Cellular composition of crescents in human rapidly progressive glomerulonephritis identified using monoclonal antibodies

The relative contributions of glomerular epithelial cells, macrophages, and other cell types to the formation of cellular crescents characteristic of human rapidly progressive glomerulonephritis remain controversial. To identify and quantitate the cell types present during different stages of glomerular crescent formation, immunoperoxidase labelling of cryostat sections from renal biopsies with cellular (n = 9) or sclerosed (n = 3) crescents was performed using monoclonal antibodies to cell-specific antigens of leucocytes, epithelial cells, and other glomerular cell types. Fresh cellular crescents consisted of macrophages (34.5 +/- 7.0%; mean +/- SEM) plus lesser proportions of polymorphs (12.8 +/- 4.7%) and epithelial cells (10.4 +/- 1.5%). Sclerosed crescents contained fewer macrophages (5.1 +/- 1.0%), but similar proportions of polymorphs (11.1 +/- 2.9%) and epithelial cells (11.5 +/- 2.1%). Lymphocytes were not detected within crescents. Many of the remaining unlabelled cells morphologically resembled fibroblasts and expressed surface fibronectin, though fibroblast-specific cell markers were not available. These results show that macrophages and not epithelial cells constitute the major cell type within cellular crescents. Therapeutic manoeuvres directed against macrophages may, therefore, be of clinical value in the management of human crescentic rapidly progressive glomerulonephritis.     

Activated (IL-2R+) intraglomerular mononuclear cells in crescentic glomerulonephritis

We recently reported evidence for the involvement of local cellular immune activation in the immunopathogenesis of human IgA nephropathy, particularly in cases of IgA disease featuring crescent formation. In the current study, using monoclonal antibodies, we investigated whether mononuclear cells bearing receptors for interleukin 2 (IL-2R+ MNC) were present within glomeruli or associated crescents in biopsies from patients with crescentic glomerulonephritis (greater than 60% crescents, N = 19), IgA disease with crescents (N = 9), or other types of proliferative glomerulonephritis with crescents (10 to 44%, N = 6), compared with normal control kidneys (N = 10). Biopsies were further classified into those showing active (cells, fibrin) (N = 15) or inactive (sclerosed) crescents (N = 19), to determine whether IL-2R+ MNC were particularly associated with active crescent formation. Few leucocytes were found within glomerular tufts of normal kidneys (2.4 +/- 0.7 cells/glomerular cross-section; mean +/- SEM). By contrast, in biopsies from patients with active crescentic glomerulonephritis, total intraglomerular tuft leucocytes were increased to 14.0 +/- 1.7 (P less than 0.01 vs. normal kidneys), largely due to increased numbers of intraglomerular monocytes (10.4 +/- 1.1, P less than 0.01) and T cells (3.7 +/- 0.6, P less than 0.01). Biopsies with active crescents also contained significantly increased numbers of intraglomerular tuft IL-2R+ MNC (4.0 +/- 0.7, 29% of total intraglomerular leucocytes), and there was a strong correlation between the numbers of intraglomerular IL-2R+ MNC and T cells (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Scanning electron microscopy of acellular glomeruli in nephrotic syndrome

All cellular elements were extracted from portions of 13 renal biopsies performed for nephrotic syndrome and the acellular glomerular basement membrane (GBM) examined by scanning electron microscopy (SEM). Five biopsy specimens did not contain subepithelial deposits by light microscopy (LM), immunofluorescence (IF), and transmission electron microscopy (TEM). SEM of the acellular GBM showed a uniform slightly granular surface identical to that previously reported for normal human GBM. Eight biopsy specimens contained subepithelial deposits by LM, IF, and TEM. SEM showed complete extraction of deposits and a spectrum of clearly visualized diffuse GBM alterations in response to subepithelial deposits. Shallow pits or indentations of the GBM were noted in two cases stage I MGN which correlated with numerous "pinholes" visualized by LM in tangential sections of the GBM on silver stain. A complex reticular pattern of GBM elaboration was observed in cases of stage II MGN corresponding to "spikes" visualized by LM on silver stain. SEM of glomeruli following cell extraction permits the first direct three-dimensional visualization of the GBM alterations occurring in various stages of subepithelial immune complex formation.     

