Glomerular hypertrophy in minimal change disease predicts subsequent progression to focal glomerular sclerosis

Glomerular size and glomerulosclerosis in Australian aborigines

We have previously described the prevalence of glomerulomegaly in biopsy specimens from Australian Aborigines with renal disease, a phenomenon documented in a number of other indigenous populations. Many of the biopsy specimens showed variable degrees of focal and segmental glomerulosclerosis (FSGS). Correlations between glomerular size and FSGS have been described in various animal models, as well as studies of humans. The aim of this study is to determine whether a relation exists between glomerular volume and severity of FSGS in biopsy specimens from Australian Aboriginals in the Northern Territory and Aboriginal inhabitants of the Tiwi Islands (Bathurst Island and Melville Island, Northern Territory, Australia). Consecutive clinical biopsy specimens were obtained from 78 non-Tiwi and 72 Tiwi Aboriginals. Glomerular volume was estimated using the stereological method of Weibel and Gomez. FSGS was graded from 0 to 4; 0 indicates no sclerosis and 4 indicates severe sclerosis. A biphasic relationship between glomerular size and severity of FSGS was identified. As the severity of FSGS increased from grade 0 to grade 3, glomerular size also increased. For both populations studied, glomeruli scored as grades 1, 2, and 3 were approximately 50% (P< 0.001), 65% (P< 0.001), and 100% (P< 0.001) larger than normal glomeruli, respectively. However, in glomeruli with grade 4 FSGS, glomerular size decreased to the size of normal glomeruli. These results show a biphasic relationship between severity of FSGS and glomerular size in Australian Aborigines.

Cell cycle regulatory proteins in renal disease: role in hypertrophy, proliferation, and apoptosis

The response to glomerular and tubulointerstitial cell injury in most forms of renal disease includes changes in cell number (proliferation and apoptosis) and cell size (hypertrophy). These events typically precede and may be responsible for the accumulation of extracellular matrix proteins that leads to a decrease in renal function. There is increasing evidence showing that positive (cyclins and cyclin-dependent kinases) and negative (cyclin-dependent kinase inhibitors) cell cycle regulatory proteins have a critical role in regulating these fundamental cellular responses to immune and nonimmune forms of injury. Data now show that altering specific cell cycle proteins affects renal cell proliferation and improves renal function. Equally exciting is the expanding body of literature showing novel biological roles for cell cycle proteins in the regulation of cell hypertrophy and apoptosis. With increasing understanding of the role for cell cycle regulatory proteins in renal disease comes the hope for potential therapeutic interventions.

Glomerular expression of dystroglycans is reduced in minimal change nephrosis but not in focal segmental glomerulosclerosis

Extensive flattening of podocyte foot processes and increased permeability of the glomerular capillary filter are the major pathologic features of minimal change nephrosis (MCN) and focal segmental glomerulosclerosis (FSGS). Adhesion proteins anchor and stabilize podocytes on the glomerular basement membrane (GBM), and presumably are involved in the pathogenesis of foot process flattening. Thus far, ao3 P,-integrin was localized to basal cell membrane domains. In this report, ao- and 3-dystroglycan (DG) were detected at precisely the sa-ne location by immunoelectron microscopy. and the presence of ac- and /-DG chains was confirmed by immunoblotting on isolated human glomeruli. Because the major DG binding partners in the GBM (laminin, agrin, perlecan), and the intracellular dystrophin analogue utrophin are also present in glomeruli, it appears that podocytes adhere to the GBM via DG complexes, similar to muscle fibers in which actin is linked via dystrophin and DG to the extracellular matrix. As with muscle cells, it is therefore plausible that podocytes use precisely actin-guided DG complexes at their "soles" to actively govern the topography of GBM matrix proteins. Expression of the a//3-DG complex was reported to be reduced in muscular dystrophies. and therefore a search for similar pathologic alterations in archival kidney biopsies from patients with MCN (it = 16) and FSGS (ni = 8) was conducted by quantitative immunoelectron microscopy. The density of a-DG on the podocyte's soles was significantly reduced to 25% in MCN, whereas it was not different in normal kidneys and FSGS. The expression of 3-DG was reduced to >50% in MCN, and was slightly increased in FSGS. Levels of DG expression returned to normal in MCN after steroid treatment (7 = 4). Expression of /3-integrin remained at normal levels in all conditions. These findings point to different potentially pathogenic mechanisms of foot process flattening in MCN and FSGS.

The role of angiotensin II and plasminogen activator inhibitor-1 in progressive glomerulosclerosis

Regardless of the primary cause, progressive renal deterioration with sclerosis is a hallmark of many renal diseases. Several studies have shown the superiority of angiotensin-converting enzyme inhibitors compared with other antihypertensive agents in providing protection from progressive renal deterioration. Furthermore, animal studies have shown that angiotensin II antagonists in excess of antihypertensive doses can also ameliorate or reverse glomerulosclerosis, leading to the hypothesis that angiotensin II has nonhemodynamic effects that mediate the renoprotective effects shown in these investigations. Although historically angiotensin II has been associated with salt and fluid homeostasis, recent data show that angiotensin II induces cell growth and matrix accumulation in glomerular cells. Plasminogen activator inhibitor-1 has been shown to be the major inhibitor of tissue plasminogen activator and urokinase-like plasminogen activator, with potentially important effects not only on thrombosis/fibrinolysis, but also on matrix degradation because of the proteolytic actions of these substances. Angiotensin II has been shown to influence the actions of plasminogen activator inhibitor-1 and, consequently, its thrombotic and sclerotic effects. Various studies, both in vitro and in vivo, have shown that direct hemodynamic actions, modulation of endothelial injury, and growth factor actions also may be important in the development of sclerosis. These factors can be directly modulated by angiotensin II inhibition. Sclerosis may even be reversed when therapies augment matrix degradation processes, both by directly increasing proteolytic activity and by downregulating inhibitors of matrix degradation. These observations indicate that angiotensin II is important in fibrotic as well as thrombotic renal injuries that lead to progressive renal disease and also in the development of therapies such as specific angiotensin receptor antagonists to prevent or reverse these conditions.

