Pathogenesis Of Stones Research Articles

Roles for Exosome in Various Kidney Diseases and Disorders.

Exosome is a nanoscale vesicle with a size range of 30–100 nm. It is secreted from cell to extracellular space by exocytosis after fusion of multivesicular body (MVB) (formed by endocytic vesicles) with plasma membrane. Exosome plays several important roles in cellular homeostasis and intercellular communications. During the last two decades, exosome has acquired a wide attention to explore its additional roles in various aspects of cell biology and function in several organ systems. For the kidney, several lines of evidence have demonstrated 1that exosome is involved in the renal physiology and pathogenic mechanisms of various kidney diseases/disorders. This article summarizes roles of the exosome as the potential source of biomarkers, pathogenic molecules, and therapeutic biologics that have been extensively investigated in many kidney diseases/disorders, including lupus nephritis (LN), other glomerular diseases, acute kidney injury (AKI), diabetic nephropathy (DN), as well as in the process of renal fibrosis and chronic kidney disease (CKD) progression, in addition to polycystic kidney disease (PKD), kidney transplantation, and renal cell carcinoma (RCC). Moreover, the most recent evidence has shown its emerging role in kidney stone disease (or nephrolithiasis), involving inflammasome activation and inflammatory cascade frequently found in kidney stone pathogenesis.

Urethral Stone: A Rare Cause of Acute Retention of Urine in Men

Urethral stones are a very rare form of urolithiasis, they most often originate from the upper urinary tract or bladder, and are rarely formed primarily in the urethra, it is formed on a urethral anatomical pathology in the majority of cases. The clinical symptomatology is very variable ranging from simple dysuria with penile pain to acute retention of urine. Smaller stones can be expelled spontaneously without intervention, but larger stones or complicated stones or those developed on an underlying urethral anatomical pathology require surgical treatment. The minimally invasive treatment should be the preferred route for the surgical treatment of this disease when feasible. We report the case of a young man with no particular pathological history who presented to the emergency department for acute retention of urine secondary to a primary fossa navicularis calculus, through this case, we discuss the different clinical aspects, etiology, pathogenesis, diagnosis and therapy of urethral stone in men.

Renal Papillary Mapping and Quantification of Randall's Plaque in Pediatric Calcium Oxalate Stone Formers.

Introduction: Randall's plaque (RP) with attached stones is recognized as a primary mechanism for stone formation in adult calcium oxalate stone formers (CaOx SFs). The role of RP in pediatric stone pathogenesis is unknown, with no reported studies to date. The purpose of this study is to investigate renal papillary abnormalities and quantify RP in pediatric CaOx SFs. Methods: Eight pediatric CaOx SFs underwent ureteroscopy for symptomatic urolithiasis. The collecting system was mapped using a digital ureteroscope. Video for each patient was then reviewed using a retrograde pyelogram to confirm the location of each papilla. A single investigator (N.L.M.) reviewed the video to quantify RP. Each papilla was graded as having mild, moderate, or severe amount of RP. Patient history was recorded. Results: An average of nine papillae were mapped per patient. RP was present in 100% of patients and in 88.8% (64/72) of all papillae examined. When present, RP was uniformly distributed throughout the kidney without preferential distribution to a region or pole. The amount of RP on the papillae was graded as mild in 60%, moderate in 20.8%, and severe in 8.3%. The mean fractional RP coverage ranged from 0.39% to 9.34%. No correlation was found between the amount of plaque and age at first stone episode or number of prior stone episodes (p = 0.84). Attached stones were rare (1/8 patients). The two patients with severe RP had a small amount of calcium phosphate in their stone analysis. Conclusions: RP is common in pediatric CaOx SFs. Compared with adult CaOx SFs wherein up to 75% of stones are found attached to RP, attached stones were rare. The significance of these findings in the pathogenesis of pediatric stone formation remains unclear and will require longer term follow-up.

Urinary extracellular vesicle-associated MCP-1 and NGAL derived from specific nephron segments differ between calcium oxalate stone formers and controls.