Glomerular epithelial-myofibroblast transdifferentiation in the evolution of glomerular crescent formation.

BACKGROUND:Glomerular cellular crescents consist of epithelial cells and macrophages, which can undergo an irreversible process of fibrous organization. However, the origin of the fibroblast-type cells that mediate this fibrous organization is unclear. METHODS: This study examined glomerular epithelial- myofibroblast transdifferentiation (GEMT) in the formation and evolution of glomerular crescents in two distinct rat models of glomerulonephritis: 5/6 nephrectomy and antiglomerular basement membrane (GBM) disease. RESULTS: Early in the course of both disease models, and prior to crescent formation, immunohistochemistry staining and in-situ hybridization demonstrated de novo expression of alpha-smooth-muscle actin (alpha-SMA), a marker of smooth muscle cells and myofibroblasts, by glomerular parietal epithelial cells (GPEC). The expression of alpha-SMA by GPEC was accompanied by a loss of E-cadherin staining, a marker of epithelial cells. At this early stage of GEMT, ultrastructural studies identified the presence of characteristic actin microfilaments and dense bodies within GPEC which retained a normal epithelial morphology with apical-basal polarity and microvilli. A late stage of transdifferentiation was seen in fibrocellular crescents. In this case, GPEC attached to intact segments of the capsular basement membrane contained large bundles of actin microfilaments throughout the cell, and this was accompanied by a loss of polarity, microvilli, and tight junctions. There was a significant correlation between the presence of alpha-SMA(+) GPEC and glomerular crescent formation. Cellular crescents contained small numbers of alpha-SMA(+) myofibroblasts. These cells become the dominant population in fibrocellular crescents, which was associated with marked local proliferation. Relatively few alpha-SMA(+) myofibroblasts remained in fibrotic/organizing crescents. Most cells within cellular and fibrocellular crescents expressed transforming growth factor-beta (TGF-beta) and basic fibroblast growth factor (FGF-2), suggesting that these growth factors may regulate this GEMT process during the evolution of glomerular crescents. CONCLUSIONS: This study provides the first phenotypic and morphological evidence that glomerular epithelial-myofibroblast transdifferentiation participates in the formation and evolution of glomerular crescents.     

Three-dimensional architecture of the mesangial matrix--comparison of the intact and acellular glomerulus

The three-dimensional ultrastructure of the rat mesangial matrix was studied in acellular rat renal cortex in comparison with intact cortex by scanning electron microscopy (SEM). The mesangial region was covered with fenestrated endothelial cells and was not identified in untreated specimens by SEM. Acellular renal cortex was obtained by perfusion with 4 mM EDTA, 3% Triton X-100, 0.0025% deoxyribonuclease in 1 M NaCl and 4% sodium deoxycholate. Transmission electron microscopy revealed that the glomerular basement membrane (GBM) and mesangial matrix maintained their respective shape and did not collapse even after removal of the cellular components. By SEM, the mesangial matrix appeared as fenestrated septa with oval or round stomata between the glomerular capillaries. The diameter of the stomata was 601 +/- 290 nm. The diameter of the fibrils forming the stomata was 177 +/- 80 nm. These fenestrated structures of the mesangial matrix appear to be useful in supporting glomerular tufts, in stretching and retracting mesangial cells and in passing macromolecules from the capillary lumen into the mesangium.     

