The role of osteopontin in kidney diseases

Role of osteokines in atherosclerosis

Despite their diverse physiologies and roles, the heart, skeletal muscles, and smooth muscles all derive from a common embryonic source as bones. Moreover, bone tissue, skeletal and smooth muscles, and the heart share conserved signaling pathways. The maintenance of skeletal health is precisely regulated by osteocytes, osteoblasts, and osteoclasts through coordinated secretion of bone-derived factors known as osteokines. Increasing evidence suggests the involvement of osteokines in regulating atherosclerotic vascular disease. Therefore, this review aims to examine the evidence for the role of osteokines in atherosclerosis development and progression comprehensively. Specifically discussed are extensively studied osteokines in atherosclerosis such as osteocalcin, osteopontin, osteoprotegerin, and fibroblast growth factor 23. Additionally, we highlighted the effects of exercise on modulating these key regulators derived from bone tissue metabolism. We believe that gaining an enhanced understanding of how osteocalcin contributes to the process of atherosclerosis will enable us to develop targeted and comprehensive therapeutic strategies against diseases associated with its progression.

Association of calcific rotator cuff tendinopathy with nephrolithiasis and/or cholelithiasis: A case-control study

This study aimed to examine the association between calcific rotator cuff tendinopathy (RCT) and nephrolithiasis and/or cholelithiasis. A case-control study was conducted on patients diagnosed with RCT between June 2016 and June 2022. RCT was confirmed by ultrasound, and patients were divided into 2 groups: calcific RCT (case) and non-calcific RCT (control). Data were collected retrospectively from electronic medical records and completed by phone calls, looking for a history of nephrolithiasis and/or cholelithiasis; based on clinical features or incidental findings on abdominal and pelvic imaging. A total of 210 patients with RCT were included. Among the 95 cases of calcific RCT, 43 had a history of lithiasis (45.3%) against 23 (20%) from the non-calcific RCT group (P < .001); 21 patients suffered from nephrolithiasis (22.1%) and 26 had cholelithiasis (27.4%) versus 10 (8.7%) (P = .006) and 16 (13.9%) (P = .015) in the non-calcific RCT group, respectively. Logistic regression showed that the independent predictors of calcific RCT included a history of nephrolithiasis (OR, 4.38; 95% CI: 1.61-11.92, P = .004) and a history of cholelithiasis (OR, 3.83; 95% CI: 1.64-8.94, P = .002). In patients with calcific RCT, the occurrence of lithiasis was significantly associated in the bivariate analysis with higher age, body mass index, fasting blood sugar, and HbA1c (all with P < .05), but only with the presence of another site of calcific tendinopathy than the shoulder (OR, 3.11; 95% CI: 1.12-8.65, P = .03) in the multivariate analysis. Nephrolithiasis and/or cholelithiasis are associated with calcific RCT, and their presence predicts calcific RCT at least 3 times. Further research is required to determine the common risk factors and preventive measures against lithogenesis in patients with calcific RCT, nephrolithiasis, and cholelithiasis.

Is renal dysfunction amplified in an arginine vasopressin induced rat model of preeclampsia?

Renal dysfunction is important in preeclampsia (PE) pathophysiology and has not been fully explored in the arginine vasopressin (AVP) rat model of PE. This study aimed to determine kidney toxicity associated with this model. Female Sprague Dawley rats (n = 24) were subcutaneously infused with AVP or saline for 18 days. Urine samples (GD8, 14 and 18) were used to determine the levels of albumin, VEGF-A, clusterin, NGAL/Lipocalin-2, KIM-1, cystatin C, TIMP-1, β2M and OPN via Multiplex ELISAs. Albumin, and NGAL/lipocalin-2 were significantly elevated in the PAVP vs PS group on GD14 and GD18 (p < 0.001) respectively. VEGF-A significantly decreased in the pregnant vs non-pregnant groups on GD14 and 18 (p < 0.001). Clusterin (p < 0.001) and OPN (p < 0.05) were significantly higher in the PAVP vs PS group on GD18. Cystatin C and KIM-1 are significantly upregulated in the PAVP vs PS groups throughout gestation (p < 0.05). β2M is significantly elevated in the PAVP vs PS group on GD14 and 18 (p < 0.05). AVP elevated the urinary levels of the kidney injury biomarkers and replicated the renal dysfunction associated with PE development. Our findings confirm the potential applications of this model in studying the mechanisms underlying renal damage in PE.

Identification of ligand and receptor interactions in CKD and MASH through the integration of single cell and spatial transcriptomics

BACKGROUND

Chronic Kidney Disease (CKD) and Metabolic dysfunction-associated steatohepatitis (MASH) are metabolic fibroinflammatory diseases. Combining single-cell (scRNAseq) and spatial transcriptomics (ST) could give unprecedented molecular disease understanding at single-cell resolution. A more comprehensive analysis of the cell-specific ligand-receptor (L-R) interactions could provide pivotal information about signaling pathways in CKD and MASH. To achieve this, we created an integrative analysis framework in CKD and MASH from two available human cohorts.

RESULTS

The analytical framework identified L-R pairs involved in cellular crosstalk in CKD and MASH. Interactions between cell types identified using scRNAseq data were validated by checking the spatial co-presence using the ST data and the co-expression of the communicating targets. Multiple L-R protein pairs identified are known key players in CKD and MASH, while others are novel potential targets previously observed only in animal models.

CONCLUSION

Our study highlights the importance of integrating different modalities of transcriptomic data for a better understanding of the molecular mechanisms. The combination of single-cell resolution from scRNAseq data, combined with tissue slide investigations and visualization of cell-cell interactions obtained through ST, paves the way for the identification of future potential therapeutic targets and developing effective therapies.

Inorganic Pyrophosphate at Serum Concentration May Not Be Able to Inhibit Mineralization: A Study in Aqueous Solutions and Serum

The constituent ions of calcium phosphate in body fluids are in the supersaturated state and tend to form minerals physiologically or pathologically. Inorganic pyrophosphate (PPi) has been considered as one of the most important inhibitors against the formation of calcium phosphate minerals. However, serum PPi concentrations in humans are maintained at a level of several μmol/L, and its effectiveness and mechanism for mineralization inhibition remain ambiguous. Therefore, this work studied the mineralization process in an aqueous solution, explored the effective inhibitory concentration of PPi by titration, and characterized the species during the reactions. We find that PPi at a normal serum concentration does not inhibit mineralization significantly. Such a conclusion was further confirmed in the PPi-added serum. This work indicates that PPi may not be a major direct inhibitor of mineralization in serum and possibly functions via alternative mechanisms.

The development of lateral flow devices for urinary biomarkers to assess kidney health

Serum creatinine levels are insensitive to real-time changes in kidney function or injury. There is a growing interest in assessing kidney injury by measuring biomarkers in body fluid. From our previous studies, we identified and reported three urinary biomarkers namely Uromodulin (UMOD), Osteopontin (OPN), and Interleukin-9 (IL-9) to be associated with kidney health. The availability of a rapid point-of-care test for these urinary biomarkers will potentially accelerate its applicability and accessibility. In this study, we aimed to develop novel lateral flow device (LFD) for UMOD, OPN and IL-9. We tested paired antibodies using Enzyme Linked Immunosorbent Assay wherein we observed functionality only for UMOD and OPN and not for IL-9. A conjugation buffer pH of 7.8 and 8.5 was found suitable at a detection antibody concentration of 15 µg/mL for LFD development. The developed LFDs were found to quantitatively measure UMOD standard (LLOD of 80,000 pg/mL) and OPN standard (LLOD of 8600 pg/mL) respectively. The LFD was also able to measure human urinary UMOD and OPN with a percent CV of 12.12 and 5.23 respectively.

Identification of molecular markers for predicting the severity of heart failure after AMI: An Olink precision proteomic study

BACKGROUND

Acute myocardial infarction (AMI) still has a high incidence of varying degrees of heart failure (HF). The aim of this study is to identify new molecular markers for predicting the severity of HF after AMI.

METHODS

We analyzed demographic indicators, past medical history, clinical indicators, major adverse cardiac events (MACEs) and molecular markers in patients with different Killip classifications after AMI. Olink proteomics was used to explore new molecular markers for predicting different severity of HF after AMI.

RESULTS

Neutrophil count was the independent risk factors for in-hospital MACEs. Nineteen differentially expressed proteins (DEPs) increased significantly with increasing Killip classification. Five DEPs were also found to have an AUC (95 % CI) value greater than 0.8: GDF-15, NT-pro BNP, TNF-R2, TNF-R1 and TFF3.

CONCLUSIONS

Neutrophil count, GDF-15, TNF-R2, TNF-R1 and TFF3 were closely related to the Killip classification of HF after AMI, which suggests that the inflammatory response plays an important role in the severity of HF after AMI and that regulating inflammation might become a new target for controlling HF.

