Experimental mesangial proliferative glomerulonephritis (the anti-Thy-1.1 model)

The anti-Thy-1.1 model is a rat model of mesangial proliferative glomerulonephritis characterized by initial mesangiolysis followed by mesangial cell proliferation and accumulation of mesangial matrix with subsequent resolution and the return to almost normal histology. In this review we discuss the pathogenesis of the initial injury, the mechanisms governing mesangial cell proliferation and matrix expansion, and some of the processes involved in the resolution of glomerular injury. Understanding these processes of mesangial cell injury and recovery may provide insights into the pathogenesis of human mesangial cell diseases such as IgA nephropathy.

Obstructive uropathy in the mouse: role of osteopontin in interstitial fibrosis and apoptosis

BACKGROUND

Osteopontin is a macrophage adhesive protein that is expressed by renal tubules in tubulointerstitial disease.

METHODS

To investigate the function of OPN, we induced tubulointerstitial disease in OPN null mutant (OPN-/-) and wild-type (OPN+/+) mice by unilateral ureteral ligation. Tissue was analyzed for macrophages (ED-1), types I and IV collagen deposition, TGF-beta expression, and for tubular and interstitial cell apoptosis.

RESULTS

Obstructed kidneys from both OPN-/- and OPN+/+ mice developed hydronephrosis, tubular atrophy, interstitial inflammation and fibrosis. OPN was absent in OPN-/- kidneys but was increased in obstructed OPN+/+ kidneys. Macrophage influx, measured by computer-assisted quantitative immunostaining, was less in OPN-/- mice compared to OPN+/+ mice at day 4 (threefold, P < 0.02), day 7 (fivefold, P < 0.02), but not at day 14. Interstitial deposition of types I and IV collagen were also two- to fourfold less in obstructed OPN-/- kidneys (P < 0.02). There was also a reduction of TGF-beta mRNA expression in the interstitium at day 7 (by in situ hybridization) and a near significant 34% reduction in cortical TGF-beta activity (P = 0.06) compared to obstructed OPN+/+ kidneys at day 14. Obstructed kidneys from OPN-/- mice also had more interstitial and tubular apoptotic cells (TUNEL assay) compared to obstructed OPN+/+ mice at all time points. The ability of OPN to act as a cell survival factor was also documented by showing that the apoptosis of serum-starved NRK52E renal epithelial cells was markedly enhanced in the presence of neutralizing anti-OPN antibody.

CONCLUSION

OPN mediates early interstitial macrophage influx and interstitial fibrosis in unilateral ureteral obstruction. OPN may also function as a survival factor for renal tubulointerstitial cells.

Alpine ski bindings and injuries. Current findings

In spite of the fact that the overall incidence of alpine ski injuries has decreased during the last 25 years, the incidence of serious knee sprains usually involving the anterior cruciate ligament (ACL) has risen dramatically since the late 1970s. This trend runs counter to a dramatic reduction in lower leg injuries that began in the early 1970s and to date has lowered the risk of injury below the knee by almost 90%. One of the primary design objectives of modern ski boots and bindings has been to protect the skier from tibia and ankle fractures. So, in that sense, they have done an excellent job. However, despite advances in equipment design, modern ski bindings have not protected the knee from serious ligament trauma. At the present time, we are unaware of any binding design, settings or function that can protect both the knee and lower extremities from serious ligament sprains. No innovative change in binding design appears to be on the horizon that has the potential to reduce the risk of these severe knee injuries. Indeed, only 1 study has demonstrated a means to help reduce this risk of serious knee sprains, and this study involved education of skiers, not ski equipment. Despite the inability of bindings to reduce the risk of severe knee injuries there can be no doubt that improvement in ski bindings has been the most important factor in the marked reduction in incidence of lower leg and ankle injuries during the last 25 years. The authors strongly endorse the application of present International Standards Organisation (ISO) and American Society for Testing and Materials (ASTM) standards concerning mounting, setting and maintaining modern 'state of the art' bindings.

