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Kidneys of 25 dogs were treated with ultrasonic shock waves and examined for both physiologic and pathologic changes. The number of pulses ranged from 2,000 to 8,000. The rate of the shock waves varied from one to 20 pulses per second. The difference in pulse rate did not affect the changes seen either acutely or in the delayed examination of the kidneys during the repair process. The physiologic and pathologic changes which occurred involved the renal tubule to a greater degree than the glomerulus. These alterations were resolving by one week following exposure to the shock waves.

The alterations in single glomerular hemodynamics, glomerular size, and development of glomerular sclerosis after subtotal nephrectomy were assessed in approximately 32-d-old young and greater than 3-mo-old adult Munich-Wistar rats. In 6 wk, young rats developed more pronounced glomerular sclerosis and more marked elevation in blood urea nitrogen. The deep (versus superficial) cortical region of young rats was characterized by having a greater number of glomeruli with advanced sclerosis. Single nephron glomerular filtration rate of superficial glomeruli of the young increased to a much greater extent than whole kidney glomerular filtration rate, whereas there were comparable post-subtotal nephrectomy increases in whole kidney glomerular filtration rate in these two age groups, indicating that the deep glomeruli were exposed to a lesser hemodynamic load than were the superficial. Since the remnant nephrons of young and adult rats achieved equally high glomerular pressures and comparably large glomerular size shortly after subtotal nephrectomy, the unique susceptibility of young glomeruli to sclerosis is attributed to the intrinsic property of these glomeruli, rather than the abnormal hemodynamics or stimuli promoting hypertrophy and mesangial matrix accumulation imposed upon the glomeruli.

Extensive research efforts have been aimed at the study of potential pathogenic processes which participate in the progression of renal disease. The characteristic end stage histological pattern ultimately shared by the various diseases has lead to the postulate of existence of common secondary destructive processes triggered by many different primary pathogenic insults (Figure 1). Initial pathogenic insults are presumed to lead to a loss of functioning nephrons through disease-specific pathophysiologic processes (immunologie or non-immunologic). This loss of nephrons then promotes alterations of function and metabolism in intact glomeruli which are self-damaging in nature, leading to further loss of nephrons. The ultimate outcome of this vicious cycle is the end-stage kidney. In strong support of this view, the so-called animal model of subtotal nephrectomy, or surgical removal of a large number of nephrons from otherwise healthy kidney tissue, indeed causes progressive glomerular sclerosis closely resembling that seen in human end-stage kidneys. Recent intensive investigative effort has therefore focused on identifying the alterations that take place in remnant glomeruli of subtotally nephrectomized animals.

It has been known for centuries that abnormalities in urine may indicate disease. The science of urinalysis has progressed greatly since the days of the medieval “Pisse Prophets” who, by visual examination of the urine, claimed to diagnose disease and see into the future. A carefully performed urinalysis using physical, chemical and microscopic examination offers very important information regarding the kidney. The results of any urinalysis depend on proper collection, preservation and careful examination. Numerous specific tests are also available for specific diagnoses when indicated by the initial routine screening tests (1–6).

Fig 2. Early segmental fibrinoid necrosis with early cellular crescent formation without endocapillary proliferation or evidence of immune complexes in the remaining glomerular tuft. This light microscopic finding is that of a pauci-immune necrotizing glomerulonephritis, with a specific diagnosis of anti-GBM antibody-mediated glomerulonephritis made by immunofluorescence (see Fig 3) (Jones silver stain; original magnification 3400).

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.

y Dis. 1999;33(3):E1 Fig 1. Glomeruli are normal by light microscopy in minimal change disease, as shown in this biopsy. The glomerular basement membrane is thin and delicate, and mesangial cellularity and matrix are within normal limits. There was no interstitial fibrosis and no segmental sclerosis in any of the glomeruli sampled. However, the possibility of unsampled focal segmental glomerulosclerosis (FSGS) cannot be completely excluded when only a small number of glomeruli (less than 250) are examined. (Jones’ silver stain, 3200).

Fig 2. Cryoglobulinemic glomerulonephritis with membranoproliferative and mesangial proliferative features. In this biopsy, strongly PAS-positive small cryoglobulin plugs are present within capillary loops. In the setting of subacute cryoglobulinemic glomerulonephritis, inflammatory cells can be present within the glomerulus, as in this case (periodic acid-Schiff stain; original magnification 3200).

Multiple physiological adaptations must occur in placental mammals at birth when the fetus switches from dependence on a maternal life support system to a free living existence. The renal system, in particular, faces the dual challenges of achieving a rapid some 50-fold increase in urine production to eliminate nitrogenous wastes now entirely through the kidney, and at the same time, of establishing a mechanism by which the high urine production is matched by efficient removal of urine from the kidney. The latter is accomplished by development of the pelvis, an organ unique to mammals, which, under the control of its pacemaker cells, initiates the peristaltic movement to rapidly transfer urine from the kidney to the ureter.

