KIM-1 Is a Potential Urinary Biomarker of Obstruction: Results from a Prospective Cohort Study

Targeted Drug Therapy for Senescent Cells Alleviates Unilateral Ureteral Obstruction-Induced Renal Injury in Rats

Hydronephrosis resulting from unilateral ureteral obstruction (UUO) is a common cause of renal injury, often progressing to late-stage renal fibrosis or even potential renal failure. Renal injury and repair processes are accompanied by changes in cellular senescence phenotypes. However, the mechanism is poorly understood. The purpose of this study is to clarify the changes in senescence phenotype at different time points in renal disease caused by UUO and to further investigate whether eliminating senescent cells using the anti-senescence drug ABT263 could attenuate UUO-induced renal disease. Specifically, renal tissues were collected from established UUO rat models on days 1, 2, 7, and 14. The extent of renal tissue injury and fibrosis in rats was assessed using histological examination, serum creatinine, and blood urea nitrogen levels. The apoptotic and proliferative capacities of renal tissues and phenotypic changes in cellular senescence were evaluated. After the intervention of the anti-senescence drug ABT263, the cellular senescence as well as tissue damage changes were re-assessed. We found that before the drug intervention, the UUO rats showed significantly declined renal function, accompanied by renal tubular injury, increased inflammatory response, and oxidative stress, alongside aggravated cellular senescence. Meanwhile, after the treatment with ABT263, the rats had a significantly lower number of senescent cells, attenuated renal tubular injury and apoptosis, enhanced proliferation, reduced oxidative stress and inflammation, improved renal function, and markedly inhibited fibrosis. This suggests that the use of the anti-senescence drug ABT263 to eliminate senescent cells can effectively attenuate UUO-induced renal injury. This highlights the critical role of cellular senescence in the transformation of acute injury into chronic fibrosis.

Current Status of Protein Biomarkers in Urolithiasis-A Review of the Recent Literature

Urolithiasis is an increasingly common clinical problem worldwide. The formation of stones is a combination of metabolic status, environmental factors, family history and many other aspects. It is important to find new ways to quickly detect and assess urolithiasis because it causes sudden, severe pain and often comes back. One way to do this is by exploring new biomarkers. Current advances in proteomic studies provide a great opportunity for breakthroughs in this field. This study focuses on protein biomarkers and their connection to kidney damage and inflammation during urolithiasis.

Advances in the study of subclinical AKI biomarkers

Acute kidney injury (AKI) is a prevalent and serious illness in all clinical departments, with a high morbidity and death rate, particularly in intensive care units, where prevention and treatment are crucial. As a result, active prevention, early detection, and timely intervention for acute kidney injury are critical. The current diagnostic criteria for acute kidney injury are an increase in serum creatinine concentration and/or a decrease in urine output, although creatinine and urine output merely reflect changes in kidney function, and AKI suggests injury or damage, but not necessarily dysfunction. The human kidney plays a crucial functional reserve role, and dysfunction is only visible when more than half of the renal mass is impaired. Tubular damage markers can be used to detect AKI before filtration function is lost, and new biomarkers have shown a new subset of AKI patients known as "subclinical AKI." Furthermore, creatinine and urine volume are only marginally effective for detecting subclinical AKI. As a result, the search for new biomarkers not only identifies deterioration of renal function but also allows for the early detection of structural kidney damage. Several biomarkers have been identified and validated. This study discusses some of the most promising novel biomarkers of AKI, including CysC, NGAL, KIM-1, lL-18, L-FABP, IGFBP7, TIMP-2, Clusterin, and Penkid. We examine their performance in the diagnosis of subclinical AKI, limitations, and future clinical practice directions.

The Use of Neutrophil Gelatinase-Associated Lipocalin (NGAL) as a Diagnostic and Prognostic Biomarker in Urinary Tract Obstruction: a Systematic Review

PURPOSE OF REVIEW

The early recognition of urinary tract obstruction (UTO) is vital in order to prevent mortality and morbidity associated with an acute kidney injury (AKI) and progression to irreversible kidney damage. Urinary biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL) have been recognised as an accurate tool in the timely diagnosis of AKI, but its role in the detection, prognosis and subsequent monitoring of a variety of obstructive uropathies has not yet been explored. We performed a systematic review of literature in accordance with Cochrane methodology from inception to August 2021.

