The progression of chronic renal failure: An unmet challenge

An increasing number of patients require dialysis replacement therapy every year in Europe. This reflects the large number of patients with chronic renal failure (CRF) and the progressive nature of their underlying nephropathies. Worldwide, the annual incidence of acceptance rates on renal replacement programmes varies between 25 patient per million of population (pmp) in some developing countries to 58.6 pmp in Europe, 169 pmp in the USA [I] and 194.2 pmp in Japan [2]. In Europe, there are in excess of 312 pmp on replacement therapy with France having one of the highest prevalence within the continent with 628 pmp [3]. Further, there are important differences in the incidence of end stage renal failure (ESRF) according to age, gender and race. In Western countries, the incidence of ESRF is lowest in children (10 pmp/year) and highest in the elderly (> 400 pmp/year in patients over the age of 75). The incidence of ESRF is higher in males. In the United States, the incidence of ESRF is higher in Afro-Carribeans and native Americans [4]. This reflects both an increased prevalence of CRF in these ethnic minorities as well as a higher rate of progression [4]. It also reflects the higher incidence of systemic hypertension and diabetic nephropathy in black and native Americans respectively [4].In the United Kingdom, the incidence of ESRF is higher in Asians [5].

Social deprivation and prevalence of chronic kidney disease in the UK: workload implications for primary care

BACKGROUND

The 'inverse care law' suggests that populations with the poorest health outcomes also tend to have poorer access to high-quality care. The new general practitioner (GP) contract in the UK aimed to reduce variations in care between areas by collecting information on processes and outcomes of chronic disease management. This study investigated whether, despite reductions in inequalities, primary care in deprived areas is still at a disadvantage due to the higher prevalence of chronic diseases, using chronic kidney disease (CKD) as an example.

METHODS

Initially, data from a hospital-based cohort of CKD patients were analysed to investigate the clustering of CKD patients across area-level deprivation using a geographical information system that employed kernel density estimation. Data from the Quality and Outcomes Framework were then analysed to explore the burden of CKD and associated non-communicable chronic diseases (NCD) and assess the potential impact on GPs' workload by area-level deprivation.

RESULTS

There was a significant clustering of CKD patients referred to the hospital in the most deprived areas. Both the prevalence of CKD and associated conditions and caseload per GP were significantly higher in deprived areas.

CONCLUSION

In the most deprived areas, there is an increased burden of major chronic disease and a higher caseload for clinicians. These reflect significant differences in workload for practices in deprived areas, which needs to be addressed.

Association of deprivation with worse outcomes in chronic kidney disease: findings from a hospital-based cohort in the United Kingdom

BACKGROUND

Chronic kidney disease (CKD) prevalence and complications are known to be associated with deprivation, but there is limited understanding of the underlying reasons for inequalities.

AIMS

To evaluate the association of both individual and area level socioeconomic status (SES) with heavy proteinuria at presentation, progression of CKD, end-stage renal disease (ESRD) and death.

METHODS

A retrospective study of 918 CKD patients using integral multivariate logistic regression to adjust for known clinical and demographic explanatory variables.

RESULTS

During 3 years of median follow-up, 34% of the study population had progression of their CKD and of these, 32% experienced rapid progression. 23% presented with heavy proteinuria (urine protein:creatinine ratio ≥300 mg/mmol), 4% developed ESRD requiring renal replacement therapy and 10% died. Area level deprivation was independently associated with heavy proteinuria, progression and rapid progression of CKD. People living in the most deprived areas were more likely to develop ESRD. Unskilled professionals were more likely to experience a higher mortality rate.

CONCLUSION

Area level SES is inversely associated with both heavy proteinuria on presentation and progression as well as rapid progression of CKD. In contrast, individual level SES, unskilled professionals found to have a marginally significant association with increased risk of mortality. People living in more deprived areas presenting with CKD are likely to be at increased risk of poor outcomes and may need more active management and earlier referral.

Cardiorenal risk prevalence in sickle cell hemoglobinopathy

INTRODUCTION

The spectrum of kidney functional and structural alterations in sickle cell hemoglobinopathy (SCH) is broad. Also, morbidity and mortality from end organ dysfunction, especially cardiorenal dysfunction, are substantial. Consequently, screening an SCH population prospectively for surrogate markers of cardiorenal risk such as albuminuria and intima-media thickness (IMT) was the aim of this cross-sectional study.

PATIENTS AND METHODS

We screened 165 patients with SCH over 4 months at the Primary Care Department, King Abdulaziz Armed Forces Hospital, Saudi Arabia. The 133 who fulfilled the inclusion criteria have been referred for further investigations. Anthropometric evaluation of body mass index (BMI) and blood pressure (BP), determination of 24-hour urine albuminuria, fasting lipids, computed atherogenic risk ratio (ARR), estimated glomerular filtration rate (eGFR), common carotid artery (CCA) IMT measurements, and hemoglobin (Hb) electrophoresis were done.

RESULTS

Increased urinary albumin excretion (UAE) rate [380 (272.2-489.6) mg/day; mean and 95% confidence interval (95% CI) of mean] was detected in 24% of SCH patients (6 males and 26 females). Microalbuminuria (168.8 +/- 59.7 mg/day) was noted in the majority (63.6%) while macroalbuminuria (752.7 +/- 205.4 mg/day) was detected in a smaller percentage (36.4%). Patients with sickle cell disease (SCD) contributed about 66.6% of subjects with microalbuminuria and 100% of those with macroalbuminuria, while most individuals with sickle cell trait (89%) were normoalbuminuric (p < 0.0001). Preclinical atherosclerosis (increased CCA IMT and/or atheromatous plaques) was noticed in 68.8% of SCH individuals with increased UAE (ANOVA p = 0.003). The microalbuminuric and macroalbuminuric patients had comparable BMI, BP values and lipid profiles. However, the microalbuminuric sicklers were significantly younger (28.4 +/- 6.7 vs. 34.0 +/- 7.2 years, p = 0.04), less anemic (Hb: 9.13 +/- 2 vs. 7.47 +/- 0.8 g/dl, p = 0.015), with lesser atherosclerosis (IMT; 0.68 +/- 0.1 vs. 0.78 +/- 0.1 mm, p = 0.004) and higher eGFR (83.3 +/- 17.2 vs. 61 +/- 10.7 ml/min/1.73 m(2), p = 0.0004) compared to those with macroalbuminuria. UAE correlated positively with age (r = 0.591, p = 0.0001), systolic BP (r = 0.483, p = 0.005), IMT (r = 0.399, p = 0.024) and negatively with Hb (r = -0.409, p = 0.02), and eGFR (r = -0.620, p = 0.0001). By univariate analysis, the significant indicators of UAE in SCH patients were age (p = 0.05), BMI (p = 0.041), IMT (p = 0.018) and eGFR (p = 0.016). Also, increased risk (odds ratio) of albuminuria was noted with SCD, age, anemia, abnormal eGFR, obesity, and ARR.

CONCLUSIONS

Markers of cardiorenal risk such as albuminuria and IMT are common findings in SCH patients of Arabic descent and could be useful screening tools to identify sicklers at risk for cardiovascular and renal events.

Prevalence of increased albumin excretion rate in young saudi adults

INTRODUCTION

Albuminuria is an important risk predictor of chronic kidney disease and cardiovascular disease. In this study, we aim to evaluate the prevalence of increased urinary albumin excretion (UAE) rate amongst a subgroup of young Saudi army/navy recruits.

METHODS

2,000 Saudi military recruits were tested for microalbuminuria by dipstick and 24-hour urine collection for quantitative evaluation.