The ontogeny of the renal calyx and ureter involves the resorption of septa between the ureteric buds, and recanalization of the ureter. Both these phenomena take place in concert with the disappearance of undifferentiated mesenchymal cells which densely surround the ureter and ureteric buds. Our recent studies have revealed that upregulation of AT2 transcriptional activity is temporally and spatially associated with the disappearance of these mesenchymal cells. In vitro studies with mouse embryonic fibroblasts also demonstrated a significant role of AT2 in promoting cell apoptosis. We now report that male mice (129 × C57BL/6) carrying a targeted null mutation of the AT2 gene (on the X chromosome) display congenital urinary tract anomalies (CUTA) with a penetrance of 23%. CUTA is predominantly unilateral, and includes hypoplastic kidney, multicystic dysplastic kidney, ureteropelvic junction obstruction, megaureter, vesicoureteral reflux and some combination thereof. This diversity of phenotypes and male preponderance closely mimic human CUTA. Evaluation of the inheritance pattern of CUTA in mice indicates that at least two other modifier genes are also involved. Together with our recent preliminary genetic findings in human populations, these results indicate that 1) embryonic activation of AT2 receptor has a significant developmental role to ensure normal growth of the ureter and the kidney; and 2) the diverse anatomical patterns seen in childhood CUTA share a common mechanism of impaired/delayed apoptosis of mesenchymal cells surrounding the developing ureter. With the AT2 null mutant mouse, it is now possible to identify other genes, besides the AT2 gene, that are involved in CUTA, and to study the etiology of CUTA in utero.

Serial micropuncture analysis of single nephron function in subtotal renal ablation. We developed a series of methodology to analyze function-structure relationship at single nephron level in animal models of chronic renal disease. Micropuncture measurements were repeated to measure single nephron GFR (SNGFR) and glomerular capillary hydraulic pressure (PGC) in the same nephrons, and subsequently examine the morphology of these glomeruli by serial section histological analysis. Using this approach, a potential causal link between early functional pattern and late structural abnormalities was examined in glomeruli of 10 Munich-Wistar rats up to six weeks after surgical removal of 5/6 total renal mass. After two weeks all SNGFR and PGC values increased uniformly but to varying degrees within each remnant kidney. Thereafter, values for SNGFR were highly variable, many declining while others increased in the same kidney. PGC showed an initial increase with subsequent decrease by four to six weeks. Serial section histological analysis of these same glomeruli revealed that the extent of glomerular sclerosis positively correlated with the functional deterioration, that is, the degree of reduction in SNGFR (P < 0.01). However, the degree of sclerosis had no tendency to correlate with the levels of SNGFR or PGC recorded in early stage. These studies indicate that pathophysiologic mechanisms other than, or in addition to, early hyperfunction are involved in determining the extent of glomerular structural damage in this model of chronic renal failure.

The Coulter S-Plus IV separates leukocytes in peripheral blood by volume analysis into granulocytes, lymphocytes, and mononuclear cell fractions, the so-called three-part differential (3PD). White blood cell (WBC) counts, hemoglobin concentrations, platelet counts, 3PDs, and histograms were compared with smear differentials on 3,861 samples, including samples from oncology patients, to determine the predictive value of the Coulter parameters in detecting smear abnormalities. Results showed good correlation between the 3PD and smear differential for granulocytes and lymphocytes (correlation coefficients were 0.883 and 0.868, respectively) and poor correlation for mononuclear cells (0.492). No histogram region flag indicators were observed in the following samples: 15 of 40 samples with greater than or 1% blasts; 105 of 183 with greater than or 1 nucleated red blood cell (NRBC) per 100 WBCs; 65 of 113 with monocytosis greater than 1,600/microL (1.6 X 10(9)/L); 425 of 548 with greater than 2,000 bands/microL (2.0 X 10(9)/L); 84 of 112 with eosinophilia greater than 600/microL (0.6 X 10(9)L); and 88 of 149 with greater than 2% immature granulocytes. All samples with greater than 5% blasts were indicated by region flags and abnormal histograms. Oncology patient data were analyzed, yielding similar results. The authors established guidelines for using the Coulter 3PD data in their tertiary care laboratory to select samples that require smear evaluation.

We report on 2 patients (3 1/2 year-old-male and 6-year-old female) with the ring 15 chromosome syndrome and speech delays and review 25 cases from the literature. The main characteristics of this syndrome include growth retardation (100%), variable mental retardation (95%), microcephaly (88%), hypertelorism (46%), and triangular facies (42%). Other frequent findings include delayed bone age (75%), brachydactyly (44%), speech delay (39%), frontal bossing (36%), anomalous ears (30%), cafe-au-lait spots (30%), cryptorchidism (30%), and cardiac abnormalities (30%). The average age at diagnosis was 8.1 years. The average maternal and paternal age at the time of birth was 28 and 31 years, respectively.