RECENT FINDINGS

Eleven studies were included in which urine and serum NGAL were measured (616 patients) presenting with multiple UTO aetiologies. Four investigated kidney stone disease (KSD) exclusively, whilst other studies identified other causes of UTO including pelviureteric junction obstruction (PUJO), retroperitoneal fibrosis (RPF) and ureteric strictures. Six studies monitored NGAL levels after surgical intervention to relieve the obstruction. Nine studies demonstrated a significant increase in both urine and serum NGAL levels in UTO, often in a more sensitive and timely manner than serum creatinine. Subclinical unilateral UTO could be recognised by urinary NGAL levels even in the absence of changes in serum creatinine. Following surgical intervention, a reduction in urinary and serum NGAL was seen in all but two studies. NGAL levels decreased acutely by 14% in 2 h and showed a long-term reduction of 78% in 6 months. Readily available but not yet widely accepted, NGAL has the potential to be a less invasive, low-cost diagnostic test for urinary tract obstructions as a whole. Not only can it be used as a marker of treatment success but also to monitor for obstruction recurrence or progression. Further research is required to acknowledge urinary biomarkers such as NGAL as a potential replacement to standard renal function monitoring tests in the context of obstructive uropathy.

The Predicted Value of Kidney Injury Molecule-1 (KIM-1) in Healthy People

Purpose

Recent studies have focused on whether kidney injury molecule-1 (KIM-1) might serve as a marker of acute kidney tubular injury. Our study analyzed the levels of KIM-1 in the healthy population of different ages to explore the correlation between KIM-1 and age. Moreover, we constructed a model to predict kidney age.

Methods

A cross-sectional study was conducted by Huashan Hospital, Shanghai, China, between April 2020 and December 2020. KIM-1 and other kidney biomarkers were measured in 176 healthy individuals ranging from 26 to 91 years old. Statistical correlated analyses for urinary KIM-1, creatinine (uCREA), potassium (K), sodium (Na) and chlorine (Cl), plasmic renin, angiotensin-2 (AngII) and aldosterone (ALD), and serum microalbuminuria (MALB), β2-microglobulin (B2MG), cystatin C (CYSC), urea nitrogen (BUN), creatinine (CREA), and glucose (GLU) were performed to assess the correlation between age and kidney biomarkers. All variables were selected as independent variables for the prediction of age by multiple linear regression.

Results

KIM-1 positively correlated with age in kidney healthy people (r = 0.41, p < 0.05), whether among females (r = 0.51, p < 0.05) or males (r = 0.27, p < 0.05). It was much related to K (r = 0.34), B2MG (r = 0.28), and CL (r = 0.23). The predicted model was constructed with eGFR, Cl, ALD, CYSC, KIM-1, BUN, GLU and AngII, reaching an adjusted R² of 69.5% and a standard error of the estimated 7.84 years.

Conclusion

The level of urinary KIM-1 increases with age in healthy people. The model constructed by KIM-1 and the other 7 biomarkers can predict kidney age in healthy people.

Can Urinary KIM-1 and NGAL Predict Management Endoscopic Surgery in Acute Unilateral Obstructive Stone Disease? Results from a Prospective Cohort Study

INTRODUCTION

Kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) are the leading novel biomarkers used efficiently in acute kidney injury (AKI). The levels of these biomarkers increase especially in the early period of nephrotoxic and ischemic renal damage. In this study, we aimed to investigate the clinical importance of NGAL and KIM-1 biomarkers used in the effective evaluation of kidney functions in patients with acute unilateral obstructive stone disease (AUOSD) in the management of endoscopic surgery.

MATERIALS AND METHODS

We prospectively included patients who underwent endoscopic surgery due to AUOSD between January 2018 and December 2019. Urine KIM-1 and NGAL values of the patients were measured preoperative period, postoperative 4th h, and postoperative 7th day. The patients were evaluated according to the location and size of the stone, the degree of renal hydronephrosis, the duration of the operation, complications, and JJ stent placement.

