Glomerular sclerosis in Wistar rats: analysis of its variable occurrence after unilateral nephrectomy.

Individual differences in susceptibility to the development of focal and segmental glomerular hyalinosis and sclerosis (FSGHS) were studied in rats after unilateral nephrectomy. A total of 20 male Wistar rats underwent unilateral nephrectomy at 3 months of age. Glomerular number in the removed kidney ranged from 17,000 to 32,700 with a mean value of 25,997 (n = 19). At death 30 weeks later, the incidence of glomeruli with FSGHS in the remaining kidney varied from 0 to 20% with a mean of 4.4%. However, the percentage of glomeruli with FSGHS and the degree of proteinuria did not correlate either with glomerular number per kidney (left and right kidneys were shown to be equivalent for glomerular number) or with glomerular volume on killing. The occurrence of FSGHS correlated significantly with mean protein excretion (P less than 0.01) and serum cholesterol levels (P less than 0.01). In conclusion, in the rat a relatively low number of nephrons in the kidneys does not increase susceptibility to the development of FSGHS.     

Number of glomeruli in normal and hypertrophied kidneys of mice and guinea-pigs.

1. In mice and guinea-pigs, the number of glomeruli was counted in kidneys during normal growth and in hypertrophy induced by unilateral nephrectomy. 2. In mice, the number of glomeruli increased sharply during the first 2 weeks in life, and more slowly afterwards. Unilateral nephrectomy, when performed during this period of natural increase, induced the formation of supplementary nephrons in the contralateral kidney. 3. In guinea-pigs, the number of glomeruli was almost complete at birth. No evidence of a supplementary increase in the number of nephrons was found in hypertrophied kidneys following unilateral nephrectomy. 4. These results, together wit previous data obtained in the rat, suggest that the ability to induce new nephrons after unilateral nephrectomy in different species would depend more on the state of kidney maturity at birth than on differences in the renal mechanisms which lead to hypertrophy.     

Focal segmental glomerular hyalinosis and/or sclerosis in rats with congenital unilateral hydronephrosis.

Focal segmental glomerular hyalinosis and/or sclerosis (FSHS) was observed in five Wistar-Imamichi rats with congenital unilateral hydronephrosis (CUH rats). Marked proteinuria (164.9 +/- 138.4 mg/day) was observed in the CUH rats. Immunoperoxidase staining for IgM, C3 and IgG was positive in the glomeruli, showing in a focal, segmental pattern that corresponded to the areas of FSHS seen by light microscopy. These glomerular findings were extremely similar to those of human focal glomerular sclerosis (FGS). FSHS was found to be common to both the hydronephrotic kidney and the contralateral kidney without hydronephrosis. Morphometry revealed that the glomerular area of the juxtamedullary glomeruli was greater than that of superficial glomeruli in control rats (11,037 micron2 vs. 6,847 microns2). On the other hand, glomerular hypertrophy was observed in non-sclerotic glomeruli of CUH rats (superficial glomeruli; 12,477-16,123 microns2, juxtamedullary glomeruli; 14,635-18,418 microns2). Also, a decreased in the number of glomeruli within the range 1.8-4.1 per unit area (1 mm2) was seen in CUH rats compared with control rats (mean 4.4). These results suggest that the increased rate of development of FSHS is based on hyperfiltration in the remaining functional nephrons.     

Induction of glomerulosclerosis by dietary lipids. A functional and morphologic study in the rat

