Rare glomerular capillary regeneration and subsequent capillary regression with endothelial cell apoptosis in progressive glomerulonephritis.

Glomerulonephritis (GN) leading to glomerular sclerosis remains an important cause of renal failure. The glomerulus is a capillary network, but endothelial and vascular reactions during progressive GN are not well understood. We have, therefore, examined the morphological alterations of glomerular capillary network and endothelial cells during the progression of damaged glomeruli to glomerular sclerosis. A progressive model of anti-glomerular basement membrane (GBM) GN was induced in Wistar-Kyoto (WKY) rats with a single injection of anti-rat GBM antibody. Severe necrotizing glomerular injuries were observed between day 5 and week 3 with a reduction in the number of total glomerular endothelial cells and total glomerular capillary lumina per glomerular cross sections. In necrotizing lesions, the glomerular endothelial cells were lost with the destruction of the glomerular capillary network. Moreover, angiogenic capillary repair with proliferation of endothelial cells was rare in severely damaged regions of glomeruli. Subsequently, mesangial hypercellularity and marked mesangial matrix accumulation occurred with absence of the development of a capillary network, and the necrotizing lesions progressed to sclerotic scars until 8 weeks. Although active necrotizing lesions could not be seen in damaged glomeruli between week 4 and week 8, the number of apoptotic endothelial cells gradually increased in the glomerular capillaries (0.10 +/- 0.01 apoptotic endothelial cells/glomerular cross section at week 8 versus 0.00 +/- 0.00 control cells (mean +/- SEM; P < 0.05) with the progression of glomerular sclerosis. Whereas the number of apoptotic endothelial cells increased in the damaged glomeruli, the number of total glomerular endothelial cells decreased (9.3 +/- 3.0 cells/glomerular cross section at week 8 versus 24.8 +/- 3.0 cells in control (mean +/- SD); P < 0.001) with regression of glomerular capillaries (3.6 +/- 2.5 capillary lumina/glomerular cross section at week 8 versus 35.0 +/- 5.0 capillary lumina in control (mean +/- SD); P < 0.001). Finally, glomerular endothelial cells could not be detected in the sclerotic lesions in progressive anti-GBM GN in WKY rats. These data indicate that the destruction of the capillary network of glomeruli and subsequent incomplete angiogenic capillary repair leads to glomerular sclerosis in progressive GN. Endothelial cell apoptosis with glomerular capillary regression may also contribute to the development of glomerular sclerosis. Injury of the glomerular capillary network with endothelial cell damage, including apoptosis and subsequent incomplete capillary repair, plays an important role in the progression of glomerular sclerosis during anti-GBM GN in WKY rats.     

Glomerular epithelial cell lesions in rat renal isografts

Visceral glomerular epithelial cell lesions--microvillus formation, loss of foot processes, osmiophilic inclusion droplets, balloon-like malformation of cell processes, degeneration, necrosis, and loss of cell processes from capillary basement membranes--are found in rat renal isografts 1 mth after transplantation. The lesions, which are most readily recognized in perfusion-fixed material, are essentially focal, affecting neither all glomeruli, nor all cells in any glomerulus, bear no relation to the degree of interstitial nephritis in the graft, and are associated with albuminuria and with focal capillary sclerosis in some glomeruli. They are not restricted to renal isografts but are found in aging rats, in different experimental models of glomerular disease and in clinical glomerular disorders, again in association with proteinuria and glomerulosclerosis. It is therefore proposed that glomerular epithelial cell damage increases capillary permeability and impairs maintenance of the integrity of the capillary wall, leading to proteinuria and focal glomerulosclerosis.     