Randall's plaque (RP; subepithelial calcification) appears to be an important precursor of kidney stone disease. However, RP cannot be noninvasively detected. The present study investigated candidate biomarkers associated with extracellular vesicles (EVs) in the urine of calcium stone formers (CSFs) with low (<5% papillary surface area) and high (≥5% papillary surface area) percentages of RP and a group of nonstone formers. RPs were quantitated via videotaping and image processing in consecutive CSFs undergoing percutaneous surgery for stone removal. Urinary EVs derived from cells of different nephron segments of CSFs (n = 64) and nonstone formers (n = 40) were quantified in biobanked cell-free urine by standardized and validated digital flow cytometer using fluorophore-conjugated antibodies. Overall, the number of EVs carrying surface monocyte chemoattractant protein (MCP)-1 and neutrophil gelatinase-associated lipocalin (NGAL) were significantly lower in CSFs compared with nonstone former controls (P < 0.05) but did not differ statistically between CSFs with low and high RPs. The number of EVs associated with osteopontin did not differ between any groups. Thus, EVs carrying MCP-1 and NGAL may directly or indirectly contribute to stone pathogenesis as evidenced by the lower of these populations of EVs in stone formers compared with nonstone formers. Validation of EV-associated MCP-1 and NGAL as noninvasive biomarkers of kidney stone pathogenesis in larger populations is warranted.

Current concepts on the pathogenesis of urinary stones

The process of kidney stone formation is complex and still not completely understood. Supersaturation and crystallization are the main drivers for the etiopathogenesis of uric acid, xanthine and cystine stones but this physicochemical concept fails to adequately explain the formation of calcium-based nephrolithiasis, which represents the majority of kidney stones. Contemporary concepts of the pathogenesis of calcium-based nephrolithiasis focus on a nidus-associated stone formation of calcium-based nephrolithiasis on Randall's plaques or on plugs of Bellini's duct. Randall's plaques originate from the interaction of interstitial calcium supersaturation in the renal papilla, vascular and interstitial inflammatory processes and mineral deposits of calcifying nanoparticles on the basal membrane of the thin ascending branch of the loop of Henle; however, plugs of Bellini's duct are assumed to be caused by mineral deposits on the wall of the collecting ducts. Aggregation and overgrowth are influenced by the interaction of matrix proteins with calcium supersaturated urine, by an imbalance between promoters and inhibitors of stone formation in the calyceal urine. Current research has elucidated many factors contributing to stone formation by revealing novel insights into the physiology of nephron and papilla, by analyzing vascular, inflammatory and calcifying processes in the renal medulla, by examining the proteome, the microbiome, promoters and inhibitors of stone formation in the urine and by conducting the first genome-wide association studies; however, more future research is mandatory to fill the gap of knowledge and hopefully, to obtain novel prophylactic, therapeutic and metaphylactic tools beyond the current state of knowledge.

Effect of dimethyl fumarate on the renal calcium oxalate stone formation in rats and possible mechanism

Objective To observe the effect of dimethyl fumarate (DMF) on the renal calcium oxalate crystals formation in SD rats induced by glyoxylic acid monohydrate, and explore the possible mechanism. Methods Thirty male Sprague-Dawley rats were randomly divided into 3 groups: control group, model group and DMF group (n=10 each). The control group was free to drink purified water. Model group was induced by intraperitoneal injection of glyoxylic acid monohydrate to establish a kidney calcium oxalate stone model, and DMF group was treat with DMF by gastric administration on the basis of modeling. After 10 days of continuous treatment, the 24 h urine, serum and kidney of rats in each group were collected. Serum creatinine (SCr) value, calcium and oxalate (Ox) contents in urine were measured. Von Kossa staining method was used to detect the deposition of calcium oxalate crystals in kidney tissue. Western blotting was used to detect the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and HO-1 protein in renal tissue. The frozen section DHE staining was used to detect the ROS level in the kidney, thiobarbituric acid method was used to test malondialdehyde (MDA) content, and the xanthine oxidase method was used to detect superoxide dismutase (SOD) activity. Results There was no visible calcium crystal in the kidney of the control group. Compared to the model group, the amounts of renal calcium crystal were significantly reduced in the DMF group (76.07±4.87) /HP vs. (37.94±4.63) /HP (t=17.940, P 0.05). There was no significant difference in 24-hour urinary calcium ion content between the three groups (F=1.670, P>0.05). Compared with the control group, renal ROS levels (t=20.920, P<0.01), Nrf2 (t=17.290, P<0.01) and HO-1 protein (t=38.030, P<0.01) expression levels were significantly increased in the model group. Compared with the model group, renal ROS levels were significantly reduced in the DMF group (t=16.000, P<0.01), while the expression levels of Nrf2 (t=25.580, P<0.01) and HO-1 protein (t=79.290, P<0.01) were significantly increased. Conclusion The formation of calcium oxalate kidney stones is related to oxalate-mediated oxidative stress. DMF may interfere with the pathogenesis of calcium oxalate kidney stones by activating Nrf2 to induce HO-1 to inhibit oxidative stress. Key words: Calcium oxalate stones; Oxidative stress; Nuclear factor erythroid 2-related factor 2; Dimethyl fumarate