Measurement of glomerular volume in needle biopsy specimens. The ESPRIT Study Group (European Study of the Progression of Renal Disease in Type 1 Diabetes)

BACKGROUND

Various methods have been used to determine mean glomerular volume, some requiring measurement of over 30 glomerular profiles for a satisfactory estimate. Needle biopsies are useful diagnostically, but if small, provide insufficient tissue for the use of such methods.

METHODS

We performed glomerular volume measurements on renal biopsies from 10 normotensive, non-uraemic patients with Type 1 diabetes. Sections were taken at 10 microm intervals through 10 glomeruli per biopsy and points landing on glomerular tuft counted under light microscopy. Volume was calculated from the measured cross-sectional area and known section thickness using the Cavalieri principle.

RESULTS

Estimating the volume of 10 glomeruli per biopsy gave an overall mean glomerular volume of 4.21x10(6) microm(3) and standard deviation between patient means 1.23x10(6) microm(3.) Using a sample size of five glomeruli per biopsy only increased the standard deviation between patient mean values by 3%. Using sections taken at 20 microm intervals made little difference to the mean glomerular volume and standard deviation estimates (MGV 4.20x10(6) microm(3)+/-1.24). Further increases in the sectioning interval resulted in an appreciable increase in the variance of the estimate.

CONCLUSIONS

The results suggest that a satisfactory estimate of mean glomerular volume can be obtained from a sample size of five glomeruli per biopsy using a sectioning interval of 20 microm. This represents a great saving in analysis time and effort, making widespread use of this method of glomerular volume measurement in renal disease more practicable, in both research and clinical settings.

Effect of pituitary microsurgery on acromegaly complicated nephrotic syndrome with focal segmental glomerulosclerosis: report of a rare clinical case

A case of nephrotic syndrome complicated by acromegaly is presented. The first renal biopsy specimen showed minor glomerular abnormalities with glomerular hypertrophy, corresponding with minimal change nephrotic syndrome. Corticosteroid therapy led to a partial remission, followed by frequent relapses after reduction of the drug. A diagnosis of atypical focal segmental glomerulosclerosis (FSGS) was made based on the second renal biopsy results 6 months after the first. We combined steroid therapy with the administration of an anticoagulant, cytotoxic agents, angiotensin-converting enzyme inhibitor, and low-density lipoprotein adsorption. Except for the angiotensin-converting enzyme inhibitor, these medications were not effective in terms of allowing a reduction in the high dosage of steroid, which in turn threatened progressive osteoporosis and lumbar vertebrae fracture. Administering the steroid at a moderate dosage, treatment was focused on the complicating acromegaly from pituitary microadenoma. Subcutaneous injections of octreotide acetate, a somatostatin analogue, reduced proteinuria and increased urine volume. Subsequent transsphenoidal microsurgery of the adenoma resulted in the normalization of the elevated creatinine clearance and the further reduction in steroid dosage while maintaining a remission state. This is the first reported clinical case with acromegaly followed by FSGS, and it is suggested that hypersecretion of growth hormone participates in the development and progression of glomerular disease.

Stereologic methods and their application in kidney research

Stereologic methods are used to obtain quantitative information about three-dimensional structures based on observations from section planes or--to a limited degree--projections. Stereologic methods, which are used in biologic research and especially in the research of normal and pathologic kidneys, will be discussed in this review. Special emphasis will be placed on modern stereologic methods, free of assumptions of the structure, size, and shape, etc., so-called UFAPP (unbiased for all practical purposes) stereologic methods. The basic foundation of all stereology, sampling, will be reviewed in relation to most of the methods discussed. Estimation of error variances and some of the basic problems in stereology will be reviewed briefly. Finally, a few comments will be made about the future directions for stereology in kidney research.

Glomerular overproduction of oxygen radicals in Mpv17 gene-inactivated mice causes podocyte foot process flattening and proteinuria: A model of steroid-resistant nephrosis sensitive to radical scavenger therapy

Focal segmental glomerulosclerosis is a steroid-resistant glomerular disease characterized by foot process flattening and heavy proteinuria. A similar disease was found to occur spontaneously in mice in which the Mpv17 gene was inactivated by retroviral insertion (Mpv17-/- mice). Here evidence is provided that glomerular damage in this murine model is due to overproduction of oxygen radicals and accumulation of lipid peroxidation adducts that were found in isolated glomeruli of Mpv17-/- mice. The development of glomerular disease in Mpv17-/- mice was inhibited by scavengers of oxygen radicals (dithiomethylurea) and lipid peroxidation (probucol), but not by steroid treatment. Although the glomerular polyanion was greatly reduced in proteinuric Mpv17-/- mice, it was preserved by antioxidative therapy. These results indicate that the glomerular disease in Mpv17-/- mice qualifies as a model of steroid-resistant focal segmental glomerulosclerosis and that experimental therapies with scavengers of oxygen radicals and lipid peroxidation efficiently ameliorate glomerular damage.

