Mesangial involvement in hemolytic-uremic syndrome. A light and electron microscopic study

Electron microscopic analysis of the mesangial injury in the hemolytic-uremic syndrome was performed in 10 patients. Proteinaceous material similar to that found in the subendothelial region was also seen focally in the mesangium altering the matrix and imparting a reticular appearance. This degenerative process was associated with reparative changes in the glomerular tuft. Many of the mesangial cells were hypertrophied and demonstrated phagocytic activity and peripheral extension of their cytoplasmic processes. Mitotic figures in endothelial as well as mesangial cells were regarded as evidence of a reparative process. Severe mesangial insudation of material containing fibrinogen derivatives resulted in segmental tuft necrosis with almost complete replacement and destruction of the mesangial matrix. On some occasions, a break of the glomerular basement membrane was accompanied by the escape of intraluminal contents into the urinary space, leading to crescentic epithelial cell proliferation.     

Morphology of poststreptococcal glomerulonephritis in adults

The authors followed the evolution of morphologic changes in adult patients with poststreptococcal glomerulonephritis (PSGN). In all the patients the kidney biopsies repeated in the period of 2 to 5 years after the acute phase, showed certain histopathologic changes as follows: increased number of mesangial cells, increase of mesangial matrix with scattered axiation and lobulation, segmental thickening of Bowman's capsule, interstitial fibrosis along with preservation of capillary lumen and absence of changes in major blood vessels. According to severity of histopathologic changes, the patients were classified into 4 groups: moderate severe changes--2 patients, mild--15 patients, small--12 and minimal changes were seen in 5 patients. It was proved that after acute stage of PSGN, in which morphologic appearance was more or less typical but not pathognomonic as well, increased number of secretory active mesangial cells was kept, which lead to gradual increasing of mesangial matrix and in slowly evolutive process by the model of glomerulosclerosis lead to irreversible damage of glomerules and interstitial fibrosis.     

Renal disease in an adult patient with type I glycogen storage disease

A 26-year-old Chinese male patient with type I glycogen storage disease presented with chronic renal disease, proteinuria, and urolithiasis. On renal biopsy, focal glomerular sclerosis, increased mesangial matrix and cellularity, interstitial fibrosis, tubular atrophy, and prominent arteriosclerosis were observed. Immunofluorescence microscopy revealed Ig A deposits predominantly in the glomerular mesangium. The possible mechanisms of renal involvement in glycogen storage disease are briefly discussed.     

From segmental glomerulosclerosis to total nephron degeneration and interstitial fibrosis: a histopathological study in rat models and human glomerulopathies

BACKGROUND: Focal segmental glomerulosclerosis (FSGS) is consistently associated with tubular degeneration and interstitial fibrosis, altogether, accounting for the progressive decline in renal function. The mechanisms which link glomerular injury to tubulo-interstitial fibrosis are controversial. The present study describes the step-by-step sequence of histopathological events, i.e. the evolution of the injury from the initial lesion in the glomerulus to total nephron destruction. METHODS: The investigation was performed in male hypertensive Fawn-hooded rats (6-, 9-, and 12-month-old) and 14-month-old Milan normotensive rats. The kidneys were fixed by in vivo perfusion and processed for structural investigation. Autopsy materials from human cases of focal segmental glomerulosclerosis and diabetic nephropathy were also examined. RESULTS: FSGS as seen in rat models consists of collapsed and hyalinized capillaries and mesangial portions which are included within a synechia between the glomerular tuft and Bowman's capsule. In addition, a synechia generally contains glomerular capillaries which are perfused and continue to filter with the filtrate being delivered into the interstitium rather than into Bowman's capsular space. Such filtration creates a paraglomerular space on the outer aspect of the parietal epithelium. This space becomes separated from the interstitium by a dense layer of sheet-like fibroblast processes. Associated with the progression to global sclerosis, this space spreads around the entire circumference of a glomerulus; all 'sclerotic' tuft portions are eventually contained in this space. Starting from the urinary pole this process also involves the proximal tubule, initially by expanding the tubular basement membrane (TBM) and later, by separating the TBM from its epithelium, thus creating a peritubular space by misdirected filtrate spreading. Similar to the situation observed at the glomerulus this space becomes separated from the interstitium by a layer of fibroblast processes. The final degeneration of the nephron occurs via two pathways. Pathway I whereby development to global sclerosis is dominant or develops concurrently with tubular degeneration, eventually terminating in global and cylindrical remnants of extracellular matrix surrounded by abundant fibrous tissue. Pathway II where the degeneration of the tubule is ahead of damage progression in the glomerulus leading to atubular glomerular cysts. CONCLUSION: The present study suggests that severely injured glomeruli may continue to filter with the filtrate spreading along interstitial routes. Fluid added locally to the interstitium from such 'extraterritorial' glomerular capillaries probably is quite different in quantity and composition compared to that from interstitial capillaries. We propose that this kind of abnormal addition of fluid to the interstitium is the essential mechanism accounting for interstitial progression of the disease. Similar histopathological phenomena in human kidneys with focal segmental glomerulosclerosis suggest that the pathogenetic pathways defined in the rat models operate in human disease as well.     

