Comparison of cystatin C-based estimated glomerular filtration rate with measured glomerular filtration rate in a pediatric cohort of patients with chronic kidney disease.

BACKGROUND: It is essential to have an accurate assessment of the renal function of patients with chronic kidney disease to monitor, treat, and predict further development of the condition. Measurement of renal function in terms of glomerular filtration rate (GFR) requires either urine or blood sampling, but especially in children, more simple methods of measurement are preferable. The main objective of this study was to examine if the estimated GFR (eGFR) calculated with different cystatin-C-based equations was comparable to the GFR measured by a radiotracer (mGFR) in pediatric patients. METHODS: In this retrospective study, 28 pediatric patients contributed with 73 pairs of measurements collected within 5 years. Bland-Altman Limits of Agreement were used to evaluate the performance and accuracy of two different cystatin-C-based estimates, the CKiDCrea-CysC and the CKiDU25 respectively, compared to an mGFR based on plasma clearance of technetium-99m-diethylenetriaminepentaacetic acid or chromium-51-ethylenediaminetetraacetic acid. RESULTS: Using the CKiDCrea-CysC equation, 58.9% of the datasets were within P10 and 87.7% were within P30. The mean difference was 4.8 mL/min/1.73m2 (standard deviation: 8.5 mL/min/1.73m2) and tended to overestimate GFR and thereby overrate the kidney function within the entire GFR range. Using the CKiDU25 equation, 53.4% were within P10 and 93.2% within P30. The mean difference was -2.9 mL/min/1.73m2 (standard deviation: 8.4 mL/min/1.73m2), but the difference varied with the GFR value. CONCLUSIONS: A cystatin-C-based eGFR provides a viable substitute for monitoring renal function in pediatric patients with chronic kidney disease. However, it has a lower accuracy than mGFR and can therefore not replace mGFR in clinical use.

Successful low-dose immunotherapy after kidney transplantation in a 10-year-old girl with Schimke immuno-osseous dysplasia.

BACKGROUND: This case report highlights a successful steroid-free, low-dose immunosuppressive protocol for renal transplantation in a pediatric patient with Schimke immuno-osseous dysplasia with excellent 7-year patient and graft survival. Schimke immuno-osseous dysplasia is a rare multisystem disorder involving the kidney. Renal transplantation is a therapeutic option, but posttransplant mortality is high due to severe infections and posttransplant lymphoproliferative disease. METHODS: A 10-year-old girl diagnosed with Schimke immuno-osseous dysplasia and end-stage renal disease underwent an AB0-compatible living-related kidney transplantation, with no donor-specific antibodies. Our standard immunosuppression protocol was modified due to the risk of infection. Basiliximab was used as induction therapy, and a reduced dose of mycophenolate mofetil and tacrolimus was initiated following transplantation, maintaining the patient on a low tacrolimus target (3-5 µg/L). Mycophenolate mofetil was discontinued after 8 weeks due to neutropenia and the patient was kept on tacrolimus as monotherapy. Five years posttransplant the patient developed acute onset of neurological symptoms, consisting of ataxia, lack of voluntary coordination, balance, aphasia and dysphagia, and diplopia. She recovered without neurological deficits within 6 weeks. Extensive evaluation revealed no pathology. To avoid a possible a component of tacrolimus-induced cerebral vasoconstriction, the immunosuppressive therapy was changed to everolimus. RESULTS: Seven years posttransplant, the patient has experienced no serious infections, no rejections, and had excellent graft function, and no de novo donor-specific antibodies. CONCLUSIONS: The present results indicate that low-dose immunosuppressive therapy after renal transplantation with low immunological risk should be considered for patients with Schimke immuno-osseous dysplasia.

Detection of DZIP1L mutations by whole-exome sequencing in consanguineous families with polycystic kidney disease.

