New insights into the pathogenesis of renal calculi

Management of hypertension addressing hyperuricaemia: introduction of nano-based approaches

Uric acid (UA) levels in blood serum have been associated with hypertension, indicating a potential causal relationship between high serum UA levels and the progression of hypertension. Therefore, the reduction of serum UA level is considered a potential strategy for lowering and mitigating blood pressure. If an individual is at risk of developing or already manifesting elevated blood pressure, this intervention could be an integral part of a comprehensive treatment plan. By addressing hyperuricaemia, practitioners may subsidize the optimization of blood pressure regulation, which illustrates the importance of addressing UA levels as a valuable strategy within the broader context of hypertension management. In this analysis, we outlined the operational principles of effective xanthine oxidase inhibitors for the treatment of hyperuricaemia and hypertension, along with an exploration of the contribution of nanotechnology to this field.

Understanding formation processes of calcareous nephrolithiasis in renal interstitium and tubule lumen

Kidney stone, one of the oldest known diseases, has plagued humans for centuries, consistently imposing a heavy burden on patients and healthcare systems worldwide due to their high incidence and recurrence rates. Advancements in endoscopy, imaging, genetics, molecular biology and bioinformatics have led to a deeper and more comprehensive understanding of the mechanism behind nephrolithiasis. Kidney stone formation is a complex, multi-step and long-term process involving the transformation of stone-forming salts from free ions into asymptomatic or symptomatic stones influenced by physical, chemical and biological factors. Among the various types of kidney stones observed in clinical practice, calcareous nephrolithiasis is currently the most common and exhibits the most intricate formation mechanism. Extensive research suggests that calcareous nephrolithiasis primarily originates from interstitial subepithelial calcified plaques and/or calcified blockages in the openings of collecting ducts. These calcified plaques and blockages eventually come into contact with urine in the renal pelvis, serving as a nidus for crystal formation and subsequent stone growth. Both pathways of stone formation share similar mechanisms, such as the drive of abnormal urine composition, involvement of oxidative stress and inflammation, and an imbalance of stone inhibitors and promoters. However, they also possess unique characteristics. Hence, this review aims to provide detailed description and present recent discoveries regarding the formation processes of calcareous nephrolithiasis from two distinct birthplaces: renal interstitium and tubule lumen.

Risk Factors of Nephrolithiasis in a Tertiary Care Hospital in Rawalpindi: A Descriptive Cross-Sectional Study

Background

Nephrolithiasis (renal stones) is the most common urological disease. Its prevalence is high in every part of the world. Several factors lead to renal stone formation. In Pakistan, nephrolithiasis prevalence is also high as Pakistan is located in a region which is known as the salt belt. However, nephrolithiasis and its possible risk factors are under-researched in Pakistan.

Objective

This study aims to identify the risk factors for nephrolithiasis among admitted patients with renal stones. This may lead to a reduction in renal stone incidence and its allied complications by the prevention of risk factors that would have a major role in renal stone formation.

Material and methods

This descriptive cross-sectional study was performed among the 143 admitted patients with renal stones in the urology ward of Benazir Bhutto Hospital, Rawalpindi, for approximately six months from November 2021 to April 2022. Non-probability convenient sampling and developed inclusion and exclusion criteria were used for the recruitment of patients. After elaborating on the objectives, the study data were collected by interviewers through a self-structured questionnaire. Descriptive analysis was carried out using SPSS version 25.0 (IBM Corp., Armonk, NY).

Results

Nephrolithiasis was more prevalent among patients who had an age group range of 15-30 years (47.55%), male gender (56.65%), illiterate educational status (53.14%), lower socioeconomic status (66.43%), inadequate intake of water (61.53%), used tap water (56.64%), a habit of daily vegetable intake (65.04%), sedentary lifestyle (51.74%), family history of renal stones (57.34%), no diabetes mellitus (62.94%), no hypertension (52.45%), and overweight (48.23%).

Conclusion

In brief, the age group of 15-30 years, male gender, illiteracy, lower socioeconomic status, insufficient water intake, tap water, high vegetables, inactive lifestyle, family history of nephrolithiasis, and a high BMI all increase the risk of nephrolithiasis.

Comprehensive proteomic quantification of bladder stone progression in a cystinuric mouse model using data-independent acquisitions

Cystinuria is one of various disorders that cause biomineralization in the urinary system, including bladder stone formation in humans. It is most prevalent in children and adolescents and more aggressive in males. There is no cure, and only limited disease management techniques help to solubilize the stones. Recurrence, even after treatment, occurs frequently. Other than a buildup of cystine, little is known about factors involved in the formation, expansion, and recurrence of these stones. This study sought to define the growth of bladder stones, guided by micro-computed tomography imaging, and to profile dynamic stone proteome changes in a cystinuria mouse model. After bladder stones developed in vivo, they were harvested and separated into four developmental stages (sand, small, medium and large stone), based on their size. Data-dependent and data-independent acquisitions allowed deep profiling of stone proteomics. The proteomic signatures and pathways illustrated major changes as the stones grew. Stones initiate from a small nidus, grow outward, and show major enrichment in ribosomal proteins and factors related to coagulation and platelet degranulation, suggesting a major dysregulation in specific pathways that can be targeted for new therapeutic options.

The Activation of ROS/NF-κB/MMP-9 Pathway Promotes Calcium-Induced Kidney Crystal Deposition

Idiopathic hypercalciuria is an important risk factor for the formation of calcium-containing kidney stones. Matrix metalloproteinase-9 (MMP-9) is closely related to cell and tissue remodeling and is involved in ectopic tissue calcification. However, little is known about its role in kidney stone formation. In this study, we found that the expression of MMP-9 and that of osteoblastic-related proteins was increased in normal rat kidney epithelial-like (NRK-52E) cells following treatment with a high concentration of calcium, while the knockout or overexpression of MMP-9 could, respectively, significantly inhibit or upregulate the expression of osteoblastic-related proteins and calcium crystal deposition. In addition, apoptosis and calcium crystal deposition were significantly reduced in Sprague-Dawley rats with 1,25(OH)₂D₃-induced hypercalciuria following MMP-9 inhibitor I treatment. Furthermore, inhibiting reactive oxygen species (ROS) production or the nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) pathway significantly reduced calcium-induced MMP-9 expression and calcium crystal deposition. In summary, our results suggested that a high calcium concentration promotes epithelial-osteoblastic transformation and calcium crystal deposition in renal tubule cells by regulating the ROS/NF-κB/MMP-9 axis and identified a novel role for MMP-9 in regulating calcium-induced calcium crystal deposition in renal tubules.

Primary aldosteronism is associated with risk of urinary bladder stones in a nationwide cohort study

We analyzed database from the Taiwan National Health Insurance to investigate whether primary aldosteronism (PA) increases the risk of bladder stones. This retrospective nationwide population-based cohort study during the period of 1998–2011 compared patients with and without PA extracted by propensity score matching. Cox proportional hazard models and competing death risk model were used to estimate the hazard ratios (HRs), sub-hazard ratios (SHRs) and corresponding 95% confidence intervals (CIs). There were 3442 patients with PA and 3442 patients without PA. The incidence rate of bladder stones was 5.36 and 3.76 per 1000 person-years for both groups, respectively. In adjusted Cox hazard proportional regression models, the HR of bladder stones was 1.68 (95% CI 1.20–2.34) for patients with PA compared to individuals without PA. Considering the competing risk of death, the SHR of bladder stones still indicates a higher risk for PA than a comparison cohort (SHR, 1.79; 95% CI 1.30–2.44). PA, age, sex, and fracture number were the variables significantly contributing to the formation of bladder stones. In conclusion, PA is significantly associated with risk of bladder stones.

