Wnt Signaling in Kidney Development and Disease

Methylglyoxal-derived hydroimidazolone-1/RAGE axis induces renal oxidative stress and renal fibrosis in vitro and in vivo

Advanced glycation end products (AGEs) are important contributors to the progression of chronic kidney diseases (CKD), including renal fibrosis. Although the relationship between AGEs and renal fibrosis has been well studied, the mechanisms of individual AGE-induced renal injury remain poorly understood. This study investigated the adverse effect of methylglyoxal-derived hydroimidazolone-1 (MG-H1), a methylglyoxal (MG)-derived AGE generated by the glycation of MG and arginine residues, on kidney damage. We aimed to elucidate the molecular mechanisms of MG-H1-mediated renal injury and fibrosis, focusing on the receptor for AGEs (RAGE) signaling and its effects on the Wnt/β-catenin pathway, MAPK pathway, and inflammatory responses. Our results suggest that the MG-H1/RAGE axis plays a significant role in the pathogenesis of CKD and its downstream events involving MAPK kinase-related factors and inflammatory factors. MG-H1 treatment modulated the expression of inflammatory cytokines (TNF-α, IL-6, and IL-1β) and MAPK proteins (ERK1/2, JNK, and p38).

Developmental 6:2 FTCA exposure impairs renal development in chicken embryos via IGF signaling

6:2 fluorotelomer carboxylic acid (6:2 FTCA) is a perfluorooctanoic acid (PFOA) substitute, which is supposedly less accumulative and toxic than PFOA. However, 6:2 FTCA is structurally similar to PFOA, and there had already been reports about its toxicities comparable to PFOA. The aim of the current study is to assess potential effects of developmental exposure to 6:2 FTCA on the development of kidney in chicken embryo and to investigate underlying mechanism. Fertile chicken eggs were exposed to 1.25 mg/kg, 2.5 mg/kg or 5 mg/kg doses of 6:2 FTCA, or 2 mg/kg PFOA, then incubated to hatch. Serum and kidney of hatchling chickens were collected. Blood urea nitrogen (BUN) and creatinine (Cre) levels were measured with commercially available kits. Morphology of kidney was assessed with histopathology. To further reveal molecular mechanism of observed endpoints, IGF signaling molecules were assessed in the kidney samples with qRT-PCR, results indicated that IGFBP3 is a potentially crucial molecule. Lentiviruses overexpressing or silencing IGFBP3 were designed and applied to enhance/suppress the expression of IGFBP3 in developing chicken embryo for further verification of its role in the observed effects. Disrupted nephron formation, in the manifestation of decreased glomeruli number/area and increased serum BUN/Cre levels, was observed in the animals developmentally exposed to 6:2 FTCA. Correspondingly, IGF signaling molecules (IGF1, IGF1R and IGFBP3) were affected by 6:2 FTCA exposure. Meanwhile, overexpression of IGFBP3 effectively alleviated such changes, while silencing of IGFBP3 mimicked observed effects. In conclusion, developmental exposure to 6:2 FTCA is associated with disrupted chicken embryo renal development, in which IGFBP3 seems to be a remarkable contributor, suggesting potential health risks for human and other species. Further risk assessments and mechanistic works are necessary.

Nkd1 functions downstream of Axin2 to attenuate Wnt signaling

Wnt signaling is a crucial developmental pathway involved in early development as well as stem-cell maintenance in adults and its misregulation leads to numerous diseases. Thus, understanding the regulation of this pathway becomes vitally important. Axin2 and Nkd1 are widely utilized negative feedback regulators in Wnt signaling where Axin2 functions to destabilize cytoplasmic β-catenin, and Nkd1 functions to inhibit the nuclear localization of β-catenin. Here, we set out to further understand how Axin2 and Nkd1 regulate Wnt signaling by creating axin2gh1/gh1, nkd1gh2/gh2 single mutants and axin2gh1/gh1;nkd1gh2/gh2 double mutant zebrafish using sgRNA/Cas9. All three Wnt regulator mutants were viable and had impaired heart looping, neuromast migration defects, and behavior abnormalities in common, but there were no signs of synergy in the axin2gh1/gh1;nkd1gh2/gh2 double mutants. Further, Wnt target gene expression by qRT-PCR and RNA-seq, and protein expression by mass spectrometry demonstrated that the double axin2gh1/gh1;nkd1gh2/gh2 mutant resembled the nkd1gh2/gh2 phenotype demonstrating that Nkd1 functions downstream of Axin2. In support of this, the data further demonstrates that Axin2 uniquely alters the properties of β-catenin-dependent transcription having novel readouts of Wnt activity compared with nkd1gh2/gh2 or the axin2gh1/gh1;nkd1gh2/gh2 double mutant. We also investigated the sensitivity of the Wnt regulator mutants to exacerbated Wnt signaling, where the single mutants displayed characteristic heightened Wnt sensitivity, resulting in an eyeless phenotype. Surprisingly, this phenotype was rescued in the double mutant, where we speculate that cross-talk between Wnt/β-catenin and Wnt/Planar Cell Polarity pathways could lead to altered Wnt signaling in some scenarios. Collectively, the data emphasizes both the commonality and the complexity in the feedback regulation of Wnt signaling.

Exosomes on the development and progression of renal fibrosis

Renal fibrosis is a prevalent pathological alteration that occurs throughout the progression of primary and secondary renal disorders towards end-stage renal disease. As a complex and irreversible pathophysiological phenomenon, it includes a sequence of intricate regulatory processes at the molecular and cellular levels. Exosomes are a distinct category of extracellular vesicles that play a crucial role in facilitating intercellular communication. Multiple pathways are regulated by exosomes produced by various cell types, including tubular epithelial cells and mesenchymal stem cells, in the context of renal fibrosis. Furthermore, research has shown that exosomes present in bodily fluids, including urine and blood, may be indicators of renal fibrosis. However, the regulatory mechanism of exosomes in renal fibrosis has not been fully elucidated. This article reviewed and analysed the various mechanisms by which exosomes regulate renal fibrosis, which may provide new ideas for further study of the pathophysiological process of renal fibrosis and targeted treatment of renal fibrosis with exosomes.

A blood-based multi-omic landscape for the molecular characterization of kidney stone disease

Kidney stone disease (KSD, also named renal calculi, nephrolithiasis, or urolithiasis) is a common urological disease entailing the formation of minerals and salts that form inside the urinary tract, frequently caused by diabetes, high blood pressure, hypertension, and monogenetic components in most patients. 10% of adults worldwide are affected by KSD, which continues to be highly prevalent and with increasing incidence. For the identification of novel therapeutic targets in KSD, we adopted high-throughput sequencing and mass spectrometry (MS) techniques in this study and carried out an integrative analysis of exosome proteomic data and DNA methylation data from blood samples of normal and KSD individuals. Our research delineated the profiling of exosomal proteins and DNA methylation in both healthy individuals and those afflicted with KSD, finding that the overexpressed proteins and the demethylated genes in KSD samples are associated with immune responses. The consistency of the results in proteomics and epigenetics supports the feasibility of the comprehensive strategy. Our insights into the molecular landscape of KSD pave the way for a deeper understanding of its pathogenic mechanism, providing an opportunity for more precise diagnosis and targeted treatment strategies for KSD.

Insulin-like growth factor-1 effects on kidney development in preterm piglets

BACKGROUND

Preterm birth disrupts fetal kidney development, potentially leading to postnatal acute kidney injury. Preterm infants are deficient in insulin-like growth factor 1 (IGF-1), a growth factor that stimulates organ development. By utilizing a preterm pig model, this study investigated whether IGF-1 supplementation enhances preterm kidney maturation.

METHODS

Cesarean-delivered preterm pigs were treated systemically IGF-1 or vehicle control for 5, 9 or 19 days after birth. Blood, urine, and kidney tissue were collected for biochemical, histological and gene expression analyses. Age-matched term-born pigs were sacrificed at similar postnatal ages and served as the reference group.

RESULTS

Compared with term pigs, preterm pigs exhibited impaired kidney maturation, as indicated by analyses of renal morphology, histopathology, and inflammatory and injury markers. Supplementation with IGF-1 reduced signs of kidney immaturity, particularly in the first week of life, as indicated by improved morphology, upregulated expression of key developmental genes, reduced severity and incidence of microscopic lesions, and decreased levels of inflammatory and injury markers. No association was seen between the symptoms of necrotizing enterocolitis and kidney defects.

CONCLUSION

Preterm birth in pigs impairs kidney maturation and exogenous IGF-1 treatment partially reverses this impairment. Early IGF-1 supplementation could support the development of preterm kidneys.

IMPACT

Preterm birth may disrupt kidney development in newborns, potentially leading to morphological changes, injury, and inflammation. Preterm pigs have previously been used as models for preterm infants, but not for kidney development. IGF-1 supplementation promotes kidney maturation and alleviates renal impairments in the first week of life in preterm pigs. IGF-1 may hold potential as a supportive therapy for preterm infants sensitive to acute kidney injury.