Podocytes contribute to the formation of glomerular crescents

The cellular composition of crescents in glomerular disease is controversial. The role of podocytes in crescent formation has been especially difficult to study because podocytes typically lose their characteristic terminally differentiated phenotype under disease conditions, making them difficult to identify. We reasoned that the intermediate filament protein nestin, a marker of progenitor cells that has recently been identified in podocytes, may allow the investigation of podocyte involvement in glomerular crescents. In a series of 35 biopsies with crescentic glomerular disease, all showed nestin-positive cells in the crescents, ranging in number from occasional to approximately 50% of crescent cells. Other podocyte markers, such as podocin and WT1, failed to identify cells in crescents, and no contribution by endothelial or myogenic cells was noted. CD68-positive cells were observed in 80% of cases but were never as numerous as the nestin-positive cells. Nestin and CD68 were not coexpressed by the same cells, providing no evidence of trans-differentiation of podocytes into a macrophage phenotype. Keratin-positive cells were found in crescents in 51% of cases, but only as occasional cells. Up to one third of crescent cells were cycling in 48% of biopsies, and double immunostaining identified these cells as a mixture of nestin-positive cells and "null" cells (negative for nestin, CD68, and keratin). In addition to our observations in human disease, we also identified nestin-positive proliferating podocytes in the crescents of 2 mouse models of crescentic glomerulonephritis. We conclude that podocytes play a role in the formation of glomerular crescents.     

An electron microscopic study of the glomerular alterations of pure-preeclampsia]

Ultrastructural glomerular lesions of preeclampsia were studied by electron microscopy in 39 biopsy specimens from 36 patients. Postpartum biopsy obtained on day 0 revealed marked narrowing of the capillary lumen due to endothelial cell swelling, massive subendothelial and mesangial deposits containing lipids and fibrillar fibrins, monocyte invasion in the mesangium, and rupture and duplication of the glomerular capillary wall. Duplication of the glomerular capillary wall generally consisted of the glomerular basement membrane (GBM) and a newly formed mesangial matrix associated with mesangial interposition. However, it was occasionally seen as the GBM and a newly formed basement membrane-like material attached to the GBM side of the endothelial cell membrane without interposing mesangial cells. Podocytes contained many protein resorption droplets in which albumin, immunoglobulins, complements and fibrinogen were observed by immunoelectron microscopy. The massive mesangial and subendothelial deposits were reduced in volume 2 weeks after delivery, and endothelial swelling decreased 3 weeks after delivery. Widening of the subendothelial space of the GBM was still apparent 5 weeks after delivery, although no deposits were observed. By 8 weeks, this widening was not evident. Foam cells and an increase in the mesangial matrix were noted 2-6 weeks and 5-8 weeks after delivery, respectively. Focal glomerular sclerosis lesions were detected in 17 cases. This lesion may have resulted from massive subendothelial and mesangial deposits, rupture of the GBM or epithelial detachment.     

Expression of basic fibroblast growth factor and its receptor in the progression of rat crescentic glomerulonephritis

Summary: The aim of this study was to examine the relationship of basic fibroblast growth factor (FGF-2) and its receptor (FGF-R) to tubular proliferation, interstitial fibrosis, glomerular cell proliferation and crescent formation in the development of anti glomerular basement membrane (GBM) glomerulonephrids in the rat. Using new microwave-based histochemistry techniques, weak constitutive expression of mRNA and protein for FGF-2 and FGF-R was evident in tubules and glomeruli of normal rat kidney. Double and triple staining with the proliferating cell nuclear antigen (PCNA) demonstrated that in disease there was focal up-regulation of FGF-2 and FGF-R mRNA and protein expression within proliferating tubules and fibroblast-like cells in areas of interstitial fibrosis. In contrast, tubules in non-inflamed areas of kidney showed no change in FGF-2 and FGF-R expression or cellular proliferation. In addition, many FGF-2⁺PCNA⁺ and FGF-R⁺PCNA⁺ cells, probably mesangial cells and podocytes, were evident within glomerular segmental proliferative lesions. of particular interest was the observation that many epithelial cells within cellular crescents, inculding proliferating (PCNA⁺) epithelial cells, strongly expressed both FGF-2 and FGF-R. Furthermore, there was strong FGF-2 and FGF-R expression by proliferating fibroblast-like cells within fibrocellular crescents suggesting that FGF-2 is involved in the formation and fibrotic progression of glomerular crescents. In conclusion, this study provides evidence that increased expression of FGF-2 and its receptor may participate in the proliferative/fibrotic response in progressive crescentic glomerulonephritis.     