Urinary Stones and Risk of Coronary Heart Disease and Stroke: the Japan Public Health Center-Based Prospective Study

Aim: Evidence is lacking about whether urinary stones are associated with the subsequent risk of cardiovascular diseases. Herein, we investigated the association between history of urinary stones and the risk of coronary heart disease (CHD) and stroke among middle-aged Japanese.

Methods: This cohort study included 89,037 Japanese men and women (45–74 years) registered in the Japan Public Health Center-based prospective study. Cox proportional hazard models were used to calculate the hazard ratios (HRs) and their 95% confidence intervals (CIs) for incident CHD and stroke among Japanese adults with a self-reported history of urinary stones compared with those without it. The following covariates were included in the regression models: age, sex, area, body mass index, and histories of hypertension, diabetes, hyperlipidemia, smoking habit, alcohol intake, and physical activity.

Results: In total, 1.31% of Japanese adults reported a positive history of urinary stones. Throughout a median follow-up period of 12 years, 1.16% of Japanese adults developed CHD, and 4.96% developed stroke. No associations were detected between history of urinary stones and the risk of CHD (HR 1.04; 95% CI: 0.64–1.67), stroke (HR 0.92; 95% CI: 0.71–1.20), or total CVD (HR 0.95; 95% CI: 0.75–1.19). Younger urinary stone formers (45–59 years) tended to have a higher, though statistically insignificant, risk of CHD than older urinary stone formers (60–74 years): [(HR 1.15; 95% CI: 0.61–2.15) versus (HR 0.83; 95% CI: 0.40–1.76)], respectively.

Conclusion: The history of urinary stones was shown to be not associated with the risk of CVD among Japanese adults.

Oxalates, urinary stones and risk of cardiovascular diseases

Increased level of oxalates in urine and plasma can be attributed to endogenous overproduction, increased ingestion or excessive intestinal absorption. When a supersaturation status is reached, oxalates combine with calcium and crystallize to form 80% of the urinary stones. Several cardiovascular diseases such as coronary heart disease and stroke are thought to be associated with the formation of urinary stones via sharing the same pathogenesis and/or risk factors. This review investigated the evidence linking oxalates/urinary stones to cardiovascular diseases. Eventually, two theories can explain the possible association between urinary stones and cardiovascular diseases: the theory of common origin and the theory of common risk factors. While the first theory is based on the common vascular pathophysiology of urinary stones and cardiac events, the later suggests that metabolic syndrome traits increase the risk of urinary stones and cardiovascular diseases independently. A few cohort studies showed a higher risk of coronary heart disease and stroke among people with history of urinary stones than people without it while other cohort studies did not. These studies had different definitions for cardiovascular diseases, used various methods to assess urinary stones, and some of them did not control for potential confounders. When they were pooled together in meta-analyses, a significant heterogeneity across studies was observed. In conclusion, although there is some evidence indicating that urinary stones could increase the risk of cardiovascular diseases, a substantial causal relationship cannot be settled.

Targeted renal knockdown of Na+/H+ exchanger regulatory factor Sip1 produces uric acid nephrolithiasis in Drosophila

Nephrolithiasis is one of the most common kidney diseases, with poorly understood pathophysiology, but experimental study has been hindered by lack of experimentally tractable models. Drosophila melanogaster is a useful model organism for renal diseases because of genetic and functional similarities of Malpighian (renal) tubules with the human kidney. Here, we demonstrated function of the sex-determining region Y protein-interacting protein-1 (Sip1) gene, an ortholog of human Na⁺/H⁺ exchanger regulatory factor (NHERF1), in Drosophila Malpighian tubules and its impact on nephrolithiasis. Abundant birefringent calculi were observed in Sip1 mutant flies, and the phenotype was also observed in renal stellate cell-specific RNA interference Sip1 knockdown in otherwise normal flies, confirming a renal etiology. This phenotype was abolished in rosy mutant flies (which model human xanthinuria) and by the xanthine oxidase inhibitor allopurinol, suggesting that the calculi were of uric acid. This was confirmed by direct biochemical assay for urate. Stones rapidly dissolved when the tubule was bathed in alkaline media, suggesting that Sip1 knockdown was acidifying the tubule. SIP1 was shown to collocate with Na⁺/H⁺ exchanger isoform 2 (NHE2) and with moesin in stellate cells. Knockdown of NHE2 specifically to the stellate cells also increased renal uric acid stone formation, and so a model was developed in which SIP1 normally regulates NHE2 activity and luminal pH, ultimately leading to uric acid stone formation. Drosophila renal tubules may thus offer a useful model for urate nephrolithiasis.

Nonrenal Systemic Arterial Calcification Predicts the Formation of Kidney Stones

Background: Recent data indicate that kidney stone formers (KSFs) may have increased biomineralization at anatomic sites throughout the body compared with nonstone formers (NSFs). The objective of this study is to compare the volume of nonrenal systemic calcifications between KSF and NSF by using a standardized system to analyze calcifications in the abdominal aorta (AA) and splenic artery (SA). Methods: The NSF cohort was obtained from a kidney donor's prospectively maintained database. One hundred ninety-seven NSF were matched to 197 KSF based on age, gender, and body mass index. Noncontrast CT scans were evaluated and semiautomated CT software was utilized to provide an AA and SA calcification Agatston score. Wilcoxon rank-sum test was used on continuous variables and chi-squared test or Fisher's exact test on categorical variables. Odds ratios (ORs) were given for a variable's influence on the formation of stones or calcifications. Results: AA and SA calcifications were more prevalent in the KSF group (p = 0.011 and p = 0.027, respectively). KSFs were 1.9 times more likely to have intermediate or severe AA calcification than NSFs (OR = 1.9, p = 0.004). Severe AA calcifications had even a greater association (OR = 3.1, p = 0.019). KSFs were also more likely to have SA, but this did not reach statistical significance (OR = 3.7, p = 0.103). Conclusion: Patients with increased systemic calcifications, specifically aortic or splenic calcifications, may be at an increased risk for future kidney stone formation. Patients with these imaging findings and additional risk factors for stone disease may be counseled on the future risk of stones.

Urine proteomic profiling in patients with nephrolithiasis and cystinuria

PURPOSE

The purpose of the study was to assess the differences in the concentration and function of urinary proteins between patients with cystine stones (CYS) and healthy controls (HC). We postulated that CYS and HC groups would demonstrate different proteomic profiles.

METHODS

A pilot study was performed comparing urinary proteomes of 10 patients with CYS and 10 age- and gender-matched HC, using liquid chromatography-mass spectrometry. Proteins which met the selection criteria (i) ≥ 2 unique peptide identifications; (ii) ≥ twofold difference in protein abundance; and (iii) ≤ 0.05 p value for the Fisher's Exact Test were analyzed using Gene Ontology classifications.