Genome-wide association studies reconstructing chronic kidney disease

Chronic kidney disease (CKD) is a major health problem with an increasing epidemiological burden, and is the 16th leading cause of years of life lost worldwide. It is estimated that more than 10% of the population have a variable stage of CKD, while about 850 million people worldwide are affected. Nevertheless, public awareness remains low, clinical access is inappropriate in many circumstances and medication is still ineffective due to the lack of clear therapeutic targets. One of the main issues that drives these problems is the fact that CKD remains a clinical entity with significant causal ambiguity. Beyond diabetes mellitus and hypertension, which are the two major causes of kidney disease, there are still many gray areas in the diagnostic context of CKD. Genetics nowadays emerges as a promising field in nephrology. The role of genetic factors in CKD's causes and predisposition is well documented and thousands of genetic variants are well established to contribute to the high burden of disease. Next-generation sequencing is increasingly revealing old and new rare variants that cause Mendelian forms of chronic nephropathy while genome-wide association studies (GWAS) uncover common variants associated with CKD-defining traits in the general population. In this article we review how GWAS has revolutionized-and continues to revolutionize-the old concept of CKD. Furthermore, we present how the investigation of common genetic variants with previously unknown kidney significance has begun to expand our knowledge on disease understanding, providing valuable insights into disease mechanisms and perhaps paving the way for novel therapeutic targets.

Pharmacological modulation of Sonic Hedgehog signaling pathways in Angiogenesis: A mechanistic perspective

The Sonic hedgehog (SHh) signaling pathway is an imperative operating network that helps in regulates the critical events during the development processes like multicellular embryo growth and patterning. Disruptions in SHh pathway regulation can have severe consequences, including congenital disabilities, stem cell renewal, tissue regeneration, and cancer/tumor growth. Activation of the SHh signal occurs when SHh binds to the receptor complex of Patch (Ptc)-mediated Smoothened (Smo) (Ptc-smo), initiating downstream signaling. This review explores how pharmacological modulation of the SHh pathway affects angiogenesis through canonical and non-canonical pathways. The canonical pathway for angiogenesis involves the activation of angiogenic cytokines such as fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), placental growth factor (PGF), hepatocyte growth factor (HGF), platelet-derived growth factor (PDGF), stromal cell-derived factor 1α, transforming growth factor-β1 (TGF-β1), and angiopoietins (Ang-1 and Ang-2), which facilitate the process of angiogenesis. The Non-canonical pathway includes indirect activation of certain pathways like iNOS/Netrin-1/PKC, RhoA/Rock, ERK/MAPK, PI3K/Akt, Wnt/β-catenin, Notch signaling pathway, and so on. This review will provide a better grasp of the mechanistic approach of SHh in mediating angiogenesis, which can aid in the suppression of certain cancer and tumor growths.

Netrin 1 directs vascular patterning and maturity in the developing kidney

The intricate vascular system of the kidneys supports body fluid and organ homeostasis. However, little is known about how vascular architecture is established during kidney development. More specifically, how signals from the kidney influence vessel maturity and patterning remains poorly understood. Netrin 1 (Ntn1) is a secreted ligand that is crucial for vessel and neuronal guidance. Here, we demonstrate that Ntn1 is expressed by Foxd1+ stromal progenitors in the developing mouse kidney and conditional deletion (Foxd1GC/+;Ntn1fl/fl) results in hypoplastic kidneys with extended nephrogenesis. Wholemount 3D analyses additionally revealed the loss of a predictable vascular pattern in Foxd1GC/+;Ntn1fl/fl kidneys. As vascular patterning has been linked to vessel maturity, we investigated arterialization. Quantification of the CD31+ endothelium at E15.5 revealed no differences in metrics such as the number of branches or branch points, whereas the arterial vascular smooth muscle metrics were significantly reduced at both E15.5 and P0. In support of our observed phenotypes, whole kidney RNA-seq revealed disruptions to genes and programs associated with stromal cells, vasculature and differentiating nephrons. Together, our findings highlight the significance of Ntn1 to proper vascularization and kidney development.

Long-term viable chimeric nephrons generated from progenitor cells are a reliable model in cisplatin-induced toxicity

Kidney organoids have shown promise as evaluation tools, but their in vitro maturity remains limited. Transplantation into adult mice has aided in maturation; however, their lack of urinary tract connection limits long-term viability. Thus, long-term viable generated nephrons have not been demonstrated. In this study, we present an approachable method in which mouse and rat renal progenitor cells are injected into the developing kidneys of neonatal mice, resulting in the generation of chimeric nephrons integrated with the host urinary tracts. These chimeric nephrons exhibit similar maturation to the host nephrons, long-term viability with excretion and reabsorption functions, and cisplatin-induced renal injury in both acute and chronic phases, as confirmed by single-cell RNA-sequencing. Additionally, induced human nephron progenitor cells differentiate into nephrons within the neonatal kidneys. Collectively, neonatal injection represents a promising approach for in vivo nephron generation, with potential applications in kidney regeneration, drug screening, and pathological analysis.

Overexpression of long noncoding RNA 4933425B07Rik leads to renal hypoplasia by inactivating Wnt/β-catenin signaling pathway

Congenital anomalies of the kidney and urinary tract (CAKUT) is a general term for a class of diseases that are mostly caused by intrauterine genetic development limitation. Without timely intervention, certain children with CAKUT may experience progressive decompensation and a rapid decline in renal function, which will ultimately result in end-stage renal disease. At present, a comprehensive understanding of the pathogenic signaling events of CAKUT is lacking. The role of long noncoding RNAs (lncRNAs) in renal development and disease have recently received much interest. In previous research, we discovered that mice overexpressing the lncRNA 4933425B07Rik (Rik) showed a range of CAKUT phenotypes, primarily renal hypoplasia. The current study investigated the molecular basis of renal hypoplasia caused by Rik overexpression. We first used Rapid Amplification of cDNA ends (RACE) to obtain the full-length sequence of Rik in Rik +/+;Hoxb7 mice. Mouse proximal renal tubule epithelial cells (MPTCs) line with Rik overexpression was constructed using lentiviral methods, and mouse metanephric mesenchyme cell line (MK3) with Rik knockout was then constructed by the CRISPR‒Cas9 method. We performed RNA-seq on the Rik-overexpressing cell line to explore possible differentially expressed molecules and pathways. mRNA expression was confirmed by qRT‒PCR. Reduced levels of Wnt10b, Fzd8, and β-catenin were observed when Rik was expressed robustly. On the other hand, these genes were more highly expressed when Rik was knocked out. These results imply that overabundance of Rik might inhibit the Wnt/β-catenin signaling pathway, which may result in renal hypoplasia. In general, such research might help shed light on CAKUT causes and processes and offer guidance for creating new prophylactic and therapeutic strategies.

Elucidating environmental factors and their combined effects on CKDu in Sri Lanka using zebrafish

Chronic kidney disease with uncertain etiology (CKDu) in Sri Lanka has attracted much attention as a global health issue. However, how environmental factors in local drinking water induce kidney damage in organisms is still elusive. We investigated multiple environmental factors including water hardness and fluoride (HF), heavy metals (HM), microcystin-LR (MC-LR), and their combined exposure (HFMM) to elucidate their toxic effects on CKDu risk in zebrafish. Acute exposure affected renal development and inhibited the fluorescence of Na, K-ATPase alpha1A4:GFP zebrafish kidney. Chronic exposure influenced the body weight of both genders of adult fish and induced kidney damage by histopathological analyses. Furthermore, the exposure significantly disturbed differential expression genes (DEGs), diversity and richness of gut microbiota, and critical metabolites related to renal functions. The transcriptomic analysis revealed that kidney-related DEGs were linked with renal cell carcinoma, proximal tubule bicarbonate reclamation, calcium signaling pathway, and HIF-1 signaling pathway. The significantly disrupted intestinal microbiota was closely related to the environmental factors and H&E score, which demonstrated the mechanisms of kidney risks. Notably, the Spearman correlation analysis indicated that the changed bacteria such as Pseudomonas, Paracoccus, and ZOR0006, etc were significantly connected to the DEGs and metabolites. Therefore, the assessment of multiple environmental factors provided new insights on "bio-markers" as potential therapies of the target signaling pathways, metabolites, and gut bacteria to monitor or protect residents from CKDu.

Mechanisms of human umbilical cord mesenchymal stem cells-derived exosomal lncRNA GAS5 in alleviating EMT of HPMCs via Wnt/β-catenin signaling pathway

BACKGROUND

Prolonged peritoneal dialysis (PD) can result in epithelial-to-mesenchymal transition (EMT) and peritoneal fibrosis (PF), which can cause patients to discontinue PD. It is imperative to urgently investigate effective measures to mitigate PF. This study aims to reveal mechanisms of exosomal lncRNA GAS5 derived from human umbilical cord mesenchymal stem cells (hUC-MSCs) on EMT of human peritoneal mesothelial cells (HPMCs) under high glucose (HG) conditions.

METHODS

HPMCs were stimulated with 2.5% glucose. The effects on EMT of HPMCs were observed by using an hUC-MSC conditioned medium (hUC-MSC-CM) and extracted exosomes. After hUC-MSCs were transfected with GAS5 siRNA, exosomes were extracted to act on HPMCs for detecting EMT markers, PTEN, and Wnt/β-catenin pathway, lncRNA GAS5 and miR-21 expressions in HPMCs.