Collapsing glomerulopathy: clinical characteristics and follow-up

In 1986, Weiss et al reported a group of patients with nephrotic syndrome, progressive chronic renal failure, and the histopathologic features of glomerular capillary collapse. Similar lesions are often described in human immunodeficiency virus (HIV) nephropathy. We evaluated 893 consecutive nontransplant renal biopsies performed in our department and the follow-up of the patients at our outpatient service. Sixteen specimens were identified with the pathological features of collapsing glomerulopathy (focal segmental or global glomerular capillary collapse and visceral epithelial cell hyperplasia), with no evidence of HIV infection and/or intravenous drug abuse. Their clinical characteristics were analyzed and compared with a group of 29 patients with noncollapsing focal segmental glomerulosclerosis (FSGS). The follow-up period of both patient groups was 5 +/- 1.46 years. The Kaplan-Meier life table method was used to present survival of the patients. The age of both groups was similar, 34 +/- 4 years (mean +/- standard error of the mean) for patients with collapsing glomerulopathy and 35 +/- 3 years for those with FSGS. The serum creatinine level was greater in patients with collapsing glomerulopathy (183 +/- 31 micromol/L) compared with those with FSGS (115 +/- 18 micromol/L), but the difference was not significant (P = 0.0504). The difference in proteinuria was not significant (P = 0.7668); it was 5.83 +/- 0.74 g/d in patients with collapsing glomerulopathy and 5.42 +/- 0.84 g/d in those with focal sclerosing glomerulonephritis. The difference in systolic (P = 0.4) and diastolic blood pressure (P = 0.556) was also not significant. Survival of the patients with collapsing glomerulopathy was worse than that of patients with FSGS (P = 0.025). Renal function survived 5 years in 40% of the patients with FSGS, but patients with collapsing glomerulopathy had no renal function survival. Our data suggest that idiopathic collapsing glomerulopathy is a distinct clinicopathologic entity with similar clinical features to focal sclerosing glomerulonephritis, but a worse prognosis and a rapidly progressive course toward end-stage renal disease.

Genetic polymorphisms of the renin-angiotensin system and the outcome of focal segmental glomerulosclerosis in children

BACKGROUND

The clinical course of primary focal segmental glomerulosclerosis (FSGS) in children is variable, with some patients having a much more rapidly progressing course than others. The purpose of our study was to compare the frequency of three polymorphisms of the renin-angiotensin system (RAS) in children with FSGS with that in healthy controls of matching ethnic groups, and to determine whether the clinical outcome of FSGS was associated with different RAS genotypes.

METHODS

Three RAS genotypes were examined in 47 Jewish and Arab children with biopsy-proven primary FSGS and in a large control group: the ACE insertion/deletion polymorphism in intron 16, the M235T mutation in the angiotensinogen gene, and the A1166C in the angiotensin II type 1 receptor gene (AT1R).

RESULTS

Arab patients showed a greater tendency towards progressive renal disease than their Jewish counterparts (12 of 21 vs. 9 of 26, P = 0.05) and were less likely to achieve remission (3 of 21 vs. 11 of 26, P < 0.04), despite similar clinical presentation, medical management and follow-up. The RAS allele prevalence was similar among patients and controls of matching ethnic backgrounds, and no difference in allele frequency was found between Arabs and Jews. Homozygotes for the ACE insertion genotype (II) were significantly less likely to have progressive renal disease than patients with the other genotypes (ID and DD; 0 of 6 vs. 21 of 41; P < 0.022). The other RAS polymorphisms were not associated with variations in the clinical course of childhood FSGS.

CONCLUSIONS

Homozygosity for the ACE insertion allele may have a protective effect in children with FSGS and can serve as a positive prognostic indicator at diagnosis. The D allele may exert a detrimental dominant effect on outcome. Neither the ACE gene polymorphism nor the other RAS polymorphisms studied are associated with disease prevalence. The AT1R and angiotensinogen gene polymorphisms are not associated with progression of renal disease in FSGS. Ethnic differences in the clinical course of the disease are not linked to these polymorphisms.

Baseline glomerular size as a predictor of function in human renal transplantation

BACKGROUND

Nonimmune mechanisms have been implicated in chronic renal allograft injury. In experimental studies, a strong correlation exists between glomerular size and the degree of glomerular sclerosis that develops after subtotal nephrectomy. Therefore, we assessed the impact of glomerular maximal planar area (MPA) in baseline biopsy specimens of human renal allografts on later graft function.

METHODS

The MPA was measured, by point counting and by computer planimetry, in postperfusion biopsy specimens from 96 allograft kidneys from nonhypertensive donors that had functioned for at least 2 years. Clinical data were analyzed throughout a follow-up period averaging 7.46+/-2.46 years.

RESULTS

Both methods produced equivalent estimates of MPA. MPA proved to be a strong predictor of late renal allograft function, with a significant correlation (P = 0.02 to P < 0.01) between MPA at baseline and later serum creatinine level and creatinine clearance, beginning at 6 months after transplantation and persisting through follow-up. Creatinine level at discharge and occurrence of rejection were also independent predictors, whereas donor age, gender and race, cold ischemia time, cadaveric versus living donor, delay in initial function, and HLA mismatch did not predict clinical outcome.

CONCLUSION

Larger glomeruli at baseline, measured by a simple point-counting technique, provide an early predictor of risk for late allograft dysfunction and may identify a subpopulation of patients in whom treatment to prevent/ameliorate glomerular enlargement and/or hypertension may be efficacious.

Differential response of glomerular epithelial and mesangial cells after subtotal nephrectomy