Immunopathology, extent and course of glomerulonephritis with crescent formation

Ten out of 66 cases of glomerulonephritis (GN) with variable crescent formation appeared to be of post-streptococcal origin. Immunofluorescent studies of biopsies from 42 of the patients showed findings suggestive of immune complex glomerular injury in 86% whilst there was no evidence of immunologic or nonimmunologic injury in the remainder. Anti-GBM GN was not demonstrable, although it can not be certain that there were no cases amongst the patients whose biopsies were not examined by immunofluorescence. Conservative measures were adequate for the treatment of cases with less than 50% crescents. In the others, with greater than or equal to 50% crescents, appreciable improvement was observed with anticoagulation, immunosuppression and dialysis. The mortality was 30% in cases with 50-80% and 65% in cases with greater than 80% crescents. No appreciable difference in survival was observed between post-streptococcal and idiopathic cases. The single most important factor in prognosis, regardless of etiology, appeared to be the extent of crescent formation. Tubulo-interstitial damage was contributory. Necrotizing angiitis, present in 4 cases, affected the course adversely.     

Histological differences in new-onset IgA nephropathy between children and adults.

BACKGROUND: It is suggested that IgA nephropathy (IgAN) manifests differently in children vs adults on the basis of biopsy findings. However, this has been difficult to establish owing to the uncertainty of the timing of disease onset in adult IgAN. We addressed this question by comparing both histology and leucocyte accumulation in biopsies of recently diagnosed childhood and adult IgAN. METHODS: Biopsies taken within 2 years from the onset of renal abnormalities in 33 childhood (10 +/- 3 years of age) and 38 adult (35 +/- 6 years) cases of IgAN were examined for histological changes (cellularity in mesangial, endocapillary and extracapillary areas, matrix expansion, adhesions/crescents and interstitial damage), glomerular deposition of immunoglobulin and complement, and the presence of macrophages, activated macrophages and T cells by immunohistochemistry. RESULTS: Glomerular hypercellularity owing to increased cells in mesangial area was prominent in paediatric IgAN and significantly greater than in adult IgAN. In contrast, glomerular matrix expansion, crescent formation and interstitial damage were more severe in adults compared to paediatric IgAN. Indeed, glomerular hypercellularity correlated with proteinuria in paediatric but not in adult IgAN, whereas glomerular matrix correlated with proteinuria and renal function in adult but not in paediatric IgAN. The degree of C3c deposition was significantly greater in paediatric IgAN, while deposition of fibrinogen was greater in adult IgAN. Glomerular and interstitial CD68+ macrophages and a subset of sialoadhesin (Sn)+ activated macrophages were identified in both paediatric and adult IgAN, being significantly greater in number in adult IgAN. Glomerular leucocyte infiltration correlated with proteinuria while interstitial leucocyte infiltration correlated with interstitial damage in both groups. However, only the subset of Sn+ macrophages gave a significant correlation with renal function, glomerular hypercellularity and glomerular matrix. CONCLUSIONS: This study has demonstrated significant differences in the early glomerular lesions of IgAN in children vs adults. Furthermore, Sn+ activated macrophages are implicated in the pathogenesis of IgAN in both patient groups. The prognostic significance of these findings warrants further study.     