Ultrastructure of the non-sclerotic glomeruli in childhood nephrotic syndrome

An electron-microscopic (EM) study of the non-sclerotic glomeruli was made in 96 children with the nephrotic syndrome in whom light microscopy had shown minimal change, focal global glomerulosclerosis or segmental glomerulosclerosis. EM showed a variety of alterations. Foot process fusion, duplication and crenation of the lamina densa, and granular and lucent expansion of lamina rara interna were noted in almost all patients in all three groups. Localised ulceration of the podocytes was noted in some patients in each group. There was no difference in the mean thickness of the glomerular basal lamina but there was an increase with age in minimal change. Curious extracellular curved striated bodies, clusters of electron-dense, round microparticles and microfilaments were found in all three. but most frequently in segmental glomerular sclerosis. Electrondense deposits were seen in all but one of the patients with segmental glomerular sclerosis and usually involved the capillary wall. They were seen in one third of those with minimal change and focal glomerular sclerosis but rarely in the capillary wall. There were no specific features which distinguished segmental glomerular sclerosis although the various types of deposits were more extensive and more frequent than in minimal change and focal glomerular sclerosis. These observations are consistent with common pathogenetic factors operating at different intensities in segmental glomerular sclerosis, focal glomerular sclerosis and minimal change.     

Glomerular cells, extracellular matrix accumulation, and the development of glomerulosclerosis in the remnant kidney model.

Expansion of the mesangial extracellular matrix (ECM) with subsequent glomerular sclerosis is a prominent finding in most progressive renal diseases. To investigate the chronology of accumulation of ECM components as it relates to previously described cellular events, biopsies were obtained from rats at various times following 5/6-nephrectomy as well as from sham-operated controls. The biopsies were stained with PAS as well as immunostained for PCNA (a cell proliferation marker), monocytes/macrophages, types I and IV collagen, laminin, s-laminin, fibronectin, heparan sulfate proteoglycan and entactin/nidogen. Immunostaining of biopsies obtained from 5/6 nephrectomized rats demonstrated an early glomerular cell proliferation, peaking at week 2. Expansion of the glomerular tuft area with rare glomeruli demonstrating focal sclerosis were also seen at week 2. Glomerular macrophage influx correlated with later ECM expansion and glomerulosclerosis. A progressive accumulation of all ECM proteins investigated was noted in the pathological mesangial matrix at week 2 and later time points. Northern analysis of total glomerular RNA at weeks 2 and 6 after 5/6 nephrectomy showed de novo expression type I collagen mRNA as well as small increases of glomerular mRNA levels for type IV collagen (1.2- and 1.4-fold over control RNA) and laminin (1.3- and 1.5-fold) but not s-laminin (1.1- and 0.9-fold). We conclude that cellular events including glomerular cell proliferation and macrophage influx are associated with increased gene and protein expression by ECM proteins in the remnant kidney model and may contribute to the development of sclerosis.     

Glomerular lesions in mice transgenic for growth hormone and insulinlike growth factor-I. I. Relationship between increased glomerular size and mesangial sclerosis.

The glomeruli of mice transgenic for bovine growth hormone (GH mice) were disproportionately enlarged as a function of either kidney or body weight. Glomerular size correlated with mesangial sclerosis and the urine albumin/creatinine ratio. The glomerular lesions consisted of mesangial proliferation (4 to 5 weeks) followed by progressive mesangial sclerosis (19 weeks), resulting in complete glomerulosclerosis at 30 to 37 weeks. Albuminuria paralleled the glomerulosclerosis. In contrast, mice transgenic for insulinlike growth factor-I (IGF-I mice) did not develop glomerulosclerosis, even though glomerular size significantly increased. Glomerular hypertrophy, however, did not reach that in GH mice. These data suggest that high levels of circulating GH lead to a disproportionate increase in glomerular cellularity and volume, as well as glomerulosclerosis. This does not appear to be the result of high levels of circulating IGF-I stimulated by GH, as the serum IGF-I level in GH mice was lower than that in IGF-I mice.     

Progressive renal lesions induced by administration of monoclonal antibody 1-22-3 to unilaterally nephrectomized rats.