RESULTS

We found that HG could induce the EMT of HPMCs. Compared with the HG group, the hUC-MSC-CM could alleviate the EMT of HPMCs induced by HG through exosomes. Exosomes in the hUC-MSC-CM entered HPMCs, by transferring lncRNA GAS5 to HPMCs, which down-regulates miR-21 and up-regulates PTEN, thus finally alleviating EMT of HPMCs. The Wnt/β-catenin pathway plays an essential role in alleviating EMT of HPMCs by exosomes in the hUC-MSC-CM. By transferring lncRNA GAS5 to HPMCs, exosomes derived from hUC-MSCs may competitively bind to miR-21 to regulate suppression on target PTEN genes and alleviate EMT of HPMCs through the Wnt/β-catenin pathway.

CONCLUSIONS

Exosomes from the hUC-MSCs-CM could alleviate the EMT of HPMCs induced by HG via regulating lncRNA GAS5/miR-21/PTEN through the Wnt/β-catenin signaling pathway.

Differential Methylation of Telomere-Related Genes Is Associated with Kidney Disease in Individuals with Type 1 Diabetes

Diabetic kidney disease (DKD) represents a major global health problem. Accelerated ageing is a key feature of DKD and, therefore, characteristics of accelerated ageing may provide useful biomarkers or therapeutic targets. Harnessing multi-omics, features affecting telomere biology and any associated methylome dysregulation in DKD were explored. Genotype data for nuclear genome polymorphisms in telomere-related genes were extracted from genome-wide case-control association data (n = 823 DKD/903 controls; n = 247 end-stage kidney disease (ESKD)/1479 controls). Telomere length was established using quantitative polymerase chain reaction. Quantitative methylation values for 1091 CpG sites in telomere-related genes were extracted from epigenome-wide case-control association data (n = 150 DKD/100 controls). Telomere length was significantly shorter in older age groups (p = 7.6 × 10^-6). Telomere length was also significantly reduced (p = 6.6 × 10^-5) in DKD versus control individuals, with significance remaining after covariate adjustment (p = 0.028). DKD and ESKD were nominally associated with telomere-related genetic variation, with Mendelian randomisation highlighting no significant association between genetically predicted telomere length and kidney disease. A total of 496 CpG sites in 212 genes reached epigenome-wide significance (p ≤ 10^-8) for DKD association, and 412 CpG sites in 193 genes for ESKD. Functional prediction revealed differentially methylated genes were enriched for Wnt signalling involvement. Harnessing previously published RNA-sequencing datasets, potential targets where epigenetic dysregulation may result in altered gene expression were revealed, useful as potential diagnostic and therapeutic targets for intervention.

Dickkopf-1 Acts as a Profibrotic Mediator in Progressive Chronic Kidney Disease

Chronic kidney disease (CKD) is a serious public health problem. Due to a high variability in the speed of CKD progression to end-stage renal disease (ESRD) and the critical involvement of Wnt/β-catenin signaling in CKD, we investigated the role of the Wnt antagonist Dickkopf-1 (DKK1) in CKD progression. Our data revealed that patients with CKD stages 4-5 had higher DKK1 levels in their serum and renal tissues than the control subjects. In an 8-year follow-up, the serum DKK1-high group in the enrolled CKD patients showed a faster progression to ESRD than the serum DKK1-low group. Using a rat model of 5/6 nephrectomy (Nx)-induced CKD, we consistently detected elevated serum levels and renal production of DKK1 in 5/6 Nx rats compared to sham-operated rats. Importantly, the knockdown of the DKK1 levels in the 5/6 Nx rats markedly attenuated the CKD-associated phenotypes. Mechanistically, we demonstrated that the treatment of mouse mesangial cells with recombinant DKK1 protein induced not only the production of multiple fibrogenic proteins, but also the expression of endogenous DKK1. Collectively, our findings suggest that DKK1 acts as a profibrotic mediator in CKD, and elevated levels of serum DKK1 may be an independent predictor of faster disease progression to ESRD in patients with advanced CKD.

Pancreatic solid pseudopapillary neoplasm with concomitant left unilateral renal agenesis and bicornuate uterus: a case report

A solid pseudopapillary neoplasm (SPN) of the pancreas is a rare tumor of the pancreas. Concomitant SPN with urogenital anomalies is a very rare presentation.

Case Presentation

A 16-year-old female presented with a chief complaint of abdominal pain 30 days back. Solid pseudopapillary neoplasm (SPN) of the pancreas was diagnosed with the aid of ultrasonography and contrast-enhanced computed tomography of the abdomen and pelvis. Incidentally, concomitant left unilateral renal agenesis and bicornuate uterus were also detected in radiological findings. The patient underwent spleen-preserving distal pancreatectomy, and SPN was confirmed with the histopathological report.

Discussion

Symptomatic SPN patients present with an abdominal mass and pain or very rarely jaundice. Most of the SPNs are benign. Complete surgical excision results in more than 95% cure. SPN with concomitant urogenital anomalies is extremely rare, and their concurrent occurrence can be better attributed to Wnt signaling pathway owing to their similar pathogenic mechanism.

Conclusion

The solid pseudopapillary tumor has an excellent prognosis if timely resected. Proper evaluation of the patient with imaging is necessary to suspect and diagnose SPN who has urogenital anomalies and vice versa.

A Causal-Pathway Phenotype of Chronic Fatigue Syndrome due to Hemodialysis in Patients with End-Stage Renal Disease

BACKGROUND

End-stage renal disease (ESRD) is associated with fatigue and physiosomatic symptoms.

OBJECTIVE

The objective of this study is to delineate the associations between severity of fatigue and physio-somatic symptoms and glomerular filtration rate, inflammatory biomarkers, and Wnt/cateninpathway proteins.

METHODS

The Wnt-pathway related proteins β-catenin, Dickkopf-related protein 1 (DKK1), R-spondin- 1, and sclerostin were measured by ELISA technique in 60 ESRD patients and 30 controls. The Fibromyalgia and Chronic Fatigue Syndrome (FF) Rating Scale was used to assess the severity of FF symptoms.

RESULTS

ESRD is characterized by a significant increase in the total FF score, muscle tension, fatigue, sadness, sleep disorders, gastro-intestinal (GI) symptoms, and a flu-like malaise. The total-FF score was significantly correlated with serum levels of urea, creatinine, and copper (positively), and β-catenin, eGFR, hemoglobin, albumin, and zinc (inversely). The total-FF score was associated with the number of total dialysis and weekly dialysis sessions, and these dialysis characteristics were more important in predicting FF scores than eGFR measurements. Partial Least Squares analysis showed that the FF score comprised two factors that are differently associated with biomarkers: a) 43.0% of the variance in fatigue, GI symptoms, muscle tension, sadness, and insomnia is explained by hemoglobin, albumin, zinc, β-catenin, and R-spondin-1; and b) 22.3% of the variance in irritability, concentration and memory impairments by increased copper and cations/chloride ratio, and male sex.

CONCLUSION

ESRD patients show high levels of fatigue and physio-somatic symptoms associated with hemodialysis and mediated by dialysis-induced changes in inflammatory pathways, the Wnt/catenin pathway, and copper.

Disease modeling of ADAMTS9-related nephropathy using kidney organoids reveals its roles in tubular cells and podocytes

Introduction

Mutations in ADAMTS9 cause nephronophthisis-related ciliopathies (NPHP-RC), which are characterized by multiple developmental defects and kidney diseases. Patients with NPHP-RC usually have normal glomeruli and negligible or no proteinuria. Herein, we identified novel compound-heterozygous ADAMTS9 variants in two siblings with NPHP-RC who had glomerular manifestations, including proteinuria.

Methods

To investigate whether ADAMTS9 dysfunction causes NPHP and glomerulopathy, we differentiated ADAMTS9 knockout human induced pluripotent stem cells (hiPSCs) into kidney organoids. Single-cell RNA sequencing was utilized to elucidate the gene expression profiles from the ADAMTS9 knockout kidney organoids.

Results

ADAMTS9 knockout had no effect on nephron differentiation; however, it reduced the number of primary cilia, thereby recapitulating renal ciliopathy. Single-cell transcriptomics revealed that podocyte clusters express the highest levels of ADAMTS9, followed by the proximal tubules. Loss of ADAMTS9 increased the activity of multiple signaling pathways, including the Wnt/PCP signaling pathway, in podocyte clusters.

Conclusions

Mutations in ADMATS9 cause a glomerulotubular nephropathy in kidney and our study provides insights into the functional roles of ADMATS9 in glomeruli and tubules.

Heterozygous variants in the DVL2 interaction region of DACT1 cause CAKUT and features of Townes-Brocks syndrome 2

Most patients with congenital anomalies of the kidney and urinary tract (CAKUT) remain genetically unexplained. In search of novel genes associated with CAKUT in humans, we applied whole-exome sequencing in a patient with kidney, anorectal, spinal, and brain anomalies, and identified a rare heterozygous missense variant in the DACT1 (dishevelled binding antagonist of beta catenin 1) gene encoding a cytoplasmic WNT signaling mediator. Our patient's features overlapped Townes-Brocks syndrome 2 (TBS2) previously described in a family carrying a DACT1 nonsense variant as well as those of Dact1-deficient mice. Therefore, we assessed the role of DACT1 in CAKUT pathogenesis. Taken together, very rare (minor allele frequency ≤ 0.0005) non-silent DACT1 variants were detected in eight of 209 (3.8%) CAKUT families, significantly more frequently than in controls (1.7%). All seven different DACT1 missense variants, predominantly likely pathogenic and exclusively maternally inherited, were located in the interaction region with DVL2 (dishevelled segment polarity protein 2), and biochemical characterization revealed reduced binding of mutant DACT1 to DVL2. Patients carrying DACT1 variants presented with kidney agenesis, duplex or (multi)cystic (hypo)dysplastic kidneys with hydronephrosis and TBS2 features. During murine development, Dact1 was expressed in organs affected by anomalies in patients with DACT1 variants, including the kidney, anal canal, vertebrae, and brain. In a branching morphogenesis assay, tubule formation was impaired in CRISPR/Cas9-induced Dact1^-/- murine inner medullary collecting duct cells. In summary, we provide evidence that heterozygous hypomorphic DACT1 variants cause CAKUT and other features of TBS2, including anomalies of the skeleton, brain, distal digestive and genital tract.