Role of Fas (CD95) in tubulointerstitial disease induced by unilateral ureteric obstruction

Murine renal tubular epithelial cells and interstitial fibroblasts may express both Fas (CD95) death receptor and Fas ligand and are vulnerable to Fas-mediated death in vitro. We therefore hypothesized that an absence of renal Fas may protect resident cells from undergoing apoptosis. We performed unilateral ureteric ligation [producing unilateral ureteral obstruction (UUO)] in 6-wk-old normal control mice and C57Bl6/lpr mice, which express a nonfunctional Fas receptor. Obstructed kidneys were removed at days 3, 7, and 14 (n = 6 per group). Tubular cell apoptosis at day 7 was significantly reduced in lpr mice [21.8 +/- 5.8 vs. 45.7 +/- 7.6 cells/10 high-power fields (hpf), P < 0.02]. Importantly, there was no difference in tubular cell proliferation between normal and lpr mice at any time point studied. Interestingly, double labeling with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) and the proximal tubule-specific antibody Fx1A indicated that the absence of Fas reduced distal but not proximal tubular death at day 7. In addition, there was no difference in interstitial cell apoptosis or proliferation, suggesting that Fas does not play a significant role in interstitial cell death. Importantly, inflammatory macrophage infiltration and ultimate collagen I deposition was unchanged in lpr mice. In conclusion, the absence of functional cell surface Fas in UUO provides distal tubular cells with partial protection from apoptosis but does not affect interstitial cell fate in this model of tubulointerstitial injury.

Renal injury and salt-sensitive hypertension after exposure to catecholamines

We investigated whether chronic infusion of phenylephrine could induce structural and functional changes in the kidney of rats with the subsequent development of salt-sensitive hypertension. Rats were infused with phenylephrine (0.15 mmol/kg per day) by minipump, resulting in a moderate increase in systolic blood pressure (BP) (17 to 25 mm Hg) and a marked increase in BP variability as measured by an internal telemetry device. After 8 weeks, the phenylephrine infusion was stopped with the return of BP to normal, and a nephrectomy was performed for histological studies. Glomeruli were largely spared, but focal tubulointerstitial fibrosis was present, with the de novo expression of osteopontin by injured tubules, macrophage and "myofibroblast" accumulation, and focal increases in mRNA for transforming growth factor beta by in situ hybridization. Peritubular capillaries at sites of injury had distorted morphology with shrinkage, rounding, and focal rarefaction, and endothelial cell proliferation was also identified. Rats were randomized to a high (8% NaCl or 1.36 mol/kg) or low (0.1% NaCl or 17 mmol/kg) salt diet. After 4 to 8 weeks, phenylephrine-treated rats on a high salt diet developed marked hypertension, which was in contrast with phenylephrine-treated rats placed on a low salt diet or vehicle-treated rats given a high salt diet. Hypertension after phenylephrine exposure correlated with the initial mean systolic BP (r(2)=0.99) and the degree of BP lability (r(2)=0.99) during the phenylephrine infusion, the amount of osteopontin expressed in the initial biopsy/nephrectomy (r(2)=0.74), and the final glomerular filtration rate (r(2)=0.58). These studies provide a mechanism by which a markedly elevated sympathetic nervous system can induce salt-dependent hypertension even when the hyperactive sympathetic state is no longer engaged.

Thrombospondin peptides are potent inhibitors of mesangial and glomerular endothelial cell proliferation in vitro and in vivo

BACKGROUND

Thrombospondin 1 (TSP1), a multifunctional, matricellular glycoprotein, is expressed de novo in many inflammatory disease processes, including glomerular disease. Short peptide fragments derived from the type I properdin repeats of the TSP1 molecule mimic anti-angiogenic and/or transforming growth factor-beta (TGF-beta)-activating properties of the whole TSP1 glycoprotein. We investigated the effects of D-reverse peptides derived from the type I domain of TSP1 in experimental mesangial proliferative glomerulonephritis in the rat (anti-Thy1 model), as well as their effects on cultured mesangial and glomerular endothelial cells.