A new animal model of progressive glomerulosclerosis was developed by administering a single i.v., injection of MoAb 1-22-3 to unilaterally nephrectomized rats. Renal morphological analysis revealed that glomerular lesions characterized by mesangial cell proliferation and mesangial matrix expansion were induced in about 95% of the glomeruli. Approximately 20% of the glomeruli of the unilaterally nephrectomized rats showed sclerosis or segmental sclerosis by week 6 after MoAb injection and crescent formation was observed in some glomeruli (ca 4%). Cellular infiltration was also noted in some parts of the interstitium. Increased expression of transforming growth factor-beta (TGF-beta) was observed in the unilaterally nephrectomized rats treated with MoAb 1-22-3, but we could not demonstrate pathological involvement of platelet-derived growth factor (PDGF), even though early-stage mesangial cell proliferation was observed. The mechanism of mesangial cell proliferation in this model remains to be elucidated. The relatively short period of time needed to induce the sclerotic changes in considered to be a great advantage of this model for clarifying the mechanisms involved in the chronic progression of mesangial proliferative glomerulonephritis.     

Vascular endothelial growth factor enhances glomerular capillary repair and accelerates resolution of experimentally induced glomerulonephritis

Vascular endothelial growth factor (VEGF) regulates angiogenesis through endothelial cell proliferation and plays an important role in capillary repair in damaged glomeruli. We tested the hypothesis that VEGF might be beneficial in rats with severe glomerular injury in glomerulonephritis (GN) based on its angiogenic and vascular remodeling properties. Acute GN with severe glomerular destruction was induced in rats by injection of anti-Thy-1.1 antibody (day 0) and Habu-snake venom (day 1). Rats were intraperitoneally injected with recombinant human VEGF(165) (10 microg/100 g body wt/day) or vehicle from day 2 to day 9, and monitored changes in glomerular capillaries, development of glomerular inflammation, and progression to glomerular sclerosis after acute glomerular destruction in both groups. Rats that received anti-Thy-1.1 antibody and Habu-snake venom showed severe mesangiolysis and marked destruction of capillary network on day 2. VEGF was expressed on glomerular epithelial cells, proliferating mesangial cells, and some infiltrating leukocytes, and VEGF(165) protein levels increased in damaged glomeruli during day 5 to day 7. Normal, damaged, and regenerating glomerular endothelial cells expressed VEGF receptor flk-1. However, endothelial cell proliferation and capillary repair was rare in vehicle-treated rats with severe glomerular damage, which progressed to global sclerosis and chronic renal failure by week 8. In contrast, in the VEGF-treated group, VEGF(165) significantly enhanced endothelial cell proliferation and capillary repair in glomeruli by day 9 (proliferating endothelial cells: VEGF(165), 4.3 +/- 1.1; control, 2.2 +/- 0.9 cells on day 7, P < 0.001; and glomerular capillaries: VEGF(165), 24.6 +/- 4.8; control, 16.9 +/- 3.4 capillaries on day 7, P < 0.01). Thereafter, damaged glomeruli gradually recovered after development of capillary network by week 8, and significant improvement of renal function was evident in the VEGF-treated group during week 8 (creatinine: VEGF(165), 0.3 +/- 0.1; control, 2.6 +/- 0.9 mg/dl, P < 0.001; proteinuria: VEGF(165), 54 +/- 15; control, 318 +/- 60 mg/day, P < 0.001). We conclude that the beneficial effect of VEGF(165) in severe glomerular injury in GN emphasizes the importance of capillary repair in the resolution of GN, and may allow the design of new therapeutic strategies against severe GN.     