BACKGROUND: Autosomal recessive polycystic kidney disease is a cystic kidney disease with early onset and clinically characterized by enlarged echogenic kidneys, hypertension, varying degrees of kidney dysfunction, and liver fibrosis. It is most frequently caused by sequence variants in the PKHD1 gene, encoding fibrocystin. In more rare cases, sequence variants in DZIP1L are seen, encoding the basal body protein DAZ interacting protein 1-like protein (DZIP1L). So far, only four different DZIP1L variants have been reported. METHODS: Four children from three consanguineous families presenting with polycystic kidney disease were selected for targeted or untargeted exome sequencing. RESULTS: We identified two different, previously not reported homozygous DZIP1L sequence variants: c.193 T > C; p.(Cys65Arg), and c.216C > G; p.(Cys72Trp). Functional analyses of the c.216C > G; p.(Cys72Trp) variant indicated mislocalization of mutant DZIP1L. CONCLUSIONS: In line with published data, our results suggest a critical role of the N-terminal domain for proper protein function. Although patients with PKHD1-associated autosomal recessive polycystic kidney disease often have liver abnormalities, none of the present four patients showed any clinically relevant liver involvement. Our data demonstrate the power and efficiency of next-generation sequencing-based approaches. While DZIP1L-related polycystic kidney disease certainly represents a rare form of the disease, our results emphasize the importance of including DZIP1L in multigene panels and in the data analysis of whole-exome sequencing for cystic kidney diseases. A higher resolution version of the Graphical abstract is available as Supplementary information.

Mineralocorticoid receptor blockade with spironolactone has no direct effect on plasma IL-17A and injury markers in urine from kidney transplant patients.

Kidney transplantation is associated with increased risk of cardiovascular morbidity. Interleukin (IL)-17A mediates kidney injury. Aldosterone promotes T helper 17 lymphocyte differentiation and IL-17A production through the mineralocorticoid receptor. In this exploratory, post hoc substudy, it was hypothesized that a 1-yr intervention with the mineralocorticoid receptor antagonist spironolactone lowers IL-17A and related cytokines and reduces epithelial injury in kidney transplant recipients. Plasma and urine samples were obtained from kidney transplant recipients from a double-blind randomized clinical trial testing spironolactone (n = 39) versus placebo (n = 41). Plasma concentrations of cytokines interferon-γ, IL-17A, tumor necrosis factor-α, IL-6, IL-1ß, and IL-10 were determined before and after 1-yr treatment. Urine calbindin-to-creatinine, clusterin-to-creatinine, kidney injury molecule-1-to-creatinine, osteoactivin-to-creatinine, trefoil factor 3 (TFF3)-to-creatinine, and VEGF-to-creatinine ratios were analyzed. Blood pressure and plasma aldosterone concentration at inclusion did not relate to plasma cytokines and injury markers expect for urine TFF3-to-creatinine ratios that correlated positively to blood pressure. None of the cytokines changed in plasma after spironolactone intervention. Plasma IL-17A increased in the placebo-treated group. Spironolactone induced an increase in plasma K+ (0.4 ± 0.4 mmol/L). This increase did not correlate with plasma IL-17A or urine calbindin and TFF3 changes. Ongoing treatment at inclusion with angiotensin-converting enzyme inhibitor and/or ANG II receptor blockers was not associated with changed levels of IL-17A and injury markers and had no effect on the response to spironolactone. Urinary calbindin and TFF3 decreased in the spironolactone-treated group with no difference in between-group analyses. In conclusion, irrespective of ongoing ANG II inhibition, spironolactone has no effect on plasma IL-17A and related cytokines or urinary injury markers in kidney transplant recipients.NEW & NOTEWORTHY The mineralocorticoid receptor antagonist spironolactone had no direct anti-inflammatory effects on prohypertensive interleukin-17A or distal nephron epithelial injury markers in kidney transplant recipients.

Proteomic Analysis of Renal Biomarkers of Kidney Allograft Fibrosis-A Study in Renal Transplant Patients.

