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Progressive renal diseases are associated with rarefaction of peritubular capillaries, but the ultrastructural and functional alterations of the microvasculature are not well described. To study this, we analyzed different time points during progressive kidney damage and fibrosis in 3 murine models of different disease etiologies. These models were unilateral ureteral obstruction, unilateral ischemia-reperfusion injury, and Col4a3 -deficient mice, we analyzed ultrastructural alterations in patient biopsy specimens. Compared with kidneys of healthy mice, we found a significant and progressive reduction of peritubular capillaries in all models analyzed. Ultrastructurally, compared with the kidneys of control mice, focal widening of the subendothelial space and higher numbers of endothelial vacuoles and caveolae were found in fibrotic kidneys. Quantitative analysis showed that peritubular capillary endothelial cells in fibrotic kidneys had significantly and progressively reduced numbers of fenestrations and increased thickness of the cell soma and lamina densa of the capillary basement membrane. Similar ultrastructural changes were also observed in patient's kidney biopsy specimens. Compared with healthy murine kidneys, fibrotic kidneys had significantly increased extravasation of Evans blue dye in all 3 models. The extravasation could be visualized using 2-photon microscopy in real time in living animals and was mainly localized to capillary branching points. Finally, fibrotic kidneys in all models exhibited a significantly greater degree of interstitial deposition of fibrinogen. Thus, peritubular capillaries undergo significant ultrastructural and functional alterations during experimental progressive renal diseases, independent of the underlying injury. Analyses of these alterations could provide read-outs for the evaluation of therapeutic approaches targeting the renal microvasculature.

Cognitive impairment is a common and largely undiagnosed finding in a significant number of dialysis patients. These alterations may result from concomitant cerebrovascular disease, hemodynamic instability, the uremic milieu, or changes induced by the dialysis process. In order to gain further insight into this, we recruited 12 stable chronic hemodialysis patients (without clinical neurological disease) and an age- and gender-matched cohort of 12 control individuals (without renal or neurological problems) in a prospective, single-center study. In order to disentangle the influence of dialysis itself on memory function, each dialysis patient was tested twice: once immediately before dialysis following a long weekend (t1) and again the day after this dialysis (t2). The control individuals were tested in the same time frame. Neuropsychological testing found that the control individuals performed significantly better in verbal learning, motor speed, task switching, verbal comprehension, word fluency, spatial visualization, spatial perception, and reasoning; all independent of the time point. Functional magnetic resonance imaging of the whole brain in seven hemodialysis patients found significantly more bilateral activation of the hippocampus during the verbal working memory task at t2 relative to t1 compared with their seven matched control counterparts. Thus, our study found differential and task-specific activation of memory-relevant brain areas during a dialysis cycle.

The increasing global prevalence of chronic kidney disease (CKD) and end-stage renal disease with the associated spiraling cost has profound public health and economic implications. This has made slowing the progression of CKD, a major health-care priority. CKD is invariably characterized by progressive kidney fibrosis and at present, treatment aiming to slow the progression of CKD is limited to aggressive blood pressure control, with few therapies targeting the fibrotic process itself. In this review, we explore the potential of experimental therapeutic strategies, based on preventing or reversing the pathophysiologic steps of kidney remodeling that lead to fibrosis.

Platelet-derived growth factor (PDGF)-BB and PDGF-DD mediate mesangial cell proliferation in vitro and in vivo. While PDGF-BB is a ligand for the PDGF alpha- and beta-receptor chains, PDGF-DD binds more selectively to the beta-chain, suggesting potential differences in the biological activities. Signal transduction and regulation of gene expression induced by PDGF-BB and -DD were compared in primary human mesangial cells (HMCs), which expressed PDGF alpha- and beta-receptor subunits. The growth factor concentrations used were chosen based on their equipotency in inducing HMCs proliferation and binding to the betabeta-receptor. Both growth factors, albeit at different concentrations induced phosphorylation and activation of extracellular signal-regulated kinase 1 (ERK1) and ERK2. In addition, PDGFs led to the phosphorylation and activation of signal transducers and activators of transcription 1 (STAT1) and STAT3. HMCs proliferation induced by either PDGF-BB or -DD could be blocked by signal transduction inhibitors of the mitogen-activated protein kinase-, Janus kinase (JAK)/STAT-, or phosphatidyl-inositol 3-kinase pathways. Using a gene chip array and subsequent verification by real-time reverse transcriptase (RT)-polymerase chain reaction, we found that in HMC genes for matrix metalloproteinase 13 (MMP-13) and MMP-14 and, to a low extent, cytochrome B5 and cathepsin L were exclusively regulated by PDGF-BB, whereas no exclusive gene regulation was detected by PDGF-DD. However, at the protein level, both MMP-13 and -14 were equally induced by PDGF-BB and -DD. PDGF-BB and -DD effect similar biological responses in HMCs albeit at different potencies. Rare apparently differential gene regulation did not result in different protein expression, suggesting that in HMCs both PDGFs exert their biological activity almost exclusively via the PDGF beta-receptor.

