences in TGF-β1 and CysC levels were observed across groups with varying proteinuria levels. CysC was positively correlated with TGF-β1 (r = 0.640, p < 0.001). TGF-β1 has been associated with proteinuria levels in T2DM patients. Each unit increase in TGF-β1 was associated with a 1.122-fold and 1.470-fold higher odds of the presence of microalbuminuria and proteinuria, respectively, in the normal proteinuria (NP) group. TGF-β1 and CysC showed varying diagnostic performance. TGF-β1 better distinguished microalbuminuria group (MP) from NP, while CysC alone was less effective. T2DM patients with impaired renal function exhibited significantly higher CysC and TGF-β1 levels compared to those with normal renal function. CysC emerged as an associated factor of renal function decline (OR = 2.255, p = 0.008). CysC demonstrated superior diagnostic efficacy compared to TGF-β1 in predicting renal function impairment (AUC = 0.974).

Conclusion

CysC and TGF-β1 can serve as potential biomarkers for assessing renal impairment and proteinuria in T2DM patients. Their combined evaluation demonstrates diagnostic value and clinical application potential.

MicroRNAs miR-148a-3p, miR-425-3p, and miR-20a-5p in Patients with IgA Nephropathy

BACKGROUND/OBJECTIVES

IgA nephropathy (IgAN) is one of the most common forms of glomerulonephritis leading to renal failure. MicroRNAs have been shown to play an important role in the pathogenesis and clinical course of IgA nephropathy; therefore, they offer the possibility of noninvasive diagnosis of this disease and have some value in predicting disease prognosis. This study aimed to evaluate the plasma levels of miR-148a-3p, miR-425-3p, and miR-20a-5p in patients with IgA nephropathy and their correlation with selected clinical parameters.

METHODS

This study included 44 patients with IgA nephropathy and 46 control subjects.

RESULTS

The results of our study indicated that in patients with IgA nephropathy, the increased plasma levels of miR-148a-3p and miR-425-3p correlated negatively with eGFR values. According to the Haas classification, plasma levels of miR-20a-5p were statistically significantly increased in patients with histopathological changes classified as Stages 3, 4, and 5 compared with patients with histopathological changes classified as Stages 1 and 2.

CONCLUSIONS

The results of our study suggest the possible involvement of miR-148a-3p, miR-425-3p, and miR-20a-5p in the pathogenesis of IgA nephropathy.

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.

The evolving understanding of systemic mechanisms in organ-specific IgA nephropathy: a focus on gut-kidney crosstalk

The interplay between multiple organs, known as inter-organ crosstalk, represents a complex and essential research domain in understanding the mechanisms and therapies for kidney diseases. The kidneys not only interact pathologically with many other organs but also communicate with other systems through various signaling pathways. It is of paramount importance to comprehend these mechanisms for the development of more efficient therapeutic strategies. Despite extensive research in IgA nephropathy (IgAN), the most common kidney disease, the elaboration mechanism of IgAN remains challenging. Numerous studies suggest that alterations in the intestinal microbiome and its metabolites are pivotal in the progression of IgAN, opening new avenues for understanding its mechanisms. Interestingly, certain presumed probiotics, such as Akkermansia muciniphila, have been implicated in the onset of IgAN, making the exploration of gut microbiota in the context of IgAN pathogenesis even more intriguing. In this review, we summarize the status of gut microbiology studies of IgAN and explore the possible mechanisms and intervention prospects. Future research and treatment directions may increasingly emphasize systemic, multi-organ combined interventions to decelerate the advancement of kidney disease and enhance the overall prognosis of patients.

Blood and urine biomarkers of disease progression in IgA nephropathy

The prognosis of patients with IgA nephropathy (IgAN) is variable but overall not good. Almost all patients with IgAN are at risk of developing end-stage renal disease within their expected lifetime. The models presently available for prediction of the risk of progression of IgAN, including the International IgA Nephropathy Prediction Tool, consist of traditional clinical, pathological, and therapeutic indicators. Finding biomarkers to improve the existing risk prediction models or replace pathological indicators is important for clinical practice. Many studies have attempted to identify biomarkers for prediction of progression of IgAN, such as galactose-deficient IgA1, complement, a spectrum of protein biomarkers, non-coding RNA, and shedding cells. This article reviews the biomarkers of progression of IgAN identified in recent years, with a focus on those with clinical value, in particular the combination of multiple biomarkers into a biomarker spectrum. Future research should focus on establishing a model based primarily on biomarkers that can predict progression of IgAN and testing it in various patient cohorts.