RESULTS

In the whole group studied, the rate of microalbuminuria-positive dipstick testing was 10.3% (n = 206), but decreased on quantitative evaluation of 24-hour urine collection to 6.2% (n = 124). Increased UAE was independently associated with diabetes mellitus (DM), hypertension (HT), obesity, male gender and hypercholesterolemia. 55 of the 124 (44.4%) were diabetics while 14 (11.3%) were hypertensives. Around 21% of individuals with albuminuria were obese; body mass index for the whole group with albuminuria = 31.15 +/- 5.8 kg/m(2) and showed no gender difference. Increased risk of albuminuria was noted with DM (OR = 5.07 [3.5-7.4], p < 0.0001), obesity (OR = 1.59 [1.0-2.5], p = 0.042) and HT (OR = 1.8 [1.0-3.2], p = 0.046). An estimated glomerular filtration rate of approximately 77 ml/min/1.73 m(2) was present in the whole group with a significantly lower level in macroalbuminuric subjects compared to those with microalbuminuria (p = 0.03). Also, age was higher in the macroalbuminuric group (p = 0.004) with comparable prevalence of DM (47.4 vs. 45.2%, p = NS).

CONCLUSIONS

This is the first description of increased UAE in a small percentage of young adult Arab subjects from Saudi Arabia detected through a selective screening process carried out on potential army recruits. It highlights the association of albuminuria in the general population with predisposing conditions such as DM, HT and obesity.

Localization of matrix metalloproteinases and their inhibitors in experimental progressive kidney scarring

The extracellular matrix (ECM) is in a continual state of turnover with homeostasis maintained by balancing synthesis and degradation rates. During progressive kidney scarring an imbalance occurs leading to ECM accumulation. Reduced matrix metalloproteinase (MMP) activity is believed to central to this imbalance. However, most of the data relating to MMPs and their natural inhibitors (tissue inhibitors of matrix metalloproteinase (TIMP)) is based on homogenate studies where in situ compartmentalization is lost and thus changes in MMP activity may be artificial. To address this we have developed a sensitive, high-resolution in situ zymography technique and applied it, along with immunohistochemistry, to the 5/6th subtotal nephrectomy model of kidney scarring. ECM proteolytic activity in kidney homogenates progressively declined post-SNx against both gelatin (-82%) and collagen I (-78%) substrates. In situ zymography revealed higher activity with both substrates within the cytoplasm of normal tubular cells compared to the SNx. In contrast, there was 96% greater activity in the SNx glomeruli than normal. Immunohistochemistry confirmed a predominantly intracellular tubular location of all MMPs and TIMPs. Tubules showed reduced MMP-3 and elevated TIMP-2, whereas MMP-1 increased significantly in the glomeruli, especially in the mesangial matrix. TIMP-1 showed a fourfold increase in the remnant kidney by Western blot analysis, but could not be localized. Lowered MMP activity in homogenates results from reduced intracellular activity in the tubules, indicating that reduced MMP activity may not play a direct role in the expansion of the tubular ECM in scarring. However, elevated MMP-1 activity in the glomeruli may play a significant role in initiating glomerular remodelling.

Prednisolone and azathioprine in membranous nephropathy: a 10-year follow-up study

BACKGROUND

Idiopathic membranous nephropathy (IMN) is the most common cause of nephrotic syndrome in adults. Although its clinical course is usually benign, some patients develop chronic renal failure. Combination of corticosteroids with cytotoxic drugs and cyclosporin have been used in the treatment of the disease. Conflicting results are reported with the use ofprednisolone and azathioprine. In this study, the effect of treatment with prednisolone and azathioprine and the parameters related to a poor outcome over a follow-up period of 10 years is estimated.

METHODS

50 patients were included in this study; 33 were treated with prednisolone (initially 60 mg/day) and azathioprine (initially 2 mg/kg body weight/day) in gradually reduced doses for 26 +/- 9 months, whereas 17 patients received no immunosuppressive drugs. The clinical course was estimated using the end-points of doubling of baseline serum creatinine and/or end-stage renal failure (ESRF). The contribution of clinical and histological parameters in the clinical outcome was examined by univariate and multivariate analyses.

RESULTS

Doubling of baseline serum creatinine was observed in 20 of 50 patients (40%), 14 from treated and 6 from the untreated group (42% vs. 35%, p=NS). ESRF developed in 10 of 50 patients (20%), 7 from treated and 3 from the untreated group (21% vs. 18%, p=NS). Most patients from both groups who reached the end-points had impaired renal function at presentation and persistent nephrotic syndrome during the follow-up period. Both parameters were identified as independent risk factors related to an unfavorable clinical outcome. No difference in the remission rate of nephrotic syndrome was observed between treated and untreated patients (51% vs. 58%, p=NS).

CONCLUSION

Treatment with prednisolone and azathioprine seems to be of no long-term benefit in ameliorating the clinical course of nephrotic patients with membranous nephropathy. Thus, other therapeutic regimens including cyclophosphamide, chlorambucil or cyclosporin should be used in nephrotic IMN patients with poor prognostic features.

Transforming growth factor-beta1 SNPs: genetic and phenotypic correlations in progressive kidney insufficiency

Associations have been described between polymorphisms of cytokine and growth factor genes and susceptibility to, or progression of, an increasing number of diseases. TGF-beta1 plays an important role in the pathogenesis of experimental and clinical glomerulosclerosis and tubulointerstitial fibrosis. In this study, single nucleotide polymorphisms (SNPs) in the TGFbeta1 gene were investigated as possible markers for the progression of chronic kidney failure (CKF). 145 Caucasian patients with CKF were screened for four TGFbeta1 SNPs: T-509C in the promoter region; Arg25Pro and Leu10Pro in exon 1 and Thr263Ile in exon 5. There were significant differences between CKF patients and controls in allele frequencies of two of the SNPs, Leu10Pro (p = 0.038) and C-509T (p = 0.02) and in haplotype distributions (p = 0.0175), indicating an association with susceptibility to CKF. We also observed a significant association between progression of CKF and homozygosity for Arg25 (odds ratio 3.77, 95% confidence interval 1.57-9.04, p = 0.002). Homozygosity for Arg25 was also associated with severity of proteinuria at diagnosis (p = 0.038), plasma TGF-beta1 protein levels (p = 0.01), and severity of glomerulosclerosis (p = 0.04). Homozygosity for -509T was associated with severity of proteinuria at diagnosis (p = 0.0017), level of renal tubular TGF-beta1 immunostaining (p = 0.0006) and with severity of renal interstitial inflammatory cellular infiltration (p = 0.01). Tubular TGF-beta1 immunostaining was significantly higher in biopsies with inflammatory cellular infiltration compared those without inflammation (p = 0.0048). There was a significant difference in haplotype distributions between CKF patients with progressive, as opposed to non-progressive disease (p = 0.0484). TGFbeta1 SNPs may be useful prognostic indicators for the progression of CKF.

Elevated epsilon-(gamma-glutamyl)lysine in human diabetic nephropathy results from increased expression and cellular release of tissue transglutaminase

INTRODUCTION

Diabetic nephropathy (DN) is the leading cause of chronic kidney failure, however the mechanisms underlying the characteristic expansion of the extracellular matrix (ECM) in diabetic kidneys remain controversial and unclear. In non-diabetic kidney scarring the protein crosslinking enzyme tissue transglutaminase (tTg) has been implicated in this process by the formation of increased epsilon-(gamma-glutamyl)lysine bonds between ECM components in both experimental and human disease. Studies in db+/db+ diabetic mice and in streptozotocin-treated rats have suggested a similar mechanism, although the relevance of this to human disease has not been addressed.

METHODS

We have undertaken a retrospective analysis of renal biopsies from 16 DN patients with type 2 diabetes mellitus using an immunohistochemical and immunofluorescence approach, with tTg and epsilon-(gamma-glutamyl)lysine crosslink quantified by confocal microscopy.