Recent studies in both human and experimental chronic renal disease suggest that there is a linkage between glomerular hypertrophy and glomerulosclerosis. To further define these relationships, we studied the changes in glomerular hypertrophy, procollagen alpha 1(IV) mRNA levels and glomerulosclerosis in rats undergoing 1 2/3 nephrectomy (Nx) or sham nephrectomy (SNx). Glomerular hypertrophy, measured biochemically by RNA/DNA and protein/DNA ratios, was significantly increased in Nx compared to SNx two days after subtotal renal ablation (RNA/DNA: Nx = 133 +/- 8%, SNx = 100 +/- 3% of the mean control value, P < 0.01; protein/DNA: Nx = 164 +/- 22%, SNx = 100 +/- 10%, P < 0.05) and remained elevated after 7 and 15 days (RNA/DNA: seven days Nx = 155 +/- 3%, SNx = 100 +/- 13%, P < 0.01; 15 days Nx = 303 +/- 21%, SNx = 100 +/- 24%, P < 0.001; protein/DNA: seven days Nx = 228 +/- 57%, SNx = 100 +/- 18%, P < 0.05; 15 days Nx = 341 +/- 23%, SNx = 100 +/- 18%, P < 0.01). Light microscopic measures of glomerular tuft volume (GTV) were too insensitive to detect glomerular enlargement until 15 days postoperatively, but GTV measured ultrastructurally demonstrated a 20% increment in Nx compared to SNx as early as two days postoperatively (P < 0.01). The latter increment in GTV was due exclusively to glomerular visceral epithelial cell (GVEC) expansion. Glomerular procollagen alpha 1(IV) mRNA levels were significantly elevated only 15 days after nephrectomy (Nx = 265 +/- 58% of the mean control value, SNx = 100 +/- 12%, P < 0.05; corrected for beta-actin mRNA levels). As this time, exuberant mesangial expansion measured ultrastructurally contributed to a 1.6 +/- 0.1-fold increase in GTV (P < 10(-5)), and to a relative decrement in the GVEC contribution to glomerular cells plus matrix (P < 0.01). Segmental sclerosis was observed only 15 days postoperatively in Nx (Nx = 1.3 +/- 0.4% of glomeruli evaluated, SNx = 0.0%, P < 0.05), and there was a strong correlation between the prevalence of segmental sclerosis and the procollagen alpha 1(IV) mRNA levels in Nx at 15 days (r = 0.93, P < 0.01). There was no significant correlation between the RNA/DNA and protein/DNA ratios and procollagen alpha 1(IV) mRNA levels. Thus, glomerular regions responded differentially to subtotal nephrectomy. Early epithelial cell expansion was followed by later mesangial expansion. Glomerular procollagen alpha 1(IV) mRNA levels were elevated only during the second (mesangial) phase of glomerular hypertrophy, when it correlated with glomerulosclerosis, but not during the initial (epithelial) phase, a pattern consistent with a mesangial origin of the procollagen alpha 1(IV) mRNA.

Glomerular number and size: facts and artefacts

This review article is concerned with clinical and experimental data on glomerular number and size and includes a critical discussion of the relevant stereological methods. There is considerable evidence supporting the view that the size of the glomerular filter, in toto, is related to the inception and development of glomerular disease. Major divergences from the filter size are incompatible with normal structure and function. Furthermore, the hypothesis has been put forward that there exists a subset of individuals with minor divergences from the norm that is more susceptible to glomerular disease than the general population. Stereological methods for estimating glomerular number and mean glomerular size could be applied to set standard values. In addition, if the above hypothesis is confirmed, then they could identify on biopsy specimens the patients that belong to cohorts at risk of developing glomerular disease. Unfortunately, despite the development of new, robust methods for particle counting and size determination, such as the fractionator and the dissector, no universal standards of glomerular number and size have been agreed on to date. The major difficulties depend on 1) establishing a standard protocol of tissue acquisition and processing and 2) defining possible variations across age, sex, and ethnic subgroups. The considerable effort required to overcome these difficulties should be rewarded, however, by important advances in the understanding of the morphogenesis of glomerular disease and in the diagnostic and prognostic yield of renal biopsy.

Metal-catalyzed oxidation of extracellular matrix proteins disrupts integrin-mediated adhesion of mesangial cells

We undertook the present study to determine whether oxidation of extracellular matrix could alter RGD (arginine-glycine-aspartic acid)-integrin interaction in mesangial cells. Mesangial cells demonstrated significantly less adhesion to matrix oxidized using a metal-catalyzed oxidation system and lost their typical spindle-shaped morphology. N-tert-butyl-alpha-phenylnitrone reversed in part both oxidation and impaired adhesion to matrix. Mesangial cells adhered to plates coated with GRGDSP but demonstrated impaired adhesion to oxidized GRGDSP. Oxidation of this peptide was demonstrated using immunoblot analysis with an antibody to dinitrophenylhydrazine bound to carbonyl groups on oxidized amino acid residues. This represents the first report demonstrating that oxidative modification of extracellular matrix impairs integrin-mediated adhesion and suggests that the mechanism may be oxidative modification of one or more amino acids in the RGD sequence. These data suggest a new mechanism by which cell-matrix interaction may be altered in disease states characterized by enhanced oxidative stress.

Biphasic glomerular hypertrophy in rats administered puromycin aminonucleoside

Recent evidence suggests that glomerular hypertrophy is a key event in the development of focal and segmental glomerulosclerosis and hyalinosis (FSGS) in humans and in many experimental models of FSGS. The initial aim of the present study was to determine if glomerular hypertrophy occurs in a puromycin aminonucleoside (PAN) model of FSGS, previously considered not to involve glomerular hypertrophy. Upon identifying significant glomerular hypertrophy, our second aim was to determine the contribution of glomerular capillary growth to this hypertrophy. Female Sprague-Dawley rats (approximately 200 g) were administered either PAN (2 mg/100 g body wt) subcutaneously, or an equivalent volume of 0.9% saline at weeks 0, 1, 2, 4, 6, 8 and 10. Tissue was analyzed at weeks 7 and 13. Unbiased stereological methods were used to estimate a range of glomerular parameters. Mean glomerular tuft volume in PAN-treated rats was 48% greater than in saline-treated rats at seven weeks, and 63% greater at 13 weeks. Similar results were found for mean renal corpuscle volume. FSGS was absent at seven weeks and minor at 13 weeks. Two-way analysis of variance indicated: significant effects (P < 0.05 at least) of PAN on capillary length per glomerulus, capillary surface area per glomerulus, capillary diameter and length of capillaries per unit volume of glomerulus; and significant effects of time on capillary diameter, capillary length per unit volume of glomerulus and capillary surface area per unit volume of glomerulus. The mean length of capillaries per glomerulus was 45% greater in PAN-treated rats at week 7 and 22% greater in PAN-treated rats at week 13. Taken together, these results indicate a biphasic pattern of glomerular hypertrophy in this model. In the first phase (to 7 weeks), an increase in capillary length contributes to glomerular hypertrophy. In the second phase (7 to 13 weeks), the continued glomerular enlargement appears more likely to be due to an increase in capillary diameter and/or mesangial matrix expansion.