The role of platelet‐derived growth factor in a murine model of crescentic nephritis

SUMMARY Platelet‐derived growth factor (PDGF) is a major mesenchymal cell mitogen, with an established role in the pathogenesis of experimental mesangial proliferative nephritis. The role of PDGF in experimental models of crescentic glomerulonephritis is not well defined. To study the role of PDGF in glomerular crescent formation, we induced a model of crescentic glomerulonephritis in transgenic mice expressing high concentrations of the soluble external domain of the PDGFβ receptor (PDGF‐Rβ). Crescentic nephritis was induced by the intraperitoneal injection of antibody to whole rabbit glomeruli. At day 7 of disease, biopsies of transgenic and wild‐type mice were evaluated for crescent frequency, crescent area, and thickness of crescent cell layer. In situ hybridization was performed to evaluate the expression of both PDGF B‐chain and PDGFRβ mRNA within crescents. Delivery of soluble receptor to the urinary space was evaluated by Western blotting. Crescent frequency did not differ between wild type and transgenic mice. However, crescent area quantified by computer image analysis was significantly reduced in transgenic mice (P < 0.015). Transgenic biopsies displayed predominantly crescents composed of two cell layers (P = 0.03 compared with wild type), whereas wild‐type biopsies had significantly more crescents composed of four or more cell layers (P = 0.04). Both PDGF B‐chain and PDGF‐Rβ mRNA were detected within crescents in a heterogeneous fashion. Soluble receptor was detectable in the urine of all transgenic diseased mice. We conclude that PDGF plays a role in modulating crescent size and development in our murine model of crescentic nephritis.     

Treatment of severe IgA nephropathy in children

We treated ten children with severe IgA nephropathy (IgAN) [proteinuria > 1g/day, hypertension, renal insufficiency, segmental sclerosis, crescent formation and/or glomerular basement membrane (GBM) deposition of IgA] with prednisone and azathioprine for 1 year. Following the year of therapy, seven of the ten children underwent a repeat kidney biopsy. All biopsies were scored for activity (percentage of glomeruli demonstrating crescent formation, degree of mesangial proliferation and interstitial infiltrate; maximum score = 9) and chronicity (percentage of glomeruli demonstrating fibrous crescents, segmental sclerosis, global sclerosis, and degree of tubular atrophy and interstitial fibrosis; maximum score = 12). After 1 year of therapy, the protein excretion of all the children decreased significantly (P<0.01) from 4052±3190 mg/day to 1692±1634 mg/day. The activity score decreased significantly (P<0.01) from 4.35±0.94 prior to therapy to 2.28±0.75 after therapy while the chronicity score was unchanged (5.42±1.7 vs 5.85±2.0). The percentage of glomeruli demonstrating cellular crescents decreased (P<0.05) from 21.2±21.7% prior to therapy to 0.94±2.4% after therapy. Mesangial deposition of IgA persisted but GBM deposition of IgA was less prominent after therapy. During the follow-up period (mean 2.6 years, range 9 months–7.5 years), one child required brief retreatment for biopsy-confirmed recurrence of active disease, two children have developed renal insufficiency due to progressive scarring in the absence of inflammation, while the remaining seven are stable. We suggest that treatment with prednisone and azathioprine may be beneficial in children with severe IgAN and that a controlled clinical trial is warranted.     

IgA肾病伴部分性新月体形成的临床病理分析

目的：探讨原发性IgA肾病伴部分性新月体形成的临床和病理特点。方法：选取79例经肾活检确诊伴部分性新月体形成IgA肾病患者,分析其临床和病理特点,并根据新月体形成所累及肾小球的比例分组：≥10%为A组,31例;≤10%为B组,48例。结果：（1）临床表现：79例均有血尿＋蛋白尿,蛋白尿〉1g/24h者48例（60.8%）;两组比较,A组蛋白尿〉1g/24h28例（89.3%）,B组蛋白尿〉1g/24h20例（41.7%）,A组大量蛋白尿、肉眼血尿、高血压、肾衰竭发生率均高于B组（P〈0.05）。（2）病理表现：79例新月体形成累及肾小球3.3%～29.0%,均以细胞性为主,几乎均有肾小球硬化、内皮细胞及系膜细胞增生、球囊黏连、灶性肾小管萎缩、以及炎性细胞浸润;两组比较A组中、重度系膜细胞及内皮细胞增生、炎性细胞浸润,细胞新月体所占比例均较B组明显;病理改变硬化肾小球占55例（69.6%）。结论：IgA肾病伴部分性新月体形成患者临床均有血尿＋蛋白尿,尤其大量蛋白尿;病理改变以局灶节段性肾小球硬化常见;炎性细胞浸润、内皮细胞及系膜细胞增生等活动性病变易见并影响新月体形成;新月体的多少及纤维化程度影响临床病理表现,≥10%较≤10%严重。     

ANCA-negative pauci-immune renal vasculitis: histology and outcome.