Glomerular hyalinosis and its relation to hyperfiltration

Reduction in renal mass in rats results in hyperfiltration of the remnant nephrons, accompanied by injury to the glomeruli and their eventual sclerosis. This study was undertaken in a rat model with 5/6 reduction of renal mass to follow the evolution of glomerular damage, over an 11-week period, with particular emphasis on the widely prevalent, although seldom discussed, lesion of hyalinosis. Light, electron, and immunofluorescence microscopic studies were performed and blood pressure, excretion of urinary albumin, and serum creatinine levels determined. Systolic blood pressure, urinary albumin excretion, and serum creatinine levels were all increased by the third week following operation. Blood pressure and serum creatinine continued to increase throughout the period of study. Glomerular damage was focal and segmental, and glomeruli were equally affected in both the juxtamedullary and outer zones of the cortex. Endothelial injury was noted to be the first indicator of glomerular damage, followed closely by alterations in the epithelial cells. The early hyalinosis lesion was characterized by an accumulation of homogeneous electron-dense material beneath damaged endothelial cells with later encroachment on the capillary lumen resulting in the easily recognizable eosinophilic, periodic acid-Schiff-positive lesion by light microscopy. These alterations were accompanied by complex changes within the mesangium, including both mesangiosclerosis and mesangiolysis. Glomerular hyalinosis, glomerular sclerosis, vascular damage, blood pressure, and albuminuria were ranked in order of severity and the rankings subjected to multiple regression analysis. Significant correlations were present between glomerular sclerosis and hyalinosis, arterial damage and blood pressure, and hyalinosis and urinary albumin excretion. The hyalinosis lesion accompanying the progressive glomerular sclerosis in this model resembles that seen in a number of human conditions. In addition, the correlations of hyalinosis with glomerular sclerosis and albuminuria reflect its association with glomerular injury; it is likely that it will prove to be a reliable marker of hyperfiltration injury.     

Age-related nephropathy and proteinuria in rats with intact kidneys exposed to diets with different protein content

Tubulointerstitial damage and glomerular sclerosis are findings commonly observed in the experimental models of adriamycin and puromycin aminonucleoside nephrosis. It has been suggested that in such models proteinuria might be an important mediator of tubulo-interstitial damage which in turn may determine the progression of the disease favoring the development of glomerulosclerosis. The objective of the present investigation was to establish the temporal relationship between proteinuria, tubulo-interstitial damage and glomerulosclerosis in aging rats with intact kidneys exposed to diets with different protein content. There were six groups of rats studied. Animals of groups 1, 5, and 6 (N = 10) were fed diets containing 20, 35, and 6% protein, respectively, for 20 months and sacrificed at the end of the experimental period. Rats in groups 3 and 4 (N = 6) exhibited marked and mild proteinuria, respectively, after 14 months of maintenance on standard diet, and followed for two additional months after the onset of proteinuria with the aim of evaluating the pattern of renal damage after a relatively short period of proteinuria. Rats in group 2 (N = 10) were fed standard diet and sacrificed before (5 months) and at the onset of proteinuria (10 months). Protein excretion and plasma creatinine were measured for each animal every month. Pathologic examination was performed by light and electron microscopy. At the onset of proteinuria neither renal structural nor functional abnormalities were detected. After 20 months, rats fed standard diet developed tubulo-interstitial damage (score: 1.29 +/- 1.05) and focal glomerular sclerosis (percentage of glomeruli with focal segmental glomerular sclerosis: 16.70 +/- 16.40). A significant correlation was found between the degree of tubulo-interstitial damage and the percentage of glomeruli with focal glomerular sclerosis (r = 0.99, p less than 0.01). Development of tubulo-interstitial damage and focal glomerular sclerosis were correlated with heavy and sustained proteinuria. The high protein diet significantly worsened proteinuria (at month 20: 247.08 +/- 101.73 mg/day), tubulo-interstitial changes (score: 1.99 +/- 0.70), focal glomerular sclerosis (percentage of glomeruli with focal segmental glomerular sclerosis: 21.50 +/- 9.44) and was associated with deteriorating renal function (at month 20, plasma creatinine: 1.20 +/- 0.50 mg/dl).(ABSTRACT TRUNCATED AT 400 WORDS)     

Prevention of 11-deoxycorticosterone-salt-induced glomerular hypertrophy and glomerulosclerosis by dietary phosphate binder.