Mechanisms of Peritoneal Mesothelial Cells in Peritoneal Adhesion

A peritoneal adhesion (PA) is a fibrotic tissue connecting the abdominal or visceral organs to the peritoneum. The formation of PAs can induce a variety of clinical diseases. However, there is currently no effective strategy for the prevention and treatment of PAs. Damage to peritoneal mesothelial cells (PMCs) is believed to cause PAs by promoting inflammation, fibrin deposition, and fibrosis formation. In the early stages of PA formation, PMCs undergo mesothelial–mesenchymal transition and have the ability to produce an extracellular matrix. The PMCs may transdifferentiate into myofibroblasts and accelerate the formation of PAs. Therefore, the aim of this review was to understand the mechanism of action of PMCs in PAs, and to offer a theoretical foundation for the treatment and prevention of PAs.

NEK2 Serves as a Novel Biomarker and Enhances the Tumorigenicity of Clear-CellRenal-Cell Carcinoma by Activating WNT/β-Catenin Pathway

Objective. Currently, cumulative evidence has shown that loss of NEK2 function suppresses tumor growth. However, complete studies on the regulatory role of NEK2 in clear-cellrenal-cell carcinoma (ccRCC) are rarely reported. Methods. The GEPIA database was used for information mining to analyze the gene expression differences between ccRCC tumor and normal tissues. At the same time, we analyzed the protein expression of NEK2 in clinical ccRCC samples and ccRCC cell lines. We detected the effect of NEK2 on the biological behavior of ccRCC at the cell level and further verified the biological effect of NEK2 on ccRCC cells in vivo by nude mouse tumorigenesis experiment. The expression of WNT/β-cateninpathway-related proteins and downstream proteins related to cell function were detected by Western blotting. Results. Using the GEPIA database, we observed that NEK2 expression level in ccRCC tissues was significantly higher than that in normal kidney tissues and was also related to tumor grade. The survival time of patients with ccRCC with high NEK2 expression was shorter than that of patients with low NEK2 expression. Compared with adjacent carcinoma and normal renal tubular epithelial cells, NEK2 levels were highly expressed in ccRCC tissues and ccRCC cell lines. NEK2 interference restrained ccRCC cell growth, migration, and invasion. NEK2 regulated the malignant behavior of ccRCC cells through the WNT/β-catenin pathway. Nude mouse tumorigenesis assay results showed that the transplanted tumors from NEK2 silenced mice grew more slowly and were smaller in size than those from control mice. Conclusions. NEK2 elevation may be associated with poor prognosis in ccRCC, and NEK2 enhances ccRCC cell proliferation, migration, and invasion ability by activating the WNT/β-catenin signaling pathway.

Integrated analysis of Wnt signalling system component gene expression

Wnt signalling controls patterning and differentiation across many tissues and organs of the developing embryo through temporally and spatially restricted expression of multi-gene families encoding ligands, receptors, pathway modulators and intracellular components. Here, we report an integrated analysis of key genes in the 3D space of the mouse embryo across multiple stages of development. We applied a method for 3D/3D image transformation to map all gene expression patterns to a single reference embryo for each stage, providing both visual analysis and volumetric mapping allowing computational methods to interrogate the combined expression patterns. We identify territories where multiple Wnt and Fzd genes are co-expressed and cross-compare all patterns, including all seven Wnt paralogous gene pairs. The comprehensive analysis revealed regions in the embryo where no Wnt or Fzd gene expression is detected, and where single Wnt genes are uniquely expressed. This work provides insight into a previously unappreciated level of organisation of expression patterns, as well as presenting a resource that can be utilised further by the research community for whole-system analysis.

Summary: A systematic analysis of integrated expression patterns of Wnt signalling pathway component-encoding genes and canonical pathway read-out, spatially mapped in 3D to mouse embryo models identifies co-expression territories.

The Prognostic Assessment of CDC20 in Patients with Renal Clear Cell Carcinoma and Its Relationship with Body Immunity

This article analyzes the relationship between cell division cycle (CDC20) molecules and oncology outcomes in patients with renal clear cell carcinoma (KIRC). CDC20 appears to act as a regulatory protein interacting with many other proteins at multiple points in the cycle. The RNA sequencing data and corresponding clinical information of CDC20 molecules were obtained from The Cancer Genome Atlas (TCGA) database. The expression of CDC20 in kidney renal clear cell carcinoma tissue and adjacent normal tissue was detected by immunohistochemical methods. Logistic analysis was performed to analyze the role of CDC20 in the clinicopathological characteristics and prognosis of KIRC. Gene Set Enrichment Analysis (GSEA) was used to identify the signal pathways which were related to CDC20. Independent prognostic factors were evaluated using univariate and multivariate Cox regression analysis. A nomogram involved in CDC20 expression and clinicopathological variables was conducted to predict overall survival (OS) in KIRC patients at 1, 3, and 5 years. Furthermore, the relation between CDC20 and immunity was also studied. Our results showed that CDC20 was upregulated in kidney renal clear cell carcinoma tissues, accompanying shorter OS (all P < 0.05). According to the results obtained by immunohistochemistry and TCGA database, CDC20 was significantly upregulated in kidney renal clear cell carcinoma tissues compared with neighboring normal kidney tissues. Univariate and multivariate Cox regression analysis showed that high expression of CDC20 was an independent prognostic factor of poor prognosis in kidney renal clear cell carcinoma patients (all P < 0.05). GSEA analysis suggested that the high expression of CDC20 was related to eight multiple signaling pathways. In addition, CDC20 was linked to tumour mutation burden (TMB), immune checkpoint molecules, tumour microenvironment, and immunological infiltration.

ShenKang Injection Attenuates Renal Fibrosis by Inhibiting EMT and Regulating the Wnt/β-Catenin Pathway

Shenkang Injection (SKI) is a traditional Chinese medicine injection commonly used in the clinical treatment of chronic kidney disease. Although it has been confirmed that SKI has anti-kidney fibrosis effects, the underlying mechanism remains unclear. To investigate the effects of SKI on epithelial-mesenchymal transition (EMT) and Wnt/β-catenin pathway and explore its potential anti-fibrosis mechanism. A unilateral ureteral obstruction (UUO) model was induced by ligating the left ureter of male SD rats. A total of 24 rats were randomly divided into the following four groups: sham group, model group, SKI group, and benazepril group. The rats in each group were treated for 28 days, and renal function was evaluated by blood urea nitrogen (BUN) and serum creatinine (Scr). The degree of renal fibrosis was assessed by hematoxylin and eosin (HE) and Masson staining. Extracellular matrix (ECM) deposition was evaluated by immunohistochemistry. Real-time fluorescent quantitative PCR (RT-qPCR) and western blotting were used to detect the expression of genes and proteins in the Wnt/β-catenin signaling pathway. Further studies were performed in vitro using HK-2 cells treated with TGF-β1. At 28 days postoperation, the levels of BUN and Scr expression were significantly increased in the UUO group. SKI and benazepril reduced the levels of BUN and Scr, which displayed protective renal effects. Pathological staining showed that compared with the sham operation group, the renal parenchymal structure was severely damaged, the number of glomeruli was reduced, and a large amount of collagen was deposited in the kidney tissue of the UUO group. SKI treatment reduced morphological changes. Immunohistochemistry showed that compared with the sham operation group, the content of collagen I and FN in the kidney tissue of the UUO group were significantly increased, whereas the SKI content was decreased. In addition, compared with the UUO group, the levels of Wnt1, active β-catenin, Snail1, and PAI-1 expression were reduced in the SKI group, suggesting that SKI may reduce renal fibrosis by mediating the Wnt/β-catenin pathway. Further in vitro studies showed that collagen I, FN, and α-SMA levels in HK-2 cells were significantly increased following stimulation with TGF-β1. SKI could significantly reduce the expression of collagen I, FN, and α-SMA. A scratch test showed that SKI could reduce HK-2 migration. In addition, by stimulating TGF-β1, the levels of Wnt1, active β-catenin, snail1, and PAI-1 were significantly upregulated. SKI treatment could inhibit the activity of the Wnt/β-catenin signaling pathway in HK-2 cells. SKI improves kidney function by inhibiting renal fibrosis. The anti-fibrotic effects may be mediated by regulation of the Wnt/β-catenin pathway and EMT inhibition.

