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.

Renin-angiotensin system in neonatal rats: induction of a renal abnormality in response to ACE inhibition or angiotensin II antagonism.

In experiments designed to analyze cardiovascular structure in response to antihypertensive therapy with an ACE inhibitor, we decided to start very early in life with the aim to prevent blood pressure increases and the development of vascular structural changes. In these treated groups of rats we unexpectedly observed that after they were weaned, their water consumption and urine volume, respectively, increased substantially. The present study was designed to determine if inhibition of the renin-angiotensin system produced similar effects in different strains of rats, and focused on characterizing the abnormal fluid balance occurring as a consequence to neonatal treatment with ACE inhibitors or angiotensin II blockers. Three-day-old Wistar Kyoto (WKY), Wistar (WR) and spontaneously hypertensive rats (SHR) were given either saline, enalapril, captopril, losartan and the AT2 blocker, PD123319, in the same amount of volume for 20 days. Treatment was stopped and rats were examined with regard to renal morphology at 4, 14 and 30 weeks of age. In addition, water consumption, urine volume, urine electrolytes and osmolality were analyzed at 14 weeks of age, that is, 10 weeks off treatment. Early treatment with the ACE inhibitors, enalapril and captopril, and the AT1 blocker, losartan, but not the AT2 blocker, PD 123319, in the SHR and in the normotensive strains WKY and WR produced persistent, irreversible histopathological renal abnormalities in adult life, long after the rats had been taken off treatment. These abnormalities consisted of mainly cortical tubulointerstitial inflammation, various degrees of papillary atrophy and pelvic dilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclosporin A nephropathy: standardization of the evaluation of kidney biopsies.

An advisory board of nephropathologists with personal experience in the evaluation of biopsies from patients treated with cyclosporin A (CyA) was set up to address the following problems: 1. Definition of CyA nephropathy as seen in patients with autoimmune diseases; 2. Evaluation of the reliability and reproducibility of the diagnostic criteria for the different morphological lesions seen in CyA nephropathy; 3. Classification of the morphological lesions according to their clinical relevance; 4. Estimation of the possible progression of CyA nephropathy with continuous CyA therapy. The most frequent lesions attributable to CyA therapy in patients with autoimmune diseases are tubular atrophy, interstitial fibrosis, and arteriolar hyalinosis. All other lesions are rare. The reproducibility and diagnostic reliability is high for tubular atrophy and interstitial fibrosis, but low for arteriolar lesions even among experienced nephropathologists. The biopsies may be classified according to the severity of tubular atrophy, interstitial fibrosis and arteriolar hyalinosis with regard to their clinical relevance: In group I (within normal limits), CyA therapy can be continued; in group III (moderate-to-severe CyA-related lesions), CyA should be stopped if possible. Among group II biopsies (slight CyA-related abnormalities), no recommendation can be made in the absence of a second biopsy after a further year of CyA therapy. No clear-cut answer can be given concerning the progression of CyA-induced lesions. However, no significant progression has been found in the cases studied to date.

Proteinuria and renal function in relation to renal morphology. A clinicopathological study of IgA nephropathy at the time of kidney biopsy.

At the time of kidney biopsy the pattern of urinary protein excretion (UPE) and renal function were studied in 54 patients (age 16-62 years) with IgA nephropathy (IgAN). Serum and urinary albumin (alb), IgG, beta-2-microglobulin and creatinine were analysed, and excretion rates (UV) and clearances were calculated. The glomerular filtration rate (GFR) was determined by plasma 51Cr-EDTA clearance (51Cr-EDTA) and by 24-hour creatinine clearance (C-Cr 24 h). Glomerular mesangial (volume expansion and cell proliferation), tubulo-interstitial (fibrosis and inflammation) and vascular lesions were classified semiquantitatively on a five-degree scale, and the percentage of glomeruli showing global sclerosis, segmental sclerosis and cellular crescents was calculated. One third of our patients had reduced renal function, three patients uremia and 70 per cent of the patients overt albuminuria. The mean GFR was reduced in microalbuminurics and further decreased in albuminurics and nephrotics. A lower GFR and more proteinuria were found in the patients with more advanced morphological lesions also when the uremic patients were excluded. Segmental glomerular sclerosis correlated with GFR as well as with UalbV and UIgGV, while global sclerosis correlated only with GFR. UalbV and UIgGV also correlated with the extent of interstitial damage but not with mesangial lesions. In summary an accurate determination of GFR and UPE at the time of the kidney biopsy may give an indication of the extent of renal damage. A lowered GFR was also found in mild proteinuria.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of the renal medulla and early treatment with enalapril upon the development of hypertension in young spontaneously hypertensive rats.