Shared and Distinct Renal Transcriptome Signatures in 3 Standard Mouse Models of Chronic Kidney Disease

INTRODUCTION

Several mouse models with diverse disease etiologies are used in preclinical research for chronic kidney disease (CKD). Here, we performed a head-to-head comparison of renal transcriptome signatures in standard mouse models of CKD to assess shared and distinct molecular changes in three mouse models commonly employed in preclinical CKD research and drug discovery.

METHODS

All experiments were conducted on male C57BL/6J mice. Mice underwent sham, unilateral ureter obstruction (UUO), or unilateral ischemic-reperfusion injury (uIRI) surgery and were terminated two- and 6-weeks post-surgery, respectively. The adenine-supplemented diet-induced (ADI) model of CKD was established by feeding with adenine diet for 6 weeks and compared to control diet feeding. For all models, endpoints included plasma biochemistry, kidney histology, and RNA sequencing.

RESULTS

All models displayed increased macrophage infiltration (F4/80 IHC) and fibrosis (collagen 1a1 IHC). Compared to corresponding controls, all models were characterized by an extensive number of renal differentially expressed genes (≥11,000), with a notable overlap in transcriptomic signatures across models. Gene expression markers of fibrosis, inflammation, and kidney injury supported histological findings. Interestingly, model-specific transcriptome signatures included several genes representing current drug targets for CKD, emphasizing advantages and limitations of the three CKD models in preclinical target and drug discovery.

CONCLUSION

The UUO, uIRI, and ADI mouse models of CKD have significant commonalities in their renal global transcriptome profile. Model-specific renal transcriptional signatures should be considered when selecting the specific model in preclinical target and drug discovery.

Assessment of osteopontin as an early nephrotoxicity indicator in human renal proximal tubule cells and its application in evaluating lanthanum-induced nephrotoxicity

Nephrotoxicity is a common adverse effect induced by various chemicals, necessitating the development of reliable toxicity screening models for nephrotoxicity assessment. In this study, we assessed a group of nephrotoxicity indicators derived from different toxicity pathways, including conventional endpoints and kidney tubular injury biomarkers such as clusterin (CLU), kidney injury molecule-I (KIM-1), osteopontin (OPN), and neutrophil gelatinase-associated lipocalin (NGAL), using HK-2 and induced pluripotent stem cells (iPSCs)-derived renal proximal tubular epithelial-like cells (PTLs). Among the biomarkers tested, OPN emerged as the most discerning and precise marker. The predictive potential of OPN was tested using a panel of 10 nephrotoxic and 5 non-nephrotoxic compounds. The results demonstrated that combining OPN with the half-maximal inhibitory concentration (IC50) enhanced the diagnostic accuracy in both cellular models. Additionally, PTLs cells showed superior predictive efficacy for nephrotoxicity compared to HK-2 cells in this investigation. The two cellular models were utilized to evaluate the nephrotoxicity of lanthanum. The findings indicated that lanthanum possesses nephrotoxic properties; however, the degree of nephrotoxicity was relatively low, consistent with the outcomes of in vivo experiments.

Efficacy of parsley seed-supplemented bread in improving serum osteopontin level and renal health in obese women: A nutritional intervention study

BACKGROUND

Obesity is a global epidemic and a major contributor to chronic kidney disease worldwide. This interventional study aimed to evaluate the effects of a unique parsley seed bread and a healthy balanced diet on serum osteopontin level and renal function in obese women.

METHODS

A total of 85 obese women (BMI, 35.68 ± 0.47 kg/m2) participated in an 8-week nutritional intervention comprising two phases. In the first phase, participants consumed 100 g of ground parsley seed bread along with a healthy balanced low caloric regimen for four weeks. In the second phase, Baladi bread was substituted for the supplement, providing an equal caloric intake, for another four weeks. Relevant Anthropometric measurements, blood pressure, dietary recall, and biochemical parameters (osteopontin, IL-1β, IL-10, kidney functions, and lipid parameters) were assessed before and after each intervention phase.

RESULTS

Following the initial intervention phase, there were significant improvements in all recorded mean anthropometric parameters (p ≤ 0.001). Lipid parameters and risk factors also significantly decreased (p < 0.05), while osteopontin, creatinine, and IL-1β levels decreased significantly. eGFR, creatinine clearance, IL-10 increased. However, these improved values returned to elevated levels after the omission of the supplement in the second phase. There was a significant negative correlation between osteopontin and creatinine, creatinine clearance, and IL-10.

CONCLUSION

The combined effect of the novel parsley seed-based intervention and a healthy balanced low-calorie regimen demonstrated improvements in osteopontin level associated with renal disorders, and inflammation, in addition to dyslipidemia in obese women. This suggests a promising approach for improving and protecting kidney disorders.

Identification of Senescence-Associated Biomarkers in Diabetic Glomerulopathy Using Integrated Bioinformatics Analysis

Background

Cellular senescence is thought to play a significant role in the onset and development of diabetic nephropathy. The goal of this study was to explore potential biomarkers associated with diabetic glomerulopathy from the perspective of senescence.

Methods

Datasets about human glomerular biopsy samples related to diabetic nephropathy were systematically obtained from the Gene Expression Omnibus database. Hub senescence-associated genes were investigated by differential gene analysis and Least Absolute Shrinkage and Selection Operator analysis. Cluster analysis was employed to identify senescence molecular subtypes. A single-cell dataset was used to validate the above findings and further evaluate the senescence environment. The relationship between these genes and the glomerular filtration rate was explored based on the Nephroseq database. These gene expressions have also been explored in various kidney diseases.

Results

Twelve representative senescence-associated genes (VEGFA, IQGAP2, JUN, PLAT, ETS2, ANG, MMP14, VEGFC, SERPINE2, CXCR2, PTGES, and EGF) were finally identified. Biological changes in immune inflammatory response, cell cycle regulation, metabolic regulation, and immune microenvironment have been observed across different molecular subtypes. The above results were also validated based on single-cell analysis. Additionally, we also identified several significantly altered cell communication pathways, including COLLAGEN, PTN, LAMININ, SPP1, and VEGF. Finally, almost all these genes could well predict the occurrence of diabetic glomerulopathy based on receiver operating characteristic analysis and are associated with the glomerular filtration rate. These genes are differently expressed in various kidney diseases.

Conclusion

The present study identified potential senescence-associated biomarkers and further explored the heterogeneity of diabetic glomerulopathy that might provide new insights into the diagnosis, assessment, management, and personalized treatment of DN.

Association of the rs1126616 and rs9138 Variants in the SPP1 Gene among Mexican Patients with Systemic Lupus Erythematosus and Lupus Nephritis

Systemic lupus erythematosus (SLE) is a multisystem disease considered a prototype of the main autoimmune disease and presents serious complications, such as lupus nephritis (LN), which generates a significant impact on morbidity and mortality. The SPP1 gene encodes the osteopontin (OPN) protein, which plays a crucial role in the regulation of inflammation and immunity. The variants rs1126616 and rs9138 of this gene have been associated with the inflammatory response. The study aims to analyze the association of the rs1126616 and rs9138 variants of the SPP1 gene in SLE Mexican-Mestizo patients without LN (SLE-LN). In this cross-sectional study, a total of 171 genomic DNA samples from SLE patients were clinically confirmed, of which 111 were SLE without LN, 60 were SLE with LN, and 100 healthy individuals were included as reference group. The rs1126616 variant was genotyped using PCR-RFLPs, and the rs9138 variant was genotyped using qPCR TaqMan. The TT genotype, the recessive model [OR 2.76 (95% CI 1.31-5.82), p = 0.011], and the T allele [OR 2.0 (95% CI 1.26-3.16), p = 0.003] of the rs1126616 variant are risk factors for SLE with LN. By contrast, the rs9138 variant did not show statistically significant differences among SLE patients stratified by LN. In our study of SLE Mexican-Mestizo patients with and without NL, demographic and clinical characteristics do not differ from other SLE populations, and the TT genotype of the rs1126616 variant of the SPP1 gene confers a risk factor for the presentation of LN. Otherwise, the rs9138 variant did not show association with NL.

Osteopontin in cancer

Osteopontin (OPN) is a heavily post-translationally modified protein with a molecular weight of 44-70 kDa, depending on the degree of glycosylation. OPN is involved in various biological processes, including bone remodeling, immune response, cell adhesion, migration, and survival. It is essential for controlling osteoclast and osteoblast activity for maintaining bone mass and bone strength. Additionally, OPN has been linked to cardiovascular, inflammatory illnesses, as well as the onset and progression of cancer. OPN is a multifunctional protein that can interact with a variety of cell surface receptors, such as integrins, CD44, the urokinase-type plasminogen activator receptor (uPAR), as well as extracellular matrix (ECM) components (e.g. collagen and hydroxyapatite). These interactions contribute to its wide range of biological functions in general and has significant implications for bone biology, immunology and cancer, specifically. In this chapter, we summarize the structure of OPN with a focus on its molecular mechanisms of action in various cancers.