PD38-04 NEUTROPHIL INFILTRATION AND NETOSIS IN THE PATHOGENESIS OF HUMAN KIDNEY BRUSHITE STONES

INTRODUCTION AND OBJECTIVES:The pathogenesis of kidney stones in humans is poorly understood. There are multiple types of kidney stones, and the role of inflammation in promoting specific stone typ...

Modulatory effects of fibronectin on calcium oxalate crystallization, growth, aggregation, adhesion on renal tubular cells, and invasion through extracellular matrix

Fibronectin, an extracellular matrix (ECM) protein, has been thought to be involved in pathogenic mechanisms of kidney stone disease, especially calcium oxalate (CaOx) type. Nevertheless, its precise roles in modulation of CaOx crystal remained unclear. We thus performed a systematic evaluation of effects of fibronectin on CaOx monohydrate (COM) crystal (the major causative chemical crystal in kidney stone formation) in various stages of kidney stone pathogenesis, including crystallization, crystal growth, aggregation, adhesion onto renal tubular cells, and invasion through ECM in renal interstitium. The data showed that fibronectin significantly decreased crystallization, growth and adhesive capability of COM crystals in a dose‐dependent manner. In contrast, COM crystal aggregation and invasion through ECM migration chamber were significantly enhanced by fibronectin in a dose‐dependent fashion. Sequence analysis revealed two and six calcium‐binding and oxalate‐binding domains, respectively. Saturation of fibronectin with oxalate prior to crystal modulation assays could abolish all the effects of fibronectin, whereas saturation with calcium had minimal interference. These data strongly indicate the dual functions of fibronectin, which serves as an inhibitor for COM crystallization, crystal growth and adhesion onto renal tubular cells, but on the other hand, acts as a promoter for COM crystal aggregation and invasion through ECM. Moreover, its crystal modulatory activities are mainly due to oxalate‐binding capability.Support or Funding InformationThis study was supported by Mahidol University research grant and the Thailand Research Fund (IRN60W0004 and IRG5980006).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Looking back on 50 years of stone treatment

Urolithiasis is an urologist's daily business. This article provides an overview of the developments in the management of urinary stone disease since the 1970s. While conventional KUB X-rays and intravenous pyelography were standard imaging procedures in the past, computed tomography is the first choice today. Conservative treatments such as medical expulsive therapy were established to facilitate ureteral stone passage, but have come into discussion in the past few years. Fifty years ago, open stone surgery was the standard procedure to access renal stones. This has been superseded by minimally-invasive procedures ranging from percutaneous nephrolithotomy (PCNL) to extracorporeal shock-wave lithotripsy (ESWL) and ureteroscopy (URS), which is today's standard for most upper urinary tract stones. It would have been desirable if such enormous efforts and progress had been made in the evaluation of stone pathogenesis and the improvement of preventative measures. Unfortunately, the knowledge on stone formation has hardly improved compared to 1970.

Modulatory effects of fibronectin on calcium oxalate crystallization, growth, aggregation, adhesion on renal tubular cells, and invasion through extracellular matrix.