Contractile cells of the kidney in primary glomerular disorders: an immunohistochemical study using an anti-alpha-smooth muscle actin monoclonal antibody

Mesangial cells of the renal glomerulus are thought to have contractile properties, resembling those of smooth muscle cells. Since actin synthesis in mesangial cells is increased in selected animal models of glomerulonephritis, we evaluated the expression of alpha-smooth muscle actin (ASMA), the principal actin isoform found in smooth muscle cells, in biopsy specimens from patients with primary glomerular disorders and in control tissues. Normal glomeruli and glomeruli in acute tubulointerstitial disorders showed few or no ASMA-positive cells in the glomeruli. In contrast, ASMA expression in mesangial cells was increased in minimal change disease, focal segmental glomerulosclerosis, mesangial proliferative glomerulonephritis, membranous glomerulonephritis, and immunoglobulin A nephropathy. In membranoproliferative glomerulonephritis and cryoglobulinemic glomerulonephritis both mesangial and capillary loop ASMA-positive cells were observed with a segmental distribution. In addition, ASMA-positive interstitial cells were seen in many biopsy specimens and often were increased in number in biopsy specimens showing early interstitial fibrosis and tubular atrophy. We conclude that ASMA synthesis in mesangial cells is upregulated in a variety of glomerular disorders, frequently associated with increased cell proliferation and mesangial matrix production. This phenotypic change may be an indicator of mesangial cell activation after injury and may have important pathophysiologic consequences.     

Expression of types I, II, and III TGF-beta receptors in human glomerulonephritis

Protein and mRNA expression of transforming growth factor-beta (TGF-beta) receptor type I (TbetaRI), type II (TbetaRII), and type III (TbetaRIII) were studied in serial sections of kidney samples obtained from patients with glomerulonephritis. In minimal change disease, weak expression of TbetaRI and TbetaRII was observed mainly in glomerular endothelial cells, peritubular capillaries, and interstitial arteriolar endothelial cells, whereas TbetaRIII expression was found mainly in the interstitium. Expression of all three TGF-beta receptors (TbetaR) was increased remarkably in glomerular and Bowman's capsular cells comprising the tuft adhesions to Bowman's capsules in glomerulonephritis with increased matrix accumulation, including IgA nephropathy, lupus nephritis, focal and segmental glomerulosclerosis, myeloperoxidase-antineutrophil cytoplasmic antibody-associated crescentic glomerulonephritis, and membranoproliferative glomerulonephritis. Increased expression of the three TbetaR was also seen in glomerular epithelial cells in the vicinity of glomerulosclerotic lesions, in crescent cells, and in some tubules and infiltrative mononuclear cells found in the periglomerular and tubulointerstitial lesions with increased matrix deposition. In contrast, no remarkable TbetaRII expression was noted in mesangial proliferative lesions in IgA nephropathy, lupus nephritis, and membranoproliferative glomerulonephritis. These data suggest that distinctive modulation of TbetaR expression may be involved in the development of adhesive, sclerotic, and proliferative renal lesions in human glomerulonephritis.     