Fibrosis in Chronic Kidney Disease: Pathophysiology and Therapeutic Targets

Chronic kidney disease (CKD) is a slowly progressive condition characterized by decreased kidney function, tubular injury, oxidative stress, and inflammation. CKD is a leading global health burden that is asymptomatic in early stages but can ultimately cause kidney failure. Its etiology is complex and involves dysregulated signaling pathways that lead to fibrosis. Transforming growth factor (TGF)-β is a central mediator in promoting transdifferentiation of polarized renal tubular epithelial cells into mesenchymal cells, resulting in irreversible kidney injury. While current therapies are limited, the search for more effective diagnostic and treatment modalities is intensive. Although biopsy with histology is the most accurate method of diagnosis and staging, imaging techniques such as diffusion-weighted magnetic resonance imaging and shear wave elastography ultrasound are less invasive ways to stage fibrosis. Current therapies such as renin-angiotensin blockers, mineralocorticoid receptor antagonists, and sodium/glucose cotransporter 2 inhibitors aim to delay progression. Newer antifibrotic agents that suppress the downstream inflammatory mediators involved in the fibrotic process are in clinical trials, and potential therapeutic targets that interfere with TGF-β signaling are being explored. Small interfering RNAs and stem cell-based therapeutics are also being evaluated. Further research and clinical studies are necessary in order to avoid dialysis and kidney transplantation.

Potential of Plant-Derived Compounds in Preventing and Reversing Organ Fibrosis and the Underlying Mechanisms

Increased production of extracellular matrix is a necessary response to tissue damage and stress. In a normal healing process, the increase in extracellular matrix is transient. In some instances; however, the increase in extracellular matrix can persist as fibrosis, leading to deleterious alterations in organ structure, biomechanical properties, and function. Indeed, fibrosis is now appreciated to be an important cause of mortality and morbidity. Extensive research has illustrated that fibrosis can be slowed, arrested or even reversed; however, few drugs have been approved specifically for anti-fibrotic treatment. This is in part due to the complex pathways responsible for fibrogenesis and the undesirable side effects of drugs targeting these pathways. Natural products have been utilized for thousands of years as a major component of traditional medicine and currently account for almost one-third of drugs used clinically worldwide. A variety of plant-derived compounds have been demonstrated to have preventative or even reversal effects on fibrosis. This review will discuss the effects and the underlying mechanisms of some of the major plant-derived compounds that have been identified to impact fibrosis.

Urinary miR-185-5p is a biomarker of renal tubulointerstitial fibrosis in IgA nephropathy

Background

For IgA nephropathy (IgAN), tubular atrophy/interstitial fibrosis is the most important prognostic pathological indicator in the mesangial and endocapillary hypercellularity, segmental sclerosis, interstitial fibrosis/tubular atrophy, and presence of crescents (MEST-C) score. The identification of non-invasive biomarkers for tubular atrophy/interstitial fibrosis would aid clinical monitoring of IgAN progression and improve patient prognosis.

Methods

The study included 188 patients with primary IgAN in separate confirmation and validation cohorts. The associations of miR-92a-3p, miR-425-5p, and miR-185-5p with renal histopathological lesions and prognosis were explored using Spearman correlation analysis and Kaplan-Meier survival curves. Bioinformatics analysis and dual luciferase experiments were used to identify hub genes for miR-185-5p. The fibrotic phenotypes of tubular epithelial cells were evaluated in vivo and in HK-2 cells.

Results

miRNA sequencing and cohort validation revealed that the expression levels of miR-92a-3p, miR-425-5p, and miR-185-5p in urine were significantly increased among patients with IgAN; these levels could predict the extent of tubular atrophy/interstitial fibrosis in such patients. The combination of the three biomarkers resulted in an area under the receiver operating characteristic curve of 0.742. The renal prognosis was significantly worse in the miR-185-5p high expression group than in the low expression group (P=0.003). Renal tissue in situ hybridization, bioinformatics analysis, and dual luciferase experiments confirmed that miR-185-5p affects prognosis in patients with IgAN mainly by influencing expression of the target gene tight junction protein 1 (TJP1) in renal tubular epithelial cells. In vitro experiment revealed that an miR-185-5p mimic could reduce TJP1 expression in HK-2 cells, while increasing the levels of α-smooth muscle actin, fibronectin, collagen I, and collagen III; these changes promoted the transformation of renal tubular epithelial cells to a fibrotic phenotype. An miR-185-5p inhibitor can reverse the fibrotic phenotype in renal tubular epithelial cells. In a unilateral ureteral obstruction model, the inhibition of miR-185-5p expression alleviated tubular atrophy/interstitial fibrosis.

Conclusion

Urinary miR-185-5p, a non-invasive biomarker of tubular atrophy/interstitial fibrosis in IgAN, may promote the transformation of renal tubular epithelial cells to a fibrotic phenotype via TJP1.

Exploring the pathogenesis and treatment of IgA nephropathy based on epigenetics

IgA nephropathy is the most common primary glomerulonephritis worldwide. However, its exact cause remains unclear, with known genetic factors explaining only 11% of the variation. Recently, researchers have turned their attention to epigenetic abnormalities in immune-related diseases, recognizing their significance in IgA nephropathy's development and progression. This emerging field has revolutionized our understanding of epigenetics in IgA nephropathy research. Though in its early stages, studying IgA nephropathy's epigenetics holds promise for unraveling its pathogenesis and identifying new biomarkers and therapies. This review aims to comprehensively analyze epigenetics' role in IgA nephropathy's development and suggest avenues for potential therapeutic interventions. In the future, assessing and modulating epigenetics may become integral in diagnosing, tailoring treatments and assessing prognoses for IgA nephropathy.