Evaluation of the association of serum glypican-4 with prevalent and future kidney function

Serum glypican-4 (GPC4) has been identified as an insulin-sensitizing adipokine serving as a marker for body mass index and insulin resistance in humans. The association of circulating GPC4 with kidney function is to date largely unexplored. Therefore, we aimed to evaluate the association between serum GPC4 and prevalent as well future kidney function in a prospective cohort study. The study included 456 Caucasian coronary angiography patients. After a median follow up period of 3.4 years, data on kidney function was reassessed in all patients. Chronic kidney disease (CKD) was defined by decreased estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m² or albuminuria. At baseline, serum GPC4 was significantly associated with decreased eGFR (adjusted odds ratio (OR) per standard deviation = 4.75 [2.66–8.48]; P <  0.001), albuminuria (OR = 1.49 [1.15–1.92]; P = 0.002), and, accordingly, with CKD (OR = 1.75 [1.35–2.26]; P < 0.001). GPC4 levels also significantly and independently predicted the incidence of newly diagnosed decreased eGFR (OR = 2.74 [1.82–4.14]; P < 0.001, albuminuria (OR = 1.58 [1.01–2.46]; P = 0.043, and CKD (OR = 2.16 [1.45–3.23]; P < 0.001). ROC analysis indicated an additional predictive value of GPC4 to a basic prediction model for newly diagnosed CKD and eGFR < 60 mL/min/1.73 m². Our study, therefore, indicates that high serum GPC4 is associated with decreased prevalent and future kidney function.

Crucial Convolution: Genetic and Molecular Mechanisms of Coiling during Epididymis Formation and Development in Embryogenesis

As embryonic development proceeds, numerous organs need to coil, bend or fold in order to establish their final shape. Generally, this occurs so as to maximise the surface area for absorption or secretory functions (e.g., in the small and large intestines, kidney or epididymis); however, mechanisms of bending and shaping also occur in other structures, notably the midbrain–hindbrain boundary in some teleost fish models such as zebrafish. In this review, we will examine known genetic and molecular factors that operate to pattern complex, coiled structures, with a primary focus on the epididymis as an excellent model organ to examine coiling. We will also discuss genetic mechanisms involving coiling in the seminiferous tubules and intestine to establish the final form and function of these coiled structures in the mature organism.

Dickkopf 3-A New Indicator for the Deterioration of Allograft Function After Kidney Transplantation

Evidence of tubular atrophy and interstitial fibrosis is prognostically unfavorable and associated with a premature graft loss after kidney transplantation. Recently, Dickkopf 3 (DKK3), a profibrotic glycoprotein released by stressed tubular epithelial cells, has been identified to cause IF/TA by regulating the Wnt/β-catenin signaling and seems to engage a T-cell response. The aim of our study was to determine if a correlation between DKK3 and graft function exists and if DKK3 could be a new indicator to identify patients at risk for a deterioration in graft function. Patients, transplanted between 2016 and 2018, were analyzed with regard to DKK3 in the urine and graft function (creatinine, eGFR, albuminuria). Multivariable analyzes were used including known factors influencing graft function (PRA, donor age) to stress robustness of DKK3. The 3 and 12 month DKK3 values were significant predictors for subsequent graft function up to 36 months. An increase of DKK3 from month 3 to 12 of ≥ 25% showed a higher risk of an impaired graft function, with, e.g., a reduction in eGFR of about 9–10 ml/min in contrast to patients without intensified DKK3 increase. Induction therapy has an influence on DKK3 as patients induced with a T-cell depleting therapy showed a trend toward lower DKK3 values. In summary, our study is the first investigation of DKK3 in kidney transplant recipients and was able to show that DKK3 could forecast graft function. It is recommended to investigate the potential of DKK3 as a predictor of kidney function after transplantation in further studies.

CXC Chemokine Receptor 2 Accelerates Tubular Cell Senescence and Renal Fibrosis via β-Catenin-Induced Mitochondrial Dysfunction

Renal fibrosis is a common feature of various chronic kidney diseases (CKD). However, its underlying mechanism has not been totally clarified. C-X-C motif chemokine receptor (CXCR) family plays a role in renal fibrosis, however, detailed mechanisms have not been elucidated. Here, we report that CXCR2 has a potential role in tubular cell senescence and renal fibrosis, and is associated with β-catenin-activated mitochondrial dysfunction. CXCR2 is one of most increased members among CXCR family in unilateral ureteral obstruction (UUO) mice. CXCR2 was expressed primarily in tubules and co-localized with p16^INK4A, a cellular senescence marker, and β-catenin. Administration of SB225002, a selective CXCR2 antagonist, significantly inhibited the activation of β-catenin signaling, restored mitochondrial function, protected against tubular cell senescence and renal fibrosis in unilateral ureteral obstruction (UUO) mice. In unilateral ischemia-reperfusion injury (UIRI) mice, treatment with interlukin-8 (IL-8), the ligand of CXCR2, further aggravated β-catenin activation, mitochondrial dysfunction, tubular cell senescence and renal fibrosis, whereas knockdown of p16^INK4A inhibited IL-8-induced these effects. In vitro, SB225002 inhibited mitochondrial dysfunction and tubular cell senescence. Furthermore, ICG-001, a β-catenin signaling blocker, significantly retarded CXCR2-induced cellular senescence and fibrotic changes. These results suggest that CXCR2 promotes tubular cell senescence and renal fibrosis through inducing β-catenin-activated mitochondrial dysfunction.

Recent Advances in Epigenetics of Age-Related Kidney Diseases

Renal aging has attracted increasing attention in today’s aging society, as elderly people with advanced age are more susceptible to various kidney disorders such as acute kidney injury (AKI) and chronic kidney disease (CKD). There is no clear-cut universal mechanism for identifying age-related kidney diseases, and therefore, they pose a considerable medical and public health challenge. Epigenetics refers to the study of heritable modifications in the regulation of gene expression that do not require changes in the underlying genomic DNA sequence. A variety of epigenetic modifiers such as histone deacetylases (HDAC) inhibitors and DNA methyltransferase (DNMT) inhibitors have been proposed as potential biomarkers and therapeutic targets in numerous fields including cardiovascular diseases, immune system disease, nervous system diseases, and neoplasms. Accumulating evidence in recent years indicates that epigenetic modifications have been implicated in renal aging. However, no previous systematic review has been performed to systematically generalize the relationship between epigenetics and age-related kidney diseases. In this review, we aim to summarize the recent advances in epigenetic mechanisms of age-related kidney diseases as well as discuss the application of epigenetic modifiers as potential biomarkers and therapeutic targets in the field of age-related kidney diseases. In summary, the main types of epigenetic processes including DNA methylation, histone modifications, non-coding RNA (ncRNA) modulation have all been implicated in the progression of age-related kidney diseases, and therapeutic targeting of these processes will yield novel therapeutic strategies for the prevention and/or treatment of age-related kidney diseases.

Overlap of vitamin A and vitamin D target genes with CAKUT-related processes

Congenital Anomalies of the Kidney and Urinary Tract (CAKUT) are a group of abnormalities affecting the kidneys and their outflow tracts. CAKUT patients display a large clinical variability as well as a complex aetiology. Only 5% to 20% of the cases have a monogenic origin. It is thereby suspected that interactions of both genetic and environmental factors contribute to the disease. Vitamins are among the environmental factors that are considered for CAKUT aetiology. In this study, we aimed to investigate whether vitamin A or vitamin D could have a role in CAKUT aetiology. For this purpose we collected vitamin A and vitamin D target genes and computed their overlap with CAKUT-related gene sets. We observed limited overlap between vitamin D targets and CAKUT-related gene sets. We however observed that vitamin A target genes significantly overlap with multiple CAKUT-related gene sets, including CAKUT causal and differentially expressed genes, and genes involved in renal system development. Overall, these results indicate that an excess or deficiency of vitamin A might be relevant to a broad range of urogenital abnormalities.

Selenium Deficiency Leads to Changes in Renal Fibrosis Marker Proteins and Wnt/β-Catenin Signaling Pathway Components

Renal fibrosis is the final result of the progression of chronic kidney disease (CKD) to end-stage renal disease (ESRD). Earlier studies confirmed that selenium (Se) displays a close association with kidney diseases. However, the correlation between Se and fibrosis has rarely been explored. Thus, this article mainly aimed to investigate the effect of Se deficiency on renal fibrosis and the Wnt/β-catenin signaling pathway. Twenty BALB/c mice were fed a diet containing 0.02-mg/kg Se (Se-deficient diet) or 0.18-mg/kg Se (standard diet) for 20 weeks. A human glomerular mesangial cell (HMC) cell line was transfected with lentiviral TRNAU1AP-shRNA vector to establish a stable Se deficiency model in vitro. As indicated in this study, the glutathione (GSH) content in the Se-deficient group displayed an obvious decline compared with that in the control group, whereas the content of malondialdehyde (MDA) was obviously elevated. The results of Masson staining showed fibrosis around the renal tubules, and the results of immunohistochemistry showed that the area of positive fibronectin expression increased. In the Se-deficient group, the levels of collagen I, collagen III, matrix metalloproteinase 9 (MMP9), and other fibrosis-related proteins changed significantly in vivo and in vitro. Compared with the control group, the TRNAU1AP-shRNA group showed markedly reduced cell proliferation and migration abilities. Our data indicate that Se deficiency can cause kidney damage and renal fibrosis. Furthermore, the Wnt pathway is critical for the development of tissue and organ fibrosis. The data of this study demonstrated that the expression of Wnt5a, β-catenin, and dishevelled 1 (Dvl-1) was significantly upregulated in the Se-deficient group. Therefore, the Wnt/β-catenin pathway may play an important role in renal fibrosis caused by Se deficiency.