RESULTS

Of the 2097 proteins identified by proteomic analysis, 398 proteins were significantly different between CYS and HC. Of those, 191 were involved in transport processes and 61 in inflammatory responses. The majority were vesicle-mediated transport proteins (78.5%), and 1/3 of them were down-regulated; of those, 12 proteins were involved in endosomal transport (including 6 charged multivesicular body proteins (CHMP) and 3 vacuolar sorting-associated proteins) and 9 in transmembrane transport. Myosin-2 and two actin-related proteins were significantly up-regulated in the vesicle-mediated transport group.

CONCLUSION

We provide proteomic evidence of impaired endocytosis, dysregulation of actin and myosin cytoskeleton, and inflammation in CYS. Endosomal transport proteins were down-regulated mainly through defective CHMP. These findings may contribute to further understanding of the pathogenesis of CYS, potentially affecting its management.

Is oxidized low-density lipoprotein the connection between atherosclerosis, cardiovascular risk and nephrolithiasis?

Nephrolithiasis is considered a systemic disease. A link has been established between nephrolithiasis, cardiovascular disease (CVD), the metabolic syndrome and atherosclerosis. A significant correlation has been found between the high levels of oxidized low-density lipoprotein (oxLDL) and CVD and atherosclerosis, including coronary and femoral artery disease. To the best of our knowledge, oxLDL has not been evaluated in patients with nephrolithiasis. This study aimed to evaluate serum levels of oxLDL, anti-oxLDL antibodies (oxLDL-ab) and other markers of atherosclerosis in patients with nephrolithiasis, according to the severity of the disease. The population sample consisted of 94 patients of 30-70 years of age with no symptoms of CVD who presented with renal calculi documented by ultrasonography, abdominal X-ray or computed tomography. The patients were divided into two groups: Group 1 (≥ 3 stones) and Group 2 (1-2 stones). A comparison control group was formed with 21 healthy individuals. Enzyme-linked immunosorbent assays were used to assess oxLDL and oxLDL-ab. Lipid peroxidation indexes were also analyzed. Median serum oxLDL values were higher in Groups 1 and 2 compared to the control group (≥ 3 stones, p = 0.02; 1-2 stones, p = 0.03). Median serum anti-oxLDL antibody levels were lower in the patients in Group 1 compared to the controls (p = 0.03). There was no significant difference in the oxLDL/oxLDL-ab ratio between patients and controls. These findings suggest that this may be the link between nephrolithiasis and the greater incidence of atherosclerosis and cardiovascular disease in patients with kidney stones.

Urinary proteomics reveals association between pediatric nephrolithiasis and cardiovascular disease

PURPOSE

To study (1) the differences in the relative abundance of urinary proteins between children with kidney stones (RS) and hypercalciuria, hypocitraturia, normal metabolic work-up, and healthy controls (HC); (2) the association of these proteins with various diseases.

METHODS

Quantitative proteomic comparison of pooled urine from RS (N = 30, 24 females, mean age 12.95 ± 4.03 years) versus age- and gender-matched HC, using mass spectrometry. Relative protein abundance was estimated using spectral counting. Proteins of interest were selected using the following criteria: (1) ≥ 5 spectral counts; (2) ≥ twofold difference in spectral counts; and (3) ≤ 0.05 p value for the Fisher's Exact Test.

RESULTS

Of the 1813 proteins identified, 229 met the above criteria, with 162 proteins up-regulated in the RS group and 67 up-regulated in HC. The largest group of proteins (30 out of 229) was found to be associated with cardiovascular disease (CVD). Of those, 16 were involved in coagulation, fibrinolysis, and adhesion, 10 in inflammation, 5 in lipid transport and metabolism, and 4 in oxidative stress. All except two were exclusively found in children with hypercalciuria and hypocitraturia, and were not seen in children with normal metabolic work-up.

CONCLUSION

Using a proteomic approach, we found a significant association between hypercalciuric and hypocitraturic nephrolithiasis and CVD in children. The shared risk factors among both diseases are endothelial dysfunction and atherosclerosis caused by abnormal coagulation, adhesion, disturbance of lipid transport and metabolism, oxidative stress and inflammation. Further understanding of the pathophysiological link between nephrolithiasis and CVD is necessary for developing new therapeutic targets.

Development of a two-stage in vitro model system to investigate the mineralization mechanisms involved in idiopathic stone formation: stage 1-biomimetic Randall's plaque using decellularized porcine kidneys

Idiopathic calcium oxalate (CaOx) stone formers form stones that are commonly attached to calcium phosphate (CaP) deposits in the renal tissue, known as Randall's plaques (RP). Plaques are suggested to originate in the renal tubular basement membrane, where they exhibit a morphology of concentrically laminated apatitic spherules, while in the interstitial regions, the collagen fibrils and vesicles become mineralized. We hypothesize that these minerals might form by non-classical crystallization mechanisms, such as via amorphous precursors, some of which might originate from a polymer-induced liquid-precursor (PILP) process. Thus, our goal is to identify mineralogical 'signatures' of various stone formation mechanisms. To do this for idiopathic CaOx stones, we are developing a two-stage model system of CaP-CaOx composite stones, consisting of stage (1) CaP mineralized plaque, followed by stage (2) CaOx overgrowth into a stone. For the studies presented here, decellularized porcine kidneys were mineralized with CaP using polyaspartic acid or the protein osteopontin (OPN) to induce the PILP process and create biomimetic RP. Analysis of the PILP-mineralized tissues shows features that resemble the native plaques, including mineral spherules and collagen with intrafibrillar mineral. In contrast, the classical crystallization produced large apatitic spherulites, which is a very different morphology, but one which is also found in some stones. An alternative hypothesis regarding Randall's plaque, and if or when it becomes pathological, is discussed.

Three-dimensional evaluation of perirenal fat volume in patients with nephrolithiasis

The concept of adipose tissue as an organ unto itself represents a new medical construct; already differences in the volume of perirenal fat around a tumor-bearing kidney have been described. We hypothesized that renal calculi may have similar impact on perirenal fat or alternatively abnormalities in urinary metabolites may be the result of perirenal fat affecting renal metabolism and subsequent stone formation. Accordingly, we conducted a study utilizing three-dimensional imaging software to evaluate perirenal fat volume (PFV) in patients with nephrolithiasis. Among 40 patients with a history of unilateral nephrolithiasis who underwent percutaneous nephrolithotomy between 2010 and 2016, the following data were acquired: body mass index, past medical history, stone characteristics and composition (i.e., calcium oxalate, calcium phosphate, uric acid, and struvite calculi). In addition, patients were stratified by dominant stone composition (≥ 50% fraction). Bilateral PFV measurements were obtained using the preoperative computed tomography scan and specialized three-dimensional imaging software. The PFV of stone-bearing kidneys was significantly greater than non-stone-bearing kidneys (397.3 and 323 cc, respectively; p = 0.004), with the PFV difference in patients with CO-dominant stone-bearing kidneys reaching statistical significance (p = 0.003). Subgroup analysis showed greater PFV surrounding the stone-bearing kidney irrespective of gender (p = 0.03), with male patients possessing significantly greater stone-bearing (p = 0.01) and bilateral PFV (p = 0.01) compared to females. No significant correlations were found between PFV and stone volume or stone density. The PFV of calcium oxalate stone-bearing kidneys is significantly greater than non-stone-bearing kidneys for both male and female patients with nephrolithiasis.