Glomerular hemodynamic changes vs. hypertrophy in experimental glomerular sclerosis. In a variety of recent studies in animals with chronic renal diseases, investigators have found a tight correlation between the elevation in glomerular pressures and flows versus glomerular hypertrophy. To investigate a possible causal link between the glomerular hyperfunction and hypertrophy, we studied the functional and morphological sequelae of nephrectomy and those of unilateral ureteral diversion (UD) into the peritoneal cavity (that is, removal of renal clearance function while keeping the kidney tissue in situ). In all nine experimental groups of 54 Munich-Wistar rats, 2/3 of the renal mass was removed from the left kidney by ligation of two or three branches of the left renal artery. In addition, right nephrectomy (NPX) was performed in Groups 1B, 2B and 3B or UD in Groups 1C, 2C and 3C. The right kidney was left untouched in control groups, Groups 1A, 2A and 3A. Micropuncture measurements and histological studies were performed at four days (Groups 1A, 1B and 1C), two weeks (Groups 2A, 2B and 2C) or four weeks (Groups 3A, 3B and 3C). At both four days and two weeks, NPX and UD groups had marked and comparable degrees ofglomerular hypertension, hyperperfusion and hyperfiltration compared to the control group in the left kidney. Whereas the maximum planar area of glomeruli (PA max ) of the UD group assessed at four days and two weeks by serial section histological analysis remained at a level similar to that of the control group, PA max was significantly increased in the NPX group. At four weeks, similar degrees of glomerular hypertension and hyperfiltration were again demonstrated in the left kidney of NPX and UD groups. However, whereas glomerular sclerosis (0 to 4 scale) assessed at four weeks was subtle in the control group (mean: 0.02) and in the UD group (mean: 0.19), a significantly and markedly higher sclerosis index (mean: 0.56) was noted in the NPX group. The results indicate that 1) physical loss of nephrons, in addition to loss of their excretory function, is required to trigger glomerular hypertrophy and sclerosis. 2) While glomerular hypertrophy appears to be an important step preceding glomerular sclerosis, glomerular hyperfunction alone does little to induce glomerular hypertrophy and sclerosis.

Renal proximal tubular damage and repair are hallmarks of acute kidney injury. Because glycogen synthase kinase-3β (GSK-3β) is an important cellular regulator of survival and proliferation, we determined its role during injury and recovery of proximal tubules in a mercuric chloride-induced nephrotoxic model of acute kidney injury. Renal proximal tubule-specific GSK-3β knockout mice exposed to mercuric chloride had improved survival and renal function compared to wild type mice. Apoptosis, measured by TUNEL staining, Bax activation, and caspase 3 cleavage were all reduced in the knockout mice. The restoration of renal structure, function, and cell proliferation was also accelerated in the GSK-3β knockout mice. This enhanced repair, evidenced by increased Ki-67 and BrdU staining, along with increased cyclin D1 and c-myc levels, was recapitulated by treatment of wild type mice with the small-molecule GSK-3 inhibitor TDZD-8 following injury. This confirmed that hastened repair in the knockout mice was not merely due to lower initial injury levels. Thus, inhibition of GSK-3β prior to nephrotoxic insult protects from renal injury. Such treatment after acute kidney injury may accelerate repair and regeneration.

Microangiopathic injury and augmented PAI-1 in human diabetic nephropathy.BackgroundMicrovascular injury and mesangial dysfunction contribute to the pathogenesis of diabetic glomerulosclerosis. We investigated the extent of microvascular injury characterized by fragmented red blood cells (RBCs) in the mesangium of glomeruli in diabetic nephropathy, and its clinicopathologic significance. We also investigated the possible contributions of plasminogen activator inhibitor-1 (PAI-1), which has been implicated in thrombosis and sclerosis, and the novel steroid receptor superfamily member, peroxisome proliferator-activated receptorγ (PPARγ), implicated in monocyte-foamy macrophage transformation in atherosclerosis and improved insulin responsiveness in diabetes.MethodsSixty-four diabetic nephropathy (DN) cases in our renal biopsy files at VUMC, diagnosed between 1997 and 1999, were reviewed. Patients were classified based on the presence or absence of fragmented RBCs in the mesangium (M+, M-). PAI-1 and PPARγ immunostaining was performed with double staining for the macrophage marker CD68.ResultsM+ lesions were present in 21.9% of cases, and in positive cases, involved on average 10.2 ± 2.1% of glomeruli. M+ patients were 40- to 78-years-old (mean ± SD, 60.4 ± 9.8), the female/male ratio was 2.5, and the white/black ratio was 6. In M-, the patients' ages ranged from 29 to 81 years (57.6 ± 13.3, P = NS vs. M+), the female/male ratio was 0.5 (P < 0.05 vs. M+), and the white/black ratio was 2.3 (P = 0.1 vs. M+). Mean 24-hour urine protein in M+ was 9.9 ± 13.6 g/24 h, versus 4.0 ± 2.8 g/24 h in M- (P < 0.05). The fragmented RBCs in M+ cases localized exclusively within Kimmelstiel-Wilson nodules. PAI-1 and PPARγ immunostaining was increased in areas of sclerosis in arteries and glomeruli, with expression of both in glomerular mesangial, parietal and visceral epithelial cells. Infiltrating macrophages in glomeruli were PPARγ negative, contrasting positivity in macrophages in control cases of carotid artery plaque and in renal interstitial macrophages. The Kimmelstiel-Wilson nodules in M+ patients showed increased PAI-1 staining.ConclusionsMesangial RBC fragments are indicative of microvascular injury and mesangiolysis in DN and are associated with worse proteinuria, and possible worse prognosis. Possible pathogenic mechanisms involve the fibrinolytic/proteolytic system and locally activated PAI-1.