Extract of Corallodiscus flabellata attenuates renal fibrosis in SAMP8 mice via the Wnt/β-catenin/RAS signaling pathway

Background

Fibrosis is one of the most common pathological features of the aging process of the kidney, and fibrosis in aging kidneys also aggravates the process of chronic kidney disease (CKD). Corallodiscus flabellata B. L. Burtt (C. flabellata, CF) is a commonly used botanical drug in Chinese folklore. However, few studies have reported its pharmacological effects. This study aimed to explore the effect of CF ethanol extract on renal fibrosis in SAMP8 mice and identify potentially active compounds.

Methods

Senescence-accelerated mouse-prone 8 (SAMP8) were used as animal models, and different doses of CF were given by gavage for one month. To observe the degree of renal aging in mice using β-galactosidase staining. Masson staining and the expression levels of Col-I, α-SMA, and FN were used to evaluate the renal fibrosis in mice. The protein expression levels of Nrf2 pathway and Wnt/β-catenin/RAS pathway in the kidney were measured. And β-galactosidase (β-gal) induced NRK-52E cells as an in vitro model to screen the active components of CF.

Results

The CF ethanol extract significantly inhibited the activity of renal β-galactosidase and the expression levels of Col-I, α-SMA, and FN in SAMP8 mice, and improved Masson staining in SAMP8 mice. CF remarkably reduced urinary protein, creatinine, urea nitrogen and serum levels of TNF-α and IL-1β in SAMP8 mice, and significantly increased the levels of SOD and GSH-Px. Moreover, CF activated the Nrf2 pathway and blocked the Wnt/β-catenin/RAS pathway in the kidneys of mice. Besides, 3,4-dihydroxyphenylethanol (SDC-0-14, 16) and (3,4-dihydroxyphenylethanol-8-O-[4-O-trans-caffeoyl-β-D-apiofuranosyl-(1→3)-β-D-glucopyranosyl (1→6)]-β-D-glucopyranoside (SDC-1-8) were isolated from CF, which reduced the senescence of NRK-52E cells, and maybe the active ingredients of CF playing the anti-aging role.

Conclusions

Our experiments illuminated that CF ethanol extract may ameliorate renal fibrosis in SAMP8 mice via the Wnt/β-catenin/RAS pathway. And SDC-0-14,16 and SDC-1-8 may be the material basis for CF to exert anti-renal senescence-related effects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03535-y.

Blood DNA Methylation Predicts Diabetic Kidney Disease Progression in High Fat Diet-Fed Mice

Diabetic kidney disease (DKD) progresses at different rates among patients with type 2 diabetes mellitus (T2D). Early identification of patients with a higher risk of DKD progression is essential to improve prognosis. Epigenetic modifications, particularly DNA methylation, have been independently implicated in T2D and chronic kidney disease. The current study aimed to determine changes in blood DNA methylation that reflects and predicts DKD progression. C57BL/6 mice were fed a high-fat diet (HFD) from weaning and subclassified into two groups, HFD-1 and HFD-2, according to urinary kidney injury marker KIM-1/creatinine ratios (low vs. high) and histological abnormalities (mild–moderate vs. advanced). DNA methylation profiles were determined by reduced representative bisulfide sequencing (RRBS). Our results confirmed early and established DKD at week 9 and week 32, respectively. At week 32, advanced kidney injury was associated with dysregulation of methylation and demethylation enzymes in the kidney. Blood RRBS revealed 579 and 203 differentially methylated sites (DMS) between HFD-1 and HFD-2 animals at week 32 and week 9, respectively, among which 11 were common. The DMS in blood and kidney at week 32 were both related to organ development, neurogenesis, cell junction, and Wnt signalling, while the DMS in blood at week 9 suggested a specific enrichment of kidney development processes. In conclusion, our data strongly support the implication of early blood DNA methylation modifications and DKD progression in T2D that could be used to improve the disease’s prognostication.

MiR-138-5p targets RUNX2 to inhibit osteogenic differentiation of aortic valve interstitial cells via Wnt/β-catenin signaling pathway

Background

Human aortic valve interstitial cells (hAVICs) are a key factor in the pathogenesis of calcific aortic valve disease (CAVD). This research examines the role and mechanism of microRNA miR-138-5p in osteogenic differentiation of hAVICs.

Methods

RT-qPCR analysis was applied for detecting miR-138-5p and RUNX2 expression in valve tissues of CAVD patients and controls. On completion of induction of osteogenic differentiation of hAVICs, and after overexpression or interference of miR-138-5p expression, the condition of osteogenic differentiation and calcification of hAVICs was confirmed using alkaline phosphatase staining and alizarin red staining. Subsequently, western blot was utilized to detect the expression of osteogenesis-related proteins OPN and ALP, and Wnt/β-catenin signaling pathway-related proteins. Finally, the relationship between miR-138-5p and RUNX2 was validated by dual-luciferase reporter assay and Pearson’s correlation test.

Results

Down-regulation of miR-138-5p was found in CAVD patients and during osteogenic differentiation of hAVICs. Overexpression of miR-138-5p contribute to the inhibition of osteoblast differentiation and calcium deposition in hAVICs, and of ALP and OPN protein expression. RUNX2 was a target gene of miR-138-5p, and it was negatively correlated with miR-138-5p in CAVD. Additionally, overexpression of RUNX2 could reverse the inhibitory effect of miR-138-5p on osteogenic differentiation of hAVICs.

Conclusion

miR-138-5p can act as a positive regulator of osteogenic differentiation in CAVD patients to involve in inhibiting valve calcification, which is achieved through RUNX2 and Wnt/β-catenin signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02471-6.

Alamandine alleviates hypertension and renal damage via oxidative-stress attenuation in Dahl rats

Alamandine (Ala) is a novel member of the renin-angiotensin-system (RAS) family. The present study aimed to explore the effects of Ala on hypertension and renal damage of Dahl salt-sensitive (SS) rats high-salt diet-induced, and the mechanisms of Ala on renal-damage alleviation. Dahl rats were fed with high-salt diets to induce hypertension and renal damage in vivo, and HK-2 cells were treated with sodium chloride (NaCl) to induce renal injury in vitro. Ala administration alleviated the high-salt diet-induced hypertension, renal dysfunction, and renal fibrosis and apoptosis in Dahl SS rats. The HK-2 cells' damage, and the increases in the levels of cleaved (c)-caspase3, c-caspase8, and c-poly(ADP-ribose) polymerase (PARP) induced by NaCl were inhibited by Ala. Ala attenuated the NaCl-induced oxidative stress in the kidney and HK-2 cells. DETC, an inhibitor of SOD, reversed the inhibitory effect of Ala on the apoptosis of HK-2 cells induced by NaCl. The NaCl-induced increase in the PKC level was suppressed by Ala in HK-2 cells. Notably, PKC overexpression reversed the moderating effects of Ala on the NaCl-induced apoptosis of HK-2 cells. These results show that Ala alleviates high-salt diet-induced hypertension and renal dysfunction. Ala attenuates the renal damage via inhibiting the PKC/reactive oxygen species (ROS) signaling pathway, thereby suppressing the apoptosis in renal tubular cells.

Geraniol protects against cyclosporine A-induced renal injury in rats: Role of Wnt/β-catenin and PPARγ signaling pathways

AIMS

The nephrotoxicity of cyclosporine A (CsA) limits its use as an immunosuppressant. Wnt/β-catenin signaling is involved in the pathogenesis of both acute and chronic kidney disease, and it is inhibited by peroxisome proliferator-activated receptor gamma (PPARγ). We aimed to evaluate if geraniol, which can modulate both PPARγ and Wnt signaling, could protect against CsA-induced nephrotoxicity.

MATERIALS AND METHODS

Rats (6 groups) received the vehicle or a combination of CsA (30 mg/kg) with the vehicle, geraniol (50, 100, or 200 mg/kg), or the PPARγ agonist pioglitazone for 4 weeks. Blood pressure (BP), markers of renal injury (serum urea, serum creatinine, blood urea nitrogen, and urinary NAG), oxidative stress (glutathione peroxidase), inflammation (ICAM-1, IL-18, and NF-κB), apoptosis (caspase-3), extracellular matrix remodeling [matrix metalloproteinase-9 (MMP-9)], and fibrosis (TGF-β1, Smad3, and Smad7) were assessed. Renal histological analysis, Wnt signaling components (Wnt-4/β-catenin and E-cadherin), and PPARγ expression were evaluated.

KEY FINDINGS

CsA group had renal injury, as well as increased BP, renal oxidative stress, inflammation, and fibrosis. The latter changes were associated with altered renal architecture, active Wnt signaling (higher Wnt-4 and β-catenin expression and E-cadherin down-regulation), and lower PPARγ levels. Geraniol protected against kidney damage and the associated biochemical and histomorphological changes in a dose-dependent manner. The latter effects were comparable or superior to those of pioglitazone.

SIGNIFICANCE

The down-regulation of Wnt/β-catenin and the increase in PPARγ by geraniol suggest that both pathways are involved in its renoprotective potential. The study highlights geraniol as a valuable protective asset against chemically induced nephrotoxicity.