Fibronectin, an extracellular matrix (ECM) protein, has been thought to be involved in pathogenic mechanisms of kidney stone disease, especially calcium oxalate (CaOx) type. Nevertheless, its precise roles in modulation of CaOx crystal remained unclear. We thus performed a systematic evaluation of effects of fibronectin on CaOx monohydrate (COM) crystal (the major causative chemical crystal in kidney stone formation) in various stages of kidney stone pathogenesis, including crystallization, crystal growth, aggregation, adhesion onto renal tubular cells, and invasion through ECM in renal interstitium. The data showed that fibronectin significantly decreased crystallization, growth and adhesive capability of COM crystals in a dose-dependent manner. In contrast, COM crystal aggregation and invasion through ECM migration chamber were significantly enhanced by fibronectin in a dose-dependent fashion. Sequence analysis revealed three calcium-binding and six oxalate-binding domains in fibronectin. Immunofluorescence study confirmed binding of fibronectin to COM crystals. Additionally, calcium- and oxalate-affinity assays confirmed depletion of both calcium and oxalate ions after incubation with fibronectin. Moreover, calcium-saturated and oxalate-saturated forms of fibronectin markedly reduced the modulatory activities of fibronectin on COM crystallization, crystal growth, aggregation, and adhesion onto the cells. These data strongly indicate the dual functions of fibronectin, which serves as an inhibitor for COM crystallization, crystal growth and adhesion onto renal tubular cells, but on the other hand, acts as a promoter for COM crystal aggregation and invasion through ECM. Finally, its COM crystal modulatory activities are most likely mediated through binding with calcium and oxalate ions on the crystals and in their environment.

Correction to: Testing the dogma that total phospholipid fatty acid composition of blood plays a role in kidney stone pathogenesis, using a high-low risk human model: results from a pilot study.

The authors would like to add the following paragraph in the acknowledgement section of the original version of the paper.

Heritable traits that contribute to nephrolithiasis.

Urinary stones tend to cluster in families. Of the known risk factors, evidence is strongest for heritability of urinary calcium excretion. Recent studies suggest that other stone risk factors may have heritable components including urinary pH, citrate and magnesium excretion, and circulating vitamin D concentration. Several risk factors assumed purely environmental may also have heritable components, including dietary intake and thirst. Thus, future studies may reveal that genetics plays an even stronger role in urinary stone pathogenesis than previously known.

Changing expression profiles of long non-coding RNAs, mRNAs and circular RNAs in ethylene glycol-induced kidney calculi rats

BackgroundTo explore long non-coding RNA (lncRNA), mRNA and circular RNA (circRNA) expression profiles and their biological functions in the pathogenesis of kidney stones in ethylene glycol-induced urolithiasis rats.ResultsThe expression of 1440 lncRNAs, 2455 mRNAs and 145 circRNAs was altered in the kidneys of urolithiasis rats. GO and KEGG biological pathway analysis were performed to predict the functions of differentially expressed lncRNAs, circRNAs and co-expressed potential targeting genes. Co-expression networks of lncRNA-mRNA and circRNA-miRNA were constructed based on correlation analysis between differentially expressed RNAs. mRNAs coexpressed with lncRNAs were involved in many kidney diseases, e.g., Ephb6 was associated with the reabsorption ability of the kidney. Arl5b was associated with the dynamic changes in the podocyte foot process in podocyte injury. miRNAs co-expressed with circRNAs, such as rno-miR-138-5p and rno-miR-672-5p, have been proven to be functional in hypercalciuria urolithiasis.ConclusionThe expression profile provided a systematic perspective on the potential functions of lncRNAs and circRNAs in the pathogenesis of kidney stones. Differentially expressed lncRNAs and circRNAs might serve as treatment targets for kidney stones.

Caffeine in Kidney Stone Disease: Risk or Benefit?

Kidney stone disease is a global health care problem, with a high recurrence rate after stone removal. It is thus crucial to develop effective strategies to prevent the formation of new or recurrent stones. Caffeine is one of the main components in caffeinated beverages worldwide (i.e., coffee, tea, soft drinks, and energy drinks). Previous retrospective and prospective studies have reported contradictory effects of caffeine on kidney stone risk. Although it has a diuretic effect on enhancing urinary output, it may slightly increase the stone risk index. However, 3 large cohorts have suggested a preventive role of caffeine in kidney stone disease. In addition, a recent in vitro study has addressed relevant mechanisms underlying the preventive role of caffeine against stone pathogenesis. This review summarizes the relevant data from previous evidence and discusses the association between caffeine consumption and kidney stone risk reduction.