Single-cell sequencing dissects the transcriptional identity of activated fibroblasts and identifies novel persistent distal tubular injury patterns in kidney fibrosis

Examining kidney fibrosis is crucial for mechanistic understanding and developing targeted strategies against chronic kidney disease (CKD). Persistent fibroblast activation and tubular epithelial cell (TEC) injury are key CKD contributors. However, cellular and transcriptional landscapes of CKD and specific activated kidney fibroblast clusters remain elusive. Here, we analyzed single cell transcriptomic profiles of two clinically relevant kidney fibrosis models which induced robust kidney parenchymal remodeling. We dissected the molecular and cellular landscapes of kidney stroma and newly identified three distinctive fibroblast clusters with "secretory", "contractile" and "vascular" transcriptional enrichments. Also, both injuries generated failed repair TECs (frTECs) characterized by decline of mature epithelial markers and elevation of stromal and injury markers. Notably, frTECs shared transcriptional identity with distal nephron segments of the embryonic kidney. Moreover, we identified that both models exhibited robust and previously unrecognized distal spatial pattern of TEC injury, outlined by persistent elevation of renal TEC injury markers including Krt8 and Vcam1, while the surviving proximal tubules (PTs) showed restored transcriptional signature. We also found that long-term kidney injuries activated a prominent nephrogenic signature, including Sox4 and Hox gene elevation, which prevailed in the distal tubular segments. Our findings might advance understanding of and targeted intervention in fibrotic kidney disease.

Study of Osteopontin as a Marker of Arteriovenous Shunt Stenosis in Hemodialysis Patients

INTRODUCTION

Although arteriovenous fistula (AVF) is the recommended access for hemodialysis (HD), it carries a high risk for stenosis. Since osteopontin (OPN) is implicated in the process of vascular calcification in HD patients, OPN may be a marker for AVF stenosis. The present study evaluated OPN as a potential marker of AVF stenosis in HD patients.

METHODS

Diagnosing a stenotic lesion was made by combining B mode with color and pulse wave Doppler imaging. Criteria for diagnosis of stenotic AVF included 50% reduction in diameter in B mode in combination with a 2-3-fold increase of peak systolic velocity compared with the unaffected segment.

RESULTS

The present study included 60 HD patients with stenotic AVF and 60 patients with functional AVF. Comparison between the two groups revealed that patients in the former group had significantly higher serum OPN levels [median (IQR): 17.1 (12.1-30.4) vs 5.8 (5.0-10.0) ng/mL, p<0.001]. All patients were classified into those with low (< median) and with high (≥ median) OPN levels. Comparison between these groups revealed that the former group had a significantly lower frequency of stenotic AVF (31.7 vs 68.3%, p<0.001) and a longer time to AVF stenosis [mean (95% CI): 68.4 (54.7-82.1) vs 46.5 (39.6-53.4) months, p=0.001].

CONCLUSION

OPN levels in HD patients may be useful markers for predicting and detecting AVF stenosis.

Hepatorenal Syndrome-Novel Insights into Diagnostics and Treatment

Hepatorenal syndrome (HRS) is a disorder associated with cirrhosis and renal impairment, with portal hypertension as its major underlying cause. Moreover, HRS is the third most common cause of acute kidney injury, thus creating a major public health concern. This review summarizes the available information on the pathophysiological implications of HRS. We discuss pathogenesis associated with HRS. Mechanisms such as dysfunction of the circulatory system, bacterial infection, inflammation, impaired renal autoregulation, circulatory, and others, which have been identified as critical pathways for development of HRS, have become easier to diagnose in recent years. Additionally, relatively recently, renal dysfunction biomarkers have been found indicating renal injury, which are involved in the pathophysiology of HRS. This review also summarizes the available information on the management of HRS, focusing on vasoconstrictive drugs, renal replacement therapy, and liver transplant together with currently being investigated novel therapies. Analyzing new discoveries for the underlying causes of this condition assists the general research to improve understanding of the mechanism of pathophysiology and thus prevention of HRS.

The critical role of osteopontin (OPN) in fibrotic diseases

Fibrosis is a pathological condition characterized by the excessive deposition of extracellular matrix components in tissues and organs, leading to progressive architectural remodelling and contributing to the development of various diseases. Osteopontin (OPN), a highly phosphorylated glycoprotein, has been increasingly recognized for its involvement in the progression of tissue fibrosis. This review provides a comprehensive overview of the genetic and protein structure of OPN and focuses on our current understanding of the role of OPN in the development of fibrosis in the lungs and other tissues. Additionally, special attention is given to the potential of OPN as a biomarker and a novel therapeutic target in the treatment of fibrosis.

A novel multiplex biomarker panel for profiling human acute and chronic kidney disease

Acute and chronic kidney disease continues to confer significant morbidity and mortality in the clinical setting. Despite high prevalence of these conditions, few validated biomarkers exist to predict kidney dysfunction. In this study, we utilized a novel kidney multiplex panel to measure 21 proteins in plasma and urine to characterize the spectrum of biomarker profiles in kidney disease. Blood and urine samples were obtained from age-/sex-matched healthy control subjects (HC), critically-ill COVID-19 patients with acute kidney injury (AKI), and patients with chronic or end-stage kidney disease (CKD/ESKD). Biomarkers were measured with a kidney multiplex panel, and results analyzed with conventional statistics and machine learning. Correlations were examined between biomarkers and patient clinical and laboratory variables. Median AKI subject age was 65.5 (IQR 58.5-73.0) and median CKD/ESKD age was 65.0 (IQR 50.0-71.5). Of the CKD/ESKD patients, 76.1% were on hemodialysis, 14.3% of patients had kidney transplant, and 9.5% had CKD without kidney replacement therapy. In plasma, 19 proteins were significantly different in titer between the HC versus AKI versus CKD/ESKD groups, while NAG and RBP4 were unchanged. TIMP-1 (PPV 1.0, NPV 1.0), best distinguished AKI from HC, and TFF3 (PPV 0.99, NPV 0.89) best distinguished CKD/ESKD from HC. In urine, 18 proteins were significantly different between groups except Calbindin, Osteopontin and TIMP-1. Osteoactivin (PPV 0.95, NPV 0.95) best distinguished AKI from HC, and β2-microglobulin (PPV 0.96, NPV 0.78) best distinguished CKD/ESKD from HC. A variety of correlations were noted between patient variables and either plasma or urine biomarkers. Using a novel kidney multiplex biomarker panel, together with conventional statistics and machine learning, we identified unique biomarker profiles in the plasma and urine of patients with AKI and CKD/ESKD. We demonstrated correlations between biomarker profiles and patient clinical variables. Our exploratory study provides biomarker data for future hypothesis driven research on kidney disease.

Predicting autosomal dominant polycystic kidney disease progression: review of promising Serum and urine biomarkers

Autosomal dominant polycystic kidney disease (ADPKD) is one of the leading causes of end-stage renal disease. In spite of the recent tremendous progress in the understanding of ADPKD pathogenesis, the molecular mechanisms of the disease remain incompletely understood. Considering emerging new targeted therapies for ADPKD, it has become crucial to disclose easily measurable and widely available biomarkers for identifying patients with future rapid disease progression. This review encompasses all the research with a shared goal of identifying promising serum or urine biomarkers for predicting ADPKD progression or response to therapy. The rate of the ADPKD progress varies significantly between patients. The phenotypic variability is only partly explained by the underlying genetic lesion diversity. Considering significant decline in kidney function in ADPKD is not usually evident until at least 50% of the parenchyma has been destroyed, conventional kidney function measures, such as glomerular filtration rate (GFR), are not suitable for monitoring disease progression in ADPKD, particularly in its early stages. Since polycystic kidney enlargement usually precedes the decline in GFR, height-adjusted total kidney volume (ht-TKV) has been accepted as an early biomarker for assessing disease severity in ADPKD patients. However, since measuring ht-TKV is time-consuming and observer-dependent, the identification of a sensitive and quickly measurable biomarker is of a great interest for everyday clinical practice. Throughout the last decade, due to development of proteomic and metabolomic techniques and the enlightenment of multiple molecular pathways involved in the ADPKD pathogenesis, a number of urine and serum protein biomarkers have been investigated in ADPKD patients, some of which seem worth of further exploring. These include copeptin, angiotensinogen, monocyte chemoattractant protein 1, kidney injury molecule-1 and urine-to-plasma urea ratio among many others. The aim of the current review is to provide an overview of all of the published evidence on potentially clinically valuable serum and urine biomarkers that could be used for predicting disease progression or response to therapy in patients with ADPKD. Hopefully, this review will encourage future longitudinal prospective clinical studies evaluating proposed biomarkers as prognostic tools to improve management and outcome of ADPKD patients in everyday clinical practice.

Gut microbiota and neonatal acute kidney injury biomarkers

One of the most frequent issues in newborns is acute kidney injury (AKI), which can lengthen their hospital stay or potentially raise their chance of dying. The gut-kidney axis establishes a bidirectional interplay between gut microbiota and kidney illness, particularly AKI, and demonstrates the importance of gut microbiota to host health. Since the ability to predict neonatal AKI using blood creatinine and urine output as evaluation parameters is somewhat constrained, a number of interesting biomarkers have been developed. There are few in-depth studies on the relationships between these neonatal AKI indicators and gut microbiota. In order to gain fresh insights into the gut-kidney axis of neonatal AKI, this review is based on the gut-kidney axis and describes relationships between gut microbiota and neonatal AKI biomarkers.