Investigation of Adipose Tissue Fatty Acid Composition in Men with Uronephrolithiasis and Metabolic Syndrome

Background

Fatty acids (FA) and their metabolites are closely related to some mechanisms involved in the development of uronephrolithiasis. The aim of this study was to evaluate the relationship between FA composition and type of kidney stones.

Material/Methods

Abdominal adipose tissue fatty acid methyl esters of 71 men with nephrolithiasis were identified by GC/MS, and the type of kidney stones was identified using FTIR infrared spectroscopy. Patients were divided into groups according to diagnosis of metabolic syndrome (MS) and type of kidney stone. The composition of FA was compared within different groups of patients with different types of kidney stones and between the patients and healthy individuals (control group) (n=100).

Results

Individuals with nephrolithiasis had a significantly higher level of monounsaturated fatty acids (MUFA) and a lower level of polyunsaturated fatty acids (PUFA) versus healthy individuals. Patients with MS had a higher level of 18: 1ω9 and a lower level of 16: 1ω7 than patients without MS. Individuals with nephrolithiasis, but without MS, had a higher level of saturated fatty acids (SFA) compared to controls. The level of PUFA was higher in the control group (p<0.0001) compared to individuals with uronephrolithiasis, with or without MS. PUFA, ω – 6 PUFA, and 18: 2ω6 were higher in patients with calcium-based kidney stones without MS versus patients with uric acid kidney stones with MS.

Conclusions

The levels of MUFA were significantly higher and the levels of PUFA were significantly lower in patients with uronephrolithiasis compared to controls.

Effects of statin treatment with atorvastatin on urolithiasis-associated urinary metabolic risk factors: an experimental study

PURPOSE

To investigate whether atorvastatin has favorable effects on urinary metabolic risk factors associated with urolithiasis.

METHODS

Sixteen male Sprague-Dawley rats were randomly divided into two groups, and baseline spot and 24-h urine samples were collected. Distilled water and atorvastatin were administered to rats during 4 weeks in the control and atorvastatin groups, respectively. At the end of the experimental procedure, spot and 24-h urine samples were collected again. Citrate, oxalate, cystine, uric acid, calcium and magnesium levels were determined in 24-h urine samples. Citrate/creatinine, oxalate/creatinine, uric acid/creatinine, calcium/creatinine and magnesium/creatinine ratios were also calculated in spot urine samples. Comparison of the baseline and post-experimental levels of these parameters was made in each group.

RESULTS

The majority of the parameters were similar before and after the experimental procedure in each group. In the atorvastatin group, uric acid and calcium levels were affected. Administration of atorvastatin was significantly decreased the levels of uric acid, whereas increased the levels of calcium (P = 0.025 and P = 0.017, respectively).

CONCLUSIONS

Our study revealed that atorvastatin has decreasing effect on U_Ua levels, whereas increasing effect on U_Ca levels. We think it cannot certainly be deduced that atorvastatin could be beneficial on overall urinary metabolic risk factors. Contrarily, atorvastatin may lead to an increased risk of calcium stones, but when considering its U_Ua decreasing effect, it may help in reducing the uric acid stone recurrence.

A case-control study on environmental and biological risk factors for renal calculi persisting in a coastal Union Territory, India

Background and Objectives:

Renal stone disease is a common disorder of the urinary tract and also a significant problem because of incidence, recurrence, and severe consequences. The complex pathogenetic mechanisms of renal stone formation involve both biologic and environmental risk factors. The present study was performed to identify the role of these parameters among renal stone patients and normal individuals from a coastal union territory region in South India.

Methods:

The authors conducted a case–control study of renal stone disease among outpatient department patients more than 30 years of age using systematic random sampling procedure with 100 study participants (50 subjects for each group). A questionnaire to explore some relevant history as well as to note general examination findings was used along with a house visit to collect a sample of water. Analysis was undertaken using appropriate statistical techniques.

Results:

The study showed statistically significant association for renal stones with female sex, illiteracy, body mass index (BMI) (>25 kg/m²), sodium (>50 mg/L), water consumption (<1.5 L/day), water source being borewell, consuming soft drink, sedentary work, and family history of renal stones. The adjusted odds ratios (ORs) were significantly higher for consuming soft drink (OR: 8.19; 95% confidence interval: 1.99–33.69), sedentary work (10.01; 1.27–78.91), and water consumption < 1.5 L/day (7.73; 2.24–26.69).

Interpretation and Conclusions:

We conclude that in this part of India, female gender, illiteracy, high BMI, high sodium in drinking water, inadequate water consumption, borewell drinking water, soft-drink consumption, sedentary work, and family history of renal stones can lead to a significant increase in the risk of renal stone disease.

Vascular Disease and Kidney Stones: Abdominal Aortic Calcifications Are Associated with Low Urine pH and Hypocitraturia

OBJECTIVE

Vascular calcifications are associated with nephrolithiasis. Although studies have demonstrated correlations with vascular disease and calcium stones in kidney stone formers (KSF), an etiologic link has remained elusive. As a noncontrast CT (NCCT) scan is typically part of a stone evaluation, our objective was to evaluate the association of NCCT-based assessment of abdominal aortic calcifications (AACs) with 24-hour urine parameters and stone composition.

MATERIALS AND METHODS

Ninety-seven KSF were included with CT imaging and 24-hour urine studies. For each patient, semi-automated CT software was utilized to provide an AAC Agatston score from the celiac axis to the aortic bifurcation. Univariate analysis was performed to compare patients with or without AAC. Multivariate logistic regression was performed to assess for variables associated with 24-hour urine parameters and stone composition.

RESULTS

The presence of AAC was associated with hypertension, diabetes, peripheral vascular disease, and coronary artery disease. Patients with any AAC showed lower 24-hour urine citrate (399 vs 593 mg/day, p < 0.001) and lower 24-hour urine pH (5.862 vs 6.328, p = 0.003). When controlling for age, system comorbidities, the presence of AAC was associated with low urine pH <6 (odds ratio [OR] 2.86, p = 0.032) and hypocitraturia <320 mg/day (OR 4.37, p = 0.005). The receiver operating characteristic curve showed that increasing AAC was associated with low urine pH (area under the curve [AUC] 0.683, p = 0.002) and uric acid stone formation (AUC 0.698, p = 0.045).

CONCLUSIONS

NCCT-based diagnosis of AAC is associated with low urine pH, hypocitraturia, and uric acid stone formation. The presence of AAC could be considered an additional prognosticator for the utility of alkalinization therapy.

The chemical disruption of human metabolism

BACKGROUND

Recent evidence highlights the reality of unprecedented human exposure to toxic chemical agents found throughout our environment - in our food and water supply, in the air we breathe, in the products we apply to our skin, in the medical and dental materials placed into our bodies, and even within the confines of the womb. With biomonitoring confirming the widespread bioaccumulation of myriad toxicants among population groups, expanding research continues to explore the pathobiological impact of these agents on human metabolism.

METHODS

This review was prepared by assessing available medical and scientific literature from Medline as well as by reviewing several books, toxicology journals, government publications, and conference proceedings. The format of a traditional integrated review was chosen.

RESULTS

Toxicant exposure and accrual has been linked to numerous biochemical and pathophysiological mechanisms of harm. Some toxicants effect metabolic disruption via multiple mechanisms.