The effects of dietary phosphate binder on deoxycorticosterone (DOC)-salt-hypertensive rats were examined. DOC-treated and non-DOC-treated rats were fed the diet either with or without phosphate binder, dihydroxyaluminum aminoacetate. All rats drank 1% NaCl. DOC-salt-treated rats without binder demonstrated marked glomerular hypertrophy, many globally sclerosed glomeruli, severe proteinuria, focal cardiac fibrosis, and splenomegaly. A significant reduction of glomerular hypertrophy, glomerulosclerosis, severity of proteinuria, splenomegaly, and the myocardial lesion took place when the DOC-salt-treated rats were given phosphate binder. The globally sclerosed glomeruli exhibited remarkable hypertrophy while structurally preserved glomeruli showed little evidence of enlargement. The plasma phosphate level was low in rats with dietary phosphate binder. In conclusion, the dietary phosphate binder ameliorated glomerular hypertrophy, glomerulosclerosis, proteinuria, myocardial fibrosis, and splenomegaly occurring in DOC-salt-treated rats. The data indicated that there was an association between glomerular hypertrophy and glomerulosclerosis in this model. The exact mechanisms of action of the phosphate binder, however, remain far from clear.     

Comparison of size of juxtamedullary and outer cortical glomeruli in normal adult kidney

Summary Abnormally large glomeruli are susceptible to hyperfiltration-associated sclerosis. We used an established morphometric method to test the general belief that juxtamedullary glomeruli are larger than those in the outer cortex, in a population with no clinical or pathological evidence of renal disease. Overall, juxtamedullary glomeruli were significantly larger, but this varied according to the amount of global glomerulosclerosis present. Global sclerosis increased with age, particularly in the outer cortex, and the ratio of juxtamedullary to outer cortical glomerular size showed a positive correlation with overall, and outer cortical, global sclerosis. Thus in the truly normal adult kidney, juxtamedullary glomeruli are not significantly larger than outer cortical glomeruli. However, global sclerosis increases with age and is most marked in the outer cortex, and this leads to compensatory enlargement of predominantly the juxtamedullary glomeruli. These findings suggest that in single kidneys, or in conditions characterised by ischaemic glomerulosclerosis such as hypertension, morphological changes related to hyperfiltration may appear first, and therefore become most severe, in juxtamedullary glomeruli.     

Experimental ablation nephropathy. Fine structure, morphometry, cell membrane epitopes, glomerular polyanion and effect of subsequent transplantation.

The subtotal (5/6) nephrectomy performed in 23 adult female rats induced severe hypertrophy of residual parenchyma with interstitial fibrosis, tubular dilatation, and focal and segmental glomerulosclerosis (FSG). This ablation nephropathy (AbN) caused proteinuria, progressive renal failure, and hypertension. The extent of FSG was assessed by semiquantitative scoring. The ultrastructure revealed widespread foot process fusion, many dense cytoplasmic inclusions in podocytes, and degenerative changes or disruption of mesangium with glomerular "microcysts". Numerous granular deposits of rat Ig were seen in the glomeruli but a short praeterminal i.v. load by heat-aggregated human Ig did not alter the morphology of AbN and produced discrete and inconstant glomerular deposits. Similarly an i.v. injection of protamine and heparin generated protamine-heparin complexes seen in various layers of glomerular capillary wall, similar to those found previously in normal rats. AbN displayed a partial irregular depletion of polyanion sites reactive with polyethylenimine in lamina rara externa. A significant increase in both glomerular and interstitial Ia+ cells and a marked predominance of W3/25+ cells in the interstitial infiltrates were documented by immunohistochemistry in the remnant kidneys. Both AbN and FSG could be largely corrected (or prevented?) by subsequent syngeneic renal transplantation (TPL; 6 animals). On the other hand a severe AbN was found in two post-ablation residues after unsuccessful TPL with graft necrosis or sclerosis.--AbN has some analogies to various chronic human nephropathies (e.g. FSG) and may explain their progression to the terminal failure. Degenerative and finally destructive mesangial lesion seems to be of prime importance in AbN.     