OBJECTIVE: To investigate the role of the renal medulla in early hypertension in spontaneously hypertensive rats (SHR), and to explore whether the attenuated increase of pressure induced by enalapril treatment is affected by chemical medullectomy. DESIGN: Forty-four male SHR were studied from 5 to 18 weeks of age: 22 remained intact; 22 were medullectomized at 5.5 weeks of age with 2-bromoethylamine hydrobromide; 11 of each of these two groups were treated with enalapril from 6 to 12 weeks of age. Blood pressure, heart rate and body weight were recorded intermittently, and at 18 weeks renal function was also analysed. RESULTS: The results indicate a protective effect of the renal medulla against severe pressure rises in SHR, although even when enalapril also lowered blood pressure in medullectomized SHR, persistent improvements of glomerular filtration rate and renal flow conductance occurred only in intact SHR. Furthermore, after enalapril treatment ended blood pressure rose to higher levels in medullectomized SHR, despite greater sodium-water losses. CONCLUSION: The renal medulla seems to exert a protective role both during and after enalapril treatment.

Effect of reduced cyclosporin dosage on long-term renal allograft histology.

The effect of different doses of cyclosporin (CyA) on the occurrence of histological lesions in renal allograft biopsies was investigated 2 years after transplantation. Biopsy findings were compared in three different groups of patients. In group 1, patients were immunosuppressed with CyA and prednisolone according to an early, high-dosage schedule (initial CyA dose 15-17.5 g/kg body weight); in group 2, they were treated with a medium CyA dose (initial dose 12 mg/kg), together with prednisolone; and in group 3, patients were given triple drug therapy consisting of low doses of CyA (initial dose 8 mg/kg), together with both azathioprine and prednisolone. Interstitial fibrosis and tubular atrophy were common findings in all groups, and on the basis of all biopsies, no difference could be found between the groups with respect to the relative volume of the renal cortical interstitium, which was used as a quantitative parameter for interstitial fibrosis. Likewise, no difference was found with respect to serum creatinine levels. When grafts that showed signs of rejection (usually vascular rejection) in the biopsy were excluded (two in group 1, six in group 2, and ten in group 3), the mean interstitial volume was significantly lower in group 3 (triple drug therapy) than in the other groups. The serum creatinine levels were also significantly lower in group 3 than in group 1. Thus, chronic renal lesions could be ameliorated when CyA doses were lowered, but this appeared to entail an increased risk of acute or chronic vascular rejection.

Course and long-term outcome of idiopathic IgA nephropathy in children.

The long-term outcome of idiopathic IgA nephropathy (IgAN) in children was investigated with regard to clinical course and biopsy changes. All patients with biopsy-verified IgAN (diagnosed by kidney biopsy 1970-1985) at three children's clinics in Sweden were included in the study. Thirty-four (10 females, 24 males), out of a total of 72 patients, had a follow-up period of 8 years or more (10.7 +/- 1.9 years, range 8-14). After this duration of follow-up, urine abnormalities were found in 47% (group A), proteinuria in 35%, hypertension in 9%, and decreased glomerular filtration rate (GFR) in 3% of patients. However, 53% had no clinical signs of disease (group B). GFR depression at the time of clinical presentation of IgAN was more common in group A than in group B (P = 0.017). At the first renal biopsy, which was performed after the same duration of IgAN in both groups, focal segmental glomerular changes were more often found in group A (P = 0.017), while diffuse proliferative changes were more common in group B (P = 0.031). The course of the IgAN was thus often very protracted, with some children developing hypertension as well as decreased renal function. However, after a period of 8 years or more of follow-up half of the patients did not show any clinical signs of the disease, which may indicate low disease activity or, possibly, recovery.

Renal histological changes in relation to renal function and urinary protein excretion in IgA nephropathy.

Renal function and urinary protein excretion (UPE) were investigated at the time of kidney biopsy in 24 children with IgA nephropathy. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured by clearances of inulin and para-aminohippuric acid. For UPE albumin, IgG, beta 2 microglobulin, and creatinine were analysed. Glomerular global/segmental sclerosis and crescents in the biopsy specimens were assessed, and glomerular and tubulointerstitial changes classified on a five degree scale. The patients with tubulointerstitial or mesangial biopsy changes or glomerular sclerosis had significantly lower GFR than those without corresponding lesions. Patients with segmental sclerosis also had higher excretion rates of IgG, which increased with increasing segmental sclerosis. Six patients had GFRs below 2SD of the controls. Within the group of patients with reduced GFR overt albuminuria, a raised excretion rate of IgG, interstitial fibrosis, and advanced mesangial lesions were more frequent. A rising excretion rate of IgG seems to indicate both reduced GFR and increasing segmental glomerulosclerosis and may be a marker of progressive disease.