RESULTS

The study enrolled 50 patients. Urinary KIM-1/Cr and urinary NGAL/Cr ratios were higher in postoperative 4th h than in others (p < 0.001). Also, we found that urinary KIM-1/Cr and urinary NGAL/Cr ratios with Grade 2 and higher hydronephrosis were statistically higher than Grade 0-1 hydronephrosis (p < 0.001 and p: 0.042, respectively). Additionally, a preoperative urinary KIM-1 value of 1.24 ng/mL had a sensitivity of 78% and a specificity of 63% to predict the presence of hydronephrosis. When urine KIM-1 and NGAL results were compared with surgery time, stone size and location, serum creatinine (sCr) value, and Post-Ureteroscopic Lesion Scale grade, the difference was not statistically significant. Postoperative 7th day NGAL/Cr and KIM-1/Cr ratios were statistically higher in those with JJ stents placed (p: 0.03 and p: 0.004, respectively).

CONCLUSION

KIM-1 and NGAL can be used in our assessment of renal function in patients with AUOSD, even if sCr is normal. Also, these biomarkers can predict the presence of hydronephrosis. It can be helpful in determining the time of surgical treatment, as well as providing information in the follow-up of patients with JJ stents after treatment.

Urine Biomarkers Combined With Ultrasound for the Diagnosis of Obstruction in Pediatric Hydronephrosis

Introduction: To establish the efficacy of ultrasound (US) combined with urine biomarkers in differentiating patients who require surgical management from those who do not, avoiding invasive investigations. Materials and Methods: From February 2019 to February 2021, all pediatric patients who presented with hydronephrosis were selected for the study. All renal units (RU) were evaluated by US, and fresh frozen voided urine samples were collected at the time of inclusion. Hydronephrosis grade was evaluated by the Society for Fetal Urology (SFU) and an alternative grading system (AGS). Patients who had high-grade hydronephrosis on US were referred to renal scan (RS) or intervention, when there was an increase of dilatation in subsequent follow-up images. Fresh frozen urine from the control group with no history of renal diseases and no renal anomalies on US was collected. We compared differences of US parameters combined with urine biomarkers between surgically and non-surgically managed patients and between the groups of patients when they were stratified by different RS findings and analyzed whether urinary biomarkers give any additional value to US. Instead of the anterior-posterior diameter (APD), we used its ratio with mid-parenchymal thickness. The additional efficacy of biomarkers to US was calculated when the US component was derived to a cumulative APD/mid-parenchymal ratio. Results: Sixty-four patients with hydronephrosis were prospectively included in the study accounting for a total of 81 patient visits and 162 RUs evaluated. A control group of 26 patients was collected. The mean age at inclusion in the hydronephrosis group was 43.7(±45.5) months, and a mean age in a control group was 61.2(±41.3) months. The cumulative APD/mid-parenchymal ratio combined with urinary albumin, β2 microglobulin (β2-M), and urinary neutrophil gelatinase-associated lipocalcin may have a better performance in the prediction of surgical intervention than the cumulative APD/mid-parenchymal ratio alone (p = 0.1). The best performance to detect the increased tissue transit time and obstructive curve on RS was demonstrated by the β2-M creatinine ratio. An increased cumulative APD/mid-parenchymal ratio with biomarkers together had a fairly good sensitivity and specificity for detection of DRF < 40%. Conclusions: According to our data, the APD/mid-parenchymal ratio alone has good efficacy in prediction of surgery and abnormal RS findings especially when combined with urine biomarkers.

Can urinary biomarkers detect obstruction defined by renal functional loss in antenatal hydronephrosis?

INTRODUCTION

Diagnosing obstruction and thus, assessment of need for surgery in the management of antenatal hydronephrosis may be challenging. Current diagnostic tests are not capable of indicating which patients are at risk for obstructive nephropathy. Biomarkers may play an important role in distinguishing these patients.

OBJECTIVE

The aim of this study is to evaluate if urinary biomarkers could differentiate obstruction (OBS) from non-obstructive dilation (NOD) in patients with antenatal hydronephrosis (AH) that underwent pyeloplasty due to loss of differential renal function (DRF).