Glomerular hypertrophy in minimal change disease predicts subsequent progression to focal glomerular sclerosis. The study sought a diagnostic clue to identify the group of pediatric patients with apparent minimal change disease who subsequently develop focal glomerular sclerosis (FGS). Review of all renal biopsy material at our institutions identified 42 pediatric patients who met the standard criteria for minimal change disease (MCD) on initial biopsies. Of those, 10 deteriorated clinically and on rebiopsy showed focal glomerular sclerosis (FGS). The initial renal biopsies of these 10 patients were analyzed morphometrically to determine the mean glomerular tuft area (GA). The results were compared to those of the remaining 32 patients whose subsequent benign clinical course was consistent with MCD, and to randomly selected, age-matched autopsy controls without renal disease (CONT, N = 10). The mean age was comparable among the three groups studied. Separate groups of adult (N = 12) and pediatric (N = 18) patients with initial biopsies with FGS were also studied. The initial biopsy of pediatric patients who subsequently showed FGS (rebiopsy performed on average 3.3 years later) had an average GA of 13.5 × 10-3 mm2, 76% larger than glomeruli from children with MCD (7.7 × 10-3 mm2, P < 0.0005) and 62% larger than CONT (8.4 × 10-3 mm2, P < 0.005). Patients with FGS on initial biopsy, whether adult or pediatric, also had significantly larger GA than the age-matched MCD or CONT groups. Evaluation of GA in all the 42 pediatric biopsies with initial MCD further showed that in 23 patients GA was equal to or smaller than the CONT average. Of these, one (4%) was found at the rebiopsy to have FGS. Fifteen patients had GA 1.00 to 1.75× the CONT average; five (33%) of these were found at the rebiopsy to have FGS. Finally, four had GA >1.75× the CONT average at the initial biopsy, all of whom (100%) were found to have FGS at the rebiopsy. The presence of glomerular hypertrophy in biopsies of apparent MCD, therefore, appears to be a highly specific indicator of increased risk for progression to FGS. The data are supportive of the view that the subset of MCD which develops FGS represents a distinctive entity in which pathophysiologic mechanism(s) promoting glomerular hypertrophy are imposed.

Importance of angiogenic action of angiotensin II in the glomerular growth of maturing kidneys. We studied the effect of three antihypertensive drugs on the growth of glomeruli in four- to five-week-old Munich-Wistar rats (N = 24), which were undergoing rapid maturation processes. Young rats were given an angiotensin converting enzyme inhibitor (ACEI, enalapril, 50 mg/liter drinking water), verapamil (50 mg/liter) or hydralazine (80 mg/liter) or no treatment for six weeks. Body weight increased comparably in the treatment groups and age-matched controls, reaching on average 197 ± 11, 214 ± 12 and 198 ± 3 g in ACEI-, verapamil- and hydralazine-treated rats, respectively, versus 218 ± 6 g in control rats. Glomerular hemodynamic patterns, including glomerular capillary pressure, measured in maturing rats after one and six weeks of ACEI treatment were unaffected by ACEI. Mean planar area of glomeruli (PAmean) achieved was smaller than control in ACEI rats (6.60 ± 0.20 × 10-3mm2 vs. 5.37 ± 0.22, respectively, P < 0.005), but not in rats treated with other antihypertensive drugs. Furthermore, the maturational PAmean increase in rats given ACEI for six weeks was, on average, only half of that achieved by age-matched controls not given ACEI, in contrast to normal maturational growth with hydralazine or verapamil (29% increase in PAmean from normal baseline in ACEI vs. 52%, 53% and 59% increases in verapamil, hydralazine and control, respectively). In contrast, comparable PAmean values were found in adults with (7.08 ± 0.22 × 10-3mm2, N = 6) and without (6.98 ± 0.33 × 10-3mm2, N = 6) ACEI treatment given for six weeks. Therefore, ACEI, but not verapamil and hydralazine, causes growth retardation in maturing glomeruli. The studies suggest that the rapid growth of glomeruli in maturing kidneys is dependent upon the angiogenic effect of angiotensin II.

Hypertensive risk factors in kidney disease in African Americans. African Americans with hypertension more commonly develop renal insufficiency compared to Caucasians. The African American Study of Kidney Disease (AASK) included a renal biopsy pilot study that demonstrated that the clinical diagnosis of so-called hypertensive nephrosclerosis in these African American patients indeed was accurate. This biopsy study demonstrated extensive global glomerulosclerosis, far exceeding that expected for patients' age. We further compared our clinically indicated renal biopsies to determine if any phenotypic differences were present in hypertensive nephrosclerosis in African Americans versus Caucasians. These studies point to an excess of the solidified type of global glomerulosclerosis (GS) (also called “decompensated benign nephrosclerosis”) in African Americans compared to more obsolescent type GS in Caucasians. We speculate that these phenotypic differences might reflect differing mechanisms of tissue injury in hypertensive African Americans versus Caucasians, and discuss possible contributors to this injury.