Cytologic patterns in juice from human pancreatic transplants: correlation with histologic findings in the graft.

In 19 patients who had undergone pancreatic transplantation with temporary exteriorization of the pancreatic juice, graft tissue became available for histologic examination. In these patients the cytologic patterns in the pancreatic juice were compared with the histologic findings in the graft specimens. In five samples the diagnosis by cytologic studies was rejection. Acute rejection was confirmed in all the histologic specimens. In eight cytologic samples, graft pancreatitis was suspected because of the increased amounts of neutrophils, degenerating cells, epithelial cells, monocytes, and some macrophages, with or without necrotic tissue fragments. All eight histologic specimens showed findings characteristic of pancreatitis. In three cytologic samples, bacteria or fungi were observed. Histologic examination of these patients showed graft pancreatitis. In four patients the cytologic findings were normal. Graft histologic factors were normal in two instances. In one of these grafts there was graft pancreatitis, and in one graft chronic vascular rejection was seen. Our study shows that two different pathologic events occurring in the pancreatic graft (i.e., acute rejection and pancreatitis) are reflected by characteristic changes in pancreatic juice cytology.

Immunopathological patterns in long-term renal allografts.

Forty-eight consecutive core needle biopsies obtained 12-158 months after transplantation from 48 human renal allografts were analyzed. A conventional histological investigation and an immunohistochemical analysis of various markers of the immune system were performed, as well as cytological analyses of simultaneously obtained fine-needle aspiration biopsies. Findings were compared in grafts with excellent or reduced function and in patients who were immunosuppressed with azathioprine or cyclosporine. All the patients with excellent renal graft function (serum creatinine level less than or equal to 120 mumol/L) showed a normal picture with respect to both FNAB pattern and immunohistology, irrespective of the type of immunosuppression. Thus, the presence of inflammatory cell infiltration in a long-term renal graft suggests a pathological process of potential clinical significance. Biopsies from CsA-treated patients with reduced renal graft function (serum creatinine greater than 120 mumol/L) showing either a normal picture or focal interstitial fibrosis on histological examination were also usually normal with respect to both FNAB cytology and the immunohistological pattern. Five of 36 biopsies with reduced function showed an immunohistochemical pattern with signs of immune activation indistinguishable from those seen in early acute rejection. In cases with histological signs of chronic rejection, the immunopathological pattern varied, which suggests that different pathogenetic mechanisms were involved.

Activated eosinophil infiltration and deposits of eosinophil cationic protein in renal allograft rejection.

Eosinophil involvement in renal allograft rejection was elucidated with immunocytochemical techniques. Sections of renal biopsies were stained for immunoreactive eosinophils and extracellular deposits of eosinophil cationic protein (ECP). Activated eosinophils were identified by means of alkaline-phosphatase-linked monoclonal antibodies. In biopsies from patients with acute rejection of the interstitial type, a varying degree of eosinophil infiltration in the interstitium was seen. Minor extracellular deposits of ECP were present in areas with activated eosinophils. In acute vascular rejection, dense infiltration of activated eosinophils and secreted ECP were found in infarcted areas and in arterial walls with necrotic lesions. Dense accumulation of activated eosinophils and extracellular deposits of ECP were also seen in biopsies from non-transplanted patients with necrotizing renal vasculitides. These findings suggest that cytotoxic eosinophil granule proteins are involved in vascular injury in renal graft rejection and in necrotizing renal vasculitides. Eosinophil activation may also have a pathophysiological role in the interstitial lesions in renal graft rejection.

Magnetic resonance imaging of the transplanted kidney. Correlation to function and histopathology.

Interstitial fibrosis is a frequent finding in biopsies from long-term renal allografts, and may be due to chronic cyclosporine nephrotoxicity or chronic rejection. In this study, long-term renal transplants were investigated with magnetic resonance (MR) imaging, and the results were correlated to histopathology and graft function. Seventeen patients were investigated with MR one to 10 years after transplantation and with simultaneous ultrasonographically guided cortical needle biopsy and function tests. Histopathology included semiquantitative grading of degree of fibrosis and quantitation of ratios of tubular structures to interstitial tissue. The correlation between the histopathological assessment of interstitial fibrosis and graft function was good. Poor differentiation between the renal cortex and the renal medulla at MR imaging was correlated to high degree of interstitial fibrosis in the kidney transplants as well as to reduced graft function. MR examination may thus be of value in the evaluation of long-term renal transplants with chronic functional changes.