Glomerular cells and macrophages in the progression of experimental focal and segmental glomerulosclerosis.

To determine the characteristics of glomerular cell involvement in experimental focal and segmental glomerulosclerosis (FGS) in rats induced by repeated injections of aminonucleoside of puromycin (PAN) and protamine sulfate (PS), glomeruli were isolated and grown in tissue culture. When compared with saline controls the FGS rats had decreased rates of glomerular attachment and significantly reduced outgrowths of type 1 (epithelial) and type II (mesangial) cells. However, the FGS rats had greater numbers of type III cells (macrophages) present in the outgrowths than controls. The production of interleukin-1 (IL-1) in the glomerular culture supernatant, measured by thymocyte stimulating activity, was determined at various stages throughout the evolution of FGS and in saline controls. The FGS glomeruli early in the disease course (day 10) had higher levels of IL-1 activity than glomerular outgrowths from control rats but significantly lower levels of IL-1 were produced late in the disease (day 80). Glomerular macrophages were present throughout the evolution of the disease but in greater numbers early (day 10). In this experimental model of FGS, IL-1 production, has been demonstrated early in the disease process, could originate from macrophages and/or mesangial cells, and could be involved in the progressive glomerulosclerosis.     

Atubular glomeruli and the structural basis for chronic renal failure.

The pathologic changes in chronic renal failure are heterogeneous and depend to some extent on the primary disease process. However, end-stage kidneys have many common features, and other factors than the primary disease may be operative in the progression. Hyperfiltration of still functioning glomeruli has (especially in rat studies) been shown to be followed by glomerular injury. This progressive glomerulosclerosis has been proposed as a mechanism for the continuous deterioration of renal function that is found in most chronically diseased kidneys. Increased glomerular capillary pressure and glomerular hypertrophy, and dietary factors have been invoked in the pathogenesis of the glomerulosclerosis. In several chronic renal diseases, including tubulointerstitial diseases, but also some primary glomerular diseases such as glomerulonephritis, the renal function correlated better with the changes in the tubules and interstitium than with glomerular changes detectable in simple 2-dimensional sections. The correlation between tubulointerstitial changes and renal insufficiency has been explained by obliteration of the postglomerular capillaries supposed to lead to a decreased glomerular blood flow or by reduced reabsorption of sodium chloride in atrophic or damaged proximal tubules with subsequent reduction of glomerular filtration via the tubuloglomerular feedback mechanism. Atubular glomeruli have been found in several, mainly tubulointerstitial disorders. Unbiased morphometrical methods have provided valuable quantitative data about the atubular glomeruli and about the structural renal changes in general. The atubular glomeruli constitute a significant and sometimes even a major part of the glomerular population in various chronic renal diseases. The atubular glomeruli are generally small, whereas glomeruli connected to normal proximal tubules have volumes at the normal level or above. Atubular glomeruli have open capillaries and minor ultrastructural changes and function as a pathway for blood that is delivered without prior filtration to the intertubular capillaries. This lack of filtration may explain the decreased filtration fraction seen in some renal diseases. Their fate in the chronically diseased kidney is not known but they have not been shown to be eliminated. They can only be identified using serial sections or microdissection. Correlation between the decrease in renal function and the decrease in percentage of glomeruli connected to normal proximal tubules have been found in experimental lithium and cisplatin nephropathy. The presence of atubular glomeruli explains the correlation between the volume of proximal tubules (and interstitium) on the one hand and the altered renal function on the other. The presence of atubular glomeruli also explains the irreversibility of chronic renal diseases.(ABSTRACT TRUNCATED AT 400 WORDS)     

Morphometric analysis of the glomerular capillary area--a comparison of minimal change nephrotic syndrome, focal glomerular sclerosis, and pre-eclampsia.