Clinical and experimental data indicate that glomerular function and morphology may be influenced by plasma lipids. In familial lecithin-cholesterol-acyltransferase (LCAT) deficiency and in Fabry's disease, lipids accumulate in glomeruli and are assumed to induce sclerosis. The present study was undertaken to examine if dietary lipids could exert effects on the glomeruli of normal, unilaterally nephrectomized rats, and of rats with two-kidney, one clip (2-K,1C) hypertension. In rats with two kidneys on a diet rich in fat and cholesterol, cholesterol concentrations in very low density lipoproteins increased. In these rats the number of glomeruli with sclerotic foci was significantly higher than in rats on a low fat, cholesterol free diet. After 6 months on the diet the percentage of glomeruli with sclerosis (SC) was 13.2 +/- 4.1 (N = 9) in rats with a cholesterol diet and 1.8 +/- 0.6 (N = 11) in control rats (p less than 0.05). The fat and cholesterol diet exacerbated glomerular lesions in the remnant kidney model of uninephrectomized rats. The sclerosis in rats with only one kidney was 38.2 +/- 9.5 (N = 6) on a cholesterol diet compared with 8.7 +/- 3.0 (N = 6) in control rats after 6 months (p less than 0.05). After 3 to 4 months on a fat rich diet cholesterylester was increased in isolated glomeruli. The composition of the dietary lipids influenced the development of glomerular lesions. A linseed oil diet that is rich in unsaturated fatty acids, especially linolenic acid, did not cause major plasma lipid abnormalities and was accompanied by a low sclerosis (1.2 +/- 0.3; N = 9) for rats with two kidneys. In rats with chronic 2-K, 1C hypertension the percentage of glomeruli with partially sclerosed tufts in the unclipped kidney was significantly higher on a fat and cholesterol diet (F) than on a control diet (N) (SC: diet F 31.0 +/- 4.0, N = 13; diet N 12.2 +/- 2.6, N = 12; P less than 0.05). In the clipped kidney, protected against the arterial hypertension, only an increased number of glomeruli with mesangial expansion was noted in rats with the cholesterol diet. Glomerular hemodynamic factors seem to play an important pathogenetic role in the induction of glomerular sclerosis by a lipid rich diet. The fact that dietary lipids can aggravate glomerular lesions in states of arterial hypertension and nephron loss may have implications for the progression of renal disease in humans.     

Messenger RNA Expression for Growth Factors in Glomeruli from Focal Glomerular Sclerosis

Focal glomerular sclerosis was induced in rats by chronic injections of puromycin aminonucleoside (PAN) on Days 0, 27, 34, and 41 and by unilateral nephrectomy on Day 22. Rats were sacrificed on Days 0, 8, and 20 (acute phase) and on Days 48, 60, and 80 (sclerotic phase). The percentage of sclerosing glomeruli was 16.6% on Day 48 and increased significantly to 72.8% on Day 80. We examined glomerular mRNA levels for proliferating cell nuclear antigen (PCNA), platelet-derived growth factor (PDGF)-A and B chains, transforming growth factor (TGF)-β, epidermal growth factor (EGF), insulin-like growth factor (IGF)-I, and basic fibroblast growth factor (bFGF) on Days 0, 8, 20, 48, 60, and 80. Although these growth factor mRNA levels showed little change in glomeruli until Day 20, all growth factor mRNA levels increased in glomeruli during the sclerotic phase of PAN nephrosis as glomerular sclerosis progressed. On Day 80, mRNA levels for PCNA, PDGF-A and B chains, TGF-β, EGF, IGF-I, and bFGF increased 12-, 10-, 12-, 15-, 2-, 2-, and 8-fold, respectively, in the glomeruli of PAN-treated rats with marked glomerular sclerosis when compared with control rats. Unilateral nephrectomy without PAN administration did not cause glomerular sclerosis up to Day 80 and mRNA levels for PCNA, PDGF-A and -B chains, TGF-β, EGF, IGF-I, and bFGF in this group were almost the same as those in the normal sham-operated group. These data suggest that changes in growth factor mRNA levels in glomeruli may contribute to the development of PAN-induced glomerular sclerosis.     

Effect of cholesterol on the position of segmental lesions in unilaterally nephrectomized rats.

Different positions of segmental lesions within glomeruli may correspond to different pathogenetic mechanisms. The effect of a high cholesterol diet on the position of lesions had not previously been investigated. This was studied in rats following unilateral nephrectomy, as a change in position would suggest a different mechanism of damage. Thirty-two female WAG/ola rats had unilateral nephrectomy. Half the rats were given a diet supplemented with 4 per cent cholesterol and 1 per cent cholic acid. At death, six at 10 weeks after nephrectomy and the rest at 24 weeks, kidney sections were examined microscopically. There were significantly more segmental lesions in the cholesterol-fed rats than in the controls, and these lesions were almost entirely at the glomerular hilum in both groups. Significantly more glomeruli contained foamy cells in the cholesterol-fed group, both within lesions and away from them. These findings confirmed that in reduced renal mass, segmental lesions are mainly hilar. The diet increases the number of glomeruli affected by lesions, but these are still mainly hilar. Therefore one possibility is that hypercholesterolaemia worsens the hyperfiltration effect on glomeruli. The diet also produces foamy cells scattered throughout the glomeruli but these do not appear to develop into segmental lesions.     