RESULTS

Immunofluorescent analysis of human biopsies (confocal microscopy) showed increases in levels of tTg (+1,266%, p < 0.001) and epsilon-(gamma-glutamyl)lysine (+486%, p < 0.001) in kidneys with DN compared to normal. Changes were predominantly in the extracellular periglomerular and peritubular areas. tTg staining correlated with epsilon-(gamma-glutamyl)lysine (r = 0.615, p < 0.01) and renal scarring (Masson's trichrome, r = 0.728, p < 0.001). Significant changes in epsilon-(gamma-glutamyl)lysine were also noted intracellularly in some (< or =5%) tubular epithelial cells. This is consistent with cells undergoing a novel transglutaminase-mediated cell death process in response to Ca2+ influx and subsequent activation of intracellular tTg.

CONCLUSION

Changes in tTg and epsilon-(gamma-glutamyl)lysine occur in human DN. Cellular export of tTg may therefore be a factor in the perpetuation of DN by crosslinking and stabilisation of the ECM, while intracellular activation may lead to cell death contributing towards tubular atrophy.

Life-threatening envenoming by the Saharan horned viper (Cerastes cerastes) causing micro-angiopathic haemolysis, coagulopathy and acute renal failure: clinical cases and review

BACKGROUND

The desert horned vipers (Cerastes cerastes and C. gasperettii) are the most familiar snakes of the great deserts of North Africa and the Middle East, including the plains of Iraq. They are responsible for many human snake bites. In Western countries, they are popular among exotic-snake keepers.

AIM

To investigate mechanisms of life-threatening envenoming and treatment.

DESIGN

Clinical investigation.

METHODS

Clinical and laboratory studies with measurement of serum venom antigen concentrations by enzyme immunoassay.

RESULTS

Two men bitten while handling captive Saharan horned vipers (Cerastes cerastes) in Europe developed extensive local swelling and life-threatening systemic envenoming, characterized by coagulopathy, increased fibrinolysis, thrombocytopenia, micro-angiopathic haemolytic anaemia and acute renal failure. The clinical picture is explicable by the presence in C. cerastes venom of several thrombin-like, Factor-X-activating, platelet-aggregating, haemorrhagic and nephrotoxic components. In one case, prophylactic use of subcutaneous epinephrine may have contributed to intracranial haemorrhage. The roles in treatment of heparin (rejected) and specific antivenom (recommended) are discussed.

DISCUSSION

Cerastes cerastes is capable of life-threatening envenoming in humans. Optimal treatment of envenoming is by early administration of specific antivenom, and avoidance of ineffective and potentially-dangerous ancillary methods.

Impact of cardiac transplantation on kidney function: a single- center experience

Long-term follow-up of cardiac transplant recipients reveals a progressive decline in kidney function in a significant number of patients. This complication is one of the most important prognostic parameters for the outcome of cardiac transplantation. The risk factors implicated in the pathogenesis of renal dysfunction following cardiac transplantation are numerous, with the immunosuppressive drug cyclosporine (CsA) playing a major role. This case-control study was designed to evaluate the role of different risk factors among patients who had been transplanted at the Northern General Hospital Cardiothoracic Centre (CTC) with the possibility of identifying modifiable risk factors that mitigate the nephrotoxicity of CsA. Over a 10-year period, heart transplantation was performed in 205 patients at the CTC. Seventeen patients who experienced chronic renal failure (CRF) and were treated at the outpatient clinic of the Sheffield Kidney Institute were randomly selected from those who had >2-year graft survival and follow-up after cardiac transplantation. As controls, 15 cardiac transplant patients were randomly selected from 32 with comparable survival and follow-up after transplantation and without evidence of significant renal dysfunction (serum creatinine </=150 micromol/L). The putative risk factors for development of renal insufficiency were retrospectively studied as well as those affecting the rate of progression of CRF. Seventy-five percent of the progressors (cases) had ischemic cardiomyopathy compared with 10% of nonprogressors (controls) (P <.05). CsA trough levels during the follow-up period were higher among the nonprogressors compared with the progressors (P =.03). Follow-up systolic blood pressure revealed a statistically significant correlation with the slope of serum creatinine in the progressor group (r = -.515 and P <.05). At the time of transplantation, ischemic cardiomyopathy as an underlying diagnosis seems to be a detrimental factor, contributing to the pathogenesis of renal dysfunction after heart transplantation. CsA trough levels alone do not seem to discriminate between progressors and nonprogressors. A randomized controlled study may be required to evaluate the possibility of replacing or reducing CsA to the lowest possible dose in the early posttransplant period for the subset of patients with ischemic cardiomyopathy.

Early human renal allograft fibrosis: cellular mediators

BACKGROUND

The development of early renal interstitial fibrosis (IF) in renal allografts is likely to depend on multiple factors. We studied retrospectively renal biopsies from cadaveric human renal allografts, transplanted from 1996 to 1998, with the intention of detecting early fibrotic changes and determining the underlying cellular mediators. We studied 23 transplant patients whose 46 renal biopsies were analysed, including a donor biopsy taken routinely at implantation from each patient and 23 follow-up biopsies, taken as clinically indicated over a period of 3 months following transplantation.

METHODS

Histological evaluation of induction and progression of fibrosis relied on point count analysis of conventional (Masson's trichrome/MT) and immunohistochemical staining for collagen III and IV, and alpha-smooth muscle actin (alpha-SMA) as a marker of myofibroblast differentiation. Mast cells (MC) were counted in sections stained with an anti-human mast cells tryptase monoclonal antibody. Activated macrophages as well as total, helper and cytotoxic T-lymphocytes were identified on frozen sections by direct immunofluorescence using mouse anti-CD71, CD3, CD4 and CD8 antibodies respectively. Eosinophils (E) were counted in hematoxylin and eosin (HE)-stained sections. Changes in interstitial fibrosis (IF) scores were evaluated and correlated with myofibroblasts, MC, E and lympho-monocytic cells.

RESULTS

We noted a significant increase in IF over a 3 months period following transplantation. There was also a significant increase in alpha-SMA+ cells, MC and E counts from implantation to follow-up biopsies. Similarly, there was a significant increase in interstitial infiltration by T-lymphocytes (modal category = 2 versus 0, p = 0.012) but not by macrophages. MC at implantation and follow-up were found to be predictive of IF (immunostainable collagen III) at follow-up (R(2) = 0.510, p = 0.023 and p = 0.030). Further, the predictive value for total T-lymphocyte infiltration at follow-up was also significant (R(2) = 0.617, p = 0.036). A strong correlation was found between alpha-SMA+ cells and MC counts at implantation (r = 0.7259, p < 0.001) and in follow-up biopsies (r = 0.5183, p < 0.01). However, there was no correlation between E counts and either alpha-SMA+ cells or MC either at implantation or in follow-up biopsies. Based on changes in interstitial immunostainable alpha-SMA, our patients were divided arbitrarily into 2 groups; group 1 (n = 12) with >100% increase in alpha-SMA and group 2 (n = 11) with <100% increase. Group 1 patients differed significantly from group 2 regarding the degree of MC infiltration at follow-up (t = 0.4519, p < 0.05) with the mean increase in MC count from implantation to follow-up biopsies being +5.1 cells/high power field (HPF) in group 1 and +0.8 cell/HPF in group 2 (p = 0.0237). MC counts in group 1 were associated with a higher modal category (greater than one) of cytotoxic: helper T-lymphocytes ratio compared to group 2 (2:1 versus 1:1 respectively).

CONCLUSION

Multiple cells may contribute to early interstitial fibrosis in a subgroup of human renal allograft recipients with MC playing a major role.

Early progressive interstitial fibrosis in human renal allografts

BACKGROUND

Early fibrosis has been described in renal allografts and implicated in the progression of chronic allograft nephropathy (CAN). The precise factors implicated in the initiation and progression of early allograft fibrosis remain uncertain.