Expression of HIV-1 genes in podocytes alone can lead to the full spectrum of HIV-1-associated nephropathy. Background Human immunodeficiency virus (HIV)-1-associated nephropathy (HIVAN) is characterized by collapsing focal and segmental glomerulosclerosis (FSGS) and microcystic tubular dilatation. HIV-1 infection is also associated with other forms of nephropathy, including mesangial hyperplasia. Since HIV-1 gene products are detected in podocytes and other renal cells, it remains uncertain whether podocyte-restricted HIV-1 gene expression can account for the full spectrum of renal lesions involving nonpodocytes. Methods To define the role of podocyte-restricted HIV-1 gene expression in the progression of HIVAN, we generated transgenic mice that express nonstructural HIV-1 genes selectively in podocytes. Results Four of the seven founder mice developed proteinuria and nephropathy. In a subsequently established transgenic line, reverse transcription-polymerase chain reaction (RT-PCR) analysis detected mRNAs for vif , vpr , nef , and spliced forms of tat and rev , but not vpu , in the kidney. In situ hybridization localized HIV-1 RNA to the podocyte. Transgenic mice on FVB/N genetic background exhibited cuboidal morphology of podocytes with reduced extension of primary and foot processes at 2 weeks of age. After 3 weeks of age, these mice developed massive and nonselective proteinuria with damage of podocytes and other glomerular cells and, after 4 weeks of age, collapsing FSGS and microcystic tubular dilatation. In marked contrast, transgenic mice with C57BL/6 genetic background showed either normal renal histology or only mild mesangial expansion without overt podocyte damage. Conclusion The present study demonstrates that podocyte-restricted expression of HIV-1 gene products is sufficient for the development of collapsing glomerulosclerosis in the setting of susceptible genetic background.

Effects of antihypertensive drugs on glomerular morphology. We quantitated the glomerular size and the degree of sclerosis simultaneously in individual glomeruli with the use of three-dimensional histological analysis on serial sections obtained from remnant kidneys with highly heterogeneous glomerular lesions after subtotal nephrectomy (sNPX). Four to six weeks after sNPX (Group I, N = 7), 90% of glomeruli had mild sclerosis (sclerosis index, SI; < 1.5 on a 0 to 4 scale) with a strong positive correlation between the maximum planar area of glomerulus (PAmax) versus SI. Twelve weeks after sNPX (Group II, N =6) more than 50% of glomeruli had advanced sclerosis (average SI: 1.88), and a significant positive correlation was again found between PAmax and SI in glomeruli with mild to modest sclerosis (SI = 1.5), whereas these two variables were correlated inversely in glomeruli with advanced sclerosis. Administration of enalapril (50 mg/liter drinking water) or hydralazine (200 mg/liter) + reserpine (10 mg/liter) + hydrochlorothiazide (50 mg/liter) for 12 weeks (Group III, TV = 12) markedly attenuated the sclerosis to comparable degrees (average SI: 0.15 vs. 0.22). The former antihypertensive therapy decreased glomerular capillary hydraulic pressure (PGc)t0 normal range, whereas the latter triple drug therapy was largely without efifect on PGC. Of note, the positive correlation between SI and PAmax remained unaffected by these anti-hypertensive drugs. SI of the glomeruli from both treated groups was expressed as a first-order function of PAmax. The correlation coefficient is identical to that found in non-treated Group II remnant glomeruli, so that the degree of sclerosis is mathematically uniquely correlated with the glomerular size, regardless of drug treatment. Thus, within a given remnant kidney, the magnitude of glomerular hypertrophy has a direct correlation with the degree of sclerosis, while the altered glomerular hemodynamic pattern has little modulatory role in determining the magnitude of this hypertrophy. Enalapril and triple drug therapy, at equi-depressor doses in regard to systemic blood pressure, had identical potency in sparing glomerular structure. The primary determinant for this antisclerotic potency appears to be related to the drugs' potency to inhibit glomerular growth rather than an effect on the abnormal hemodynamics which develop in the glomerulus.

This study tests the hypothesis that plasminogen activator inhibitor-1 (PAI-1) contributes to aldosterone-induced renal and cardiac injury. The effects of 12-week aldosterone (2.8 microg/day)/salt (1% drinking water) versus vehicle/salt on renal and cardiac histology and mRNA expression were determined in wild-type (WT) and PAI-1 deficient (PAI-1(-/-)) mice. Systolic blood pressure was similar in aldosterone-infused WT and PAI-1(-/-) mice until 12 weeks, when it was significantly higher in the WT mice. At 12 weeks, urine volume, sodium excretion, and sodium/potassium ratio were similarly increased in the two aldosterone-infused groups. In contrast, urine albumin excretion was greater in aldosterone-infused WT mice (mean+/-s.d.: 699.0+/-873.0 microg/24 h) compared to vehicle-infused WT (23.6+/-9.0 microg/24 h, P=0.003) or aldosterone-infused PAI-1(-/-) mice (131.6+/-110.6 microg/24 h, P=0.007). Aldosterone increased glomerular area to a greater extent in WT (4651+/-577 versus 3278+/-488 microm2/glomerulus in vehicle-infused WT, P0.001) than in PAI-1(-/-) mice (3713+/-705 microm2/glomerulus, P=0.001 versus aldosterone-infused WT), with corresponding mesangial expansion. Renal collagen content was also increased in aldosterone-infused WT versus PAI-1(-/-) mice. In WT mice, aldosterone increased renal mRNA expression of PAI-1, collagen I, collagen III, osteopontin, fibronectin, monocyte chemoattractant protein-1 (MCP-1), and F4/80 (all P0.05), but not transforming growth factor beta (TGF-beta). In PAI-1(-/-) mice, aldosterone increased renal expression of collagen I, osteopontin, fibronectin, and MCP-1, and tended to increase collagen III. Renal osteopontin expression was diminished in aldosterone-treated PAI-1(-/-) compared to aldosterone-treated WT mice (P=0.05). Aldosterone induced cardiac hypertrophy but not fibrosis in WT and PAI-1(-/-) mice. PAI-1 contributes to aldosterone-induced glomerular injury.