The Urinary Concentrations of Neutrophil Gelatinase-Associated Lipocalin, Cystatin C and Osteopontin in the Healthy Term and Stable Preterm Neonates: A Pilot Study

BACKGROUND

In neonates, the assessment of kidney function with serum creatinine is limited; therefore, more effective biomarkers are needed.

AIM

The study aimed at analyzing the concentrations of renal biomarkers (osteopontin, cystatin C, and NGAL) in neonates.

MATERIAL AND METHODS

The study included 80 term and 20 preterm neonates aged 28-33 weeks of gestation. Biomarkers were measured in urine. Term neonates' urine was collected on the 1st day of life. Preterm neonates' urine was collected on the 1st, 8th, 15th, 22nd day of life. Biomarkers' concentrations were normalized to urinary creatinine (cr.) and presented as urinary biomarker/cr. ratios.

RESULTS

Median values of biomarker/creatine ratios in term and preterm neonates were the following: cystatin C/cr.: 7.26 and 439.49; osteopontin/cr.: 135.86 and 1633.37; NGAL/cr. in girls: 212.14 and 256.93; and NGAL/cr. in boys 27.123 and 65.29 ng/mg cr. In preterm neonates the cystatin C/cr. ratio was higher on the 1st than on the 8th day. The osteopontin/cr. ratio did not differ between the days. The NGAL/cr. ratio in girls was higher on the 8th than on the 22nd day, and in boys, the lowest was on the 22nd day.

CONCLUSIONS

Prematurity in stable, Caucasian neonates might cause higher osteopontin and cystatin C excretion, but not NGAL. The excretion of NGAL and cystatin C, but not osteopontin, may change during first weeks of premature neonate's life.

Recent Advances of Proteomics in Management of Acute Kidney Injury

Acute Kidney Injury (AKI) is currently recognized as a life-threatening disease, leading to an exponential increase in morbidity and mortality worldwide. At present, AKI is characterized by a significant increase in serum creatinine (SCr) levels, typically followed by a sudden drop in glomerulus filtration rate (GFR). Changes in urine output are usually associated with the renal inability to excrete urea and other nitrogenous waste products, causing extracellular volume and electrolyte imbalances. Several molecular mechanisms were proposed to be affiliated with AKI development and progression, ultimately involving renal epithelium tubular cell-cycle arrest, inflammation, mitochondrial dysfunction, the inability to recover and regenerate proximal tubules, and impaired endothelial function. Diagnosis and prognosis using state-of-the-art clinical markers are often late and provide poor outcomes at disease onset. Inappropriate clinical assessment is a strong disease contributor, actively driving progression towards end stage renal disease (ESRD). Proteins, as the main functional and structural unit of the cell, provide the opportunity to monitor the disease on a molecular level. Changes in the proteomic profiles are pivotal for the expression of molecular pathways and disease pathogenesis. Introduction of highly-sensitive and innovative technology enabled the discovery of novel biomarkers for improved risk stratification, better and more cost-effective medical care for the ill patients and advanced personalized medicine. In line with those strategies, this review provides and discusses the latest findings of proteomic-based biomarkers and their prospective clinical application for AKI management.

Single-cell sequencing dissects the transcriptional identity of activated fibroblasts and identifies novel persistent distal tubular injury patterns in kidney fibrosis

Examining kidney fibrosis is crucial for mechanistic understanding and developing targeted strategies against chronic kidney disease (CKD). Persistent fibroblast activation and tubular epithelial cell (TEC) injury are key CKD contributors. However, cellular and transcriptional landscapes of CKD and specific activated kidney fibroblast clusters remain elusive. Here, we analyzed single cell transcriptomic profiles of two clinically relevant kidney fibrosis models which induced robust kidney parenchymal remodeling. We dissected the molecular and cellular landscapes of kidney stroma and newly identified three distinctive fibroblast clusters with "secretory", "contractile" and "vascular" transcriptional enrichments. Also, both injuries generated failed repair TECs (frTECs) characterized by decline of mature epithelial markers and elevation of stromal and injury markers. Notably, frTECs shared transcriptional identity with distal nephron segments of the embryonic kidney. Moreover, we identified that both models exhibited robust and previously unrecognized distal spatial pattern of TEC injury, outlined by persistent elevation of renal TEC injury markers including Krt8, while the surviving proximal tubules (PTs) showed restored transcriptional signature. Furthermore, we found that long-term kidney injuries activated a prominent nephrogenic signature, including Sox4 and Hox gene elevation, which prevailed in the distal tubular segments. Our findings might advance understanding of and targeted intervention in fibrotic kidney disease.

Osteopontin as a Biomarker in Chronic Kidney Disease

Osteopontin (OPN) is a ubiquitously expressed protein with a wide range of physiological functions, including roles in bone mineralization, immune regulation, and wound healing. OPN has been implicated in the pathogenesis of several forms of chronic kidney disease (CKD) where it promotes inflammation and fibrosis and regulates calcium and phosphate metabolism. OPN expression is increased in the kidneys, blood, and urine of patients with CKD, particularly in those with diabetic kidney disease and glomerulonephritis. The full-length OPN protein is cleaved by various proteases, including thrombin, matrix metalloproteinase (MMP)-3, MMP-7, cathepsin-D, and plasmin, producing N-terminal OPN (ntOPN), which may have more detrimental effects in CKD. Studies suggest that OPN may serve as a biomarker in CKD, and while more research is needed to fully evaluate and validate OPN and ntOPN as CKD biomarkers, the available evidence suggests that they are promising candidates for further investigation. Targeting OPN may be a potential treatment strategy. Several studies show that inhibition of OPN expression or activity can attenuate kidney injury and improve kidney function. In addition to its effects on kidney function, OPN has been linked to cardiovascular disease, which is a major cause of morbidity and mortality in patients with CKD.

Osteopontin Promotes Macrophage M1 Polarization by Activation of the JAK1/STAT1/HMGB1 Signaling Pathway in Nonalcoholic Fatty Liver Disease

Background and Aims

Osteopontin (OPN) is reported to be associated with the pathogenesis of nonalcoholic fatty liver disease (NAFLD). However, the function of OPN in NAFLD is still inconclusive. Therefore, our aim in this study was to evaluate the role of OPN in NAFLD and clarify the involved mechanisms.

Methods

We analyzed the expression change of OPN in NAFLD by bioinformatic analysis, qRT-PCR, western blotting and immunofluorescence staining. To clarify the role of OPN in NAFLD, the effect of OPN from HepG2 cells on macrophage polarization and the involved mechanisms were examined by FACS and western blotting.

Results

OPN was significantly upregulated in NAFLD patients compared with normal volunteers by microarray data, and the high expression of OPN was related with disease stage and progression. OPN level was also significantly increased in liver tissue samples of NAFLD from human and mouse, and in HepG2 cells treated with oleic acid (OA). Furthermore, the supernatants of OPN-treated HepG2 cells promoted the macrophage M1 polarization. Mechanistically, OPN activated the janus kinase 1(JAK1)/signal transducers and activators of transcription 1 (STAT1) signaling pathway in HepG2 cells, and consequently HepG2 cells secreted more high-mobility group box 1 (HMGB1), thereby promoting macrophage M1 polarization.

Conclusions

OPN promoted macrophage M1 polarization by increasing JAK1/STAT1-induced HMGB1 secretion in hepatocytes.

Omics are Getting Us Closer to Understanding IgA Nephropathy

During the last decade, thanks to omics technologies, new light has been shed on the pathogenesis of many diseases. Genomics, epigenomics, transcriptomics, and proteomics have helped to provide a better understanding of the origin and heterogeneity of several diseases. However, the risk factors for most autoimmune diseases remain unknown. The successes and pitfalls of omics have also been observed in nephrology, including immunoglobulin A nephropathy (IgAN), the most common form of glomerulonephritis and a principal cause of end-stage renal disease worldwide. Unfortunately, the immense progress in basic research has not yet been followed by the satisfactory development of a targeted treatment. Although, most omics studies describe changes in the immune system, there is still insufficient data to apply their results in the constantly evolving multi-hit pathogenesis model and thus do to provide a complete picture of the disease. Here, we describe recent findings regarding the pathophysiology of IgAN and link omics studies with immune system dysregulation. This review provides insights into specific IgAN markers, which may lead to the identification of potential targets for personalised treatment in the future.