BACKGROUND: Pauci-immune renal vasculitis with focal glomerular necrosis and crescent formation is usually associated with anti-neutrophil cytoplasmic antibodies (ANCAs). However, ANCA's are absent in up to 10% of cases, which constitutes a rarely studied variant of renal vasculitis. METHODS: This retrospective multicentre cohort study analyzed the presenting features, renal histology and outcome in 20 patients with pauci-immune crescentic necrotizing renal vasculitis in whom indirect immunofluorescence did not detect ANCA. RESULTS: Renal histology revealed a high percentage of active glomerular lesions (50%), mainly cellular crescents, 28% of them with glomerular necrosis. Chronic tissue damage with glomerulosclerosis (21%) and diffuse interstitial fibrosis (40%) was already present at diagnosis, more prominent than in historical PR3-positive patients. Infiltrates of polymorphonuclear neutrophils in glomerular capillary loops were observed in 40% of all biopsies, mainly in necrotic lesions. The subsets of interstitially infiltrating leukocytes similar to ANCA-associated disease. Microscopic polyangiitis was diagnosed in 17 patients, Wegener's granulomatosis in two and renal-limited vasculitis in one. The patients median disease extent index (DEI) of 5 (range 4-11) reflected a systemic vasculitis. ANCA-negative vasculitis was not associated with infection or malignancy. Renal outcome was correlated to DEI (P = 0.032) and serum creatinine at diagnosis (P = 0.04). The mortality rate was high (35%) and closely related to age above 65 years at diagnosis (P = 0.014). Conclusions. The histological findings and prognosis in ANCA-negative renal vasculitis are comparable with those of ANCA-positive disease. Our data underline the importance of the exact diagnosis in an active vasculitic disease process even in the absence of ANCAs.     

How glomerular extracapillary proliferation might lead to loss of renal function: light microscopic and immunohistochemical investigation

Although there has been extensive research into the mechanisms involved in glomerular crescent formation, it is not yet fully understood how this change may cause renal function impairment. The aim of this study is to identify morphologic changes which may be responsible for this phenomenon. Thirty-eight renal biopsies showing glomerulonephritis with extracapillary proliferation (20 vasculitis-related, 6 idiopathic, 9 due to immune-complex deposition and 3 superimposed on diabetic nephropathy) were considered, and 146 glomeruli in which both crescents and the urinary pole were found at the same time, were studied. The involvement of the urinary pole by cellular crescents was observed in 93.1 and 100% of the glomeruli with segmental or circumferential crescents, respectively. A tridimensional study, for the evaluation of the glomeruli as a whole, was performed on 8 biopsies by means of the step-section technique and disclosed the involvement of the urinary space and a close contact between crescent and tubular cells in all 54 investigated glomeruli. The reported features do not seem to be related to the type of cells which formed the crescent. Indeed, as shown by immunohistochemical study on 10 cases with anti-cytokeratin and anti-CD68 antisera, the crescent localization at the urinary pole had no correlation with the prevalence of epithelial or macrophagic cells. These findings suggest that crescents, due to epithelial proliferation or macrophage clustering, tend to localize at the urinary pole and thus come into close contact with cells of the proximal convoluted tubule: the formation of a sort of plug or a 'glomerular stone' could well explain the block in the urine flow and the consequent impairment of renal function in the acute phase of the disease, even in those cases where crescents are segmental.     