Renal transplant recipients are at greater risk of infection from influenza than healthy individuals, due to therapeutic immunosuppression. Influenza can result in severe complications such as pneumonia, bacterial infections or even graft loss in these patients. However, immunosuppression impairs the efficacy of conventional influenza vaccines. A total of 116 adult (aged 18–64 years) renal transplant recipients were randomised to receive a single intramuscular injection of MF59-adjuvanted influenza vaccine (FLUAD®; n =60) or a conventional subunit influenza vaccine (Agrippal®; n =56). Safety and immunogenicity of both groups were assessed. Increases in geometric mean titres of antibody from pre- to post-immunisation were notably higher in the MF59-adjuvanted vaccine group for all three influenza antigens. Seroprotection rates were greater in the MF59-adjuvanted vaccine group, particularly for the A/H3N2 antigen (84% for the adjuvanted vaccine group versus 56% for the conventional vaccine group). Both vaccines were safe and well tolerated. It therefore seems reasonable to preferentially administer this adjuvanted vaccine over conventional vaccines in this immunocompromised population.

Rapid bone loss is a frequent finding early after kidney transplantation. Only limited data are available on the bone mineral density (BMD) in long-term kidney transplant recipients.In 26 kidney transplant recipients (13 men and 13 women, age 45.3 +/- 12.3 years), serum biochemical markers of bone metabolism and BMD at the lumbar vertebrae L2-4 were evaluated prospectively in three serial examinations (E1, E2, E3; method: dual-energy X-ray absorptiometry). Examinations were performed at 47 +/- 2 months, 59 +/- 2 months, and 71 +/- 2 months after transplantation. All patients received standard dual or triple immunosuppression including prednisolone.The mean BMD was significantly lower (P0.001) than in sex-matched young controls: T-score was -1.43 +/- 1.49 (E1), -1.39 +/- 1.40 (E2), and -1.44 +/- 1.30 (E3). The BMD did not change significantly (Delta BMD, -0.5 +/- 5.9%) from E1 to E3. Regression analysis did not show significant associations between Delta BMD and biochemical parameters or prednisolone dosage. No clinically apparent new lumbar vertebral fracture occurred. The mean intact parathyroid hormone was 110.1 +/- 97.5 pg/mL (E1), 121 +/- 102.7 pg/mL (E2), and 134.5 +/- 128.6 pg/mL (E3). Serum creatinine was 1.44 +/- 0.45 (128 +/- 40) mg/dL (micromol/L) (E1), 1.44 +/- 0.47 (127 +/- 42) mg/dL (micromol/L) (E2), and 1.45 +/- 0.70 (128 +/- 62) mg/dL (micromol/L) (E3). Ten patients (38.5%) showed an increase of BMD (+5.7 +/- 3.2%) and 15 patients (57.7%) showed a decrease of -4.7 +/- 3.2% (P0.0001). Both groups were different in T-scores at E1 (-2.29 +/- 1 versus -0.88 +/- 1.5); intact parathyroid hormone, creatinine, vitamin D levels, and prednisolone dosage were not significantly different.This study shows that lumbar BMD is reduced in long-term kidney transplant recipients. During our 24-month observation period, overall lumbar BMD remained stable.