CONCLUSIONS

As a primary causative determinant of chronic disease, toxicant exposures induce metabolic disruption in myriad ways, which consequently result in varied clinical manifestations, which are then categorized by health providers into innumerable diagnoses. Chemical disruption of human metabolism has become an etiological determinant of much illness throughout the lifecycle, from neurodevelopmental abnormalities in-utero to dementia in the elderly.

Short-Term Changes in Algometry, Inclinometry, Stabilometry, and Urinary pH Analysis After a Thoracolumbar Junction Manipulation in Patients with Kidney Stones

OBJECTIVES

To determine the efficacy of a high-velocity low-amplitude manipulation of the thoracolumbar junction in different urologic and musculoskeletal parameters in subjects suffering from renal lithiasis.

DESIGN

Randomized, controlled blinded clinical study.

SETTINGS/LOCATION

The Nephrology departments of two hospitals and one private consultancy of physiotherapy in Valencia (Spain).

SUBJECTS

Forty-six patients suffering from renal lithiasis.

INTERVENTIONS

The experimental group (EG, n = 23) received a spinal manipulation of the thoracolumbar junction, and the control group (CG, n = 23) received a sham procedure.

OUTCOME MEASURES

Pressure pain thresholds (PPTs) of both quadratus lumborum and spinous processes from T10 to L1, lumbar flexion range of motion, stabilometry, and urinary pH were measured before and immediately after the intervention. A comparison between pre- and postintervention phases was performed and an analysis of variance for repeated measures using time (pre- and postintervention) as intrasubject variable and group (CG or EG) as intersubject variable.

RESULTS

Intragroup comparison showed a significant improvement for the EG in the lumbar flexion range of motion (p < 0.001) and in all the PPT (p < 0.001 in all cases). Between-group comparison showed significant changes in PPT in quadratus lumborum (p < 0.001), as well as in the spinous processes of all of the evaluated levels (p < 0.05). No changes in urinary pH were observed (p = 0.419).

CONCLUSION

Spinal manipulation of the thoracolumbar junction seems to be effective in short term to improve pain sensitivity, as well as to increase the lumbar spine flexion.

Urolithiasis analysis in a multiethnic population at a tertiary hospital in Nairobi, Kenya

Background

Urolithiasis is a global problem whose incidence is reported to be on the rise across the world. Previously, urolithiasis was reported as being rare among the indigenous African population but recent data suggest otherwise. This study reviewed the demographic and clinical characteristics of patients with urolithiasis seen at the Aga Khan University hospital Nairobi (AKUHN) as well as the chemical composition of the stones and the modalities of therapy used.

Methods

This was a retrospective study which utilized patients’ clinical and laboratory records from 2013 to 2014. Sixty-seven symptomatic patients with confirmed urolithiasis formed the study. This study aimed to describe the clinical characteristics of patients, modalities of treatment as well as the chemical composition of renal stones from patients diagnosed and managed for urolithiasis during a duration spanning 17 months. Wet chemistry was utilized for analyzing the chemical composition of the urinary calculi. Data on age, sex, symptoms, radiological investigations done, location of the calculi, chemical composition of calculi and therapeutic procedures instituted were extracted and analyzed.

Results

Ages ranged from 3 to 87 years with a median of 42; males were the majority (79%) and the commonest presenting symptoms were flank pain (91%) and dysuria (19%). The majority of the stones were located in the ureters (46%) and at the pelvi-ureteric junction (25%). A statistically significant difference in frequency of lodgment at the pelvi-ureteric site between males and females was noted. However, the number of female patients in this study was small and studies with larger numbers of female participants are required to confirm this observation. All stones contained calcium and oxalate, often as the only constituents (72%). In the remainder of the stones, other constituents such bicarbonate, ammonium, phosphorous, magnesium, uric acid and cystine occurred in varying combinations with calcium oxalate. Laser lithotripsy was the most performed therapeutic procedure (77.6%).

Conclusions

Males formed the majority of patient with urolithiasis. Overall, most of the calculi were located in the ureters except in women where the pelviureteric location was commoner. Stones containing calcium oxalate only were predominant across the age groups and in both sexes. Lithotripsy was the commonest mode of management.

Kidney stone nano-structure - Is there an opportunity for nanomedicine development?

BACKGROUND

Kidney stone analysis techniques are well-established in the field of materials characterization and provide information for the chemical composition and structure of a sample. Nanomedicine, on the other hand, is a field with an increasing rate of scientific research, a big budget and increasingly developing market. The key scientific question is if there is a possibility for the development of a nanomedicine to treat kidney stones.

MAJOR CONCLUSIONS

The main calculi characterization techniques such as X-ray Diffraction and Fourier Transform Infrared Spectroscopy can provide information about the composition of a kidney stone but not for its nanostructure. On the other hand, Small Angle X-ray Scattering and Nitrogen Porosimetry can show the nanostructural parameters of the calculi. The combination of the previously described parameters can be used for the development of nano-drugs for the treatment of urolithiasis, while no such nano-drugs exist yet.

GENERAL SIGNIFICANCE

In this study, we focus on the most well-known techniques for kidney stone analysis, the urolithiasis management and the search for possible nanomedicine for the treatment of kidney stone disease. We combine the results from five different analysis techniques in order to represent a three dimensional model and we propose a hypothetical nano-drug with gold nanoparticles. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editor: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.

Drosophila Malpighian Tubules: A Model for Understanding Kidney Development, Function, and Disease

The Malpighian tubules of insects are structurally simple but functionally important organs, and their integrity is important for the normal excretory process. They are functional analogs of human kidneys which are important physiological organs as they maintain water and electrolyte balance in the blood and simultaneously help the body to get rid of waste and toxic products after various metabolic activities. In addition, it receives early indications of insults to the body such as immune challenge and other toxic components and is essential for sustaining life. According to National Vital Statistics Reports 2016, renal dysfunction has been ranked as the ninth most abundant cause of death in the USA. This chapter provides detailed descriptions of Drosophila Malpighian tubule development, physiology, immune function and also presents evidences that Malpighian tubules can be used as a model organ system to address the fundamental questions in developmental and functional disorders of the kidney.

How do stones form? Is unification of theories on stone formation possible?

There are two basic pathways for formation of calcium based kidney stones. Most idiopathic calcium oxalate (CaOx) stones are formed in association with sub-epithelial plaques of calcium phosphate (CaP), known as Randall's plaques, on renal papillary surfaces. Crystal formation and retention within the terminal collecting ducts, the ducts of Bellini, leading to the formation of Randall's plugs, is the other pathway. Both pathways require supersaturation leading to crystallization, regulated by various crystallization modulators produced in response to changing urinary conditions. High supersaturation, as a result of a variety of genetic and environmental factors, leads to crystallization in the terminal collecting ducts, eventually plugging their openings into the renal pelvis. Stasis behind the plugs may lead to the formation of attached or unattached stones in the tubular lumen. Deposition of crystals on the plug surface facing the pelvic or tubular urine may result in stone formation on the Randall's plugs. Kidneys of idiopathic stone formers may be subjected to oxidative stress as a result of increased urinary excretion of calcium/oxalate/phosphate and/or decrease in the production of functional crystallization inhibitors or in relation to co-morbidities such as hypertension, atherosclerosis, or acute kidney injury. We have proposed that production of reactive oxygen species (ROS) causes dedifferentiation of epithelial/endothelial cells into osteoblast type cells and deposition of CaP in the basement membrane of renal tubules or vessels. Growth, aggregation and melding of CaP crystals leads to the formation of plaque which grows by further calcification of interstitial collagen and membranous vesicles. Plaque becomes exposed to pelvic urine once the covering papillary epithelium is breached. Surface layers of CaP are replaced by CaOx through direct transformation or demineralization of CaP and mineralization of CaOx. Alternatively, or in addition, CaOx crystals nucleate directly on the plaque surface. Stone growth may also depend upon supersaturation in the pelvic urine, triggering further nucleation, growth and aggregation.

