Elevated Levels of Urinary Biomarkers TIMP-2 and IGFBP-7 Predict Acute Kidney Injury in Neonates after Congenital Heart Surgery

Objectives  This article investigated the utility of urine biomarkers tissue inhibitor of metalloproteinase-2 (TIMP-2) and insulin-like growth factor binding protein-7 (IGFBP-7) in identifying acute kidney injury (AKI) in neonates after congenital heart surgery (CHS). TIMP-2 and IGFBP-7 are cell cycle arrest proteins detected in urine during periods of kidney stress/injury. Methods  We conducted a single-center, prospective study between September 2017 and May 2019 with neonates undergoing CHS requiring cardiopulmonary bypass (CPB). Urine samples were analyzed using NephroCheck prior to surgery and 6, 12, 24, and 96 hours post-CPB. All patients were evaluated using the Acute Kidney Injury Network (AKIN) criteria. Wilcoxon rank sum tests were used to compare the medians of the [TIMP-2*IGFBP-7] values in the AKIN negative and positive groups at each time point. Receiver operating characteristic curves were used to measure how well the [TIMP-2*IGFBP-7] values predict AKIN status. Results  Thirty-six patients were included. No patients met the AKIN criteria for AKI preoperatively. Postoperatively, 19 patients (53%) met the AKIN criteria for AKI diagnosis: 13 (36%) stage 1, 5 (14%) stage 2, and 1 (3%) stage 3. None required renal replacement therapy. At the 24-hour time points, patients who met the AKIN criteria for AKI had a statistically significantly higher [TIMP-2*IGFBP7] values than the patients without AKI (1.1 vs. 0.27 [ng/mL] ² /1,000) at 24 hours (adj- p  = 0.0019). Conclusion  AKI is a serious complication associated with adverse outcomes in patients undergoing cardiac surgery. [TIMP-2*IGFBP-7] urinary level 24 hours after CPB is a good predictor of AKI in this population.

Pulmonary Manifestations of Renal Disorders in Children

The causes of kidney disease in pediatric patients are evenly divided between congenital abnormalities of the kidney and urinary tract and acquired disorders. Nearly 10% to 15% of adults in the United States have chronic kidney disease (CKD); there are no comparable data in children. Regardless of patient age, CKD is a systemic problem that affects every organ system, including the lung. We review the tests used to diagnose and evaluate kidney disease and the main clinical syndromes that are likely to be encountered to aid the pulmonology consultant who is asked to evaluate patients with kidney disease.

Persistent Disease Activity in Patients With Long-Standing Glomerular Disease

Introduction

Methods

Results

Conclusion

Center Volume and Kidney Transplant Outcomes in Pediatric Patients

Rationale & Objectives

Recent data demonstrate that center volume is not a factor in the outcomes of adult kidney transplant recipients. This study assessed whether center volume affects graft survival in pediatric patients who received a kidney transplant.

Study Design

Case-cohort study.

Setting & Participants

Kidney transplantation centers, recipients younger than 18 years.

Results

Data were retrieved from the Scientific Registry of Transplant Recipients for transplantations performed July 1, 2010, to June 30, 2015, and the Organ Procurement and Transplantation Network for transplantations performed January 1, 2010, to December 30, 2015. Center volume was divided into 3 groups: low (<4 per year), intermediate (4-8 per year), and high (>8 per year). The primary outcome was 3-year graft survival rate. Outcomes were reviewed in 115 centers that performed 3,762 transplantations. There were no substantive differences in sex, age, ethnicity, diagnosis, and kidney donor profile index score in the 3 transplantation center volume categories. During the 5-year period (July 1, 2010, to June 30, 2015), 3-year graft survival in centers with low, intermediate, and high volumes were 88.4%, 90.3%, and 92.1%, respectively; P = 0.02. Although outcomes for deceased donor kidney recipients were similar in the 3 volume categories, outcomes in patients who received a living kidney donation were better in the high-volume centers. Low household income was associated with poorer outcomes. However, 3-year graft survival was similar in the 3 center volume categories in high and low mean household income states.

Limitations

Lack of information for complications and individual family household income of recipients.