PATIENTS AND METHODS

We studied retrospectively 23 cadaveric renal allograft recipients over a 3-year period, who had paired renal biopsies (Bx) (at implantation and as clinically indicated) within 3 months of transplantation (Tx). Eight of them have progressed over an average period of 3.16 +/- 0.83 years to CAN. Histological evaluation of interstitial fibrosis (IF) relied on point count analysis of Masson's trichrome (MT) staining as well as immunostainable collagens III (iCol III) and IV (iCol IV). The severity of the IF scores was correlated with the clinical, biochemical and histological parameters. The nature and severity of the interstitial inflammatory infiltrate were also evaluated by immunofluorescence. In addition, patients were subdivided into those whose fibrosis progressed (> 50% increase in IF/iCol IlI; Group 1) and non-progressors (< 50% increase in fibrosis score; Group 2) in an attempt to determine discriminatory features.

RESULTS

In the whole group, there was a significant increase in the IF score, as estimated by MT staining and iCol III, from implantation to follow-up Bx (p = 0.0027 and p = 0.0088, respectively). The changes in iCol IV were not significant. Further, the increase in interstitial inflammatory infiltrate of total T lymphocytes, and not of macrophages, from implantation (modal category = 2) to follow-up (modal category = 0) was significant (p = 0.0121). The predictive value of such increase was significant (R2 = 0.617, p = 0.03). The donor's age (R2 = 0.892, p = < 0.0001), death from cerebrovascular accident (CVA) (R2 = 0.822, p = 0.047), as well as recipient's body weight (R2 = 0.892, p = 0.001), male gender (R2 = 0.687, p = 0.041) and elevated mean arterial pressure (MAP) (R2 = 0.892, p = < 0.0001) were all significant risk factors for early IF. Delayed graft function (DGF) proved to be a significant predictor of early IF (R2 = 0.822, p = 0.003) and became more significant in the presence of superimposed acute rejection (AR) (p = 0.0001). Proteinuria > 1 g/day (R2 = 0.882, p = 0.004) and hypertriglyceridemia > 2.25 mmol/l (R2 = 0.808, p = < 0.0001) were also associated with early IF. Of the implantation histological parameters, iCol III proved to be a highly significant predictor of early IF (R2 = 0.892, p = < 0.0001). Interestingly, the predictive value of iCol III for graft survival in terms of CAN was significant (Cox p = 0.088). Group 1 progressor patients (n = 10) were all males (p = 0.038) and received their kidneys from donors who died from CVAs in 90% of cases (p = 0.011). They had, compared to non-progressors, a lower cyclosporin A level (p = 0.047), a higher incidence of AR episodes (80% versus 54%), a higher serum creatinine at 10 days post-Tx (p = 0.005), a higher proteinuria (2.07 +/- 3.89 g/l vs 0.96 +/- 0.97 g/l, p = 0.041) and a higher serum triglyceride (2.48 +/- 1.37 mmol/l vs 1.69 +/- 0.81 mmol/l, p = 0.039) level. 8% of Group 1 patients had DGF compared to 30% in Group 2 (p = 0.023). Of note, the modal category of cytotoxic: helper T lymphocytes ratio was greater than 1 in Group 1 (2:1) patients and not in Group 2 (1:1).

CONCLUSION

Implantation histology, and in particular iCol III, is a predictor of early IF in a subgroup of patients with DGF and AR. Additional risk factors include hypertension, proteinuria and hypertriglyceridemia especially in patients receiving kidneys from older donors who died of CVAs.

Caspase-3 and apoptosis in experimental chronic renal scarring

BACKGROUND

Caspase-3 is a member of the caspase enzyme family, having a central role in the execution of apoptosis. However, the significance of Caspase-3 in the inappropriate and excessive apoptosis that contributes to the progression of non-immune-mediated renal scarring has not been established.

METHODS

Kidneys from sham-operated and subtotal nephrectomized (SNx) rats were harvested on days 7, 15, 30, 60, 90 and 120 post-surgery. These were analyzed for apoptosis (in situ end labeling of DNA, light and electron microscopy), Caspase-3 activity (fluorometric substrate cleavage assay), protein and mRNA (Western and Northern blotting), as well as distribution (immunohistochemistry), inflammation (ED-1 immunohistochemistry) and fibrosis (Masson's Trichrome staining).

RESULTS

Apoptosis, inflammation and fibrosis gradually increased in glomeruli, tubules and interstitium of SNx rats. Caspase-3 was mainly located in damaged tubules, but also was found in some glomerular and interstitial cells. Little or no staining was noted in sham-operated kidneys. In SNx kidneys, Caspase-3 activity was significantly increased from day 30 and peaked on day 120 (2.5-fold). This resulted from increases in the 17 and 24 kD active protein subunits. The 32 kD precursor was increased at all time points (1861% on day 120, P < 0.01). Caspase-3 changes were transcription-dependent with the 2.7 kb caspase-3 mRNA significantly increased at all time points (287% on day 120). Caspase-3 activity was a better predictor of apoptosis (Std beta coefficient = 0.347, P < 0.05) than Caspase-3 proteins or mRNA; however, Caspase-3 at all levels correlated with apoptosis, inflammation and fibrosis (all P < 0.01).

CONCLUSIONS

Up-regulation of apoptosis in remnant kidneys is likely to be Caspase-3-dependent as it is associated with increases in Caspase-3 at the activity, protein and mRNA levels. Therefore, Caspase-3 is a potential therapeutic target for the modification of renal cell apoptosis and subsequently renal fibrosis.

Analysis of the association between diabetic nephropathy and polymorphisms in the aldose reductase gene in Type 1 and Type 2 diabetes mellitus

AIMS

To investigate the association between polymorphisms of the aldose reductase gene and diabetic nephropathy in both Type 1 and Type 2 diabetes mellitus, and to carry out a meta-analysis of published results.

METHODS

We have investigated the role of two aldose reductase polymorphisms in four independent cohorts of cases and controls (two each with Type 1 and Type 2 diabetes) drawn from two ethnic populations, including 471 patients with nephropathy and 494 control diabetic patients without nephropathy. A C/T transition at position -106, and a (CA)n microsatellite marker 2.1 kb from the start site of the aldose reductase gene were genotyped in nephropathic patients and non-nephropathic controls from each cohort.

RESULTS

Carriage of the -106 T allele was significantly associated with diabetic nephropathy in three of the four study groups. The Mantel-Haenszel combined odds ratio was 2.22 (95% CI 1.69, 2.94), P = 1.05 x 10(-8). We found no evidence for association of the microsatellite marker with nephropathy, despite moderate levels of disequilibrium between the two markers. Meta-analysis of published data yielded no evidence for association of the microsatellite marker with diabetic nephropathy in Type 2 diabetes, but varying degrees of association with diabetic nephropathy in Type 1 diabetes.

CONCLUSIONS

Meta-analyses provide more convincing evidence of a role for the ALR2-106 marker than for the microsatellite marker in diabetic nephropathy (DN). More studies are now required to confirm these results and to establish whether the ALR2-106 polymorphism has a functional role in DN.

Role of stem cell factor and mast cells in the progression of chronic glomerulonephritides

BACKGROUND

Mast cells (MCs) have been implicated in the pathogenesis of atherosclerosis and tissue fibrosis. However, the role of MC in the development of renal fibrosis has not been fully elucidated. Stem cell factor (SCF; the ligand for MC c-kit receptor) is thought to attract and activate MCs.

METHODS

The intensity of MC infiltration and SCF expression in renal biopsies from 56 patients with different forms of primary and secondary glomerulonephritis and five controls were investigated by immunohistochemistry, using a monoclonal anti-human MC tryptase antibody and a polyclonal antihuman SCF antibody.