METHODS

Effects of TSP peptides on proliferation of mesangial or glomerular endothelial cells in culture after growth arrest or growth factor stimulation (fibroblast growth factor-2, platelet-derived growth factor-BB, 10% fetal calf serum) were measured by [3H]thymidine incorporation assay. Adhesion of rat mesangial cells (MCs) to a TSP-peptide matrix was assayed using an attachment-hexosaminidase assay. TSP peptides were intraperitoneally injected daily in rats that had received an intravenous injection of polyclonal anti-Thy1 antibody to induce mesangial proliferative glomerulonephritis. On biopsies from days 2, 5, and 8 of anti-Thy1 disease, mesangial and glomerular endothelial proliferation, matrix expansion, mesangial activation, and microaneurysm formation were assessed. Functional parameters such as blood pressure and proteinuria were also measured.

RESULTS

An 18-amino acid peptide (type I peptide) with anti-angiogenic and TGF-beta-activating sequences decreased mesangial and glomerular endothelial cell proliferation in vitro and in vivo and reduced microaneurysm formation and proteinuria in experimental glomerulonephritis. Analogues lacking the TGF-beta-activating sequence mimicked most effects of the type I peptide. The mechanism of action of these peptides may include antagonism of fibroblast growth factor-2 and alteration of MC adhesion. The TGF-beta-activating sequence alone did not have significant effects on mesangial or glomerular endothelial cells in vitro or in experimental kidney disease in vivo.

CONCLUSION

Peptides from TSP1 may be promising therapeutics in treating glomerular disease with mesangial and endothelial cell injury.

The cyclin kinase inhibitor p21CIP1/WAF1 limits glomerular epithelial cell proliferation in experimental glomerulonephritis

BACKGROUND

During glomerulogenesis, visceral glomerular epithelial cells (VECs) exit the cell cycle and become terminally differentiated and quiescent. In contrast to other resident glomerular cells, VECs undergo little if any proliferation in response to injury. However, the mechanisms for this remain unclear. Cell proliferation is controlled by cell-cycle regulatory proteins where the cyclin-dependent kinase inhibitor p21Cip1,WAF1 (p21) inhibits cell proliferation and is required for differentiation of many nonrenal cell types.

METHODS

To test the hypothesis that p21 is required to maintain a differentiated and quiescent VEC phenotype, experimental glomerulonephritis was induced in p21 knockout (-/-) and p21 wild-type (+/+) mice with antiglomerular antibody. DNA synthesis (proliferating cell nuclear antigen, bromodeoxyuridine staining), VEC proliferation (multilayers of cells in Bowman's space), matrix accumulation (periodic acid-Schiff, silver staining), apoptosis (TUNEL), and renal function (serum urea nitrogen) were studied on days 5 and 14 (N = 6 per time point). VECs were identified by location, morphology, ezrin staining, and electron microscopy. VEC differentiation was measured by staining for Wilms' tumor-1 gene.

RESULTS

Kidneys from unmanipulated p21-/- mice were histologically normal and did not have increased DNA synthesis, suggesting that p21 was not required for the induction of VEC terminal differentiation. Proliferating cell nuclear antigen and bromodeoxyuridine staining was increased 4.3- and 3.3-fold, respectively, in p21-/- mice with glomerulonephritis (P < 0.0001 vs. p21+/+ mice). At each time point, VEC proliferation was also increased in nephritic p21-/- mice (P < 0.0001 vs. p21+/+ mice). VEC re-entry into the cell cycle was associated with the loss of Wilms' tumor-1 gene staining. Nephritic p21-/- mice had increased extracellular matrix protein accumulation and apoptosis and decreased renal function (serum urea nitrogen) compared with p21+/+ mice (P < 0.001).

CONCLUSION

These results show that the cyclin kinase inhibitor p21 is not required by VECs to attain a terminally differentiated VEC phenotype. However, the loss of p21, in disease states, is associated with VEC re-entry into the cell cycle and the development of a dedifferentiated proliferative phenotype.