A morphometric analysis was performed to compare the capillary area in non-sclerotic glomeruli in focal glomerular sclerosis (FGS), pre-eclampsia with focal sclerotic change of the glomeruli, and minimal change nephrotic syndrome (MCNS). The mean and standard deviation of the capillary area was greater in FGS than in pre-eclampsia and MCNS. Tubulo-interstitial lesions, such as tubular atrophy, interstitial fibrosis, and lymphocytic infiltration, were more severe in FGS than in pre-eclampsia. The presence of tubulo-interstitial changes including tubular atrophy and interstitial fibrosis with lymphocytic infiltration is thought to be an important prognostic factor in pre-eclampsia as well as in FGS. Unequal dilatation of the glomerular capillaries in non-sclerotic glomeruli may be harmful to the glomeruli and may lead to the development of glomerular sclerosis.     

Ferritin deposition in the glomerular deposits of focal glomerular sclerosis in the rat

The glomerular lesions of focal sclerosis clinically associated with a steroid-resistant nephrotic syndrome, are of unknown origin. IgM and C3 deposits and electron dense material found in areas of sclerosis are not convincing evidence of an immune pathogenesis. These deposits have been studied in a rat model of focal sclerosis induced by uninephrectomy and repeated aminonucleoside administration. Sclerotic lesions closely resembling human disease developed in the remaining kidney. There was a severe progressive proteinuria. Seventy-eight days after initial aminonucleoside injection 65 per cent of glomeruli were sclerotic with IgM, IgG, C3 and fibrinogen deposits, and electron dense deposits by electron microscopy. To study macromolecule deposition in this model of focal sclerosis, ferritin uptake 4 and 24 h after intravenous ferritin given at 77 days was compared in focal sclerosis rats with control rats without sclerosis (uninephrectomy plus saline-only injections). In focal sclerosis rats sclerotic areas contained massive accumulations of ferritin. In unaffected segments of sclerotic glomeruli, and normal glomeruli of focal sclerosis rats, ferritin concentration was no different from controls. Abnormal ferritin trapping in areas of sclerosis suggests that the presence of IgM and C3 may be due to a similar mechanism, and is not indicative of an immune pathogenesis for focal sclerosis.     

Progressive glomerulosclerosis develops in transgenic mice chronically expressing growth hormone and growth hormone releasing factor but not in those expressing insulinlike growth factor-1.

An increase in glomerular size occurs in normal maturation after subtotal renal ablation and disease states such as diabetes mellitus. The role that growth hormone (GH), growth hormone releasing factor (GHRF), and insulinlike growth factor-1 (IGF-1) play in these processes has been investigated using transgenic mice chronically expressing these hormones. The glomeruli were enlarged in all 3 strains of mice. Mesangial proliferation followed by progressive glomerulosclerosis was observed in the GH and GHRF animals only. In the IGF-1 mice the large glomeruli remained morphologically normal except for the enlargement. These data suggest that the glomerulosclerosis was due, in part, to disordered mesangial cell growth in response to circulating GH. The mesangial lesions in mice with chronically high plasma GH levels mimicked those in human diabetes mellitus. These models provide a means to study the hormonal regulation of glomerular growth and the role that specific hormones might play in the pathogenesis of glomerulosclerosis.     

Role of differential and cell type-specific expression of cell cycle regulatory proteins in mediating progressive glomerular injury in human IgA nephropathy