The Role and Clinical Relevance of Osteopontin in Allergic Airway Diseases

The airway epithelium is exposed to numerous external irritants including infectious agents, environmental allergens, and atmospheric pollutants, releasing epithelial cytokines including thymic stromal lymphopoietin (TSLP), IL-33, and IL-25 and initiating downstream type 2 (IL-4, IL-13, and IL-5) and IgE-driven pathways. These pathways trigger the initiation and progression of allergic airway diseases, including chronic rhinosinusitis with nasal polyps (CRSwNP), allergic rhinitis (AR), and allergic asthma. However, the use of biological agents that target downstream cytokines, such as IL-5, IL-4, and IL-13 receptors and IgE, might not be sufficient to manage some patients successfully. Instead of blocking downstream cytokines, targeting upstream epithelial cytokines has been proposed to address the complex immunologic networks associated with allergic airway diseases. Osteopontin (OPN), an extracellular matrix glyco-phosphoprotein, is a key mediator involved in Th1-related diseases, including systemic lupus erythematosus, multiple sclerosis, inflammatory bowel disease, and rheumatoid arthritis. Emerging evidence, including ours, indicates that epithelial-cell-derived OPN also plays an essential role in Th2-skewed airway diseases, including CRSwNP, AR, and allergic asthma involving the Th17 response. Therefore, we reviewed the current knowledge of epithelial-cell-derived OPN in the pathogenesis of three type-2-biased airway diseases and provided a direction for its future investigation and clinical relevance.

Prediction of cellular targets in diabetic kidney diseases with single-cell transcriptomic analysis of db/db mouse kidneys

Diabetic kidney disease is the leading cause of impaired kidney function, albuminuria, and renal replacement therapy (dialysis or transplantation), thus placing a large burden on health-care systems. This urgent event requires us to reveal the molecular mechanism of this disease to develop more efficacious treatment. Herein, we reported single-cell RNA sequencing analyses in kidneys of db/db mouse, an animal model for type 2 diabetes and diabetic kidney disease. We first analyzed the hub genes expressed differentially in the single cell resolution transcriptome map of the kidneys. Then we figured out the communication among the renal and immune cells in the kidneys. Data from this report may provide novel information for better understanding the cell-specific targets involved in the aetiologia of type 2 diabetic kidney disease and for cell communication and signaling between renal cells and immune cells of this complex disease.

Cell Protection and Crystal Endocytosis Inhibition by Sulfated Laminaria Polysaccharides Against Nano-COM-Induced Oxidative Damage in Renal Epithelial Cells

Background: The damage to renal tubular epithelial cells is closely related to the formation of kidney stones. At present, research on drugs that can protect cells from damage remains limited. Methods: This study aims to explore the protective effects of four different sulfate groups (-OSO₃ ^-) of Laminaria polysaccharides (SLPs) on human kidney proximal tubular epithelial (HK-2) cells and determine the difference in the endocytosis of nano-sized calcium oxalate monohydrate (COM) crystals before and after protection. COM with a size of 230 ± 80 nm was used to damage HK-2 cells to establish a damage model. The protection capability of SLPs (LP0, SLP1, SLP2, and SLP3) with -OSO₃ ^- contents of 0.73, 15, 23, and 31%, respectively, against COM crystal damage and the effect of SLPs on the endocytosis of COM crystals were studied. Results: Compared with that of the SLP-unprotected COM-injured group, the cell viability of the SLP-protected group was improved, healing capability was enhanced, cell morphology was restored, production of reactive oxygen species was reduced, mitochondrial membrane potential and lysosome integrity were increased, intracellular Ca²⁺ level and autophagy were decreased, cell mortality was reduced, and internalized COM crystals were lessened. The capability of SLPs to protect cells from damage and inhibit the endocytosis of crystals in cells enhanced with an increase in the -OSO₃ ^- content of SLPs. Conclusions: SLPs with a high -OSO₃ ^- content may become a potential green drug for preventing the formation of kidney stones.

Curcumin alleviated oxidation stress injury by mediating osteopontin in nephrolithiasis rats

PURPOSE

To explore the role and mechanism of curcumin (Cur) in reducing oxidative stress damage in rats with nephrolithiasis induced by ethylene glycol (EG).

METHODS

Thirty male rats were divided into normal control, model, positive (10% potassium citrate), Cur-10 (10 mg/kg curcumin) and Cur-20 (20 mg/kg curcumin) groups.

RESULTS

The results of kidney tissue section stained by hematoxylin-eosin and von Kossa showed that curcumin treatment can inhibit the formation of kidney stones. The biochemical test results showed that the urea (Ur), creatinine (Cr), uric acid (UA), inorganic phosphorus and Ca2+ concentrations in urine decreased after being treated with curcumin. There were significant differences between different doses of curcumin (P < 0.05). Compared with the Cur-10 group, Cur-20 had a more significant inhibitory effect on malondialdehyde (MDA) (P < 0.05). In addition, reverse transcription polymerase chain reaction (PCR) detection and immunohistochemical results indicated that the osteopontin (OPN) in the kidney was significantly reduced after curcumin treatment.

CONCLUSIONS

Curcumin could reduce the oxidative stress damage caused by EG-induced kidney stones.

Comprehensive single-cell transcriptional profiling defines shared and unique epithelial injury responses during kidney fibrosis

The underlying cellular events driving kidney fibrogenesis and metabolic dysfunction are incompletely understood. Here, we employed single-cell combinatorial indexing RNA sequencing to analyze 24 mouse kidneys from two fibrosis models. We profiled 309,666 cells in one experiment, representing 50 cell types/states encompassing epithelial, endothelial, immune, and stromal populations. Single-cell analysis identified diverse injury states of the proximal tubule, including two distinct early-phase populations with dysregulated lipid and amino acid metabolism, respectively. Lipid metabolism was defective in the chronic phase but was transiently activated in the very early stages of ischemia-induced injury, where we discovered increased lipid deposition and increased fatty acid β-oxidation. Perilipin 2 was identified as a surface marker of intracellular lipid droplets, and its knockdown in vitro disrupted cell energy state maintenance during lipid accumulation. Surveying epithelial cells across nephron segments identified shared and unique injury responses. Stromal cells exhibited high heterogeneity and contributed to fibrogenesis by epithelial-stromal crosstalk.

A molecular phenotypic screen reveals that lobetyolin alleviates cardiac dysfunction in 5/6 nephrectomized mice by inhibiting osteopontin

BACKGROUND

Cardiovascular diseases are the major cause of mortality in patients with advanced chronic kidney diseases. The predominant abnormality observed among this population is cardiac dysfunction secondary to myocardial remodelings, such as hypertrophy and fibrosis, emphasizing the need to develop potent therapies that maintain cardiac function in patients with end-stage renal disease.

AIMS

To identify potential compounds and their targets as treatments for cardiorenal syndrome type 4 (CRS) using molecular phenotyping and in vivo/in vitro experiments.

METHODS

Gene expression was assessed using bioinformatics and verified in animal experiments using 5/6 nephrectomized mice (NPM). Based on this information, a molecular phenotyping strategy was pursued to screen potential compounds. Picrosirius red staining, wheat germ agglutinin staining, Echocardiography, immunofluorescence staining, and real-time quantitative PCR (qPCR) were utilized to evaluate the effects of compounds on CRS in vivo. Furthermore, qPCR, immunofluorescence staining and flow cytometry were applied to assess the effects of these compounds on macrophages/cardiac fibroblasts/cardiomyocytes. RNA-Seq analysis was performed to locate the targets of the selected compounds. Western blotting was performed to validate the targets and mechanisms. The reversibility of these effects was tested by overexpressing Osteopontin (OPN).

RESULTS

OPN expression increased more remarkably in individuals with uremia-induced cardiac dysfunction than in other cardiomyopathies. Lobetyolin (LBT) was identified in the compound screen, and it improved cardiac dysfunction and suppressed remodeling in NPM mice. Additionally, OPN modulated the effect of LBT on cardiac dysfunction in vivo and in vitro. Further experiments revealed that LBT suppressed OPN expression via the phosphorylation of c-Jun N-terminal protein kinase (JNK) signaling pathway.

CONCLUSIONS

LBT improved CRS by inhibiting OPN expression through the JNK pathway. This study is the first to describe a cardioprotective effect of LBT and provides new insights into CRS drug discovery.

Identification of osteopontin as a urinary biomarker for autosomal dominant polycystic kidney disease progression

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD), one of the most common human monogenic diseases, is characterized by the presence of numerous fluid-filled renal cysts and is a leading cause of end-stage renal disease (ESRD). Urinary biomarkers may be useful for predicting the variable course of ADPKD progression from cyst growth to ESRD.

METHODS

To identify candidate urinary biomarkers of ADPKD progression, we used CRISPR/Cas9 genome editing to generate porcine fibroblasts with mono- and biallelic ADPKD gene knockout (PKD2+/- and PKD2-/-, respectively). We then performed RNA-sequencing analysis on these cells.

RESULTS

Levels of osteopontin (OPN), which is expressed by renal epithelial tubular cells and excreted into urine, were reduced in PKD2-/- cells but not in PKD2+/- cells. OPN levels were also reduced in the renal cyst cells of ADPKD patients. Next, we investigated whether OPN excretion was decreased in patients with ADPKD via enzyme-linked immunosorbent assay. OPN levels excreted into renal cyst cell culture media and urine from ADPKD patients were decreased. To investigate whether OPN can predict the rate of ADPKD progression, we compared urinary excretion of OPN in ADPKD patients with slow progression and those with rapid progression. Those with rapid progression had an estimated glomerular filtration rate of >60 mL/min/1.73 m2 . Urinary OPN excretion levels were lower in rapid progressors than in slow progressors.