We have previously observed increased expression of peroxisome proliferator-activated receptor gamma (PPARgamma) in podocytes in both rat and human sclerotic conditions. The aim of the present study was to investigate whether activation of PPARgamma can attenuate podocyte injury-associated glomerulosclerosis in vivo. Puromycin aminonucleoside nephropathy was induced in Sprague-Dawley rats. The animals then either received no further treatment (control group (CONT)); or the PPARgamma agonist, pioglitazone (Pio) starting at week 0 (P0); or Pio starting at week 6 (P6), with sacrifice at week 12. At week 12, urinary protein excretion and systolic blood pressure were similar in the three groups. Glomerular filtration rate and glomerulosclerosis were decreased in CONT and P0 at week 12, but preserved in P6 rats. PPARgamma expression in CONT at 12 weeks was increased in podocytes and in mesangial WT-1 cells in segmentally sclerotic glomeruli, with less Wilms' tumor 1 (WT-1) staining. In P6 rats, mesangial WT-1 staining was lessened, but podocyte staining was strongly accentuated. Delayed treatment with Pio partially restored podocyte staining and tended to decrease the ratio of proliferating cell nuclear antigen-positive to apoptotic cells in glomeruli. Both treatment groups showed significantly reduced infiltrating glomerular macrophages and plasminogen activator inhibitor-1 mRNA expression in cortex, with no change in transforming growth factor-beta1 and tissue inhibitor of metalloproteinase-1 mRNA. Pio also decreased renal cortical angiopoietin-like protein 4 expression to almost 20% of CONT group, associated with increased vascular endothelial-derived growth factor expression in glomeruli. We conclude that treatment with PPARgamma agonist has protective effects on progression of glomerulosclerosis.

A clinically important characteristic of chronic renal disease, regardless of the underlying cause, is its frequently relentless progression to end-stage renal failure. Functional deterioration is often inevitable even after the initial pathological mechanism has apparently subsided. The possibility has therefore been raised for some time that, after a certain degree of renal damage by the initial disease processes, a common pathway leads to the final progressive functional and structural deterioration. Intensive clinical and experimental animal studies, both in vivo and in vitro, carried out during the last decade have identified several potentially important pathophysiologic mechanisms contributing to this progressive destruction of renal architecture. In this article we will review these recent findings and outline the current directions of research in this field.

Effect of heparin on the glomerular structure and function of remnant nephrons. The development of glomerular structural abnormalities in remnant nephrons, after ablation of renal mass (subtotal nephrectomy), in rats is largely prevented by the daily injection of heparin. To investigate if this protective effect of heparin is due to attenuation of glomerular hyperperfusion, hypertension and hyperfiltration, which develop in remnant nephrons soon after subtotal nephrectomy, we measured various parameters of glomerular hemodynamics at two weeks (Group 1) and four weeks (Group 2) after removal of 1-3/4 of total kidney mass in heparin-treated (Groups 1A and 2A) and untreated (Groups IB and 2B) Munich-Wistar rats. When compared to normal non-nephrectomized rats (Group 1C), the values for glomerular capillary hydraulic pressure(PGC), glomerular plasma flow fate (QA) and single nephron filtration rate (SNGFR) in remnant nephrons were found to be markedly and similarly elevated in both Groups 1A and 1B, averaging 71 ± 4 and 73 ± 4mm Hg, 229 ± 41 and 176 ± 13 nl/min, 58.9 ± 6.4 and 60.8 ± 7.8 nl/min, respectively. Thus, glomerular hemodynamic parameters two weeks after subtotal nephrectomy did not differ between untreated and heparin-treated rats. Likewise, heparin treatment did not decrease the values of PGC and SNGFR assessed four weeks after subtotal nephrectomy, with the average values being 65 ± 2mm Hg and 83.8 ± 7.1 nl/min in Group 2A versus 62 ± 4mm Hg and 63.7 ± 6.5 nl/min in Group 2B. Thin-section light microscopic studies revealed that most of the remnant glomeruli of heparin-treated rats remained structurally intact throughout the entire study period of 7.5 weeks. In non-treàted rats progressive destruction of glomerular architecture developed and normal glomeruli comprised 23 ± 7% of the total remaining nephron population at 7.5 weeks after subtotal nephrectomy. Therefore, the effect of heparin in protecting glomeruli of remnant nephrons from structural damage is mediated by a mechanism independent of glomerular hyperperfusion, hypertension or hyperfiltration occurring in these nephrons. The importance of an anticoagulant and/or antiproliferative effect of heparin is suggested as playing a role in the protection of glomerular structure.