Statistical methods for dependent competing risks

In this study, the kinetics of glomerular endothelial cells during the repair process following glomerular injury was investigated in a model of mesangial proliferative glomerulonephritis induced by Habu-snake venom (HSV) in rats. Intravenous injection of HSV led to a cystic ballooning type lesion at day 1. Subsequently a marked segmental proliferative lesion was observed in the cystic areas at day 5. Thereafter cellularity decreased and reconstruction of the glomerular tuft was gradually observed with time. The histological structure of the glomeruli had almost returned to normal 21 days following HSV injection. After prominent depletion at day 1, the number of endothelial cells increased rapidly and reached a plateau at day 7, not significantly different from that of the control group. Morphologically endothelial cell elongation from the vascular pole into the cystic lesion was seen together with premature capillary formation in the proliferative lesion. Accompanying the reduction of mesangial expansion, the endothelial cells gradually formed definite capillary lumens. We conclude that the mesangial proliferative glomerulonephritis induced by HSV recovers to its original structural state and that the migration and proliferation of endothelial cells with accompanying capillary formation are essential for the repair process, in addition to mesangial cell proliferation.     

Glomerular lesions in multiple myeloma

An autopsy case of multiple myeloma (IgG, lambda type), clinically characterized by decreased glomerular filtration rate, is reported with particular emphasis on changes in the glomeruli of kidneys. Histologically, the glomeruli revealed slight increase in mesangial matrix and focal thickening of tuft capillary wall. Electron-microscopically, deposits were observed in a subendothelial location in the glomerular capillary walls, and inclusions were noted in the cytoplasm of the visceral epithelial cells. Histoimmunofluorescent study of the kidney demonstrated intense focal and slight diffuse positivity against labelled antisera of anti-IgG and anti-lambda type of light chain on the capillary wall of the glomerular tufts. Other immunoglobulins were not demonstrable in capillary walls. These findings represent the intraglomerular deposition of paraprotein of multiple myeloma without amyloidosis.     

Analysis of the expression of two thiolprotease genes from daylily (Hemerocallis spp.) during flower senescence

Rats treated with two injections of adriamycin (week 0 and week 12) developed glomerusclerosis and severe tubulointerstitial lesions as described in the literature. In addition, a number of glomerular alterations were present. These included capillary loop dilation, insudation of eosinophilic material, necrosis, duplication of the glomerular basement membrane, severe mesangiolysis with disruption of the mesangial matrix and segmental double-contours. The renal arterioles and interlobular arteries showed endothelial cell swelling. The subendothelial space was infiltrated by fibrinoid material and there was intensive fibrinoid necrosis of the wall of both arteries and arterioles extending into the glomerular tuft. These alterations were very similar to those observed in the hemolytic uremic syndrome. This observation suggests that the two injections of adriamycin, with a long interval in between them, might induce renal lesions similar to those observed in the hemolytic uremic syndrome.     

Glomerular tip lesions--a newly described glomerular change

Glomerular tip lesion is a newly described histopathological lesion characterized by a focal and segmental widening of the mesangial matrix without hypercellularity together with capillary dilatation, hyaline exudation on the inside of capillary walls and occurrence of vacuolized cells, localized to the peripheral segments of the glomerular tuft. Clinically, these patients have a pronounced nephrotic syndrome with slightly reduced renal function, but terminal renal failure is seldom seen, even after many years of disorder. Two characteristic case histories are presented. The classification of this lesion among the glomerular disorders is at present uncertain. It may represent a transitional form between minor lesion nephritis and focal segmental sclerosis, a separate disorder, or a functional lesion associated with high proteinuria.     