RESULTS

A large number of MCs were detected in the renal interstitium of the diseased kidneys. Immunostainable SCF was detected in tubular as well as interstitial cells. MC infiltration was significantly higher in glomerulonephritis (16.9 +/- 10.2 cells/field) compared with controls (2.8 +/- 2.1 cells/field, P = 0.03). Similarly, immunostainable SCF was 0.6 +/- 0.3% for controls and 3.3 +/- 2.1% in the glomerulonephritis group (P = 0.02). MC infiltration was highly correlated with SCF expression in diseased kidneys (r = 0.93, P = 0.0001). Double immunostain showed them to colocalize in some interstitial cells. Analysis of MC proliferation [proliferating cell nuclear antigen (PCNA) positivity] and apoptosis (in situ end labeling of DNA) showed these cells to be terminally differentiated. Both MCs and SCF were correlated with interstitial fibrosis (R = 0.71 for MC and R = 0.62 for SCF, P = 0.0001) and interstitial alpha-smooth muscle actin (R = 0.69 for MC and R = 0.60 for SCF P = 0.0001). Using regression analysis, the number of MC infiltration was found to be a very powerful determinant of interstitial fibrosis in the glomerulonephritis group (R2 = 91.4%).

CONCLUSION

MCs as an infiltrating hematopoietic cell and its growth factor (SCF) seem to be up-regulated in glomerulonephritis, and may play a role in the development of renal fibrosis.

Increases in renal epsilon-(gamma-glutamyl)-lysine crosslinks result from compartment-specific changes in tissue transglutaminase in early experimental diabetic nephropathy: pathologic implications

Diabetic nephropathy (DN) is characterized by an early, progressive expansion and sclerosis of the glomerular mesangium leading to glomerulosclerosis. This is associated with parallel fibrosis of the renal interstitium. In experimental renal scarring, the protein cross-linking enzyme, tissue transglutaminase (tTg), is up-regulated and externalized causing an increase in its crosslink product, epsilon-(gamma-glutamyl)-lysine, in the extracellular space. This potentially contributes to the extracellular matrix (ECM) accumulation central to tissue fibrosis by increasing deposition and inhibiting breakdown. We investigated if a similar mechanism may contribute to the ECM expansion characteristic of DN using the rat streptozotocin model over 120 days. Whole kidney epsilon-(gamma-glutamyl)-lysine (HPLC analysis) was significantly increased from Day 90 (+337%) and peaked at Day 120 (+650%) (p < 0.05). Immunofluorescence showed this increase to be predominantly extracellular in the peritubular interstitial space, but also in individual glomeruli. Total kidney transglutaminase (Tg) was not elevated. However, using a Tg in situ activity assay, increased Tg was detected in both the extracellular interstitial space and glomeruli by Day 60, with a maximal 53% increase at Day 120 (p < 0.05). Using a specific anti-tTg antibody, immunohistochemistry showed a similar increase in extracellular enzyme in the interstitium and glomeruli. To biochemically characterize glomerular changes, glomeruli were isolated by selective sieving. In line with whole kidney measurement, there was an increase in glomerular epsilon-(gamma-glutamyl) lysine (+361%); however, in the glomeruli this was associated with increases in Tg activity (+228%) and tTg antigen by Western blotting (+215%). Importantly, the ratio of glomerular epsilon-(gamma-glutamyl) lysine to hydroxyproline increased by 2.2-fold. In DN, changes in the kidney result in increased translocation of tTg to the extracellular environment where high Ca(2+) and low GTP levels allow its activation. In the tubulointerstitium this is independent of increased tTg production, but dependent in the glomerulus. This leads to excessive ECM cross-linking, contributing to the renal fibrosis characteristic of progressive DN.

Differential expression of suppressors of cytokine signalling genes in response to nutrition and growth hormone in the septic rat

GH treatment during critical illness and sepsis may increase mortality. A family of negative regulators of cytokine signalling, the suppressors of cytokine signalling (SOCS), have been characterised. SOCS provide a mechanism for cross-talk between the cytokine receptors, including GH. Here, we have investigated the impact of nutrition and GH treatment on GH receptor, SOCS1, SOCS-2, SOCS-3 and cytokine-inducible SH2-containing protein (CIS) hepatic mRNA expression in a rat model of sepsis, caecal ligation and puncture (CLP). Four groups of rats were studied: control (food given ad libitum, n=7), CLP only (n=8), CLP and total parenteral nutrition (TPN) (n=9), and CLP, TPN and GH (n=10). CLP rats underwent surgery and 18 h later received saline or TPN or TPN+GH for 6 h before they were killed. Serum IGF-I levels were lower in all CLP groups (P<0.001). The combination of TPN and GH treatment increased IGF-I levels compared with the saline-treated CLP rats (P<0.01), but IGF-I levels remained lower than control animals (P<0.001). GH receptor and GH-binding protein expression in liver was reduced in animals subjected to CLP and was unaffected by nutrition or GH treatment. Hepatic SOCS-1 was detectable in normal rats, induced in all CLP animals but was unaffected by nutrition and GH. Hepatic SOCS-2 expression was difficult to detect in normal and CLP rats but was greatly induced in CLP rats treated with GH. Hepatic SOCS-3 expression was only just detectable in the control group but was elevated in all CLP groups and unaffected by nutrition and GH. Hepatic CIS expression was difficult to detect in normal rats, was not induced by CLP but was induced by both nutrition and GH. In conclusion, CLP induced low IGF-I levels associated with increased expression of SOCS-1 and SOCS-3, both of which are known to inhibit GH receptor signalling. GH induced SOCS-2 and CIS in the CLP rat despite resistance with respect to IGF-I generation, and parenteral feeding induced CIS in the CLP rat. Thus, there is potential for a complex interaction between GH and cytokine signalling at the level of SOCS expression whereby the inflammatory response may alter GH signalling and GH may influence the inflammatory response.

Transforming growth factor-beta(1) and myofibroblasts: a potential pathway towards renal scarring in human glomerular disease

BACKGROUND/AIMS

The cellular and humoral factors involved in the development and progression of renal scarring have not been fully investigated. Transforming growth factor-beta (TGF-beta(1)) is considered to be the main fibrogenic growth factor and it is implicated in the pathogenesis of renal fibrosis in experimental and clinical nephropathies. On the other hand, collagen III is an important component of the extracellular matrix. In this study we attempted to identify any possible links between TGF-beta(1) and collagen III synthesis and expression with the expression of myofibroblasts in the evolution of renal scarring in human glomerular diseases.

METHODS

We studied retrospectively 40 patients with various types of primary and secondary glomerulonephritis (GN), with either proliferative or nonproliferative pattern, with emphasis on the renal synthesis of TGF-beta(1) and collagen III (detected by in situ hybridization) and their expression (detected by immunohistochemistry) as well as myofibroblast expression. The possible links of TGF-beta(1) expression with myofibroblast distribution (alpha-smooth muscle actin, alpha-SMA(+) cells) and with conventional histopathology and renal function was also examined.

RESULTS

TGF-beta(1) protein and mRNA were detected in the renal tubular epithelial cells and interstitium and to a lesser extent within glomeruli of patients with GN. Collagen III was mainly detected in the interstitium (peritubular and periglomerular areas) and to a lesser extent in the glomeruli. Messenger RNA for collagen III followed a similar peritubular and periglomerular distribution to that of TGF-beta(1) and alpha-SMA(+) interstitial cells. The intensity of interstitial TGF-beta(1) protein expression was significantly related to the degree of interstitial fibrosis (r = 0.628, p < 0.01), tubular atrophy (r = 0.612, p < 0.01), interstitial collagen III expression (r = 0.478, p < 0.05), and serum creatinine values (r = 0.722, p < 0.001). Also there was a close positive correlation between the severity of interstitial myofibroblast expression and interstitial TGF-beta(1) (r = 0.412, p < 0.05), as well as collagen III (r = 0.409, p < 0.05). In addition, a significant correlation was found between glomerular TGF-beta(1) expression and severity of glomerulosclerosis (r = 0.620, p < 0.01).

CONCLUSION

The results of this study suggest that TGF-beta(1) plays an important role in the pathogenesis of fibrosis developing in human kidney, during the evolution of glomerular disease. Interstitial myofibroblasts may contribute to interstitial fibrosis through the synthesis and release of both TGF-beta1 and collagen III.