Histological aspects of the "fixed-particle" model of stone formation: animal studies

Crystallization by itself is not harmful as long as the crystals are not retained in the kidneys and are allowed to pass freely down the renal tubules to be excreted in the urine. A number of theories have been proposed, and studies performed, to determine the mechanisms involved in crystal retention within the kidneys. It has been suggested that urinary transit through the nephron is too fast for crystals to grow large enough to be retained. Thus, free particle mechanism alone cannot lead to stone formation, and there must be a mechanism for crystal fixation within the kidneys. Animal model studies suggest that crystal retention is possible through both the free- and fixed-particle mechanisms. Crystal-cell interaction leads to pathological changes which promote crystal attachment to either epithelial cells or their basement membrane. Alternatively, crystals aggregate and produce large enough particles to block the tubules particularly at sites, where urinary flow is affected because of changes in the luminal diameter of the tubule. Crystal deposits plugging the openings of the ducts of Bellini may be the result of such a phenomenon. Intratubular crystals translocating to renal interstitium may produce osteogenic changes in the epithelial or endothelial cells resulting in the formation of the Randall's plaques. Thus, fixation appears to be either through the formation of Randall's plugs, crystal plugs clogging the openings of the ducts of Bellini or sub-epithelial crystal deposits, and the Randall's plaques.

Kidney stones

Kidney stones are mineral deposits in the renal calyces and pelvis that are found free or attached to the renal papillae. They contain crystalline and organic components and are formed when the urine becomes supersaturated with respect to a mineral. Calcium oxalate is the main constituent of most stones, many of which form on a foundation of calcium phosphate called Randall's plaques, which are present on the renal papillary surface. Stone formation is highly prevalent, with rates of up to 14.8% and increasing, and a recurrence rate of up to 50% within the first 5 years of the initial stone episode. Obesity, diabetes, hypertension and metabolic syndrome are considered risk factors for stone formation, which, in turn, can lead to hypertension, chronic kidney disease and end-stage renal disease. Management of symptomatic kidney stones has evolved from open surgical lithotomy to minimally invasive endourological treatments leading to a reduction in patient morbidity, improved stone-free rates and better quality of life. Prevention of recurrence requires behavioural and nutritional interventions, as well as pharmacological treatments that are specific for the type of stone. There is a great need for recurrence prevention that requires a better understanding of the mechanisms involved in stone formation to facilitate the development of more-effective drugs.

Coronary Artery Calcium Score and Association with Recurrent Nephrolithiasis: The Multi-Ethnic Study of Atherosclerosis

PURPOSE

Subclinical coronary artery calcification is an established predictor of cardiovascular events. While a history of kidney stones has been linked to subclinical carotid atherosclerosis, to our knowledge no study has examined its relationship with coronary artery calcification. We studied the association between kidney stone history and prevalent coronary artery calcification in MESA (Multi-Ethnic Study of Atherosclerosis).

MATERIALS AND METHODS

MESA is a multisite cohort study of participants 45 to 84 years old without known cardiovascular disease at baseline from 2000 to 2002. Computerized tomography was done in 3,282 participants at followup in 2010 to 2012 to determine coronary artery calcification and kidney stone history was assessed by self-report. Coronary artery calcification scores were categorized as none-0, mild-1 to 99, moderate-100 to 399 or severe-400 or greater. Cross-sectional analysis was performed adjusting for demographic and dietary factors related to kidney stones.

RESULTS

The prevalence of kidney stone disease history was approximately 9%, mean ± SD participant age was 69.5 ± 9.3 years, 39% of participants were Caucasian, 47% were men and 69% had detectable coronary artery calcification (score greater than 0). No difference in the score was seen between single stone formers and nonstone formers. Recurrent kidney stone formation was associated with moderate or severe calcification on multivariable logistic regression vs none or mild calcification (OR 1.80, 95% CI 1.22-2.67). When coronary artery calcification scores were separated into none, mild, moderate and severe calcification, recurrent stone formation was associated with a higher score category on multivariable ordinal logistic regression (OR 1.44 per category, 95% CI 1.04-2.01).

CONCLUSIONS

Recurrent kidney stone formation is associated with subclinical coronary atherosclerosis. This association appeared stronger with coronary artery calcification severity than with coronary artery calcification presence.

Osteogenic changes in kidneys of hyperoxaluric rats

Many calcium oxalate (CaOx) kidney stones develop attached to renal papillary sub-epithelial deposits of calcium phosphate (CaP), called Randall's plaque (RP). Pathogenesis of the plaques is not fully understood. We hypothesize that abnormal urinary environment in stone forming kidneys leads to epithelial cells losing their identity and becoming osteogenic. To test our hypothesis male rats were made hyperoxaluric by administration of hydroxy-l-proline (HLP). After 28days, rat kidneys were extracted. We performed genome wide analyses of differentially expressed genes and determined changes consistent with dedifferentiation of epithelial cells into osteogenic phenotype. Selected molecules were further analyzed using quantitative-PCR and immunohistochemistry. Genes for runt related transcription factors (RUNX1 and 2), zinc finger protein Osterix, bone morphogenetic proteins (BMP2 and 7), bone morphogenetic protein receptor (BMPR2), collagen, osteocalcin, osteonectin, osteopontin (OPN), matrix-gla-protein (MGP), osteoprotegrin (OPG), cadherins, fibronectin (FN) and vimentin (VIM) were upregulated while those for alkaline phosphatase (ALP) and cytokeratins 10 and 18 were downregulated. In conclusion, epithelial cells of hyperoxaluric kidneys acquire a number of osteoblastic features but without CaP deposition, perhaps a result of downregulation of ALP and upregulation of OPN and MGP. Plaque formation may additionally require localized increases in calcium and phosphate and decrease in mineralization inhibitory potential.

Vascular Calcification and Stone Disease: A New Look towards the Mechanism

Calcium phosphate (CaP) crystals are formed in pathological calcification as well as during stone formation. Although there are several theories as to how these crystals can develop through the combined interactions of biochemical and biophysical factors, the exact mechanism of such mineralization is largely unknown. Based on the published scientific literature, we found that common factors can link the initial stages of stone formation and calcification in anatomically distal tissues and organs. For example, changes to the spatiotemporal conditions of the fluid flow in tubular structures may provide initial condition(s) for CaP crystal generation needed for stone formation. Additionally, recent evidence has provided a meaningful association between the active participation of proteins and transcription factors found in the bone forming (ossification) mechanism that are also involved in the early stages of kidney stone formation and arterial calcification. Our review will focus on three topics of discussion (physiological influences-calcium and phosphate concentration-and similarities to ossification, or bone formation) that may elucidate some commonality in the mechanisms of stone formation and calcification, and pave the way towards opening new avenues for further research.