Purification and characterization of pyruvate oxidoreductase from the photosynthetic bacterium Rhodobacter capsulatus

The effects of the addition of a calcium channel blocker, verapamil (20 mg/kg/day) to an ACE inhibitor, trandolapril (0.7 mg/kg/day) in a 6-month treatment on renal insufficiency development in rats with 5/6th nephrectomy, were studied. Every month we measured heart rate and arterial pressure by the tail-cuff method. Renal function studies were performed in metabolic cages. At the end of the study, renal tissue was prepared for light microscope analysis. Renal lesions were assessed by semiquantitative scores in a blind fashion. Corpuscular section area, intraglomerular and tubulointerstitial fibrosis were determined by digital image analysis with a specific software (Fibrosis HR) on syrium red-stained renal sections. Trandolapril markedly increased the survival ratio that after 6 months reached 87% in comparison with 61% in untreated rats. No mortality was observed in rats treated with the combination of verapamil and trandolapril. Trandolapril treatment prevented the development of hypertension. The combination verapamil-trandolapril did not induce further reduction on blood pressure. The untreated group showed a marked proteinuria, that in the trandolapril group showed an important reduction. The verapamil + trandolapril group showed a proteinuria significantly smaller than that of all the other groups. Light microscopy semiquantitative studies of the renal injury showed that the trandolapril and verapamil + trandolapril groups had a marked reduction in glomerular and tubulointerstitial alterations, compared with untreated animals. Quantitative determinations of glomerular and interstitial fibrosis performed on syrium red-stained renal sections demonstrated that fibrosis was reduced when rats when treated with trandolapril and even more with verapamil + trandolapril when they were compared to untreated animals' values. In conclusion, long-term treatment with verapamil given in addition to trandolapril produces additional protection against progressive renal injury associated to subtotal nephrectomy.     

Renal glomerular fibrosis in a cat

Renal glomerular fibrosis was observed in a 1-year-old spayed female Japanese domestic cat that showed clinically advanced renal failure. In the glomeruli, increased homogeneous materials were stained strongly with aniline blue by Masson's trichrome and positive for anti-type III collagen antibody by immunohistochemical staining, causing mesangial sclerosis and capillary collapse. By electron microscopy, randomly arranged fibrils were observed in the expanded subendothelial and mesangial areas, and the fibrils showed periodicity characteristic of collagen fibers in longitudinal sections. These findings of glomerular lesions closely resemble those of human "collagenofibrotic glomerulonephropathy," which has recently been described as a new type of glomerulonephropathy.     

Mental health in action

Twenty-nine patients with insulin-dependent diabetes mellitus with similarly manifest renal involvement were examined to elucidate the role of dyslipidemia in diabetic nephropathy progress. Clinico-laboratory parameters (urinary albumin excretion, blood serum levels of total cholesterol, triglycerides, low, very low, and high density lipoprotein cholesterol) and morphologic changes in renal tissue biopsy specimens were analyzed. An increment of the number of large lipid incorporations was observed in various cells of renal glomeruli and interstitium, as well as a high prevalence of low density lipoprotein deposition in glomerular basal membranes and canaliculi as the renal process augmented in severity. Since lipids accumulating in glomerular structures may stimulate mesangial cell proliferation and mesangial matrix hyperproduction, the authors believe that dyslipidemia in diabetes mellitus may be conducive to a more rapid progress of renal disease.     