A histopathological study on the prognosis of childhood IgA nephropathy and glomerular basement membrane lesions

Seventy-three patients with IgA nephropathy (IgAGN), under the age of 15 years at the time of the discovery of the disease, were investigated with respect to glomerular basement membrane (GBM) lesions. Irregular attenuation or widening of GBM, especially on the epithelial side, was observed in 28 cases (38%). These two changes are referred to aslysis of GBM and were considered to be the primary and specific changes among the GBM lesions in IgAGN. GBM thickening with layering of lamina densa was found in 37 of 73 cases (51%), but this change has been observed in other types of glomerular diseases. GBM lesions similar to those seen in IgAGN were also observed in Henoch-Schönlein purpura nephritis (HSPN) and poststreptococcal acute glomerulonephritis (PSAGN). Lysis of GBM was observed only in IgAGN, HSPN and PSAGN. Subepithelial and intramembranous deposits appeared to have an important role in the development of these GBM lesions. The presence of GBM lesions was correlated with a high incidence of cellular crescents but not with other clinical or light microscopic findings. The presence of these GBM lesions in IgAGN does not have a significant effect on the prognosis, at least in childhood. The affected GBM seemed to recover without leaving any significant residual damage in most cases. In the long-term prognosis of the disease non-immunological factors, such as ageing or hypertension, seem to be important.     

Osteopontin expression in human crescentic glomerulonephritis

Osteopontin expression in human crescentic glomerulonephritis. BACKGROUND: Osteopontin is a molecule with diverse biological functions, including cell adhesion, migration, and signaling. The expression of osteopontin has been demonstrated in a number of models of renal injury in association with accumulations of monocyte/macrophages, including recent reports of osteopontin expression in glomerular crescents in a rat model of anti-glomerular basement membrane glomerulonephritis. METHODS: Glomerular expression of osteopontin in biopsies of human crescentic glomerulonephritis (N = 25), IgA nephropathy with crescents (N = 2), and diffuse proliferative lupus glomerulonephropathy with crescents (N = 1) was studied by immunohistochemistry, in situ hybridization, and combined immunohistochemistry/in situ hybridization. Additionally, antibodies to cell-specific phenotypic markers were used to identify cellular components of the glomerular crescent, which express osteopontin protein and mRNA. RESULTS: All of the crescents present in the biopsies studied contained a significant number of cells that expressed osteopontin protein and mRNA, demonstrated by immunohistochemistry and in situ hybridization, respectively. Using replicate tissue sections and combined immunohistochemistry/in situ hybridization, we showed that the majority of the strongly osteopontin-positive cells are monocyte/macrophages. In addition to the very strong and cell-associated localization, a weaker and more diffuse pattern of osteopontin protein and mRNA expression could be seen in a number of crescents. None of the osteopontin mRNA-expressing cells could be identified as parietal epithelial cells, CD3-positive T cells, or alpha-smooth muscle actin-positive myofibroblasts. Interstitial monocyte/macrophages did not express osteopontin, except when located in a periglomerular inflammatory infiltrate. CONCLUSIONS: Macrophages present in the human glomerular crescent express osteopontin protein and mRNA at a high level. This expression supports a role for osteopontin in the formation and progression of the crescentic lesion via chemotactic and signaling properties of the molecule.     

Transforming growth factor-{beta}, endothelin-1, and c-fos expression in necrotizing/crescentic IgA glomerulonephritis