Renal effects of moderate hypercholesterolaemia in uninephrectomized rats

Animal studies have shown that a 4-6-fold increase in serum cholesterol aggravates pre-existing renal injury. We studied the renal effects of moderate hypercholesterolaemia over a period of 18 weeks in uninephrectomized rats. Animals were allocated to two groups; the group 1 rats were fed a normal diet, as controls, and the group 2 rats were fed a high cholesterol diet containing 3% cholesterol and 1% sodium cholate by weight. The serum total cholesterol was higher in group 2 than in controls being 2.5 +/- 0.4 vs. 1.0 +/- 0.1 mmol l-1 at 9 weeks and 2.1 +/- 0.3 vs. 1.1 +/- 0.2 mmol l-1 at 18 weeks (p < 0.05 for both). Serum high density lipoprotein cholesterol levels were similar in both groups. The mean systolic blood pressure was higher in group 2 than in controls, at 145 +/- 9 vs. 137 +/- 8 mmHg (p < 0.05) by 13 weeks and 146 +/- 6 vs. 136 +/- 4 mmHg (p < 0.05) at 18 weeks. Serum creatinine and glomerular filtration rates were similar in both groups. Urine protein excretion remained within the normal range in both groups. Histological examination at 18 weeks showed diffuse fatty changes in the liver cells and prominent vacuolization of renal tubule cells in the group 2 rats. Nevertheless, the glomeruli were normal. There was no significant difference in mean glomerular volume between group 2 rats (1.20(-3) +/- 0.09(-3) mm3) and controls (1.36(-3) +/- 0.10(-3) mm3). Thus moderate hypercholesterolaemia for 18 weeks in uninephrectomized rats resulted in a mild elevation in blood pressure, but did not affect glomerular volume or glomerular histology, in spite of the deleterious effects on liver and renal tubule cells. We assume that extremely high levels of serum cholesterol are required to induce glomerulosclerosis in the rat.

Focal segmental glomerulosclerosis

Over the last 2 decades, we have learnt that focal segmental glomerulosclerosis (FSGS) is a ubiquitous phenomenon underlying the progressive deterioration of many different types of renal diseases in both pediatric and adult populations. FSGS may also be the primary renal lesion, whether in new disease entities such as glycogen storage disease and human immunodeficiency virus infection, or in idiopathic FSGS. Although the mechanism which triggers the development of primary FSGS still remains unknown, laboratory and clinical studies have identified several key pathophysiological events leading to end-stage renal disease. While therapeutic modalities have not changed remarkably, a recent study, although uncontrolled, demonstrated an impressive efficacy of intravenous steroid pulse therapy in inducing remission. Nevertheless, it remains largely unknown whether such a forced remission decreases the overall risk of developing chronic renal failure. Studies have revealed an important pathophysiological role of angiotensin and the therapeutic efficacy of angiotensin converting enzyme inhibitors in progressive loss of renal function in diseases where glomerulosclerosis is secondary; however, it remains to be verified whether these results hold true in primary FSGS. As a result of the improvement in allograft survival rate, the benefit of renal transplant outweighs the risk of recurrence of FSGS, hence transplantation continues to be a vital therapy for FSGS patients who have reached renal failure. Thus, FSGS is not one disease, but rather a range of lesions seen in many settings. The type of lesions and the patient's unique genetic factors contribute to prognosis, and also may dictate choice of optimum therapy.

Dissociation of glomerular hypertrophy, cell proliferation, and glomerulosclerosis in mouse strains heterozygous for a mutation (Os) which induces a 50% reduction in nephron number

We reported that the Os mutation in ROP mice induced a 50% reduction in nephron number, glomerular hypertrophy, and severe glomerulosclerosis. We examined two mouse strains with the Os mutation, ROP Os/+ and C57 Os/+ mice, to determine whether the genetic background influenced the development of glomerulosclerosis. Nephron number was decreased by 50% in both ROP Os/+ and C57 Os/+ mice, and a glomerular volume and labeling index were two- to threefold increased in both. Whereas glomerulosclerosis was severe in ROP Os/+ mice, it was absent or minimal in C57 Os/+ mice. ROP Os/+ glomeruli had two- to threefold more type IV collagen, laminin, and tenascin than C57 Os/+ by immunofluorescence microscopy. Glomerular alpha 1IV collagen and tenascin mRNA levels were increased (2.8- and 1.7-fold) in ROP Os/+ and in C57 Os/+ (1.7- and 1.4-fold) mice. Both ROP Os/+ and C57 Os/+ mice had a slight increase (1.5- and 1.7-fold) in 72-kD collagenase mRNA levels. Whereas laminin B1 mRNA levels were twofold higher in ROP +/+ than in C57 +/+ mice, there was no further change in the presence of the Os mutation. Thus, the response to the Os mutation depended on the mouse strain, since severe glomerulosclerosis occurred only in ROP Os/+ mice, even though cell proliferation and glomerular hypertrophy also were present in C57 Os/+ mice.

Possible relationship between hyperinsulinemia and glomerular hypertrophy in nephrosclerosis

Hyperinsulinemia is potentially associated with the development of vascular sclerosis. On the other hand, the relationship between hyperinsulinemia and nephrosclerosis has not been elucidated. In this investigation clinicopathological studies were performed in 40 patients with nephrosclerosis, with special attention to the relationship between hyperinsulinemia and glomerular hypertrophy. Forty patients with biopsy-proven nephrosclerosis were divided into two groups by the 75-g oral glucose tolerance test (OGTT): group A, 2-hr plasma glucose concentration > 140 mg/dL (n = 25); group B, 140 < or = 2-hr plasma glucose < 200 mg/dL (n = 15). Patients with diabetes mellitus or diabetic nephropathy were not included. Morphometric analysis of the glomeruli revealed a significantly larger mean glomerular volume in subjects with nephrosclerosis in both subgroups. In addition, the mean glomerular volume was significantly correlated with the fasting insulin level, while no significant correlation was observed between the mean glomerular volume and creatinine clearance or degree of global sclerosis. These results indicate that hyperinsulinemia may be intimately related to glomerular hypertrophy in patients with nephrosclerosis.