Immunohistochemical Expression of Wnt-4 Protein in Clear Cell Renal Carcinoma

Wingless binding integration site proteins (Wnt) have an important role in normal kidney development and in various kidney diseases. They are required for complete epithelial differentiation and normal nephron formation. Changes in these proteins could also have important role in carcinogenesis. This study included 185 patients with clear cell renal carcinoma (ccRCC) in whom immunohistochemical expression of Wnt-4 protein in healthy and tumorous tissue after surgery was investigated. There was higher expression of Wnt-4 in healthy than in tumor tissue. No difference between Fuhrman’s grade and Wnt-4 expression was found. A poor negative correlation between tumor size and Wnt-4 expression was found. Patients with suspected metastatic diseases had higher Wnt-4 expression. There was no difference in survival rates between Wnt-4 negative and positive groups. In our study we have shown that high Wnt-4 expression in healthy tissue decreases in low-grade tumors but then increases in high-grade tumors, suggesting that tumor progression requires Wnt-4 activation or reactivation.

Recent Advances in Kidney Bioengineering

Kidney disease is an epidemic that affects more than 600 million people worldwide. The socioeconomic impacts of the disease disproportionately affect Hispanic and non-Hispanic Black Americans, making the disease an issue of social inequality. The urgency of this situation has only become worse during the COVID-19 pandemic, as those who are hospitalized for COVID-19 have an increased risk of kidney failure. For researchers, the kidney is a complex organ that is difficult to accurately model and understand. Traditional cell culture models are not adequate for studying the functional intricacies of the kidney, but recent experiments have offered improvements for understanding these systems. Recent progress includes organoid modeling, 3D bioprinting, decellularization, and microfluidics. Here, we offer a review of the most recent advances in kidney bioengineering.

Nephronophthisis-Pathobiology and Molecular Pathogenesis of a Rare Kidney Genetic Disease

The exponential rise in our understanding of the aetiology and pathophysiology of genetic cystic kidney diseases can be attributed to the identification of cystogenic genes over the last three decades. The foundation of this was laid by positional cloning strategies which gradually shifted towards next-generation sequencing (NGS) based screenings. This shift has enabled the discovery of novel cystogenic genes at an accelerated pace unlike ever before and, most notably, the past decade has seen the largest increase in identification of the genes which cause nephronophthisis (NPHP). NPHP is a monogenic autosomal recessive cystic kidney disease caused by mutations in a diverse clade of over 26 identified genes and is the most common genetic cause of renal failure in children. NPHP gene types present with some common pathophysiological features alongside a diverse range of extra-renal phenotypes associated with specific syndromic presentations. This review provides a timely update on our knowledge of this disease, including epidemiology, pathophysiology, anatomical and molecular features. We delve into the diversity of the NPHP causing genes and discuss known molecular mechanisms and biochemical pathways that may have possible points of intersection with polycystic kidney disease (the most studied renal cystic pathology). We delineate the pathologies arising from extra-renal complications and co-morbidities and their impact on quality of life. Finally, we discuss the current diagnostic and therapeutic modalities available for disease management, outlining possible avenues of research to improve the prognosis for NPHP patients.

Inactivation of the Wnt/β-catenin signaling contributes to the epithelial barrier dysfunction induced by sodium oxalate in canine renal epithelial cells

High oxalate consumption has been recognized as a risk factor for renal calcium oxalate stones in companion animals (dogs and cats). However, the cellular signaling involved in oxalate-induced dysfunction in renal tubular epithelial cells remains not fully elucidated. In this study, Mardin-Darby canine kidney (MDCK) cells, an epithelial cell line derived from canine kidney tubule, were tested for cell proliferation activity and barrier function after being exposed to sodium oxalate (NaOx). Further, the involvement of Wnt/β-catenin in NaOx-induced renal epithelial barrier dysfunction was evaluated. MDCK cells treated with NaOx exhibited reduction in cell proliferation and migration. Besides, NaOx exposure led to a decrease in transepithelial electrical resistance and an increase in paracellular permeability. The deleterious effects of NaOx on epithelial barrier function were related to the suppressed abundance of tight junction proteins including zonula occludens, occludin, and claudin-1. Of note, protein levels of β-catenin and phosphorylated (p)-β-catenin (Ser552) in MDCK cells were repressed by NaOx, indicating inhibitory effects on Wnt/β-catenin signaling. An inhibition of glycogen synthase kinase-3β (GSK-3β) by SB216763 enhanced the abundance of β-catenin and p-β-catenin (Ser552), and protected against epithelial barrier dysfunction in NaOx-treated MDCK cells. The results revealed a critical role of Wnt/β-catenin signaling in the epithelial barrier function of MDCK cells. Activation of Wnt/β-catenin signaling might be a potential therapeutic target for the treatment of oxalate-linked renal stones.

Bardet-Biedl syndrome proteins modulate the release of bioactive extracellular vesicles

Primary cilia are microtubule based sensory organelles important for receiving and processing cellular signals. Recent studies have shown that cilia also release extracellular vesicles (EVs). Because EVs have been shown to exert various physiological functions, these findings have the potential to alter our understanding of how primary cilia regulate specific signalling pathways. So far the focus has been on lgEVs budding directly from the ciliary membrane. An association between cilia and MVB-derived smEVs has not yet been described. We show that ciliary mutant mammalian cells demonstrate increased secretion of small EVs (smEVs) and a change in EV composition. Characterisation of smEV cargo identified signalling molecules that are differentially loaded upon ciliary dysfunction. Furthermore, we show that these smEVs are biologically active and modulate the WNT response in recipient cells. These results provide us with insights into smEV-dependent ciliary signalling mechanisms which might underly ciliopathy disease pathogenesis.

Extracellular vesicles (EV) are known to be released from the primary cilium, but the role ciliary proteins play in EV biogenesis remains unexplored. Here, the authors demonstrate increased secretion of small EVs with altered cargo composition from cells with known ciliarelated mutations. Wnt related molecules made up a majority of altered cargo

Wnt/β-catenin pathway proteins in end-stage renal disease

Aim: To delineate the association of end-stage renal disease (ESRD) and Wnt-proteins including the agonist R-spondin-1, the transducer β-catenin and the antagonists DKK1 and sclerostin. Materials & methods: Serum Wnt-pathway proteins levels were measured by ELISA in 60 ESRD patients and 30 normal controls. Results: DKK1 and sclerostin were significantly higher in ESRD than in controls, and β-catenin and the catenin + R-spondin-1/DKK1 + sclerostin ratio, reflecting the ratio of agonist and transducer on antagonists (AT/ANTA), were significantly lower in ESRD. Estimated glomerular filtration rate was significantly associated with DKK1 and sclerostin (inversely), β-catenin (positively) and the AT/ANTA ratio (r = 0.468, p < 0.001). Conclusion: Wnt/β-catenin pathway proteins show significant alterations in ESRD, indicating significantly increased levels of antagonists.

LncRNA GAS5 Competitively Combined With miR-21 Regulates PTEN and Influences EMT of Peritoneal Mesothelial Cells via Wnt/β-Catenin Signaling Pathway

Objective

Epithelial-mesenchymal transition (EMT) is an important factor leading to peritoneal fibrosis (PF) in end-stage renal disease (ESRD) patients. The current research aimed to evaluate the effect of long non-coding RNA growth arrest-specific 5 (lncRNA GAS5) in human peritoneal mesothelial cells (HPMCs) EMT and explore the potential molecular mechanisms.

Materials and Methods

HPMCs were cultured under control conditions or with high glucose (HG). The cells were then treated with lncRNA GAS5, lncRNA GAS5 siRNA, with or without miR-21 inhibitor and PTEN transfection. Expression of lncRNA GAS5, miR-21, α-SMA, Vimentin, E-cadherin, phosphatase and tensin homolog deleted on chromosome ten (PTEN), Wnt3a, and β-catenin were measured by real time PCR and Western blotting. Bioinformatics analyses were used to test the specific binding sites between the 3' UTR of the PTEN gene, miR-21, and lncRNA GAS5. Rescue experiments were performed to confirm the lncRNA GAS5/miR-21/PTEN axis in HPMC EMT.

Results

We found that HG-induced EMT decreased lncRNA GAS5 and that overexpression of lncRNA GAS5 can attenuate EMT in HPMCs. In addition, lncRNA GAS5 regulated HG-induced EMT through miR-21/PTEN. Cotransfection of miR-21 inhibitors remarkably increased PTEN expression and attenuated EMT in lncRNA GAS5 knockdown HPMCs. Moreover, rescue experiments showed that overexpression of PTEN attenuated the EMT effects of lncRNA GAS5 siRNA in HPMCs. We also confirmed that the Wnt/β-catenin pathway was stimulated in lncRNA GAS5/miR-21/PTEN-mediated EMT.

Conclusion

Our research showed that lncRNA GAS5 competitively combined with miR-21 to regulate PTEN expression and influence EMT of HPMCs via the Wnt/β-catenin signaling pathway. This study provides novel evidence that lncRNA GAS5 may be a potential therapeutic target for HPMC EMT.

The changes in the expression levels of β-catenin gene in pre- and post- Kidney Transplants

PURPOSE

Wnt signaling is an important pathway in kidney development and disease. We aimed to establish the levels of β-catenin expression in CD4⁺ T cells before and after renal transplantation and to associate it with the form of transplant type, rejection, and graft dysfunction.