Testing the dogma that total phospholipid fatty acid composition of blood plays a role in kidney stone pathogenesis, using a high-low risk human model: results from a pilot study.

Previous studies have suggested that ω-3 and ω-6 polyunsaturated fatty acid (PUFA) composition in plasma and red blood cell (RBC) total phospholipids plays a role in urolithiasis. Our aim was to test the robustness of this dogma by retrospectively comparing baseline profiles of these parameters in subjects from high- and low-stone-risk groups. The documented difference in stone occurrence in white (relatively common) (W) and black (rare) (B) subjects prompted us to select these groups as the high-low risk model for the study. Blood and urine samples were obtained from ten subjects in each group and were analysed for PUFAs and stone risk factors, respectively. Concentrations of linoleic acid (LA), eicosadienoic acid (EDA) and arachidonic acid (AA) in plasma and or/RBC total phospholipids were significantly higher in B. Differences in other PUFA profiles were also observed. There was no inter-group difference in AA/LA ratios. Urinary oxalate was significantly higher while urinary phosphate was significantly lower in B. We speculate that elevated AA in B might arise because of a possibly enhanced elongation of LA to EDA, as well as an enhanced ∆-8-desaturation of EDA to dihomo-gamma-linolenic acid (DGLA), which is the immediate precursor of AA. Alternatively, we speculate that the ∆-5-desaturation step of DGLA to AA might be more highly activated in this group. Irrespective of the mechanism, our observed inter-group differences in phospholipid PUFA composition are in conflict with previously published dogma which relates PUFA characteristics to high- and low-stone risk.

Protein Network Analysis and Functional Studies of Calcium Oxalate Crystal-Induced Cytotoxicity in Renal Tubular Epithelial Cells.

Our previous expression study has reported a set of proteins with altered levels in renal tubular cells after exposure to calcium oxalate monohydrate (COM) crystals, which are the main composition of kidney stones. However, their functional significance remained largely unknown. In this study, protein network analysis revealed that the significantly altered proteins induced by COM crystals were involved mainly in three main functional networks, including i) cell proliferation and wound healing; ii) oxidative stress and mitochondrial function; and iii) cellular junction complex and integrity. Cell proliferation and wound healing assays showed that the COM-treated cells had defective proliferation and tissue healing capability, respectively. Oxyblot analysis demonstrated accumulation of the oxidized proteins, whereas intracellular ATP level was significantly increased in the COM-treated cells. Additionally, level of zonula occludens-1 (ZO-1), a tight junction protein, was significantly decreased, consistent with the significant declines in transepithelial resistance (TER) and level of RhoA signaling molecule in the COM-treated cells. These findings indicate significant perturbations in mitochondrial and oxidative stress axis that cause defective cell proliferation, tissue healing capability, junctional protein complex, and cellular integrity of renal tubular epithelial cells exposed to COM crystals that may play important roles in kidney stone pathogenesis.

Roles of Macrophage Exosomes in Immune Response to Calcium Oxalate Monohydrate Crystals.

In kidney stone disease, macrophages secrete various mediators via classical secretory pathway and cause renal interstitial inflammation. However, whether their extracellular vesicles, particularly exosomes, are involved in kidney stone pathogenesis remained unknown. This study investigated alterations in exosomal proteome of U937-derived macrophages (by phorbol-12-myristate-13-acetate activation) after exposure to calcium oxalate monohydrate (COM) crystals for 16-h using 2-DE-based proteomics approach. Six significantly altered proteins in COM-treated exosomes were successfully identified by nanoscale liquid chromatography–electrospray ionization–electron transfer dissociation tandem mass spectrometry as proteins involved mainly in immune processes, including T-cell activation and homeostasis, Fcγ receptor-mediated phagocytosis, interferon-γ (IFN-γ) regulation, and cell migration/movement. The decreased heat shock protein 90-beta (HSP90β) and increased vimentin were confirmed by Western blotting. ELISA showed that the COM-treated macrophages produced greater level of interleukin-1β (IL-1β), one of the markers for inflammasome activation. Functional studies demonstrated that COM-treated exosomes enhanced monocyte and T-cell migration, monocyte activation and macrophage phagocytic activity, but on the other hand, reduced T-cell activation. In addition, COM-treated exosomes enhanced production of proinflammatory cytokine IL-8 by monocytes that could be restored to its basal level by small-interfering RNA targeting on vimentin (si-Vimentin). Moreover, si-Vimentin could also abolish effects of COM-treated exosomes on monocyte and T-cell migration as well as macrophage phagocytic activity. These findings provided some implications to the immune response during kidney stone pathogenesis via exosomal pathway of macrophages after exposure to COM crystals.