Do angiotensin converting enzyme inhibitors lower blood pressure in the rat partly via the humorally mediated antihypertensive system of the renal medulla?

It has been suggested that there is a negative-feedback interaction between the humoral renomedullary antihypertensive system and angiotensin II. If so, the acute blood pressure-lowering effects of angiotensin converting enzyme (ACE) inhibitors might be due, in part, to an increased secretion of renomedullary depressor substances. Groups of anaesthetized Wistar-Kyoto rats (WKY) with an intact or chemically destroyed renal medulla received either saline or the ACE inhibitor enalapril, and mean arterial pressure (MAP), heart rate and renal function were measured. MAP was clearly decreased after enalapril administration in the WKY controls with an intact renal medulla, but was not changed in the medullectomized group. In one WKY control group, where the prostaglandin and kallikrein-kinin systems had also been acutely blocked, the MAP reduction after enalapril was even more marked than in the intact controls. Thus, the acute blood pressure-lowering effect of enalapril is clearly dependent on an intact renal medulla, further suggesting that the renomedullary antihypertensive system is important to normal blood pressure homeostasis.

Fine-needle aspiration cytology and conventional histology in 200 renal allografts.

The diagnoses in 200 parallel fine-needle and core biopsies taken in acute renal allograft dysfunction, reduced function in long-term allografts, or in well-functioning grafts were compared. Fine-needle aspiration biopsy (FNAB) was found to be a reliable diagnostic tool with both a high sensitivity and specificity in acute cellular rejection (81 and 92%, respectively) and in normal kidney grafts (78 and 82%). On the other hand, the method was less valuable in the diagnosis of vascular rejection or interstitial fibrosis. Further evaluation is needed regarding the diagnostic implications of isometric vacuolization of tubular cells in FNAB specimens as a marker for acute cyclosporine nephrotoxicity.

Postnatal development of the interstitial tissue of the rat kidney.

To study the ontogenetic development of the interstitial tissue of the kidney, rats were investigated 1, 3, 7, 14, 21 and 28 days after birth. Kidneys perfusion-fixed with glutaraldehyde were studied with light- and electron microscopy. Cryostate sections from kidneys immediately frozen in liquid nitrogen were studied with respect to the expression of MHC class II antigen using the monoclonal antibody OX6. The interstitial space of both the renal cortex and the outer and inner medulla was prominent during the first days postnatally. The relative interstitial volume of the cortex and outer part of the medulla then decreased in conjunction with the outgrowth and maturation of the superficial nephrons while the inner medullary interstitium remained wide. During the first postnatal days, the abundant interstitial cells of the cortex were connected via cytoplasmic processes to form a loose network which later became less well defined. The lipid-laden interstitial cells of the inner medulla showed essentially the same ultrastructure in the newborn as in the adult animal. Strong expression of class II antigen first appeared on epithelial cells of the thick ascending limb of Henle's loop about 7 days postnatally, and became weak at 28 days. From 21 days, a weak staining of the proximal tubules was also observed. While interstitial cells in the inner medulla were always negative, cortical and outer medullary interstitial cells became strongly positive for class II antigen from day 21 post partum.

Uptake of exogenous protein tracer in cells of the rat renal papilla.

In order to study the phagocytic potential of different cell types of the rat renal papilla with special emphasis on interstitial cells, horseradish peroxidase (HRP) (8 mg/100 g body weight) was injected intravenously into adult rats. The distribution of peroxidase was studied in animals perfusion-fixed 60 and 180 min after injection and was found to be similar after both time intervals. The epithelial cells of the collecting ducts took up the largest amounts of the tracer. HRP was mainly located in large lysosome-like bodies in the basal part of the cytoplasm, suggesting peritubular uptake from the interstitial space. However, small amounts of the tracer were also seen in apical vesicles close to the luminal plasma membrane. The interstitial cells of peroxidase-injected animals were ultrastructurally altered and had large irregular invaginations of the cell membrane. The cells had taken up only small amounts of the tracer which were located in small round lysosome-like bodies. Thus, the interstitial cells displays no macrophage characteristics, either in the native state or when challenged with an extracellular protein.