Renal transplantation is the preferred treatment of end stage renal disease, but allograft survival is limited by the development of interstitial fibrosis and tubular atrophy in response to various stimuli. Much effort has been put into identifying new protein markers of fibrosis to support the diagnosis. In the present work, we performed an in-depth quantitative proteomics analysis of allograft biopsies from 31 prevalent renal transplant patients and correlated the quantified proteins with the volume fraction of fibrosis as determined by a morphometric method. Linear regression analysis identified four proteins that were highly associated with the degree of interstitial fibrosis, namely Coagulation Factor XIII A chain (estimate 18.7, adjusted p < 0.03), Uridine Phosphorylase 1 (estimate 19.4, adjusted p < 0.001), Actin-related protein 2/3 subunit 2 (estimate 34.2, adjusted p < 0.05) and Cytochrome C Oxidase Assembly Factor 6 homolog (estimate -44.9, adjusted p < 0.002), even after multiple testing. Proteins that were negatively associated with fibrosis (p < 0.005) were primarily related to normal metabolic processes and respiration, whereas proteins that were positively associated with fibrosis (p < 0.005) were involved in catabolic processes, cytoskeleton organization and the immune response. The identified proteins may be candidates for further validation with regards to renal fibrosis. The results support the notion that cytoskeleton organization and immune responses are prevalent processes in renal allograft fibrosis.

Identification of differential gene expression patterns in human arteries from patients with chronic kidney disease.

Uremia accelerates atherosclerosis, but little is known about affected pathways in human vasculature. This study aimed to identify differentially expressed arterial transcripts in patients with chronic kidney disease (CKD). Global mRNA expression was estimated by microarray hybridization in iliac arteries ( n = 14) from renal transplant recipients and compared with renal arteries from healthy living kidney donors ( n = 19) in study 1. Study 2 compared nonatherosclerotic internal mammary arteries (IMA) from five patients with elevated plasma creatinine levels and age- and sex-matched controls with normal creatinine levels. Western blotting and immunohistochemistry for selected proteins were performed on a subset of study 1 samples. Fifteen gene transcripts were significantly different between the two groups in study 1 [fold changes (FC) > 1.05 and false discovery rates (FDR) < 0.005]. Most upregulated mRNAs associated with cellular signaling, apoptosis, TNFα/NF-κB signaling, smooth muscle contraction, and 10 other pathways were significantly affected. To focus attention on genes from genuine vascular cells, which dominate in IMA, concordant deregulated genes in studies 1 and 2 were examined and included 23 downregulated and eight upregulated transcripts (settings in study 1: FC > 1.05 and FDR < 0.05; study 2: FC > 1.2 and P < 0.2). Selected deregulated gene products were investigated at the protein level, and whereas HIF3α confirmed mRNA upregulation, vimentin showed upregulation in contrast to the mRNA results. We conclude that arteries from CKD patients display change in relatively few sets of genes. Many were related to differentiated vascular smooth muscle cell phenotype. These identified genes may contribute to understanding the development of arterial injury among patients with CKD.

Does Mineralocorticoid Receptor Antagonism Prevent Calcineurin Inhibitor-Induced Nephrotoxicity?

Calcineurin inhibitors have markedly reduced acute rejection rates in renal transplantation, thus significantly improved short-term outcome. The beneficial effects are, however, tampered by acute and chronic nephrotoxicity leading to interstitial fibrosis and tubular atrophy, which impairs long-term allograft survival. The mineralocorticoid hormone aldosterone induces fibrosis in numerous organs, including the kidney. Evidence from animal models suggests a beneficial effect of aldosterone antagonism in reducing calcineurin inhibitor-induced nephrotoxicity. This review summarizes current evidence of mineralocorticoid receptor antagonism in animal models of calcineurin inhibitor-induced nephrotoxicity and the results from studies of mineralocorticoid antagonism in renal transplant patients.

The Pharmacogenetics of Tacrolimus in Corticosteroid-Sparse Pediatric and Adult Kidney Transplant Recipients.

