Vitronectin dictates intraglomerular fibrinolysis in immune-mediated glomerulonephritis

During human glomerulonephritis, the severity of injuries correlates with glomerular fibrin deposits, which are tightly regulated by the intraglomerular fibrinolytic system. Here, we evaluated the role of vitronectin (VTN; also known as complement S protein), the principal cofactor of the plasminogen activator inhibitor-1 (PAI-1), in a mouse model of acute glomerulonephritis. We found that in mice subjected to nephrotoxic serum, the absence of VTN resulted in a lower glomerular PAI-1 activity and a higher glomerular fibrinolytic activity. Challenged VTN(-/-) mice displayed significantly less fibrin deposits, proteinuria, and renal failure than their wild-type counterparts. Notably, this protective effect afforded by VTN deficiency was still observed after a C3 depletion. Finally, the injection of VTN(+/+) serum in VTN(-/-) mice induced the glomerular deposition of VTN, increased PAI-1 deposition, decreased glomerular fibrinolytic activity, and aggravated glomerular injury. As in mice, abundant glomerular VTN deposits were also observed in patients with severe glomerulonephritis. Here, we show that plasma-exchange therapy, admittedly beneficial in this clinical context, induces a significant depletion in circulating VTN, which might modulate PAI-1 activity locally and accelerate the clearance of fibrin deposits in the glomeruli. Collectively, these results demonstrate that VTN exerts a deleterious role independently from complement, by directing PAI-dependent fibrinolysis in the glomerular compartment.

[Epithelial-mesenchymal transition in kidney grafts]

Late loss of renal grafts is primarily due to progressive sclerosis, involving both immune and non immune processes. Activation of interstitial fibroblasts responsible for graft fibrosis is known to involve proliferation and activation of resident fibroblasts, recruitment of bone marrow-derived stem cells, and epithelial-mesenchymal transition, a more recently identifled mechanism. In this latter process, tubular epithelial cells lose their epithelial phenotype, acquire mesenchymal markers and properties, and participate in the fibrotic process. Whether or not these cells move into the interstitium is controversial. By using immunohistochemistry with specific antibodies against vimentin, beta cadherin, beta catenin and other fibroblastic markers, we found that tubular epithelial cells in kidney grafts can exhibit phenotypic markers of epithelial-mesenchymal transition as early as 3 months after transplantation, before the onset of fibrosis. These changes are associated with prolonged cold ischemia and clinical or subclinical acute rejection. In addition, changes observed at 3 months seem to be predictive of both the fibrosis score at 12 months and, interestingly, the progression of fibrosis between 3 months and 12 months. Finally, renal function at 2 years was significantly poorer in patients exhibiting epithelial changes at 3 months. These results suggest that the epithelial-mesenchymal transition plays a role in the progressive fibrosis of kidney grafts, and that its early inhibition could prevent the gradual decline in renal function and late graft loss.

Incidence, risk factors and clinical consequences of neutropenia following kidney transplantation: a retrospective study

Neutropenic episodes in kidney transplant patients are poorly characterized. In this retrospective study, neutropenia was experienced by 112/395 patients (28%) during the first year posttransplant. The only factor found to be significantly associated with the occurrence of neutropenia was combined tacrolimus-mycophenolate therapy (p < 0.001). Neutropenic patients experienced more bacterial infections (43% vs. 32%, p = 0.04). Grade of neutropenia correlated with the global risk of infection. Discontinuation of mycophenolic acid (MPA) due to neutropenia was associated with an increased incidence of acute rejection (odds ratios per day 1.11, 95% confidence intervals 1.02-1.22) but not with reduced renal function at 1 year. The time from onset of neutropenia to MPA discontinuation correlated with the duration of neutropenia. Granulocyte colony-stimulating factor (G-CSF) administration was safe and effective in severely neutropenic kidney graft recipients, with absolute neutrophil count >1000/microL achieved in a mean of 1.5+/-0.5 days. Neutropenia is an important and frequent laboratory finding that may exert a significant influence on outcomes in kidney transplantation. As well as leading to an increased incidence of infection, it is associated with a higher rate of allograft rejection if MPA is discontinued for >6 days (p = 0.02). G-CSF accelerates recovery of neutropenia and may be a good therapeutic alternative for severely neutropenic patients.

