David C.H. Harris

A randomized, controlled trial of early versus late initiation of dialysis

BACKGROUND In clinical practice, there is considerable variation in the timing of the initiation of maintenance dialysis for patients with stage V chronic kidney disease, with a worldwide trend toward early initiation. In this study, conducted at 32 centers in Australia and New Zealand, we examined whether the timing of the initiation of maintenance dialysis influenced survival among patients with chronic kidney disease. METHODS We randomly assigned patients 18 years of age or older with progressive chronic kidney disease and an estimated glomerular filtration rate (GFR) between 10.0 and 15.0 ml per minute per 1.73 m2 of body-surface area (calculated with the use of the Cockcroft-Gault equation) to planned initiation of dialysis when the estimated GFR was 10.0 to 14.0 ml per minute (early start) or when the estimated GFR was 5.0 to 7.0 ml per minute (late start). The primary outcome was death from any cause. RESULTS Between July 2000 and November 2008, a total of 828 adults (mean age, 60.4 years; 542 men and 286 women; 355 with diabetes) underwent randomization, with a median time to the initiation of dialysis of 1.80 months (95% confidence interval [CI], 1.60 to 2.23) in the early-start group and 7.40 months (95% CI, 6.23 to 8.27) in the late-start group. A total of 75.9% of the patients in the late-start group initiated dialysis when the estimated GFR was above the target of 7.0 ml per minute, owing to the development of symptoms. During a median follow-up period of 3.59 years, 152 of 404 patients in the early-start group (37.6%) and 155 of 424 in the late-start group (36.6%) died (hazard ratio with early initiation, 1.04; 95% CI, 0.83 to 1.30; P=0.75). There was no significant difference between the groups in the frequency of adverse events (cardiovascular events, infections, or complications of dialysis). CONCLUSIONS In this study, planned early initiation of dialysis in patients with stage V chronic kidney disease was not associated with an improvement in survival or clinical outcomes. (Funded by the National Health and Medical Research Council of Australia and others; Australian New Zealand Clinical Trials Registry number, 12609000266268.)

Effects of Early and Late Intervention with Epoetin α on Left Ventricular Mass among Patients with Chronic Kidney Disease (Stage 3 or 4): Results of a Randomized Clinical Trial

It is not known whether prevention of anemia among patients with chronic kidney disease would affect the development or progression of left ventricular (LV) hypertrophy. A randomized controlled trial was performed with 155 patients with chronic kidney disease (creatinine clearance, 15 to 50 ml/min), with entry hemoglobin concentrations ([Hb]) of 110 to 120 g/L (female patients) or 110 to 130 g/L (male patients). Patients were monitored for 2 yr or until they required dialysis; the patients were randomized to receive epoetin alpha as necessary to maintain [Hb] between 120 and 130 g/L (group A) or between 90 and 100 g/L (group B). [Hb] increased for group A (from 112 +/- 9 to 121 +/- 14 g/L, mean +/- SD) and decreased for group B (from 112 +/- 8 to 108 +/- 13 g/L) (P < 0.001, group A versus group B). On an intent-to-treat analysis, the changes in LV mass index for the groups during the 2-yr period were not significantly different (2.5 +/- 20 g/m(2) for group A versus 4.5 +/- 20 g/m(2) for group B, P = NS). There was no significant difference between the groups in 2-yr mean unadjusted systolic BP (141 +/- 14 versus 138 +/- 13 mmHg) or diastolic BP (80 +/- 6 versus 79 +/- 7 mmHg). The decline in renal function in 2 yr, as assessed with nuclear estimations of GFR, also did not differ significantly between the groups (8 +/- 9 versus 6 +/- 8 ml/min per 1.73 m(2)). In conclusion, maintenance of [Hb] above 120 g/L, compared with 90 to 100 g/L, had similar effects on the LV mass index and did not clearly affect the development or progression of LV hypertrophy. The maintenance of [Hb] above 100 g/L for many patients in group B might have been attributable to the relative preservation of renal function.