METHODS

CD4⁺ T cells were isolated from patients before and after kidney transplantation and their purity was confirmed by flow cytometer. RNA isolation and cDNA synthesis were carried out from these cells. The expression changes of the β-catenin were investigated by real-time polymerase chain reaction (RT-PCR). Changes in the β-catenin protein levels were determined by the western blot analysis.

RESULTS

The increasing expression levels of β-catenin were detected in 60.8% of the patients 6 months after transplantation when compared to patients before transplantation result. 12 of these 14 patients had no graft rejection. It was observed that 11 of 14 patients with increased β-catenin expression had not graft dysfunction after the transplantation.

CONCLUSION

According to our results, the increased levels of β-catenin expression after transplantation may have a protective function for kidney survival. To understand this protective mechanism, further analysis of this signaling pathway is necessary.

Current Epigenetic Insights in Kidney Development

The kidney is among the best characterized developing tissues, with the genes and signaling pathways that regulate embryonic and adult kidney patterning and development having been extensively identified. It is now widely understood that DNA methylation and histone modification patterns are imprinted during embryonic development and must be maintained in adult cells for appropriate gene transcription and phenotypic stability. A compelling question then is how these epigenetic mechanisms play a role in kidney development. In this review, we describe the major genes and pathways that have been linked to epigenetic mechanisms in kidney development. We also discuss recent applications of single-cell RNA sequencing (scRNA-seq) techniques in the study of kidney development. Additionally, we summarize the techniques of single-cell epigenomics, which can potentially be used to characterize epigenomes at single-cell resolution in embryonic and adult kidneys. The combination of scRNA-seq and single-cell epigenomics will help facilitate the further understanding of early cell lineage specification at the level of epigenetic modifications in embryonic and adult kidney development, which may also be used to investigate epigenetic mechanisms in kidney diseases.

Recent updates on Wnt signaling modulators: a patent review (2014-2020)

Introduction: Wnt signaling is a signal transduction pathway that plays a vital role in embryonic development and normal tissue preservation. Dysfunction of it gives rise to various diseases like cancer, Alzheimer's, metabolic and skeletal disorders, kidney and liver disease, etc. Thus, targeting Wnt pathway can be a potential approach to design and develop novel therapeutic classes.Areas covered: Authors provided an overview of Wnt modulators from 2014 to 2020. Different heterocyclic scaffolds and their pharmacology from a total of 104 PCT applications have been summarized.Expert opinion: The scientific community is working extensively to bring first in the class molecule to the market which targets Wnt pathway. Lorecivivint, Wnt inhibitor, for the treatment of knee Osteoarthritis and SM-04554, Wnt activator, for the treatment of androgenetic alopecia are currently under Phase III. Other molecules, LGK-974, RXC-004, ETC-159, CGX-1321, PRI-724, CWP-232291 and BC-2059 are also under different stages of clinical development for the treatment of cancer. Antibody based Wnt modulator, OTSA101-DTPA-90Y is currently under Phase I for the treatment of Relapsed or Refractory Synovial Sarcoma while OMP-18R5 is under Phase I for Metastatic Breast Cancer.  Ongoing preclinical/clinical trials will define the role of the Wnt pathway in different therapeutic areas and open new opportunities.

OFD Type I syndrome: lessons learned from a rare ciliopathy

The OFD1 gene was initially identified as the gene responsible for the X-linked dominant male lethal OFD type I syndrome, a developmental disorder ascribed to cilia disfunction. The transcript has been subsequently associated to four different X-linked recessive conditions, namely Joubert syndrome, retinitis pigmentosa, primary ciliary dyskinesia and Simpson-Golabi-Behmel type 2 syndrome. The centrosomal/basal body OFD1 protein has indeed been shown to be required for primary cilia formation and left-right asymmetry. The protein is also involved in other tasks, e.g. regulation of cellular protein content, constrain of the centriolar length, chromatin remodeling at DNA double strand breaks, control of protein quality balance and cell cycle progression, which might be mediated by non-ciliary activities. OFD1 represents a paradigmatic model of a protein that performs its diverse actions according to the cell needs and depending on the subcellular localization, the cell type/tissue and other possible factors still to be determined. An increased number of multitask protein, such as OFD1, may represent a partial explanation to human complexity, as compared with less complex organisms with an equal or slightly lower number of proteins.

The Role of Macrophages in Kidney Fibrosis

The phenotypic heterogeneity and functional diversity of macrophages confer on them complexed roles in the development and progression of kidney diseases. After kidney injury, bone marrow-derived monocytes are rapidly recruited to the glomerulus and tubulointerstitium. They are activated and differentiated on site into pro-inflammatory M1 macrophages, which initiate Th1-type adaptive immune responses and damage normal tissues. In contrast, anti-inflammatory M2 macrophages induce Th2-type immune responses, secrete large amounts of TGF-β and anti-inflammatory cytokines, transform into αSMA+ myofibroblasts in injured kidney, inhibit immune responses, and promote wound healing and tissue fibrosis. Previous studies on the role of macrophages in kidney fibrosis were mainly focused on inflammation-associated injury and injury repair. Apart from macrophage-secreted profibrotic cytokines, such as TGF-β, evidence for a direct contribution of macrophages to kidney fibrosis is lacking. However, under inflammatory conditions, Wnt ligands are derived mainly from macrophages and Wnt signaling is central in the network of multiple profibrotic pathways. Largely underinvestigated are the direct contribution of macrophages to profibrotic signaling pathways, macrophage phenotypic heterogeneity and functional diversity in relation to kidney fibrosis, and on their cross-talk with other cells in profibrotic signaling networks that cause fibrosis. Here we aim to provide an overview on the roles of macrophage phenotypic and functional diversity in their contribution to pro-fibrotic signaling pathways, and on the therapeutic potential of targeting macrophages for the treatment of kidney fibrosis.

Nupr1 mediates renal fibrosis via activating fibroblast and promoting epithelial-mesenchymal transition

Renal interstitial fibrosis (RIF) is a pathological process that fibrotic components are excessively deposited in the renal interstitial space due to kidney injury, resulting in impaired renal function and chronic kidney disease. The molecular mechanisms controlling renal fibrosis are not fully understood. In this present study, we identified Nuclear protein 1 (Nupr1), a transcription factor also called p8, as a novel regulator promoting renal fibrosis. Unilateral ureteral obstruction (UUO) time-dependently induced Nupr1 mRNA and protein expression in mouse kidneys while causing renal damage and fibrosis. Nupr1 deficiency (Nupr1^-/- ) attenuated the renal tubule dilatation, tubular epithelial cell atrophy, and interstitial collagen accumulation caused by UUO. Consistently, Nupr1^-/- significantly decreased the expression of type I collagen, myofibroblast markers smooth muscle α-actin (α-SMA), fibroblast-specific protein 1 (FSP-1), and vimentin in mouse kidney that were upregulated by UUO. These results suggest that Nupr1 protein was essential for fibroblast activation and/or epithelial-mesenchymal transition (EMT) during renal fibrogenesis. Indeed, Nupr1 was indispensable for TGF-β-induced myofibroblast activation of kidney interstitial NRK-49F fibroblasts, multipotent mesenchymal C3H10T1/2 cells, and the EMT of kidney epithelial NRK-52E cells. It appears that Nupr1 mediated TGF-β-induced α-SMA expression and collagen synthesis by initiating Smad3 signaling pathway. Importantly, trifluoperazine (TFP), a Nupr1 inhibitor, alleviated UUO-induced renal fibrosis. Taken together, our results demonstrate that Nupr1 promotes renal fibrosis by activating myofibroblast transformation from both fibroblasts and tubular epithelial cells.

Wnt-C59 inhibits proinflammatory cytokine expression by reducing the interaction between β-catenin and NF-κB in LPS-stimulated epithelial and macrophage cells

Dysregulation of the Wnt pathway causes various diseases including cancer, Parkinson’s disease, Alzheimer’s disease, schizophrenia, osteoporosis, obesity and chronic kidney diseases. The modulation of dysregulated Wnt pathway is absolutely necessary. In the present study, we evaluated the anti-inflammatory effect and the mechanism of action of Wnt-C59, a Wnt signaling inhibitor, in lipopolysaccharide (LPS)-stimulated epithelial cells and macrophage cells. Wnt-C59 showed a dose-dependent anti-inflammatory effect by suppressing the expression of proinflammatory cytokines including IL6, CCL2, IL1A, IL1B, and TNF in LPS-stimulated cells. The dysregulation of the Wnt/β-catenin pathway in LPS stimulated cells was suppressed by Wnt-C59 treatment. The level of β-catenin, the executor protein of Wnt/β-catenin pathway, was elevated by LPS and suppressed by Wnt-C59. Overexpression of β-catenin rescued the suppressive effect of Wnt-C59 on proinflammatory cytokine expression and nuclear factor-kappa B (NF-κB) activity. We found that the interaction between β-catenin and NF-κB, measured by co-immunoprecipitation assay, was elevated by LPS and suppressed by Wnt-C59 treatment. Both NF-κB activity for its target DNA binding and the reporter activity of NF-κB-responsive promoter showed identical patterns with the interaction between β-catenin and NF-κB. Altogether, our findings suggest that the anti-inflammatory effect of Wnt-C59 is mediated by the reduction of the cellular level of β-catenin and the interaction between β-catenin and NF-κB, which results in the suppressions of the NF-κB activity and proinflammatory cytokine expression.