Elemental Content of Calcium Oxalate Stones from a Canine Model of Urinary Stone Disease

One of the most common types of urinary stones formed in humans and some other mammals is composed of calcium oxalate in ordered hydrated crystals. Many studies have reported a range of metals other than calcium in human stones, but few have looked at stones from animal models such as the dog. Therefore, we determined the elemental profile of canine calcium oxalate urinary stones and compared it to reported values from human stones. The content of 19 elements spanning 7-orders of magnitude was quantified in calcium oxalate stones from 53 dogs. The elemental profile of the canine stones was highly overlapping with human stones, indicating similar inorganic composition. Correlation and cluster analysis was then performed on the elemental profile from canine stones to evaluate associations between the elements and test for potential subgrouping based on elemental content. No correlations were observed with the most abundant metal calcium. However, magnesium and sulfur content correlated with the mineral hydration form, while phosphorous and zinc content correlated with the neuter status of the dog. Inter-elemental correlation analysis indicated strong associations between barium, phosphorous, and zinc content. Additionally, cluster analysis revealed subgroups within the stones that were also based primarily on barium, phosphorous, and zinc. These data support the use of the dog as a model to study the effects of trace metal homeostasis in urinary stone disease.

Calcium oxalate calculi-induced clusterin expression in kidney

The aim of the study was to investigate clusterin expression in the kidney and evaluate the urine clusterin level in the kidney stone formers. (1) In vitro, we treated the Madin-Darby canine kidney (MDCK) cell line with different concentrations of calcium oxalate (CaOx), and then the clusterin protein expression in the cells was evaluated by Western blotting. (2) Kidney stone patients who received percutaneous nephrolithotomy were enrolled in our study. Urine samples were collected before surgery, the kidney punctured to obtain kidney tissue guided by ultrasound intraoperatively. Clusterin expression in the human kidney tissue was evaluated by immunochemistry. The urine clusterin level was determined by enzyme-linked immunosorbent assay. Non-kidney disease subjects were chosen as controls. In vitro, the clusterin expression was up-regulated in the MDCK cells induced by CaOx. The study included 49 patients and 41 non-kidney disease subjects. All calculi were composed of calcium oxalate monohydrate or calcium oxalate dihydrate and a few also contained protein or uric acid. Mean ± SD urine clusterin level was 17.47 ± 18.61 μg/ml in patients, and 3.31 ± 5.42 μg/ml in non-kidney disease subjects, respectively (p < 0.001). Immunohistochemistry revealed the clusterin was located in the cytoplasm of the renal distal and collecting tubular epithelial cells. Also the tissue clusterin expression increased significantly in the kidney stone formers compared to the control groups (p = 0.001). CaOx could induce clusterin expression in renal tubular cells, and increase clusterin levels in the kidney and urine from the kidney stone formers.

A Drosophila model identifies a critical role for zinc in mineralization for kidney stone disease

Ectopic calcification is a driving force for a variety of diseases, including kidney stones and atherosclerosis, but initiating factors remain largely unknown. Given its importance in seemingly divergent disease processes, identifying fundamental principal actors for ectopic calcification may have broad translational significance. Here we establish a Drosophila melanogaster model for ectopic calcification by inhibiting xanthine dehydrogenase whose deficiency leads to kidney stones in humans and dogs. Micro X-ray absorption near edge spectroscopy (μXANES) synchrotron analyses revealed high enrichment of zinc in the Drosophila equivalent of kidney stones, which was also observed in human kidney stones and Randall's plaques (early calcifications seen in human kidneys thought to be the precursor for renal stones). To further test the role of zinc in driving mineralization, we inhibited zinc transporter genes in the ZnT family and observed suppression of Drosophila stone formation. Taken together, genetic, dietary, and pharmacologic interventions to lower zinc confirm a critical role for zinc in driving the process of heterogeneous nucleation that eventually leads to stone formation. Our findings open a novel perspective on the etiology of urinary stones and related diseases, which may lead to the identification of new preventive and therapeutic approaches.

Dyslipidemia is associated with an increased risk of nephrolithiasis

The pathophysiology of nephrolithiasis is multifactorial. Obesity, diabetes mellitus and hypertension are implicated in its formation. Dyslipidemia (DLD) recently has received attention as well. Congruent with a vascular etiology in stone formation, DLD theoretically would predispose patients to nephrolithiasis. We investigated a possible association of DLD with nephrolithiasis. A random cohort of 60,000 patients was established by collecting the first 5,000 patient charts per month in the year 2000. After excluding pediatric patients, a retrospective study was performed by reviewing age, sex, comorbidities, and last patient follow-up. Median lipid laboratory levels also were reviewed. Descriptive statistics were performed as well as Cox proportional-hazards regression analysis, and univariate and multivariate analyses. 52,184 (22,717 women/29,467 men) patient charts were reviewed. The average age was 31.0 ± 15.2 years. On univariate analysis, DLD was associated with nephrolithiasis with a hazard ratio (HR) of 2.2 [Confidence Interval (CI), 1.9-2.5; p < 0.001] and on multivariate analysis HR = 1.2 (1.0-1.5; p = 0.033). Low-density lipoprotein and triglycerides had no association with stone disease. Patients with high-density lipoprotein (HDL) values <45 for men and <60 for women had an HR of 1.4 (1.1-1.7, 95% CI, p = 0.003) on univariate analysis and on multivariate analysis; HR = 1.27 (1.03-1.56; p = 0.024) for nephrolithiasis. DLD was associated with an increased risk of stone disease though the only specific lipid panel associated with lower nephrolithiasis was HDL. Clinicians should consider obtaining lipid levels with the intent that treatment could potentially not only mitigate atherosclerotic disease but also decrease nephrolithiasis risk.

Biomimetic Randall's plaque as an in vitro model system for studying the role of acidic biopolymers in idiopathic stone formation

Randall's plaque (RP) deposits seem to be consistent among the most common type of kidney stone formers, idiopathic calcium oxalate stone formers. This group forms calcium oxalate renal stones without any systemic symptoms, which contributes to the difficulty of understanding and treating this painful and recurring disease. Thus, the development of an in vitro model system to study idiopathic nephrolithiasis, beginning with RP pathogenesis, can help in identifying how plaques and subsequently stones form. One main theory of RP formation is that calcium phosphate deposits initially form in the basement membrane of the thin loops of Henle, which then fuse and spread into the interstitial tissue, and ultimately make their way across the urothelium, where upon exposure to the urine, the mineralized tissue serves as a nidus for overgrowth with calcium oxalate into a stone. Our group has found that many of the unusual morphologies found in RP and stones, such as concentrically laminated spherulites and mineralized collagenous tissue, can be reproduced in vitro using a polymer-induced liquid precursor (PILP) process, in which acidic polypeptides induce a liquid phase amorphous precursor to the mineral, yielding non-equilibrium crystal morphologies. Given that there are many acidic proteins and polysaccharides present in the renal tissue and urine, we have put forth the hypothesis that the PILP system may be involved in urolithiasis. Therefore, our goal is to develop an in vitro model system of these two stages of composite stone formation to study the role that various acidic macromolecules may play. In our initial experiments presented here, the development of "biomimetic" RP was investigated, which will then serve as a nidus for calcium oxalate overgrowth studies. To mimic the tissue environment, MatriStem(®) (ACell, Inc.), a decellularized porcine urinary bladder matrix was used, because it has both an intact epithelial basement membrane surface and a tunica propria layer, thus providing the two types of matrix constituents found associated with mineral in the early stages of RP formation. We found that when using the PILP process to mineralize this tissue matrix, the two sides led to dramatically different mineral textures, and they bore a striking resemblance to native RP, which was not seen in the tissue mineralized via the classical crystal nucleation and growth process. The interstitium side predominantly consisted of collagen-associated mineral, while the luminal side had much less mineral, which appeared to be tiny spherules embedded within the basement membrane. Although these studies are only preliminary, they support our hypothesis that kidney stones may involve non-classical crystallization pathways induced by the large variety of macromolecular species in the urinary environment. We believe that mineralization of native tissue scaffolds is useful for developing a model system of stone formation, with the ultimate goal of developing strategies to avoid RP and its detrimental consequences in stone formation, or developing therapeutic treatments to prevent or cure the disease. Supported by NIDDK grant RO1DK092311.