An immunological correlation between the anchoring filaments of initial lymph vessels and the neighboring elastic fibers: a unified morphofunctional concept

More than 25 years have passed since immunoglobulin A (IgA) nephropathy was introduced as a disease entity independent of glomerulonephritis. It has been known that more than 30% of cases have gone into end-stage renal failure within 20 years, indicating the presence of a chronic active group in this disease. Histologically this disesase is composed of at least three types of tissue damage: (i) minimal inflammation including deposition of IgA-containing substances with minor matricial increase; (ii) acute lesions characterized by matricial damage of glomerular basement membrane (membranolysis) and/or mesangial matrix (mesangiolysis) with inflammatory cell accumulation and/or intrinsic cell proliferation; and (iii) chronic lesions mainly composed of postinflammatory sclerosis. The progression is actually accelerated by the frequency of acute lesions, resulting in increased glomerular sclerosis foci. In such a situation, the histologic grading and staging (G-S) system is proposed, with the aim of having a more precise understanding of the disease process. The histological grade (G) is estimated by the extent of acute glomerular and tubulointerstitial lesions, and the stage (S) is evaluated by the increase of extracellular matrices of the glomeruli and interstitial fibrosis. The evaluation of G and S is expressed semiquantitatively for more helpful clinical use.     

Paracrine PDGF-B/PDGF-Rbeta signaling controls mesangial cell development in kidney glomeruli

Kidney glomerulus mesangial cells fail to develop in mice carrying targeted null mutations in the platelet-derived growth factor (PDGF)-B or PDGF-Rbeta genes. We have examined the pattern of expression of these genes and smooth muscle markers during kidney development, to address the possible mechanisms underlying the mutant phenotypes. In wild-type embryos, PDGF-B was expressed in vascular endothelial cells, particularly in capillary endothelial cells in the developing glomeruli, whereas PDGF-Rbeta was found in perivascular mesenchymal cells in the developing renal cortex. In the course of glomerular development, small groups of PDGF-Rbeta and desmin-expressing cells collected in the 'S'-shaped and early cup-shaped vesicles, and at later stages such cells were found in the glomerular mesangium. In PDGF-B or -Rbeta null embryos, some PDGF-Rbeta/desmin or desmin-positive cells, respectively, were seen in early cup-shaped vesicles, but fewer than in the wild type, and further development of the mesangium failed. In mouse chimeras composed of PDGF-Rbeta +/+ and -/- cells, the Rbeta-/- cells failed to populate the glomerular mesangium. Our results show that while the mesangial cell lineage is specified independently of PDGF-B/Rbeta, these molecules provide critical permissive signals in mesangial cell development. We propose a model in which mesangial cells originate from PDGF-Rbeta-positive progenitors surrounding the developing glomerular afferent and efferent arterioles, and are co-recruited in response to PDGF-B during angiogenic formation of the glomerular capillary tuft.     

Role of growth factors in mesangial cell ion channel regulation

Our single channel work has characterized two ion channels capable of depolarizing mesangial cells and activating classic, voltage-activated Ca2+ channels in response to growth-stimulatory peptides (such as Ang II, ET and insulin): (1) Ca(2+)-dependent, 4 pS Cl- channel promoting Cl- efflux; and (2) Ca(2+)-dependent, 27 pS nonselective cation channels promoting cation influx. We have also characterized a third channel which provides an alternative, receptor-operated pathway for Ca2+ entry in response to the growth factor, PDGF: (3) Ca(2+)-permeable, 1 pS cation channel. Consistent with our model of mesangial cell signal transduction (Fig. 1), these three mesangial cell ion channels are activated by binding of growth factors to membrane receptors (Fig. 8). Defective channel regulation, such as occurs in early diabetes mellitus, would promote mesangial cell relaxation and pathogenic glomerular hyperfiltration. Glomerular hyperfiltration and hypertension have been proposed to be major pathogenic factors in renal disease progression [4, 29, 38, 39]. Compensatory renal growth factor responses initially provide adaptive changes in glomerular hemodynamics after loss of functional renal mass. However, chronic stimulation of these mesangial cell ion channels by renal growth factors would promote sustained extracellular Ca2+ entry, resulting in mesangial cell contraction and growth, and progressive decreases in Kf and GFR. Eventually, this process leads to irreversible renal damage due to the development of glomerulosclerosis and interstitial fibrosis.     