Conclusions

Transplantation outcomes are worse in pediatric patients treated at lower-volume centers. The difference was more pronounced for patients receiving living versus deceased donor kidneys. The distribution of household income in pediatric transplant recipients may also be a factor that contributes to lower 3-year graft survival in low-volume centers.

Hypokalemia Associated With a Claudin 10 Mutation: A Case Report

Hypokalemia of renal origin can arise from genetic abnormalities in a variety of transporters or channel proteins that mediate tubular handling of potassium. Recently, mutations in claudin 10 have been documented in patients with hypokalemia in association with a range of other electrolyte abnormalities and skin and sweat gland manifestations. We report a 12-year-old Hispanic boy who presented with anhydrosis, aptyalism, alacrima, hypokalemia, and hypocalciuria, in whom we detected a homozygous mutation in the claudin 10 gene. During the 4-year follow-up period, he developed hypermagnesemia and a decline in estimated glomerular filtration rate to 59mL/min/1.73m². His unaffected parents and siblings were heterozygous for the mutation. We summarize the clinical phenotype encountered in patients with claudin 10 mutations. It is characterized by significant heterogeneity in electrolyte and extrarenal abnormalities and is associated with a risk for progressive loss of kidney function in up to 33% of cases. Awareness of this association between claudin 10 mutations and electrolyte abnormalities, namely hypokalemia and hypermagnesemia, sheds new light on the physiology of potassium and magnesium handling along the nephron and increases the likelihood of identifying the underlying tubular mechanism in patients with newly diagnosed hypokalemia with or without concomitant hypermagnesemia.

Early manifestations of renal disease in patients with tuberous sclerosis complex

Objectives

Renal manifestations are the second most significant cause of morbidity and mortality in patients with tuberous sclerosis complex (TSC), and include renal cysts, angiomyolipomas, fat-poor lesions, and malignant tumors. These lesions begin in childhood and often lead to chronic kidney disease (CKD). Little is known on the incidence of early modifiable risk factors of CKD, such as proteinuria and hypertension, or subtle decreases in glomerular filtration rate that correspond to the early stages of CKD in children with TSC. The impact of genotype on these early manifestations of CKD has not been investigated.

Design

Retrospective chart review of 84 children and young adults with TSC.

Measurements

This study assessed the prevalence of hypertension, renal impairment, and proteinuria, as well as the genotype–phenotype correlations.

Results

Children and young adults with TSC2 mutations had a significantly higher rate of renal lesions, hypertension (36% vs 14%), and decreased renal function than those with TSC1 mutations.

Conclusion

On the basis of estimated glomerular filtration rate and blood pressure, our findings are consistent with the hypothesis that TSC2 mutations are associated with more severe early renal involvement in children. There is a compelling need for close collaboration of nephrologists and neurologists to provide care to pediatric patients with TSC to improve screening and management of early manifestations of renal disease.

Association between perfluoroalkyl acids and kidney function in a cross-sectional study of adolescents

BACKGROUND

Perfluoroalkyl acids are synthetic compounds widely used in industrial and commercial applications. Laboratory studies suggest that these persistent and bioaccumulative chemicals produce oxidant stress and damage glomerular endothelial cells, raising concern regarding the impact of these compounds on renal function.

METHODS

We performed cross-sectional analyses of data 1960 participants aged 12-19 years of the 2003-2010 National Health and Nutrition Examination Surveys. PFAA exposure was assessed using levels of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid, and perfluorohexane sulfonic acid. Primary study outcomes were estimated glomerular filtration rate (eGFR) and serum uric acid.

RESULTS

While adjusting for demographics, cotinine, prehypertension, insulin resistance, body mass index, and hypercholesterolemia, adolescents in the highest PFOA and PFOS quartile had a lower eGFR, 6.84 mL/min/1.73 m(2) (95% CI: 2.19 to 11.48) and 9.69 mL/min/1.73 m(2) (95 % CI: -4.59 to 14.78), respectively, compared to the lowest quartile. Highest PFOA and PFOS quartiles were also associated with 0.21 mg/dL (95% CI: 0.056 to 0.37) and 0.19 mg/dL (95% CI: 0.032 to 0.34) increases in uric acid, respectively.