Adriamycin nephropathy: A model of focal segmental glomerulosclerosis

Adriamycin nephropathy (AN) is a rodent model of chronic kidney disease that has been studied extensively and has enabled a greater understanding of the processes underlying the progression of chronic proteinuric renal disease. AN is characterized by podocyte injury followed by glomerulosclerosis, tubulointerstitial inflammation and fibrosis. Genetic studies have demonstrated a number of loci that alter both risk and severity of renal injury induced by Adriamycin. Adriamycin‐induced renal injury has been shown in numerous studies to be modulated by both non‐immune and immune factors, and has facilitated further study of mechanisms of tubulointerstitial injury. This review will outline the pharmacological behaviour of Adriamycin, and describe in detail the model of AN, including its key structural characteristics, genetic susceptibility and pathogenesis.

Disruption of E-Cadherin by Matrix Metalloproteinase Directly Mediates Epithelial-Mesenchymal Transition Downstream of Transforming Growth Factor-β1 in Renal Tubular Epithelial Cells

Epithelial-mesenchymal transition (EMT) plays an important role in organ fibrosis, including that of the kidney. Loss of E-cadherin expression is a hallmark of EMT; however, whether the loss of E-cadherin is a consequence or a cause of EMT remains unknown, especially in the renal system. In this study, we show that transforming growth factor (TGF)-beta1-induced EMT in renal tubular epithelial cells is dependent on proteolysis. Matrix metalloproteinase-mediated E-cadherin disruption led directly to tubular epithelial cell EMT via Slug. TGF-beta1 induced the proteolytic shedding of E-cadherin, which caused the nuclear translocation of beta-catenin, the transcriptional induction of Slug, and the repression of E-cadherin transcription in tubular epithelial cells. These findings reveal a direct role for E-cadherin and for matrix metalloproteinases in causing EMT downstream of TGF-beta1 in fibrotic disease. Specific inhibition rather than activation of matrix metalloproteinases may offer a novel approach for treatment of fibrotic disease.

Macrophages in Renal Disease

Macrophages have heterogeneous phenotypes as they exercise their twofold role in the development and recovery of renal diseases. Some subpopulations of macrophages (M1) have a pathogenic function in renal inflammation, making them a logical target for elimination. Alternatively, M2 macrophage subpopulations resolve inflammation and repair injury, making them a potential therapeutic tool against renal injury. Here, we summarize recent findings regarding macrophage plasticity, and the various strategies for targeting or utilizing macrophages to treat renal disease. We highlight, in particular, the potential of renoprotective M2 macrophages to resolve inflammation and repair the kidney.

E-Cadherin/β-Catenin Complex and the Epithelial Barrier

E-Cadherin/β-catenin complex plays an important role in maintaining epithelial integrity and disrupting this complex affect not only the adhesive repertoire of a cell, but also the Wnt-signaling pathway. Aberrant expression of the complex is associated with a wide variety of human malignancies and disorders of fibrosis resulting from epithelial-mesenchymal transition. These associations provide insights into the complexity that is likely responsible for the fibrosis/tumor suppressive action of E-cadherin/β-catenin.

IL-10/TGF-beta-modified macrophages induce regulatory T cells and protect against adriamycin nephrosis.

IL-10/TGF-beta-modified macrophages, a subset of activated macrophages, produce anti-inflammatory cytokines, suggesting that they may protect against inflammation-mediated injury. Here, macrophages modified ex vivo by IL-10/TGF-beta (IL-10/TGF-beta Mu2) significantly attenuated renal inflammation, structural injury, and functional decline in murine adriamycin nephrosis (AN). These cells deactivated effector macrophages and inhibited CD4+ T cell proliferation. IL-10/TGF-beta Mu2 expressed high levels of the regulatory co-stimulatory molecule B7-H4, induced regulatory T cells from CD4+CD25- T cells in vitro, and increased the number of regulatory T cells in lymph nodes draining the kidneys in AN. The phenotype of IL-10/TGF-beta Mu2 did not switch to that of effector macrophages in the inflamed kidney, and these cells did not promote fibrosis. Taken together, these data demonstrate that IL-10/TGF-beta-modified macrophages effectively protect against renal injury in AN and may become part of a therapeutic strategy for chronic inflammatory disease.