The activities of cell cycle regulatory proteins have been reported to be associated with the development of pathological lesions in glomerulonephritis. To assess the cellular mechanisms underlying the mesangial cell proliferation and glomerulosclerosis in progressive human IgA nephropathy (IgAN), we examined the expression of E2F1, Rb, c-Myc, proliferating cell nuclear antigen (PCNA), cyclins (D1, E and A), cyclin-dependent kinase 2 (CDK2) and CDK inhibitors (p21(waf1), p27(kip1), 57(kip2) and p16(ink4a)) by immunohistochemistry in renal biopsy specimens. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) was also performed to detect the presence of apoptosis. In total, 51 cases of IgAN were categorized into four subgroups according to histological severity. A dramatic upregulation of E2F1 expression in mesangial cells was identified in proliferating glomeruli, which correlated well with the proliferation index. High endogenous expression of p27(kip1) and p57(kip2) by podocytes in normal glomeruli and glomeruli with minor lesions was observed to decrease in proliferating and sclerosing glomeruli; this pattern displayed a strong inverse correlation with the mean glomerulosclerosis score and the index of glomerular lesion. Increased apoptotic activity was identified in progressive glomerular lesions of advanced IgAN, which correlated with the proliferative activity in these lesions as assessed by total expression levels of PCNA and CDK2 in glomeruli, E2F1 expression levels in the mesangium, cyclin D1 expression levels in endothelium and the c-Myc glomerular staining score. Our results suggest that the onset and magnitude of mesangial cell proliferation and glomerulosclerosis is associated with the upregulation of E2F1 by mesangial cells and the downregulation of p27(kip1) and p57(kip2) by glomerular epithelial cells. The cell type-specific and coordinated regulation of proliferative and proapoptotic activities of cell cycle regulatory proteins may play an important role in mediating progressive glomerular injury in human IgAN.     

Glomerular hypertrophy and epithelial cell injury modulate progressive glomerulosclerosis in the rat

The effects of glomerular size and visceral epithelial cell integrity upon the development of progressive glomerulosclerosis was studied by superimposing renal ablation on adriamycin-induced nephropathy in rats. Adriamycin alone caused focal epithelial cell injury and proteinuria but minimal segmental glomerulosclerosis. In normal rats, renal ablation was accompanied by mild progressive proteinuria and glomerulosclerosis. However, renal ablation in rats with adriamycin nephropathy caused a dramatic increase in proteinuria and a disproportionately high frequency of segmental glomerulosclerosis. Accelerated glomerular injury after renal ablation in adriamycin-treated rats was associated with substantial glomerular hypertrophy with near doubling of the tuft volume. Morphometric and autoradiographic studies showed that compensatory glomerular hypertrophy occurs without a proportional increase in the number of visceral epithelial cells, leading to a substantial reduction in the density of these cells within the capillary tuft. The severity of segmental glomerulosclerosis showed a significant correlation with the glomerular volume and the reciprocal of the visceral epithelial cell density. Ultrastructural observations indicate that epithelial defects with detachment of the cell processes from the underlying basement membrane are almost invariably seen in areas of segmental glomerulosclerosis with hyalinosis. These findings suggest that the process of progressive glomerulosclerosis is, to a great extent, contingent upon the development of epithelial cell defects, that result from direct injury or from a reduction in the cell density after inordinate compensatory glomerular hypertrophy.     

Morphological alterations of glomerulus induced by infusion of cationized ferritin

Morphological alterations of the glomerulus were induced by infusion of cationized ferritin. After a direct injection of highly cationized ferritin (CF) into the left kidney of rats, endothelial injuries were followed by activation of platelets and the coagulation system after 1-2h, which occluded capillary loops. In most glomeruli, resolving processes occurred from 2 h onward, leaving a mild thickening of the mesangial region at 7 days. On the other hand, in severely involved glomeruli, capillary loops were still obstructed even at 24 h by hypertrophic and proliferated endothelial cells as well as mesangial cells, instead of platelets and fibrin strands. After this period, exfoliation of podocytes and endothelial cells occurred over a wide area, which resulted in glomerular obsolescence at 7 days. These progressive glomerular injuries were assumed to be closely related to the persistence of CF in glomeruli, which might be caused by disturbances of glomerular clearing systems. Mild proteinuria was only noticed in severely involved cases. It is concluded that an assault on glomerular endothelial cells by cationic macromolecules can cause thrombotic complications leading to glomerular obsolescence.