The diagnostic value of positron emission tomography (PET) with radiolabelled fluorodeoxyglucose (18F-FDG) in head and neck cancer

Positron emission tomography (PET) scanning has recently been introduced into clinical practice but its usefulness in the management of head and neck cancer is not well defined. The aim of this prospective preliminary study was to examine the clinical value of fluorodeoxyglucose (FDG)--PET in patients with head and neck cancer treated by radiotherapy with surgery in reserve by (i) relating quantitative uptake of isotope to tumour type and histological grade and (ii) comparing the imaging findings of PET and magnetic resonance imaging (MRI) in post-radiotherapy assessment of tumour response. Twenty-one patients had pre-treatment PET and MRI scans and these were repeated four and eight months after treatment if there was no clinical relapse. Pre-treatment uptake of FDG using tumour to cerebellar ratio parameters was significantly related to the histological grade of squamous cancer (p = 0.04) but not to tumour type. Discordance of post-treatment PET/MRI findings in one case indicates a possible role for PET in the early detection of tumour recurrence. Other potential uses of PET scanning in the management of head and neck cancer are discussed.

Mechanisms of endothelin-induced venoconstriction in isolated guinea pig mesentery

In the present study, endothelin (ET) agonists and receptor selective antagonists were used to characterize ET receptors mediating constriction in guinea pig mesenteric veins (250-300 micrometers diameter) in vitro. The contribution of ET-evoked vasodilator release to venous tone was also explored. Computer-assisted video microscopy was used to monitor vein diameter. Endothelin-1 (ET-1), endothelin-3 (ET-3), and sarafotoxin 6c (S6c) produced sustained concentration-dependent contractions with a rank order agonist potency of ET-1 = S6c > ET-3. Indomethacin (1 microM) and Nomega-nitro-L-arginine (100 microM) enhanced ET-1 and S6c responses. The ETA selective antagonists BQ-610 (100 nM) and PD156707 (10 nM) shifted ET-1 concentration-response curves rightward and decreased maximal ET-1 responses, without changing S6c responses. The ETB selective antagonist BQ-788 (100 nM) shifted S6c responses rightward but produced no change in ET-1 responses. Combined application of BQ-788 and BQ-610 or BQ-788 and PD 156707 produced a rightward shift in ET-1 responses that was greater than shifts produced by BQ-610 or PD 156707 alone. In conclusion, smooth muscle in guinea pig mesenteric veins expresses ETA and ETB receptors coupled to contractile mechanisms. Activation of endothelial ETB receptors results in release of vasodilators, primarily nitric oxide.

Salt-sensitive hypertension develops after short-term exposure to Angiotensin II

We hypothesized that short-term exposure to angiotensin II (Ang II) could result in structural and functional changes in the kidney that would favor sodium retention and the development of sustained hypertension. To test this hypothesis, rats were exposed to pressor doses (435 ng. kg-1. min-1) of Ang II for 2 weeks. The infusion of Ang II was associated with acute hypertension, renal dysfunction, proteinuria, and focal tubulointerstitial and vascular damage. At sites of the tubulointerstitial damage, there was a reduction in peritubular capillary endothelial cell staining. By use of immunostaining, we found focal loss of endothelial nitric oxide synthase (eNOS) in the peritubular capillaries at sites of injury and a generalized reduction in eNOS in collecting ducts, thin loops of Henle, and vascular bundles in the medulla. When the Ang II infusion ended, the rats became normotensive and renal function returned toward normal. However, exposure of the rats to high salt diet (4% NaCl) resulted in the redevelopment of hypertension after 3 to 4 weeks. Rats maintained on a high salt diet with no prior exposure to Ang II and rats placed on low salt diet (0.1% NaCl) after exposure to Ang II remained normotensive. Thus, we report a new model of salt-sensitive hypertension induced by transient exposure to pressor doses of Ang II. The mechanism may relate to microvascular injury with peritubular capillary loss coupled with functional changes, such as a loss in intrarenal nitric oxide formation, that could alter the ability of the kidney to excrete a salt load.