STUDY DESIGN

Children with a history of AH and postnatal anteroposterior (AP) diameter ≥15 mm were included in this study of prospectively collected data between 2010 and 2018. The OBS group included patients who underwent pyeloplasty due to solely ≥10% subsequent decrease in DRF on a MAG-3 scan during follow-up. Patients with stable or improving hydronephrosis with no significant reduction in ipsilateral DRF (<10%) during follow-up formed the NOD group. Healthy children with no history of AH and a normal urinary ultrasound were taken as the control group. Urinary IP-10, MCP-1, KIM-1, NGAL, and Ca19-9 levels using ELISA were measured. In the OBS group, urine samples were obtained preoperatively and at 3rd post operative-month whereas in the NOD and control groups, samples were collected at the time of enrollment.

RESULTS

There were 24 children in the OBS and 27 children in the NOD groups. The control group consisted of 27 healthy children. The pre-operative bladder urine levels of biomarkers of the OBS group were significantly higher than in the NOD and control group (p < 0.05, for all). In terms of differentiating OBS from NOD, results of ROC analyses for the given cut-off values were as follows: 135.06 ng/mgCr (sensitivity 75%; specificity 66%, AUC = 0.735) for IP-10, 0.89 ng/mgCr (sensitivity 79.2%; specificity 88%, AUC = 0.802) for KIM-1, 367.65 pg/mgCr (sensitivity 62.5%; specificity 52%, AUC = 0.660) for MCP-1, 16.15 ng/mgCr (sensitivity 70.8%; specificity 70.4%, AUC = 0.669) for NGAL, and 55.5 U/mgCr (sensitivity 75%; specificity 66%, AUC = 0.676) for Ca 19-9. Moreover, when KIM-1 was combined with IP-10 and Ca19-9, sensitivity and specificity levels were 83% and 85% (AUC = 0.919), respectively.

CONCLUSION

In this novel study, which focused on scintigraphic DRF loss, KIM-1 was the most successful among all the biomarkers evaluated. Combination of IP-10, Ca19-9 and KIM-1 resulted increased diagnostic ability.

Roles Played by Biomarkers of Kidney Injury in Patients with Upper Urinary Tract Obstruction

Partial or complete obstruction of the urinary tract is a common and challenging urological condition caused by a variety of conditions, including ureteral calculi, ureteral pelvic junction obstruction, ureteral stricture, and malignant ureteral obstruction. The condition, which may develop in patients of any age, induces tubular and interstitial injury followed by inflammatory cell infiltration and interstitial fibrosis, eventually impairing renal function. The serum creatinine level is commonly used to evaluate global renal function but is not sensitive to early changes in the glomerular filtration rate and unilateral renal damage. Biomarkers of acute kidney injury are useful for the early detection and monitoring of kidney injury induced by upper urinary tract obstruction. These markers include levels of neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemotactic protein-1, kidney injury molecule 1, N-acetyl-b-D-glucosaminidase, and vanin-1 in the urine and serum NGAL and cystatin C concentrations. This review summarizes the pathophysiology of kidney injury caused by upper urinary tract obstruction, the roles played by emerging biomarkers of obstructive nephropathy, the mechanisms involved, and the clinical utility and limitations of the biomarkers.

Urinary kidney injury molecule-1: a novel biomarker to monitor renal function in patients with unilateral ureteral obstruction

PURPOSE

This study aimed to investigate the clinical significance of urinary kidney injury molecule-1 (KIM-1) to monitor renal function in patients with obstructive unilateral ureteral calculi.

METHODS

Kidneys of 12 male C57BL/6J mice, as well as their urine and plasma specimens, were extracted to detect KIM-1 expressions 24 h after unilateral ureteral obstruction (UUO) construction or sham surgery. Meanwhile, a cohort of 89 patients with unilateral ureteral calculi was retrospectively reviewed. 46 of which received double-J ureteral stent indwelling (group 1) and the remaining 43 were treated conservatively (group 2). Urinary KIM-1 levels in the baseline, 2 h and 1 day after treatments were analyzed.