Focal Segmental Glomerular Hyalinosis and/or Sclerosis in Rats with Congenital Unilateral Hydronephrosis

Focal segmental glomerular hyalinosis and/or sclerosis (FSHS) was observed in five Wistar-Imamichi rats with congenital unilateral hydronephrosis (CUH rats). Marked proteinuria (164.9+138.4mg/day) was observed in the CUH rats. Immunoperoxidase staining for IgM, C3 and IgG was positive in the glomerull, showing in a focal, segmental pattern that corresponded to the areas of FSHS seen by light microscopy. These glomerular findings were extremely similar to those of human focal glomerular sclerosis (FGS). FSHS was found to be common to both the hydronephrotic kidney and the contralateral kidney without hydronephrosis. Morphometry revealed that the glomerular area of the juxtamedullary glomeruli was greater than that of superficial glomeruli in control rats (11,037 μm² vs. 6,847 μm²). On the other hand, glomerular hypertrophy was observed in non-sclerotic glomeruli of CUH rats (superficial glomeruli; 12,477–16,123 μm², juxtamedullary glomeruli; 14,635–18,418 μm²). Also, a decreased in the number of glomeruli within the range 1.8-4.1 per unit area (1 mm²) was seen in CUH rats compared with control rats (mean 4.4). These results suggest that the increased rate of development of FSHS is based on hyperfiltration in the remaining functional nephrons. Acta Pathol Jpn 41: 653–660, 1991.     

Intraglomerular thrombotic tendency and glomerular ADPase. Unilateral impairment of ADPase elicits a proaggregatory microenvironment in experimental glomerulonephritis

It has been proposed, predominantly from ex vivo studies, that glomerular ADPase may function as an antithrombotic principle within the rat kidney. Therefore, intraglomerular platelet aggregation was studied in vivo in rats after impairment of glomerular ADPase activity using local X-irradiation (20 Gy). Biochemical assays in suspensions of glomeruli obtained from rats 24 hours after local X-irradiation (group I) demonstrated a significant reduction in ADPase activity as compared to sham treated rats (group II; p less than 0.01). Cytochemical observations at the ultrastructural level showed that this reduction in glomerular enzyme activity represents in particular ADPase activity detectable in the basement membrane. Following X-irradiation, intraglomerular platelet aggregation was quantitatively studied in two groups of rats. Both groups received X-irradiation of the left kidney (20 Gy). Twenty-four hours after X-irradiation, animals received an intravenous injection of either 0.5 ml of saline (group III; N = 6) or 0.5 ml of heterologous nephrotoxic serum (NTS; group IV; N = 6). Subsequently, 24 hours after this injection, platelet aggregation in left kidneys was compared with aggregation in contralateral non-X-irradiated kidneys. The results showed that while X-irradiation per se did not induce intraglomerular platelet aggregation as compared with the contralateral kidney (0.20 +/- 0.08% versus 0.17 +/- 0.06% platelet aggregation/glomerulus), a significant increase in platelet aggregation could be demonstrated in X-irradiated kidneys in the early phase of nephrotoxic serum nephritis as compared with the contralateral nephritic kidney (2.45 +/- 0.66% versus 1.37 +/- 0.35% platelet aggregation per glomerulus; p less than 0.005). A potential effect of altered influx of inflammatory cells after X-irradiation could be excluded since no difference in H2O2 producing cells was observed between left and right kidneys. Thus, while ADPase impairment by X-irradiation does not induce platelet aggregation per se, it is clear that in proaggregatory conditions, like in NTS nephritis, the thrombotic tendency, due to decreased glomerular ADPase, is enhanced. These results demonstrate the functional significance of glomerular ADPase activity as an antithrombotic principle following platelet activation in vivo.     

Quantitation of the intrarenal uptake of immunoglobulin aggregates by macrophages in diffuse proliferative glomerulonephritis.