Selective inhibition of inducible nitric oxide inhibition enhances intraglomerular coagulation in chronic anti-Thy 1 nephritis. Background A particular Lewis rat substrain (LEW/Maa) develops chronic glomerulonephritis in the anti-Thy 1 model (aThy 1-GN) characterized by increased microaneurysm formation, chronic glomerular sclerosis and persistent albuminuria. This phenotype is accompanied by increased and prolonged glomerular induction of inducible nitric oxide synthase (iNOS) when compared to the LEW/Moe substrain, in which aThy 1-GN resolves quickly. We investigated the effect of selective iNOS inhibition by L-N 6 -(1-iminoethyl)-lysine (L-NIL) administration on aThy 1-GN in LEW/Maa rats. Methods Nephritic rats were studied over a period of 7 days. L-NIL–treated animals received 20 mg/day L-NIL in the drinking water starting two days prior to disease induction. iNOS activity was determined in cultured glomeruli and in urine samples, respectively. Severity of aThy 1-GN was determined by scoring glomerular matrix expansion and microaneurysm formation, and by albuminuria measurements (ELISA). Immunohistochemical evaluation was performed including staining for macrophages (ED-1), platelets (PL-1) and fibrin deposition. Results L-NIL treated rats (+NIL) showed a significant decrease in peak nitrate production by ex vivo cultured glomeruli, and in urinary nitrate excretion versus untreated nephritic rats (-NIL). Mean arterial pressure remained unchanged in both +NIL and -NIL rats. +NIL rats developed significantly increased albuminuria (+44%) associated with a significant increase in glomerular platelet (+45%) and fibrin deposition (+48%). Conclusions Selective inhibition of iNOS aggravated albuminuria in chronic aThy 1-GN in LEW/Maa rats. Induction of iNOS during the inflammatory phase of this model may be a partially protective mechanism by interfering with intraglomerular coagulation processes.

Permeability of dialyzer membranes to TNFα-inducing substances derived from water bacteria. Pro-inflammatory cytokine-inducing substances derived from cultured E. coli have previously been shown to pass across low-flux regenerated cellulosic dialyzer membranes. In the present study, a sterile filtrate of Pseudomonas maltophilia grown from standard bicarbonate dialysis fluid was used to test the permeability of various dialyzer membranes (regenerated cellulose, cellulose triacetate, polyacrylonitrile, polysulfone and polyamide) to TNFα-inducing bacterial substances. Pyrogen-free tissue culture medium (MEM) was recirculated for 60 minutes in the dialysate compartment of a closed-loop dialysis system, then P. maltophilia filtrate was added and recirculation was continued for a further hour. Samples from the dialysate (MEM) and the blood side (containing 10% human plasma in MEM) were incubated with donor mononuclear cells (MNC) for 18 hours and TNFα release was measured in MNC supernatants by radioimmunoassay. Five minutes after the addition of P. maltophilia filtrate, mean TNFα-inducing activity in the dialysate increased from (mean ± sem) 0.10 ± 0.02 to 18.2 ± 1.5 (ng/2.5 × 106 MNC/18 hr). TNFα-inducing activity in the blood side increased with regenerated cellulose from 0.10 ± 0.01 to 4.57 ± 1.55 (N = 8; P < 0.001); with cellulose triacetate from 0.20 ± 0.05 to 0.44 ± 0.10 (N = 5; P < 0.05), and with polyacrylonitrile from 0.10 ± 0.02 to 1.16 ± 0.45 (N = 5; P < 0.03). No increased TNFα-inducing activity was observed in the blood side of polysulfone (N = 5) or polyamide dialyzers (N = 5). Polymyxin B reduced dialysate TNFα-inducing activity by 40%, but had no effect on the TNFα-inducing activity of samples derived from the blood compartments. We conclude that the permeability of dialyzer membranes to cytokine-inducing substances derived from water bacteria is influenced by the physicochemical nature of the membrane rather than its pore size. Backfiltration was ≤1.2ml/min with all dialyzers, suggesting that the transport of cytokine-inducing substances was predominantly by diffusion. As the cytokine-inducing material passed through low-flux regenerated cellulose, our data suggest that the molecular weight of the material is less than 5 kD.

Due to its potent chemotactic properties leukotriene B4 is an important mediator of inflammatory reactions. Cultured human kidney mesangial cells converted exogenously added leukotriene B4 efficiently into three different more lipophilic metabolites, two of them probably representing dihydro-leukotriene B4 isomers. This represents an alternative metabolic pathway, in contrast to leukotriene B4 omega-oxidation found in human polymorphonuclear leukocytes. Both dihydro-leukotriene B4 isomers had nearly completely lost their ability to induce leukocyte chemotaxis as compared to leukotriene B4.