RESULTS

KIM-1 expressions were dramatically higher in mice underwent UUO surgery when compared with the sham group. Clinical data showed urinary KIM-1 levels decreased as time went by for patients in group 1 (1.787 ± 1.081 ng/mL for baseline, 1.668 ± 1.162 ng/mL for 2 h and 0.935 ± 0.526 ng/mL for 1 day after operation; p = 0.0001). Nevertheless, for those in group 2, a mild increase (1.659 ± 0.997 ng/mL, 1.691 ± 0.872 ng/mL and 1.675 ± 0.911 ng/mL, correspondingly; p = 0.9869) was observed. Additionally, a urinary KIM-1 value of 1.04 ng/mL had a sensitivity of 83.1% and specificity of 62.5% to predict the presence of hydronephrosis (95% CI: 0.641-0.873, AUC: 0.757, p < 0.001).

CONCLUSIONS

Urinary KIM-1 is a sensitive biomarker of post-renal acute kidney injury (AKI) and might predict the presence of hydronephrosis. It can be used as an effective surrogate to monitor renal function.

Evaluation of dynamic thiol-disulphide homeostasis in obstructive uropathy

PURPOSE

To evaluate the ability of thiol-disulphide homeostasis to predict renal injury in ureteral obstruction by matching renal scintigraphy and pathological findings in an experimental rat model.

METHODS

24 rats were randomized and divided into 3 groups as sham, partial and complete. Blood samples for biochemical evaluations and dimercaptosuccinic acid (DMSA) renal scintigraphy were performed at the beginning and on the 7th day postoperatively. Only a midline abdominal incision was done in sham group. Left ureter of partial group was dissected and gently buried into the psoas muscle. In complete group, left ureter was dissected and ligated.

RESULTS

Statistically significant association was found between left kidney function loss percentage, native thiol, total thiol and creatinine alterations and pathological EGTI (Endothelial, Glomerular, Tubular, Interstitial) scores (r = - 0.867, r = - 0.815, r = 0.745, r = - 0.911; p = 0.000). Statistically significant difference was detected between groups in terms of postoperative native thiol and total thiol values (p = 0.000, p = 0.001). There was also a significant difference in preoperative and postoperative comparisons of these parameters in partial and complete obstruction groups (p = 0.012, p = 0.018). There was a significant difference in terms of postoperative disulphide/native thiol and native thiol/total thiol ratios in complete obstruction group compared to other groups (p₁ = 0.011, p₂ = 0.040; p₁ = 0.015, p₂ = 0.028).

CONCLUSIONS

Association with scintigraphic and pathological results empowers the value of this parameter. Disulphide/native thiol and native thiol/total thiol ratios indicate complete obstruction. These findings may shed light to more comprehensive studies.

First-year profile of biomarkers for early detection of renal injury in infants with congenital urinary tract obstruction

BACKGROUND

Diagnosis of renal function impairment and deterioration in congenital urinary tract obstruction (UTO) continues to be extremely challenging. Use of renal biomarkers in this setting may favor early renal injury detection, allowing for a reliable choice of optimal therapeutic options and prevention or minimization of definitive renal damage.

METHODS

This longitudinal, prospective study analyzed the first-year profile of two serum renal biomarkers: creatinine (sCr) and cystatin C (sCyC); and six urinary renal biomarkers: neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), transforming growth factor beta-1 (TGF-β1), retinol-binding protein (RBP), cystatin C (uCyC), and microalbuminuria (μALB) in a cohort of 37 infants with UTO divided into three subgroups: 14/37 with unilateral hydro(uretero)nephrosis, 13/37 with bilateral hydro(uretero)nephrosis, and 10/37 patients with lower urinary tract obstruction (LUTO), compared with 24 healthy infants matched by gestational age and birth weight.

RESULTS

All urine biomarkers showed significantly higher values at the first month of life (p ≤ 0.009), while NGAL (p = 0.005), TGF-ß1 (p < 0.001), and μALB (p < 0.001) were high since birth compared to controls. Best single biomarker performances were RBP in bilateral hydronephrosis and LUTO subgroups and KIM-1 in unilateral hydronephrosis subgroup. Best biomarker combination results for all subgroups were obtained by matching RBP with TGF-ß1 or KIM-1 and NGAL with CyC ([AUC] ≤ 0.934; sensitivity ≤ 92.4%; specificity ≤ 92.8%).