Effects of adenosine receptor antagonists on the responses to contrast media in the isolated rat kidney

Contrast media can induce both a decrease in renal blood flow and a reduction in glomerular filtration rate (GFR) when administered to both experimental animals and humans. In the present study we have examined the role of adenosine in mediating these effects using the isolated perfused rat kidney. Kidneys were perfused with a 6. 7%-(w/v)-albumin-based perfusate supplemented with glucose and amino acids (n=6 per group). They were exposed to diatrizoate [20 mg of iodine (mgI)/ml; osmolality 1650 mOsm/kg of water] or iotrolan (20 mgI/ml; osmolality 320 mOsm/kg of water) in the presence or absence of theophylline (10.8 microg/ml), or to diatrizoate in the presence or absence of a specific adenosine A(1) receptor antagonist (KW-3902; 2 microg/ml) or a specific A(2) receptor antagonist (KF17837; 6 microg/ml). Diatrizoate (n=6) produced a fall in GFR from 0.65+/-0.04 to 0.42+/-0.03 ml.min(-1).g(-1) (P<0.05); renal perfusate flow (RPF) also declined, from 36.5+/-3.8 to 22.0+/-3.2 ml. min(-1).g(-1) (P<0.05). Iotrolan (n=6) produced a fall in GFR from 0. 64+/-0.02 to 0.48+/-0.04 ml.min(-1).g(-1) (P<0.05) and in RPF from 33.3+/-3.8 to 24.0+/-3.0 ml.min(-1).g(-1) (P<0.05). Theophylline (10.8 microg/ml) prevented the fall in GFR caused by either diatrizoate (baseline, 0.63+/-0.05 ml.min(-1).g(-1); diatrizoate+theophylline, 0. 60+/-0.04 ml.min(-1).g(-1)) or iotrolan (baseline, 0.64+/-0.04 ml. min(-1).g(-1); iotrolan+theophylline, 0.67+/-0.05 ml.min(-1).g(-1)), but did not affect the decreases in RPF caused by either agent. KW-3902 (2 microg/ml) also prevented the fall in GFR produced by diatrizoate (baseline, 0.66+/-0.05 ml.min(-1).g(-1); diatrizoate+KW-3902, 0.61+/-0.05 ml.min(-1).g(-1)), while the fall in RPF remained unaffected. KF17837 (6 microg/ml) had no effect on the decreases in either GFR or RPF induced by diatrizoate (n=6 per group). The results suggest a role for adenosine acting at the A(1) receptor in mediating the decrease in GFR induced by contrast media. This effect is independent of a change in renal vascular resistance, and possibly secondary to mesangial cell contraction causing a decrease in the ultrafiltration coefficient.

Interferon-gamma inhibits experimental renal fibrosis

Interferon-gamma inhibits experimental renal fibrosis.

BACKGROUND

Recent evidence has implicated myofibroblasts as a cell type responsible for the laying down of extracellular matrix components during fibrosis in a number of organs. In this study, we examined the capacity of interferon-gamma (IFN-gamma) to inhibit the activation of fibroblasts to the myofibroblastic phenotype and hence reduce the extent of renal scarring in the rat subtotal nephrectomy (SNx) model using a novel method of intrarenal delivery.

METHODS

Rats were divided into four groups: sham, SNx (group 1), SNx + drug vehicle (group 2) and SNx + IFN-gamma (400 units/day; group 3) for 30 days. Rats were sacrificed on days 15, 30, 45, and 90 following SNx.

RESULTS

Clinical data showed a marked reduction in proteinuria in the group treated with IFN-gamma (161 vs. 280 mg/24 hr by day 45, P < 0.01) and a preservation of the creatinine clearance (1.16 vs. 0. 84 ml/min by day 45, P < 0.05) when compared to the SNx or SNx + vehicle groups throughout the time course. Immunohistochemical staining for alpha-smooth muscle actin (alpha-SMA) revealed a reduction in myofibroblastic cell types (6.5 +/- 3.1% glomerular alpha-SMA in group 3 compared with 14.8 +/- 4.2% glomerular alpha-SMA in group 2, P < 0.05, 3.8 +/- 1.4% tubulointerstitial alpha-SMA in group 3 compared with 8.8 +/- 2.0% tubulointerstitial alpha-SMA in group 2 on day 45, P < 0.05). There was also a reduction in immunostaining for collagens III and IV in the IFN-gamma-treated group. Scoring for both glomerulosclerosis and tubulointerstitial fibrosis in the IFN-gamma group (group 3) was lower than the other two operated groups.

CONCLUSIONS

We conclude that IFN-gamma, administered at a dose of 400 units/day, has a strong inhibitory effect on myofibroblasts and that as a possible result of this action, renal fibrosis is reduced and renal function is preserved in the rat SNx model. The IFN-gamma renoprotective effect lasted only for the extent of its administration and subsided when discontinued.

Transglutaminase transcription and antigen translocation in experimental renal scarring

It was recently demonstrated that renal tissue transglutaminase (tTg) protein and its catalytic product the epsilon(gamma-glutamyl) lysine protein cross-link are significantly increased in the subtotal (5/6) nephrectomy model (SNx) of renal fibrosis in rats. It was proposed that the enzyme had two important physiologic functions in disease development; one of stabilizing the increased extracellular matrix (ECM) by protein cross-linking, the other in a novel form of tubular cell death. This study, using the same rat SNx model, demonstrates first by Northern blotting that expression of tTg mRNA when compared with controls is increased by day 15 (+70% increase, P < 0.05), then rises steadily, peaking at day 90 (+391%, P < 0.01), and remains elevated at 120 d (+205%, P < 0.05) when compared with controls. In situ hybridization histochemistry demonstrated that the tubular cells were the major site of the additional tTg synthesis. Immunohistochemistry on cryostat sections revealed a sixfold increase (P < 0.001) in ECM-bound tTg antigen at 90-d post-SNx, whereas in situ transglutaminase activity demonstrated by the incorporation of fluorescein cadaverine into cryostat sections indicated a 750% increase (P < 0.001) on day 90 in SNx animals. This increased activity was extracellular and predominantly found in the peritubular region. These results indicate that increased tTg gene transcription by tubular cells underlies the major changes in renal tTg protein reported previously in SNx rats, and that the presence of the epsilon(gamma-glutamyl) lysine cross-links in the extracellular environment is the result of the extracellular action of tTg. These changes may be in response to tubular cell injury during the scarring process and are likely to contribute to the progressive expansion of the ECM in renal fibrosis.

Effects of transforming growth factor-beta1 on renal extracellular matrix components and their regulating proteins

Transforming growth factor-beta1 (TGF-beta1) is widely regarded as a potent fibrogenic renal growth factor. In cell culture, TGF-beta1 has been shown to increase various extracellular matrix (ECM) proteins and tissue inhibitors of metalloproteinases (TIMP), while decreasing matrix metalloproteinases (MMP), providing the optimum environment for progressive ECM accumulation. This study, which uses the isolated perfused rat kidney (IPRK), describes for the first time in a whole kidney preparation the action of TGF-beta1 on factors associated with ECM processing. This model allows the study of the intact rat kidney with physiologic cell-cell interactions in the absence of confounding systemic influences. Left kidneys were removed from male Wistar rats by a nonischemic technique and perfused with a sterile, apyrogenic, endotoxin-free perfusate, based on the plasma volume expander Hemaccel (polygeline), at constant pressure in a recirculating IPRK system. Kidneys were perfused for 1 h either with (n = 3) or without (n = 3) recombinant human TGF-beta1 (20 ng/ml). The effects of perfusion were controlled by comparison with the nonperfused contralateral kidney (n = 6). TGF-beta1 was measured in the perfusate and urine, at the start and end of the experiment using an enzyme-linked immunosorbent assay to its biologically active form. After perfusion, sections of the kidneys were analyzed for changes in mRNA by Northern blotting. Significant increases in mRNA for fibronectin (7.5-fold, P < 0.01), heparan sulfate proteoglycan core protein (53-fold, P < 0.001), laminin beta1 (12-fold, P < 0.001), collagen alpha1(IV) (17-fold, P < 0.001), collagen alpha1(III) (fourfold, P < 0.001), and MMP9 (twofold, P < 0.05) were observed after perfusion with TGF-beta1. Measurement of TIMP1, TIMP2, TIMP3, MMP1, and MMP2 mRNA demonstrated no detectable change, whereas determination of mRNA for tissue transglutaminase, an enzyme capable of cross-linking many ECM components, showed an eightfold increase (P < 0.01). This study suggests that in the IPRK and in the absence of other exogenous growth factors, TGF-beta1 selectively increases the synthesis of ECM and tissue transglutaminase without changes that would result in the reduction of ECM degradation.