The potential for Ontario region's health information system to facilitate case management, program planning, and evaluation and to promote enhanced First Nations' control of health services

The Ontario Region of Medical Services Branch, Health Canada, comprises approximately 63,000 First Nations people living on-reserve in four geographical areas: Sioux Lookout, Moose Factory, Thunder Bay, and Southern Ontario. As of April 1996, 35% of the 126 First Nations communities in Ontario Region have either assumed control of the delivery of health services or are in the process of transfer negotiations with the federal government. Another 14% have entered into Integrated Community-based Health Services Agreements with the federal government, which is an intermediate step that could culminate in a complete transfer agreement. In order to provide First Nations with an epidemiological database for effective program planning and evaluation, Medical Services Branch, Ontario Region, has worked in partnership with First Nations during the past two and one-half years to develop a comprehensive, computerized Health Information System (HIS). HIS will provide First Nations with a significant degree of autonomy from the Medical Services Branch structure, with regard to access to health information for case management, program planning and evaluation, and the establishment of their own program priorities at the community level. With access to the HIS, First Nations will eventually be able to re-profile available resource in response to their own identified community health priorities.

The effect of anterior cruciate ligament trauma and bracing on knee proprioception

We studied the effect that chronic anterior cruciate ligament disruption, functional bracing, and a neoprene sleeve have on knee proprioception by measuring the threshold to detection of passive knee motion in all three conditions. The threshold to detection of passive knee motion was worse in knees with chronic anterior cruciate ligament insufficiency when compared with uninjured knees. This difference was small, on average an additional 0.28 degree of flexion-extension rotation was required for the anterior cruciate ligament-deficient knee before the subject detected motion, and of questionable significance from a clinical and functional perspective. Wearing a functional brace or neoprene sleeve on the anterior cruciate ligament-deficient knee did not significantly change the threshold to detection of passive motion in comparison with the same knee without a brace, although improvements were observed. There was no relationship between the most common clinical means of characterizing altered biomechanics of the anterior cruciate ligament-deficient knee (that is, the magnitude of anterior-posterior knee laxity and the grade of pivot shift) and the threshold to detection of passive knee motion.

The strain behavior of the anterior cruciate ligament during stair climbing: an in vivo study

Stair climbing is a closed kinetic chain exercise that is thought to be useful for knee rehabilitation following anterior cruciate ligament (ACL) reconstruction while protecting the graft from excessive strain. The objectives of this study were to measure the strain produced in the anteromedial band (AMB) of the normal ACL during stair climbing in vivo. We have previously shown that the normal AMB strain pattern during knee passive flexion-extension motion is similar to that of an ACL graft immediately after graft fixation. We successfully tested five subjects with normal ACLs, who were candidates for arthroscopic meniscectomy under local anesthesia. AMB strain was measured in vivo using the Differential Variable Reluctance Transducer (MicroStrain, Burlington, VT). The stair climbing activities were performed on a StairMaster 4000PT (Randall Sports Medicine, Kirkland, WA). Two different climbing cadences were evaluated; 80 and 112 steps per minute. Consistent with our previous studies of ACL biomechanics, strain values increased as the knee was moved from a flexed to an extended position. The mean peak AMB strain values for the 80 and 112 steps per minute conditions were 2.69% (+/-2.89&) and 2.76% (+/-2.68%), respectively. These values were not significantly different. Compared with other rehabilitation activities previously tested in the same manner, the AMB strain values produced during stair climbing were highly variable across subjects. High strain values were observed in some patients but not in others.

Osteopontin expression in fetal and mature human kidney

Osteopontin is a secreted phosphoprotein that is expressed by normal kidney, and has been associated with a number of functions including cell adhesion, migration, signaling, and biomineralization. Although there is a vast literature detailing osteopontin localization in various rodent models of both development and disease, this article presents the first comprehensive description of osteopontin localization in human kidney. In this study, immunohistochemistry, immunoelectron microscopy, in situ hybridization, and Northern blotting are used to analyze osteopontin protein and mRNA expression in human fetal and normal mature renal tissue. Osteopontin is expressed in the human embryonic renal tubular epithelium beginning on approximately day 75 to 80 of gestation. In the fetal kidney, osteopontin can also be seen occasionally expressed in the ureteric buds and in some interstitial cells. As localized at the protein and mRNA level, the tubular expression of osteopontin increases with increasing gestational age and persists into adulthood. In the normal adult kidney, osteopontin is localized primarily to the distal nephron and is strongly expressed by the thick ascending limb of the loops of Henle. Osteopontin expression can also be observed in some collecting duct epithelium. In cases that exhibit foci of interstitial fibrosis and an associated influx of interstitial macrophages, osteopontin expression is significantly upregulated in all tubular segments, including proximal tubules.