Pattern of glomerular involvement in human immunodeficiency virus-infected patients: an Italian study

Renal biopsy specimens from 26 adult human immunodeficiency virus (HIV)-infected patients with glomerular involvement were reviewed from the files of three hospital pathology services in Northern Italy. All the patients were Italian and most (19 of 26 patients) were intravenous drug addicts. The types of glomerular lesions were as follows: minimal-change glomerulopathy (two cases), mesangial proliferative glomerulonephritis (GN) with scanty immunoglobulin deposits (four cases), and various patterns of immune complex-mediated glomerulonephritis, including postinfectious GN (six cases), membranoproliferative GN (one case), membranous GN (three cases), immunoglobulin (Ig) A nephropathy (four cases), a mixed membranous and proliferative (three cases) and diffuse proliferative lupus-like pattern with subendothelial deposits, and intraluminal thrombi (two cases) or subepithelial and subendothelial deposits (one case). None of the patients had evidence of HIV-associated nephropathy. Our study confirms previous observations on the low incidence of HIV-associated nephropathy among white HIV-infected patients in Europe, where immune complex-mediated GN seems to predominate. Apart from the frequent electron microscopic observation of endothelial tubuloreticular structures, none of the reported lesions could be distinguished on morphologic grounds from those occurring in uninfected patients. The high variability of the glomerular lesions upholds the need for accurate diagnosis for the clinician confronted with an HIV-positive patient with suspected glomerular involvement.

Glomerular disease and lung transplantation

Three patients with lung or heart/lung transplants developed nephrotic-range proteinuria 2 to 5 years posttransplantation. Kidney biopsy showed focal segmental glomerulosclerosis in two patients and probable focal sclerosis in the third. A retrospective review of postmortem kidney specimens from 18 lung transplant recipients who died did not indicate additional cases of glomerular disease. The three patients with glomerular disease after lung transplantation had very few clinical similarities other than nephrotic-range proteinuria and lung transplantation. Their underlying lung diseases were different, and their posttransplantation courses were very different in terms of pulmonary function, cyclosporine nephrotoxicity, and other complications. We did not find in the literature previous reports of de novo focal segmental glomerulosclerosis or other glomerular lesions after lung transplantation. We suspect that additional cases will be identified in the future.

Transforming growth factor-beta 1 expression and phenotypic modulation in the kidney of hypertensive rats

We have previously reported that renal mRNA levels for transforming growth factor-beta 1, fibronectin, and collagens were increased in 32-week-old stroke-prone spontaneously hypertensive rats (SHRSP) with severe nephrosclerosis. To elucidate the mechanism of hypertension-induced nephrosclerosis, we examined gene expression and localization of transforming growth factor-beta 1 and cellular phenotype in the kidney of 25-week-old SHRSP with moderate renal damage. Renal mRNA was measured by Northern blot analysis. The localization of transforming growth factor-beta 1 and cellular phenotype was determined by immunohistochemistry. In the kidney of 25-week-old SHRSP, renal transforming growth factor-beta 1 mRNA was elevated compared with Wistar-Kyoto rats (WKY), whereas renal collagen mRNAs of SHRSP were not increased. Immunoreactive transforming growth factor-beta 1 in SHRSP was mainly localized in glomerular cells. Furthermore, alpha-smooth muscle actin and desmin were significantly expressed in SHRSP glomerular cells, in contrast to negligible expression of these proteins in WKY. alpha-Smooth muscle actin staining was also observed in interstitial cells, and vimentin, another phenotypic marker, was expressed in atrophic tubular cells of SHRSP, despite no staining of these proteins in WKY. Furthermore, all these phenotypic changes in SHRSP were associated with increased cell proliferation, as shown by the increased number of proliferating cell nuclear antigen-positive cells. Treatment of SHRSP with cilazapril and nifedipine (from the age of 13 to 25 weeks) prevented the increase in transforming growth factor-beta 1 expression and the cellular phenotypic modulation and was accompanied by a reduction of urinary albumin excretion and inhibition of cell proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)

Balance between matrix synthesis and degradation: a determinant of glomerulosclerosis

In glomerular health and disease, the balance between extracellular matrix (ECM) protein synthesis and degradation determines the amount of matrix that accumulates locally. While cell and whole animal regulation of ECM synthesis has been the subject of ongoing study, attention has become focused on proteases that degrade matrix components only recently. Two major ECM protease systems have been defined. The plasminogen activators (PAs) are serine proteases that have matrix-degrading capability and also activate plasminogen to plasmin. Plasmin not only degrades ECM proteins, but also may activate members of the matrix metalloproteinase (MMP) family which comprise the second major matrix-degrading system. Specific biological antagonists of both the PAs and the MMPs tightly regulate proteolysis by these enzymes. All of these enzymes and inhibitors have been detected in the kidney, and their expression may be altered to facilitate ECM accumulation in conditions associated with matrix expansion, such as glomerulosclerosis. Work is in progress to determine how these systems are regulated in the kidney and to further define their contribution to the sclerotic process.

Analyzing renal glomeruli with the new stereology

The highly specialized architecture of the renal glomerulus is altered in a variety of disease states. Morphometric methods, including stereological methods, have been widely used to analyze these changes in both animal and human glomeruli. However, many of the methods available until recently were biased and provided incomplete information. The past few years have witnessed the development of a new generation of unbiased stereological methods. Another advantage of these new methods and strategies is that they are less influenced by technical artifacts than the traditional methods. This chapter describes how these new stereological methods can be used to quantify glomerular morphology. Parameters considered include glomerular number and volume; glomerular cell number and size; and the length, surface area, and number of glomerular capillaries. Methods for obtaining data for average glomeruli as well as individual glomeruli are described. Technical details are included wherever possible.