The effects of dose, nutrition, and age on hexarelin-induced anterior pituitary hormone secretion in adult patients on maintenance hemodialysis

Malnutrition is common in chronic renal failure (CRF) and adversely affects prognosis. In view of the anabolic action of GH in CRF, we have studied the effects of hexarelin, a GH secretagogue, on CRF. An iv dose-response study in six 20- to 40-yr-old well nourished hemodialysis (HD) patients was followed by administration of the maximally effective dose to six 20- to 40-yr-old healthy controls, six 20- to 40-yr-old poorly nourished HD patients, and six 50- to 70-yr-old poorly nourished HD patients. GH secretion (area under the curve over 180 min, mean +/- SE) after 2 and 1 microg/kg doses (10.7 +/- 4.2 and 8.2 +/- 5.2 min/U x L, respectively) was greater than after placebo (0.60 +/- 0.11 min/U x L; P < 0.001 and P < 0.05, respectively). The most effective dose (2 microg/kg) produced similar GH secretion (11.4 +/- 3.3 min/U x L) in controls. GH secretion in the younger poorly nourished HD group (19.0 +/- 4.4 min/U x L) was not significantly different from that in the well nourished 20- to 40-yr-old HD patients (P = 0.06). GH secretion in the older, poorly nourished HD patients (9.4 +/- 2.2 min/U x L) was similar to that in the young, poorly nourished group (P = 0.18). ACTH and cortisol concentrations increased in all groups, whereas PRL concentrations were not affected in CRF. The profound action of hexarelin on GH secretion has been shown to extend to CRF. Trends were evident toward increasing efficacy in malnourished subjects and decreasing efficacy with age. Further studies are required to determine whether the acute actions of hexarelin can be translated into long term anabolic changes.

Cellular apoptosis and proliferation in experimental renal fibrosis

BACKGROUND

The progression of chronic renal failure (CRF) is associated with the progressive deletion of renal cells along with the fibrosis of the kidney. We have studied the role of programmed cell death (apoptosis) in the progression of experimental CRF and renal scarring.

METHODS

The sub-total (5/6th) nephrectomy (SNx) model of CRF was studied in adult male Wistar rats, with renal tissue collected from experimental and control animals on days 7, 15, 30, 60, 90, and 120 post SNx (n = 6 per group). These were examined for morphological signs of apoptosis by light and electron microscopy. Further, we stained the nuclear chromatin by the acridine orange fluorescent method and detected signs of DNA cleavage by endonucleases via the principal of TUNEL staining (ApopTag). Rates of cellular proliferation were measured simultaneously by immunohistochemical staining for the proliferating cell nuclear antigen (PCNA). In addition, cell division was monitored by counting of morphologically mitotic motifs detectable by light microscopy.

RESULTS

Progressive renal insufficiency associated with glomerulosclerosis and tubulointerstitial fibrosis took place in the majority of SNx rats. In these animals, we noted a marked and progressive increase in the number of apoptotic glomerular, tubular as well as interstitial cells. The most significant apoptotic changes were seen in the tubules of remnant kidneys peaking at day 120 post-SNx. At this stage, the increase in apoptosis compared to controls was 10.33+/-2.67 (M+/-SEM) fold for glomerular cells (P< or =0.006), 26.20+/-4.56 fold for tubular cells (P < 0.0001) and 4.66+/-0.81 fold for interstitial cells (P< or =0.001). Parallel changes in the number of PCNA positive renal cells were observed. Maximal PCNA staining was seen at day 120 when the increase with respect to controls was 14.00+/-4.93 fold (P< or = 0.05) for glomerular cells, 60.01+/-12.20 fold (P< or =0.05) for tubular cells and 28.59+/-4.45 fold (P< or = 0.05) for interstitial cells. As expected, the number of cells undergoing division and detectable by conventional light microscopy was lower at any time point to those expressing PCNA. We also observed a close correlation between the severity of tubular atrophy and tubulointerstitial fibrosis with the rate of tubular apoptosis (r=0.970, R2 =0.941, P< or =0.001).

CONCLUSIONS

We have shown a time-dependent increase in apoptosis and PCNA antigen positive staining in the sub-total nephrectomy model of chronic renal failure correlating with the progression of renal fibrosis. PCNA staining did not match analysis for mitosis and was considered to overestimate the number of proliferating cells in the tissue. With this reservation in mind and taking into account the relative time-frames in vivo of apoptosis and proliferation; apoptosis potentially outweighs proliferation by a factor of 2 8-fold, when examined over the same time period. Consequently, even small changes in the finite numbers of apoptotic cells become highly significant. Our results have shown the definite role of apoptosis within progression of renal damage and highlighted how it may contribute to the progression of tubular atrophy and play a role in the pathogenesis of tubulo-interstitial scarring.

Myofibroblasts and the progression of crescentic glomerulonephritis

BACKGROUND

The cellular and humoral factors involved in the pathogenesis of glomerulosclerosis and renal fibrosis following a crescentic glomerulonephritis have not been fully elucidated. Myofibroblasts and transforming growth factor-beta (TGF-beta) have been implicated in the development of experimental and clinical renal fibrosis. We have attempted to identify these mediators in crescentic glomerulonephritis and determine their role in the progression of the disease.

PATIENTS AND METHODS

We studied retrospectively 21 patients with crescentic and necrotizing glomerulonephritis (CNG) with emphasis on the renal expression (detected by immunohistochemistry) of myofibroblasts (alpha-smooth muscle actin+ cells), TGF-beta and collagen (III and IV) as well as their relationship with the clinical outcome of these patients. In situ hybridization histochemistry was applied to determine the site of synthesis of TGF-beta1 and collagen III. All the patients were treated by immunosuppression and followed up for a median period of 14 months.

RESULTS

Myofibroblasts and TGF-beta were detected in the crescents as well as in the periglomerular and tubulointerstitial areas in CNG biopsies. TGF-beta1 was also detected within renal tubular cells. The percentage of glomeruli with fibrotic and fibrocellular crescents was positively correlated with the severity of Bowman's capsule disruption (r = 0.631, P < 0.01) and with the intensity of myofibroblast expression in the interstitium (r = 0.504, P < 0.05). Strong interstitial immunostain for myofibroblasts and TGF-beta was also noted in association with interstitial fibrosis. In situ hybridization revealed the site of synthesis of TGF-beta1 to be the renal tubular cells of patients with CNG. By contrast, the site of synthesis of collagen III appeared to be confined to interstitial cells surrounding vessels, tubules and the glomeruli in a distribution identical to that of myofibroblasts. There was a significant positive correlation between the number of interstitial alpha-SMA+ cells and both interstitial TGF-beta (r = 0.591, P < 0.01) and interstitial collagen IV (r = 0.588, P < 0.01). In addition, the number of interstitial alpha-SMA+ cells and the extent of immunostain for collagen IV were positively correlated with the final serum creatinine (r = 0.517, P < 0.05 and r = 0.612, P < 0.01 respectively) and partially predicted functional outcome (R2 = 26.7% and 37.5% respectively) as well as the response to treatment. An association was observed between periglomerular myofibroblasts and the generation of fibrotic and fibrocellular crescents.