The intrarenal processing of circulating immune-complex-like-material is traditionally attributed to resident glomerular mesangial cells. To assess the contribution of infiltrating mononuclear cells to macromolecule processing by diseased glomeruli we have utilized an isolated perfused kidney system (IPK) to quantify the specific glomerular uptake of heat-aggregated immunoglobulin (AIgG) (as micrograms of aggregated IgG per 10(4) glomeruli (microgram 10(4)glom)). Mononuclear cell infiltrated glomeruli from animals with diffuse proliferative glomerulonephritis had a significantly augmented uptake of AIgG (48.9 +/- 3.8 micrograms/10(4)glom; normal 11.8 +/- 0.6 micrograms/10(4)glom; P less than 0.01). Specific blockade of mononuclear cell function by perfusion with anti-macrophage-serum (AMS) prevented increased AIgG uptake (12.8 +/- 1.2 micrograms/10(4)gloms; P less than 0.01), but had no effect on the AIgG uptake of normal kidneys (13.1 +/- 1.2 micrograms/10(4)glom). Thus, in diffuse proliferative glomerulonephritis the observed increase in the glomerular clearance of AIgG was due to phagocytosis by mononuclear cells. This study suggests that infiltrating, bone-marrow derived mononuclear cells may significantly contribute to the glomerular handling of circulating immune complexes by nephritic glomeruli.     

Impairment and recovery of the clipped kidney in two kidney, one clip hypertensive rats during and after antihypertensive therapy

Earlier experiments have shown that in sodium depleted hypertensive rats with bilaterally constricted renal arteries the arterial pressure normalized after blockade of the renin-angiotensin system; simultaneously acute renal failure occurred. In hypertensive rats with unilateral renal artery stenosis an impaired excretory function of the clipped kidney can be expected, but may not be detectable by conventional tests of renal function. Male Wistar rats with chronic two kidney, one clip hypertension were fed a low sodium diet. After 7 days the rats were treated with vehicle, with the vasodilator dihydralazine, or with the angiotension converting enzyme inhibitor MK 421 for 2 weeks. During the 14-day treatment period a continuous blood pressure reduction was achieved in dihydralazine and MK 421 treated rats. Overall excretory kidney function (plasma creatinine concentration) was well maintained in all three groups until the end of the antihypertensive drug treatment. At the end of drug therapy mean glomerular filtration rates of the left clipped kidneys were significantly lower in both treated groups compared to hypertensive controls, and mean glomerular filtration rate of the left clipped kidneys of dihydralazine treated rats was significantly higher than in MK 421 treated rats: controls (N = 6) 1.03 +/- 0.03, dihydralazine-group (N = 10) 0.28 +/- 0.07, MK 421-group (N = 9) 0.03 +/- 0.01 ml/min. Renal blood flows were comparable in both treated groups. Only the left kidneys of rats treated with MK 421 showed a prominent tubular atrophy. Seven days after declipping of the left renal artery and right nephrectomy a considerable restitution of the tubular structure had occurred in the MK 421-group. The recovery of tubular epithelial cells was paralleled by a rise in glomerular filtration rate: MK 421 group (N = 7) 1.25 +/- 0.08 ml/min. Thus, the clipped kidney in two kidney, one clip hypertensive rats showed functional and morphological signs of impairment when systemic arterial pressure was reduced to the normal range. The alterations of the clipped kidney were most pronounced in rats with renin-angiotensin system-blockade.     

Glomerular immune deposits in kidneys from patients with no clinical or light microscopic evidence of glomerulonephritis. Assessment of the influence of autolysis on identification of immunoglobulins and complement.

Using a direct fluorescent staining technique, immunofluorescent microscopy (IFM) demonstrated glomerular deposits of IgG and IgM and/or fractions of complement in kidney tissue from 24% of 33 patients examined post mortem and in 39% of kidney biopsies obtained from 23 patients on lithium treatment. All the patients investigated had a normal blood pressure. There was no evidence of glomerulonephritis (GN) neither clinically, at light microscopy, nor on laboratory investigation. These "spontaneously" deposited immunoglobulins and complement fractions in glomeruli will obviously by demonstrated in kidney biopsies from patients with GN, even though they bear no relation to the disease. This will therefore preclude an immunopathological classification which relates to histological and clinical findings. A control study of the IFM findings in glomeruli on 13 surgically removed kidneys showed optimal identification and no further glomerular deposition of immunoglobulins during the 72 hours following nephrectomy, at temperatures below 10 degrees C. Clq and C3 were less stable and were only demonstrated with certainty up to 24 hours after nephrectomy.     