Sodium dodecyl sulphate polyacrylamide gel electrophoresis of urinary proteins in steroid-responsive and steroid-resistant nephrotic syndrome in children

Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE) of urinary proteins was performed in 56 children with nephrotic syndrome during relapse, of whom 31 had their urines tested within 2 months of the onset of disease. The urines of all 32 steroid-sensitive [presumed minimal change nephrotic syndrome (MCNS)] patients revealed albumin and transferrin bands only; whereas 19 steroid-resistant children with focal glomerular sclerosis showed additional excretion of IgG and low molecular weight proteins (lysozyme, beta 2-microglobulin). This mixed pattern of proteinuria was also detected in 5 other steroid-resistant patients, 3 of whom were Africans with MCNS on biopsy and 2 who were Indians and not biopsied. Findings in patients studied within 2 months of presentation were identical to those investigated later in the course of the disease. SDS PAGE analysis of urine, which appears to distinguish steroid-responsive from steroid-resistant patients may provide a valuable adjunct to the management of childhood nephrotic syndrome.

Progression of glomerular diseases

The nature and slope of progression of glomerular diseases is the subject of considerable discussion. The use of renal biopsies has been accompanied by considerable improvement in the classification of glomerular disease. However, the clinical and histological tools available to assess prognosis in individual patients lack accuracy, especially in slowly progressive glomerular diseases such as diabetes mellitus. The development of molecular biology tools provides a new approach to the analysis of glomerulosclerosis. The accumulation of extracellular matrix in the glomerulus results from an exaggerated synthesis of collagens and other molecules forming the basement membranes, and is accompanied by an increase in the corresponding mRNAs. The measure of local glomerular gene activation can therefore provide a dynamic view of glomerular scarring. Utilizing a method combining microdissection of the glomeruli, reverse transcription in situ and a competitive polymerase-chain-reaction assay we were able to measure minute amounts of mRNAs in single mouse and human glomeruli. Both in mouse models and in human glomerulosclerosis we found upregulation of basement membrane collagen genes in the glomeruli. The increase appeared to be parallel to the slope of progression of glomerulosclerosis in experimental animals. This new approach may therefore provide a quantitative and sensitive method to define the propensity to sclerosis in human disease.

A quantitative analysis of the glomeruli in focal segmental glomerulosclerosis

Quantitative analysis of the glomerular area, mesangial matrix and mesangial cells was performed using renal biopsy specimens from 22 children with focal segmental glomerulosclerosis (FSGS) and 20 with minimal change nephrotic syndrome (MCNS). Non-sclerotic glomeruli were examined. All children in both groups showed nephrotic syndrome at the time of biopsy. Children with benign haematuria were examined as controls. Glomerular area increased with age in the FSGS, MCNS and control groups. The glomerular area was significantly greater in FSGS (1.5 +/- 0.4 x 10(4) microns 2) than in MCNS (1.2 +/- 0.2 x 10(4) microns 2) or in controls (1.2 +/- 0.3 x 10(4) microns 2) (P < 0.05). Mesangial matrix was increased with age in the three groups. The mesangial matrix was significantly increased in FSGS (28.3 +/- 4.0%; mesangial matrix area/glomerular area) compared with MCNS (24.9 +/- 4.1%) and controls (23.0 +/- 3.0%) (P < 0.01). These findings suggest that both glomerular hypertrophy and mesangial matrix increase in non-sclerotic glomeruli in FSGS may lead to glomerular sclerosis.

Human glomerular growth during childhood: a morphometric study

Morphometric measurements of glomerular size were made on renal biopsy specimens obtained from 16 children with minimal change nephrotic syndrome (MCNS) and 16 with isolated recurrent haematuria (RH), whose ages ranged from 1.8 to 15.2 years. Glomeruli were normal on light and electron microscopy, and immunofluorescence was essentially negative. Tracings were made of the outlines of glomerular capsules, tufts, and individual capillary lumens; using computerized digitometry, the mean areas of each item were determined. The number of capillary lumens per glomerulus was counted automatically. From these data, the mean mesangial area was also calculated. Mesangial cells were counted in at least 100 distal mesangial areas per biopsy. The mean glomerular capsular area (GCA) correlated well with the mean glomerular tuft area (GTA) but frequent capsular artefacts rendered the former measurement less suitable for comparison with diseased glomeruli. The mean GTA correlated significantly with age and body surface area in both MCNS and RH, as did the number of capillary lumens per glomerulus, but the mean capillary lumina area showed no such correlations. The mean mesangial area increased with age in proportion to GTA, whereas mesangial cell counts remained normal. These findings indicate that glomerular growth during childhood is proportional to body growth, and are consistent with capillary subdivision as the mechanism of enlargement.

Glomerular volume and renal function in children with different types of the nephrotic syndrome

Glomerular hypertrophy has been suggested to be an important factor in the pathogenesis of focal glomerular sclerosis. The aim of the present study was to analyse retrospectively the renal biopsies of 58 children (0.2-16.1 years of age) with different types of the nephrotic syndrome, minimal change nephrotic syndrome (MCNS), diffuse mesangial proliferation (DMP) and focal segmental glomerulosclerosis (FSGS). Glomerular surface area was measured and glomerular volume was calculated and related to steroid responsiveness and to renal function, measured by clearances of inulin and para-aminohippuric acid. Glomerular volume correlated with body surface area (BSA) and age. Because of this, patients with FSGS and DMP were matched according to BSA and age, with corresponding MCNS patients. Glomerular volumes of FSGS and DMP patients were significantly larger than those of MCNS patients. In the MCNS patients, significant correlations were found between glomerular volumes and glomerular filtration rate and effective renal plasma flow. Steroid-dependent and steroid-resistant patients showed larger glomeruli than the steroid-responsive children. We suggest that hyperfiltration and hyperperfusion, among other factors, may contribute to glomerular hypertrophy, mesangial proliferation and glomerulosclerosis.