Hyperuricosuric calcium urolithiasis.

Hyperuricosuric calcium urolithiasis is a condition of mixed calcium oxalate stones characterized by hyperuricosuria either in isolation or in conjunction with other risk factors for calcium oxalate stones such as hypercalciuria, hyperoxaluria, and hypocitraturia. There are three proposed physicochemical models of pathogenesis where urate in its crystalline phase via heterogeneous nucleation, in its colloidal phase via removal of crystallization inhibitors, and in solution via precipitation crystallization, can all increase propensity to calcium oxalate precipitation. Regardless of the model, the phenomenologic observation of urate increasing calcium oxalate precipitation appears solid. Another supporting factor are retrospective data analysis and prospective trials showing uric acid lowering reduces stones events in hyperuricosuric calcium stone formers. Due to the heterogeneity of pathogenesis of calcium oxalate stones in the unselected stone-formers, association cannot be demonstrated between uric acid excretion rate and risk of kidney stone the general population. In calcium oxalate stoners with isolated hyperuricosuria or hyperuricosuria in combination with other calcium stone risks where treatment of these traditional risks fails to reduce stone formation, urate acid lowering should be cautiously attempted. More refinement of pathogenic models and prospective controlled trials in phenotypically defined subgroups of subjects with calcium oxalate urolithiasis will be informative.

Kidney Stone Disease: An Update on Current Concepts.

Kidney stone disease is a crystal concretion formed usually within the kidneys. It is an increasing urological disorder of human health, affecting about 12% of the world population. It has been associated with an increased risk of end-stage renal failure. The etiology of kidney stone is multifactorial. The most common type of kidney stone is calcium oxalate formed at Randall's plaque on the renal papillary surfaces. The mechanism of stone formation is a complex process which results from several physicochemical events including supersaturation, nucleation, growth, aggregation, and retention of urinary stone constituents within tubular cells. These steps are modulated by an imbalance between factors that promote or inhibit urinary crystallization. It is also noted that cellular injury promotes retention of particles on renal papillary surfaces. The exposure of renal epithelial cells to oxalate causes a signaling cascade which leads to apoptosis by p38 mitogen-activated protein kinase pathways. Currently, there is no satisfactory drug to cure and/or prevent kidney stone recurrences. Thus, further understanding of the pathophysiology of kidney stone formation is a research area to manage urolithiasis using new drugs. Therefore, this review has intended to provide a compiled up-to-date information on kidney stone etiology, pathogenesis, and prevention approaches.

Defining and Systematic Analyses of Aggregation Indices to Evaluate Degree of Calcium Oxalate Crystal Aggregation.

Crystal aggregation is one of the most crucial steps in kidney stone pathogenesis. However, previous studies of crystal aggregation were rarely done and quantitative analysis of aggregation degree was handicapped by a lack of the standard measurement. We thus performed an in vitro assay to generate aggregation of calcium oxalate monohydrate (COM) crystals with various concentrations (25–800 μg/ml) in saturated aggregation buffer. The crystal aggregates were analyzed by microscopic examination, UV-visible spectrophotometry, and GraphPad Prism6 software to define a total of 12 aggregation indices (including number of aggregates, aggregated mass index, optical density, aggregation coefficient, span, number of aggregates at plateau time-point, aggregated area index, aggregated diameter index, aggregated symmetry index, time constant, half-life, and rate constant). The data showed linear correlation between crystal concentration and almost all of these indices, except only for rate constant. Among these, number of aggregates provided the greatest regression coefficient (r = 0.997; p < 0.001), whereas the equally second rank included aggregated mass index and optical density (r = 0.993; p < 0.001 and r = −0.993; p < 0.001, respectively) and the equally forth were aggregation coefficient and span (r = 0.991; p < 0.001 for both). These five indices are thus recommended as the most appropriate indices for quantitative analysis of COM crystal aggregation in vitro.