CONCLUSION

These findings suggest that OPN is a useful urinary biomarker for predicting ADPKD progression.

Increased PHOSPHO1 expression mediates cortical bone mineral density in renal osteodystrophy

Patients with advanced chronic kidney disease (CKD) often present with skeletal abnormalities, a condition known as renal osteodystrophy (ROD). While tissue non-specific alkaline phosphatase (TNAP) and PHOSPHO1 are critical for bone mineralization, their role in the etiology of ROD is unclear. To address this, ROD was induced in both WT and Phospho1 knockout (P1KO) mice through dietary adenine supplementation. The mice presented with hyperphosphatemia, hyperparathyroidism, and elevated levels of FGF23 and bone turnover markers. In particular, we noted that in CKD mice, bone mineral density (BMD) was increased in cortical bone (P < 0.05) but decreased in trabecular bone (P < 0.05). These changes were accompanied by decreased TNAP (P < 0.01) and increased PHOSPHO1 (P < 0.001) expression in WT CKD bones. In P1KO CKD mice, the cortical BMD phenotype was rescued, suggesting that the increased cortical BMD of CKD mice was driven by increased PHOSPHO1 expression. Other structural parameters were also improved in P1KO CKD mice. We further investigated the driver of the mineralization defects, by studying the effects of FGF23, PTH, and phosphate administration on PHOSPHO1 and TNAP expression by primary murine osteoblasts. We found both PHOSPHO1 and TNAP expressions to be downregulated in response to phosphate and PTH. The in vitro data suggest that the TNAP reduction in CKD-MBD is driven by the hyperphosphatemia and/or hyperparathyroidism noted in these mice, while the higher PHOSPHO1 expression may be a compensatory mechanism. Increased PHOSPHO1 expression in ROD may contribute to the disordered skeletal mineralization characteristic of this progressive disorder.

A Biomarker‐Enhanced Model for Prediction of Acute Kidney Injury and Cardiovascular Risk Following Angiographic Procedures: CASABLANCA AKI Prediction Substudy

Background

The 2020 Acute Disease Quality Initiative Consensus provided recommendations on novel acute kidney injury biomarkers. In this study, we sought to assess the added value of novel kidney biomarkers to a clinical score in the CASABLANCA (Catheter Sampled Blood Archive in Cardiovascular Diseases) study.

Methods and Results

We evaluated individuals undergoing coronary and/or peripheral angiography and added 4 candidate biomarkers for acute kidney injury (kidney injury molecule‐1, interleukin‐18, osteopontin, and cystatin C) to a previously described contrast‐associated acute kidney injury (CA‐AKI) risk score. Participants were categorized into integer score groups based on the risk assigned by the biomarker‐enhanced CA‐AKI model. Risk for incident cardiorenal outcomes during a median 3.7 years of follow‐up was assessed. Of 1114 participants studied, 55 (4.94%) developed CA‐AKI. In adjusted models, neither kidney injury molecule‐1 nor interleukin‐18 improved discrimination for CA‐AKI; addition of osteopontin and cystatin C to the CA‐AKI clinical model significantly increased the c‐statistic from 0.69 to 0.73 (P for change <0.001) and resulted in a Net Reclassification Index of 59.4. Considering those with the lowest CA‐AKI integer score as a reference, the intermediate, high‐risk, and very‐high‐risk groups were associated with adverse cardiorenal outcomes. The corresponding hazard ratios of the very‐high‐risk group were 3.39 (95% CI, 2.14–5.38) for nonprocedural acute kidney injury, 5.58 (95% CI, 3.23–9.63) for incident chronic kidney disease, 6.21 (95% CI, 3.67–10.47) for myocardial infarction, and 8.94 (95% CI, 4.83–16.53) for all‐cause mortality.

Conclusions

A biomarker‐enhanced risk model significantly improves the prediction of CA‐AKI beyond clinical variables alone and may stratify the risk of future cardiorenal outcomes.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT00842868.

Early Biomarkers of Altered Renal Function and Orthostatic Intolerance During 10-day Bedrest

Exposure to actual or simulated microgravity results in alterations of renal function, fluid redistribution, and bone loss, which is coupled to a rise of urinary calcium excretion. We provided evidence that high calcium delivery to the collecting duct reduces local Aquaporin 2 (AQP2)-mediated water reabsorption under vasopressin action, thus limiting the maximal urinary concentration to reduce calcium saturation. To investigate early renal adaptation into simulated microgravity, we investigated the effects of 10 days of strict bedrest in 10 healthy volunteers. We report here that 10 days of inactivity are associated with a transient, significant decrease (day 5) in vasopressin (copeptin) paralleled by a decrease in AQP2 excretion, consistent with an increased central volume to the heart, resulting in reduced water reabsorption. Moreover, bedrest caused a significant increase in calciuria secondary to bone demineralization paralleled by a decrease in PTH. Urinary osteopontin, a glycoprotein exerting a protective effect on stone formation, was significantly reduced during bedrest. Moreover, a significant increase in adrenomedullin (day 5), a peptide with vasodepressor properties, was observed at day 5, which may contribute to the known reduced orthostatic capacity post-bedrest. We conclude that renal function is altered in simulated microgravity and is associated with an early increase in the risk of stone formation and reduced orthostatic capacity post-bedrest within a few days of inactivity.

Association of osteopontin with kidney function and kidney failure in chronic kidney disease patients: the GCKD study

BACKGROUND

Osteopontin (OPN), synthesized in the thick ascending limb of Henle's loop and in the distal tubule, is involved in the pathogenesis of kidney fibrosis, a hallmark of kidney failure (KF). In a cohort of chronic kidney disease (CKD) patients, we evaluated OPN's association with kidney markers and KF.

METHODS

OPN was measured from baseline serum samples of German Chronic Kidney Disease study participants. Cross-sectional regression models for estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (UACR) as well as Cox regression models for all-cause mortality and KF were evaluated to estimate the OPN effect. Additionally, predictive ability, of OPN and time-dependent population-attributable fraction were evaluated.

RESULTS

Over a median follow-up of 6.5 years, 471 KF events and 629 deaths occurred among 4,950 CKD patients. One-unit higher log(OPN) was associated with 5.5 mL/min/1.73m2 lower eGFR (95%CI: [-6.4,-4.6]) and 1% change in OPN with 0.7% higher UACR (estimated effect 0.7, 95%CI: [0.6,0.8]). Moreover, higher OPN levels were associated with a higher risk of KF (hazard ratio [HR] 1.4, 95%CI: [1.2,1.7]) and all-cause mortality (HR 1.5, 95%CI: [1.3,1.8]). After 6 years, 31% of the KF events could be attributed to higher OPN levels (95%CI: [3%,56%]).

CONCLUSIONS

In this study, higher OPN levels were associated with kidney function markers worsening, and a higher risk for adverse outcomes. A larger proportion of KF could be attributed to higher OPN levels warranting further research on OPN with regards to its role in CKD progression and possible treatment options.

Genetics of osteopontin in patients with chronic kidney disease: The German Chronic Kidney Disease study

Osteopontin (OPN), encoded by SPP1, is a phosphorylated glycoprotein predominantly synthesized in kidney tissue. Increased OPN mRNA and protein expression correlates with proteinuria, reduced creatinine clearance, and kidney fibrosis in animal models of kidney disease. But its genetic underpinnings are incompletely understood. We therefore conducted a genome-wide association study (GWAS) of OPN in a European chronic kidney disease (CKD) population. Using data from participants of the German Chronic Kidney Disease (GCKD) study (N = 4,897), a GWAS (minor allele frequency [MAF]≥1%) and aggregated variant testing (AVT, MAF<1%) of ELISA-quantified serum OPN, adjusted for age, sex, estimated glomerular filtration rate (eGFR), and urinary albumin-to-creatinine ratio (UACR) was conducted. In the project, GCKD participants had a mean age of 60 years (SD 12), median eGFR of 46 mL/min/1.73m2 (p25: 37, p75: 57) and median UACR of 50 mg/g (p25: 9, p75: 383). GWAS revealed 3 loci (p<5.0E-08), two of which replicated in the population-based Young Finns Study (YFS) cohort (p<1.67E-03): rs10011284, upstream of SPP1 encoding the OPN protein and related to OPN production, and rs4253311, mapping into KLKB1 encoding prekallikrein (PK), which is processed to kallikrein (KAL) implicated through the kinin-kallikrein system (KKS) in blood pressure control, inflammation, blood coagulation, cancer, and cardiovascular disease. The SPP1 gene was also identified by AVT (p = 2.5E-8), comprising 7 splice-site and missense variants. Among others, downstream analyses revealed colocalization of the OPN association signal at SPP1 with expression in pancreas tissue, and at KLKB1 with various plasma proteins in trans, and with phenotypes (bone disorder, deep venous thrombosis) in human tissue. In summary, this GWAS of OPN levels revealed two replicated associations. The KLKB1 locus connects the function of OPN with PK, suggestive of possible further post-translation processing of OPN. Further studies are needed to elucidate the complex role of OPN within human (patho)physiology.