Background: Among our cases of IgA glomerulonephritis (IgAGN), 10% show necrotizing/extracapillary lesions involving a small percentage of glomeruli and associated with a ceratin degree of inflammation in absence of glomerular and interstitial scarring. In our experience, also in repeat biopsies, these cases of IgAGN have a worse prognosis probably because necrotizing/extracapillary lesions can repeat and accumulate, leading to the progression of damage. As it is well known that transforming growth factor-{beta} (TGF-{beta}) and endothelin-1 (ET-1) are key-factors in the progression of glomerulonephritis, aim of the study was to examine their expression in renal biopsies of primary IgAGN with necrotizing/crescentic lesions in complete absence of interstitial fibrosis. To obtain information about the mitogenic effect of ET-1, the expression of c-fos, whose upregulation by ET-1 has been established in culture, was also studied. Methods: Eighteen renal biopsies of patients with necrotizing/crescentic IgAGN were examined by immunohistochemistry with antibodies against TGF-{beta}, ET-1 and c-fos. The results were compared with those obtained on 22 cases of IgAGN characterized only by pure mesangial proliferation and 25 IgAGN biopsies with advanced, not active, glomerulointerstitial lesions. Results: In necrotizing/crescentic IgAGN glomerular TGF-{beta} appeared more positive than in cases characterized only by pure mesangial proliferation and was especially expressed on cellular crescents. In the interstitium, TGF-{beta}, ET-1 and c-fos were expressed by infiltrating leukocytes, tubules, and small vessels. This positivity, although similar as localization, was less diffuse than in biopsies with advanced interstitial damage, but significantly greater than in cases with pure mesangial proliferation. Conclusions: Positivity of TGF-{beta} on cellular crescents is similar to that observed from other authors in different types of necrotizing/crescentic human glomerulonephritis and supports our hypothesis that this is a peculiar type of IgAGN. Moreover, interstitial expression of TGF-{beta}, ET-1 and c-fos in biopsies with glomerular active lesions but complete absence of interstitial fibrosis may potentially represent a signal of activation of mechanisms that induce and amplify the damage leading to further progression of the disease. Key words: c-fos; ET-1; immunohistochemistry; necrotizing/crescentic IgAGN; TGF-{beta}      

Active and chronic phases of Berger's disease (IgA nephropathy)

Berger's disease, or IgA nephropathy, is generally considered as pursuing a chronic course, often with recurrent attacks of gross hematuria or persistent microscopic hematuria. However, little attention has been paid to the acute changes that may accompany this nephropathy, and there are few reports of follow-up renal biopsy studies in these patients. We have had the opportunity to study two patients with Berger's disease (IgA nephropathy) in whom initial and follow-up renal biopsy studies were available. Both of these patients presented clinically with gross hematuria and moderately heavy proteinuria. In both cases, the initial renal biopsy disclosed diffuse mesangial proliferation associated with crescent formation, while follow-up biopsy disclosed only mild mesangial proliferation and no crescents. In one case electron microscopy revealed prominent subendothelial and small mesangial deposits in the initial biopsy, which became almost solely large mesangial in the second biopsy. The other case demonstrated only mesangial deposits in both biopsies.     

Proteinase-3 mRNA expressed by glomerular epithelial cells correlates with crescent formation in Wegener's granulomatosis

BACKGROUND: Wegener's granulomatosis (WG) is characterized by systemic vasculitis with crescentic glomerulonephritis (CGN) and circulating autoantibodies directed against neutrophil cytoplasmic antigens (ANCA). Proteinase 3 (PR-3), a neutral serine proteinase in neutrophils implicated in the growth control of myeloid cells, has been identified as the target antigen for ANCA in WG. Since the kidneys are frequently involved in WG, we studied the in situ expression of PR-3 by renal parenchymal cells. METHODS: We assessed the expression of PR-3 in kidney biopsies of 15 patients with WG by immunohistochemistry (IHC) and in situ hybridization (ISH). Normal kidney tissue served as the control. RESULTS: We detected PR-3 mRNA and PR-3 protein in distal tubular epithelial cells (TECs) and glomerular epithelial cells (GECs) in normal kidney tissue and in CGN. Furthermore, a strong glomerular PR-3mRNA expression restricted to the site of cellular crescents was detected in patients with WG. The analysis of 144 glomeruli with cellular or sclerotic crescents revealed a positive correlation of glomerular PR-3mRNA expression with the percentage of cellular crescents per glomerulus. The capability of human TECs and GECs to synthesize PR-3 was confirmed by Northern blot and ISH on cultured cells. CONCLUSION: These data provide evidence that nonhematopoetic renal parenchymal cells express PR-3 and that glomerular expression of PR-3 is associated with crescent formation in WG. Our findings suggest that renal parenchymal cells may directly be involved in the pathogenesis of CGN in WG.