In view of its role as a pro-inflammatory mediator in glomerular injury, we investigated the renal cortical microcirculatory responses to the intrarenal arterial administration of platelet-activating factor (PAF) in the anesthetized euvolemic Munich-Wistar rat. Close arterial administration of PAF led to dose-dependent reductions in renal plasma flow rate (RPF), glomerular filtration rate (GFR), and filtration fraction (FF), in the absence of hypotension or hemoconcentration. Single-nephron (SN) plasma flow rate (QA), SNGFR and SNFF also fell [126 +/- 7 to 101 +/- 6 nl/min (P less than 0.005), 40.6 +/- 2.1 to 21.5 +/- 2.5 nl/min (P less than 0.005), and 0.33 +/- 0.03 to 0.21 +/- 0.03 (P less than 0.025)]. PAF increased pre- and postglomerular arteriolar resistances [2.32 +/- 0.14 to 2.73 +/- 0.19 (P less than 0.005) and 1.32 +/- 0.13 to 1.45 +/- 0.10(10)dyn.s.cm-5 (P less than 0.05)]. PAF infusion also led to a dramatic reduction in the mean value for the glomerular capillary ultrafiltration coefficient, Kf [0.058 +/- 0.012 to 0.020 +/- 0.003 nl.s-1.mmHg (P less than 0.025)]. PAF-induced changes in renal hemodynamics were abolished in the presence of the cyclooxygenase inhibitors, indomethacin and ibuprofen. When administered concomitantly with a thromboxane A2 (TxA2) receptor antagonist, PAF led to significant increases in RPF and GFR. In isolated glomeruli, PAF stimulated the biosynthesis of TxB2 in a dose-dependent manner. Thus PAF depresses rat glomerular function by inducing contraction of arteriolar and mesangial smooth muscle. These effects are likely mediated via the secondary release of TxA2.

Single nephron filtration rate of albumin (SNGFRAlb) was measured in remnant nephrons of Munich-Wistar rats 4-6 wk after subtotal nephrectomy (NPX). Serial thin-section histological analysis was then conducted on the same glomeruli by light microscopy. SNGFRAlb ranged from 1 to 15 times normal. However, a direct relationship between abnormalities of structure and function was not seen, e.g. the glomeruli with the fewest structural abnormalities and marked hyperfiltration often had the highest SNGFRAlb. Moreover, the majority of glomeruli had minimal structural abnormalities. Normalization of the markedly elevated glomerular capillary pressure (PGC) in these glomeruli was accomplished by acute intravenous infusion of verapamil, which decreased SNGFRAlb by 9-83% without affecting the single nephron filtration rate of water (SNGFRH2O). 1-2 wk after subtotal NPX, all glomeruli were hyperfiltering and had elevated PGC. The fractional clearance of larger (greater than 36 A) dextrans was selectively increased in these glomeruli that lacked discernible damage by light microscopy. Verapamil normalized PGC, reduced proteinuria to 48 +/- 4% of baseline, and improved glomerular size selectivity without altering SNGFRH2O. Proteinuria after subtotal NPX thus originates largely from glomeruli with minimal structural abnormalities. The defect in size selectivity is largely attributed to the prevailing high PGC, producing large, nonselective channels on the glomerular capillary wall. The observations raise the possibility that in chronic renal diseases, the reduction in proteinuria often seen after therapeutic measures, including antihypertensive medication, may reflect their functional effect on the relatively intact glomeruli rather than their structure-sparing effect on severely damaged glomeruli, which contribute little to the proteinuria.

Thirty-one patients with chronic primary pure red cell aplasia (PRCA) had blood and marrow cell karyotypes performed prior to immunosuppressive treatment. Only one patient had an abnormal marrow cell karyotype, which revealed a clone of hyperdiploid cells with 47 chromosomes (47, XY, + G). His blood cell karyotype was normal. This patient had no erythroid response to prednisone and cyclophosphamide, or splenectomy, and after 3 yr he developed acute myelomonocytic leukemia with the emergence of a new clone of hyperdiploid cells with multiple ring chromosomes (46,XY/47,XY, + G/49,XY,–G,+4r) in the blood and marrow. These studies indicate that chronic primary PRCA probably has a much lower incidence of abnormal karyotypes and acute leukemia than other refractory anemias (myelodysplastic syndromes), but that an abnormal marrow karyotype may portend a leukemia. The role of cytotoxic immunosuppressive drugs in the treatment of PRCA patients with an abnormal karyotype remains unknown.

In Munich-Wistar rats, a micropipette was inserted into a first-order branch of the left main renal artery and continuously infused with human/porcine endothelin (0.4 ng/min). Micropuncture measurements revealed substantial differences within the cortical microcirculation of the same left kidney: SNGFR was some 35% lower in glomeruli exposed to endothelin compared with non-endothelin-perfused glomeruli (P less than 0.005). Similarly, glomerular plasma flow rate was some 38% lower in the endothelin-exposed glomeruli (P less than 0.001). The hypoperfusion and hypofiltration in the endothelin-exposed glomeruli reflected an increase in resistances in the afferent and efferent arterioles. There was no difference in the value of the glomerular capillary ultrafiltration coefficient between the two populations of glomeruli. We also studied kidneys that underwent 25 min of renal artery clamping 48 h before study. Antiendothelin antibody infused into one of the branches of the main renal artery ameliorated the vasoconstriction characteristic of postischemic nephrons: within the cortical microcirculation, the SNGFR in glomeruli exposed to antiendothelin antibody was 27.0 +/- 3.1 nl/min as compared with 17.4 +/- 1.7 measured in glomeruli not perfused with the antibody (P less than 0.001). Similarly, glomerular plasma flow rate was higher in the glomeruli exposed to antiendothelin antibody (128.7 +/- 14.4 nl/min vs. 66.6 +/- 5.6, P less than 0.005). Resistances in both the afferent and efferent arterioles were substantially lower in the antibody-exposed glomeruli. It is, therefore, suggested that endothelin, presumably released from damaged endothelium, may play an important intermediary role in the hypoperfusion and hypofiltration observed in postischemic kidneys.