CONCLUSIONS

RBP, NGAL, KIM-1, TGF-ß1, and CyC, alone and especially in combination, are relatively efficient in identifying surgically amenable congenital UTO and could be of practical use in indicating on-time surgery.

Atypical Causes of Urinary Tract Obstruction

Acute kidney injury due to urinary tract obstruction invariably suggests lower urinary tract obstruction or bilateral ureteric obstruction since obstruction of a single kidney while the contralateral kidney is normal and not obstructed would not cause a perceptible rise in creatinine. Assuming a total body volume of 42 L, 70 kg male that generates approximately 1400 mg of creatinine daily (20 mg/kg/day) who has complete urinary tract obstruction would experience a 3.33 mg/dL per day increase in serum creatinine. Thus, for an individual who had prior normal renal function and who presents with a creatinine of 30 mg/dL, one could surmise that the obstructive pathology had lasted at least 10 days. However, the rise in serum creatinine is a poor marker of renal injury and subsequent prognosis. Urinary tract obstruction leading to AKI can be due to a variety of causes, and its management is tailored to the underlying etiology. This case series describes the varied clinical course of four patients at our center who experienced AKI from atypical causes of obstructive uropathy. Current and future diagnostic modalities and caveats in the treatment of this disease entity are also discussed.

A Novel Biomarker for Acute Kidney Injury, Vanin-1, for Obstructive Nephropathy: A Prospective Cohort Pilot Study

Background: Vanin-1 is a novel acute kidney injury (AKI) biomarker that has not been clinically investigated as a biomarker for obstructive nephropathy. This study investigated the diagnostic value of vanin-1 as a biomarker for adult obstructive nephropathy by comparing it to existing AKI biomarkers. Methods: A total of 49 patients, 21 controls, and 28 hydronephrosis (HN) cases were assessed. AKI biomarkers in bladder (BL) urine and renal pelvic (RP) urine in the HN group were compared to each BL marker in the control group. In a subgroup of cases receiving interventions for obstructive nephropathy, the BL values of each biomarker were assessed after the intervention. Results: RP vanin-1 levels were significantly higher while BL vanin-1 levels were marginally higher in the HN group than in the control group. The area under the receiver operating characteristics curve values for RP and BL vanin-1 were 0.9778 and 0.6386, respectively. In multivariate analyses, BL vanin-1 and N-acetyl-β-D-glucosaminidase (NAG), but not kidney injury molecule-1 (KIM-1) or neutrophil gelatinase-associated lipocalin (NGAL), were independent factors for predicting the presence of HN. In cases receiving interventions, vanin-1 decreased significantly from 1 week after the intervention in cases of moderate to severe obstructive nephropathy compared to RP values at baseline. Conclusion: Urinary vanin-1 is a useful biomarker to detect and monitor the clinical course of obstructive nephropathy.

Elevated urinary lipocalin-2, interleukin-6 and monocyte chemoattractant protein-1 levels in children with congenital ureteropelvic junction obstruction

INTRODUCTION

In children with congenital ureteropelvic junction obstruction (UPJO), urinary biomarkers could assist in the diagnosis of renal damage or kidneys at risk for damage. Urinary levels of interleukin-6 (IL6), neutrophil gelatinase-associated lipocalin (LCN2), monocyte chemoattractant protein-1 (MCP1), and transforming growth factor-β1 (TGFB1) proteins have been correlated with renal damage in several contexts. Whether they might be useful non-invasive biomarkers of obstructive nephropathy due to unilateral and bilateral congenital UPJO was tested.

PATIENTS AND METHODS

A cohort study was performed at People's Hospital of Xinjiang Uygur Autonomous Region in China. Bladder urine samples from 17 patients with UPJO were obtained before surgical intervention and from 17 healthy age-matched controls. Levels of IL6, LCN2, MCP1, and TGFB1 were determined by enzyme-linked immunosorbent assay and normalized to urinary creatinine levels.