Reactive oxygen species mediate compensatory glomerular hypertrophy in rat uninephrectomized kidney

Hyperfiltration in glomeruli is the most common pathway to progressive renal dysfunction. Moreover, reduction of renal mass by unilateral nephrectomy results in an immediate increase in glomerular flow to the remnant kidney, followed by compensatory glomerular hypertrophy. Reactive oxygen species (ROS) are involved in renal hypertrophic responses; however, the role of ROS in compensatory glomerular hypertrophy remains unclear. Therefore, this role was investigated in the present study. Wistar rats were randomly placed into two groups: uninephrectomized rats (Nx) and uninephrectomized rats treated with tempol (Nx + TP). The glomerular volume increased in the Nx 1 week after surgery, but was significantly suppressed in the Nx + TP. Levels of phospho-Akt and phospho-ribosomal protein S6, which are critical for cell growth and hypertrophy, were markedly increased in the glomeruli of the Nx, while tempol treatment almost abolished the activation of these proteins. These results suggest that ROS have important roles in compensatory hypertrophy in glomeruli. M. Ozeki and H. Nagasu have contributed equally to this study.     

回输转染饰胶蛋白聚糖基因的肾系膜细胞对大鼠抗thy-1血清性肾炎的拮抗作用

目的以转染饰胶蛋白聚糖(decorin)基因的肾系膜细胞(MSC)为载体,经肾动脉回输入抗thy-1血清性肾炎大鼠肾小球,观察其存活情况及对模型大鼠肾小球病变的影响及意义。方法用脂质体介导法将载有目的基因(decorin)片段转入正常,MSC株而获得阳性表达之细胞克隆;经尾静脉注射兔抗大鼠thy-1血清(ATS)复制其抗thy-1系膜增生性肾炎模型;经左肾动脉将转基因MSC回输入thy-1肾炎大鼠肾小球,并经该鼠MsC原代培养、BrdU和decorin蛋白免疫组织化学染色结合图像分析观察其生存情况;应用转化生长因子β1(TGF-β1)、纤连蛋白和Ⅳ型胶原免疫组织化学结合图像分析研究对thy-1系膜增生性肾炎动物模型肾小球病变的影响。结果经制备兔抗大鼠ATS,将其从尾静脉注入大鼠体内成功复制thy-1系膜增生性肾炎模型。经左肾动脉直接注入转染decorin基因的．MSC克隆(D-A6),经原代培养证实其生长活跃,用免疫组织化学法发现其细胞核和细胞质均可分别表达BrdU和decorin蛋白。与未经注射对侧肾相比,回输侧肾的肾小球TGF-β1、纤连蛋白和Ⅳ型胶原的表达均降低,分别为TGF-β1 4d时P＜0．05和纤连蛋白、Ⅳ型胶原1～2d时P＜0．01。结论通过肾动脉直接输入法将转染decorin基因的细胞克隆回输入大鼠抗thy-1血清性肾炎肾小球内,并观察到对病变肾小球的拮抗作用,这为肾小球肾炎动物模型的基因治疗提供实验依据。     

Glomerulosclerosis and hyalinosis in rabbits.

Histological appearances of remnant kidney in female New Zealand white rabbits undergoing left nephrectomy at 6 mths were studied. All 20 rabbits had evidence of previous Encephalitozoon cuniculi (E. cuniculi) infection. Half of the 10 uninephrectomized and 10 control animals completed 3 pregnancies before sacrifice (15 mths). Twelve of 30 kidneys at sacrifice showed focal and segmental hyalinosis and sclerosis (FSHS), a lesion not previously reported in rabbits. Four of 5 kidneys in both uninephrectomized pregnant and uninephrectomized virgin animals showed FSHS compared with 2 of 10 in both control pregnant and non-pregnant rabbits (p = 0.0026). More glomeruli were sclerosed in control pregnant (median 3.5%) than non pregnant animals (median 0.4%) (p < 0.005). Median right kidney weights per kilogram body weight were greater in previously nephrectomized animals (3.9 gm/kg) than controls (2.6 gm/kg), (p < 0.001). Absolute glomerular area was increased in hypertrophied kidneys, however, after correction for kidney weight, glomerular area was smaller in previously uninephrectomized animals than controls (p < 0.0001).     

Glomerular number and size in relation to age, kidney weight, and body surface in normal man.

The number and size of glomeruli in normal, mature human kidneys were estimated by a direct and unbiased stereological method, the fractionator. The number was 617,000 on average, and the mean size 6.0 M microns3. Both glomerular number and size showed significant negative correlation to age and significant positive correlation to kidney weight. Apparently, humans loose glomeruli with age. Body surface area correlated positively to kidney weight and total glomerular volume but not to number of glomeruli. Body surface area correlates significantly with metabolic rate (Robertson and Reid, Lancet, 1: 940-943, 1952). Thus, intraspecies adaptation of kidney filtration capacity to the metabolic demand is performed by changing the size of glomeruli, i.e., the number of glomeruli in individuals of a given species is independent of the metabolic rate.     