Cyst infections in patients with autosomal dominant polycystic kidney disease

BACKGROUND AND OBJECTIVES

Cyst infection is a complex diagnostic and therapeutic issue in patients with autosomal dominant polycystic kidney disease (ADPKD); however, published data regarding the diagnosis and the management of cyst infections in patients with ADPKD are sparse.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A retrospective study was conducted in a referral center for patients with ADPKD in Paris, France. We identified using a computerized database all patients who had ADPKD and were admitted in the nephrology department of Hôpital Necker between January 1998 and August 2008 with likely or definite renal and/or hepatic cyst infection. Medical files of all included patients were reviewed.

RESULTS

Among 389 identified patients with ADPKD, 33 (8.4%) had 41 episodes of cyst infection, including eight definite and 33 likely cases. The incidence of cyst infections in patients with ADPKD was 0.01 episode per patient per year. Microbiological documentation was available for 31 episodes (75%), Escherichia coli accounting for 74% of all retrieved bacterial strains. Positron emission tomography scan proved superior to ultrasound, Computed tomography scan, and magnetic resonance imaging for the detection of infected cysts. Clinical efficacy of initial antibiotic treatment was noted in 71% of episodes. Antibiotic treatment modification was more frequently required for patients who were receiving initial monotherapy compared with those who were receiving bitherapy. Large (diameter >5 cm) infected cysts frequently required drainage.

CONCLUSIONS

Positron emission tomography scan will probably make the diagnosis of cyst infections easier and more accurate. Antibiotic association, including a fluoroquinolone, and the drainage of large infected cysts remain the main treatment for cyst infections.

Invariant natural killer T cells and TGF-beta attenuate anti-GBM glomerulonephritis

Invariant natural killer T (iNKT) cells represent a particular subset of T lymphocytes capable of producing several cytokines, which exert regulatory or effector functions, following stimulation of the T cell receptor. In this study, we investigated the influence of iNKT cells on the development of experimental anti-glomerular basement membrane glomerulonephritis (anti-GBM GN). After injection of anti-GBM serum, the number of kidney iNKT cells rapidly increased. iNKT cell-deficient mice (Jalpha18-/-) injected with anti-GBM serum demonstrated worse renal function, increased proteinuria, and greater glomerular and tubular injury compared with similarly treated wild-type mice. We did not detect significant differences in Th1/Th2 polarization in renal tissue that might have explained the severity of disease in Jalpha18-/- mice. Interestingly, expression of both TGF-beta and TGF-beta-induced (TGFBI) mRNA was higher in wild-type kidneys compared with Jalpha18-/- kidneys, suggesting a possible protective role for TGF-beta in anti-GBM GN. Administration of an anti-TGF-beta neutralizing antibody significantly enhanced the severity of disease in wild-type, but not Jalpha18-/-, mice. In conclusion, in experimental anti-GBM GN, iNKT cells attenuate disease severity and TGF-beta has a renoprotective role.

Hyperemesis gravidarum: une cause rare d'encéphalopathie de Wernicke

INTRODUCTION

Wernicke encephalopathy - most often observed in alcoholic patients - is due to severe thiamine deficiency.

CASE

We report here the case of a 30-year-old woman who presented with hyperemesis and vomiting during the first trimester of pregnancy (hyperemesis gravidarum). Hyperemesis can lead to severe, symptomatic thiamine deficiency and to severe dehydration with prerenal azotemia.

DISCUSSION

Wernicke encephalopathy is a rare complication of hyperemesis gravidarum. It should be diagnosed as early as possible to prevent long-term complications.