Modulation of plasminogen activator inhibitor-1 in vivo: A new mechanism for the anti-fibrotic effect of renin-angiotensin inhibition. We examined the potential of in vivo linkage of plasminogen activator inhibitor-1 (PAI-1) and angiotensin II (Ang II) in the setting of endothelial injury and sclerosis following radiation injury in the rat. PAI-1 is a major physiological inhibitor of the plasminogen activator (PA)/plasmin system, a key regulator of fibrinolysis and extracellular matrix (ECM) turnover. PAI-1 mRNA expression in the kidney was markedly increased (9-fold) at 12 weeks after irradiation (P < 0.001 vs. normal control). In situ hybridization revealed significant association of PAI-1 expression with sites of glomerular injury (signal intensity in injured vs. intact glomeruli, P < 0.001). Angiotensin converting enzyme inhibitors (ACEI, captopril or enalapril) or angiotensin II receptor antagonist (AURA, L158,809) markedly reduced glomerular lesions (thrombosis, mesangiolysis, and sclerosis; sclerosis index, 0 to 4+ scale, 0.49 ± 0.20 in untreated vs. 0.05 ± 0.02, 0.02 ± 0.01, 0.04 ± 0.02 in captopril, enalapril and AURA, respectively, all P < 0.01 vs. untreated). Further, ACEI and AURA markedly attenuated increased PAI-1 mRNA expression in the irradiated kidney (36, 19 and 20% expression, respectively, for captopril, enalapril and AURA, compared to untreated irradiated kidney, P < 0.05, < 0.01, < 0.01). This effect was selective in that neither tissue-type nor urokinase-type PA mRNA expression was affected by these interventions. Thus, we speculate that inhibition of the renin-angiotensin system may ameliorate injury following radiation by accelerating fibrinolysis and ECM degradation, at least in part, via suppression of PAI-1 expression. In summary, inhibition of Ang II, in addition to its known effects on vascular sclerosis, may also by its novel effect to inhibit PAI-1, lessen fibrosis following endothelial/thrombotic injury.

Item does not contain fulltext In rodents, parietal epithelial cells (PECs) migrating onto the glomerular tuft participate in the formation of focal segmental glomerulosclerosis (FSGS) lesions. We investigated whether immunohistologic detection of PEC markers in the initial biopsies of human patients with first manifestation of idiopathic nephrotic syndrome with no immune complexes can improve the sensitivity to detect sclerotic lesions compared with standard methods. Ninety-five renal biopsies were stained for claudin-1 (PEC marker), CD44 (activated PECs), and LKIV69 (PEC matrix); 38 had been diagnosed as early primary FSGS and 57 as minimal change disease. PEC markers were detected on the tuft in 87% of the biopsies of patients diagnosed as primary FSGS. PEC markers were detected in FSGS lesions from the earliest stages of disease. In minimal change disease, no PEC activation was observed by immunohistology. However, in 25% of biopsies originally diagnosed as minimal change disease the presence of small lesions indicative of a sclerosing process were detected, which were undetectable on standard periodic acid-Schiff staining, even though only a single histologic section for each PEC marker was evaluated. Staining for LKIV69 detected lesions with the highest sensitivity. Two novel PEC markers A-kinase anchor protein 12 and annexin A3 exhibited similar sensitivity. In summary, detection of PECs on the glomerular tuft by immunostaining improves the differentiation between minimal change disease and primary FSGS and may serve to guide clinical decision making.

To the Editor: Whereas the NC1 domain of α3(IV) collagen is the major target of Goodpasture autoAbs in anti-GBM glomerulonephritis, DBA/1 mice immunized with α3NC1 develop massive albuminuria progressing to nephrotic syndrome. Kidney histopathology shows fine granular GBM deposition of IgG and C3, GBM thickening with “spike” reaction, subepithelial electrondense deposits, podocyte foot process effacement, but minimal glomerular inflammation1-3. These clinical and morphologic findings recapitulate human membranous nephropathy rather than anti-GBM glomerulonephritis. This unexpected phenotype may be due to a subepithelial planted antigen, consistent with the fine granular deposition of exogenous antigen in the capillary loops3. An elegant recent study comprehensively characterized tubulointerstitial infiltrates of macrophages and CD4(+) Th1 and Th17 cells in the late stages of α3NC1-induced nephropathy1. This may reflect a true autoimmune response against α3(IV) collagen occurring in all mouse (but not human) tubular basement membranes. Alternatively, mononuclear interstitial infiltrates may be secondary to nephrotic-range proteinuria. Of note, the predominant inflammatory cells in human membranous nephropathy are interstitial monocyte/macrophages and CD4(+) T cells4. Moreover, their numbers correlate with renal impairment at the time of the biopsy and progressive renal impairment over 5 years, suggesting that progression toward renal failure in membranous nephropathy may be driven mainly by cell-mediated immunity4. Future studies expanding on the findings of Hopfer et al are needed to determine whether interstitial mononuclear infiltrates are indeed harbingers of renal failure in membranous nephropathy.