Single-Nucleus Transcriptional Profiling of Chronic Kidney Disease after Cisplatin Nephrotoxicity

Cisplatin induces both acute and chronic nephrotoxicity during chemotherapy in patients with cancer. Presented here is the first study of single-nucleus RNA sequencing (snRNA-seq) of cisplatin-induced nephrotoxicity. Repeated low-dose cisplatin treatment (RLDC) led to decreases in renal function and kidney weight in mice at 9 weeks. The kidneys of these mice showed tubular degeneration and dilation. snRNA-seq identified 16 cell types and 17 cell clusters in these kidneys. Cluster-by-cluster comparison demonstrated cell type-specific changes in gene expression and identified a unique proximal tubule (PT) injury/repair cluster that co-expressed the injury marker kidney injury molecule-1 (Kim1) and the proliferation marker Ki-67. Compared with control, post-RLDC kidneys had 424 differentially expressed genes in PT cells, including tubular transporters and cytochrome P450 enzymes involved in lipid metabolism. snRNA-seq also revealed transcriptional changes in potential PT injury markers (Krt222, Eda2r, Ltbp2, and Masp1) and repair marker (Bex4). RLDC induced inflammation and proinflammatory cytokines (RelB, TNF-α, Il7, Ccl2, and Cxcl2) and the expression of fibrosis markers (fibronectin, collagen I, connective tissue growth factor, vimentin, and α-smooth muscle actin). Together, these results provide new insights into RLDC-induced transcriptional changes at the single-cell level that may contribute to the development of chronic kidney problems in patients with cancer after cisplatin chemotherapy.

β-catenin-controlled tubular cell-derived exosomes play a key role in fibroblast activation via the OPN-CD44 axis

Tubular injury and peripheral fibroblast activation are the hallmarks of chronic kidney disease (CKD), suggesting intimate communication between the two types of cells. However, the underlying mechanisms remain to be determined. Exosomes play a role in shuttling proteins and other materials to recipient cells. In our study, we found that exosomes were aroused by β‐catenin in renal tubular cells. Osteopontin (OPN), especially its N‐terminal fragment (N‐OPN), was encapsulated in β‐catenin‐controlled tubular cell‐derived exosome cargo, and subsequently passed to fibroblasts. Through binding with CD44, exosomal OPN promoted fibroblast proliferation and activation. Gene deletion of β‐catenin in tubular cells (Ksp‐β‐catenin^−/−) or gene ablation of CD44 (CD44^−/−) greatly ameliorated renal fibrosis. Notably, N‐OPN was carried by exosome and secreted into the urine of patients with CKD, and negatively correlated with kidney function. The urinary exosomes from patients with CKD greatly accelerated renal fibrosis, which was blocked by CD44 deletion. These results suggest that exosome‐mediated activation of the OPN/CD44 axis plays a key role in renal fibrosis, which is controlled by β‐catenin.

Identification of the pivotal role of SPP1 in kidney stone disease based on multiple bioinformatics analysis

Background

Kidney stone disease (KSD) is a multifactorial disease involving both environmental and genetic factors, whose pathogenesis remains unclear. This study aims to explore the hub genes related to stone formation that could serve as potential therapeutic targets.

Methods

Based on the GSE73680 dataset with 62 samples, differentially expressed genes (DEGs) between Randall’s plaque (RP) tissues and normal tissues were screened and weighted gene co-expression network analysis (WGCNA) was applied to identify key modules associated with KSD. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were performed to explore the biological functions. The protein–protein interaction (PPI) network was constructed to identify hub genes. Meanwhile, CIBERSORT and ssGSEA analysis were used to estimate the infiltration level of the immune cells. The correlations between hub genes and immune infiltration levels were also investigated. Finally, the top hub gene was selected for further GSEA analysis.

Results

A total of 116 DEGs, including 73 up-regulated and 43 down-regulated genes, were screened in the dataset. The red module was identified as the key module correlated with KSD. 53 genes were obtained for functional enrichment analysis by taking the intersection of DEGs and genes in the red module. GO analysis showed that these genes were mainly involved in extracellular matrix organization (ECM) and extracellular structure organization, and others. KEGG analysis revealed that the pathways of aldosterone-regulated sodium reabsorption, cell adhesion molecules, arachidonic acid (AA) metabolism, and ECM-receptor interaction were enriched. Through PPI network construction, 30 hub genes were identified. CIBERSORT analysis revealed a significantly increased proportion of M0 macrophages, while ssGSEA revealed no significant differences. Among these hub genes, SPP1, LCN2, MMP7, MUC1, SCNN1A, CLU, SLP1, LAMC2, and CYSLTR2 were positively correlated with macrophages infiltration. GSEA analysis found that positive regulation of JNK activity was enriched in RP tissues with high SPP1 expression, while negative regulation of IL-1β production was enriched in the low-SPP1 subgroup.

Conclusions

There are 30 hub genes associated with KSD, among which SPP1 is the top hub gene with the most extensive links with other hub genes. SPP1 might play a pivotal role in the pathogenesis of KSD, which is expected to become a potential therapeutic target, while its interaction with macrophages in KSD needs further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01157-4.

Secreted protein acidic and rich in cysteine (SPARC) and a disintegrin and metalloproteinase with thrombospondin type 1 motif (ADAMTS1) increments by the renin-angiotensin system induce renal fibrosis in deoxycorticosterone acetate-salt hypertensive rats

Secreted protein acidic and rich in cysteine (SPARC), an extracellular matrix (ECM) protein, was recently shown to induce collagen deposition through the production of a disintegrin and metalloproteinase with thrombospondin type 1 motif (ADAMTS1) in the aging heart. ADAMTS1 regulates ECM turnover by degrading ECM components, and its excessive activation contributes to various pathological states, including fibrosis. The present study investigated the pathophysiological regulation and role of SPARC and ADAMTS1 in renal fibrosis using uninephrectomized rats treated with deoxycorticosterone acetate (DOCA, 40 mg/kg/week, subcutaneously) and salt (1% in drinking water). The administration of DOCA and salt gradually and significantly elevated systolic blood pressure during the 3-week treatment period, induced proteinuria, decreased creatinine clearance, and increased NADPH oxidase-derived superoxide production, malondialdehyde concentrations, and monocyte chemoattractant protein-1 and osteopontin expression in the kidneys. Glomerulosclerosis, fibrillar collagen deposition, and transforming growth factor-β expression increased in a time-dependent manner, and SPARC and ADAMTS1 expression showed a similar pattern to these changes. The angiotensin II type-1 receptor blocker losartan suppressed the overexpression of SPARC and ADAMTS1, and an in vitro exposure to angiotensin II induced the production of both SPARC and ADAMTS1 in renal fibroblast NRK-49F cells. Knockdown of the SPARC gene with small interfering RNA reduced all forms (the 110-kDa latent and 87- and 65-kDa bioactive forms) of ADAMTS1 expression as well as collagen production. These results suggest that SPARC is induced by the renin-angiotensin system and may be a fibrogenic factor, at least in part, by producing ADAMTS1 in hypertensive renal disease.

Physiological Changes and Pathological Pain Associated with Sedentary Lifestyle-Induced Body Systems Fat Accumulation and Their Modulation by Physical Exercise

A sedentary lifestyle is associated with overweight/obesity, which involves excessive fat body accumulation, triggering structural and functional changes in tissues, organs, and body systems. Research shows that this fat accumulation is responsible for several comorbidities, including cardiovascular, gastrointestinal, and metabolic dysfunctions, as well as pathological pain behaviors. These health concerns are related to the crosstalk between adipose tissue and body systems, leading to pathophysiological changes to the latter. To deal with these health issues, it has been suggested that physical exercise may reverse part of these obesity-related pathologies by modulating the cross talk between the adipose tissue and body systems. In this context, this review was carried out to provide knowledge about (i) the structural and functional changes in tissues, organs, and body systems from accumulation of fat in obesity, emphasizing the crosstalk between fat and body tissues; (ii) the crosstalk between fat and body tissues triggering pain; and (iii) the effects of physical exercise on body tissues and organs in obese and non-obese subjects, and their impact on pathological pain. This information may help one to better understand this crosstalk and the factors involved, and it could be useful in designing more specific training interventions (according to the nature of the comorbidity).