Glomerular hypertrophy and chronic renal failure in focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis evolves toward chronic renal failure (CRF) with a highly variable rate; in particular, a group of patients with a much more rapid decline of renal function has been described. The purpose of this study was to evaluate the usefulness of morphometry in identifying those cases with a faster decline in renal function. Two groups of patients have been studied: six with rapid evolution toward CRF (group 1) and six without reduction in renal function during a follow-up of up to 10 years (group 2). The results of the morphometric analysis of glomeruli were as follows: mean glomerular area: 30,550 +/- 5,259 microns2 (group 1) versus 22,667 +/- 5,078 microns2 (group 2) (P = 0.01); maximum glomerular area: 40,827 +/- 9,508 microns2 (group 1) versus 30,445 +/- 7,224 microns2 (group 2) (P = 0.02); mean glomerular diameter: 193.9 +/- 15.8 microns (group 1) versus 161.8 +/- 16.8 microns (group 2) (P = 0.003); and caliper diameter: 328.6 +/- 20.6 microns (group 1) versus 260.6 +/- 36 microns (group 2) (P = 0.001). Values of body surface area were not different between the two groups (1.85 +/- 0.34 m2 v 1.6 +/- 0.13 m2) (P = NS). Our results suggest that glomerular hypertrophy in the course of focal segmental glomerulosclerosis is correlated with a faster decline toward CRF. It might represent a compensatory hypertrophy that would immediately precede a rapid decline in renal function or it might be the expression of the preexisting condition (meganephronia), which predisposes to the development of CRF.

The effect of selective growth hormone defect in the progression of glomerulosclerosis

The role of endogenous growth hormone (GH) in the progression of glomerulosclerosis was examined in a new mutant strain of Sprague-Dawley (SD) rats with a selective GH gene defect. Fifteen spontaneous dwarf [GH(-)] rats and 10 SD rats underwent subtotal nephrectomy (Nx) or sham operation. Twelve weeks after Nx, the mean arterial pressure, glomerular filtration rate, urinary protein excretion rate, glomerular size, and frequency of glomerulosclerosis were examined. Marked elevation in mean arterial pressure was seen in both SD/Nx and GH(-)/Nx rats. In both strains, the glomerular filtration rate at 12 weeks after Nx was approximately 50% to 60% of that seen in the respective Sham-operated rat groups. The urinary protein excretion rate increased significantly only in the SD/Nx rats. The glomerular size, expressed as the ratio of glomerular volume to body weight, increased by 200% in the SD/Nx rats compared with the SD/Sham rats, in marked contrast to the 70% increase in the GH(-)/Nx rats compared with the GH(-) rats. The frequency of glomerulosclerosis in the GH(-)/Nx rats (1.0 +/- 0.5%) was significantly lower than that in the SD/Nx rats (16.7 +/- 2.8%). The frequency of glomerulosclerosis correlated with glomerular hypertrophy in both the SD and GH(-) rats (r = 0.88 and 0.67, respectively). These results show that the progression of glomerular sclerosis was markedly attenuated in the GH-defective rats. This attenuation of structural injury was correlated with a marked decrease in glomerular hypertrophy. These studies indicate that this specific growth regulatory peptide of endogenous origin plays an important determining role in the progression of glomerulosclerosis.

Cytokine stimulation of prostaglandin production inhibits the proliferation of serum-stimulated mesangial cells

Mesangial cell proliferation contributes to glomerulosclerosis and is associated with the development of end-stage renal disease. We examined the effects of the cytokines interleukin 1 (IL-1 beta) and interleukin 6 (IL-6) on the mitogenesis and proliferation of rat glomerular mesangial cells. Exposure of serum-stimulated cells to IL-1 beta and IL-6 for 48 hours resulted in a dose-dependent inhibition of both mitogenesis, determined by 3H-thymidine incorporation, and proliferation, determined by absolute cell counts. Both IL-1 beta and IL-6 stimulated endogenous PGE2 production in this cell system. Cyclooxygenase inhibition by indomethacin and meclofenamate abrogated the inhibitory effects of both IL-1 beta and IL-6. Furthermore, addition of exogenous PGE2 to cytokine-stimulated cells in which cyclooxygenase activity was blocked resulted in inhibition of mitogenesis, while addition of exogenous aracidonic acid to the cytokine-stimulated cells enhanced the induced inhibition of mitogenesis. These results demonstrate that in serum-stimulated mesangial cells, both IL-1 beta and IL-6 inhibit mitogenesis and proliferation, and that these effects are mediated, in part, by stimulated endogenous prostaglandin production.

Glomerular dimensions in children under 16 years of age

Glomerular area, perimeter, and mean maximum glomerular diameter were assessed in post-mortem kidney tissue from 114 children who died suddenly in accidents and who were considered to have been previously healthy. One hundred glomeruli were measured from each case using a computer-based measurement system. Regression analysis was used to analyse glomerular size with respect to age, body weight, height, and body mass index. The estimated mean glomerular area for newborns was 7934 microns 2 (SE 314), increasing 8 per cent per year to 18,219 microns 2 at 15 years of age. The estimated mean maximum glomerular diameter increased from 112 microns (SE 1.9 microns) for newborns, approximately 3.6 microns per year to reach 167 microns at age 15. Glomerular size correlated better with age than with height, weight, or body mass index, and glomeruli in the inner cortex were significantly larger than those in the middle and outer cortex. Glomerular size was significantly greater in female children than in the male children over the age range examined.

Segmental sclerosing glomerular lesions

Segmental sclerosing glomerular lesions are usually all grouped together and called focal segmental glomerulosclerosis. This has meant that the term that was originally used for a defined clinical entity is now applied to a variety of conditions in man and experimental animals, with the assumption that the morphological changes are the same in all conditions. Studies of the position of segmental lesions within glomeruli, the size of glomeruli and the proportion of glomeruli affected have shown that this assumption is wrong. Such studies have identified a disease that corresponds to the original clinical concept of focal segmental glomerulosclerosis. This begins with the nephrotic syndrome in patients whose renal biopsies show large glomeruli with mesangial hypercellularity and segmental lesions at every tubular origin. Later the biopsies have segmental lesions throughout the glomerular tuft. This disease differs clinically and pathologically from other conditions that have segmental sclerosing lesions, such as in patients with reduced renal mass or patients with hypertension and proteinuria. The term focal segmental glomerulosclerosis is now too ambiguous and unsatisfactory to be used without qualification.