IL-1 up-regulates osteopontin expression in experimental crescentic glomerulonephritis in the rat

Osteopontin (OPN) is a macrophage chemotactic and adhesion molecule that acts to promote macrophage infiltration in rat anti-glomerular basement membrane (GBM) glomerulonephritis. The present study investigated the role of interleukin-1 (IL-1) in the up-regulation of renal OPN expression in this disease model. Accelerated anti-GBM glomerulonephritis was induced in groups of six rats. Animals were treated by a constant infusion of the IL-1 receptor antagonist or saline (control) over days -1 to 14 (induction phase) or days 7 to 21 (established disease). In normal rat kidney, OPN was expressed in a few tubules (<5%) and absent from glomeruli. During the development of rat anti-GBM disease (days 7 to 21), there was substantial up-regulation of OPN mRNA and protein expression in glomeruli (>5 cells per glomerular cross-section) and tubular epithelial cells (50-75% OPN-positive). Up-regulation of OPN expression was associated with macrophage accumulation within the kidney, severe proteinuria, loss of renal function, and severe histological damage including glomerular crescentic formation and tubulointerstitial fibrosis. In contrast, IL-1 receptor antagonist treatment of either the induction phase of disease or established disease significantly reduced OPN mRNA and protein expression in glomeruli (/75-85%, P < 0.001) and tubules (/45-60%, P < 0.001). The reduction in OPN expression was associated with significant inhibition of macrophage accumulation and progressive renal injury. In vitro, the addition of IL-1 to the normal rat tubular epithelial cell line NRK52E up-regulated OPN mRNA and protein levels, an effect that was dose-dependent and inhibited by the addition of IL-1 receptor antagonist, thus demonstrating that IL-1 can act directly to up-regulate renal OPN expression. In conclusion, this study provides in vivo and in vitro evidence that IL-1 up-regulates OPN expression in experimental kidney disease and support for the argument that inhibition of OPN expression is one mechanism by which IL-1 receptor antagonist treatment suppresses macrophage-mediated renal injury.

Reappraisal of the pathogenesis and consequences of hyperuricemia in hypertension, cardiovascular disease, and renal disease

An elevated uric acid level is associated with cardiovascular disease. Hyperuricemia is predictive for the development of both hypertension and coronary artery disease; it is increased in patients with hypertension, and, when present in hypertension, an elevated uric acid level is associated with increased cardiovascular morbidity and mortality. Serum uric acid level should be measured in patients at risk for coronary artery disease because it carries prognostic information. Hyperuricemia is caused by decreased renal excretion. In this article, we suggest that this may be mediated by intrarenal ischemia with lactate generation and the inhibition of the secretion of urate by the anion-exchange transport system. The possibility that hyperuricemia directly contributes to cardiovascular or renal disease needs to be reconsidered. Although hyperuricemia is associated with a number of cardiovascular or renal risk factors, several studies have found uric acid level to be independently associated with increased mortality by multivariate analysis. If hyperuricemia is directly toxic, the most likely site is the kidney. Chronic hyperuricemia is strongly associated with chronic tubulointerstitial disease, and many of these patients have decreased renal function. Although it is possible that the hyperuricemia could simply be the consequence of the renal disease, further studies are necessary to rule out a pathogenic role for uric acid in the development of renal disease and salt-dependent hypertension.

Focal segmental glomerular sclerosis among patients infected with hepatitis C virus

This study describes the occurence of hepatitis C virus (HCV) infection in the setting of focal segmental glomerular sclerosis (FSGS). All patients with the pathologic diagnosis of idiopathic FSGS between 1992 and 1996 at the University of Washington Hospitals were examined using a retrospective cohort study design. FSGS was determined by renal biopsy in the absence of secondary causes. Demographic, laboratory, and outcome data were collected in a standardized fashion. Six patients (50%) were infected with HCV. Patients with HCV infection and FSGS were primarily Black (67%), hypertensive (100%), had a history of intravenous drug abuse (83%), and had normal liver enzymes. Those with HCV infection and a history of IVDA appeared clinically and histologically similar to previously described cases of 'heroin nephropathy'. We demonstrate that there is a high prevalence of HCV infection in our population of patients with idiopathic FSGS. Although this may simply reflect an epiphenomenon, we propose that HCV infection may play a role in the development of FSGS in a predisposed host.