CONCLUSIONS

PFAAs are associated with a reduction in kidney function and increased uric acid levels in otherwise healthy adolescents. Reverse causation and residual confounding could explain the results. Our study results confirm and amplify previous findings, though longitudinal studies examining prenatal and childhood biomarkers in relationship with robust measures of childhood renal function are needed.

Deletion of Lkb1 in Renal Tubular Epithelial Cells Leads to CKD by Altering Metabolism

Renal tubule epithelial cells are high-energy demanding polarized epithelial cells. Liver kinase B1 (LKB1) is a key regulator of polarity, proliferation, and cell metabolism in epithelial cells, but the function of LKB1 in the kidney is unclear. Our unbiased gene expression studies of human control and CKD kidney samples identified lower expression of LKB1 and regulatory proteins in CKD. Mice with distal tubule epithelial-specific Lkb1 deletion (Ksp-Cre/Lkb1(flox/flox)) exhibited progressive kidney disease characterized by flattened dedifferentiated tubule epithelial cells, interstitial matrix accumulation, and dilated cystic-appearing tubules. Expression of epithelial polarity markers β-catenin and E-cadherin was not altered even at later stages. However, expression levels of key regulators of metabolism, AMP-activated protein kinase (Ampk), peroxisome proliferative activated receptor gamma coactivator 1-α (Ppargc1a), and Ppara, were significantly lower than those in controls and correlated with fibrosis development. Loss of Lkb1 in cultured epithelial cells resulted in energy depletion, apoptosis, less fatty acid oxidation and glycolysis, and a profibrotic phenotype. Treatment of Lkb1-deficient cells with an AMP-activated protein kinase (AMPK) agonist (A769662) or a peroxisome proliferative activated receptor alpha agonist (fenofibrate) restored the fatty oxidation defect and reduced apoptosis. In conclusion, we show that loss of LKB1 in renal tubular epithelial cells has an important role in kidney disease development by influencing intracellular metabolism.

Direct Reversible Kidney Injury in Familial Hemophagocytic Lymphohistiocytosis Type 3

Hemophagocytic lymphohistiocytosis is a hyperinflammatory disorder resulting from primary or secondary immune dysfunction. AKI is frequent in severe hemophagocytic lymphohistiocytosis and has been attributed to multiorgan failure or the use of nephrotoxic drugs, but AKI is rarely considered a direct consequence of the disease process. We describe a child with familial hemophagocytic lymphohistiocytosis type 3 who developed AKI requiring prolonged renal replacement therapy because of severe renal inflammation. There was massive infiltration of the renal parenchyma by activated macrophages and cytotoxic T cells, and acute tubular injury. The patient responded to high-dose intravenous methylprednisolone, which resulted in improvement of renal function and discontinuation of renal replacement therapy. This case confirms the occurrence of reversible AKI due to hemophagocytic lymphohistiocytosis-induced activated macrophage infiltration of the renal parenchyma and inflammation.

Novel therapies for FSGS: preclinical and clinical studies

Focal segmental glomerulosclerosis (FSGS) is a rare but important cause of end-stage kidney disease in children and adults. Current therapy, consisting of corticosteroids and calcineurin inhibitors, fails to achieve a sustained remission in most patients. Therefore, there is a pressing need to develop new treatments for this glomerulopathy. Traditional approaches have focused on agents that modulate the immune system. In this review, we summarize preclinical and clinical data with newer agents that may ameliorate FSGS. We focus on drugs that inhibit immune injury or inflammation, such as abatacept, rituximab, adalimumab, and stem cells. The potential of agents that block the glomerular action of circulating permeability factors such as soluble urokinase receptor is reviewed. Finally, because fibrosis represents the final common pathway of glomerular damage in FSGS, the experience with a wide range of antifibrotic agents is presented. Despite extensive research on the podocyte dysfunction in the pathogenesis of FSGS, there are few agents that directly target podocyte structure or viability. We conclude that FSGS is a heterogeneous disorder and that intensified translational research is vital to improve our understanding of distinct subtypes that have a defined prognosis and predictable response to targeted therapeutic interventions.