CONCLUSION

These observations suggest a causal link between myofibroblasts and fibrotic crescent formation. We also believe that interstitial myofibroblasts are actively involved in the pathogenesis of interstitial fibrosis in CNG.

Nutritional assessment of children on haemodialysis: value of IGF-I, TNF-alpha and IL-1beta

BACKGROUND

Protein-energy malnutrition (PEM) is associated with increased morbidity and mortality in haemodialysis (HD) patients. Insulin-like growth factor I (IGF-I) has proved to be a sensitive marker of malnutrition, while interleukin-1 (IL-1beta) and tumour necrosis factor (TNF) have been found to be raised in catabolic states.

METHODS

We have investigated the nutritional status of 17 chronic renal failure (CRF) paediatric patients (8 boys, 9 girls) on maintenance HD. Eight predialysis CRF children (5 boys and 3 girls; mean creatinine 5.1+/-3.2 mg/dl) and 10 healthy children served as control groups. PEM was defined according to anthropometric measurements (triceps skinfold thickness (TST), mid-arm circumference (MAC), and mid-arm muscle circumference (MAMC)). These were correlated with serum IGF-I, IL-1, TNF-alpha, transferrin, and albumin (all sampled before the HD session).

RESULTS

In the HD group, TST was reduced in 41.2% of the patients, whereas MAC and MAMC were reduced in 82.4 and 76.5% respectively. TST was depleted in only one of the predialysis CRF children. The degree of reduction in MAC and MAMC were 62.5 and 62.5% respectively. Median serum IGF-I level was decreased in both HD and predialysis CRF patients (205.1 interquartile range (IQR) 194.4 microg/l and 258.8 IQR 155.0 microg/l respectively) compared to the healthy children (418.0 IQR 310.5 microg/l) (P=0.0009 and P=0.01 respectively). Within the HD group, IGF-I levels were lower in patients with malnutrition defined according to TST (145.0 IQR 125.5 microg/l) compared to children with normal TST (301.2 IQR 218.8 microg/l) (P=0.05). IGF-I levels of the HD patients with malnutrition according to TST was also lower than the predialysis CRF patients and healthy children (P=0.04 and P=0.002 respectively). Serum IL-1beta was undetectable in all groups. Median serum TNF-alpha levels were higher in HD and predialysis CRF patients compared to healthy children, albeit statistically insignificant. There was no correlation between TNF-alpha, transferrin or albumin and anthropometric parameters.

CONCLUSIONS

Our results support the high prevalence of malnutrition in CRF children, which becomes more pronounced when treatment by HD is initiated. We suggest that determination of IGF-I levels in childhood HD patients in conjunction with anthropometric measurements is useful for identification of malnutrition. We have not been able to demonstrate the catabolic effects of cytokines on this state of protein energy malnutrition.

Expression of cytoskeletal proteins differentiates between progressors and non-progressors in treated idiopathic membranous nephropathy

Myofibroblasts play an important role in wound healing in a variety of tissue injuries. They have also been implicated in tissue fibrosis including renal scarring. This study was aimed at defining their role in one of the commonest forms of nephrotic syndrome in adults, namely membranous nephropathy. We have studied 21 patients with biopsy proven idiopathic membranous nephropathy who were treated with glucocorticoids, attempting to define the role of myofibroblasts (alpha-smooth muscle actin-positive as well as vimentin-positive cells) in the progression of this form of nephropathy. There were 13 non-progressors (NP) and 8 progressors (P). The clinical, histological, and immunohistochemical characteristics of both groups were compared. Immunohistochemical staining for myofibroblasts cytoplasmic markers a-smooth muscle actin (alpha-SMA) and vimentin relied on an avidin-biotin-peroxidase method. The level of blood pressure, degree of proteinuria, severity of interstitial infiltrate and interstitial fibrosis did not differentiate P from NP. However, vascular sclerosis was more severe in P compared to NP (p < 0.016) and its severity predicted the subsequent functional outcome (slope of the 1/serum creatinine against time; r2 = 0.618, p < 0.01). Mesangial alpha-SMA was significantly higher in P (31 +/- 18.6%) than in NP (14.5 +/- 9.8%), p < 0.015. Interstitial alpha-SMA immunostain was also higher in P but did not reach statistical significance. However, the number of interstitial myofibroblasts (alpha-SMA positive cells) closely predicted the subsequent rate of the progression of chronic renal failure (r2 = 0.919, p < 0.0001). Mesangial vimentin expression was not different between both groups. By contrast, interstitial vimentin immunostain was higher in P (19.1 +/- 8.8%) compared to NP (7.9+/-5.6 %), p < 0.002. These data suggest that the expression of mesangial and interstitial cytoskeletal proteins (alpha-SMA and vimentin) may have useful prognostic implications as they appear to differentiate between patients with membranous nephropathy who respond to immunosuppression and those who continue to progress.

Progression to renal failure after nephrotoxic nephritis in rats studied by renal transplantation

We studied the relation between immunopathology and progressive renal failure after nephrotoxic nephritis (NTN) in rats. Thirty days after induction of nephritis by injection of rabbit anti-rat nephrotoxic serum, pairs of kidneys from 13 nephritic rats were transplanted into separate syngeneic recipients, one of whom had been pre-immunized with rabbit immunoglobulin G (IgG) whilst the other was naive. Progression to renal failure of the transplanted nephritic kidney was studied after removal of the recipient's own kidneys; results from right and left kidney from a single donor in pre-immunized and naive recipients were compared. There were substantial differences in autologous anti-rabbit IgG titres in naive and preimmunized recipients; despite this pairs of kidneys from the same donor had almost identical courses as assessed by proteinuria, serum creatinine and graft survival. There was substantial variation in survival of kidneys from different donors. But there were very strong correlations of graft survival with proteinuria (r = 0.97, t = 4.443, P less than 0.001) and reciprocal serum creatinine (r = 0.95, t = 4.32, P less than 0.001) in donors shortly before transplantation. We conclude that autologous antibody titres did not influence the progression to renal failure after nephrotoxic nephritis. The rate of progression was already determined at the time of transplantation.

Selective effect of low protein diets in chronic renal diseases

It has recently been established that the rate of progression of chronic renal failure in man can be slowed by restricting dietary protein. Consequently, the short term and long term effects of a low protein diet on the course of different chronic nephropathies were studied in an attempt to delineate the factors that determine the response to such a diet. When a low protein diet was given for six months renal function improved significantly in nine patients with chronic tubulointerstitial nephritis (p less than 0.025); the diet had a marginally beneficial effect in 12 patients with chronic glomerulonephritis (p less than 0.05) and no effect in nine with hypertensive nephrosclerosis. The heterogeneous functional response in the patients with chronic glomerulonephritis correlated closely with the effect of the diet on these patients' proteinuria (r = 0.76, p less than 0.01). In a short term study (four weeks) of 12 patients with chronic renal failure changes in renal plasma flow were proportional to dietary protein intake. Renal vascular resistance fell during a high protein diet and increased when dietary protein was restricted. The changes in renal plasma flow during the low protein diet correlated well with the patients' long term functional response to the diet (r = 0.76, p less than 0.01). It is concluded that the response to a low protein diet in chronic renal failure is determined, firstly, by the nature of the underlying nephropathy, with maximal benefit being observed in non-glomerular disorders; secondly, by the effect of the diet on the proteinuria in chronic glomerulonephritis; and, thirdly, by the haemodynamic response to the diet, with patients with a reactive renal vascular bed improving with a low protein diet.

Captopril in hypertension after renal transplantation

Eight hypertensive renal allograft recipients who had received captopril are presented. Captopril in a maximal daily dose of 250 mg enabled the withdrawal of large doses of beta-blocking agents and vasodilators. Blood pressure was satisfactorily controlled in all except one. No adverse side effects were observed other than the 'first dose' effect which resulted in transient anuria in one patient. Captopril appears to be a useful agent in the management of severe hypertension after renal transplantation.