INTRODUCTION: Tacrolimus is a calcineurin inhibitor used as an immunosuppressant drug in solid organ transplantation, and is mainly metabolized by cytochrome P450 (CYP) 3A4 and CYP3A5. Studies have shown an association between the CYP3A5 genotype and tacrolimus dose-adjusted trough concentrations. Variants in the genes PPARA, POR and CYP3A4 have recently been shown to influence tacrolimus metabolism. Furthermore, pharmacokinetic interaction between corticosteroid treatment and tacrolimus has been shown. In the present study, we investigated a potential association between CYP3A5*3, PPARA c.209-1003G>A, POR*28 and CYP3A4*22 and dose-adjusted tacrolimus trough concentrations in a primarily corticosteroid-free (>85%) population of Danish pediatric and adult kidney transplant recipients. METHODS: Seventy-two patients receiving treatment with oral tacrolimus were genotyped using real-time polymerase chain reaction and Primer-Probe Detection. Tacrolimus trough concentrations, corresponding doses and covariates were retrospectively collected from the patients' medical charts. RESULTS: It was confirmed that CYP3A5*1 wild-type carriers had lower median dose-adjusted tacrolimus trough concentrations compared with noncarriers. Adults had 56 and 77% lower trough concentrations at 6 weeks (p = 0.0003) and 1 year, respectively (p < 0.0017), and, similarly, children had 65 and 39% lower median concentrations, with p values of 0.006 and 0.011, respectively. No association was found for PPARA c.209-1003G>A, POR*28, or CYP3A4*22. An association between the PPARA c.209-1003G>A genotype and an increased number of infections with cytomegalovirus (CMV) within the first year was identified (p < 0.05). Only 29% of trough concentrations measured between 2 and 12 weeks post-transplantation were on target. CONCLUSION: This study shows that the known association of the CYP3A5 genotype with tacrolimus dose-adjusted trough concentrations has the same impact in a corticosteroid-sparse population. The association between PPARA variance and infections with CMV will need further investigation.

Cancer risk and mortality after kidney transplantation: a population-based study on differences between Danish centres using standard immunosuppression with and without glucocorticoids.

BACKGROUND: Kidney recipients receive immunosuppression to prevent graft rejection, and long-term outcomes such as post-transplant cancer and mortality may vary according to the different protocols of immunosuppression. METHODS: A national register-based historical cohort study was conducted to examine whether post-transplant cancer and all-cause mortality differed between Danish renal transplantation centres using standard immunosuppressive protocols including steroids (Centres 2, 3, 4) or a steroid-free protocol (Centre 1). The Danish Nephrology Registry, the Danish Civil Registration System, the Danish National Cancer Registry and the Danish National Patient Register were used. A historical cohort of 1450 kidney recipients transplanted in 1995-2005 was followed up with respect to post-transplant cancer and death until 31 December 2011. RESULTS: Compared with Center 1 the adjusted post-transplant cancer risk was 6-39% lower in Centre 3 [hazard ratio (HR) 0.94, 95% confidence interval (CI) 0.67-1.32], in Centre 2 (HR 0.72, 95% CI 0.52-0.98) and in Centre 4 (HR 0.61, 95% CI 0.44-0.83). Compared with Center 1, the adjusted post-transplant mortality was 21-55% higher in Centre 4 (HR 1.21, 95% CI 0.91-1.61), in Centre 3 (HR 1.35, 95% CI 0.98-1.86) and in Centre 2 (HR 1.55, 95% CI 1.17-2.05). On average, post-transplant cancer was associated with a 4-fold increase in the risk of death (HR 4.25, 95% CI 3.36-5.38). CONCLUSIONS: There was a tendency of a higher post-transplant cancer occurrence, but lower all-cause mortality, in the Danish transplantation centre that adhered to a standard steroid-free immunosuppressive protocol.

Post-transplant lymphoproliferative disorder following kidney transplantation: a population-based cohort study.