Twin-glomeruli and duplication of glomerular capillary tuft in human kidneys

Since the turn of this century the term twin-glomeruli (TG) designates a pair of glomerular capillary tufts supplied by a single afferent arteriole. Screening for TG has been performed in a series of kidney slides from 200 unselected consecutive autopsy cases with 21 (10.5%) positive results. Serial sectioning of 21 TG-positive and 10-TG-negative kidneys revealed the frequency of TG = 0.48% (71 among 15035 glomeruli) in the first group and 0.38% (32 TG among 8241 glomeruli) in the second. In individual cases the frequency ranged from zero up to 1.73% of all glomeruli. Three types of TG could be distinguished according to the distance between glomerular hili and the degree of Bowman's capsules coalescence. A complicated spatial relationship between the glomerular vessels and surrounding tubules was demonstrated by plastic reconstructions. TG are believed to be of a variety of renal architecture probably occurring in every human kidney. On the other hand, the glomeruli with two, mostly incomplete capillary tufts, which are occasionally found in the kidneys of newborns and children with multiple malformation syndromes and kidney dysplasias, are supposed to give evidence of a disturbed development of the kidneys.     

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 function and pathology following extreme ablation of renal mass.

The role of the pathologic features and dysfunction of glomerular epithelial cells (GECs) in the pathogenesis of glomerular scarring was studied in the remnant kidney model (RK) (1 and 5/6 nephrectomy) in rats. Three weeks after surgery serum creatinine was greater in the RK than either sham-operation controls (SHAM) or spontaneously hypertensive rats (SHRs). Blood pressure was higher in the RK (181 +/- 26 mm Hg) than in SHAM (129 +/- 17, P less than 0.05) but not SHR (195 +/- 15, P less than 0.05). GEC endocytosis, assessed by protamine heparin aggregate (PHA) disappearance (10), was not different from that in SHAM. Glomerular damage was greater in RK (glomerular damage index, 30 +/- 18) than in SHAM animals (4 +/- 3, P less than 0.05) and SHR (0, P less than 0.05), and 2 of 11 RK animals had fibrinoid necrosis and thrombosis of arterioles and glomeruli. Segmental sclerosis occurred in only 1 RK animal (0.6% of glomeruli). Six weeks after surgery serum creatinine and urinary protein excretion remained higher in the RK than in the SHAM animals. Blood pressure was higher in RK (158 +/- 34 mm Hg) than in SHAM animals (144 +/- 24), but the difference was not significant. PHA disappeared from the glomerulus at a slower rate in RK than in SHAM animals (outside the 95% confidence limits of SHAM). Glomerular pathology was more widespread in RK than in SHAM animals (glomerular damage index, 73 +/- 62 versus 3 +/- 8, P less than 0.05), and 4 of 11 animals had acute hypertensive injury in arterioles and glomeruli. Segmental glomerular sclerosis was only seen in the animals with necrotic glomeruli. GEC dysfunction is not demonstrable until long after proteinuria and hypertension are established, and it only occurs in the context of severe, acute glomerular injury when the epithelial cells separate from the capillary wall and undergo severe degenerative changes and necrosis. The acute glomerular and vascular lesions in the RK model are morphologically similar to malignant nephrosclerosis in humans. Segmental glomerular sclerosis occurs only after proteinuria is well established in the context of severe glomerular injury, and it appears to represent, at least partially, progression of more proximate glomerular capillary injury.     

Glomerular number and size in relation to age,kidney weight,and body surface in normal man

The number and size of glomeruli in normal, mature human kidneys were estimated by a direct and unbiased stereological method, the fractionator. The number was 617,000 on average, and the mean size 6.0 M μm³. Both glomerular number and size showed significant negative correlation to age and significant positive correlation to kidney weight. Apparently, humans loose glomeruli with age. Body surface area correlated positively to kidney weight and total glomerular volume but not to number of glomeruli. Body surface area correlates significantly with metabolic rate (Robertson and Reid, Lancet, 1: 940–943, 1952). Thus, intraspecies adaptation of kidney filtration capacity to the metabolic demand is performed by changing the size of glomeruli, i. e., the number of glomeruli in individuals of a given species is independent of the metabolic rate.