Intracranial juvenile nasopharyngeal angiofibroma

We report the case history of a 26-year-old man who was diagnosed with advanced juvenile nasopharyngeal angiofibroma with intracranial extension. The lesion was considered to be inoperable and the patient was treated with radical radiotherapy. Serial magnetic resonance imaging has shown continued tumour regression and he remains well after 3 years. The literature is reviewed and radiotherapy recommended as the modality of choice for these patients.

The plasma membrane-actin linking protein, ezrin, is a glomerular epithelial cell marker in glomerulogenesis, in the adult kidney and in glomerular injury

BACKGROUND

Ezrin belongs to a family of plasma membrane-cytoskeleton linking, actin binding proteins (Ezrin-radixin-Moesin family) involved in signal transduction, growth control, cell-cell adhesion, and microvilli formation.

METHODS

The expression of ezrin was examined in glomerular cells in culture, during kidney development, in the mature kidney, and in five different experimental kidney disease models in the rat.

RESULTS

Ezrin was specifically expressed in glomerular epithelial cells in developing glomeruli in mature glomeruli and in glomerular epithelial cells in culture. Distinct from its other family members, moesin and radixin, which are predominantly expressed in glomerular endothelial and mesangial areas, ezrin protein (by immunohistochemistry) was specifically and exclusively modulated during podocyte injury and regeneration. Ezrin immunohistochemistry was able to visualize cell body attenuation, pseudocysts, and in particular vacuolation of injured podocytes, a feature that usually has to be identified at the ultrastructural level, and was strikingly increased in binucleated podocytes or podocytes that were partially or completely detached from the underlying GBM (frequently also binucleated). Infiltrating macrophages also express ezrin, but can easily be differentiated from podocytes by their round shape and higher level of expression.

CONCLUSIONS

Ezrin likely has a role in the cytoskeletal organization, such as reassembling of acting filaments accompanying podocyte injury and regeneration. Since suitable light microscopic markers for the identification of glomerular epithelial cells are rare, ezrin may also be a useful marker for podocytes in normal and injured glomeruli.

Risk of death among chronic dialysis patients infected with hepatitis C virus

Hepatitis C virus (HCV) infection is highly prevalent among chronic dialysis patients (10% to 40%) and is the most common cause of chronic liver disease. However, there are no studies estimating the risk for death among dialysis patients infected with HCV compared with those not infected. We conducted a prospective cohort study to estimate the risk for death among chronic dialysis patients infected with HCV compared with those not infected. In 1992, 200 patients (91%) who had been undergoing dialysis therapy for at least 6 months consented to be screened for HCV infection by enzyme immunoblot assay and polymerase chain reaction (PCR). Information about potential confounders and potential risk factors for death and HCV infection was obtained from the dialysis center database. Patient outcomes collected included death, transplantation, and loss to follow-up. The Cox proportional hazards model was used to estimate the odds of death among dialysis patients who were positive for the HCV antibody and HCV RNA compared with negative patients. Forty-four patients (22%) were HCV antibody positive. Thirty-four patients (17%) were HCV RNA positive. Patients in the HCV RNA-positive group were more likely to be younger (51.8+/-12.6 v 57.2+/-17.3 years of age), men (77% v 54%), and black (65% v 37%). None of the home hemodialysis or peritoneal dialysis patients were HCV RNA positive, whereas one of the home hemodialysis and one of the peritoneal dialysis patients were HCV antibody positive. Two patients became infected with HCV during the follow-up period. Patients who were HCV RNA positive and those who were HCV antibody positive were at increased risk for death compared with patients who were negative (adjusted relative risk [aRR]=1.78; 95% confidence interval [CI], 1.01 to 3.14; P=0.045; and aRR=1.97; 95% CI, 1.16 to 3.33; P=0.012, respectively), after adjusting for time on dialysis, race, transplantation, and age. We conclude that HCV infection increased the risk for death during the study period compared with those not infected. Further studies should assess the measures used to prevent and treat HCV infection.