RESULTS

Levels of urinary LCN2, MCP1, and IL6 were significantly elevated in the urine from individuals with UPJO compared with controls (P = 0.0003, P = 0.0003, and P = 0.0073, respectively). Children with bilateral UPJO (n = 5) showed significantly higher levels of IL6, LCN2, and MCP1 protein in their urine compared with controls or those with unilateral UPJO (n = 12; P = 0.007, P < 0.0001, and P = 0.0002, respectively). Combining LCN2 and MCP1 slightly improved biomarker performance.

DISCUSSION

Urinary biomarkers could be used in obstructed patients to monitor for renal damage and might find particular utility on patients with bilateral UPJO. Monitoring urinary biomarkers and imaging features in untreated patients could provide insights into the natural history of renal damage due to obstruction and will be necessary to test their performance characteristics as biomarkers.

CONCLUSIONS

Urinary levels of LCN2 and MCP1 protein are promising biomarkers monitoring children with UPJO, particularly in those with bilateral disease.

Potential Novel Biomarkers of Obstructive Nephropathy in Children with Hydronephrosis

Obstructive nephropathy (ON) secondary to the congenital hydronephrosis (HN) is one of the most common causes of chronic kidney disease in children. Neither currently used imaging techniques nor conventional laboratory parameters are sufficient to assess the onset and outcome of this condition; hence, there is a need to prove the usefulness of newly discovered biomarkers of kidney injury in this respect. The purpose of the study was to assess the urinary excretion of alpha-GST, pi-GST, NGAL, and KIM-1 and the serum level of NGAL in children with congenital unilateral hydronephrosis secondary to ureteropelvic junction obstruction. The results were evaluated in relation to severity of HN, the presence of ON, relative function of an obstructed kidney, and the presence of proteinuria. The study comprised 45 children with HN of different grades and 21 healthy controls. Urinary and serum concentrations of biomarkers were measured using specific ELISA kits. Urinary biomarker excretions were expressed as a biomarker/creatinine (Cr) ratio. Patients with the highest grades of HN showed significantly increased values of all measured biomarkers, whereas those with the lowest grades of HN displayed only significant elevation of urinary alpha-GST and the serum NGAL. Urinary NGAL positively correlated with percentage loss of relative function of an obstructed kidney in renal scintigraphy. In patients with proteinuria, significantly higher urinary alpha-GST excretion was revealed as compared to those without this symptom. The ROC curve analysis showed the best diagnostic profile for urinary alpha-GST/Cr and NGAL/Cr ratios in the detection of ON. In conclusion, the results of the study showed that urinary alpha-GST and NGAL are promising biomarkers of ON. Ambiguous results of the remaining biomarkers, i.e., urinary pi-GST and KIM-1, and serum NGAL level may be related to a relatively small study group. Their utility in an early diagnosis of ON should be reevaluated.

Identification of transcripts associated with renal damage due to ureteral obstruction as candidate urinary biomarkers

Renal obstruction is a common cause of renal failure in adults and children and is suspected when hydronephrosis is detected on imaging. Because not all cases of hydronephrosis are associated with renal damage, biomarkers are needed to guide intervention to relieve obstruction. We performed gene expression profiling on the kidneys from adult mice over a detailed time course after obstruction and compared these data with a neonatal model of bilateral high-grade obstruction induced by conditional deletion of the calcineurin β₁ gene. Having identified a set of 143 transcripts modulated in both adult and neonatal obstruction, we tested their expression in a model of short-term obstruction (1 day), where renal damage is transient and reversible, and long-term obstruction (5 days), where significant renal damage is permanent. A significant number of transcripts increased early after obstruction, and later normalized, while 26 transcripts remained elevated 10 and 28 days after relief of 5 days of ureteral obstruction. With the use of qPCR, elevated levels of several of these candidate RNA biomarkers of renal damage were detected in urine from obstructed mice. In addition, several of these candidate RNA biomarkers of damage resulting from obstruction were detectable in catheterized urine samples from children undergoing surgery for ureteropelvic junction obstruction. Measurement of urinary transcripts modulated in response to renal obstruction could serve as biomarkers of renal damage with important clinical applications.