Endocrine Regulation of Extra-skeletal Organs by Bone-derived Secreted Protein and the effect of Mechanical Stimulation

Bone serves as the support for body and provide attachment points for the muscles. The musculoskeletal system is the basis for the human body to complete exercise. Studies believe that bone is not only the basis for constructing structures, but also participates in the regulation of organs outside bone. The realization of this function is closely related to the protein secreted by bone. Whether bone can realize their positions in the human body is also related to their secretion. Bone-derived proteins provide a medium for the targeted regulation of bones on organs, making the role of bone in human body more profound and concrete. Mechanical stimulation effects the extra-skeletal organs by causing quantitative changes in bone-derived factors. When bone receives mechanical stimulation, the nichle of bone responds, and the secretion of various factors changes. However, whether the proteins secreted by bone can interfere with disease requires more research. In this review article, we will first introduce the important reasons and significance of the in-depth study on bone-derived secretory proteins, and summarize the locations, structures and functions of these proteins. These functions will not only focus on the bone metabolism process, but also be reflected in the cross-organ regulation. We specifically explain the role of typical bone-derived secretory factors such as osteocalcin (OCN), osteopontin (OPN), sclerostin (SOST) and fibroblast growth factor 23 (FGF23) in different organs and metabolic processes, then establishing the relationship between them and diseases. Finally, we will discuss whether exercise or mechanical stimulation can have a definite effect on bone-derived secretory factors. Understanding their important role in cross-organ regulation is of great significance for the treatment of diseases, especially for the elderly people with more than one basic disease.

Diagnostic Value of Multiple Serum Biomarkers for Vancomycin-Induced Kidney Injury

Acute kidney injury (AKI) is a major contributor to in-hospital morbidity and mortality. Vancomycin, one of the most commonly used antibiotics in a clinical setting, is associated with AKI, with its incidence ranging up to 43%. Despite the high demand, few studies have investigated serum biomarkers to detect vancomycin-induced kidney injury (VIKI). Here, we evaluated the diagnostic value of nine candidate serum biomarkers for VIKI. A total of 23,182 cases referred for vancomycin concentration measurement from January 2018 to December 2019 were screened and 28 subjects with confirmed VIKI were enrolled (VIKI group). Age- and sex- matched control group consisted of 21 subjects who underwent vancomycin therapy without developing VIKI (non-VIKI group), and 23 healthy controls (HC group). The serum concentrations of clusterin, retinol binding protein 4 (RBP4), interleukin-18 (IL-18), tumor necrosis factor receptor 1 (TNF-R1), C-X-C motif chemokine ligand 10 (CXCL10), neutrophil gelatinase-associated lipocalin (NGAL), osteopontin, trefoil factor-3 (TFF3), and cystatin C were compared among the three groups, and their correlations with estimated glomerular filtration rate (eGFR) and diagnostic values for VIKI were assessed. All of the biomarkers except clusterin and RBP4 exhibited significant elevation in the VIKI group. Serum TFF3, cystatin C, TNF-R1, and osteopontin demonstrated an excellent diagnostic value for VIKI (TFF3, area under the curve (AUC) 0.932; cystatin C, AUC 0.917; TNF-R1, AUC 0.866; osteopontin, AUC 0.787); and except osteopontin, a strong negative correlation with eGFR (TFF3, r = −0.71; cystatin C, r = −0.70; TNF-R1, r = −0.60). IL-18, CXCL10, and NGAL showed weak correlation with eGFR and moderate diagnostic value for VIKI. This study tested multiple serum biomarkers for VIKI and showed that serum TFF3, cystatin C, TNF-R1, and osteopontin could efficiently discriminate VIKI patients. Further studies are warranted to clarify the diagnostic value of these biomarkers in VIKI.

T Cell Immunosenescence in Aging, Obesity, and Cardiovascular Disease

Although advances in preventive medicine have greatly improved prognosis, cardiovascular disease (CVD) remains the leading cause of death worldwide. This clearly indicates that there remain residual cardiovascular risks that have not been targeted by conventional therapies. The results of multiple animal studies and clinical trials clearly indicate that inflammation is the most important residual risk and a potential target for CVD prevention. The immune cell network is intricately regulated to maintain homeostasis. Ageing associated changes to the immune system occurs in both innate and adaptive immune cells, however T cells are most susceptible to this process. T-cell changes due to thymic degeneration and homeostatic proliferation, metabolic abnormalities, telomere length shortening, and epigenetic changes associated with aging and obesity may not only reduce normal immune function, but also induce inflammatory tendencies, a process referred to as immunosenescence. Since the disruption of biological homeostasis by T cell immunosenescence is closely related to the development and progression of CVD via inflammation, senescent T cells are attracting attention as a new therapeutic target. In this review, we discuss the relationship between CVD and T cell immunosenescence associated with aging and obesity.

Hydroxycitrate prevents calcium oxalate crystallization and kidney injury in a nephrolithiasis rat model

Hydroxycitrate (HCA) is a derivative of citric acid, and previous studies of HCA have revealed its ability to inhibit the formation of calcium oxalate crystals in vitro. To date, there has been little evidence proving that HCA has the same effectiveness in vivo. The present study was designed to investigate the ameliorating effect of HCA on calcium oxalate deposition and renal impairment in a male rat model. Male Sprague-Dawley rats were randomly divided into four groups: a control group, a model group (glyoxalic acid), a CA group (glyoxalic acid + CA), and an HCA group (glyoxalic acid + HCA). Kidney stone formation was induced by injection of glyoxalic acid (60 mg/kg). The results showed that serum and urinary parameters were significantly improved by HCA treatment. In addition, differences in the formation of calcium oxalate crystals between groups were observed, and HCA was superior to CA in inhibiting crystal accumulation. The ultrastructure of renal tubules and glomeruli occurred in the model group, and the above lesions were significantly reduced in the HCA group. Both OPN and SOD expression levels were promoted by HCA, while CA only promoted OPN. In this article, we provided data on whether HCA affected kidney stones and the expression levels of OPN and SOD in a male rat model.

Osteopontin in Cardiovascular Diseases

Unprecedented advances in secondary prevention have greatly improved the prognosis of cardiovascular diseases (CVDs); however, CVDs remain a leading cause of death globally. These findings suggest the need to reconsider cardiovascular risk and optimal medical therapy. Numerous studies have shown that inflammation, pro-thrombotic factors, and gene mutations are focused not only on cardiovascular residual risk but also as the next therapeutic target for CVDs. Furthermore, recent clinical trials, such as the Canakinumab Anti-inflammatory Thrombosis Outcomes Study trial, showed the possibility of anti-inflammatory therapy for patients with CVDs. Osteopontin (OPN) is a matricellular protein that mediates diverse biological functions and is involved in a number of pathological states in CVDs. OPN has a two-faced phenotype that is dependent on the pathological state. Acute increases in OPN have protective roles, including wound healing, neovascularization, and amelioration of vascular calcification. By contrast, chronic increases in OPN predict poor prognosis of a major adverse cardiovascular event independent of conventional cardiovascular risk factors. Thus, OPN can be a therapeutic target for CVDs but is not clinically available. In this review, we discuss the role of OPN in the development of CVDs and its potential as a therapeutic target.

miR-195-5p Regulates the Phenotype Switch of CCSM Cells by Targeting Smad7

INTRODUCTION

Phenotype switch refers to the process in which smooth muscle cells change from contractile type to synthetic type and acquire the ability of proliferation. Phenotypic transformation involves many changes of cell function, such as collagen deposition and fibrosis, which affect the normal erectile function of penis.

AIM

To investigate the role of miR-195-5p in regulating the Phenotype switch of the corpus cavernosum smooth muscle (CCSM) cells.

METHODS

A small mother against decapentaplegic 7(Smad7) virus vector and a miR-195-5p mimics or an si-Smad7 viral vector and a miR-195-5p inhibitor were transfected into CCSM cells. The cells were obtained by primary culture of rat corpus cavernosum smooth muscle tissue. Real-time polymerase chain reaction (PCR) experiments, Western blotting, hematoxylin-eosin (HE) staining, transwell experiments, MTT assays, and flow cytometry were used to detect miR-195-5p, Smad7, phenotype switch markers of CCSM cells and related protein expression, as well as changes in cell morphology, migration, proliferation and apoptosis.

MAIN OUTCOME MEASURE

To study the regulation of miR-195-5p in CCSM cells by overexpression and silencing strategies.

RESULTS

Overexpressed miR-195-5p promoted the transformation of CCSM cells from a contractile type to a synthetic type. Meanwhile, the migration ability and proliferation ability of CCSM cells increased, and the apoptosis rate decreased. The expression-silencing of miR-195-5p gave rise to the opposite effect. The results of the rescue experiment demonstrated that overexpressed Smad7 rescued the inhibitory of the switch of the CCSM cell phenotype from the contractile type to the synthesis type caused by overexpression of miR-195-5p alone. Moreover, the enhancement effect of the migration ability and proliferation ability of CCSM cells was also eliminated, and the apoptosis rate was increased. Silencing miR-195-5p and Smad7 at the same time resulted in the opposite effect.

CONCLUSION

miR-195-5p may regulate the phenotype switch of CCSM cells by targeting Smad7. Zhang J, Zhang X, Zhang J, et al. miR-195-5p Regulates the Phenotype Switch of CCSM Cells by Targeting Smad7. Sex Med 2021;9:100349.