Role of intrinsic renal cells versus infiltrating cells in glomerular crescent formation

BACKGROUND

Studies were undertaken to characterize the cellular composition that occurs in glomeruli and the tubulointerstitium of a passive model of complement-independent crescentic nephritis in mice.

METHODS

Glomerulonephritis was induced by the injection of antibody to whole rabbit glomeruli, and tissue was examined histologically at 7, 14 and 28 days.

RESULTS

Mice developed proteinuria, glomerular crescents, and progressive glomerulosclerosis and tubulointerstitial fibrosis. The majority of the cells within the crescents appeared to be intrinsic ezrin-positive epithelial cells of visceral or parietal origin. Many of the ezrin positive cells were proliferating and expressing the PDGF receptor. Despite expression of the macrophage adhesive protein, osteopontin, the early crescents were devoid of infiltrating macrophages, T cells or myofibroblasts, which could be explained by the finding that the Bowman's capsule remained intact. Tubulointerstitial damage also occurred, and included tubular dilation and atrophy, periglomerular and patchy interstitial infiltration and interstitial fibrosis with increased interstitial deposition of type IV collagen and laminin. Interstitial infiltrating cells included macrophages, CD4+ T lymphocytes, CD8+ T lymphocytes, and activated myofibroblasts. Tubular osteopontin expression was increased in the areas of tubulointerstitial damage and was associated with interstitial macrophage infiltration.

CONCLUSIONS

We describe an experimental model of complement-independent murine crescentic nephritis associated with tubulointerstitial injury. Proliferating glomerular epithelial cells are the main cellular components of the crescents in this model.

Osteopontin expression, tubulointerstitial disease, and essential hypertension

A role has recently been proposed for the tubulointerstitium in the pathogenesis of salt-dependent essential hypertension. In this study, biopsies from patients with essential hypertension with either minimal ("benign") or severe ("decompensated") tubulointertitial injury were analyzed for the expression of osteopontin, a protein known to modulate tubulointerstitial damage and nitric oxide production. In biopsies from patients with decompensated arteriolosclerosis, osteopontin mRNA and protein were increased in tubules in association with expression of alpha-smooth muscle actin by interstitial fibroblasts and increased type IV collagen deposition. The relevance of these findings to the pathogenesis of essential hypertension is discussed.

Predictive value of clinical examination, transrectal ultrasound and magnetic resonance imaging prior to radiotherapy in carcinoma of the cervix

The objectives of this study were to compare tumour staging and volume assessment by examination under anaesthesia (EUA), transrectal ultrasound (TRU) and magnetic resonance imaging (MRI) in patients with invasive carcinoma of the cervix, and to correlate findings with long-term outcome following treatment by radiotherapy. Tumour staging was performed on 60 patients immediately before starting radiotherapy. Clinicians and radiologists performing EUA, TRU or MRI were blinded to the results of other investigations. Tumour stage and dimensions were recorded prospectively for each technique, and analysed for concordance. The relationship between pre-treatment stage, size of tumour and patient outcome after radiotherapy was assessed, using clinical status 5 years after treatment as the truth measure. EUA, TRU and MRI assigned the same tumour stage in only 30% of patients and EUA and MRI agreed tumour stage in a further 27%. In cases of disagreement, the MRI stage correlated better with outcome than the TRU or EUA stage. There was a significant difference between tumour volume obtained from measurements made on MRI and those from TRU. 62% of patients with enlarged lymph nodes on pre-treatment MRI either died, or developed tumour recurrence or metastases. The ability of MRI to assess the full extent of bulky tumours and the presence of lymph node enlargement was an advantage over both EUA and TRU in identifying patients with a poor prognosis.

A new model of renal microvascular injury

The vascular endothelial injury with its consequent activation is actively involved in inflammation and promotion of a procoagulant state, which are likely to be of major importance in the pathogenesis of various disorders, including renal thrombotic microangiopathy. This study briefly reviews the consequences of glomerular endothelial cell injury or activation, as shown by recent experimental data.