Idiopathic membranous glomerulonephritis associated with diabetes mellitus: light, immunofluorescence and electron microscopic study

The present study described 3 patients with idiopathic membranous glomerulonephritis associated with diabetes mellitus. Clinical characteristics of the 3 patients contrasted with diabetic glomerulosclerosis in the following manner: absence of diabetic retinopathy and neuropathy, and presence of nephrotic syndrome associated with relatively short duration of diabetes mellitus. Renal histology showed the characteristic changes of membranous glomerulonephritis along with those of diabetic glomerulosclerosis. Immunofluorescent studies demonstrated a granular pattern of IgG and C3 deposits along the glomerular capillary wall. Electron microscopic study also demonstrated thickening of glomerular basement membrane and increase of mesangial matrix as well as the presence of electron-dense deposits primarily in the subepithelial and mesangial areas.     

Isolation of myosin heavy chain from small skeletal muscle samples by preparative continuous elution gel electrophoresis: application to measurement of synthesis rate in human and animal tissue

We studied seven patients aged 14 to 40 years who received living-related kidney transplants and had allograft survivals of 26 to 29 years. The blood urea and creatinine were either within normal limits or marginally elevated. Histopathologic examination showed only mild mesangial expansion, interstitial fibrosis, and arteriosclerosis. Immunoperoxidase staining with anti-HLA antibodies or in situ hybridization with a Y chromosome probe showed persistence of donor tubular epithelium and vascular endothelium within the graft. Recipient-derived glomerular cells were seen in one case, and interstitial lymphocytic infiltrates were seen in all cases. A review of the clinicopathologic data available for these cases indicated that both central and peripheral immunologic mechanisms contributed to the maintenance of prolonged graft survival. This extended survival was independent of six antigen matching, down-regulation of donor HLA antigen expression, and ingrowth of host epithelium/endothelium into the allograft.     

Vascular adventitial cell expression of collagen I messenger ribonucleic acid in anti-glomerular basement membrane antibody-induced crescentic nephritis in the rabbit. A cellular source for interstitial collagen synthesis in inflammatory renal disease

BACKGROUND: Scarring in the interstitial compartment of the renal cortex heralds a poor prognosis in many forms of renal injury, however, the mechanism through which glomerular inflammation leads to interstitial scarring is not understood. In a model of anti-GBM disease in the rabbit, development of crescentic glomerulonephritis is associated with marked interstitial fibrosis and decreased renal function. We previously demonstrated that collagen accumulation in the model was preceded by increases in collagen I and IV mRNA and that these changes were primarily extraglomerular at early time points when inflammation was predominantly intraglomerular. In order to identify the cellular origins of extraglomerular collagen synthesis in this model, in situ hybridization using an alpha 2(I) procollagen probe was performed. EXPERIMENTAL DESIGN: A 602 bp rabbit alpha 2(I) procollagen cDNA was cloned using a PCR strategy and sequenced. The nucleotide sequence of the coding region was 94% identical with the human alpha 2(I) procollagen sequence. Northern blots were performed to define conditions of specific hybridization of the anti-sense riboprobe. Tissue sections from normal rabbit kidneys and from kidneys 4, 5, 7, 10 and 14 days after injection of anti-GBM antibody were hybridized with 35S-labeled sense and anti-sense riboprobes. Cells containing alpha 2(I) mRNA were identified by autoradiography and mRNA abundance was quantitated by grain density. RESULTS: No specific hybridization was detected with the sense probe at any time. alpha 2(I) mRNA was undetectable with the anti-sense probe in normal kidney sections. In contrast, the anti-sense probe hybridized specifically at all time points after induction of anti-GBM disease. In agreement with previous filter hybridization studies, on day 4, when inflammation was predominantly intraglomerular, cells in the periarterial adventitial compartment of renal cortex hybridized strongly. At later time points, labeling was also present in the interstitial spaces, the periglomerular region, in Bowman's space and in the glomerular tuft itself. CONCLUSIONS: We conclude that perivascular adventitial cells are among the first to respond to glomerular inflammation and represent a pool of cells that subsequently contribute to interstitial and glomerular scarring.