Post-transplant lymphoproliferative disorder (PTLD) incidence is difficult to determine, mainly because both early and other lesions may go unrecognized and unregistered. Few studies have included systematic pathology review to maximize case identification and decide more accurately PTLD frequency after long-term post-transplantation follow-up. A retrospective population-based cohort study including all kidney transplant recipients at two Danish centres (1990-2011; population covered 3.1 million; 2175 transplantations in 1906 patients). Pathology reports were reviewed for all patient biopsies to identify possible PTLDs. Candidate PTLDs underwent histopathological review and classification. Seventy PTLD cases were identified in 2175 transplantations (3.2%). The incidence rate (IR) after first transplantation was 5.4 cases per 1000 patient-years (95% CI: 4.0-7.3). Most PTLDs were monomorphic (58.5%), or early lesions (21.5%). Excluding early lesions and patients <18 years, IR was 3.7 (95% CI: 2.9-5.5). Ten patients with PTLD were retransplanted, 2 developing further PTLDs. Post-transplant patient survival was inferior in patients with PTLD, while death-censored graft survival was not. Using registry data together with extensive pathological review and long follow-up, a rather high incidence of PTLD was found.

The role of glucocorticoids in sodium retention in cirrhotic patients: a double blind, randomized, crossover study.

OBJECTIVE: Cirrhotic patients have an increased ratio of urinary cortisol to cortisone metabolites, indicating decreased renal 11-ß-hydroxysteroid dehydrogenase type-2 activity. This suggests that cortisol--by activation of the mineralocorticoid receptor--may contribute to the abnormal sodium retention evident in cirrhosis. The aim was to elucidate the role of glucocorticoids in sodium retention in decompensated cirrhotic patients. METHODS: A randomized, double-blind, placebo-controlled, crossover study was performed in nine patients with alcoholic cirrhosis of the liver. A washout interval of 14 days separated the two periods. After a basal period of 36 h, dexamethasone (0.5 mg every 6 h) or placebo was given for two days. Urine was collected for 12 h periods, and the concentrations of sodium, potassium, creatinine, cortisol and cortisol metabolites were determined. Blood samples for hemoglobin, glucose, sodium, potassium, creatinine, aldosterone and cortisol were obtained daily. RESULTS: Dexamethasone treatment decreased S-cortisol 92.3% (82.9-93.4%) (median and range) compared with that in the basal period. Natriuresis (dexamethasone--placebo) increased 55.1 (-26.4-168.7) mmol/day (median and range). No statistically significant differences (dexamethasone--placebo) were found in changes in body weight (0.00 (-0.45-2.20) kg/day), diuresis (0.56 (-0.35-1.43) L/day) or mean arterial pressure (8.33 (-16.0-41.3) mmHg) (median and range) in reference to the preceding 24 h basal period. CONCLUSION: These results indicate that endogenous glucocorticoids contribute to the sodium retention in patients with alcoholic cirrhosis of the liver.

Vitamin D status in children and adolescents with kidney transplants.

Hypovitaminosis D is highly prevalent in adult kidney-transplanted patients. The knowledge of vitamin D status in kidney-transplanted children and adolescents is sparse. The present study investigated the vitamin D status of a cohort of kidney-transplanted children and adolescents, and the association between vitamin D status and plasma concentrations of PTH, ionized calcium, and phosphate. The study included 35 patients with a functioning graft. Their mean age was 12.0 yr, and the mean graft age was 2.8 yr. Forty percent of the patients were vitamin D insufficient (P-25-hydroxyvitamin D 40-75 nm), and 14% were deficient (P-25-hydroxyvitamin D < 40 nm). S-25-hydroxyvitamin D was inversely associated with PTH (p = 0.02) and positively associated with S-1,25-dihydroxyvitamin D (p = 0.02). There was no significant association between S-1,25-dihydroxyvitamin D and PTH. In conclusion, we found hypovitaminosis D in 54% of the study population despite the fact that samples were collected in spring and summer months. Hypovitaminosis D was associated with adverse effects on PTH and 1,25-dihydroxyvitamin D. Our data suggest that it is warranted to monitor vitamin D status of kidney-transplanted children and adolescents and indicate that correction of hypovitaminosis D might have favorable effects on calcium-phosphate metabolism.