Unified theory on the pathogenesis of Randall's plaques and plugs

Kidney stones develop attached to sub-epithelial plaques of calcium phosphate (CaP) crystals (termed Randall's plaque) and/or form as a result of occlusion of the openings of the Ducts of Bellini by stone-forming crystals (Randall's plugs). These plaques and plugs eventually extrude into the urinary space, acting as a nidus for crystal overgrowth and stone formation. To better understand these regulatory mechanisms and the pathophysiology of idiopathic calcium stone disease, this review provides in-depth descriptions of the morphology and potential origins of these plaques and plugs, summarizes existing animal models of renal papillary interstitial deposits, and describes factors that are believed to regulate plaque formation and calcium overgrowth. Based on evidence provided within this review and from the vascular calcification literature, we propose a "unified" theory of plaque formation-one similar to pathological biomineralization observed elsewhere in the body. Abnormal urinary conditions (hypercalciuria, hyperoxaluria, and hypocitraturia), renal stress or trauma, and perhaps even the normal aging process lead to transformation of renal epithelial cells into an osteoblastic phenotype. With this de-differentiation comes an increased production of bone-specific proteins (i.e., osteopontin), a reduction in crystallization inhibitors (such as fetuin and matrix Gla protein), and creation of matrix vesicles, which support nucleation of CaP crystals. These small deposits promote aggregation and calcification of surrounding collagen. Mineralization continues by calcification of membranous cellular degradation products and other fibers until the plaque reaches the papillary epithelium. Through the activity of matrix metalloproteinases or perhaps by brute physical force produced by the large sub-epithelial crystalline mass, the surface is breached and further stone growth occurs by organic matrix-associated nucleation of CaOx or by the transformation of the outer layer of CaP crystals into CaOx crystals. Should this theory hold true, developing an understanding of the cellular mechanisms involved in progression of a small, basic interstitial plaque to that of an expanding, penetrating plaque could assist in the development of new therapies for stone prevention.

Interstitial calcinosis in renal papillae of genetically engineered mouse models: relation to Randall's plaques

Genetically engineered mouse models (GEMMs) have been highly instrumental in elucidating gene functions and molecular pathogenesis of human diseases, although their use in studying kidney stone formation or nephrolithiasis remains relatively limited. This review intends to provide an overview of several knockout mouse models that develop interstitial calcinosis in the renal papillae. Included herein are mice deficient for Tamm-Horsfall protein (THP; also named uromodulin), osteopontin (OPN), both THP and OPN, Na(+)-phosphate cotransporter Type II (Npt2a) and Na(+)/H(+) exchanger regulatory factor (NHERF-1). The baseline information of each protein is summarized, along with key morphological features of the interstitial calcium deposits in mice lacking these proteins. Attempts are made to correlate the papillary interstitial deposits found in GEMMs with Randall's plaques, the latter considered precursors of idiopathic calcium stones in patients. The pathophysiology that underlies the renal calcinosis in the knockout mice is also discussed wherever information is available. Not all the knockout models are allocated equal space because some are more extensively characterized than others. Despite the inroads already made, the exact physiological underpinning, origin, evolution and fate of the papillary interstitial calcinosis in the GEMMs remain incompletely defined. Greater investigative efforts are warranted to pin down the precise role of the papillary interstitial calcinosis in nephrolithiasis using the existing models. Additionally, more sophisticated, second-generation GEMMs that allow gene inactivation in a time-controlled manner and "compound mice" that bear several genetic alterations are urgently needed, in light of mounting evidence that nephrolithiasis is a multifactorial, multi-stage and polygenic disease.

Determination of calcium mobility in alkaline-cooked grounded corn in presence of a magnetic field

The mobility of calcium ions in corn dough prepared using commercial powder of alkaline-cooked grounded-corn kernel was determined in presence of a magnetic field. The ionic conduction was determined using 2 electrodes placed at 2 consecutives corners of the square samples: the excitation line was along one edge. Three different calcium concentrations [Ca] and 3 different magnetic field B conditions (B0, B-, B+) were analyzed; in all cases, the same amount of water was used. The relaxation times τ were determined by measuring the ionic current with and, immediately after, without excitation voltage. An empirical model, based on the obstruction effect characteristic of the ionic conduction and on the effect of the magnetic field B on the motion of the ions, was developed to explain the dependence of τ with [Ca] and B. The threshold concentration at which the Ca ions are not longer linked chemically to the starch molecules and move freely in the dough interior was obtained.

PRACTICAL APPLICATION

It was possible to determine the free-to-link threshold concentration for calcium ions in alkaline-cooked grounded-corn kernel dough; this is near 1.5% Ca. The magnetic field allows to separate and measuring different types of ions; a model to explain the dependence of the relaxation time with the magnetic field was included.

C-phycocyanin confers protection against oxalate-mediated oxidative stress and mitochondrial dysfunctions in MDCK cells

Oxalate toxicity is mediated through generation of reactive oxygen species (ROS) via a process that is partly dependent on mitochondrial dysfunction. Here, we investigated whether C-phycocyanin (CP) could protect against oxidative stress-mediated intracellular damage triggered by oxalate in MDCK cells. DCFDA, a fluorescence-based probe and hexanoyl-lysine adduct (HEL), an oxidative stress marker were used to investigate the effect of CP on oxalate-induced ROS production and membrane lipid peroxidation (LPO). The role of CP against oxalate-induced oxidative stress was studied by the evaluation of mitochondrial membrane potential by JC1 fluorescein staining, quantification of ATP synthesis and stress-induced MAP kinases (JNK/SAPK and ERK1/2). Our results revealed that oxalate-induced cells show markedly increased ROS levels and HEL protein expression that were significantly decreased following pre-treatment with CP. Further, JC1 staining showed that CP pre-treatment conferred significant protection from mitochondrial membrane permeability and increased ATP production in CP-treated cells than oxalate-alone-treated cells. In addition, CP treated cells significantly decreased the expression of phosphorylated JNK/SAPK and ERK1/2 as compared to oxalate-alone-treated cells. We concluded that CP could be used as a potential free radical-scavenging therapeutic strategy against oxidative stress-associated diseases including urolithiasis.