CD4+CD25+ Regulatory T Cells Protect against Injury in an Innate Murine Model of Chronic Kidney Disease

Studies of mechanisms of disease regulation by CD4+CD25+ regulatory T cells (Treg) have been focused on their interaction with effector T cells; however, the possibility that regulation might involve noncognate cells has not been explored in detail. This study investigated the effect of CD4+CD25+ Treg on macrophage proinflammatory properties and phenotype in vitro and found that they modulate macrophages by inhibiting their activation, leading to reduced proinflammatory cytokine production and a downregulated effector phenotype. For testing the in vivo significance of this effect, CD4+CD25+ T cells that expressed high levels of Foxp3 were reconstituted into SCID mice after induction of Adriamycin nephropathy, a noncognate model of chronic renal disease. CD4+CD25+ T cells significantly reduced glomerular and interstitial injury. In addition, there was a significant fall in the number of macrophages in both the glomeruli and interstitium of SCID mice that were reconstituted with Treg as compared with the Adriamycin alone group. Blockade of TGF-beta using neutralizing antibodies significantly impaired the protective effect of Treg. These findings delineate a TGF-beta-dependent Treg-macrophage inhibitory interaction that can explain cognate-independent protection by Treg.

Effects of uric acid-lowering therapy on renal outcomes: a systematic review and meta-analysis.

BACKGROUND Non-randomized studies suggest an association between serum uric acid levels and progression of chronic kidney disease (CKD). The aim of this systematic review is to summarize evidence from randomized controlled trials (RCTs) concerning the benefits and risks of uric acid-lowering therapy on renal outcomes. METHODS Medline, Excerpta Medical Database and Cochrane Central Register of Controlled Trials were searched with English language restriction for RCTs comparing the effect of uric acid-lowering therapy with placebo/no treatment on renal outcomes. Treatment effects were summarized using random-effects meta-analysis. RESULTS Eight trials (476 participants) evaluating allopurinol treatment were eligible for inclusion. There was substantial heterogeneity in baseline kidney function, cause of CKD and duration of follow-up across these studies. In five trials, there was no significant difference in change in glomerular filtration rate from baseline between the allopurinol and control arms [mean difference (MD) 3.1 mL/min/1.73 m2, 95% confidence intervals (CI) -0.9, 7.1; heterogeneity χ2=1.9, I2=0%, P=0.75]. In three trials, allopurinol treatment abrogated increases in serum creatinine from baseline (MD -0.4 mg/dL, 95% CI -0.8, -0.0 mg/dL; heterogeneity χ2=3, I2=34%, P=0.22). Allopurinol had no effect on proteinuria and blood pressure. Data for effects of allopurinol therapy on progression to end-stage kidney disease and death were scant. Allopurinol had uncertain effects on the risks of adverse events. CONCLUSIONS Uric acid-lowering therapy with allopurinol may retard the progression of CKD. However, adequately powered randomized trials are required to evaluate the benefits and risks of uric acid-lowering therapy in CKD.

Iron Accumulation in Human Chronic Renal Disease

Iron, which has been shown to accumulate within proximal tubule lysosomes in proteinuric models of renal disease, may play a role in the progression of chronic renal disease by the generation of reactive oxygen species. Therefore, renal biopsies from humans with proteinuria and/or chronic renal failure were examined at an ultrastructural level for iron by energy dispersive analysis and compared with normal biopsies. Iron accumulated in proximal tubular lysosomes in renal disease (P < 0.05 v normals), accompanied in some cases by phosphorus and silicon. Both the number of iron-containing lysosomes per tubular cross-section (1.86 +/- 0.41 v 0.66 +/- 0.22, P < 0.05) and the mean concentration of lysosomal iron (254.5 +/- 73.4 mg/dL v 81.2 +/- 23.8, P < 0.001) was greater in patients with nephrotic syndrome (n = 12) than in those without (n = 8). Iron accumulation (number of iron-containing lysosomes/tubule) correlated with protein excretion (r = 0.68, P = 0.003, n = 20), but not with glomerular filtration rate. Damaged tubules contained greater amounts of iron than tubules with less damage (288.5 +/- 68.5 mg/dL v 80.4 +/- 13.9, P < 0.01). Further studies are needed to define the possible role of iron in causing tubular damage and progression of renal disease.