ADCK4 "reenergizes" nephrotic syndrome

Steroid-resistant nephrotic syndrome has a poor prognosis and often leads to end-stage renal disease development. In this issue of the JCI, Ashraf and colleagues used exome sequencing to identify mutations in the aarF domain containing kinase 4 (ADCK4) gene that cause steroid-resistant nephrotic syndrome. Patients with ADCK4 mutations had lower coenzyme Q10 levels, and coenzyme Q10 supplementation ameliorated renal disease in a patient with this particular mutation, suggesting a potential therapy for patients with steroid-resistant nephrotic syndrome with ADCK4 mutations.

Evidence for HSP-mediated cytoskeletal stabilization in mesothelial cells during acute experimental peritoneal dialysis

Low biocompatibility of peritoneal dialysis fluid (PDF) injures mesothelial cells and activates their stress response. In this study, we investigated the role of heat shock proteins (HSP), the main cytoprotective effectors of the stress response, in cytoskeletal stabilization of mesothelial cells in experimental peritoneal dialysis. In cultured human mesothelial cells, cytoskeletal integrity was assessed by detergent extractability of marker proteins following in vitro PDF exposure. Effects of HSP on stabilization of ezrin were evaluated by a conditioning protocol (PDF pretreatment) and repair assay, based on coincubation of cytoskeletal protein fractions with recombinant HSP-72 or HSP-72 antibodies. In the rat model, detachment of mesothelial cells from their peritoneal monolayer during in vivo PDF exposure was assessed with and without overexpression of HSP-72 (by heat conditioning). In vitro, cytoskeletal disruption on sublethal PDF exposure was demonstrated by significantly altered detergent extractability of ezrin and ZO-1. Restoration was associated with significant induction and cytoskeletal redistribution of HSP during recovery. Both the conditioning protocol and in vitro repair assay provided evidence for HSP-72-mediated cytoskeletal stabilization. In the rat model, overexpression of HSP-72 following heat conditioning resulted in significantly reduced detachment of mesothelial cells on in vivo exposure to PDF. Our results establish an essential role of HSP in repair and cytoprotection of cytoskeletal integrity in mesothelial cells following acute in vitro and in vivo exposure to PDF. Repeated exposure to PDF, as is the rule in the clinical setting, may not only cause repeat injury to mesothelial cells but rather represents a kind of inadvertent conditioning treatment.

Ex vivo reversal of in vivo transdifferentiation in mesothelial cells grown from peritoneal dialysate effluents

BACKGROUND

During peritoneal dialysis (PD), epithelial-mesenchymal transition (EMT) is likely involved in aberrant healing and progressive peritoneal fibrosis. Recently, EMT of the kidney was actively reversed into the opposite direction, into mesenchymal-epithelial transition (MET), by treatment with bone morphogenic protein-7 (BMP-7). In this study, the potential for ex vivo interconversion of in vivo transdifferentiation processes was investigated in mesothelial cells.

METHODS

In vivo EMT was assessed in mesothelial cell cultures randomly grown from peritoneal effluents of seven patients on chronic PD. Then, ex vivo treatment with modulating factors was performed by incubating cobblestone-like cell cultures with transforming growth factor (TGF- beta1) and fibroblast-like cultures with BMP-7. Effects were assessed by morphological characterization, western analysis and reverse transcription-polymerase chain reaction of marker proteins ezrin and alpha-smooth muscle actin (alpha-SMA).

RESULTS

PD caused progressive in vivo EMT with loss of the epithelial phenotype in the majority of mesothelial cell cultures over a 12-month period. EMT was reproducible by ex vivo treatment of cultured cells with TGF-beta1, converting the epithelial to the fibroblast-like phenotype. Ex vivo treatment with BMP-7 reversed in vivo and ex vivo EMT. During rhBMP-7 incubation the fibroblast-like growth pattern reversed into a more epithelial morphology, the expression of ezrin increased and alpha-SMA decreased.

CONCLUSION

Our study shows that modulating factors of transdifferentiation, such as BMP-7, may be attractive tools in the balance between normal healing and aberrant profibrotic processes in mesothelial cells during peritoneal dialysis. Peritoneal-effluent-derived mesothelial cells are not mere biomarkers for in vivo EMT in the peritoneal cavity, but also represent an assay to test ex vivo interventions to reverse the profibrotic phenotype.